Research

13 pages, 687 KiB

Open AccessArticle

Molecular Detection of Integrons, Colistin and β-lactamase Resistant Genes in Salmonella enterica Serovars Enteritidis and Typhimurium Isolated from Chickens and Rats Inhabiting Poultry Farms

by Tsepo Ramatla, Kealeboga Mileng, Rendani Ndou, Nthabiseng Mphuti, Michelo Syakalima, Kgaugelo E. Lekota and Oriel M.M. Thekisoe

Microorganisms 2022, 10(2), 313; https://doi.org/10.3390/microorganisms10020313 - 28 Jan 2022

Cited by 15 | Viewed by 2703

Abstract

The rapid growth of multidrug-resistant Salmonella is a global public health concern. The aim of this study was to detect integrons, colistin and β-lactamase resistance genes in Salmonella enteritidis and typhimurium. A total of 63 isolates of S. enteritidis (n = [...] Read more.

The rapid growth of multidrug-resistant Salmonella is a global public health concern. The aim of this study was to detect integrons, colistin and β-lactamase resistance genes in Salmonella enteritidis and typhimurium. A total of 63 isolates of S. enteritidis (n = 18) and S. typhimurium (n = 45) from fecal samples of layers and rats at chicken farms were screened for antibiotic resistant genes. Conventional PCR was performed for the detection of integrons (classes 1, 2, and 3), colistin (mcr-1-5) and β-lactamase (bla_CTX-M, bla_CTX-M-1, bla_CTX-M-2, bla_CTX-M-9, bla_CTX-M_-15, bla_TEM, bla_SHV, and bla_OXA) resistant genes. Of these isolates, 77% and 27% of S. typhimurium and S. enteritidis harboured the mcr-4 encoded gene for colistin, respectively. The prevalence of class 1 integrons for S. typhimurium and S. enteritidis was 100% for each serovar, while for class 2 integrons of S. typhimurium and S. enteritidis it was 49% and 33% respectively, while class 3 integron genes was not detected. Our study also detected high levels of β-lactamase encoding genes (bla gene), namely bla_CTX-M, bla_CTX-M-1, bla_CTX-M_-9 and bla_TEM from both S. typhimurium and S. enteritidis. This, to our knowledge, is the first report of mcr-4 resistance gene detection in Salmonella serovars in South Africa. This study also highlights the importance of controlling rats at poultry farms in order to reduce the risk of transmission of antibiotic resistance to chickens and eventually to humans. Full article

(This article belongs to the Special Issue Salmonella and Salmonellosis)

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12 pages, 852 KiB

Open AccessArticle

Development and Evaluation of Alternative Methods to Identify the Three Most Common Serotypes of Salmonella enterica Causing Clinical Infections in Kazakhstan

by Sabyrkhan M. Barmak, Yuriy A. Sinyavskiy, Aidar B. Berdygaliev, Turegeldy Sh. Sharmanov, Irina S. Savitskaya, Gulmira T. Sultankulova and Elena V. Zholdybayeva

Microorganisms 2021, 9(11), 2319; https://doi.org/10.3390/microorganisms9112319 - 09 Nov 2021

Cited by 2 | Viewed by 1725

Abstract

In this study, we aimed to compare the performance of conventional PCR and real-time PCR assays as screening methods for identification of three frequent, clinically significant Salmonella serovars in Kazakhstan. We determined the diagnostic efficacy of three molecular methods for detection of S. [...] Read more.

In this study, we aimed to compare the performance of conventional PCR and real-time PCR assays as screening methods for identification of three frequent, clinically significant Salmonella serovars in Kazakhstan. We determined the diagnostic efficacy of three molecular methods for detection of S. enterica subsp. enterica and typing S. Typhimurium, S. Enteritidis, and S. Virchow. A total of 137 clinical samples and 883 food samples were obtained in Almaty in 2018–2019. All tests showed high analytical specificity for detecting S. enterica and its corresponding serovariants (100%). The sensitivity of real-time PCR for each of the tested targets was 1–10 microbial cells and in conventional PCR 10–100 microbial cells. The trials with conventional PCR and real-time PCR had a diagnostic efficacy (DE) of 100% and 99.71%, respectively. The DE of real-time PCR and conventional PCR for detecting S. Enteritidis and S. Typhimurium was 99.90%, while the DE of conventional PCR and real-time PCR for detecting S. Virchow was 99.31% and 99.80%, respectively. The RAPD-PCR analysis of the genomic DNA of Salmonella enterica showed the genetic kinship of S. Enteritidis isolates, and the genetic heterogeneity of S. Typhimurium and S. Virchow isolates. Thus, the developed methods can be considered as alternatives to classical serotyping using antisera. Full article

(This article belongs to the Special Issue Salmonella and Salmonellosis)

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16 pages, 7245 KiB

Open AccessArticle

Qualitative Evaluation of Causes for Routine Salmonella Monitoring False-Positive Test Results in Dutch Poultry Breeding Flocks

by Eduardo Costa, Armin Elbers, Miriam Koene, Andre Steentjes, Henk Wisselink, Peter Wijnen and Jose Gonzales

Microorganisms 2021, 9(11), 2215; https://doi.org/10.3390/microorganisms9112215 - 25 Oct 2021

Viewed by 2795

Abstract

The Salmonella monitoring program, as outlined in the EU Commission regulation 200/2010, asks for repeated sampling in order to ascertain progress in achievement of the EU target. According to Article 2.2.2.2.c of this regulation, the competent authority may decide to do a resample [...] Read more.

The Salmonella monitoring program, as outlined in the EU Commission regulation 200/2010, asks for repeated sampling in order to ascertain progress in achievement of the EU target. According to Article 2.2.2.2.c of this regulation, the competent authority may decide to do a resample and retest when it has reasons to question the results of initial testing. In the Netherlands, the competent authorities have been resampling and retesting all initial positive samplings for several years because of doubts about false positive initial test results. An analysis of population data in the period 2015–2019 indicates that 48% of initial samplings at the farm were classified as false positive after resampling and retesting by the competent authorities. A qualitative analysis, assessing factors that could be associated with the occurrence of false positives, indicates that cross-contamination during the sampling process by the poultry farmer is probably the most likely source. Cross-contamination of samples during transport from the farm to the laboratory and/or cross-contamination at the laboratory are also considered possible sources. Given the slightly non-optimal system-specificity of the Salmonella monitoring program, there is good reason to make, or consider, standard resampling and retesting of initial positive results by the competent veterinary authorities possible within the EU. Full article

(This article belongs to the Special Issue Salmonella and Salmonellosis)

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10 pages, 671 KiB

Open AccessArticle

Evaluation of Sodium Bisulfate on Reducing Salmonella Heidelberg Biofilm and Colonization in Broiler Crops and Ceca

by Megan Rose Pineda, James Allen Byrd, Kenneth James Genovese, Yuhua Zhang Farnell, Dan Zhao, Xi Wang, Allison Claire Milby and Morgan Brian Farnell

Microorganisms 2021, 9(10), 2047; https://doi.org/10.3390/microorganisms9102047 - 28 Sep 2021

Cited by 3 | Viewed by 2283

Abstract

Salmonella Heidelberg (SH) on contaminated poultry causes economic and health risks to producers and consumers. We hypothesized that sodium bisulfate (SBS) would decrease SH biofilm on polyvinyl chloride (PVC) coupons and decrease the horizontal transfer of SH in broilers. Experiment 1: Salmonella Heidelberg [...] Read more.

Salmonella Heidelberg (SH) on contaminated poultry causes economic and health risks to producers and consumers. We hypothesized that sodium bisulfate (SBS) would decrease SH biofilm on polyvinyl chloride (PVC) coupons and decrease the horizontal transfer of SH in broilers. Experiment 1: Salmonella Heidelberg biofilm was cultured with PVC coupons, which were treated with SBS at a pH of 3.5 for 10 min, 8 h, and 24 h. Experiment 2: Nine replicate pens per treatment were divided between two rooms. A seeder contact model was used to mimic a natural infection environment. Treatments consisted of tap water or sodium bisulfate in water at a pH of 3.5. Salmonella Heidelberg incidence and enumeration were measured in crops and ceca. Sodium bisulfate significantly reduced biofilm by 2.16 and 1.04 logs when treated for 8 and 24 h, respectively. Crop colonization was significantly decreased in trials 1 and 2 by 0.29 and 0.23 logs, respectively. Crop pH was significantly decreased in trial 2. Ceca colonization was significantly decreased in trial 1 by 0.39 logs. The results from the present study suggest that SBS may be administered to drinking water to decrease SH gut colonization and to reduce biofilm. Full article

(This article belongs to the Special Issue Salmonella and Salmonellosis)

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11 pages, 6041 KiB

Open AccessArticle

Comparison of Conventional Molecular and Whole-Genome Sequencing Methods for Differentiating Salmonella enterica Serovar Schwarzengrund Isolates Obtained from Food and Animal Sources

by I-Chen Li, Rayean Wu, Chung-Wen Hu, Keh-Ming Wu, Zeng-Weng Chen and Chung-Hsi Chou

Microorganisms 2021, 9(10), 2046; https://doi.org/10.3390/microorganisms9102046 - 28 Sep 2021

Cited by 4 | Viewed by 1924

Abstract

Over the last decade, Salmonella enterica serovar Schwarzengrund has become more prevalent in Asia, Europe, and the US with the simultaneous emergence of multidrug-resistant isolates. As these pathogens are responsible for many sporadic illnesses and chronic complications, as well as outbreaks over [...] Read more.

Over the last decade, Salmonella enterica serovar Schwarzengrund has become more prevalent in Asia, Europe, and the US with the simultaneous emergence of multidrug-resistant isolates. As these pathogens are responsible for many sporadic illnesses and chronic complications, as well as outbreaks over many countries, improved surveillance is urgently needed. For 20 years, pulsed-field gel electrophoresis (PFGE) has been the gold standard for determining bacterial relatedness by targeting genome-wide restriction enzyme polymorphisms. Despite its utility, recent studies have reported that PFGE results correlate poorly with that of closely related outbreak strains and clonally dominant endemic strains. Due to these concerns, alternative amplification-based molecular methods for bacterial strain typing have been developed, including clustered regular interspaced short palindromic repeats (CRISPR) and multilocus sequence typing (MLST). Furthermore, as the cost of sequencing continues to decrease, whole genome sequencing (WGS) is poised to replace other molecular strain typing methods. In this study, we assessed the discriminatory power of PFGE, CRISPR, MLST, and WGS methods to differentiate between 23 epidemiologically unrelated S. enterica serovar Schwarzengrund isolates collected over an 18-year period from distinct locations in Taiwan. The discriminatory index (DI) of each method for different isolates was calculated, resulting in values between 0 (not discriminatory) and 1 (highly discriminatory). Our results showed that WGS has the greatest resolution (DI = 0.982) compared to PFGE (DI = 0.938), CRISPR (DI = 0.906), and MLST (DI = 0.463) methods. In conclusion, the WGS typing approach was shown to be the most sensitive for S. enterica serovar Schwarzengrund fingerprinting. Full article

(This article belongs to the Special Issue Salmonella and Salmonellosis)

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8 pages, 564 KiB

Open AccessCommunication

Can Human Handling Increase the Presence of Multidrug Resistance (MDR) in Salmonella spp. Isolated from Food Sources?

by Valeria Gargano, Delia Gambino, Sergio Migliore, Maria Vitale, Sonia Sciortino, Antonella Costa and Domenico Vicari

Microorganisms 2021, 9(10), 2018; https://doi.org/10.3390/microorganisms9102018 - 23 Sep 2021

Cited by 9 | Viewed by 2069

Abstract

The spread of antibiotic resistance (AR) among zoonotic pathogens is a serious health problem, especially because in the last decade the massive use of antibiotics has favored the emergence of Multidrug Resistance (MDR) strains. Some species of the Salmonella genus are among the [...] Read more.

The spread of antibiotic resistance (AR) among zoonotic pathogens is a serious health problem, especially because in the last decade the massive use of antibiotics has favored the emergence of Multidrug Resistance (MDR) strains. Some species of the Salmonella genus are among the major causes of foodborne infections worldwide and could represent reservoirs of AR. For these reasons, the susceptibility to six antibiotic classes of 63 strains isolated from animals and food was determined to assess the presence of MDR strains. In addition, the detection of resistance genes was done for strains that resulted in MDR. A statistically significant difference was found when comparing the presence of Salmonella spp. MDR strains between strains isolated from animals and strains isolated from food. Our data seem to indicate that MDR occurs mostly in Salmonella strains isolated from food. Full article

(This article belongs to the Special Issue Salmonella and Salmonellosis)

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13 pages, 12736 KiB

Open AccessArticle

Phenotypic and Genetic Comparison of a Plant-Internalized and an Animal-Isolated Salmonella Choleraesuis Strain

by Irene Esteban-Cuesta, Mirian Labrador, Katharina Hunt, Sven Reese, Jennie Fischer, Karin Schwaiger and Manfred Gareis

Microorganisms 2021, 9(8), 1554; https://doi.org/10.3390/microorganisms9081554 - 21 Jul 2021

Cited by 1 | Viewed by 2060

Abstract

Contamination of fresh produce with human pathogens poses an important risk for consumers, especially after raw consumption. Moreover, if microorganisms are internalized, no removal by means of further hygienic measures would be possible. Human pathogenic bacteria identified in these food items are mostly [...] Read more.

Contamination of fresh produce with human pathogens poses an important risk for consumers, especially after raw consumption. Moreover, if microorganisms are internalized, no removal by means of further hygienic measures would be possible. Human pathogenic bacteria identified in these food items are mostly of human or animal origin and an adaptation to this new niche and particularly for internalization would be presumed. This study compares a plant-internalized and an animal-borne Salmonella enterica subsp. enterica serovar Choleraesuis aiming at the identification of adaptation of the plant-internalized strain to its original environment. For this purpose, a phenotypical characterization by means of growth curves under conditions resembling the indigenous environment from the plant-internalized strain and further analyses using Pulsed-field gel electrophoresis and Matrix-assisted laser desorption ionization time of flight spectrometry were assessed. Furthermore, comparative genomic analyses by means of single nucleotide polymorphisms and identification of present/absent genes were performed. Although some phenotypical and genetic differences could be found, no signs of a specific adaptation for colonization and internalization in plants could be clearly identified. This could suggest that any Salmonella strain could directly settle in this niche without any evolutionary process being necessary. Further comparative analysis including internalized strains would be necessary to assess this question. However, these kinds of strains are not easily available. Full article

(This article belongs to the Special Issue Salmonella and Salmonellosis)

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8 pages, 997 KiB

Open AccessCommunication

Feedborne Salmonella enterica Serovar Jerusalem Outbreak in Different Organic Poultry Flocks in Switzerland and Italy Linked to Soya Expeller

by Jule Anna Horlbog, Roger Stephan, Marc J. A. Stevens, Gudrun Overesch, Sonja Kittl, Maira Napoleoni, Valentina Silenzi, Magdalena Nüesch-Inderbinen and Sarah Albini

Microorganisms 2021, 9(7), 1367; https://doi.org/10.3390/microorganisms9071367 - 23 Jun 2021

Cited by 2 | Viewed by 2416

Abstract

Poultry feed is a leading source of Salmonella infection in poultry. In Switzerland, heat-treated feed is used to reduce Salmonella incursions into flocks in conventional poultry production. By contrast, organic feed is only treated with organic acids. In 2019, the Swiss National Reference [...] Read more.

Poultry feed is a leading source of Salmonella infection in poultry. In Switzerland, heat-treated feed is used to reduce Salmonella incursions into flocks in conventional poultry production. By contrast, organic feed is only treated with organic acids. In 2019, the Swiss National Reference Center for Enteropathogenic Bacteria identified the rare serovar S. Jerusalem from samples of organic soya feed. Further, in July 2020, the European Union’s Rapid Alert System for Food and Feed published a notification of the detection of S. Jerusalem in soya expeller from Italy. During 2020, seven S. Jerusalem isolates from seven different poultry productions distributed over six cantons in Switzerland were reported, providing further evidence of a possible outbreak. Using whole-genome sequencing (WGS), S. Jerusalem isolates from feed and from animals in Switzerland were further characterized and compared to S. Jerusalem from organic poultry farm environments in Italy. WGS results showed that feed isolates and isolates from Swiss and Italian poultry flocks belonged to the sequence type (ST)1028, grouped in a very tight cluster, and were closely related. This outbreak highlights the risk of spreading Salmonella by feed and emphasizes the need for a heat-treatment process for feed, also in organic poultry production. Full article

(This article belongs to the Special Issue Salmonella and Salmonellosis)

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12 pages, 5184 KiB

Open AccessArticle

Salmonella Bacterin Vaccination Decreases Shedding and Colonization of Salmonella Typhimurium in Pigs

by Eduarda Alexandra Gonçalves de Oliveira Moura, Daniela Gomes da Silva, Caio Henrique Turco, Thainara Vitoria Carnevalli Sanches, Gabriel Yuri Storino, Henrique Meiroz de Souza Almeida, Marina Lopes Mechler-Dreibi, Isabela Peixoto Rabelo, Karina Sonalio and Luís Guilherme de Oliveira

Microorganisms 2021, 9(6), 1163; https://doi.org/10.3390/microorganisms9061163 - 28 May 2021

Cited by 3 | Viewed by 2733

Abstract

Since the occurrence of swine salmonellosis has increased over time and control strategies other than biosecurity are highly recommended, the present study aimed to evaluate the efficacy of vaccination with Salmonella Choleraesuis and Salmonella Typhimurium bacterins in pigs. Two experimental groups were formed: [...] Read more.

Since the occurrence of swine salmonellosis has increased over time and control strategies other than biosecurity are highly recommended, the present study aimed to evaluate the efficacy of vaccination with Salmonella Choleraesuis and Salmonella Typhimurium bacterins in pigs. Two experimental groups were formed: G1, animals immunized with two doses of a commercial vaccine (n = 20); G2, control group (n = 20). After vaccination, all pigs were orally challenged (D0) with 10⁸ CFU of Salmonella Typhimurium and evaluated for 40 days. Every 10 days after D0, five piglets from each experimental group were euthanized and submitted to the necroscopic examination, when organ samples were collected. Blood samples and rectal swabs were collected before the first dose of the vaccine (D−42), before the second dose (D−21), before the challenge (D0), and thereafter, every three days until D39. Blood count, serum IgG measurement by ELISA, and the excretion of Salmonella Typhimurium in feces were evaluated. While the results from blood count and serum IgG concentration did not differ, the detection and excretion of Salmonella between G1 and G2 differed (p < 0.05). Therefore, it was observed that this vaccine partially protected the animals against experimental infection with Salmonella Typhimurium, reducing the excretion of bacteria in feces. Full article

(This article belongs to the Special Issue Salmonella and Salmonellosis)

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19 pages, 723 KiB

Open AccessArticle

Characterization of Salmonella Isolates Recovered from Stages of the Processing Lines at Four Broiler Processing Plants in Trinidad and Tobago

by Anisa Sarah Khan, Karla Georges, Saed Rahaman, Woubit Abebe and Abiodun Adewale Adesiyun

Microorganisms 2021, 9(5), 1048; https://doi.org/10.3390/microorganisms9051048 - 13 May 2021

Cited by 8 | Viewed by 2452

Abstract

This cross-sectional study determined the prevalence, characteristics, and risk factors for contamination of chicken with Salmonella at four operating broiler processing plants in Trinidad. Standard methods were used to isolate and characterize the Salmonella isolates. The overall prevalence of Salmonella at the four [...] Read more.

This cross-sectional study determined the prevalence, characteristics, and risk factors for contamination of chicken with Salmonella at four operating broiler processing plants in Trinidad. Standard methods were used to isolate and characterize the Salmonella isolates. The overall prevalence of Salmonella at the four processing plants was 27.0% (107/396). The whole carcass enrichment (WCE) method yielded a statistically significantly (p = 0.0014) higher frequency of isolation (53.9%; 97/180) than the whole carcass rinse (35.0%; 63/180) and neck skin methods (42.2%; 38/90). S. enterica serotypes Enteritidis, Javiana, and Infantis were the predominant serotypes isolated accounting for 20.8%, 16.7% and 12.5%, respectively, of the serotyped isolates. Risk factors included the use of over 100 contract farmers (OR 4.4), pre-chiller (OR 2.3), addition of chlorine to chiller (OR 3.2), slaughtering sick broilers (OR 4.4), and flocks with >50% mortality. Multi-drug resistance was detected in 12.3% (14/114) of the isolates of Salmonella. Resistance was high to kanamycin (85.7%) and doxycycline (74.6%) but low to amoxicillin-clavulanic acid (2.4%) and sulphamethoxazole-trimethoprim (0.8%). The occurrence of resistant Salmonella in chickens processed at commercial broiler processing plants has implications for salmonellosis and therapeutic failure in consumers of improperly cooked contaminated chickens from these plants in the country. Full article

(This article belongs to the Special Issue Salmonella and Salmonellosis)

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11 pages, 566 KiB

Open AccessArticle

Salmonella in Captive Reptiles and Their Environment—Can We Tame the Dragon?

by Magdalena Zając, Magdalena Skarżyńska, Anna Lalak, Renata Kwit, Aleksandra Śmiałowska-Węglińska, Paulina Pasim, Krzysztof Szulowski and Dariusz Wasyl

Microorganisms 2021, 9(5), 1012; https://doi.org/10.3390/microorganisms9051012 - 08 May 2021

Cited by 21 | Viewed by 2710

Abstract

Reptiles are considered a reservoir of a variety of Salmonella (S.) serovars. Nevertheless, due to a lack of large-scale research, the importance of Reptilia as a Salmonella vector still remains not completely recognized. A total of 731 samples collected from reptiles [...] Read more.

Reptiles are considered a reservoir of a variety of Salmonella (S.) serovars. Nevertheless, due to a lack of large-scale research, the importance of Reptilia as a Salmonella vector still remains not completely recognized. A total of 731 samples collected from reptiles and their environment were tested. The aim of the study was to assess the prevalence of Salmonella in exotic reptiles kept in Poland and to confirm Salmonella contamination of the environment after reptile exhibitions. The study included Salmonella isolation and identification, followed by epidemiological analysis of the antimicrobial resistance of the isolates. Implementation of a pathway additional to the standard Salmonella isolation protocol led to a 21% increase in the Salmonella serovars detection rate. The study showed a high occurrence of Salmonella, being the highest at 92.2% in snakes, followed by lizards (83.7%) and turtles (60.0%). The pathogen was also found in 81.2% of swabs taken from table and floor surfaces after reptile exhibitions and in two out of three egg samples. A total of 918 Salmonella strains belonging to 207 serovars and serological variants were obtained. We have noted the serovars considered important with respect to public health, i.e., S. Enteritidis, S. Typhimurium, and S. Kentucky. The study proves that exotic reptiles in Poland are a relevant reservoir of Salmonella. Full article

(This article belongs to the Special Issue Salmonella and Salmonellosis)

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7 pages, 232 KiB

Open AccessCommunication

Comparison of Molecular and In Silico Salmonella Serotyping for Salmonella Surveillance

by Linda Chui, Christina Ferrato, Vincent Li and Sara Christianson

Microorganisms 2021, 9(5), 955; https://doi.org/10.3390/microorganisms9050955 - 29 Apr 2021

Cited by 6 | Viewed by 1871

Abstract

Salmonella surveillance and outbreak management is a key function of public health. Laboratories are shifting from antigenic serotype determination to molecular methods including microarray or whole genome sequencing technologies. The objective of this study was to compare the Check&Trace Salmonella™ DNA microarray (CTS), [...] Read more.

Salmonella surveillance and outbreak management is a key function of public health. Laboratories are shifting from antigenic serotype determination to molecular methods including microarray or whole genome sequencing technologies. The objective of this study was to compare the Check&Trace Salmonella™ DNA microarray (CTS), a commercially available assay with the Salmonella in silico typing resource (SISTR), which uses whole genome sequencing technology for serotyping clinical Salmonella strains in Alberta, Canada, collected over an 18-month period. A high proportion of isolates (96.3%) were successfully typed by both systems. SISTR is a powerful tool for laboratories which already have a WGS infrastructure in place, whereas smaller laboratories can benefit from a commercial microarray system and reduce the processing cost per isolate compared to traditional serotyping. Full article

(This article belongs to the Special Issue Salmonella and Salmonellosis)

15 pages, 11032 KiB

Open AccessArticle

Re-Emergence of Salmonellosis in Hog Farms: Outbreak and Bacteriological Characterization

by Mariana Meneguzzi, Caroline Pissetti, Raquel Rebelatto, Julian Trachsel, Suzana Satomi Kuchiishi, Adrienny Trindade Reis, Roberto Maurício Carvalho Guedes, Joice Aparecida Leão, Caroline Reichen and Jalusa Deon Kich

Microorganisms 2021, 9(5), 947; https://doi.org/10.3390/microorganisms9050947 - 27 Apr 2021

Cited by 9 | Viewed by 2223

Abstract

Clinical salmonellosis has been increasing significantly in Brazil in recent years. A total of 130 outbreaks distributed among 10 swine-producing states were investigated. One representative Salmonella isolate from each outbreak was characterized through serotyping, antimicrobial resistance profiles, PFGE, and WGS. From 130 outbreaks: [...] Read more.

Clinical salmonellosis has been increasing significantly in Brazil in recent years. A total of 130 outbreaks distributed among 10 swine-producing states were investigated. One representative Salmonella isolate from each outbreak was characterized through serotyping, antimicrobial resistance profiles, PFGE, and WGS. From 130 outbreaks: 50 were enteric, 48 were septicemic, 17 cases were characterized as hepato-biliary invasive, 13 as nodal and two were not classified. The most prevalent serovars were a monophasic variant of S. typhimurium (55/130), Choleraesuis (46/130), and Typhimurium (14/130). Most of the strains (86.92%) demonstrated a high rate of multi-drug resistance. The identification of a major Choleraesuis clonal group in several Brazilian states sharing the same resistance genes suggested that these strains were closely related. Six strains from this clonal group were sequenced, revealing the same ST-145 and 11 to 47 different SNPs. The detected plasmid type showed multiple marker genes as RepA_1_pKPC-CAV1321, the first to be reported in Salmonella. All AMR genes detected in the genomes were likely present on plasmids, and their phenotype was related to genotypic resistance genes. These findings reveal that salmonellosis is endemic in the most important pig-producing states in Brazil, emphasizing the need to make data available to aid in reducing its occurrence. Full article

(This article belongs to the Special Issue Salmonella and Salmonellosis)

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14 pages, 2733 KiB

Open AccessArticle

Fate of Salmonella spp. in the Fresh Soft Raw Milk Cheese during Storage at Different Temperatures

by Adriana Lobacz and Justyna Zulewska

Microorganisms 2021, 9(5), 938; https://doi.org/10.3390/microorganisms9050938 - 27 Apr 2021

Cited by 11 | Viewed by 2745

Abstract

The aim of this study was to determine the survival kinetics of Salmonella spp. in unripened, fresh raw milk cheese during storage at 5, 15 and 25 °C. Microbiological (coliforms and E. coli, S. thermophilus, Lactococcus sp., total microbial count and [...] Read more.

The aim of this study was to determine the survival kinetics of Salmonella spp. in unripened, fresh raw milk cheese during storage at 5, 15 and 25 °C. Microbiological (coliforms and E. coli, S. thermophilus, Lactococcus sp., total microbial count and Enterobacteriaceae) and physicochemical (pH and a_w) characteristics were also determined. Two primary models were used to estimate the kinetic parameters of Salmonella spp., namely Weibull and Baranyi and Roberts (no lag) models. Additionally, goodness-of-fit of the primary models was assessed by calculating the R-Square and mean square error. Salmonella spp. growth in the unripened raw milk cheese was inhibited during storage, but nevertheless bacteria survived at 5 °C for 33 days (2.5 log cfu/g) and 15 °C for 18 days (1.8 log cfu/g). A decrease in the number of Salmonella spp. populations from an initial concentration 6.6 log cfu/g to below a detection limit was observed at 25 °C after 7 days of storage of contaminated cheese samples. It was concluded that the storage temperature significantly influenced the inactivation rate of Salmonella spp. in fresh raw milk cheese and proceeded faster at 25 °C compared to remaining storage temperatures. Full article

(This article belongs to the Special Issue Salmonella and Salmonellosis)

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15 pages, 1146 KiB

Open AccessArticle

Mitigating the Spread and Translocation of Salmonella Enteritidis in Experimentally Infected Broilers under the Influence of Different Flooring Housing Systems and Feed Particle Sizes

by Marwa F. E. Ahmed, Amr Abd El-Wahab, Jan-Philip Kriewitz, Julia Hankel, Bussarakam Chuppava, Christine Ratert, Venja Taube, Christian Visscher and Josef Kamphues

Microorganisms 2021, 9(4), 874; https://doi.org/10.3390/microorganisms9040874 - 18 Apr 2021

Viewed by 2141

Abstract

This study aimed to evaluate the influences of different flooring designs and feed particle sizes on the spread of Salmonella (S.) in broiler chickens. Birds (n = 480) were allocated to four different housing systems (fully littered with and without [...] Read more.

This study aimed to evaluate the influences of different flooring designs and feed particle sizes on the spread of Salmonella (S.) in broiler chickens. Birds (n = 480) were allocated to four different housing systems (fully littered with and without floor heating, partially and fully slatted flooring with sand bath) and two dietary treatments (finely and coarsely ground diets) in 24 boxes. Two broilers per box were experimentally infected with S. Enteritidis (8.00 log₁₀ CFU/bird) at d 17. Salmonella prevalence in caecal contents and the liver was highest in broilers housed on fully slatted floor until d 36/37 (88.1% and 91.5%, respectively), and lowest in litter flooring (caecal content 64.4%) and litter flooring with floor heating (liver 61.7%). In turn, broilers on littered flooring expressed the lowest Salmonella counts in caecal content at d 36/37 (2.21 ± 1.75 log₁₀ CFU/g), partial slatted flooring the highest (3.76 ± 1.46 log₁₀ CFU/g). The mean Salmonella count in the caecal content was significantly lower for birds fed a coarsely ground diet (0.96 and 1.94 log₁₀ CFU/g) than a finely ground diet (5.07 and 3.34 log₁₀ CFU/g) at d 23 and d 36/37, respectively (p < 0.0001). Slatted flooring with a sand bath did not show advantages in terms of Salmonella reduction, whereas the coarsely ground diet markedly reduced the spread of Salmonella. Full article

(This article belongs to the Special Issue Salmonella and Salmonellosis)

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11 pages, 1120 KiB

Open AccessArticle

Occurrence of Salmonella in the Cattle Production in France

by Laetitia Bonifait, Amandine Thépault, Louise Baugé, Sandra Rouxel, Françoise Le Gall and Marianne Chemaly

Microorganisms 2021, 9(4), 872; https://doi.org/10.3390/microorganisms9040872 - 17 Apr 2021

Cited by 12 | Viewed by 2825

Abstract

Salmonella is among the most common foodborne pathogens worldwide, and can lead to acute gastroenteritis. Along with poultry, cattle production is recognized as an important source of human infection. Salmonella transmission from cattle to humans can occur through the environment, or through close [...] Read more.

Salmonella is among the most common foodborne pathogens worldwide, and can lead to acute gastroenteritis. Along with poultry, cattle production is recognized as an important source of human infection. Salmonella transmission from cattle to humans can occur through the environment, or through close contact with sick animals or their derived products. This study aimed to investigate the intestinal carriage of Salmonella spp. within French cattle production. A total of 959 cattle intestinal samples, from one of the largest French slaughterhouses, were analyzed. Isolated strains were genotyped by pulsed field gel electrophoresis (PFGE), and a sub-selection was taken by whole genome sequencing (WGS). Twenty-nine samples were positive for Salmonella spp., yielding an estimated prevalence of 3% in cattle production. Eight different Salmonella serotypes were found: Montevideo was the most prevalent (34%), followed by Mbandaka (24%) and Anatum (14%). PFGE genotyping allowed the clustering of Salmonella isolates according to their serotype. Within the clusters, some isolates presented 100% similarity. To investigate potential epidemiological links between them, WGS and core genome multilocus sequence typing (cgMLST) were used, revealing identical profiles between isolates originating from different areas and/or different animal breeds. This investigation provides new insights on Salmonella serotype epidemiology in cattle production in France. Full article

(This article belongs to the Special Issue Salmonella and Salmonellosis)

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15 pages, 2249 KiB

Open AccessArticle

Characterisation of Phage Susceptibility Variation in Salmonellaenterica Serovar Typhimurium DT104 and DT104b

by Manal Mohammed and Beata Orzechowska

Microorganisms 2021, 9(4), 865; https://doi.org/10.3390/microorganisms9040865 - 17 Apr 2021

Cited by 5 | Viewed by 2899

Abstract

The surge in mortality and morbidity rates caused by multidrug-resistant (MDR) bacteria prompted a renewal of interest in bacteriophages (phages) as clinical therapeutics and natural biocontrol agents. Nevertheless, bacteria and phages are continually under the pressure of the evolutionary phage–host arms race for [...] Read more.

The surge in mortality and morbidity rates caused by multidrug-resistant (MDR) bacteria prompted a renewal of interest in bacteriophages (phages) as clinical therapeutics and natural biocontrol agents. Nevertheless, bacteria and phages are continually under the pressure of the evolutionary phage–host arms race for survival, which is mediated by co-evolving resistance mechanisms. In Anderson phage typing scheme of Salmonella Typhimurium, the epidemiologically related definitive phage types, DT104 and DT104b, display significantly different phage susceptibility profiles. This study aimed to characterise phage resistance mechanisms and genomic differences that may be responsible for the divergent phage reaction patterns in S. Typhimurium DT104 and DT104b using whole genome sequencing (WGS). The analysis of intact prophages, restriction–modification systems (RMS), plasmids and clustered regularly interspaced short palindromic repeats (CRISPRs), as well as CRISPR-associated proteins, revealed no unique genetic determinants that might explain the variation in phage susceptibility among the two phage types. Moreover, analysis of genes coding for potential phage receptors revealed no differences among DT104 and DT104b strains. However, the findings propose the need for experimental assessment of phage-specific receptors on the bacterial cell surface and analysis of bacterial transcriptome using RNA sequencing which will explain the differences in bacterial susceptibility to phages. Using Anderson phage typing scheme of Salmonella Typhimurium for the study of bacteria-phage interaction will help improving our understanding of host–phage interactions which will ultimately lead to the development of phage-based technologies, enabling effective infection control. Full article

(This article belongs to the Special Issue Salmonella and Salmonellosis)

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17 pages, 6179 KiB

Open AccessArticle

CD4+ and CD8+ Circulating Memory T Cells Are Crucial in the Protection Induced by Vaccination with Salmonella Typhi Porins

by Luis Ontiveros-Padilla, Alberto García-Lozano, Araceli Tepale-Segura, Tania Rivera-Hernández, Rodolfo Pastelin-Palacios, Armando Isibasi, Lourdes A. Arriaga-Pizano, Laura C. Bonifaz and Constantino López-Macías

Microorganisms 2021, 9(4), 770; https://doi.org/10.3390/microorganisms9040770 - 07 Apr 2021

Cited by 1 | Viewed by 2444

Abstract

Salmonella enterica serovar Typhi (S. Typhi) porins, OmpC and OmpF, are potent inducers of the immune response against S. Typhi in mice and humans. Vaccination with porins induces the protection against 500 LD₅₀ of S. Typhi, life-lasting bactericidal [...] Read more.

Salmonella enterica serovar Typhi (S. Typhi) porins, OmpC and OmpF, are potent inducers of the immune response against S. Typhi in mice and humans. Vaccination with porins induces the protection against 500 LD₅₀ of S. Typhi, life-lasting bactericidal antibodies and effector T cell responses in mice; however, the nature of the memory T cell compartment and its contribution to protection remains unknown. In this work, we firstly observed that vaccination with porins induces in situ (skin) CD4+ and CD8+ T cell responses. Analysis of the porin-specific functional responses of skin CD4+ and CD8+ T cells showed IFN-gamma- and IL-17-producing cells in both T cell populations. The memory phenotype of porin-specific T cells indicated the presence of resident and effector memory phenotypes in the skin, and a central memory phenotype in the skin-draining lymph node. In addition, we demonstrated that vaccination with porins via skin reduces the bacterial burden following challenge. Finally, evaluating the role of the circulating T cell memory population in protection, we showed that circulating memory CD4+ and CD8+ T cells are crucial in porin-mediated protection against S. Typhi. Overall, this study highlights the importance of inducing circulating memory T cell responses in order to achieve the optimal protection provided by porins, showing a mechanism that could be sought in the rational development of vaccines. Full article

(This article belongs to the Special Issue Salmonella and Salmonellosis)

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11 pages, 1534 KiB

Open AccessCommunication

Natural Antimicrobials Suitable for Combating Desiccation-Resistant Salmonella enterica in Milk Powder

by Ahmed G. Abdelhamid and Ahmed E. Yousef

Microorganisms 2021, 9(2), 421; https://doi.org/10.3390/microorganisms9020421 - 18 Feb 2021

Cited by 6 | Viewed by 2589

Abstract

Some Salmonella enterica strains survive well in low-water activity (low-a_w) foods and cause frequent salmonellosis outbreaks in these products. Methods are needed to overcome such desiccation-resistant Salmonella and to improve the safety of low-a_w foods. Building on a recent finding, [...] Read more.

Some Salmonella enterica strains survive well in low-water activity (low-a_w) foods and cause frequent salmonellosis outbreaks in these products. Methods are needed to overcome such desiccation-resistant Salmonella and to improve the safety of low-a_w foods. Building on a recent finding, we hypothesized that natural antimicrobial food additives, which are active against cytoplasmic membrane, could overcome this desiccation resistance phenomenon, and thus, sensitize the pathogen to drying and mild processing. Food additives were screened for the ability to cause leakage of intracellular potassium ions; retention of these ions is vital for protecting Salmonella against desiccation. Two antimicrobial food additives, carvacrol and thymol, caused considerable potassium leakage from the desiccation-resistant S. enterica serovars, Tennessee and Livingstone. Thus, carvacrol and thymol were investigated for their ability to sensitize the desiccation-adapted S. enterica to heat treatment. The combined use of food additives, at their minimum inhibitory concentrations, with heat treatment at 55 °C for 15 min caused 3.1 ± 0.21 to more than 5.5 log colony forming unit (CFU)/mL reduction in desiccation-adapted S. enterica, compared to 2.4 ± 0.53–3.2 ± 0.11 log CFU/mL reduction by sole heat treatment. Carvacrol was the additive that caused the greatest potassium leakage and sensitization of Salmonella to heat; hence, the application of this compound was investigated in a food model against Salmonella Typhimurium ASD200. Addition of carvacrol at 200 or 500 ppm into liquid milk followed by spray-drying reduced the strain’s population by 0.9 ± 0.02 and 1.3 ± 0.1 log CFU/g, respectively, compared to 0.6 ± 0.02 log CFU/g reduction for non-treated spray-dried milk. Additionally, freeze-drying of milk treated with high levels of carvacrol (5000 ppm) reduced the population of Salmonella Typhimurium ASD200 by more than 4.5 log CFU/g, compared to 1.1 ± 0.4 log CFU/g reduction for the freeze-dried untreated milk. These findings suggest that carvacrol can combat desiccation-resistant S. enterica, and thus, potentially improve the safety of low-a_w foods. Full article

(This article belongs to the Special Issue Salmonella and Salmonellosis)

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11 pages, 1123 KiB

Open AccessArticle

Control of Salmonella and Pathogenic E. coli Contamination of Animal Feed Using Alternatives to Formaldehyde-Based Treatments

by Rebecca J. Gosling, Ian Mawhinney, Kurt Richardson, Andrew Wales and Rob Davies

Microorganisms 2021, 9(2), 263; https://doi.org/10.3390/microorganisms9020263 - 27 Jan 2021

Cited by 10 | Viewed by 3364

Abstract

This study compared a novel non-formaldehyde combination product developed for pathogen control in animal feed Finio (A), with a panel of three commonly used organic acid feed additive products: Fysal (B), SalCURB K2 (C) and Salgard (D). Products were evaluated for their ability [...] Read more.

This study compared a novel non-formaldehyde combination product developed for pathogen control in animal feed Finio (A), with a panel of three commonly used organic acid feed additive products: Fysal (B), SalCURB K2 (C) and Salgard (D). Products were evaluated for their ability to reduce Salmonella Typhimurium DT104 and avian pathogenic Escherichia coli in poultry feed. A commercial layer-hen mash was treated with each product and then mixed with feed previously contaminated (via inoculated meat and bone meal) with either Salmonella or E. coli. After 24 h at room temperature, 10 replicate samples were taken from each preparation and plate counts were performed using a selective agar. All concentrations of product A (0.5, 1.0, 1.5, 2.0 and 2.5 kg per metric tonne (MT)) plus the higher concentration of products B and D (6.0 kg MT⁻¹) significantly reduced Salmonella counts compared with those in the untreated control group (p < 0.05). Product C did not significantly reduce levels of Salmonella under these conditions. Because of the poor recovery of E. coli, statistical comparisons for this organism were limited in scope, but only product A at the highest concentration appeared to have eliminated it. Full article

(This article belongs to the Special Issue Salmonella and Salmonellosis)

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11 pages, 3046 KiB

Open AccessArticle

Development of a Genoserotyping Method for Salmonella Infantis Detection on the Basis of Pangenome Analysis

by Seung-Min Yang, Jiwon Baek, Eiseul Kim, Hyeon-Be Kim, Seyoung Ko, Donghyuk Kim, Hyunjin Yoon and Hae-Yeong Kim

Microorganisms 2021, 9(1), 67; https://doi.org/10.3390/microorganisms9010067 - 29 Dec 2020

Cited by 7 | Viewed by 2847

Abstract

In recent years, Salmonella Infantis has become a predominant serovariant in clinical and poultry isolates, thereby imposing a substantial economic burden on both public health and the livestock industry. With the aim of coping with the steep increase in serovar Infantis prevalence, a [...] Read more.

In recent years, Salmonella Infantis has become a predominant serovariant in clinical and poultry isolates, thereby imposing a substantial economic burden on both public health and the livestock industry. With the aim of coping with the steep increase in serovar Infantis prevalence, a polymerase chain reaction (PCR)-based rapid and accurate diagnostic assay was developed in this study through pangenome profiling of 60 Salmonella serovars. A gene marker, SIN_02055, was identified, which is present in the S. Infantis genome but not in the pangenome of the other serovars. Primers specific to SIN_02055 were used to accurately detect serovar Infantis, and to successfully differentiate Infantis from the other 59 serovars in real-time PCR with a R² of 0.999 and an efficiency of 95.76%. The developed method was applied to 54 Salmonella strains belonging to eight dominant serovars, and distinguished Infantis from the other seven serovars with an accuracy of 100%. The diagnostic primer set also did not show false positive amplification with 32 strains from eight non-Salmonella bacterial species. This cost-effective and rapid method can be considered an alternative to the classic serotyping using antisera. Full article

(This article belongs to the Special Issue Salmonella and Salmonellosis)

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19 pages, 2423 KiB

Open AccessArticle

Genotyping Study of Salmonella 4,[5],12:i:- Monophasic Variant of Serovar Typhimurium and Characterization of the Second-Phase Flagellar Deletion by Whole Genome Sequencing

by Ainhoa Arrieta-Gisasola, Aitor Atxaerandio-Landa, Victoria Garrido, María Jesús Grilló, Ilargi Martínez-Ballesteros, Lorena Laorden, Javier Garaizar and Joseba Bikandi

Microorganisms 2020, 8(12), 2049; https://doi.org/10.3390/microorganisms8122049 - 21 Dec 2020

Cited by 10 | Viewed by 2711

Abstract

After Salmonella Enteritidis and S. Typhimurium, S. 4,[5],12:i:- is the most reported serovar in human clinical cases. During the past 20 years, many tools have been used for its typing and second-phase flagellar deletion characterization. Currently, whole genome sequencing (WGS) and different bioinformatic [...] Read more.

After Salmonella Enteritidis and S. Typhimurium, S. 4,[5],12:i:- is the most reported serovar in human clinical cases. During the past 20 years, many tools have been used for its typing and second-phase flagellar deletion characterization. Currently, whole genome sequencing (WGS) and different bioinformatic programs have shown the potential to be more accurate than earlier tools. To assess this potential, we analyzed by WGS and in silico typing a selection of 42 isolates of S. 4,[5],12:i:- and S. Typhimurium with different in vitro characteristics. Comparative analysis showed that SeqSero2 does not differentiate fljB-positive S. 4,[5],12:i:- strains from those of serovar Typhimurium. Our results proved that the strains selected for this work were non-clonal S. 4,[5],12:i:- strains circulating in Spain. Using WGS data, we identified 13 different deletion types of the second-phase flagellar genomic region. Most of the deletions were generated by IS26 insertions, showing orientation-dependent conserved deletion ends. In addition, we detected S. 4,[5],12:i:- strains of the American clonal line that would give rise to the Southern European clone in Spain. Our results suggest that new S. 4,[5],12:i:- strains are continuously emerging from different S. Typhimurium strains via different genetic events, at least in swine products. Full article

(This article belongs to the Special Issue Salmonella and Salmonellosis)

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12 pages, 1590 KiB

Open AccessArticle

Validating Thermal Lethality to Salmonella enterica in Chicken Blood by Simulated Commercial Rendering

by Caleb Wong de la Rosa, Kourtney A. Daniels, Rosana G. Moreira, Chris R. Kerth and Thomas M. Taylor

Microorganisms 2020, 8(12), 2009; https://doi.org/10.3390/microorganisms8122009 - 16 Dec 2020

Cited by 2 | Viewed by 2648

Abstract

The U.S. rendering industry produces materials for use in further processed animal foods and feeds and is required to scientifically validate food safety hazard control. This study aimed to provide lethality validation for Salmonella enterica during simulated commercial rendering of whole chicken blood. [...] Read more.

The U.S. rendering industry produces materials for use in further processed animal foods and feeds and is required to scientifically validate food safety hazard control. This study aimed to provide lethality validation for Salmonella enterica during simulated commercial rendering of whole chicken blood. Chicken blood was inoculated with a blend of multiple serovars of the pathogen (S. Heidelberg, Typhimurium, Senftenberg) and subjected to heating at 82.2, 87.8, or 93.3 °C; surviving cells were enumerated incrementally up to 5.0 min. Survivor data were modeled using the GInaFiT 1.7 freeware package. D-values and t_7D (time to a 7.0 log₁₀-cycle inactivation) values were generated from best-fit model parameters. Predictive modeling analysis revealed that the survival curves of Salmonella possessed log-linear components but also possessed shoulder and/or tail components. Mean D-values declined from 0.61 to 0.12 min as heating temperature was raised from 82.2 to 93.3 °F, respectively, differing by heating temperature (p = 0.023). t_7D values differed significantly by heating temperature (p = 0.001), as was also the case for shoulder length (S_L) (p = <0.0001), where, at lower temperatures, a shoulder was observed versus heating at 93.3 °F. These data aid scientific validation of Salmonella enterica inactivation during thermal rendering of poultry blood for use in further processed animal foods. Full article

(This article belongs to the Special Issue Salmonella and Salmonellosis)

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Review

Jump to: Research, Other

15 pages, 1106 KiB

Open AccessReview

Whole Genome Sequencing Analysis of Salmonella enterica Serovar Typhi: History and Current Approaches

by Wan Ratmaazila Wan Wan Makhtar, Izwan Bharudin, Nurul Hidayah Samsulrizal and Nik Yusnoraini Yusof

Microorganisms 2021, 9(10), 2155; https://doi.org/10.3390/microorganisms9102155 - 15 Oct 2021

Cited by 7 | Viewed by 4649

Abstract

In recent years, the advance in whole-genome sequencing technology has changed the study of infectious diseases. The emergence of genome sequencing has improved the understanding of infectious diseases, which has revamped many fields, such as molecular microbiology, epidemiology, infection control, and vaccine production. [...] Read more.

In recent years, the advance in whole-genome sequencing technology has changed the study of infectious diseases. The emergence of genome sequencing has improved the understanding of infectious diseases, which has revamped many fields, such as molecular microbiology, epidemiology, infection control, and vaccine production. In this review we discuss the findings of Salmonella enterica serovar Typhi genomes, publicly accessible from the initial complete genome to the recent update of Salmonella enterica serovar Typhi genomes, which has greatly improved Salmonella enterica serovar Typhi and other pathogen genomic research. Significant information on genetic changes, evolution, antimicrobial resistance, virulence, pathogenesis, and investigation from the genome sequencing of S. Typhi is also addressed. This review will gather information on the variation of the Salmonella enterica serovar Typhi genomes and hopefully facilitate our understanding of their genome evolution, dynamics of adaptation, and pathogenesis for the development of the typhoid point-of-care diagnostics, medications, and vaccines. Full article

(This article belongs to the Special Issue Salmonella and Salmonellosis)

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Other

Jump to: Research, Review

14 pages, 2956 KiB

Open AccessHypothesis

AT Homopolymer Strings in Salmonella enterica Subspecies I Contribute to Speciation and Serovar Diversity

by Jean Guard, Adam R. Rivers, Justin N. Vaughn, Michael J. Rothrock, Jr., Adelumola Oladeinde and Devendra H. Shah

Microorganisms 2021, 9(10), 2075; https://doi.org/10.3390/microorganisms9102075 - 01 Oct 2021

Cited by 1 | Viewed by 1812

Abstract

Adenine and thymine homopolymer strings of at least 8 nucleotides (AT 8+mers) were characterized in Salmonella enterica subspecies I. The motif differed between other taxonomic classes but not between Salmonella enterica serovars. The motif in plasmids was possibly associated with serovar. Approximately 12.3% [...] Read more.

Adenine and thymine homopolymer strings of at least 8 nucleotides (AT 8+mers) were characterized in Salmonella enterica subspecies I. The motif differed between other taxonomic classes but not between Salmonella enterica serovars. The motif in plasmids was possibly associated with serovar. Approximately 12.3% of the S. enterica motif loci had mutations. Mutability of AT 8+mers suggests that genomes undergo frequent repair to maintain optimal gene content, and that the motif facilitates self-recognition; in addition, serovar diversity is associated with plasmid content. A theory that genome regeneration accounts for both persistence of predominant Salmonella serovars and serovar diversity provides a new framework for investigating root causes of foodborne illness. Full article

(This article belongs to the Special Issue Salmonella and Salmonellosis)

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