Patients receiving hematopoietic stem-cell transplantation (HSCT) are prone to develop invasive infections due to disease and transplantation-related immunosuppression. The main causative agents often originate from the digestive tract and are multidrug-resistant. Our aim was to investigate the in vitro activity of ceftazidime-avibactam (CZA) against extended spectrum beta-lactamase (ESBL)-producing and carbapenem-resistant (CR) Gram-negative bacteria recovered from blood and fecal samples of patients following HSCT, hospitalized in University Hospital “Saint Marina”—Varna, during 2019–2021.
A total of 48 isolates (E. coli, n = 20; Enterobacter cloacae, n = 9; Klebsiella pneumoniae, n = 6; Serratia marcescens, n = 1; Acinetobacter baumannii, n = 2; Pseudomonas putida, n = 4; Pseudomonas aeruginosa, n = 4; Pseudomonas mendocina, n = 1; Pseudomonas composti, n = 1) were studied. MALDI Biotyper Sirius (Bruker, Bremen, Germany) and the automated Phoenix system (BD, Franklin Lakes, NJ, USA) were used for species identification and susceptibility testing. Twenty-four isolates, included in this study, were resistant to third- and fourth-generation cephalosporins and, therefore, were identified as ESBL producers (E. coli, n = 12; E. cloacae, n = 7; K. pneumoniae, n = 4; S. marcescens, n = 1). A multiplex polymerase chain reaction was used for gene detection, associated with carbapenem resistance. In the studied group, eleven isolates (23%) were CR (E. cloacae, n = 1; Pseudomonas spp., n = 8; A. baumannii, n = 2). All 24 ESBL-producing isolates were CZA-susceptible. In the group of CR isolates, only 1 P. aeruginosa was susceptible to CZA, while 10 CR isolates were resistant. Genes associated with class B and class D carbapenemases were detected by PCR (blaVIM and blaOXA-like).
In conclusion, in our study, all ESBL producers were susceptible to CZA, while 91% of the CR isolates (all class B and class D carbapenemase producers) were resistant. CZA is a drug combination that is highly active against ESBL producers, but its spectrum of activity is limited against carbapenemase producers. Therefore, other novel antimicrobial agents are urgently needed.
Author Contributions
Conceptualization, D.N. and T.S.; methodology, D.N.; validation, D.N., D.S. and T.S.; formal analysis, I.M.; investigation, D.N.; resources, I.M.; data curation, D.N.; writing—original draft preparation, D.N.; writing—review and editing, T.S.; supervision, T.S.; project administration, D.N.; funding acquisition, D.S. All authors have read and agreed to the published version of the manuscript.
Funding
This research was funded by Medical University of Varna grant number [19019].
Institutional Review Board Statement
The study was conducted in accordance with the Declaration of Helsinki, and approved by the Ethics Committee of Medical University of Varna (92/02.04.2020).
Informed Consent Statement
Not applicable.
Conflicts of Interest
The authors declare no conflict of interest.
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