Changes in Antibiotic Resistance Level of Nosocomial Pseudomonas Aeruginosa Isolates in the Largest University Hospital of Lithuania

The aim was to estimate changes in the resistance rates of Pseudomonas aeruginosa (P. aeruginosa) strains isolated from patients treated in intensive care units of the largest university hospital.
Materials and Methods. Isolates were identified with the Phoenix ID system (Becton Dickinson, USA). The minimum inhibitory concentration (MIC) of ceftazidime, ciprofloxacin, and amikacin were determined by the E-test and evaluated following the recommendations of the Clinical Laboratory Standards Institute.
Results. In 2003, the proportion of P. aeruginosa strains resistant to piperacillin was greatest followed by strains resistant gentamicin and ciprofloxacin. In 2008, the resistance rates markedly changed being the highest to ciprofloxacin. An increase in the resistance rates to ciprofloxacin (+24%, P<0.001) and ceftazidime (+8.3%, P<0.05) was documented. In 2003, there were 66.7% of P. aeruginosa strains sensitive to all antibiotics tested, and this percentage decreased to 47.5% in 2008 (P<0.05). During the study, a significant increase in the median MICs for ciprofloxacin and amikacin was observed (P<0.001); however, no significant change was documented for ceftazidime.
Conclusions. P. aeruginosa remains an important nosocomial pathogen with relatively high overall resistance to antimicrobial agents, and the resistance level is increasing.