Correlation between cefepime utilisation and Pseudomonas aeruginosa resistance rates to β-lactams and carbapenems in patients with healthcare-associated infections.

OBJECTIVES: There is direct link between overutilisation or abuse of antibiotics and Pseudomonas aeruginosa resistance rates, but other factors may also influence the resistance rate. This study aimed to observe changes in P. aeruginosa resistance rates in patients with hospital-acquired infections (HAIs) following a period of cefepime unavailability in an ICU.

METHODS: The study was designed as a retrospective observational analysis of trends in antibiotic utilisation and density of antibiotic resistance. It covered only P. aeruginosa isolates causing HAIs obtained from patients aged >18years. Isolates taken <48h after admission to the ICU and duplicate isolates were excluded. The effects of cefepime withdrawal from prescribing during the 2-year period on P. aeruginosa resistance density trends were also followed.

RESULTS: During the study period (2009-2016), a total of 318 non-duplicate P. aeruginosa isolates causing HAIs in the ICU were collected. The predominant anatomical localisation of these infections (nearly 95%) was the lungs (pneumonia), surgical sites and urinary tract (69.18%, 18.24% and 6.92%, respectively). The isolates showed a lower resistance density (per/1000 PDs) in the last year (2016) compared with the first year of observation (2009) for all monitored antibiotics, with a peak in 2011. Although a decreasing trend of resistance density was recorded for all examined drugs, statistical significance was noted only for imipenem, meropenem and piperacillin/tazobactam (P<0.05) CONCLUSIONS: Temporary withdrawal of cefepime in a hospital resulted in a significant decrease in the density of P. aeruginosa isolates resistant to imipenem, meropenem, piperacillin/tazobactam, ceftazidime and cefepime.