Antibiotic susceptibility and genotype patterns of Pseudomonas aeruginosa from mechanical ventilation-associated pneumonia in intensive care units.

Pseudomonas aeruginosa (P. aeruginosa) is a leading cause of morbidity and mortality in patients with ventilation-associated pneumonia (VAP). It is difficult to treat this infection due to acquired resistance to various antibiotics. In order to understand the potential route of transmission, it is important to have detailed knowledge of the genotypes and antibiotic susceptibility of P. aeruginosa. The aim of this study was to determine antibiotic susceptibility using the broth microdilution minimum inhibitory concentration (MIC) method and to apply the Randomly Amplified Polymorphic DNA (RAPD) typing method for VAP caused by P. aeruginosa in 16 patients (8 men and 8 women; average age at inclusion, 67.8 years; range, 53-76 years). To determine antibiotic susceptibility, imipenem (IPM), cefepime (FEP) and meropenem (MEM) were administered for the treatment of P. aeruginosa, yielding an effectiveness of 75, 62.5, and 62.5%, respectively. According to the National Committee for Clinical Laboratory Standards (NCCLS) breakpoints, 8 (50%) of the 16 mechanical ventilation (MV) isolates were resistant to ceftazidime (CAZ) and pipenacillin (PIP). Amikacin (AK) and aztreonam (AZT) were not as effective against P. aeruginosa (75%). In addition, P. aeruginosa was completely resistant to ciprofloxacin (CIP). The MV isolates were susceptible to polymyxin B (PB). RAPD analysis revealed 12 genotypes for all the isolated P. aeruginosa, separated into 4 patterns. The results demonstrated a high incidence of P. aeruginosa isolated from VAP, with endogenous and cross infections being potential reasons for P. aeruginosa isolated from VAP in the intensive care units.