Antimicrobial susceptibility pattern and epidemiological investigation of the clinical isolates of Pseudomonas aeruginosa in 1999and 2000

: During 1999-2000, a total of 1,215 isolates of Pseudomonas aeruginosa (P. aeruginosa) were analyzed by wards, type of clinical specimens and serotypes. Antimicrobial susceptibility was also examined for 10 agents (PIPC, CAZ, LMOX, IPM-CS, GM, AMK, MINO, LVFX, NFLX, and ST) with criteria by NCCLS (M7-A5). Sputum (33%) was most common source of P. aeruginosa followed by urine (17) and wound discharge (14%). According to wards, the isolation rate at the critical care unit was the highest (40%) in 1999 but decreased to 14% in 2000. In the isolates from inpatients (1999, 2000) the resistance rate was 96.8-98.9% for MINO and ST, 23.5-30.8% for IPM-CS, 27.2-28.9% for LMOX, 12.5-20.1% for GM, and 6.7-11.8% for NFLX. Comparison between the two years showed increases in isolates resistant to GM (p<0.01) and NFLX (p<0.05) but a decrease in IPM-CS resistant isolates (p<0.01). According to serotypes, the E and G type were most frequently observed (242 isolates each, 21.8%) followed in order by F type (127 isolates, 11%) and the B type (124 isolates, 11%). The incidence of the F type was high compared with other medical institutions. There was a reduction in the rates of susceptibility of serotype E isolates to PIPC (74.4%) and GM (60.3%), and of serotype F isolates to IPM-CS (52%). Multidrug-resistant P. aeruginosa (MDR-PSA) that were resistant to beta-lactams, aminoglycosides, and new quinolons accounted for 3%.