Significance and characterisation of pseudomonads from urinary tract specimens

Pseudomonads are commonly encountered in clinical samples. Usually ignored as contaminants, these organisms are known to cause nosocomial opportunistic infections like urinary tract infections (UTI). One hundred and two pseudomonads obtained in pure culture and significant numbers from 8400 consecutive urinary tract (UT) specimens were biochemically characterised upto species level by a battery of biochemical tests. Modified Stoke's disk diffusion method was followed for testing antibiotic susceptibility. Beta-lactamase production was checked by nitrocefin disk method. Minimum Inhibitory Concentration for some of these strains against imipenem was done by agar dilution method of NCCLS. Etiological significance of isolating these organisms from UT specimens was also assessed. P. aeruginosa was the commonest (76) followed by B. pickettii (10), P. putida (6), P.fluorescence (2), P. stutzeri (20) P. vesicularis (2), S. putrefaciens (2) and Stenotrophomonas maltophilia (2). Seventy six per cent of P. aeruginosa produced beta-lactamases as compared to 45% of other pseudomonads. The frequency of antibiotic resistance was gentamicin and ciprofloxacin (68.6%) followed by netilmicin (60.7%), ceftazidime (58.8%), amikacin (43.1%) and piperacillin (39.2%). In 42 patients (51.2%) the etiological significance of isolating a pseudomonad could be confirmed. Risk factors for development of UTI were present in 62(75%). Obstructive uropathy (20) followed by post operative period and surgery on urinary tract were the commonest risk factors involved. A high level of resistance was observed for imipenem (P. aeruginosa 43.7% and other pseudomonads 25%).