Antimicrobial susceptibility patterns of urinary pathogens in Trinidad, 1996-1999

The prevalence of antimicrobial resistance among urinary pathogens has been increasing worldwide. Laboratory diagnosed urinary tract infections were retrospectively evaluated for the years 1996 through 1999, to document the common pathogens and their changing antimicrobial profiles. From 14,853 hospital specimens, an isolation rate of 6.1% was found; and from 5330 community specimens, the isolation rate was 27.9%. E. coli was the predominant cause of urinary tract infections in both hospital and community practices. The rate of isolation of the other pathogens was relatively stable except for citrobacter species, which increased from 1.3% in 1996 to 20.1% in 1999 (p < 0.001) among community isolates. Significant changes in the susceptibility patterns of uropathogens also were observed. E. coli strains from hospitals were significantly more resistant to cefuroxime than community strains (p < 0.001), while resistance to ampicillin and nalidixic acid was high in both practices. No substantial changes in susceptibility to gentamicin and tetracycline were noticed during the four-year period compared to the 99% resistance to tetracycline in 1995. In relation to nitrofurantoin, no significant changes were noted in both practices where resistant rates remained low, but susceptibility to augmentin showed much improvement among all isolates, including E. coli. Urinary isolates were more commonly recovered from the paediatric age group (1-10 years) and those older than 50 years of age, and males were the predominant gender in both age groups. The study showed that the antibiotics useful in the treatment of UTI in decreasing order of effectiveness in community practice were gentamicin, norfloxacin, nitrofurantoin and cefuroxime. For nosocomial UTI, the drugs most effective include norfloxacin, nitrofurantoin, gentamicin, co-trimoxazole and amoxicillin-clavulanic acid.