Enteric fever in Karachi: current antibiotic susceptibility of Salmonellae isolates.

OBJECTIVE To determine the current sensitivity and resistance profile of Salmonellae (S.) isolates in a laboratory setting. STUDY DESIGN An observational study. PLACE AND DURATION OF STUDY Dr. Essa`s Laboratory and Diagnostic Centre, Karachi, Pakistan, from November 2008 - October 2010. METHODOLOGY Isolates from blood culture specimens of 481 bacteraemic patients were identified using conventional biochemical tests. Salmonellae was confirmed with specific antisera and their antibiograms determined by Kirby-Bauer Disc Diffusion method using 12 relevant antibiotics. Inclusions of the study were bacteraemia documented in all blood samples positive for S. typhi, S. paratyphi-A and B. Exclusions were all samples other than blood and blood samples negative for S. typhi and S. paratyphi-A and B during the same period. Multidrug resistance (MDR) of isolates was defined as the isolates showing resistance to all conventional anti-typhoid medicines i.e., Chloramphenicol, Ampicillin and Co-trimoxazole. RESULTS Specimens (n=217) yielded 131 Salmonellae typhi (60.36%), 71 S. paratyphi-A (32.71%), and 15 S. paratyphi-B (6.9%); these were sensitive to the Quinolones [Enoxacin: 94.96% (n=91), Ciprofloxacin, 96.47% (n=182), Ofloxacin: 95.74% (n=203)], and Cephalosporins [Cefixime: 96.62% (n=202), Cefotaxime: 99.17% (n=206), Ceftriaxone: 98.79% (n=208)]. Resistance to Amoxicillin was 96.48% (n=128) and 29.91% (n=78) to Co-trimoxazole. About 62.64% (n=136) of the isolates were MDR strains. CONCLUSION Ciprofloxacin is currently a suitable empirical choice in presumed enteric fever cases, but culture and sensitivity analysis should be encouraged and results incorporated in prescription strategy. Increasing frequency of S. paratyphi-A isolates possibly suggests incomplete coverage employing monovalent vaccine.