Trends in antibiotic susceptibility of enteric fever isolates from South India, 2002-2013

Enteric fever is endemic in India. Trends in antibiotic resistance in Salmonella enterica subspecies enterica serovars Typhi and Paratyphi A isolates over the past 12 years were studied.

A retrospective analysis of consecutive blood culture isolates of Salmonella Typhi and Salmonella Paratyphi A was performed from 2002 to 2013. Antibiotic susceptibility testing was carried out for ampicillin, chloramphenicol, cotrimoxazole, nalidixic acid (NA), ciprofloxacin and ceftriaxone by disc diffusion. The minimum inhibitory concentration of ciprofloxacin and azithromycin was determined using E-test strips. Mantel-Haenszel extended chi-square test was used for analysis of trends across years.

Three thousand two hundred ninety-six Salmonella spp. were isolated; of which, 1905 were identified as Salmonella Typhi (58%) and 1393 as Salmonella Paratyphi A (42%). Multidrug resistance (chloramphenicol, ampicillin and cotrimoxazole) was relatively stable throughout the study period. NA resistance increased from 18% in 2007 to 100% in 2013 among Salmonella Paratyphi A isolates and from 67% to 82% among Salmonella Typhi isolates. Complete susceptibility to ceftriaxone and azithromycin was observed in this study.

Knowledge of the local patterns of resistance would help in appropriate therapy for enteric fever. With increasing rates of fluoroquinolone resistance in our hospital setting, it is probably prudent to revert back to the first-line agents for treatment and save azithromycin and third-generation cephalosporins for difficult and non-responsive cases.