The Re-Emergence of chloramphenicol sensitivity among enteric fever pathogens in Mangalore

Background: Enteric fever is a global health problem, especially in the developing countries of the tropics. Drug resistance among enteric fever pathogens is a major challenge for the clinicians. Since its introduction in 1948, chloramphenicol (C) remained as the drug of choice for enteric fever. Later, ciprofloxacin (Cf) replaced C, when C-resisitant enteric fever emerged and caused outbreaks in different parts of the world. Fluoroquinlones are replaced by third generation cephalosporins like ceftriaxone (Ci) and cefotaxime (Ce) as the first line therapy nowadays. C-sensitive Salmonella serotypes emerged again due to the withdrawal of antibiotic pressure. Therefore, an attempt was made to study the incidence of blood stream Salmonella infections and their antimicrobial susceptibility pattern. Method: Strains isolated from 188 blood culture positive cases of enteric fever over a period of 1 year and 11 months were studied and their sensitivity pattern to chloramphenicol(C), ampicillin(A), cotrimoxazole(Co), nalidixic acid(Na), ciprofloxacin(Cf), ofloxacin(Of) and ceftriaxone(Ci) were analysed by the disk diffusion method according to the Clinical Laboratory Standard Institute(CLSI) guidelines. The Minimum Inhibitory Concentration (MIC) was determined for chloramphenicol by the agar dilution method according to the CLSI guidelines. Results: A total of 188(2.99%) Salmonella isolates were obtained from blood culture during the period of 1 year and 11 months. Of these, 77 were S.typhi and 111 were S.paratyphi A. The present study showed higher chloramphenicol sensitivity for S.typhi (97.4%) and S.paratyphi A (100%). The MIC for Chloramphenicol was ≤ 4 μg/ml for 187 Salmonella isolates. OneSalmonella isolate showed C - MIC of 64 μg/ml. Conclusion: This study has shown the reemergence of chloramphenicol sensitivity among enteric fever pathogens. The results suggest the necessity for the reevaluation of chloramphenicol therapy in enteric fever.