Epidemiology of typhoid and paratyphoid fever in Kathmandu: two years study and trends of antimicrobial resistance.

Enteric fever is prevalent in developing countries including Nepal, where it still remains as a major health problem. Appropriate antibiotics are essential for the treatment of typhoid and paratyphoid fever. A prospective study was carried out to characterize the epidemiological features of enteric fever in Kathmandu, Nepal and to analyse the recent trend of antimicrobial resistance pattern of the Salmonella isolated from the cases of enteric fever from different hospitals in Kathmandu during June, 2002 to June, 2004. A total of 1469 Salmonella typhi and Salmonella paratyphi 'A' isolates collected during this period from five different hospital laboratories situated in Kathmandu were studied. The antimicrobial susceptibilities of the isolates towards Ampicillin (10 mcg), Chloramphenicol (30 mcg), Cotrimoxazole (25 mcg), Ciprofloxacin (5 mcg) and Ceftriaxone (5 mcg) were determined by standard disc diffusion technique and Agar dilution technique were used to determine the minimum inhibitory concentration (MIC) for Ampicillin, Ciprofloxacin, Chloramphenicol and Ceftriaxone. All the isolates tested were found to be sensitive to Ceftriaxone and Ciprofloxacin, the most commonly used antibiotic for treatment of enteric fever in Nepal. Of the total isolates studied, 15.5% from 2002, 8% from 2003 and 3.45% from 2004 were found to be multidrug resistant (exhibiting resistance towards Ampicillin, Chloramphenicol and Cotrimoxazole). Of the total multi drug resistant Salmonella isolates, 92% were Salmonella typhi. All the multidrug resistant isolates were also further tested for susceptibilities towards Tetracycline (30 mcg), Nalidixic acid (30 mcg), Streptomycin (10 units), Gentamycin (25 mcg), Azithromycin (15 mcg), Kanamycin (30 mcg), Neomycin (30 mcg). 50% of the multi drug resistant Salmonella typhi were also resistant to Tetracycline. Plasmid analysis revealed that all of the multidrug resistant Salmonella typhi isolates with Tetracycline resistance harbored a large molecular weight (147 Kb) plasmid.