Epidemiology of Typhoid and Paratyphoid Fever in Kathmandu : Two Years Study and Trends of Antimicrobial Resistance

Abstract

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 (10mcg), Chloramphenicol (30mcg), Cotrimoxazole (25mcg), Ciprofloxacin (5mcg) and Ceftriaxone
(5mcg) 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 (30mcg), Nalidixic acid (30 mcg), Streptomycin (10units), Gentamycin (25mcg), Azithromycin
(15mcg), Kanamycin (30mcg), Neomycin (30mcg). 50% of the multi drug resistant Salmonella typhi were
also resistant to Tetracycline. Plasmid analysis revealed that all of the Mutidrug resistant Salmonella typhi
isolates with Tetracycline resistance harbored a large molecular weight (147 Kb) plasmid.
Key Words: Enteric fever, Salmonella, Antibiotic, Plasmid, Multidrugresistant