Changing trend of antimicrobial susceptibility pattern of Salmonella spp. in different regions of Nepal: A six years surveillance study

The study was undertaken to evaluate the prevalence of enteric fever, antimicrobial susceptibility pattern, regional and seasonal distribution of Salmonella spp. in Nepal. Salmonella spp., the causative organism for enteric fever, is a major public health problem; especially in the developing countries and has gradually developed resistance to many antibiotics. Surveillance of antimicrobial resistance is helpful in assessing the burden of disease, trend of antimicrobial resistant pattern and effectiveness of antimicrobials used for treatment of infection. A study was conducted in 11 hospital based laboratories of Nepal from 2005 to 2010. Identification and antimicrobial susceptibility testing of the Salmonella isolates was done following standard microbiologic techniques. Isolates received from other laboratories were further confirmed and verified at the National Public Health Laboratory (NPHL). A total of 8342 Salmonella isolates were reported during 6 years period of which 5416 (64.92%) were Salmonella typhi, 2690 (32.25%) were Salmonella paratyphi and 236 (2.83%) were other Salmonella spp. The rate of infection was common among 15 to 30 years age group and followed by below 15 years age group in 2007 to 2010. The maximum numbers of isolates were reported during April to June during 2005 to 2007 and in year 2008 and 2010 during July to September, but in 2009 during October to December. 80 to 93% of the Salmonella isolates were resistant to Nalidixic Acid (NA). This study also revealed increase in Multidrug Resistant (MDR) Salmonella cases (2 to 8%) over the 6 years period. The study shows the prevalence of Salmonella typhi over other Salmonella spp., and thus, indicates it to be the major causative agent of enteric fever. Although, resistance to most antibiotics is in highly increasing trend, resistance to ceftriaxone was least. Thus, sensitivity pattern of causative organism must be sought before appropriate therapy to prevent further emergence of drug resistance.