Shigella isolates of Nepal: changes in the incidence of shigella subgroups and trends of antimicrobial susceptibility pattern

Abstract

Objectives: Shigellosis is an important cause of bloody diarrhoea in all age groups, especially in children. A retrospective study was done to analyse the pattern of shigella isolates and the antimicrobial susceptibility trend of these shigella isolated at different hospitals of Nepal from Jan, 2003- Dec, 2005.

Materials and methods: A total of 118 Shigella species isolated at nine different hospital laboratories of Nepal were reported to National Public Health Laboratory during January, 2003- December 2005 .The isolates were tested for the confirmation of identification and antimicrobial susceptibility pattern by standard bacteriological techniques.

Results: Of the 118 Shigella isolates reported, Shigella flexneri 51 (43.22%) was the predominant of the four species followed by Shigella dysenteriae 49(41.52 %) , Shigella boydii (7.62%) and Shigella sonnei (7.62%).But the yearly distribution of the Shigella isolates in 2003 and 2004 showed that Shigella dysenteriae was the most common of the four species. In 2005, a shift in the species was noted as Sh flexneri replaced Sh dysenteriae and became the most prevalent species. The percentage of Shigella dysenteriae type-1 among all Shigella dysenteriae were 66.66 % in 2003, 44.44 % in 2004 and 60 % in 2005. Individual or multiple resistances to Ampicillin, Nalidixic acid, and/or Cotrimoxazole was seen in all the four species of Shigella. 33% of the total Shigella isolates reported were multi drug resistant (showing resistance to 3 or more antibiotics at a time). Shigella dysenteriae type-1(Sd 1) isolates resistant to ciprofloxacin were also encountered in the present study .Of the total 25 Shigella dysenteriae type 1 isolates reported, 18(72%) were ciprofloxacin resistant . All the Shigella isolates were however sensitive to Ceftriaxone and Azithromycin.

Conclusion: Distribution of different species of Shigella and their antibiotic susceptibility profile may vary from one geographical location to another and may also change with time. Systematic monitoring of the species and serotypes of Shigellae and their antimicrobial susceptibility can help to guide therapy and reveal periodic epidemics due to Sd 1, which may have acquired resistance to antibiotics that have previously been effective. Key words: Dysentery, Shigella, Shigella dysenteriae type-1, Antimicrobial resistance.