Emergence of multidrug-resistant Salmonella Gloucester and Salmonella Typhimurium in Bangladesh

Infections due to non-typhoid Salmonella, resistant to antibiotics, have re cently emerged as an important health problem worldwide. Antibiotic resista nce was studied by the disc-diffusion method among 3,876 (2.78%) non-typhoi d Salmonella isolates cultured from 139,279 faecal samples in a diarrhoea t reatment centre in Dhaka, Bangladesh, during 1989-1996. Of 499 salmonellae isolated in 1989, serogroup C (1.12%) was the most common, followed by Salm onella Typhi (0.72%) and serogroup B (0.71%). Isolation rate of serogroup B increased significantly to 2.18% (p<0.01) in 1992 compared to 0.56% in 199 1, 2.86% in 1995, and 2.48% in 1996. Serotyping of 194 serogroup B isolates revealed Salmonella Typhimurium (52%) and Salmonella Gloucester (45%) as p redominant serotypes. Resistance to ampicillin (A), chloramphenicol (C), an d trimethoprim-sulphamethoxazole (Sxt) (R type-ACSxt) increased to 89-100% during 1992-1996 from 20-28% during 1989-1991 (p<0.01) among S. Typhimurium and S. Gloucester isolates. In 1993, 8-10% of the strains of both the sero types, resistant to ampicillin, chloramphenicol, and trimethoprim-sulphamet hoxazole, acquired resistance to ceftriaxone (Cr) (R type-ACSxtCr), which i ncreased to 85-92% in 1996 (p<0.01). All were susceptible to ciprofloxacin. A 157-kb conjugative plasmid transferred R type-ACSxt from both the seroty pes to Escherichia coli K-12. The findings of the study suggest the emergen ce of multidrug-resistant S. Gloucester and S. Typhimurium for the first ti me as a significant health problem in Bangladesh, and surveillance is essen tial to monitor the resistant non-typhoid Salmonella and identify its sourc es and modes of transmission.