title: Changing trends in the prevalence of Shigella species: emergence of multi-drug resistant Shigella sonnei biotype g in Bangladesh.
abstract: Shigellosis, caused by Shigella species, is a major public health problem in Bangladesh. To determine the prevalence and distribution of different Shigella species, we analyzed 10,827 Shigella isolates from patients between 2001 and 2011. S. flexneri was the predominant species isolated throughout the period. However, the prevalence of S. flexneri decreased from 65.7% in 2001 to 47% in 2011, whereas the prevalence of S. sonnei increased from 7.2% in 2001 to 25% in 2011. S. boydii and S. dysenteriae accounted for 17.3% and 7.7% of the isolates respectively throughout the period. Of 200 randomly selected S. sonnei isolates for extensive characterization, biotype g strains were predominant (95%) followed by biotype a (5%). Resistance to commonly used antibiotics including trimethoprim-sulfamethoxazole, nalidixic acid, ciprofloxacin, mecillinam and ampicillin was 89.5%, 86.5%, 17%, 10.5%, and 9.5%, respectively. All isolates were susceptible to ceftriaxone, cefotaxime, ceftazidime and imipenem. Ninety-eight percent of the strains had integrons belonging to class 1, 2 or both. The class 1 integron contained only dfrA5 gene, whereas among class 2 integron, 16% contained dhfrAI-sat1-aadA1-orfX gene cassettes and 84% harbored dhfrA1-sat2 gene cassettes. Plasmids of ∼5, ∼1.8 and ∼1.4 MDa in size were found in 92% of the strains, whereas only 33% of the strains carried the 120 MDa plasmid. PFGE analysis showed that strains having different integron patterns belonged to different clusters. These results show a changing trend in the prevalence of Shigella species with the emergence of multidrug resistant S. sonnei. Although S. flexneri continues to be the predominant species albeit with reduced prevalence, S. sonnei has emerged as the second most prevalent species replacing the earlier dominance by S. boydii and S. dysenteriae in Bangladesh.
authors.affiliation: Centre for Food and Water Borne Diseases, International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh.
authors.forename: Abu I M S
authors.initials: AI
authors.lastname: Ud-Din
authors.affiliation: Centre for Food and Water Borne Diseases, International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh.
authors.forename: Syeda U H
authors.initials: SU
authors.lastname: Wahid
authors.affiliation: Centre for Food and Water Borne Diseases, International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh.
authors.forename: Hasan A
authors.initials: HA
authors.lastname: Latif
authors.affiliation: Centre for Food and Water Borne Diseases, International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Shahnaij
authors.affiliation: Centre for Food and Water Borne Diseases, International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh.
authors.forename: Mahmuda
authors.initials: M
authors.lastname: Akter
authors.affiliation: Centre for Food and Water Borne Diseases, International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh.
authors.forename: Ishrat J
authors.initials: IJ
authors.lastname: Azmi
authors.affiliation: Centre for Food and Water Borne Diseases, International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh.
authors.forename: Trisheeta N
authors.initials: TN
authors.lastname: Hasan
authors.affiliation: Centre for Food and Water Borne Diseases, International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh.
authors.forename: Dilruba
authors.initials: D
authors.lastname: Ahmed
authors.affiliation: Centre for Food and Water Borne Diseases, International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh.
authors.forename: Mohammad A
authors.initials: MA
authors.lastname: Hossain
authors.affiliation: Centre for Food and Water Borne Diseases, International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh.
authors.forename: Abu S G
authors.initials: AS
authors.lastname: Faruque
authors.affiliation: Centre for Food and Water Borne Diseases, International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh.
authors.forename: Shah M
authors.initials: SM
authors.lastname: Faruque
authors.affiliation: Centre for Food and Water Borne Diseases, International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka, Bangladesh.
authors.forename: Kaisar A
authors.initials: KA
authors.lastname: Talukder
mesh_terms: D000560:Amdinocillin / Q000627:therapeutic use; D000667:Ampicillin / Q000627:therapeutic use; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D001459:Bangladesh / Q000453:epidemiology; D002939:Ciprofloxacin; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics; D004405:Dysentery, Bacillary / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology; D006801:Humans; D032023:Integrons / Q000235:genetics; D009268:Nalidixic Acid / Q000627:therapeutic use; D010802:Phylogeny; D015995:Prevalence; D012764:Shigella sonnei / Q000187:drug effects* / Q000235:genetics / Q000472:pathogenicity; D015662:Trimethoprim, Sulfamethoxazole Drug Combination / Q000627:therapeutic use
chemical_list: D000900:Anti-Bacterial Agents; D009268:Nalidixic Acid; D002939:Ciprofloxacin; D000667:Ampicillin; D015662:Trimethoprim, Sulfamethoxazole Drug Combination; D000560:Amdinocillin