title: Transmission and strain variation of Shigella flexneri 4a after mass prophylaxis in a long-stay psychiatric centre.
abstract: Shigella flexneri 4a caused sustained outbreaks in a large long-stay psychiatric centre, Taiwan, 2001-2006. Trimethoprim-sulphamethoxazole (SXT) prophylaxis was administered in 2004. We recovered 108 S. flexneri 4a isolates from 83 symptomatic (including one caregiver) and 12 asymptomatic subjects (11 contacts, one caregiver). The isolates were classified into eight antibiogram types and 15 genotypes (six clusters) by using antimicrobial susceptibility testing and pulsed-field gel electrophoresis of NotI-digested DNA, respectively. These characteristics altered significantly after SXT prophylaxis (P < 0·05), with concomitant emergence of SXT-resistant isolates in two antibiogram types. P01 (n = 71), the predominant epidemic genotype, caused infection in two caregivers and five patients under their care; two P01 isolates were recovered from the same patient 6 months apart. These results indicate the importance of sustained person-to-person transmission of S. flexneri 4a by long-term convalescent, asymptomatic or caregiver carriers, and support the emergence of SXT-resistant strains following selective pressure by SXT prophylaxis.
authors.affiliation: Institute of Medical Sciences, Tzu Chi University, Hualien, Taiwan.
authors.forename: C F
authors.initials: CF
authors.lastname: Ko
authors.affiliation: Department of Medicine, Mackay Medical College, Taipei, Taiwan.
authors.forename: L Y
authors.initials: LY
authors.lastname: Wang
authors.affiliation: Institute of Microbiology, Immunology, and Biochemistry, Tzu Chi University, Hualien, Taiwan.
authors.forename: N T
authors.initials: NT
authors.lastname: Lin
authors.affiliation: The Central Region Laboratory, Centre of Research and Diagnostics, Centres for Disease Control, Taichung, Taiwan.
authors.forename: C S
authors.initials: CS
authors.lastname: Chiou
authors.affiliation: The Sixth Branch Office, Centres for Disease Control, Hualien, Taiwan.
authors.forename: H C
authors.initials: HC
authors.lastname: Yeh
authors.affiliation: Department of Orthopaedic Surgery, Yuli Veterans Hospital, Hualien, Taiwan.
authors.forename: J H
authors.initials: JH
authors.lastname: Renn
authors.affiliation: Department of Public Health, Tzu Chi University, Hualien, Taiwan.
authors.forename: Y S
authors.initials: YS
authors.lastname: Lee
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D019072:Antibiotic Prophylaxis; D004269:DNA, Bacterial / Q000235:genetics; D004196:Disease Outbreaks; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D004405:Dysentery, Bacillary / Q000453:epidemiology* / Q000382:microbiology / Q000517:prevention & control / Q000635:transmission; D016521:Electrophoresis, Gel, Pulsed-Field; D005838:Genotype; D006801:Humans; D008134:Long-Term Care; D008826:Microbial Sensitivity Tests; D017720:Molecular Epidemiology; D012763:Shigella flexneri / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification; D013624:Taiwan / Q000453:epidemiology; D015662:Trimethoprim, Sulfamethoxazole Drug Combination / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D015662:Trimethoprim, Sulfamethoxazole Drug Combination