title: Frequency of isolation of various subtypes and antimicrobial resistance of Shigella from urban slums of Karachi, Pakistan.
abstract: OBJECTIVE
  Shigellosis remains a major public health problem in developing countries. Antimicrobial resistance has complicated the empirical treatment. Knowledge of serotypes is crucial in vaccine development, as cross-protection between various serotypes is limited. Therefore we conducted a prospective study to determine the frequency of isolation of Shigella serotypes and antimicrobial resistance.
  
  
  METHODS
  Stool samples from 8155 individuals, collected through a surveillance study conducted in four slums of Karachi from January 2002 to March 2004, were cultured.
  
  
  RESULTS
  Shigella was isolated in 394 (4.8%) of 8155 patients presenting with diarrhea. Two hundred and forty-two (62%) isolates were Shigella flexneri, 72 (18%) were Shigella sonnei, 43 (11%) were Shigella boydii, and 37 (9%) were Shigella dysenteriae. Thirteen S. flexneri serotypes were identified, of which the most frequent were 2a (38), 6 (37), and 1b (25), followed by 2b (23). Only 22 (5.6%) Shigella isolates were found to be pan-susceptible. Large proportions of isolates were resistant to co-trimoxazole (89% S. flexneri, 81% S. dysenteriae, 80% S. sonnei, and 56% S. boydii) and ampicillin (87% S. flexneri, 68% S. dysenteriae, 35% S. boydii, and 4% S. sonnei).
  
  
  CONCLUSIONS
  Concurrent circulation of multiple strains with high resistance is worrying and mandates surveillance at the national level to facilitate the control of shigellosis.
authors.affiliation: Department of Pathology and Microbiology, Aga Khan University Hospitals, Stadium Road, PO Box 3500, Karachi 74800, Pakistan. afia.zafar@aku.edu
authors.forename: Afia
authors.initials: A
authors.lastname: Zafar
authors.forename: Rumina
authors.initials: R
authors.lastname: Hasan
authors.forename: Shaikh Qamaruddin
authors.initials: SQ
authors.lastname: Nizami
authors.forename: Lorenz
authors.initials: L
authors.lastname: von Seidlein
authors.forename: Sajid
authors.initials: S
authors.lastname: Soofi
authors.forename: Tanwir
authors.initials: T
authors.lastname: Ahsan
authors.forename: Saeeda
authors.initials: S
authors.lastname: Chandio
authors.forename: Atif
authors.initials: A
authors.lastname: Habib
authors.forename: Naveed
authors.initials: N
authors.lastname: Bhutto
authors.forename: Fahad J
authors.initials: FJ
authors.lastname: Siddiqui
authors.forename: Arjumand
authors.initials: A
authors.lastname: Rizvi
authors.forename: John D
authors.initials: JD
authors.lastname: Clemens
authors.forename: Zulfiqar A
authors.initials: ZA
authors.lastname: Bhutta
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D024881:Drug Resistance, Bacterial; D004405:Dysentery, Bacillary / Q000453:epidemiology* / Q000382:microbiology; D005243:Feces / Q000382:microbiology; D006801:Humans; D008826:Microbial Sensitivity Tests; D010154:Pakistan / Q000453:epidemiology; D012703:Serotyping; D012760:Shigella / Q000145:classification / Q000187:drug effects / Q000302:isolation & purification; D013045:Species Specificity; D014505:Urban Population
chemical_list: D000900:Anti-Bacterial Agents