title: Antibiotic resistance among Salmonella enterica serovars Typhi and Paratyphi A in Pakistan (2001-2006).
abstract: OBJECTIVE
  To compare antimicrobial resistance in S. Typhi and S. Paratyphi A isolates from Pakistan.
  
  
  METHODS
  Blood samples were collected through > 175 laboratory collection points in major cities and towns across the country. The study included 3,671 S. Typhi and 1,475 S. Paratyphi A isolates (2001-2006). Multidrug resistance (MDR) was defined as resistance to first-line agents co-trimoxazole, chloramphenicol and ampicillin.
  
  
  RESULTS
  In total, 79.3% S. Typhi and 59.9% S. Paratyphi A were isolated from patients under 15 years of age. During the study period, the MDR rate increased in S. Typhi (34.2 to 48.5% p<0.001). Quinolone resistance (MIC> 1 microg/ml) increased in both S. Typhi (1.6 to 64.1% p<0.001) and S. Paratyphi A (0 to 47% p<0.001). The increase in the proportion of strains showing high level quinolone resistance (MIC > 4 microg/ml) was greater in S. Paratyphi A when compared to S. Typhi. Resistance to first-line drugs was higher in those <15 years of age whereas quinolone resistance was higher in older patients.
  
  
  CONCLUSIONS
  Differences between S. Typhi and S. Paratyphi A, in terms of evolution of resistance to first-line agents and to quinolones, are evident in this population. The rapid increase in quinolone resistance in S. Paratyphi A when compared to S. Typhi is concerning and requires further study.
authors.affiliation: Department of Pathology & Microbiology, Aga Khan University Hospitals, Karachi 74800, Pakistan. rumina.hasan@aku.edu
authors.forename: Rumina
authors.initials: R
authors.lastname: Hasan
authors.forename: Afia
authors.initials: A
authors.lastname: Zafar
authors.forename: Zohair
authors.initials: Z
authors.lastname: Abbas
authors.forename: Vikram
authors.initials: V
authors.lastname: Mahraj
authors.forename: Faisal
authors.initials: F
authors.lastname: Malik
authors.forename: Anita
authors.initials: A
authors.lastname: Zaidi
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D024901:Drug Resistance, Multiple, Bacterial; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D008297:Male; D008826:Microbial Sensitivity Tests; D010154:Pakistan / Q000453:epidemiology; D012482:Salmonella paratyphi A / Q000187:drug effects* / Q000302:isolation & purification; D012485:Salmonella typhi / Q000187:drug effects* / Q000302:isolation & purification; D014435:Typhoid Fever / Q000453:epidemiology / Q000382:microbiology*