title: Molecular evaluation of drug resistance in clinical isolates of Salmonella enterica serovar Typhi from Pakistan.
abstract: BACKGROUND
  This study aimed to determine the drug susceptibility patterns and genetic elements related to drug resistance in isolates of Salmonella enterica serovar Typhi (S. Typhi) from the Faisalabad region of Pakistan.
  
  
  METHODS
  The drug resistance status of 80 isolates were evaluated by determining antimicrobial susceptibility, MICs, drug resistance genes involved, and the presence of integrons. Nalidixic acid resistance and reduced susceptibility to ciprofloxacin were also investigated by mutation screening of the gyrA, gyrB, parC, and parE genes.
  
  
  RESULTS
  Forty-seven (58.7%) isolates were multidrug resistant (MDR). Among the different resistance (R) types, the most commonly observed (13/80) was AmChStrTeSxtSmzTmp, which is the most frequent type observed in India and Pakistan. The most common drug resistant genes were blaTEM-1, cat, strA-strB, tetB, sul1, sul2, and dfrA7. Among the detected genes, only dfrA7 was found to be associated in the form of a single gene cassette within the class 1 integrons.
  
  
  CONCLUSIONS
  MIC determination of currently used drugs revealed fourth-generation gatifloxacin as an effective drug against multidrug-resistant S. Typhi, but its clinical use is controversial. The Ser83→Phe substitution in gyrA was the predominant alteration in nalidixic acid-resistant isolates, exhibiting reduced susceptibility and increased MICs against ciprofloxacin. No mutations in gyrB, parC, or parE were detected in any isolate.
authors: National Institute for Biotechnology and Genetic Engineering, Faisalabad, Pakistan. amnanoor_786@yahoo.com.
authors: Amna
authors: A
authors: Afzal
authors: Yasra
authors: Y
authors: Sarwar
authors: Aamir
authors: A
authors: Ali
authors: Abbas
authors: A
authors: Maqbool
authors: Muhammad
authors: M
authors: Salman
authors: Muhammad Asif
authors: MA
authors: Habeeb
authors: Abdul
authors: A
authors: Haque
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004252:DNA Mutational Analysis; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D024881:Drug Resistance, Bacterial; D005798:Genes, Bacterial; D006801:Humans; D008826:Microbial Sensitivity Tests; D010154:Pakistan; D012485:Salmonella typhi / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D014435:Typhoid Fever / Q000382:microbiology*
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial