title: Changing trends in antimicrobial resistance of Salmonella enterica serovar typhi and salmonella enterica serovar paratyphi A in Chennai.
abstract: OBJECTIVE
  Chloramphenicol was considered the anti-microbial gold standard for typhoid treatment but, following the increasing worldwide frequency of antibiotic resistance, ciprofloxacin has been the mainstay of therapy since 1980. Recent studies have shown a shifting of susceptibility to conventional drugs like chloramphenicol, ampicillin and cotrimoxazole. The primary objective of the study was to evaluate the in vitro activity of chloramphenicol and other first-line drugs in comparison with cephalosporins and quinolones.
  
  
  METHODS
  Fifty isolates of Salmonella obtained from blood culture were subjected to serotyping at the Central Research Institute, Kasauli. Phage typing and biotyping was performed at the National Phage Typing Centre, New Delhi. Antibiotic sensitivity testing was carried out for 10 drugs by the Kirby-Bauer disc diffusion method and minimum inhibitory concentration by broth microdilution for nalidixic acid, chloramphenicol, ciprofloxacin, ceftriaxone, cefixime and ofloxacin. Multi-drug-resistant (MDR) strains were checked for plasmid.
  
  
  RESULTS
  In the present study, 70 and 30% of the isolates were Salmonella enterica serovar typhi and paratyphi A, respectively. They were highly sensitive to chloramphenicol (86%), ampicillin (84%) and cotrimoxazole (88%). Highest sensitivity was seen for cephalosporins, followed by quinolones. Seventeen/21 (81%) and 100% of the Salmonella enterica serovar typhi strains belonged to E1 phage type and biotype 1, respectively. Antibiogram showed 2% of the strains to be sensitive to all the drugs tested and 12% were MDR and showed the presence of plasmids.
  
  
  CONCLUSIONS
  The study indicates reemergence of chloramphenicol-susceptible Salmonella enterica serovar typhi and paratyphi A isolates, a significant decline in MDR strains and high resistance to nalidixic acid. E1 phage type and biotype 1 are found to be most prevalent in Chennai, India.
authors.affiliation: Department of Microbiology, Dr ALM Post Graduate Institute of Basic Medical Sciences, University of Madras, Chenai, India. padma.abpkn@gmail.com
authors.forename: Padma
authors.initials: P
authors.lastname: Krishnan
authors.forename: M
authors.initials: M
authors.lastname: Stalin
authors.forename: S
authors.initials: S
authors.lastname: Balasubramanian
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D015373:Bacterial Typing Techniques; D001434:Bacteriophage Typing; D001769:Blood / Q000382:microbiology; D024881:Drug Resistance, Bacterial; D006801:Humans; D007194:India; D008826:Microbial Sensitivity Tests / Q000379:methods; D010284:Paratyphoid Fever / Q000382:microbiology; D010957:Plasmids / Q000032:analysis; D012482:Salmonella paratyphi A / Q000187:drug effects* / Q000302:isolation & purification; D012485:Salmonella typhi / Q000187:drug effects* / Q000302:isolation & purification; D012703:Serotyping; D014435:Typhoid Fever / Q000382:microbiology
chemical_list: D000900:Anti-Bacterial Agents