title: Prevalence of faecal carriage of Enterobacteriaceae with NDM-1 carbapenemase at military hospitals in Pakistan, and evaluation of two chromogenic media.
abstract: OBJECTIVE
  To determine the prevalence and antimicrobial susceptibility of carbapenemase-producing Enterobacteriaceae among hospitalized patients and outpatients attending two military hospitals in Rawalpindi, Pakistan, and to compare the performance of two chromogenic culture media for the isolation of these organisms.
  
  
  METHODS
  Stool samples from 200 distinct patients were cultured on MacConkey agar and subsequently on two chromogenic media-Colorex KPC and a prototype chromogenic medium, ID Carba-designed for the isolation of carbapenemase-producing Enterobacteriaceae. All Gram-negative isolates growing on either chromogenic medium were investigated for carbapenemases by phenotypic and molecular methods. Producers were subjected to susceptibility testing with 40 antimicrobials by VITEK 2 or agar dilution.
  
  
  RESULTS
  In total, 64 NDM-1-positive isolates of Enterobacteriaceae, belonging to seven distinct species, were recovered from 37 (18.5%) of the stool samples. No other carbapenemase types were confirmed. Nineteen positive samples were identified among 70 from inpatients (prevalence 27.1%) and there were 18 positive samples among 130 from outpatients (prevalence 13.8%). Fifty-six isolates (87.5%) harbouring the NDM-1 enzyme were recovered on ID Carba compared with 41 isolates (64.1%) on Colorex KPC (P = 0.012). Multidrug resistance was prevalent, but no pan-resistant isolates were found, with most isolates susceptible in vitro to colistin (97%), mecillinam (95%), fosfomycin (94%), tigecycline (89%) and nitrofurantoin (78%).
  
  
  CONCLUSIONS
  This study shows a high prevalence of multidrug-resistant Enterobacteriaceae with the NDM-1 enzyme in Rawalpindi. The new chromogenic medium, ID Carba, was more sensitive than Colorex KPC and has potential as a screening medium for isolation of Enterobacteriaceae harbouring the NDM-1 enzyme.
authors.affiliation: Microbiology Department, Freeman Hospital, Newcastle upon Tyne NE7 7DN, UK. john.perry@nuth.nhs.uk
authors.forename: John D
authors.initials: JD
authors.lastname: Perry
authors.forename: Sakeenah Hussain
authors.initials: SH
authors.lastname: Naqvi
authors.forename: Irfan Ali
authors.initials: IA
authors.lastname: Mirza
authors.forename: Shehla Ambreen
authors.initials: SA
authors.lastname: Alizai
authors.forename: Aamir
authors.initials: A
authors.lastname: Hussain
authors.forename: Sandrine
authors.initials: S
authors.lastname: Ghirardi
authors.forename: Sylvain
authors.initials: S
authors.lastname: Orenga
authors.forename: Kathryn
authors.initials: K
authors.lastname: Wilkinson
authors.forename: Neil
authors.initials: N
authors.lastname: Woodford
authors.forename: Jiancheng
authors.initials: J
authors.lastname: Zhang
authors.forename: David M
authors.initials: DM
authors.lastname: Livermore
authors.forename: Shahid Ahmad
authors.initials: SA
authors.lastname: Abbasi
authors.forename: Muhammad W
authors.initials: MW
authors.lastname: Raza
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000378:metabolism*; D024901:Drug Resistance, Multiple, Bacterial; D004755:Enterobacteriaceae / Q000187:drug effects* / Q000201:enzymology / Q000254:growth & development / Q000302:isolation & purification; D004756:Enterobacteriaceae Infections / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology*; D005243:Feces / Q000382:microbiology*; D006772:Hospitals, Military; D006801:Humans; D008826:Microbial Sensitivity Tests; D010154:Pakistan / Q000453:epidemiology; D001618:beta-Lactamases / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D001618:beta-Lactamases; C552864:beta-lactamase NDM-1; C063912:carbapenemase