title: Reliability of Kirby-Bauer disk diffusion method for detecting meropenem resistance among non-fermenting gram-negative bacilli.
abstract: BACKGROUND
  Meropenem is empirically used as a last resort for the treatment of infections by non-fermenting gram-negative bacilli (NFGNB). Minimum inhibitory concentration (MIC) determined using agar or broth dilution methods is widely used for testing meropenem resistance. However, it is not possible in resource-poor settings.
  
  
  OBJECTIVE
  A prospective study was performed to evaluate the reliability of Kirby-Bauer disk diffusion (KBDD) method for detecting meropenem resistance among NFGNB.
  
  
  METHODS
  A total of 146 NFGNB consisting of 56 Acinetobacter baumannii, 24 Acinetobacter lwoffii, 48 Pseudomonas aeruginosa and 18 Pseudomonas spp. were included in the study. All the isolates were tested simultaneously by both KBDD method and agar dilution method.
  
  
  RESULTS
  Very major errors were not observed with A. baumannii, A. lwoffii and P. aeruginosa, while other Pseudomonas spp. showed a very major error rate of about 5.6%. The major error rates observed with A. baumannii, A. lwoffii, P. aeruginosa and Pseudomonas spp. were 1.8%, 0%, 2.1% and 28.6%, respectively. All the isolates showed a good correlation between zone diameters (KBDD method) and MICs (agar dilution method). The sensitivity and specificity of KBDD method for detecting meropenem resistance was above 90% for all the NFGNB except Pseudomonas spp.
  
  
  CONCLUSIONS
  The KBDD method can be reliably used for routine testing of meropenem resistance in A. baumannii, A. lwoffii and P. aeruginosa. However, further studies are needed before employing this technique for detecting meropenem resistance in Pseudomonas spp.
authors.affiliation: Department of Microbiology, Jawaharlal Institute of Postgraduate Medical Education and Research, Pondicherry, India. noyaljoseph@yahoo.com
authors.forename: Noyal M
authors.initials: NM
authors.lastname: Joseph
authors.forename: Sujatha
authors.initials: S
authors.lastname: Sistla
authors.forename: Tarun K
authors.initials: TK
authors.lastname: Dutta
authors.forename: Ashok S
authors.initials: AS
authors.lastname: Badhe
authors.forename: Desdemona
authors.initials: D
authors.lastname: Rasitha
authors.forename: Subhash C
authors.initials: SC
authors.lastname: Parija
mesh_terms: D000150:Acinetobacter / Q000187:drug effects*; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D003951:Diagnostic Errors / Q000706:statistics & numerical data; D052978:Disk Diffusion Antimicrobial Tests / Q000379:methods*; D006801:Humans; D000077731:Meropenem; D011446:Prospective Studies; D011549:Pseudomonas / Q000187:drug effects*; D013845:Thienamycins / Q000494:pharmacology*; D018440:beta-Lactam Resistance
chemical_list: D000900:Anti-Bacterial Agents; D013845:Thienamycins; D000077731:Meropenem