title: A Pilot Study on Carbapenemase Detection: Do We See the Same Level of Agreement as with the CLSI Observations.
abstract: BACKGROUND
  Rapid identification of carbapenemase producing organisms is of great importance for timely detection, treatment and implementation of control measures to prevent the spread. The Modified Hodge Test (MHT) and Carba NP test is recommended by CLSI for the detection of carbapenemases in Enterobacteriaceae. However, MHT may give false positive results or fail to detect metallo β-lactamases (MBLs). In the US, MHT is the most widely used test for detection of carbapenemases and has been found to have a sensitivity and specificity of >90% for bla KPC producers. However, in India, the prevalence of bla NDM is higher than bla KPC producers.
  
  
  OBJECTIVE
  To evaluate the usefulness of CarbaNP in an Indian setting.
  
  
  METHODS
  A total of 260 isolates of carbapenem resistant E.coli (n=57), Klebsiella spp. (n=85), Pseudomonas aeruginosa (n=60), and Acinetobacter baumannii (58) isolated from clinical specimens between 2012-2014 at the Christian Medical College, Vellore were included in the study. All the carbapenem resistant isolates were subjected to CarbaNP, MHT and multiplex PCR for detection of carbapenemase genes.
  
  
  RESULTS
  CarbaNP was found to be positive in 88% (n=50/57), 81% (n=69/51), 38% (n=23/60) and 81% (n=47/58) for E.coli, Klebsiella spp., P. aeruginosa, and A. baumannii respectively. While in MHT it showed, 89% (n=51/57) and 81 % (n=69/85) for E.coli and Klebsiella spp. respectively. In P.aeruginosa, synergy testing of imipenem plus cloxacillin showed that, 65% of CarbaNP negatives were ampC producers. Overall, the sensitivity and specificity of CarbaNP was found to be 94% and 100 for bla NDM; 77% and 100 % for bla OXA-48 like producers and 81% and 100% for CarbAcinetoNP respectively.
  
  
  CONCLUSIONS
  This observation was more than what was reported in CLSI guidelines. Therefore, it is advisable to evaluate an assay for better laboratory diagnosis at respective regions.
authors.affiliation: Research Associate, Department of Clinical Microbiology, Christian Medical College , Vellore, India .
authors.forename: Agila Kumari
authors.initials: AK
authors.lastname: Pragasam
authors.affiliation: Professor, Department of Clinical Microbiology, Christian Medical College , Vellore, India .
authors.forename: Rani Diana
authors.initials: RD
authors.lastname: Sahni
authors.affiliation: Professor, Department of Clinical Microbiology, Christian Medical College , Vellore, India .
authors.forename: Shalini
authors.initials: S
authors.lastname: Anandan
authors.affiliation: Registrar, Department of Clinical Microbiology, Christian Medical College , Vellore, India .
authors.forename: Archa
authors.initials: A
authors.lastname: Sharma
authors.affiliation: Research Associate, Department of Clinical Microbiology, Christian Medical College , Vellore, India .
authors.forename: Radha
authors.initials: R
authors.lastname: Gopi
authors.affiliation: Research Associate, Department of Clinical Microbiology, Christian Medical College , Vellore, India .
authors.forename: Noorjahan
authors.initials: N
authors.lastname: Hadibasha
authors.affiliation: Research Associate, Department of Clinical Microbiology, Christian Medical College , Vellore, India .
authors.forename: Priya
authors.initials: P
authors.lastname: Gunasekaran
authors.affiliation: Professor & Head, Department of Clinical Microbiology, Christian Medical College , Vellore, India .
authors.forename: Balaji
authors.initials: B
authors.lastname: Veeraraghavan
keywords: CarbaNP; Class D Oxacillinases; MHT; Metallo beta lactamases