Utility of Carba NP test (Inhouse/RAPIDEC Commercial Kit) in the Identification of Carbapenemase Producing Clinical Isolates in a Tertiary Care Hospital

Abstract

Introduction: Carbapenems are the drugs of choice for the treatment of many multidrug resistant hospital acquired infections. Resistance to carbapenems also is not uncommon and is increasingly being reported now-a-days. Though various tests like modified hodge test are available for the detection of carbapenemases, they lack sensitivity and specificity. Recently, the Carba NP test has been introduced for carbapenemase detection which has been approved and included in CLSI guidelines. Aim: To identify the prevalence of carbapenemase producing isolates and the utility of Carba NP in house as well as commercial RAPIDEC Carba NP test in the identification of these carbapenemases. Materials and Methods: All the carbapenem resistant organisms isolated during the study period from July 2018 to December 2018 were included in the study. A total of 91 isolates were identified during the study period which were further tested for carbapenemase production by both in House Carba NP test as well as commercially available RAPIDEC Carba NP (Biomerieux) as per the existing protocols. Twenty five carbapenem sensitive isolates were also tested. Klebsiella pneumoniae BAA ATCC1705 and BAA ATCC-1706 were used as controls. Results: Out of 91, carbapenem resistant strains tested, 72 were identified as carbapenemase producers. Out of them, Klebsiella pneumonia accounted for 59.7% of the total carbapenemase producing organisms followed by Pseudomonas aeruginosa (25%) and E.coli (6.9%) followed by Acinetobacter and Enterobacter which constituted less than 5%. Among enterobacteriaceae, 43 out of 59 carbapenem resistant Klebsiella were carbapenemase producers whereas all the 5 carbapenem resistant E.coli were positive for Carba NP test. Among Pseudomonas 18 out of 21 were carbapenemase producers. All the positive isolates by in-house Carba NP test were also positive by commercial RAPIDEC test and vice-versa and none of the 25 carbapenem sensitive strains tested were positive for Carba NP test by either method indicating 100% correlation between the two methods studied. Conclusion: Carba NP in house as well as commercial RAPIDEC Carba NP test were equally effective in the identification of the carbapenemase producing gram negative bacilli. Wide adaptability of these tests by various laboratories will help in the early identification of these potentially spreading carbapenemase producers, which in association with appropriate treatment and infection control practices will prevent the emergence of these strains and will decrease the mortality and morbidity.

Keywords

• enterobacteriaceae
• klebsiella pneumonia
• multidrug resistance
• pseudomonas aeruginosa