Outcomes in Oxacillinases β-Lactamases (OXA-48) and New Delhi Metallo-β-Lactamase (NDM-1)-Producing, Carbapenem-Resistant Klebsiella Pneumoniae Isolates Obtained From Bloodstream Infections

Abstract

BACKGROUND: Carbapenemase-producing Klebsiella pneumoniae (CRKP) has become a menace in several intensive care units, which needs to be controlled immediately after being reported by a laboratory. Detection in the laboratory is usually done using phenotypic methods and it is not known whether knowledge of these genes helps in individual patient management. This study aimed to compare the outcomes of oxacillinases β-lactamases (OXA-48) and New Delhi metallo-β-lactamase (NDM-1)-producing CRKP isolates, the two most common carbapenemases reported from India, obtained from patients with bloodstream infections in an ICU in a tertiary care center in North India and to compare the different laboratory methods for their detection. MATERIALS AND METHODS: Klebsiella pneumoniae isolates obtained from the blood culture of patients admitted to various ICUs were subjected to conventional polymerase chain reaction (PCRs) for blaNDM and blaOXA48-like genes. Those positive for any of the genes were tested by the modified carbapenem inactivation method (mCIM) and if found positive were also subjected to ethylenediamine tetraacetic acid (EDTA)-modified carbapenem inactivation method (eCIM). Antibiotic susceptibility tests (AST) were performed and clinical data were recorded. RESULTS: A total of 49 isolates were positive for one or more carbapenemase genes (30 {61.2%} for blaNDM gene only, 13 {26.5%)} for blaOXA48-like gene only, and six {12.2%} for both). The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of mCIM were found to be 77.6%, 100%, 100%, and 78.9%, respectively. Statistically significant differences were found in the AST pattern between the isolates with two genes. Increased MIC levels of colistin were observed, though they lay in the sensitive range. Mortality occurred in all six patients who were infected with CRKP harboring both the genes though no significant difference was observed in NDM and OXA-48 producing CRKP isolates. CONCLUSION: Surveillance of carbapenemase genes in a hospital setting is essential. The possible reasons for the low diagnostic accuracy of mCIM and differences in AST patterns are discussed.