Detection of NDM-1 and VIM Genes in Carbapenem-Resistant Klebsiella pneumoniae Isolates from a Tertiary Health-Care Center in Kathmandu, Nepal

Abstract

<b><i>Background:</i></b> <i>Klebsiella pneumoniae</i> is one of the leading causes of nosocomial infections. Carbapenems are used as the last resort for the treatment of multidrug resistant Gram-negative bacterial infections. In recent years, resistance to these lifesaving drugs has been increasingly reported due to the production of carbapenemase. The main objective of this study was to detect the carbapenem-resistant genes <i>bla</i>_NDM-1 and <i>bla</i>_VIM in <i>K. pneumoniae</i> isolated from different clinical specimens. <b><i>Methods:</i></b> A total of 585 clinical specimens (urine, pus, sputum, blood, catheter tips, and others) from human subjects attended at Annapurna Neurological Institute and Allied Sciences, Kathmandu were obtained in the period between July 2018 and January 2019. The specimens were isolated and identified for <i>K. pneumoniae</i>. All <i>K</i>. <i>pneumoniae</i> isolates were processed for antimicrobial susceptibility testing (AST) using the disk diffusion method. The isolates were further phenotypically confirmed for carbapenemase production by the modified Hodge test (MHT) using imipenem (10 μg) and meropenem (10 μg) discs. Thus, confirmed carbapenemase-producing isolates were further screened for the production of <i>bla</i>_NDM-1 and <i>bla</i>_VIM using conventional polymerase chain reaction (PCR). <b><i>Results:</i></b> Among the clinical isolates tested, culture positivity was 38.29% (224/585), and the prevalence of <i>K. pneumoniae</i> was 25.89% (58/224). On AST, <i>K. pneumoniae</i> exhibited resistance toward carbapenems including ertapenem, meropenem, and imipenem, while it showed the highest susceptibility rate against to tigecycline (93.1%; 54/58). Overall, AST detected 60.34% (35/58) carbapenem-resistant isolates, while the MHT phenotypically confirmed 51.72% (30/58) isolates as carbapenemase-producers and 48.28% (28/58) as carbapenemase nonproducers. On subsequent screening for resistant genes among carbapenemase-producers by PCR assay, 80% (24/30) and 3.33% (1/30) isolates were found to be positive for <i>bla</i>_NDM-1 and <i>bla</i>_VIM, respectively. In the same assay among 28 carbapenem nonproducing isolates, 9 (32.14%) isolates were positive for <i>bla</i>_NDM-1 gene while none of them were tested positive for <i>bla</i>_VIM gene. <b><i>Conclusions:</i></b> Molecular detection of resistant genes provides greater specificity and sensitivity than those with conventional techniques, thus aiding in accurate identification of antimicrobial resistance and clinical management of the disease.