Phenotypic tests and Molecular detection of blaOXA-48 and blaNDM-1 genes among carbapenem-resistant Enterobacteriaceae isolated from allograft liver recipients

Background: Infections with carbapenem resistant Enterobacteriaceae (CRE) cause significant morbidity and mortality in Liver transplant recipients. Accurate detection of CRE is the first step in combating this problem. Objectives: to study the distribution of pathogens and CRE causing infections in liver allograft recipients with special reference to the impact of pre-operative intestinal colonization with CRE on post-operative infections, and to investigate the phenotypic tests and to detect the frequency of blaOXA48 and blaNDM-1 genes by duplex PCR. Methodology: A total of 23 CRE isolates were investigated for carbapenemase production by phenotypic methods such as the modified Hodge test (MHT), douple disc synergy test (DDST), E test and Rabidec Carba NP (RCNP) test. Production of blaOXA 48 and blaNDM-1genes was investigated by duplex PCR. Results: Frequency of CRE that harbored blaOXA-48 and blaNDM-1 genes, as obtained by PCR, was 47.8% for blaOXA-48, 20.1% for blaNDM-1 and 8.7% of CRE isolates co-produced the two genes. RCNP test exhibited Sensitivity of 90.9% and 100% versus 81.1% and 66.6% sensitivities by MHT in detecting blaOXA-48 and blaNDM1genes respectively. E-test had a much higher sensitivity in identifying NDM-1 carpabenemase compared to DDST (100% versus 66.6% respectively).Conclusion: RCNP test can be done instead of MHT in detecting CRE, as it is more accurate, rapid and having excellent sensitivity in detecting blaNDM-1 and blaOXA-48 producing isolates. E-test is more reliable than DDST and can be a valid alternative to PCR in detecting MBL especially NDM-1 type.