Carbapenem Resistance in Acinetobacter baumannii and Other Acinetobacter spp. Causing Neonatal Sepsis: Focus on NDM-1 and Its Linkage to ISAba125

Carbapenem-resistant determinants and their surrounding genetic structure were studied in Acinetobacter spp. from neonatal sepsis cases collected over 7 years at a tertiary care hospital. Acinetobacter spp. (n = 68) were identified by ARDRA followed by susceptibility tests. Oxacillinases, metallo-beta-lactamases (MBLs), extended spectrum Hactamases and AmpCs, were detected phenotypically and/or by PCR followed by DNA sequencing. Transconjugants possessing the bla(NDM-1)(New Delhi metallo-beta-lactamase) underwent further analysis for plasmids, integrons and associated genes. Genetic environment of the carbapenemases were studied by PCR mapping and DNA sequencing. Multivariate logistic regression was used to identify risk factors for sepsis caused by NDM-1-harboring organisms. A. baurnannii (72%) was the predominant species followed by A. calcoaceticus (10%), A. Iwoffii (6%), A. nosocomialis (3%). A. junni (3%), A. variabilis (3%), A. haemolyticus (2%), and 1410 (2%). Fifty six percent of the isolates were meropenem-resistant. Oxacillinases present were OXA-23-like, OXA-58-like and OXA-51-like, predominately in A. baumannii. NDM-1 was the dominant MBL (22%) across different Acinetobacter spp. Isolates harboring NDM-1 also possessed bla((VIM-2,) (PER-1,) (VEB-2), (CTX-M-15)) armA, aac(6')lb, aac(6')lb-cr genes. bla(NDM_1) was organized in a composite transposon between two copies of /SAba125 in the isolates irrespective of the species. Further, OXA-23-like gene and OXA-58-like genes were linked with /SAba1 and /SAba3 respectively. Isolates were clonally diverse. Integrons were variable in sequence but not associated with carbapenem resistance. Most commonly found genes in the 5' and 3' conserved segment were aminoglycoside resistance genes (aadB, aadA2, aac4'), non-enzymatic chloramphenicol resistance gene (cmlA1g) and ADP-ribosylation genes (arr2, arr3). Outborn neonates had a significantly higher incidence of sepsis due to NDM-1 harboring isolates than their