AUTHOR=Chatterjee Somdatta , Datta Saswati , Roy Subhasree , Ramanan Lavanya , Saha Anindya , Viswanathan Rajlakshmi , Som Tapas , Basu Sulagna 

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

JOURNAL=Frontiers in Microbiology

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2016.01126

DOI=10.3389/fmicb.2016.01126

ISSN=1664-302X

ABSTRACT=<p>Carbapenem-resistant determinants and their surrounding genetic structure were studied in <italic>Acinetobacter</italic> spp. from neonatal sepsis cases collected over 7 years at a tertiary care hospital. <italic>Acinetobacter</italic> spp. (<italic>n</italic> = 68) were identified by ARDRA followed by susceptibility tests. Oxacillinases, metallo-β-lactamases (MBLs), extended-spectrum β-lactamases and AmpCs, were detected phenotypically and/or by PCR followed by DNA sequencing. Transconjugants possessing the <italic>bla</italic><sub>NDM−1</sub>(New Delhi metallo-β-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. <italic>A. baumannii</italic> (72%) was the predominant species followed by <italic>A. calcoaceticus</italic> (10%), <italic>A. lwoffii</italic> (6%), <italic>A. nosocomialis</italic> (3%), <italic>A. junni</italic> (3%), <italic>A. variabilis</italic> (3%), <italic>A. haemolyticus</italic> (2%), and 14TU (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 <italic>A. baumannii</italic>. NDM-1 was the dominant MBL (22%) across different <italic>Acinetobacter</italic> spp. Isolates harboring NDM-1 also possessed <italic>bla</italic><sub>(VIM−2</sub>, <sub>PER−1</sub>, <sub>VEB−2, CTX−M−15)</sub>, <italic>armA, aac(6</italic>′<italic>)Ib, aac(6</italic>′<italic>)Ib-cr</italic> genes. <italic>bla</italic><sub>NDM−1</sub>was organized in a composite transposon between two copies of <italic>IS</italic>Aba125 in the isolates irrespective of the species. Further, OXA-23-like gene and OXA-58-like genes were linked with <italic>IS</italic>Aba1 and <italic>IS</italic>Aba3 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 (<italic>aadB, aadA2, aac4</italic>′), non-enzymatic chloramphenicol resistance gene (<italic>cmlA1g</italic>) and ADP-ribosylation genes (<italic>arr2, arr3</italic>). Outborn neonates had a significantly higher incidence of sepsis due to NDM-1 harboring isolates than their inborn counterparts. This study demonstrates the significance of both <italic>A. baumannii</italic> and other species of <italic>Acinetobacter</italic> in cases of neonatal sepsis over an extended period. Oxacillinases and <italic>bla</italic><sub>NDM−1</sub> are the major contributors to carbapenem resistance. The dissemination of the <italic>bla</italic><sub>NDM−1</sub> is likely linked to Tn125 in diverse clones of the isolates.</p>