title: Detection of ISAba1 in association with a novel allelic variant of the β-lactamase ADC-82 and class D β-lactamase genes mediating carbapenem resistance among the clinical isolates of MDR A. baumannii.
abstract: OBJECTIVE
  The objective of the present study is to investigate the diverse resistance determinants, their association with insertion sequence mobile elements and predilection of a particular clone for such associations in Acinetobacter baumannii.
  
  
  METHODS
  Fifty-four consecutive isolates collected during 2011-2012 from a tertiary care hospital were subjected to susceptibility testing followed by PCR screening of commonly reported β-lactamases and 16S rRNA methyltransferase encoding genes. The integrity of resistance-nodulation-cell division efflux pump-related genes in their respective operons was also investigated.
  
  
  RESULTS
  β-Lactamase genes such as blaADC (100 %), blaOXA-23 (81 %), blaPER-1 (81 %), blaIMP-1 (31 %) and blaNDM-1 (15 %) were found to be present more frequently while blaVIM-2 and blaOXA-24 were not observed in our study population. ISAba1 was associated only with blaOXA-51-like like (30 %), blaOXA-23-like (55 %) and blaADC-like (33 %). armA was found in 87 % of isolates and ISAba1 linked with one novel variant of ADC, namely blaADC-82, which was identified to have 15 nucleotide differences with blaADC-79, and this finding is of much significance. In many isolates, efflux pump genes were not intact, resulting in severely altered effluxing functions. For the first time, we have identified ISAba1-mediated disruption of adeN among the isolates of ST 195B, which would have led to overexpression of AdeIJK efflux pump causing elevated resistance. Multilocus sequence typing revealed the predominance of CC 92B (IC-IIB) and CC 447B clonal complexes.
  
  
  CONCLUSIONS
  High incidence of IC-II clones, novel resistance determinants (ADC-82) and elevated resistance mediated by ISAba1 reported here will be of enormous importance while assessing the emergence of extremely resistant A. baumannii in India.
authors.affiliation: Department of Biotechnology, School of Life Sciences, Pondicherry University, Pondicherry, India.
authors.forename: Rajagopalan
authors.initials: R
authors.lastname: Saranathan
authors.affiliation: School of Biotechnology, Jawaharlal Nehru University, New Delhi, India.|Department of Biotechnology, School of Life Sciences, Pondicherry University, Pondicherry, India.
authors.forename: Rinki
authors.initials: R
authors.lastname: Kumari
authors.affiliation: Department of Microbiology, Mahatma Gandhi Medical College and Research Institute, Pondicherry, India.|Department of Clinical Microbiology, Pondicherry Institute of Medical Sciences (PIMS), Pondicherry, India.
authors.forename: Ramakrishnan
authors.initials: R
authors.lastname: Kalaivani
authors.affiliation: Department of Biotechnology, School of Life Sciences, Pondicherry University, Pondicherry, India.
authors.forename: Sah
authors.initials: S
authors.lastname: Suresh
authors.affiliation: Department of Biotechnology, School of Life Sciences, Pondicherry University, Pondicherry, India.
authors.forename: Anshu
authors.initials: A
authors.lastname: Rani
authors.affiliation: Department of Clinical Microbiology, Pondicherry Institute of Medical Sciences (PIMS), Pondicherry, India.
authors.forename: Shashikala
authors.initials: S
authors.lastname: Purty
authors.affiliation: Department of Biotechnology, School of Life Sciences, Pondicherry University, Pondicherry, India.
authors.forename: K
authors.initials: K
authors.lastname: Prashanth
mesh_terms: D040981:Acinetobacter baumannii / Q000201:enzymology / Q000235:genetics*; D000293:Adolescent; D000328:Adult; D000368:Aged; D000483:Alleles; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D015780:Carbapenems / Q000494:pharmacology; D002648:Child; D002675:Child, Preschool; D003001:Cloning, Molecular; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D005260:Female; D006760:Hospitalization; D006801:Humans; D007194:India; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008780:Methyltransferases / Q000235:genetics / Q000378:metabolism; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D058885:Multilocus Sequence Typing; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D055815:Young Adult; D001618:beta-Lactamases / Q000145:classification / Q000235:genetics*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D015780:Carbapenems; D012336:RNA, Ribosomal, 16S; D008780:Methyltransferases; D001618:beta-Lactamases