Mutations Decreasing Intrinsic beta-Lactam Resistance Are Linked to Cell Division in the Nosocomial Pathogen Acinetobacter baumannii

• Type of Material: Article
• Authors: Daniel Knight, Veterans Affairs Medical Center; Daniela D. Dimitrova, Emory University; Susan D. Rudin, Louis Stokes VA Medical Center; Robert A. Bonomo, Louis Stokes VA Medical Center; Philip Rather, Emory University
• Language: English
• Date: 2016-06-01
• Publisher: American Society for Microbiology
• Publication Version: Final Published Version
• Copyright Statement: © 2016, American Society for Microbiology. All Rights Reserved.
• Final Published Version (URL): http://dx.doi.org/10.1128/AAC.00361-16
• Title of Journal or Parent Work: Antimicrobial Agents and Chemotherapy
• ISSN: 0066-4804
• Volume: 60
• Issue: 6
• Start Page: 3751
• End Page: 3758
• Grant/Funding Information: This work was supported by grant R01AI72219 from the National Institutes of Health to P.N.R. and R.A.B. P.N.R. is also supported by grants from the Merit Review program and by a Research Career Scientist Award, both from the Department of Veterans Affairs.; Research reported in this publication was also supported in part by the National Institute of Allergy and Infectious Diseases of the National Institutes of Health (grants R01AI100560 and R01AI063517 to R.A.B.).; This study was also supported in part by funds and/or facilities provided by the Cleveland Department of Veterans Affairs (grant 1I01BX001974 to R.A.B.) and by the Biomedical Laboratory Research & Development Service of the VA Office of Research and Development and the Geriatric Research Education and Clinical Center (grant VISN 10 to R.A.B.).
• Keywords: Life Sciences & Biomedicine; CLINICAL STRAINS; ESCHERICHIA-COLI; CEPHALOSPORINASE; NO ESKAPE; WALL; Microbiology; FTSZ; INDUCED LYSIS; GENE; EXPRESSION; Science & Technology; Pharmacology & Pharmacy; AMPC
• Research Categories: Health Sciences, Immunology; Biology, Microbiology

Abstract

Transposon mutagenesis was used to identify novel determinants of intrinsic β-lactam resistance in Acinetobacter baumannii An EZ-Tn5 transposon insertion in a gene corresponding to the A1S_0225 sequence resulted in a 4-fold decrease in resistance to ampicillin, cefotaxime, imipenem, and ceftriaxone but did not alter resistance to other classes of antibiotics. Based on this phenotype, the gene was designated blhA (β-lactam hypersusceptibility). The blhA::EZ-Tn5 mutation conferred a similar phenotype in A. baumannii strain ATCC 17978. The wild-type blhA gene complemented the blhA::EZTn5 insertion and restored β-lactam resistance levels back to wild-type levels. The blhA mutation also increased β-lactam susceptibility in an adeB adeJ double mutant, indicating that the blhA mutation acted independently of these efflux systems to mediate susceptibility. In addition, mRNA levels for the blaOXA and blaADC β-lactamase genes were not altered by the blhA mutation. The blhA mutation resulted in a prominent cell division and morphological defect, with cells exhibiting a highly elongated phenotype, combined with large bulges in some cells. The blhA gene is unique to Acinetobacter and likely represents a novel gene involved in cell division. Three additional mutations, in zipA, zapA, and ftsK, each of which encode predicted cell division proteins, also conferred increased β-lactam susceptibility, indicating a common link between cell division and intrinsic β-lactam resistance in A. baumannii.