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      Molecular Detection of Carbapenemase-Encoding Genes in Multidrug-Resistant Acinetobacter baumannii Clinical Isolates in South Africa

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          Abstract

          Introduction

          Carbapenem-resistant Acinetobacter baumannii has been responsible for an increasing number of hospital-acquired infections globally. The study investigated the prevalence of carbapenemase-encoding genes in clinical multidrug-resistant A. baumannii strains.

          Materials and Methods

          A total of 100 nonduplicate multidrug-resistant A. baumannii strains were cultured from clinical samples obtained from healthcare facilities in the O. R. Tambo district. The strains were confirmed by detecting the intrinsic bla OXA-51-like gene. Antimicrobial susceptibility testing was performed by VITEK ® 2 and autoSCAN-4 systems. The MIC of imipenem and meropenem was rechecked by E-test. Colistin MIC was confirmed by the broth microdilution method. Real-time PCR was performed to investigate the presence of carbapenemase-encoding genes.

          Results

          Most strains showed high resistance rates (>80%) to the antibiotics tested. Resistance to amikacin, tetracycline, and tigecycline were 50%, 64%, and 48%, respectively. All strains were fully susceptible to colistin. The bla OXA-51-like was detected in all strains whilst bla OXA-23-like, bla OXA-58-like, bla OXA-24-like, bla IMP-1, bla VIM, and bla NDM-1 were found in 70%, 8%, 5%, 4%, 3%, and 2% of strains, respectively. None of the tested strains harboured the genes bla SIM and bla AmpC. The coexistence of bla OXA-23-like, and bla IMP-1 or bla OXA-58-like was detected in 1% and 2% strains, respectively. A distinct feature of our findings was the coharbouring of the genes bla OXA-23-like, bla OXA-58-like, and bla IMP-1 in 2% strains, and this is the first report in the Eastern Cape Province, South Africa. The intI1 was carried in 80% of tested strains whilst IS Aba1/ bla OXA-51-like and IS Aba1/ bla OXA-23-like were detected in 15% and 40% of the strains, respectively. The detection of bla OXA-23-like, IS Aba1/ bla OXA-51-like, IS Aba1/ bla OXA-23-like, and bla OXA-23-like, bla OXA-58-like, and bla IMP-1 carbapenemases in strains had a significant effect on both imipenem and meropenem MICs.

          Conclusions

          Results showed a high level of oxacillinases producing A. baumannii circulating in our study setting, highlighting the need for local molecular surveillance to inform appropriate management and prevention strategies.

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          Most cited references39

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          OXA β-lactamases.

          The OXA β-lactamases were among the earliest β-lactamases detected; however, these molecular class D β-lactamases were originally relatively rare and always plasmid mediated. They had a substrate profile limited to the penicillins, but some became able to confer resistance to cephalosporins. From the 1980s onwards, isolates of Acinetobacter baumannii that were resistant to the carbapenems emerged, manifested by plasmid-encoded β-lactamases (OXA-23, OXA-40, and OXA-58) categorized as OXA enzymes because of their sequence similarity to earlier OXA β-lactamases. It was soon found that every A. baumannii strain possessed a chromosomally encoded OXA β-lactamase (OXA-51-like), some of which could confer resistance to carbapenems when the genetic environment around the gene promoted its expression. Similarly, Acinetobacter species closely related to A. baumannii also possessed their own chromosomally encoded OXA β-lactamases; some could be transferred to A. baumannii, and they formed the basis of transferable carbapenem resistance in this species. In some cases, the carbapenem-resistant OXA β-lactamases (OXA-48) have migrated into the Enterobacteriaceae and are becoming a significant cause of carbapenem resistance. The emergence of OXA enzymes that can confer resistance to carbapenems, particularly in A. baumannii, has transformed these β-lactamases from a minor hindrance into a major problem set to demote the clinical efficacy of the carbapenems.
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            The role of ISAba1 in expression of OXA carbapenemase genes in Acinetobacter baumannii.

            ISAba1 was found in all widespread clones of Acinetobacter baumannii in the United Kingdom. All isolates studied had a blaOXA-51-like carbapenemase gene; some also had blaOXA-23-like and/or blaOXA-58-like. Among isolates with blaOXA-51-like as sole carbapenemase gene, only those with ISAba1 adjacent to blaOXA-51-like were carbapenem resistant. Minor differences in blaOXA-51-like sequence were observed in resistant and susceptible isolates. Isolates with blaOXA-23-like in addition were consistently resistant to carbapenems; in all of these ISAba1 lay upstream of blaOXA-23-like, but was not associated with blaOXA-51-like. These results suggest that ISAba1 is providing the promoter for blaOXA-51-like and, probably, for blaOXA-23-like.
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              Cephalosporinase over-expression resulting from insertion of ISAba1 in Acinetobacter baumannii.

              ISAba1-like sequences were identified immediately upstream of the bla(ampC) gene in ceftazidime-resistant Acinetobacter baumannii isolates, but were absent in ceftazidime-susceptible A. baumannii isolates. AmpC over-expression resulted from insertion of ISAba1-like sequences upstream of bla(ampC). ISAba1 provided strong promoter sequences, and it was demonstrated that the change in the ribosome binding site sequence resulting from insertion of ISAba1 did not influence expression of the bla(ampC) gene. Sequence analysis revealed that AmpC sequences of A. baumannii isolates were almost identical and that ISAba1 elements had a high percentage of identity.
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                Author and article information

                Contributors
                Journal
                Int J Microbiol
                Int J Microbiol
                IJMICRO
                International Journal of Microbiology
                Hindawi
                1687-918X
                1687-9198
                2020
                13 June 2020
                : 2020
                : 7380740
                Affiliations
                1Division of Medical Microbiology, Department of Laboratory Medicine & Pathology, Faculty of Health Sciences, Walter Sisulu University, Private Bag: X1, Mthatha 5117, Eastern Cape Province, South Africa
                2Division of Medical Microbiology, National Health Laboratory Services (NHLS), Nelson Mandela Central Hospital, Mthatha 5100, South Africa
                3Department of Biological & Environmental Sciences, Walter Sisulu University, Private Bag: X1, Mthatha—5117, Eastern Cape Province, South Africa
                4School of Chemistry and Physics, College of Agriculture Engineering and Science, University of KwaZulu-Natal, 2nd Floor, Francis Stock Building, Howard College Campus, UKZN, Durban 4041, South Africa
                Author notes

                Academic Editor: Karl Drlica

                Author information
                https://orcid.org/0000-0002-1329-3864
                https://orcid.org/0000-0001-7859-1320
                Article
                10.1155/2020/7380740
                7306865
                32612659
                0df076ea-15b1-4349-ad1a-1919fe39e023
                Copyright © 2020 Yaw Adjei Anane et al.

                This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

                History
                : 27 September 2019
                : 17 February 2020
                : 13 March 2020
                Funding
                Funded by: National Research Foundation
                Award ID: 107619
                Categories
                Research Article

                Microbiology & Virology
                Microbiology & Virology

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