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Analysis of genes encoding penicillin-binding proteins in clinical isolates of Acinetobacter baumannii.

ABSTRACT: There is limited information on the role of penicillin-binding proteins (PBPs) in the resistance of Acinetobacter baumannii to ?-lactams. This study presents an analysis of the allelic variations of PBP genes in A. baumannii isolates. Twenty-six A. baumannii clinical isolates (susceptible or resistant to carbapenems) from three teaching hospitals in Spain were included. The antimicrobial susceptibility profile, clonal pattern, and genomic species identification were also evaluated. Based on the six complete genomes of A. baumannii, the PBP genes were identified, and primers were designed for each gene. The nucleotide sequences of the genes identified that encode PBPs and the corresponding amino acid sequences were compared with those of ATCC 17978. Seven PBP genes and one monofunctional transglycosylase (MGT) gene were identified in the six genomes, encoding (i) four high-molecular-mass proteins (two of class A, PBP1a [ponA] and PBP1b [mrcB], and two of class B, PBP2 [pbpA or mrdA] and PBP3 [ftsI]), (ii) three low-molecular-mass proteins (two of type 5, PBP5/6 [dacC] and PBP6b [dacD], and one of type 7 (PBP7/8 [pbpG]), and (iii) a monofunctional enzyme (MtgA [mtgA]). Hot spot mutation regions were observed, although most of the allelic changes found translated into silent mutations. The amino acid consensus sequences corresponding to the PBP genes in the genomes and the clinical isolates were highly conserved. The changes found in amino acid sequences were associated with concrete clonal patterns but were not directly related to susceptibility or resistance to ?-lactams. An insertion sequence disrupting the gene encoding PBP6b was identified in an endemic carbapenem-resistant clone in one of the participant hospitals.

SUBMITTER: Cayo R

PROVIDER: S-EPMC3232777 | biostudies-literature | 2011 Dec

REPOSITORIES: biostudies-literature

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Analysis of genes encoding penicillin-binding proteins in clinical isolates of Acinetobacter baumannii.

Cayô Rodrigo R Rodríguez María-Cruz MC Espinal Paula P Fernández-Cuenca Felipe F Ocampo-Sosa Alain A AA Pascual Alvaro A Ayala Juan A JA Vila Jordi J Martínez-Martínez Luis L

Antimicrobial agents and chemotherapy 20110926 12

There is limited information on the role of penicillin-binding proteins (PBPs) in the resistance of Acinetobacter baumannii to β-lactams. This study presents an analysis of the allelic variations of PBP genes in A. baumannii isolates. Twenty-six A. baumannii clinical isolates (susceptible or resistant to carbapenems) from three teaching hospitals in Spain were included. The antimicrobial susceptibility profile, clonal pattern, and genomic species identification were also evaluated. Based on the ...[more]

PMID: 21947403

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Project description:IntroductionCarbapenem-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 methodsA 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.ResultsMost 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 ISAba1/bla OXA-51-like and ISAba1/bla OXA-23-like were detected in 15% and 40% of the strains, respectively. The detection of bla OXA-23-like, ISAba1/bla OXA-51-like, ISAba1/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.ConclusionsResults 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.

Project description:BackgroundAcinetobacter baumannii is a nosocomial pathogen which is establishing as a major cause of morbidity and mortality within the healthcare community. The success of this pathogen is largely due to its ability to rapidly gain resistance to antimicrobial therapies and its capability to persist in an abiotic environment through the production of a biofilm. Our tertiary-care hospital has showed high incidence of carbapenem-resistant Acinetobacter baumannii (CRAB) isolates.MethodsIn this study we explore both genotypic and phenotypic properties of 26 CRAB isolates: 16 isolates were collected from January 2010 to March 2011, and 10 were collected between February and May 2015.ResultsWe determined that all 26 CRAB isolates possessed multiple β-lactamase genes, including genes from Groups A, C, and D. Specifically, 42% of the isolates possesses the potentially plasmid-borne genes of OXA-23-like or OXA-40-like β-lactamase. The presence of mobile gene element integron cassettes and/or integrases in 88% of the isolates suggests a possible mechanism of dissemination of antibiotic resistance genes. Additionally, the location of insertion sequence (IS) ISAba1 in promotor region of of the OXA-51-like, ADC-7, and ampC genes was confirmed. Multilocus sequence typing (MLST) demonstrated that all 26 CRAB isolates were either sequence type (ST)-229 or ST-2. Interestingly, ST-2 went from being the minority CRAB strain in the 2010-2011 isolates to the predominant strain in the 2015 isolates (from 32 to 90%). We show that the ST-2 strains have an enhanced ability to produce biofilms in comparison to the ST-229 strains, and this fact has potentially led to more successful colonization of the clinical environment over time.ConclusionsThis study provides a longitudinal genetic and phenotypic survey of two CRAB sequence types, and suggests how their differing phenotypes may interact with the selective pressures of a hospital setting effecting strain dominance over a 5-year period.

Dataset Information

Analysis of genes encoding penicillin-binding proteins in clinical isolates of Acinetobacter baumannii.

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Analysis of genes encoding penicillin-binding proteins in clinical isolates of Acinetobacter baumannii.

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