Abstract
BackgroundAcinetobacter baumannii is an important hospital-acquired pathogen in healthcare facilities that frequently causes bacteraemia and ventilator-associated pneumonia in intensive care units. Acinetobacter baumannii can be isolated from various sites in the hospital environment like medical equipment, bed linen, medical personnel and indwelling catheters. It is difficult to treat A. baumannii infections because of their highly resistant antimicrobial profiles. The purpose of this study was to determine the prevalence of β-lactamase genes in multidrug-resistant (MDR) clinical A. baumannii isolates using Multiplex-PCR (M-PCR) assays.MethodsOne hundred MDR A. baumannii isolates were collected from the diagnostic division of the Department of Medical Microbiology after routine analysis of the submitted specimens. All collected isolates were identified and tested for susceptibility using the VITEK 2® system (bioMérieux, France). Six isolates were excluded from this study because the isolates were incorrectly identified as A. baumannii with the VITEK 2® system (bioMérieux, France). Molecular tests, namely M-PCR assays, pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) were performed. MLST analyses were performed on representative isolates from the four major pulsotypes (≥5 isolates with 80 % similarity) and selective isolates from each minor pulsotype.ResultsAll the A. baumannii isolates showed 100 % resistance to ampicillin, amoxicillin, cefuroxime, cefuroximine axetil, cefoxitin, cefotaxime and nitrofurantoin. Seven percent of the isolates were resistant to amikacin. Two percent of the isolates were classified as having intermediate susceptibility to tigecycline. A. baumannii isolates showed an antibiotic resistance profile of 67 % and higher to antibiotics, such as ceftazidime, cefepime, imipenem, meropenem, gentamicin, ciprofloxacin and trimethoprim/sulfamethoxazole. None of the isolates were resistant to colistin. The M-PCR assays showed that 99 % of the isolates contained the OXA-51 gene and 77 % contained the OXA-23 gene. None of the isolates contained the GES, GIM, IMP, KPC, NDM, OXA-24, OXA-58, PER, SIM, SPM, VEB and VIM genes. Representative A. baumannii isolates were grouped into five existing sequence types (ST): ST106, ST258, ST339, ST502, ST758 and ST848. Isolates belonging to the pan-European clonal lineages I and II (EUI and EUII) were identified.ConclusionThe high prevalence of MDR A. baumannii isolates has a severe impact on available treatment choices and this in return impacts on treatment outcomes in the studied healthcare facilities. The most dominant ST among the collected isolates was ST758, member of the EUI group. The presence of the OXA-23 gene was not restricted to a specific ST. Continuous research and surveillance is necessary to monitor the circulating β-lactamase genes in clinical settings to guide infection control policies in order to try and curb the spread of this bacterium.
Highlights
Acinetobacter baumannii is an important hospital-acquired pathogen in healthcare facilities that frequently causes bacteraemia and ventilator-associated pneumonia in intensive care units
Collection of A. baumannii clinical isolates Fifty-eight of the isolates were collected from male patients and 36 isolates were collected from female patients
Through molecular methods this study has indicated that 99 % of the A. baumannii isolates contained the OXA-51 gene, compared to Kock et al [5] where only 81% out of the 97 isolates contained this gene
Summary
Acinetobacter baumannii is an important hospital-acquired pathogen in healthcare facilities that frequently causes bacteraemia and ventilator-associated pneumonia in intensive care units. Acinetobacter baumannii is an emerging opportunistic pathogen that can become resistant to multiple antimicrobial agents [1,2,3]. Resistance is acquired through the transfer of integrons, plasmids or transposons that carry groups of genes encoding resistance to several antibiotic families [6]. This bacterium can survive under a wide range of environmental conditions and on surfaces for extended periods of time and this can lead to both endemicity and outbreaks in healthcare facilities [4, 7]. Patients with underlying chronic disease, decreased immunity, indwelling catheters and prolonged hospitalisation are more at risk to become colonised and develop subsequent infection with A. baumannii [7,8,9, 11]
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