Abstract:
BACKGROUND : 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
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.
METHODS : One 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.
RESULTS : All 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.
CONCLUSION : The 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.
