Abstract
The emergence of infections associated to new antimicrobial resistance in Acinetobacter baumannii (Ab) genotypes represents a major challenge. In this context, this study aimed to determine the diversity of resistance mechanisms and investigate clonal dissemination and predominant sequence types (STs) in multidrug-resistant Ab strains of clinical (tracheal aspirate, n = 17) and environmental (surface, n = 6) origins. Additionally, the major clones found in clinical (A) and environmental (H) strains had their complete genomes sequenced. All strains were submitted to polymerase chain reactions (PCR) for the detection of the ISAba1/blaOXA-51-like and ISAba1/blaOXA-23-like genes, while the expression of genes encoding the carO porin, AdeABC (adeB), AdeFGH (adeG), and AdeIJK (adeJ) efflux pumps was determined by real time PCR (qPCR). Most of the strains were characterized as extensively drug-resistant (XDR) with high minimal inhibitory concentrations (MICs) detected for tigecycline and carbapenems. Associations between ISAba1/OXA-51 and ISAba1/OXA-23 were observed in 91.3% and 52.2% of the strains, respectively. Only the adeB gene was considered hyper-expressed. Furthermore, most of the strains analyzed by the MuLtilocus Sequence-Typing (MLST) were found to belong to the clonal complex 113 (CC113). In addition, a new ST, ST1399, belonging to CC229, was also discovered herein. Strains analyzed by whole genome sequencing presented resistance genes linked to multidrug-resistance phenotypes and confirmed the presence of Tn2008, which provides high levels carbapenem-resistance.
Highlights
Acinetobacter baumannii (Ab) is one of the most successful pathogens responsible for hospitalacquired infections worldwide, mainly in immunocompromised patients and those admitted to intensive care units (ICUs) [1,2].Carbapenem resistance in Ab is most frequently mediated by intrinsic (OXA-51-like) or acquired oxacillinases [3]
Tracking the evolution and clonal dissemination of carbapenem resistance in Ab isolates is important to support the implementation of control strategies, which is only possible through a comprehensive understanding of the complete genome of these strains
The presence of genes encoding the AdeABC, AdeFGH, and AdeIJK efflux pumps was evidenced in all analyzed strains
Summary
Carbapenem resistance in Ab is most frequently mediated by intrinsic (OXA-51-like) or acquired (mainly OXA-23-like) oxacillinases [3]. The increased expression of chromosomal genes of resistancenodulation-cell division (RND)-type efflux systems [2,7] and the decreased expression of certain outer membrane channel-forming proteins [8,9] play an important role in Ab multidrug resistance. Other studies worldwide indicate that multidrug-resistant Ab is related to CC92 [17,12,18,19]. Tracking the evolution and clonal dissemination of carbapenem resistance in Ab isolates is important to support the implementation of control strategies, which is only possible through a comprehensive understanding of the complete genome of these strains
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