Abstract
Background: Acinetobacter baumannii is one of the most challenging multidrug-resistant (MDR) nosocomial pathogens worldwide. Aminoglycosides are used for the treatment of A. baumannii infections, however, resistance to aminoglycosides is currently emerging, limiting therapeutic choices. Objective: In this study, the prevalence of aminoglycoside resistance and plasmid-mediated mechanisms of aminoglycoside resistance were investigated in A. baumannii clinical isolates collected from ICU patients at a tertiary care hospital in Egypt. Methods: The automated Vitek 2 system was used to identify A. baumannii species and determination of the antimicrobial susceptibility pattern. The identification of A. baumannii was confirmed by the detection of the blaOXA-51-like gene intrinsic to this species. Minimum Inhibitory Concentration (MIC) of gentamicin was determined using E-test following the CLSI breakpoints. Isolates were screened for the prevalence and diversity of the plasmid-carried aminoglycoside-modifying enzymes encoding genes aacC1, aadA1, aadB and aphA6. For genetic diversity analysis, the ERIC-PCR method was performed. Results: All A. baumannii isolates were MDR with high resistance rates to tested antimicrobials. The resistance rate to gentamicin was 92.9% with elevated MICs (≥ 32 μg/mL). The gentamicin-resistant isolates harboured one or more of the studied genes with the prevalence of aphA6 (81%). ERIC-based genotyping revealed that there was no evidence of A. baumannii clonal dissemination among isolates. Conclusion: The study concluded that MDR A. baumannii isolates were highly resistant to gentamicin. The plasmid-carried aminoglycoside-modifying enzymes encoding genes were disseminated among isolates with the AphA6 gene, which was the most prevalent one. The acquisition of more than one aminoglycoside resistance gene was associated with an elevated MIC of gentamicin. Thus, regular surveillance studies of the emerging resistance to antimicrobials and strict measures to control the dissemination of resistance determinants genes are warranted.
Highlights
A. baumannii is a gram-negative, nonfermentative, oxidase-negative coccobacillus that has emerged to an infectious agent of importance worldwide [1]
The study concluded that MDR A. baumannii isolates were highly resistant to gentamicin
The current study aimed to evaluate the prevalence of aminoglycoside resistance; clonal dissemination; and the occurrence rate of the common plasmid-carried aminoglycosides resistance encoding genes, aacC1 (encodes gentamicin acetyltransferase I or aminoglycoside N(3')-acetyltransferase I), aadA1, aadB (encodes aminoglycoside (2') adenyltransferase) and aphA6, among A. baumannii isolates from patients admitted to the Intensive Care Unit (ICU) at a tertiary hospital in Cairo, Egypt
Summary
A. baumannii is a gram-negative, nonfermentative, oxidase-negative coccobacillus that has emerged to an infectious agent of importance worldwide [1]. A. baumannii has been ranked second after Pseudomonas aeruginosa among Gram-negative pathogens causing infections in the hospitalized immunocompromised patients. This organism is responsible for a significant proportion of nosocomial infections, including. A. baumannii has the ability to accumulate mechanisms of resistance to various classes of antimicrobials, leading to the emergence of Multidrug-Resistant (MDR) and Extensive Drug-Resistant (XDR) strains that are difficult to treat [1, 7, 9, 10]. Aminoglycosides have long been used as an alternative or synergistic agent with cell-wall inhibitors for the treatment of infections caused by MDR A. baumannii strains. Acinetobacter baumannii is one of the most challenging multidrug-resistant (MDR) nosocomial pathogens worldwide. Aminoglycosides are used for the treatment of A. baumannii infections, resistance to aminoglycosides is currently emerging, limiting therapeutic choices
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