Co-occurrence of carbapenem and aminoglycoside resistance genes among multidrug-resistant clinical isolates of Acinetobacter baumannii from Cracow, Poland

Abstract

BackgroundAcinetobacter baumannii is a significant hospital pathogen, possessing a considerable degree of antimicrobial resistance. A. baumannii resistance to carbapenems and aminoglycosides is mostly conferred by class D OXA carbapenemases and aminoglycoside-modifying enzymes, respectively. The aim of this study was to determine the prevalence of selected genes encoding OXA carbapenemases and aminoglycoside-modifying enzymes in multidrug-resistant strains of A. baumannii.Material/MethodsThe study included 61 carbapenem-resistant and aminoglycoside-nonsusceptible A. baumannii isolates, collected between 2009 and 2011 in Cracow, Poland. Selected resistance genes, including: blaOXA-51-like, blaOXA-23-like, blaOXA-40-like, blaOXA-58-like, aac(6′)-Ih, aac(3)-Ia, aac(3)-IIa, aac(6′)-Ib, aph(3′)-Ia and aph(3′)-VI, were detected by PCR method.ResultsThe blaOXA-51-like genes were detected in all isolates, while acquired carbapenemase encoding genes were found in 96.7% of tested strains. Presence of blaOXA-40-like and blaOXA-23-like genes was observed among 65.6% and 27.9% of isolates, respectively. Assayed aminoglycoside resistance genes were found to harbor 98.4% of isolates. Among tested strains, we observed the following percentages of resistance determinants: aac(3)-Ia – 78.7%, aph(3′)-VI – 78.7% and aph(3′)-Ia – 27.9%. Analysis of co-occurrence of carbapenem and aminoglycoside resistance genes revealed the highest percentage of strains possessing blaOXA-40-like, aac(3)-Ia, and aph(3′)-VI genes (44.3%).ConclusionsThe blaOXA-40-like and aac(3)-Ia/aph(3′)-VI were the most prevalent genes encoding acquired OXA carbapenemases and aminoglycoside-modifying enzymes, respectively, among A. baumannii strains in Cracow, Poland. Genes conferring resistance to carbapenems and aminoglycosides coexisted in the clinical strains of A. baumannii. The phenomenon of A. baumannii resistance indicates the necessity of monitoring for the presence of the resistance genes.

Role of aminoglycoside-modifying enzymes and 16S rRNA methylase (ArmA) in resistance of Acinetobacter baumannii clinical isolates against aminoglycosides

“…However, 89.4% of our isolates containing this gene showed an MIC range of ≥256 µg/mL for spectinomycin, streptomycin, kanamycin, and tobramycin, while 100% of them exhibited this MIC range for gentamicin. Moreover, according to research by Hasani et al, this gene was detected in SG1-4 1 , while Nowak et al did not detect this gene among their isolates 28 .…”

“…Interestingly, 74% and 88.3% of our isolates containing aphA6 exhibited MIC values of ≥256 µg/mL for amikacin and kanamycin, respectively. Moreover, a study carried out in Poland revealed that aphA6 was the second most prevalent AME gene (78.7%) among 61 A. baumannii isolates 28 . However, aadB, the second most prevalent AME gene in the current study, confers resistance to gentamicin, tobramycin, and kanamycin in gram-negative bacteria 26 , while 95.8%, 93.1%, and 87.6% of our isolates containing aadB showed an MIC range of ≥256 µg/mL for these antibiotics, respectively.…”

Prevalence of carbapenemases among high-level aminoglycoside-resistant Acinetobacter baumannii isolates in a university hospital in China

“…However, there is a paucity of data regarding the aac(3)-IIa gene distribution in A. baumannii . It was reported that only 4 strains (3.7%) carried aac(3)-IIa genes (62); aac(3)-IIa was not identified in any strains in a study by Nowak et al (63). Previous studies have reported that aac(3)-IIa modifies gentamicin, which explains the observed high rate of resistance to gentamicin in these A. baumannii strains (59).…”

Characterization of Carbapenem-Resistant Acinetobacter baumannii Strains Isolated from Hospitalized Patients in Palestine

“…The aminoglycoside-resistant gene aphA6 was reported in Egypt [ 17 ]. On a more international scale, the following aminoglycoside-resistant genes were reported in Poland in 2013: aphA1 , aphA6, and aacC1 [ 18 ]. Our isolates are equipped with not only enzymatic resistance mechanisms, but also the ompA biofilm-producing virulence factor.…”