The existence and expression of aminoglycoside resistance genes among multidrug-resistant Escherichia coli isolates in intensive care unit centers

Abstract

BackgroundE. coli is among the substantial agents of nosocomial infections. The aim of this study was detection of the aminoglycoside resistance genes and their expression among multidrug-resistant (MDR) E. coli isolates in intensive care units (ICUs). MethodsTotally, 500 isolates of E. coli were collected from ICU centers in Baghdad, Iraq. The antibiotic susceptibility profile of them was determined using disk diffusion test in which seven antibiotics were employed. The gentamicin minimum inhibitory concentration (MIC) was determined using agar dilution method with an antibiotic dilution range of 0.5–256 μg/mL. The polymerase chain reaction (PCR) was implemented to amplify the aac(3)-IIa, ant(2″)-Ia, aac(6′)-lb, aac(3)-Ia, ant(4′)-IIb and aac(6′)-Ib-genes responsible for aminoglycosides resistance. The expression of genes was compared between MDR and non-MDR strains. ResultsThe patients' mean age included 57.33 ± 2 years (66% females vs 34% males, p = 0.0233). Four-hundred and fifty (90%) of isolates were from urinary tract infections (UTIs) and 24 from trachea (48%). Three-hundred and sixty (70%) of isolates were MDR, 260 (52%) of which being resistant to gentamicin. Prior hospitalization (p = 0.0261), prior β-lactams (p < 0.001) and aminoglycoside (p = 0.0113) consumption and diabetes (0.0117) were significant risk factors of MDR-E. coli isolation. The gentamicin MIC of MDR-E. coli included 6–256 μg/mL, 234 (46.8%) of which being in resistant range (64–256 μg/mL). The predominant gene included the aac(3)-IIa (92.6%, n = 463, MIC range: 32–256 μg/mL), followed by aac(6′)-Ib and aac(6′)-Ib-cr, aac(3)-Ia genes being in 224 (44.8%), 37 (7.4%) and 16 (2.2%) and 0% of isolates, respectively. The AMEs gene were detected among isolates with MICs>16 μg/mL and aac(3)-IIa, aac(6′)-Ib and aac(6′)-Ib-cr genes were significantly associated with MIC range of 128–256 μg/mL (p < 0.001). Most of genes expression was significantly higher in MDR than non-MDR strains. ConclusionThe majority of E. coli from ICU was MDR. Prior hospitalization, β-lactams and aminoglycoside consumption and diabetes were significant risk factors of MDR-E. coli isolation. Moreover, the aac(3)-IIa and aac(6′)-lb genes were predominant AMEs which were associated with higher MIC levels. Mechanisms affecting drug resistance genes expression in MDR strains maybe different from those in non-MDR strains.