Abstract
In this study, we investigated the prevalence of aminoglycosides modifying enzymes (AMEs)-encoding genes, including aac(3′)-ΙΙ, ant(3′′)-Ι, aph(3′)-VΙ, and aac(6′)-Ιb-cr and their potential effect on the development of resistance to aminoglycosides and fluoroquinolones in clinical isolates of Klebsiella pneumoniae. According to the phenotypic and biochemical characteristics of 150 clinical samples, 50 (33%) isolates were identified as K. pneumoniae. These isolates were collected from different clinical sources, including urine (15, 30%), blood (12, 24%), sputum (9, 18%), wounds (9, 18%), and burns (5, 10%). The minimum inhibitory concentrations (MICs) assay revealed that the resistance values of isolates were 25 (50%) to gentamicin (≥16µg/ml), 21 (42%) to amikacin (≥64 µg/ml), 15 (30%) to ciprofloxacin (≥4 µg/ml), and 11 (22%) to levofloxacin (≥8 µg/ml). Genotypic detection revealed that aac(3′)-ΙΙ, aac(6′)-Ιb-cr, aph(3′)-VΙ, and ant(3′′)-Ι were found in 47 (94%), 38 (76%), 18 (36%), and 8 (16%) of K. pneumoniae isolates, respectively. The co-resistance pattern for both aminoglycosides and fluoroquinolones was detected in 14 (28%) isolates, of these 10 (71.4%) harbored aac(6′)-Ιb-cr. DNA sequencing for some isolates revealed the presence of point and frameshift mutations in the studied genes. Our study findings suggest that the presence of missense and frameshift mutations may contribute to the elevated resistance to amikacin and gentamicin. The increased prevalence of AMEs-encoding genes among K. pneumoniae isolates could contribute in reducing susceptibility to amikacin and gentamicin. The co-resistance pattern for aminoglycosides and fluoroquinolones was highly associated with the presence of the aac(6′)-Ιb-cr gene.
Highlights
Klebsiella pneumoniae is a Gram-negative bacillus which is classified as a member of the familyEnterobacteriaceae, with cells that are usually surrounded by a polysaccharide capsule that interferes with the host defense by inhibiting phagocytosis [1]
In this study, we investigated the prevalence of aminoglycosides modifying enzymes (AMEs)-encoding genes, including aac(3′)-ΙΙ, ant(3′′)-Ι, aph(3′)-VΙ, and aac(6′)-Ιb-cr and their potential effect on the development of resistance to aminoglycosides and fluoroquinolones in clinical isolates of Klebsiella pneumoniae
The results of minimum inhibitory concentrations (MICs), listed in Table-2, exhibited that 25 (50%) of K. pneumoniae isolates were resistant to gentamicin, with MIC ≥16 μg/ml, while 21 (42%) isolates were resistant to amikacin, with
Summary
Klebsiella pneumoniae is a Gram-negative bacillus which is classified as a member of the family. The frequency of mutations in the AMEs-encoding genes increases the diversity of these genes through the contribution in the emergence of new alleles This results in reducing the active role of common used aminoglycosides which imposes a great health challenge for both patients and physicians that can be inevitably difficult to be confronted and controlled [4,6]. Aac(6′)-Ιb-cr is an allele of the aac(6′)-Ιb gene that belongs to the AACs family and confers coresistance for both aminoglycosides and fluoroquinolones [7] It was detected on the plasmid in K. pneumoniae as one of the plasmid mediated quinolone resistance (PMQR) mechanisms, but recently was found on the chromosome of this species [5]. This study was conducted to investigate the prevalence of some AMEs-encoding genes, namely aac(3′)-ΙΙ, ant(3′′)-Ι, aph(3′)-VΙ, and aac(6′)-Ιb-cr, along with their effects on the resistance to aminoglycosides and fluoroquinolones among clinical isolates of K. pneumoniae. Started by initial denaturation at 95°C for 15 min, followed by 30 cycles of denaturation at 95 ̊C for 1 min, annealing at 55 ̊C for 1 min, and elongation at 72 ̊C for 5 min, while it was finalized with a final extension at 72°C for 5 min [12]
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