Characterization of Aminoglycoside Modifying Enzymes Producing E. coli and Klebsiella pneumoniae Clinical Isolates

Abstract

Antimicrobial resistance gene profile characterization and dissemination offer useful detail on the possible challenge in treating bacteria. The development of aminoglycoside modifying enzymes (AMEs) is considered as the primary mechanism of resistance to aminoglycosides, in addition to the 16S rRNA methylases. This study aimed at isolation and characterization of aminoglycosides resistant clinical isolates of enterobacteriaceae family from different clinical samples. Over a period of 24 months, thirty samples were collected and 49 clinical isolates of E. coli [n=25], Klebsiella [n=13], Enterobacter species (n=7) and Proteus species (n=4) were isolated from Egyptian clinical laboratories. The identities of the cultures were confirmed following standard microbiological procedures. Resistance of the isolates to aminoglycosides was determined by the disc diffusion method and isolates with highest resistance (n=9) were selected and investigated for 16S rRNA methylase and AMES encoding genes by polymerase chain reaction (PCR) and sequencing. In general, aminoglycoside resistance was found in 95% of the isolates; the isolates displayed the highest rate of resistance to netilmicin (75%) and kanamycin (55%), while resistance to gentamycin (18%) and tobramycin (16%) was low. A total of 9 isolates have the highest aminoglycoside resistant rate, showed the highest appearance for aac(6′)-Ib as well as ant (3″)-Ia resistant genes, with aac (3)-II (44%) and ant (4′)-IIb (34%) following closely. The high prevalence of AMEs observed among resistant isolates in this study suggests the urgent need for more efficient treatment designs to mitigate the selection burden as well as improved care of patients who have been infected with these drug-resistant organisms.