Identification of Streptomycin Resistance Gene Among Enterococcus spp. Isolated from Hospitals of Tehran by PCR

Enterococci are normal flora and present in the intestinal tract of humans and many mammals. Today, the increasing prevalence of resistant enterococci to aminoglycosides is a major problem in hospitals around the world. In Enterococci, aph (3 ') - IIIa gene plays a major role in the emergence of resistance to streptomycin. The aim of this study was to identify this gene in enterococci isolated from patients using PCR method in Tehran.
In this study, 350 clinical samples were collected from Milad, Imam Khomeini, and Baghiyatallah hospitals during the years 2015-2014. Enterococcus species were identified based on specific biochemical tests and culture. Then, disk diffusion method was performed according to CLSI guidelines to determine the drug resistance of Enterococcus isolates to different antibiotics. The following primer to streptomycin resistance genes, aph (3 ') - IIIa was used in the PCR method.
Among the 150 samples, 87 samples (58%) were reported as Enterococcus faecalis, and 63 (42%) as Enterococcus faecium. In Antibiotic test, strains showed high resistance to tetracycline and erythromycin whereas the least resistance was observed to chloramphenicol and vancomycin, respectively. The high resistance to Streptomycin was in 22.2% strains which included aph (3') -IIIa gene.
The results of this study can be concluded that the presence of aph (3') -IIIa gene is the main cause of antibiotic resistance to streptomycin in Enterococcus faecium and E. faecalis strains that is growing gradually in the hospitals in Tehran. Therefore, early detection of this type of resistance with the PCR method could be the best way to prevent the spread of infections caused by this bacterium.