A preliminary study of Aminoglycoside Modifying Enzymes (AMEs) of Multiple Antibiotic Resistance of Methicillin-resistant Staphylococcus aureus (MRSA) isolated from clinical specimens in Al-Diwaniya/Iraq

Abstract

Staphylococcus aureus (SA) plays a significant role in numerous serious life-threatening infections that present a major challenge to public health in controlling it, especially those resistant to methicillin (MR) known as (MRSA). These pathogens have resistance to other classes of antimicrobial agents including aminoglycoside molecules which mostly resist it through three types of medically significant enzymes: APH (3')-III, ANT (4')-I and (6')/APH(2"). In this paper, seventy-two MRAS were isolated from different lesions from Al-Diwaniya teaching hospital, and Maternity and Children teaching hospital, during the period from January to July 2018. Disc diffusion method, minimum inhibitory concentration(MIC), and bactericidal (MBC) were carried out to MRAS strains subjected to phenotype and genotype identification as well as to detect AMEs genes. Susceptibility of 29 drugs of MRAS strains was: 100% susceptible to vancomycin and chloramphenicol, but 100% resistant to penicillin, cefoxitin, ceftriaxone, aztreonam, and nitrofurantoin. Thus, a (72.2%) of MRAS were found to be either MDR or XDR including 20 aminoglycoside resistant (AR) strains. Multiple antibiotic resistance (MAR) index of a total of 20(100%)AR strains were recorded high values>0.2 ranged(0.48-0.83) from the maximum MAR index:1. Moreover, MIC and MBC values of vancomycin, for S. aureus, ranged from 2 μg/mL to 8 μg/mL. Phenotype resistance of MRSA strains to aminoglycoside molecules was: kanamycin 20(27.8%)tobramycin 18(25%); gentamicin 16(22.2%);amikacin 14(19.4%); and netilmicin 8(11.1%). PCR analysis led to all 100% MRSA caring for the mecA gene. Frequency of genes encoding aminoglycosides resistance aac(6')/aph (2");80%, aph (3')-IIIa;45%, and ant (4')-Ia; 35%. The aac(6')/aph (2") and ant (4')-Ia genes was the only determinant of resistance in 5 and 1 strains respectively. Correlation between MRSA-AR strains and AMEs genes was 90%. In conclusion, MRSA strains harbouring the mecA gene are currently widely distributed in the Al-Diwaniya governorate. Co-production with AMEs may increase the risk of the spreading of multiple drug resistance clinical strains in communities and hospitals.