Detection of eap Gene in Clinical Isolates of Staphylococcus aureus Before and After In vitro X-Irradiation and its Association with Antimicrobial Susceptibility

Extracellular adherence protein (Eap) constitutes an important virulence factor enhancing binding and internalization of Staphylococcus aureus into eukaryotic cells. In the present study 63 S. aureus isolates from cancer patients were examined for the existence of the Eap-encoding gene (eap) before and after in vitro X-irradiation using PCR amplification to determine whether this gene could be used as a molecular diagnostic target for sensitive detection and identification of S. aureus infections in X-ray treated cancer patients. Also, to investigate the relations to their antimicrobial sensitivities. The prevalence of the eap gene was (100%) before irradiation however, only (55.56%) were shown to harbor this gene after irradiation (P<0.001). The incidence of linezolid and vancomycin susceptibility was high (100%), while, it was (97.14%) & (94.29%) for Eap-bearing isolates after irradiation, respectively. Interestingly, relations between eap presence and change in the antimicrobial sensitivity pattern before and after irradiation were highly significant for amoxicillin/clavulanic acid (P = 0.000), chloramphenicol (P = 0.006), levofloxacin (P= 0.003), meropenem (P = 0.000), minocycline (P = 0.000), oxacillin(P = 0.000) and penicillin (P=0.002) and significant for quinupristin/dalfopristin (P= 0.038) indicating the association between missing the encoding gene after irradiation and shifting to antibiotic susceptibility.