The Molecular Investigation of the mecA Gene and Antibiotic Susceptibility Pattern of Staphylococcus aureus and Staphylococcus epidermidis Isolated from Patients with Immune System Disorders at Omid Hospital, Isfahan, Iran

 At present, antibiotic-resistant staphylococci, especially methicillin-resistant strains, are prevalent agents of infections in medical centers and hospitals. The objective of the present investigation was to discern and trace the methicillin resistance gene harbored in two bacterial strains, namely Staphylococcus aureus and Staphylococcus epidermidis, obtained from clinical specimens gathered from patients exhibiting immune system deficiency at Omid hospital located in Isfahan.

 The present investigation was conducted utilizing a descriptive cross-sectional approach. Initially, a total of 70 clinical isolates comprising 35 isolates of S. aureus and 35 isolates of S. epidermidis were obtained from patients who were diagnosed with immunodeficiency and admitted to Omid Hospital located in Isfahan, Iran, from January 2017 to April 2018. After the characterization of the isolates via morphological and biochemical assessments, subsequent evaluation of their antibiotic sensitivity was performed through the utilization of disk diffusion and Epsilometer test (E-test). Then, the identification of the isolates was conducted using the colony PCR method incorporating primers (MCF, MCR, GAIF, and GAIR) and elucidated through molecular analysis.

 In this study, all isolates of S. aureus were resistant to cefoxitin and the MIC of this antibiotic was confirmed using E-test. However, of 35 S. epidermidis isolates, 30 isolates (85.7%) were resistant to oxacillin and 5 isolates (14.3%) were sensitive to oxacillin. According to the molecular findings, out of 35 isolates of methicillin-resistant S. aureus, 4 isolates (11.4%) had the mecA gene, and out of 35 isolates of S. epidermidis, 10 isolates (28.5%) had the mecA gene.

 The present study revealed that precise detection of methicillin resistance in the aforementioned bacterial strains necessitates the employment of both phenotypic and genotypic methods. The frequency of the mecA gene in methicillin-resistant S. aureus (MRSA) was found to be declining. The incidence of methicillin-resistant S. epidermidis (MRSE) is on the rise.