Biofilm Formation in Staphylococcus epidermidis Isolated from Hospitalized Patients

Staphylococcus epidermidis as a typical opportunist pathogen is responsible for major nosocomial infections, and has a substantial impact on human life and health. Studies have shown that its main virulence factor is the ability to form biofilms on polymeric surfaces to which it adheres and colonize. The biofilms protect microorganisms such as Staphylococcus epidermidis against the action of antibiotics administered for the treatment of infections and against the patient’s immune system. In the current study, 50 isolates of S. epidermidis were characterized and subjected to biofilm detection by the microtiter plate (MTP), Congo red agar (CRA), and PCR methods. Antibiotic resistance was assessed by the disk diffusion method. The clinical source of S. epidermidis was as follows: blood (n = 20, 40%), urine (n = 4, 8%), wound (n = 8, 16%), catheter (n = 10, 20%), and pus (n = 8, 16%). The current study showed that all the isolates were susceptible to nitrofurantoin, vancomycin, and Synercid and all were resistant to penicillin. Moreover, 68% of the isolates were biofilm-positive by CRA and 76% by MTP methods. Finally, 72% of the isolates showed icaA genes. The pathogenic determinants of S. epidermidis are very complex, multifactorial, and dependent on numerous genetic and environmental factors. Other genes that may contribute to pathogenicity are also involved in biofilm formation in S. epidermidis that need to be studied in more accurate molecular assays.