Take Care MRSA is in the Neighborhood

Abstract

Objective: The aim of the study was to: (i) evaluate the evidence for the emergence of MRSA in our community (ii) to evaluate the antibiotic profile of the isolated CA_MRSA strains. Methods: The clinical specimens were purulent exudates from different forms of suppurative skin lesions that were processed for isolation of S. aureus. The samples were obtained from 200 patients attending the outpatient clinic of the Dermatology Department in the Main University Hospital of Alexandria, Egypt. All samples were inoculated on to the surface of: blood agar, oxacillin supplemented CHROMagar Staph aureus (CSA+), and oxacillin-supplemented Mueller Hinton agar (MH+). Plates were examined after 24 hours and discarded as negative after 48 hours. All staphylococcal colonies isolated on each of CSA+ and MH+ were subjected to antibiotic susceptibility testing by the single disc diffusion method using: oxacillin, ciprofloxacin, vancomycin, gentamicin, erythromycin, clindamycin trimethoprim, and sulfamethoxazole. Results: The most common bacteria isolated was S. aureus, isolated from 81.04% of the studied samples, where 45 (26.32 %) were CA-MRSA. The sensitivity to detect CA-MRSA after 24 h by CSA+ was 73.33%. Prolonging the incubation period to 48 h improved the sensitivity to 95.56 %. The sensitivity of MH+ after 24 h was 68.89%, increased to 80 % after 48 h incubation. Multi-drug resistant strains of the isolated CA-MRSA represented 17.78%. Conclusions: Further evaluation of CHROMagar Staph aureus with direct clinical specimens is needed before this medium can be used for routine direct screening for MRSA. Though the aim of selective and differential media for isolation of MRSA was to reduce the time and work load needed for its full identification when using ordinary media (which is 48 h), unfortunately 48 hours were required to increase the sensitivity of both CSA+ and MH+. So their use needs to be re-evaluated regarding cost, incubation time and performance. Empirical treatment should be guided by antibiotic susceptibility results due to the emergence of MRSA skin infection in the community.

Keywords

• staphylococcus aureus
• ca-mrsa
• oxacillin
• chromagar staph aureus
• oxacillin supplemented mueller hinton agar
• multidrug resistance