Extended Spectrum β-lactamase Detection and Antibiotic Susceptibility Profile of Staphylococcus aureus Strains Isolated from Surgical Wounds

Aims: The study aims to determine the antibiotic susceptibility pattern, incidence of β-lactamase and extended-spectrum β-lactamase (ESBL) production in Staphylococcus aureus isolated from surgical wounds.

Study Design: A cross-sectional study designed to evaluate the incidence of antibiotic resistance and ESBL production in S. aureus recovered from surgical wound patients was conducted.

Place and Duration of Study: The study participants included hospitalized patients who were presented with surgical wounds at the Obafemi Awolowo University Teaching Hospital Complex (OAUTHC), Ile-Ife, Osun-State, Nigeria between April-December, 2013.

Methodology: Wound swabs were aseptically collected from one hundred and ten in-patients that have been hospitalized for more than 48 hr in a tertiary teaching hospital. The antibiotic susceptibility typing was conducted using Kirby-Bauer disc diffusion method. The β-lactamase was assayed with the acidometric method while the ESBL was screened with the double disk approximation method. The SHV and TEM resistance genes were detected with polymerase chain reaction (PCR) based technique.

Results: Forty seven (42.7%) S. aureus isolates identified were all multi-resistant to the antibiotics tested, but 42 (89.4%) of the isolates were susceptible to imipenem. β-lactamase was detected in 26 (55.3%) of the S. aureus isolates and ESBL was phenotypically expressed in two isolates. However, sulfhydryl variant (SHV) gene was detected in 5 (19.2%) of the β-lactamase producing strains while the TEM gene was not detected.

Conclusion: This study suggests a continuous screening and surveillance of MRSA among the patients in the hospital setting due to the high prevalence of these microorganisms in Osun state, Nigeri