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Surveillance of Staphylococcus aureus susceptibility to fusidic acid in five Canadian laboratories

Abstract number: P1738

Rennie R., Brosnikoff C., Harris M., Turnbull L., Kidson P., Yamamura D., Kelly M., Forward K., Laverdiere M., Skov R., Larsen A.

Objective: Fusidic acid has been available on the Canadian market since the early 1980s. The objective of this study was to perform regular surveillance of fusidic acid susceptibility of Staphylococcus aureus strains in five Canadian diagnostic laboratories.

Methods:S. aureus strains were collected from cultures submitted to the routine laboratory during March and September on an annual basis. Sixty (60) strains were collected from each of the five diagnostic laboratory sites; 10 strains from each site were meticillin resistant Staph. aureus (MRSA) isolates. Only one strain per patient was tested in each test period. Routine antimicrobial susceptibility testing was performed in the submitting laboratory by an automated susceptibility method. Testing for fusidic acid susceptibility was performed by disk diffusion (Oxoid, Nepean, Ontario) and ETest® (AB Biodisk, Solna, Sweden) on Mueller Hinton agar plates. The plates were incubated at 35° C for 18–20 hr in ambient air. A zone diameter of >20 mm and an MIC of leqslant R: less-than-or-eq, slant2 mg/L (Leo Pharma Inc) were considered to be susceptible.

Results: 603 S. aureus strains were tested for fusidic acid susceptibility during 2007, including 100 MRSA strains. 187/603 (31%) of strains were collected from inpatients and 416/603 (69%) from outpatients. 22/300 (7.3%) were resistant to fusidic acid in March and 32/303 (10.6%) in September. 3/50 (6%) strains of MRSA were resistant to fusidic acid in March and 2/50 (4%) in September. All 5 strains of MRSA resistant to FA in 2007 were isolated from one laboratory. Spa typing showed that the fusidic acid resistant strains appeared to be clonal, and not related to resistant clones observed in Europe.

Conclusions: Fusidic acid is the most widely prescribed topical antimicrobial in Canada. Compared to data gathered over the previous 7 years, ongoing surveillance suggests that there has been no trend towards increasing fusidic acid resistance in S. aureus strains isolated across the country. The resistance rate remains low even among the MRSA strains submitted for testing. These data support the importance of continuing surveillance and suggest that fusidic acid has maintained its efficacy over the years.

Session Details

Date: 19/04/2008
Time: 00:00-00:00
Session name: 18th European Congress of Clinical Microbiology and Infectious Diseases
Subject:
Location: Barcelona, Spain
Presentation type:
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