Open AccessFusidic Acid Resistance Rates and Prevalence of Resistance Mechanisms among Staphylococcus spp. Isolated in North America and Australia, 2007-2008
Author(s) -
Mariana Castanheira,
Amy A. Watters,
Jan M. Bell,
John Turnidge,
Ronald N. Jones
Publication year - 2010
Publication title -
antimicrobial agents and chemotherapy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.07
H-Index - 259
eISSN - 1070-6283
pISSN - 0066-4804
DOI - 10.1128/aac.01390-09
Subject(s) - fusidic acid , staphylococcus aureus , microbiology and biotechnology , biology , micrococcaceae , sccmec , staphylococcal infections , veterinary medicine , antibacterial agent , methicillin resistant staphylococcus aureus , medicine , bacteria , antibiotics , genetics
Among 4,167 Staphylococcus aureus and 790 coagulase-negative Staphylococcus (CoNS; not S. saprophyticus) isolates collected consecutively from North American and Australian hospitals, only 87 (1.7% overall) isolates displayed a fusidic acid (FA; also known as CEM-102) MIC of > or = 2 microg/ml (FA resistance). These strains were further evaluated with a multiplex PCR to amplify the acquired resistance genes fusB, fusC, and fusD. Mutations in fusA and fusE were evaluated in all isolates showing an absence of acquired resistance genes and/or showing FA MIC values of > or = 64 microg/ml. S. aureus resistance rates were very low in the United States (0.3%) and were higher in Canada and Australia (7.0% for both countries). Among CoNS isolates, FA resistance rates were significantly more elevated than that for S. aureus (7.2 to 20.0%; the highest rates were in Canada). All 52 (41 CoNS) FA-resistant isolates from the United States showed FA MIC results of < or = 64 microg/ml, and 7 of 11 S. aureus isolates carried fusC. CoNS strains from the United States carried fusB or fusC. In Canada, fusB and fusC occurrences were similar among S. aureus and CoNS isolates, and modestly elevated FA MIC values were observed (all MIC results were < or = 32 microg/ml). Isolates from Australia showed MIC values ranging from 2 to 32 microg/ml, and S. aureus isolates were predominantly fusC positive. fusA mutations were detected in only three S. aureus isolates, conferring FA MIC values of 2 to 8 microg/ml. Target mutations have been considered the primary FA resistance mechanism among Staphylococcus spp.; however, acquired resistance genes appear to have a dominant role in resistance against this older antimicrobial agent. In summary, this study shows that acquired genes are highly prevalent among FA-resistant strains (>90%) in three nations with distinct or absence (United States) of fusidic acid clinical use.