Expression of resistance to tetracyclines in strains of methicillin-resistant Staphylococcus aureus.

Journal article

A diverse collection of methicillin-resistant Staphylococcus aureus (MRSA) isolates resistant to tetracycline was screened by PCR for the presence of the resistance determinants tetK, tetL, tetM or tetO. Twenty-four of 66 isolates had tetM alone, 21 had tetK alone and 21 had both tetK and tetM (tetKM). All isolates were tetL- and tetO-negative. MICs of tetracycline, doxycycline and minocycline were evaluated for all isolates with or without preincubation in the presence of subinhibitory concentrations of tetracycline or minocycline. All isolates with one or more tetracycline resistance determinants were resistant to tetracycline 8 mg/L without induction of resistance. Some MRSA isolates of each of these three genotypes showed an unexpected lack of resistance to tetracyclines when the disc diffusion or agar dilution method was applied to uninduced cells. Resistance to tetracycline and doxycycline was greater (two- to four-fold) in tetK cells preincubated with tetracycline (tetK MRSA isolates were susceptible to minocycline

Authors: Trzcinski, K; Cooper, B; Hryniewicz, W; Dowson, C

• Publication status: Published
• Journal: Journal of antimicrobial chemotherapy
• Volume: 45
• Issue: 6
• Pages: 763-770
• Publication date: 2000-06-01
• DOI: 10.1093/jac/45.6.763
• EISSN: 1460-2091
• ISSN: 0305-7453
• Language: English
• Keywords: Reverse Transcriptase Polymerase Chain Reaction; Microbial Sensitivity Tests; Phenotype; Genotype; Methicillin Resistance; Staphylococcus aureus; Tetracycline Resistance; Genes, Bacterial