An IS257-derived hybrid promoter directs transcription of a tetA(K) tetracycline resistance gene in the Staphylococcus aureus chromosomal mec region

• Published in: Journal of bacteriology 2000-06, Vol.182 (12), p.3345-3352
• Main Authors: Simpson, A E, Skurray, R A, Firth, N
• Format: Article
• Language: English
• Subjects: Anti-Bacterial Agents - pharmacology; Antiporters - genetics; Antiporters - metabolism; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Bacteriology; Base Sequence; Chromosomes, Bacterial - genetics; DNA Transposable Elements; Drug resistance; Gene Expression Regulation, Bacterial; Genes; insertion sequence IS257; Methicillin Resistance - genetics; Microbial Sensitivity Tests; Molecular Sequence Data; plasmid pT181; Plasmids - genetics; Plasmids and Transposons; Promoter Regions, Genetic - genetics; Sequence Analysis, DNA; Staphylococcus aureus; Staphylococcus aureus - drug effects; Staphylococcus aureus - genetics; Staphylococcus aureus - growth & development; tetA(K) gene; Tetracycline - pharmacology; Tetracycline Resistance; Transcription, Genetic
• ISSN: 0021-9193; 1098-5530
• DOI: 10.1128/JB.182.12.3345-3352.2000

Transcription of the tetA(K) tetracycline resistance determinant encoded by an IS257-flanked cointegrated copy of a pT181-like plasmid, located within the chromosomal mec region of a methicillin-resistant Staphylococcus aureus isolate, has been investigated. The results demonstrated that transcription of tetA(K) in this strain is directed by both an IS257-derived hybrid promoter, which is stronger than the native tetA(K) promoter in the autonomous form of pT181, and a complete outwardly directed promoter identified within one end of IS257. Despite lower gene dosage, the chromosomal configuration was shown to afford a higher level of resistance than that mediated by pT181 in an autonomous multicopy state. Furthermore, competition studies revealed that a strain carrying the chromosomal tetA(K) determinant exhibited a higher level of fitness in the presence of tetracycline but not in its absence. This finding suggests that tetracycline has been a selective factor in the emergence of strains carrying a cointegrated pT181-like plasmid in their chromosomes. The results highlight the potential of IS257 to influence the expression of neighboring genes, a property likely to enhance its capacity to mediate advantageous genetic rearrangements.