Clonal lineages detected amongst tetracycline-resistant meticillin-resistant Staphylococcus aureus isolates of a Tunisian hospital, with detection of lineage ST398.

Tetracycline resistance has been postulated as a potential phenotypic marker of livestock-associated lineage ST398 amongst meticillin-resistant Staphylococcus aureus (MRSA) clinical isolates in some European hospitals. The objective of this study was to determine if this marker could also be applied to Maghrebian countries. In total, 99 MRSA isolates were collected in a Tunisian hospital during January 2011-October 2012, and 24 tetracycline-resistant MRSA isolates of this collection were characterized. All isolates were tested for antimicrobial resistance phenotypes and genotypes, molecular typing, and virulence genes. Multilocus sequence typing showed that the majority of the isolates (19/24) belonged to clonal complex CC8 (ST247, n = 12 isolates; ST239, n = 6 isolates; ST241, n = 1 isolate). The remaining isolates belonged to CC398 (ST398, n = 1 isolate), CC5 (ST5 and ST641, n = 2 isolates), and CC80 (ST728, n = 2 isolates). Spa typing discriminated MRSA in eight spa types: bib26 (n = 12 isolates), bib26 (n = 5 isolates), bib26 (n = 2 isolates), and bib26, bib26, bib26, bib26 and the new bib26 (n = 1 isolate each). Three agr groups were found amongst the studied isolates: agr group I (n = 20 isolates), agr group II (n = 2) and agr group III (n = 2 isolates). We report the detection of one MRSA ST398-t899 isolate in the nasal sample of a farmer patient in Tunisia, representing the first report of ST398 in humans in Africa. Tetracycline resistance seems not to be a good phenotypic marker for MRSA ST398 strains in Tunisia, where CC8 was the most prevalent lineage. Continuous efforts to understand the changing epidemiology of this micro-organism are necessary not only for appropriate antimicrobial treatment and effective infection control, but also to monitor its evolution.