Characterisation of a novel SCCmec VI element harbouring fusC in an emerging Staphylococcus aureus strain from the Arabian Gulf region

Abstract

Fusidic acid is a steroid antibiotic known since the 1960s. It is frequently used in topical preparations, i.e., ointments, for the treatment of skin and soft tissue infections caused by Staphylococcus aureus. There is an increasing number of methicillin-resistant S. aureus (MRSA) strains that harbour plasmid-borne fusB/far1 or fusC that is localised on SCC elements. In this study we examined a series of related CC30-MRSA isolates from the Arabian Gulf countries that presented with SCCmec elements and fusC, including a variant that-to the best of our knowledge-has not yet formally been described. It consisted of a class B mec complex and ccrA/B-4 genes. The fusidic acid resistance gene fusC was present, but contrary to the previously sequenced element of HDE288, it was not accompanied by tirS. This element was identified in CC30 MRSA from Kuwait, Saudi Arabia and the United Arab Emirates that usually also harbour the Panton-Valentin leukocidin (PVL) genes. It was also identified in CC8 and ST834 isolates. In addition, further CC30 MRSA strains with other SCCmec VI elements harbouring fusC were found to circulate in the Arabian Gulf region. It can be assumed that MRSA strains with SCCmec elements that include fusC have a selective advantage in both hospital and community settings warranting a review of the use of topical antibiotics and indicating the necessity of reducing over-the-counter sale of antibiotics, including fusidic acid, without prescription.

Fig 1. Schematic representation of the SCCmec VI _(RUH-32) element and, for comparison, of the SCCmec IVc element of another CC30 strain (TCH60, GenBank CP002110), of the SCCfus element from a CC1-MSSA (MSSA476, BX571857) and of other SCC VI elements that include fusC (HDE288, AF411935; MRSA18, ERR108048; AR466, CP029080.1 and 20121643, ERR1595888/SAMEA3924203).

Genes outside SCC are drawn in light grey, genes within dark grey. mecA is red, typical mec complex genes dark red. fusC and accompanying genes are blue. The ccr recombinase genes are indicated in different shades of green, and dfrA in brown.