Novel Type V Staphylococcal Cassette Chromosome mec Driven by a Novel Cassette Chromosome Recombinase, ccrC

Abstract

Staphylococcal cassette chromosome mec (SCCmec) is a mobile genetic element composed of the mec gene complex, which encodes methicillin resistance, and the ccr gene complex, which encodes the recombinases responsible for its mobility. The mec gene complex has been classified into four classes, and the ccr gene complex has been classified into three allotypes. Different combinations of mec gene complex classes and ccr gene complex types have so far defined four types of SCCmec elements. Now we introduce the fifth allotype of SCCmec, which was found on the chromosome of a community-acquired methicillin-resistant Staphylococcus aureus strain (strain WIS [WBG8318]) isolated in Australia. The element shared the same chromosomal integration site with the four extant types of SCCmec and the characteristic nucleotide sequences at the chromosome-SCCmec junction regions. The novel SCCmec carried mecA bracketed by IS431 (IS431-mecA⌬mecR1-IS431), which is designated the class C2 mec gene complex; and instead of ccrA and ccrB genes, it carried a single copy of a gene homologue that encoded cassette chromosome recombinase. Since the open reading frame (ORF) was found to encode an enzyme which catalyzes the precise excision as well as site-and orientation-specific integration of the element, we designated the ORF cassette chromosome recombinase C (ccrC), and we designated the element type V SCCmec. Type V SCCmec is a small SCCmec element (28 kb) and does not carry any antibiotic resistance genes besides mecA. Unlike the extant SCCmec types, it carries a set of foreign genes encoding a restriction-modification system that might play a role in the stabilization of the element on the chromosome.

Offsetting virulence and antibiotic resistance costs by MRSA

“…SCCmec elements I-III are larger than the others and are predominantly found causing hospital-and health-care-associated infections. SCCmec types IV and V are not restricted to these environments and can cause infections in otherwise healthy individuals with no health-care contact (Ito et al, 2004;Ma et al, 2002). Although many individual virulence factors have been found to be associated with community-acquired MRSA (for example cytolytic proteins (Wang et al, 2007), a-toxin (Li et al, 2009) and the PVL leukotoxin (Labandeira-Rey et al, 2007), it is still not clear why these strains are successful both in and outside health-care settings.…”

Association of Virulence Factor (Panton–valentine Leukocidin) With Meca Gene in Staphylococcus Aureus Isolates in Tertiary Care Hospital

“…Thus, when the four native peptidoglycan synthetases (penicillin-binding proteins 1, 2, 3, and 4) are bound and inactivated by beta-lactams, PBP2a can still affect cell wall synthesis. mecA is harbored on the Staphylococcal chromosomal cassette mec (SCCmec), a genetic element that integrates site-specifically into the S. aureus chromosome [1].…”

Methicillin-Resistant Staphylococci Isolated from Healthy Horses and Horse Personnel in Italy

“…To date, 7 major variants of SCCmec, types I-VII, have been distinguished. 12,13 There is a limited amount of information available on MRS in animals compared with those in humans; however, dogs and other pets living in close contact with human MRSA carriers can become colonized with MRSA. 8,15,20 Failure to detect and treat these colonized pets can result in recurrent MRSA colonization or infection in humans.…”