A novel hybrid SCCmec-mecC region in Staphylococcus sciuri

Area of Science:

• Microbiology
• Genetics
• Antimicrobial Resistance

Background:

• Methicillin resistance in Staphylococcus species is mediated by the alternative penicillin-binding protein 2a (PBP2a), encoded by the mecA gene.
• A novel mecA variant, mecC, has been identified in Staphylococcus aureus from human and animal sources.
• Staphylococcus sciuri subsp. carnaticus isolates from bovine infections were found to harbor multiple mecA homologues.

Purpose of the Study:

• To investigate the genetic context of mecA homologues in Staphylococcus sciuri subsp. carnaticus.
• To analyze the expression and excision of SCCmec elements and mec genes in these isolates.
• To understand the role of animal-associated staphylococci in antibiotic resistance gene reservoirs.

Main Methods:

• Whole-genome sequencing of two Staphylococcus sciuri subsp. carnaticus isolates.
• Polymerase Chain Reaction (PCR) and Reverse Transcription PCR (RT-PCR) for gene analysis.
• Analysis of SCCmec element excision and mec gene expression.

Main Results:

• Identification of a novel hybrid SCCmec region containing a class E mec complex (mecI-mecR1-mecC1-blaZ) and a staphylococcal cassette chromosome mec (SCCmec) type VII element.
• Demonstration of the excision capability of both SCCmec type VII and a hybrid SCCmec-mecC element.
• Expression of mecC and mecA genes, but not mecA1, in oxacillin-supplemented liquid culture.

Conclusions:

• The mecC gene is present in a variety of staphylococcal species.
• Coagulase-negative staphylococci from animals may serve as reservoirs for antibiotic resistance genes.
• This study contributes to understanding the dissemination of antibiotic resistance mechanisms in staphylococci.