Detection of novel chromosome-SCCmec variants in Methicillin Resistant Staphylococcus aureus and their inclusion in PCR based screening

Findings. To facilitate automation, a novel DNA extraction method for MRSA was adopted. The MRSA specific chromosome-SCCmec PCR was adapted, additional primers were added, and the performance was validated. From various laboratories in The Netherlands we received a total of 86 MRSA clinical isolates, that were negative in commercially available tests. We identified 14 MRSA strains with new variant chromosome-SCCmec junctions by sequence analysis. These MRSA strains appeared to carry SCCmec sequences with a high degree of homology to SCC regions of S. epidermidis and S. haemolyticus. All were included for detection in chromosome-SCCmec based PCR. Background: Efficient management of Methicillin Resistant Staphylococcus aureus (MRSA) in the hospital is needed to prevent dissemination. It is important that MRSA can be rapidly identified, and effective infection control measures can be initiated. Equally important is a rapid MRSA negative report, especially for patients in isolation. For negative screening we implemented fully automated high through-put molecular screening for MRSA. Conclusions: Fourteen variant chromosome-SCCmec junctions in MRSA, that are not detected in commercially available MRSA detection kits were added to our PCR to detect all currently known variant SCC-mec types of MRSA

Impact of target site distribution for Type I restriction enzymes on the evolution of methicillin-resistant Staphylococcus aureus (MRSA) populations.

A limited number of Methicillin-resistant Staphylococcus aureus (MRSA) clones are responsible for MRSA infections worldwide, and those of different lineages carry unique Type I restriction-modification (RM) variants. We have identified the specific DNA sequence targets for the dominant MRSA lineages CC1, CC5, CC8 and ST239. We experimentally demonstrate that this RM system is sufficient to block horizontal gene transfer between clinically important MRSA, confirming the bioinformatic evidence that each lineage is evolving independently. Target sites are distributed randomly in S. aureus genomes, except in a set of large conjugative plasmids encoding resistance genes that show evidence of spreading between two successful MRSA lineages. This analysis of the identification and distribution of target sites explains evolutionary patterns in a pathogenic bacterium. We show that a lack of specific target sites enables plasmids to evade the Type I RM system thereby contributing to the evolution of increasingly resistant community and hospital MRSA

A Clonal Complex 12 Methicillin-Resistant Staphylococcus aureus Strain, West Australian MRSA-59, Harbors a Novel Pseudo-SCCmec Element

Copyright © 2015, American Society for Microbiology. All Rights Reserved. A West Australian methicillin-resistant Staphylococcus aureus strain (WA MRSA-59) was characterized by microarray and sequencing. Its pseudo-staphylococcal cassette chromosome mec (SCCmec) element comprised dcs, Q9XB68-dcs, mvaS-SCC, Q5HJW6, dru, ugpQ, ydeM, mecA-mecR-mecI, txbi mecI, tnp IS431, copA2-mco (copper resistance), ydhK, arsC-arsB-arsR (arsenic resistance), open reading frame PT43, and per-2. Recombinase genes, xylR (mecR2), and PSM-mec (phenol-soluble modulin) were absent. We suggest that mec complex A should be split into two subtypes. One harbors PSM-mec and xylR (mecR2). It is found in SCCmec types II, III, and VIII. The second subtype, described herein, is present in WA MRSA-59 and some coagulasenegative staphylococci