A Field Guide to Pandemic, Epidemic and Sporadic Clones of Methicillin-Resistant Staphylococcus aureus

Abstract

In recent years, methicillin-resistant Staphylococcus aureus (MRSA) have become a truly global challenge. In addition to the long-known healthcare-associated clones, novel strains have also emerged outside of the hospital settings, in the community as well as in livestock. The emergence and spread of virulent clones expressing Panton-Valentine leukocidin (PVL) is an additional cause for concern. In order to provide an overview of pandemic, epidemic and sporadic strains, more than 3,000 clinical and veterinary isolates of MRSA mainly from Germany, the United Kingdom, Ireland, France, Malta, Abu Dhabi, Hong Kong, Australia, Trinidad & Tobago as well as some reference strains from the United States have been genotyped by DNA microarray analysis. This technique allowed the assignment of the MRSA isolates to 34 distinct lineages which can be clearly defined based on non-mobile genes. The results were in accordance with data from multilocus sequence typing. More than 100 different strains were distinguished based on affiliation to these lineages, SCCmec type and the presence or absence of PVL. These strains are described here mainly with regard to clinically relevant antimicrobial resistance- and virulence-associated markers, but also in relation to epidemiology and geographic distribution. The findings of the study show a high level of biodiversity among MRSA, especially among strains harbouring SCCmec IV and V elements. The data also indicate a high rate of genetic recombination in MRSA involving SCC elements, bacteriophages or other mobile genetic elements and large-scale chromosomal replacements.

tst1-positive ST22-MRSA-IVa in healthy Italian preschool children

“…However, our findings suggest that this strain has spread into a wider area, including the Mediterranean region. The detection in our setting of ST22-MSSA, spa t223 appears to be consistent with the hypothesis of a local evolution towards resistance to methicillin, which has been suggested as an alternative to the import of EMRSA-15 into the Middle Eastern area [9]. Further intensive molecular investigations on these strains are needed to reliably track their evolution and dissemination routes.…”

“…However, in our setting an unexpected finding was the predominance of the tst1-positive ST22-MRSA, spa t223 strain. This strain, previously identified as a Middle Eastern variant of UK-EMRSA-15, appears to be identical to the ''Gaza strain'' described by Biber et al [8] as the predominant MRSA clone in healthy children and their parents living in the Gaza strip [8,9]. MRSA strains with similar characteristics have also been reported from Saudi Arabia, Abu Dhabi and Egypt [10].…”

“…The possible relationships between this MRSA strain and the ST22-IVa isolates which have been identified in several healthcare settings in our geographic area deserves further investigation [12]. The most likely origin of the ''Gaza strain'', according to the hypothesis of Biber et al [9], should be a locally prevalent ST22-MSSA spa t223 strain. However, our findings suggest that this strain has spread into a wider area, including the Mediterranean region.…”

Resazurin Microplate Assay: Rapid Assay for Detection of Methicillin Resistant Staphylococcus aureus

“…The same isolate had a cefoxitin MIC value of >32ug/ml when it was tested by the resazurin microplate assay. A similar finding was reported by Garcia-Álvarez and colleagues (2011) (Monecke et al, 2011).…”

Characterization of methicillin-resistantStaphylococcus aureusfrom healthy carrier chickens

“…Indeed, next to the classical MRSA ST398 spa type t899 and t011, three hospital-acquired MRSA ST239 spa type t037 with SCCmec type III were isolated. ST239 clones are disseminated worldwide and are among the oldest MRSA clones found in Europe (Monecke et al, 2011). They account for 90% of the hospital-acquired MRSA in Asia and have also been detected in South America and are nowadays mainly circulating in Eastern Europe (Yamamoto et al, 2012).…”