To estimate the proportion of methicillin-resistant Staphylococcus aureus (MRSA) isolates from humans that were sequence type (ST) 398, we surveyed 24 laboratories in 17 countries in Europe in 2007. Livestock-associated MRSA ST398 accounted for only a small proportion of MRSA isolates from humans; most were from the Netherlands, Belgium, Denmark, and Austria.
Community-acquired methicillin-resistant
Staphylococcus aureus
(CA-MRSA) carrying
pvl
is an emerging problem worldwide. CA-MRSA tends to harbor staphylococcal cassette chromosome
mec
type IV (SCC
mec
IV), to be non-multiantibiotic resistant, and to have different genotypes from the local hospital-acquired MRSA (HA-MRSA). However, in Ireland, 80% of HA-MRSA isolates have the non-multiantibiotic-resistant genotype ST22-MRSA-IV. This study investigated MRSA isolates from Ireland (CA-MRSA, health care-associated MRSA, and HA-MRSA) for the carriage of
pvl
and determined the genotypic characteristics of all
pvl
-positive isolates identified. All 1,389 MRSA isolates were investigated by antibiogram-resistogram typing and SmaI DNA macrorestriction analysis.
pvl
-positive isolates were further characterized by multilocus sequence typing and SCC
mec
,
agr
, and toxin gene typing. Twenty-five (1.8%) MRSA isolates belonging to six genotypes (ST30, ST8, ST22, ST80, ST5, and ST154) harbored
pvl
. Nineteen of these (76%) were CA-MRSA isolates, but a prospective study of MRSA isolates from 401 patients showed that only 6.7% (2/30) of patients with CA-MRSA yielded
pvl
-positive isolates. Thus,
pvl
cannot be used as a sole marker for CA-MRSA. Fifty-two percent of
pvl
-positive MRSA isolates were recovered from patients with skin and soft tissue infections; thirty-six percent were from patients of non-Irish ethnic origin, reflecting the increasing heterogeneity of the Irish population due to immigration. All 25
pvl
-positive isolates carried SCC
mec
IV; 14 (56%) harbored SCC
mec
IV.1 or IV.3, and the remaining 11 isolates could not be subtyped. This study demonstrates that
pvl
is not a reliable marker for CA-MRSA in Ireland and reveals the emergence and importation of diverse genotypes of
pvl
-positive MRSA in Ireland.
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