| The worldwide emergence of hypervirulent MRSA strains
carrying the loci for Panton-Valentine leukocidin (PVL) is not limited
to the community, but may also be emerging in the hospital environment.
Since 1989, the National Institute of Public Health and the Environment
(RIVM) serves as the national reference center for the surveillance of
MRSA in Dutch hospitals . In 2003, we reported the first detection
of PVL-MRSA in the Netherlands . Since then, all hospital MRSA isolates
(1 per patient) from the national surveillance programme are routinely
tested by PCR for the presence of the PVL loci. In the period 2000-2002,
approximately 10% of all Dutch hospital MRSA isolates carried the PVL
loci, and molecular subtyping by multilocus sequence typing (MLST) revealed
a predominant sequence type: ST80 . This article summarises the characteristics
of PVL-MRSA in the Netherlands in the year 2003.
In 2003, the PVL loci were detected in 8% (123/1601) of the MRSA isolates
sent to the RIVM by Dutch hospitals. The national programme is solely
based on surveillance of MRSA, so the proportion of PVL-positive methicillin-sensitive
S. aureus (MSSA) remains unclear, but deserves attention in the future.
Approximately 75% of the PVL-MRSA isolates were obtained from abscesses,
furuncles, wounds or blood, the remainder from nose or throat; in non-PVL
MRSA isolates the reverse ratio was observed. The male:female ratio
was 1:1 and the mean age was 37 years (range 1-88 years). The PVL-MRSA
isolates were obtained from clinics (40%), outpatient clinics (35%),
and patients visiting general practitioners (25%).
Fifty isolates belonged to epidemic clusters and 73 were sporadic isolates.
These 123 isolates belonged to 49 different PFGE types (Dice cut-off
95%, used for local epidemiology). There were 13 outbreaks with PVL-MRSA
in the Netherlands in 2003, varying from 2-10 cases per outbreak.
One representative of each of the 49 PFGE types was subjected to MLST,
resulting in 11 different STs. The 5 most common STs (found among 78%
(38/49) of the PFGE types) were well-documented global epidemic types:
ST8 (USA300), ST22 (EMRSA-15), ST30 (related to EMRSA-16), ST59 (Europe
and the United States) and ST80 (common 'European' type) .
In the period 2000-2002, the predominant PVL-MRSA genotype was ST80
. This was also the case in 2003: 20% (10/49) of all PVL-MRSA isolates
was assigned ST80. This PVL-MRSA genotype is predominant in other European
countries as well [3-5]. However, another dominant genotype, ST8, emerged
in 2003: 16% (8/49) compared to 1% in 2002. PVL-positive S. aureus
isolates with this genotype have recently been observed in outbreaks
among prisoners and gay men in the United States. [6,7].
Approximately 65% of the PVL-MRSA isolates in 2003 were assigned staphylococcal
cassette chromosome mec (SCCmec) type IV , followed
by SCCmec type III (20%) and type I (15%). Recent data have indicated
the presence of SCCmec type IV in community-acquired MRSA [9,10].
Since 40% of the Dutch isolates were obtained from clinics, PVL-MRSA
isolates are also present, and presumably spreading, in the hospital
environment. The presence of type IV SCCmec MRSA isolates in
European hospitals has been reported before . In general, it is
assumed that type IV SCCmec can be transferred relatively easily
and is present in a wide range of S. aureus backgrounds [12,13]. Because
of the low (= 1%) MRSA prevalence in the Netherlands, we are able to
study virtually all hospital-acquired MRSA found in the national surveillance
programme, which provides an accurate representation of the actual MRSA
situation in our country. The data presented here seem to confirm the
hypothesis that PVL-MRSA might also be or become a hospital-associated
public health threat.