1. Österreichische Agentur für Gesundheit und Ernährungssicherheit (Austrian Agency for Health and Food Safety - AGES), Vienna, Austria
2. Robert Koch-Institut, Berlin, Germany
Methicillin-resistant Staphylococcus aureus
isolates are emerging as significant pathogens in the community. There are substantial differences between community-associated MRSA (CA-MRSA) and healthcare-associated MRSA (HA-MRSA) in terms of staphylococcal chromosome cassette (SCC) mec
types, distribution of toxin genes and antimicrobial susceptibility . CA-MRSA strains often carry a smaller methicillin resistance cassette (i.e. SCCmec
IV or SCCmec
V) and the Panton–Valentine leukocidin (PVL) genes luk
V, and are commonly more susceptible to non-beta-lactam antibiotics . PVL-producing MRSA cause mostly skin and soft tissue infections, but can also cause severe invasive disease, including necrotizing pneumonia [3,4]. Data indicate a higher prevalence of CA-MRSA in young people, and several cases in children have been described . In Europe, the frequency of Panton-Valentine leukocidin (PVL)-positive CA-MRSA is about 3% of all isolates tested, with ST80 (spa
type t044) being the most frequent CA-MRSA . In the United States, clone "USA300" ST8 (spa
type t008) as designated by the Centers for Disease Control and Prevention (CDC), is responsible for the majority of community-acquired infections causing major public health problems . The occurrence of USA300 ST8 (t008) has recently been reported in several European countries [7-13]. Due to the pronounced spreading capacity of the USA 300 clone, early detection is essential for preventing its further diffusion in Europe.
This paper reports nine USA300 isolates found to date in Austria.
Since 2005, the National Reference Laboratory for Staphylococci at the Austrian Agency for Health and Food Safety has offered typing of MRSA isolates free of charge. To date, sequence analysis of the variable X-region of the protein A gene (spa), and testing for the Panton-Valentine leukocidin genes lukS-lukF (PVL) and for mecA have been performed on approximately 1,500 MRSA isolates. Detection of the mecA gene and of the PVL gene was performed in a duplex PCR as described by Stöger et al. . The SCCmec type was determined by a multiplex PCR protocol as described by Oliveira et al. . Molecular typing of the isolates by Multilocus Sequence Typing (MLST) was done as described by Enright et al.  and spa typing as described by Ruppitsch et al. . Multiplex PCR-based agr grouping was performed as described by Moore and Lindsay . The presence of the ACME gene cluster, another USA 300 associated genetic marker, was detected by PCR as described by Diep et al. . SmaI macrorestriction analysis was performed according to the harmonised pulsed-field gel electrophoresis protocol using the proposed guidelines for gel image analysis as described by Murchan et al. .
Antimicrobial susceptibility patterns against gentamicin, erythromycin, clindamycin, tetracycline, chloramphenicol, vancomycin, teicoplanin, ciprofloxacin, sulfamethoxazole, rifampin, quinupristin-dalfopristin, and linezolid were determined by disk diffusion test applying CLSI-criteria and against mupirocin, fosfomycin, and fusidic acid according to instructions provided by the drug producers .
Of the approximately 1,500 MRSA isolates tested, nine were of spa type t008, harboured the PVL gene and the SCCmec IVa genetic element, and yielded the USA300 PFGE pattern. In accordance with the USA300 genotype, all nine isolates belonged to the agrI group and seven harbored the ACME gene cluster. Two isolates have lost the ACME gene cluster as determined by detection of the arcA gene by PCR .
These nine Austrian isolates of USA300 were submitted by five hospital laboratories and obtained from samples taken from eight patients with community-acquired infections and from one nasal swab taken from an asymptomatic carrier during contact tracing. The eight patients (five of them male) had a median age of 49 years (range 20-76) and suffered from various soft tissue infections (Table). None of the cases was lethal.
Epidemiological links to America could be shown for three of the eight patients: Isolate D was obtained from a 52-year-old Austrian postal worker employed in a parcel centre processing the incoming mail from the United States. Isolate G was taken from a 20-year-old US citizen who attended university courses in Austria. Isolate I belonged to a 26-year-old Austrian who suffered a cutaneous infection after he had been bitten by an insect during his vacation in Central America.
Besides general resistance to the beta-lactam antibiotics, the nine isolates showed in vitro resistance against erythromycin. Five isolates were resistant to ciprofloxacin and moxifloxacin, four other isolates showed intermediate resistance to ciprofloxacin. The isolate G obtained from the American student was also resistant to tetracycline (Table).
As a result of the pronounced capacity of USA300 to spread, early detection may be essential for preventing its diffusion in Europe. We have demonstrated the occurrence of USA300 in seven Austrian patients and one asymptomatic carrier, resident in Vienna, Lower Austria, and Salzburg, i.e. in three of the nine Austrian provinces.
CA-MRSA infections are not currently covered by Austria’s infectious disease control laws; there is no mandatory reporting and public health officers have no legal mandate to investigate occurrences of CA-MRSA infections. We feel that public health authorities should be prepared for CA-MRSA outbreaks and make ready the legal requirements necessary for outbreak control. A successful termination of a large furunculosis outbreak in Germany due to lukS-lukF-positive S. aureus by decolonisation strategy, including mupirocin nasal ointment and disinfecting wash solution, has been recently described by Wiese-Posselt et al. .