An epidemic clone of methicillin-resistant Staphylococcus aureus (EMRSA-15) ST22-SCCmecIV has been detected in hospitals of all regions of the Czech Republic.
Healthcare-associated MRSA strains with a susceptibility profile similar to that of EMRSA-15 (resistant to -lactams, ciprofloxacin and erythromycin) began to emerge in the Czech Republic with increasing frequency early in 2003. To find out whether the EMRSA-15 clone had spread across the country, MRSA isolates were analysed retrospectively and prospectively over a four year period (2001-2004) in close cooperation with the Czech participants of the European Antimicrobial Surveillance System (EARSS, http://www.rivm.nl/earss/). Of 349 mecA positive S. aureus isolates, 64 strains resistant to erythromycin, clindamycin, ciprofloxacin and, exceptionally, to chloramphenicol were selected for further molecular analysis. They were collected as colonising or infecting organisms from various clinical sources; one isolate originated from a hospital environment.
Strains were characterised by macrorestriction profile, HindIII ribotype, SCCmec type and sequence type (ST) as described previously . EMRSA-15 (ST22-SCCmecIV) (n=40) from blood (n=12), wound infection (n=11), nose (n=5), sputum (n=3), pus (n=2), perineum (n=2) and single isolates from urine, catheter, puncture specimen, throat and the environment were characterised further. The total annual incidence of EMRSA-15 isolates increased from 3 in 2001 to 19 in 2004. The EMRSA-15 strains were isolated from blood from septicaemic patients (n=12), but the incidence of the blood isolates was stable over the study period (2001: 2 isolates; 2002: 1 isolate; 2003: 5 isolates and 2004: 4 isolates).
Amplification of MLSB resistance genes (ermA, ermB, ermC, msrA) was performed as previously described . The strains only carried the ermC gene, while the msrA gene harboured by two of four EMRSA-15 strains in the previous study  was not detected. None of A, B, C, D and E enterotoxins, toxic shock syndrome toxin 1 (TSST-1) and exfoliative toxins A and B was detected by the SET-RPLA, TST-RPLA, and EXT-RPLA kits. Amplicons of seg genes  specific for enterotoxin G were detected in all EMRSA-15 strains (n=40) and those of sei genes specific for enterotoxin I were found in most of the strains (n=37).
EMRSA-15 emerged as a significant nosocomial pathogen in the United Kingdom (UK) in 1991, and ten years later was one of the eleven major MRSA clones  that spread internationally and rapidly displaced most of the other MRSA strains .
Clinical nosocomial MRSA strains in the Czech Republic were studied systematically in 1996-1997  and 2000-2002 . The Brazilian clone and its descendants, the Czech (ST239) and Iberian clones (ST247), were detected throughout the periods studied. Moreover, four strains collected in hospitals of two cities were classified into the EMRSA-15 clone . Only one strain of this clone was isolated from blood of a patient admitted to hospital with fever of unknown origin in the eastern part of the Czech Republic in 2001. Two strains were isolated from wound infections in patients admitted to another hospital in the same region in 2002.
In a previous study  four EMRSA-15 strains were detected in only one administrative region, in two hospitals located about 30 km apart, while in the more recent study, 40 EMRSA-15 strains were recovered in 16 hospitals. Detection of the strains in all administrative regions (n=7) documents the spread of the EMRSA-15 clone throughout the country. The clone was most frequently detected in the northeast part of the country (six hospitals), where it had previously been sporadic .
The route and mechanism of their spread remain unknown, and accurate tracking of the spread could not be confirmed retrospectively. Nevertheless, a hypothesis is suggested: hundreds of asylum applicants, mainly from the eastern Czech Republic, have travelled to the United Kingdom since 1997, but the majority were unsuccessful in their applications, and returned to the Czech Republic within a few weeks or months. It is possible that while in the UK, these people came into contact with healthcare providers, and sometimes visited hospitals where the EMRSA-15 clone is endemic. It is probable that representatives of the EMRSA-15 clone were introduced into the Czech Republic on several different occasions.
Another hypothesis is that the clone may have spread from other countries where it is endemic (such as Germany, Ireland or Sweden). In particular, Germany shares a border with the Czech Republic and there is cross border movement of tourists and workers/business people. Such factors, alone or in combination with other unknown factors, may have played a role in the introduction and spread of the EMRSA-15 clone in the Czech Republic.
*This work was supported by the Reference Laboratory for Antibiotics, National Institute of Public Health, Prague, Czech Republic. The authors thank P. Petráš, National Institute of Public Health, for screening the EMRSA-15 strains for the production of exfoliative toxins and enterotoxins and the Czech EARSS participants: N Bartoníková, M Bártová, E Bendová, T Bergerová, Z Bohunová, D Burgetová, M Dovalová, AGrabowiecka, V Hásková, P Havránek, B Heinigeová, B Horová, M Horníková, E Chmelařová, J Janečková, A Jedličková, P Ježek, V Jindrák, R Jirsa, M Kolář, J Kotalíková, P Linhart, M Machučová, D Malotová, J Miklová, M Mlynaříková, H Nedvědová, O Nýč, J Niemczyková, V Petkov, E Plíšková, Z Pokorná, J Pomykal, L Poustecká, E Pozlerová, B Puchálková, J Rousková, M Rumlerová, A Sekáčová, J Scharfen, H Skáčaniová, A Steinerová, E Šimečková, M Štolbová, E Šťastná, R Tejkalová, L Trojan, J Valenta and E Veselá. Thanks are also due to M Aires de Sousa for methodical cooperation and E Kodytková for reviewing the manuscript.