[1] LOIMAA DIST HOSP, MED CLIN, LOIMAA, FINLAND
[2] TURKU UNIV, CENT HOSP, PERSONNEL HLTH CTR, TURKU, FINLAND
[3] TURKU CITY HOSP, MED CLIN, TURKU, FINLAND
[4] TURKU UNIV, DEPT MED MICROBIOL, TURKU, FINLAND
[5] TURKU UNIV, CENT HOSP, MED CLIN, 20520 TURKU, FINLAND