Occupational acquisition of methicillin-resistant Staphylococcus aureus in humans--a description of MRSA carrier and infected cases from the Region of North Jutland in Denmark.

Since 2006 in Denmark, there has been a statutory order on physicians' notification of methicillin-resistant Staphylococcus aureus (MRSA). Occupational cases notified in North Denmark Region in 2008 and 2009 were analysed. Overall, 109 cases (54 females and 55 males) were notified, of whom 56 were infected and 52 cases were carriers, whereas in one case the status was unknown. The most prevalent clonal complex (CC) was 398 (n=26; 23.9%), followed by CC5 (n=17; 15.6%), CC30 (n=14; 12.8%), and CC8 (n=12; 11%). Eighteen cases were occupational with a predominance of CC398 (n= 16; 88.8%); CC8 and CC22 accounted for one case each. There was a significantly higher proportion of occupational cases for CC398 compared with other clonal complexes (p<0.001). All CC398 occupational cases were either farmers or farm workers occupied in swine confinement buildings. The two other cases were nurses working in the region's public hospitals. Most occupational cases were carriers (n=15; 83%). Three were infected, two with impetigo and one with tonsillitis; CC398 was the causative agent in all three cases. CC398 has a porcine reservoir which is huge in Denmark with a total annual production of 27,700,000 pigs. The presented population-based retrospective study shows an infectious potential of CC398 in humans. Close monitoring of future trends in prevalence, occupational distribution and pathogenicity is still warranted.