An emerging subtype of methicillin-resistant Staphylococcus
aureus (MRSA), clonal complex (CC) 398, is associated
with animals, particularly pigs. We conducted a
matched case–control and a case–case study comparing
21 CC398 case-patients with 2 controls randomly selected
from the Danish Civil Registry and 2 case-patients infected
with MRSA other than CC398. On farms of case-patients,
animals were examined for MRSA. Thirteen case-patients
reported pig exposure. Living or working on farms with animals
was an independent risk factor for CC398 in the case–
control (matched odds ratio [MOR] 35.4, 95% confi dence interval
[CI] 2.7–469.8) and the case–case study (MOR 14.5,
95%CI 2.7–76.7). History of hospitalization was associated
with an increased risk only in the case–control study (MOR
11.4, 95% CI 1.4–94.8). A total of 23 of 50 pigs on 4 of 5
farms were positive for CC398. Our results, corroborated by
microbiologic testing, demonstrate that pigs are a source of
CC398 in Denmark.