During the past 25 years an increase in the prevalence of methicillin-resistant 
Staphylococcus aureus (HA-MRSA) was recorded worldwide. Additionally, MRSA 
infections may occur outside and independent of hospitals, caused by community 
associated MRSA (CA-MRSA). In Germany, we found that at least 10% of these 
sporadic infections are due to livestock-associated MRSA (LA-MRSA), which is 
initially associated with livestock. The majority of these MRSA cases are 
attributed to clonal complex CC398. LA-MRSA CC398 colonizes the animals 
asymptomatically in about half of conventional pig farms. For about 77%-86% of 
humans with occupational exposure to pigs, nasal carriage has been reported; it 
can be lost when exposure is interrupted. Among family members living at the 
same farms, only 4%-5% are colonized. Spread beyond this group of people is less 
frequent. The prevalence of LA-MRSA in livestock seems to be influenced by farm 
size, farming systems, usage of disinfectants, and in-feed zinc. LA-MRSA CC398 
is able to cause the same kind of infections in humans as S. aureus and MRSA in 
general. It can be introduced to hospitals and cause nosocomial infections such 
as postoperative surgical site infections, ventilator associated pneumonia, 
septicemia, and infections after joint replacement. For this reason, screening 
for MRSA colonization at hospital admittance is recommended for farmers and 
veterinarians with livestock contacts. Intrahospital dissemination, typical for 
HA-MRSA in the absence of sufficient hygiene, has only rarely been observed for 
LA-MRSA to date. The proportion of LA-MRSA among all MRSA from nosocomial 
infections is about 3% across Germany. In geographical areas with a 
comparatively high density of conventional farms, LA-MRSA accounts for up to 10% 
of MRSA from septicemia and 15% of MRSA from wound infections. As known from 
comparative genome analysis, LA-MRSA has evolved from human-adapted 
methicillin-susceptible S. aureus, and the jump to livestock was obviously 
associated with several genetic changes. Reversion of the genetic changes and 
readaptation to humans bears a potential health risk and requires tight 
surveillance. Although most LA-MRSA (>80%) is resistant to several antibiotics, 
there are still sufficient treatment options.