Suspected transmission and subsequent spread of MRSA from farmer to dairy cows.

In the present study we describe an outbreak where PVL positive MRSA belonging to spa-type t002 and multi-locus sequence type ST2659 persisted in a Swedish dairy herd for at least two years, despite efforts to hinder transmission between animals and between the farmer and his animals. This is the first description of persistence and spread of MRSA in a dairy herd in Sweden. Sampling of animals in the herd was initiated by the finding of MRSA in the farmer and was performed at eight occasions from November 2012 to September 2014. In total, MRSA was detected in 25 animals and in 16 of these MRSA was detected in milk samples. In addition, MRSA was also detected in bulk milk samples. Whole genome sequencing (WGS) of twelve isolates from farmer (n = 1), animals (n = 9) and bulk milk (n = 2) revealed high relatedness, implying a common source. MRSA may initially have been transmitted from humans to cows with further spread within the herd. WGS showed minor differences in one isolate (loss of phage ΦN315) which could indicate adaption of the strain to an animal host.

Preventing introduction of livestock associated MRSA in a pig population--benefits, costs, and knowledge gaps from the Swedish perspective.

Antibiotic resistance is a growing concern in human, as well as in veterinary medicine. Part of the problem concerns how to respond to the risk presented by animal reservoirs of resistant bacteria with the potential of spreading to humans. One example is livestock associated methicillin-resistant Staphylococcus aureus (LA-MRSA). In countries where LA-MRSA is endemic in the pig population, people in contact with pigs have a higher risk of being colonised with LA-MRSA, and persons from this group are subjected to precautionary measures when visiting health care facilities. In the present study, it is assumed that, if LA-MRSA was introduced to the Swedish pig population, the prevalence in the risk groups would be the same as in Denmark or the Netherlands (two countries with low human prevalence that have implemented measures to detect, trace and isolate human LA-MRSA cases and, therefore, have comprehensive data with good coverage regarding prevalence of LA-MRSA), and that similar interventions would be taken in Swedish health care facilities. It is also assumed that the Swedish pig population is free of MRSA or that the prevalence is very low. We analyse if it would be efficient for Sweden to prevent its introduction by testing imported live breeding pigs. Given that quarantining and testing at import will prevent introduction to the pig population, the study shows that the preventive measures may indeed generate a societal net benefit. Benefits are estimated to be between € 870 720 and € 1 233 511, and costs to € 211 129. Still, due to gaps in knowledge, the results should be confirmed when more information become available.