International research suggests people living near livestock or in livestock farming communities may be at greater risk of contracting anti-biotic resistant MRSA bacteria.

Researchers at the Johns Hopkins Bloomberg School of Public Health, Baltimore, the Dutch Institute for Public Health and the Environment (RIVM) and VU University Medical Centre in Amsterdam looked at the transmission of livestock associated MRSA, which accounts for 40 per cent of MRSA cases in the Netherlands. They found that the regional density of livestock populations had links to the spread of antibiotic resistant bacteria, and concluded that “regional density of livestock is an important risk factor for nasal carriage of livestock-associated MRSA.” The link is present regardless of whether a person has direct contact with animals or not.

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The bacteria examined in the study can cause a range of illnesses in humans, from minor to life-threatening skin, bloodstream, respiratory and urinary infections. It is especially infamous for causing complications after surgery in infected hospitals. The bacteria’s resistance to many first-line antibiotics makes it incredibly difficult to treat.

The researchers behind the study stressed that nasal carriage, the method of spread under examination, does not indicate that someone is infected with MRSA; instead it is associated with increased risks of eventual infection. Commenting on the increased collocation between antibiotic resistance and livestock farming, Dr Ellen Silbergeld one of the study’s authors, said, “In the past, MRSA had been largely associated with hospitals and other health care facilities, but in the last decade the majority of infections have been acquired in the community outside of a health care setting.”

In Europe, moves have been made to curb the overuse of antibiotics in farming in an effort to combat the growing problem of resistant bacteria. The European Commission has drawn up a 15-step plan to reduce antibiotic use and address the problem, though Danish authorities last week said other EU states must to increase efforts to combat resistance, when the country’s surveillance agency revealed domestic attempts to curb resistance in livestock populations were being undermined.

The US-Dutch study is the first to suggest the importance of indirect routes of transmission of livestock-associated MRSA, according to author Dr Jan Kluytmans, who said, “In the Netherlands livestock associated MRSA was first found in 2003 and was initially almost exclusively found in persons with direct contact to livestock. In recent years LA-MRSA is found with increasing frequency in community-dwelling individuals with no known contact with livestock. It is important to determine the routes of transmission outside of the farms since this may have important consequences for public health.”

The scientists found that, as the density of veal calves, pigs, or cattle doubled in a specific area, the odds of humans in the region carrying MRSA increased between 24 percent and 77 percent, depending on the animal. The international team examined data from the Netherlands to produce their study.  

The study’s authors concluded their work may have serious implications, not only for Europe, where measures to combat resistant bacteria in agriculture are underway, but also for the United States, where certain areas have incredibly high volumes of livestock farms, often with animals living in high densities. Dr Silbergeld elaborated, “Swine production is a significant industry in the Netherlands, but its density and scale are much less than in the United States. Future work should investigate the relationship between intensive livestock operations in the US and exposures to drug-resistant microbes including MRSA.”

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