Humans carry more antibiotic-resistant bacteria than animals they work with

26-Aug-2015 - USA

Antibiotic-resistant bacteria are a concern for the health and well-being of both humans and farm animals. One of the most common and costly diseases faced by the dairy industry is bovine mastitis, a potentially fatal bacterial inflammation of the mammary gland (IMI). Widespread use of antibiotics to treat the disease is often blamed for generating antibiotic-resistant bacteria. However, researchers investigating staphylococcal populations responsible for causing mastitis in dairy cows in South Africa found that humans carried more antibiotic-resistant staphylococci than the farm animals with which they worked. The research is published in the Journal of Dairy Science

"South Africa has one of the highest HIV/AIDS and tuberculosis rates in the world and the human health risk to immune-compromised individuals is therefore that much greater," explained lead investigator Tracy Schmidt, a PhD candidate at the Department of Medical Microbiology, University of Pretoria. "The rise of livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) and reported cases of bacterial transmission between dairy cows and humans has raised concerns from both the agriculture/veterinary sector and public health officials. The lack of data about the occurrence of LA-MRSA in South Africa and the need to investigate possible reservoirs were part of the motivation for this work."

This research in the KwaZulu-Natal province of South Africa investigated the diversity of Staphylococcus populations responsible for IMI in dairy cows and assessed the susceptibility of different species to antimicrobials commonly used in the veterinary field as well as human medicine. At the same time, individuals working in close contact with the animals were sampled and the diversity and susceptibility profiles of staphylococcal isolates determined and compared with isolates of animal origin.

With respect to staphylococcal diversity the results showed the clear predominance of Staphylococcus chromogenes, while Staphylococcus epidermidis was the isolate most commonly recovered from the human specimens.

The study found a relatively low occurrence of antimicrobial resistance among the bovine staphylococci. "This is encouraging as it indicates the responsible usage of antimicrobials within local dairies and provides our veterinary practitioners and animal owners valuable information going forward with respect to the treatment of infected animals," commented Schmidt. None of the staphylococcal isolates of bovine origin were found to be resistant to methicillin. Furthermore, all isolates tested negative for the presence of vancomycin-encoding genes - vancomycin being one of the front-line antimicrobials used for the treatment of methicillin-resistant staphylococcal infections in humans. The results indicate the low potential health risk posed to close contact workers and milk consumers through exposure to antibiotic-resistant staphylococci originating from milk.

"Of greatest interest was the extensive antimicrobial resistance noted among the coagulase-negative staphylococci of human origin. Multidrug resistance was common among isolates, and due to the propensity for staphylococci to acquire antimicrobial resistance through genetic exchange, human staphylococci can be regarded as a potential reservoir of resistance genes," added Schmidt.

https://www.bionity.com/en/news/154258/humans-carry-more-antibiotic-resistant-bacteria-than-animals-they-work-with.html