MRSA: What’s New?

Written on:June 26, 2011
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      Bacteria such as Staphyloccoccus aureus are constantly evolving, which is why methicillin-resistent Staphylococcus aureus (MRSA) exists in the first place. A new strain occurs when an existing bacterial strain undergoes a mutation. New strains of pathogens may develop new antibiotic resistances, become more or less virulent or infect new host species. In the case of a MRSA strain that was discovered by researchers in June 2011, the strain is different enough from the parent strain of MRSA that it is not detected by the tests currently on the market for detecting MRSA, called slide agglutination testing and polymerase chain reaction (PCR).

Researchers involved in this study collected samples from dairy cows that were suffering from mastitis, a bacterial infection that results in swollen, inflamed udders. Staphylococcus aureus commonly causes this condition in cows. The researchers determined that this was an infection of S. aureus, and the bacteria grew in the presence of methicillin, indicating that the strain was resistant to methicillin. Even though it was clear that a strain of MRSA had been found, PCR and slide agglutination testing were producing negative results for MRSA. Upon further investigation, the strain was found to be new and genetically different from known MRSA strains.The new strain of MRSA was later found in humans in several countries, including Denmark, Scotland and England. Scientists have determined that the new MRSA strain originated in cows and was then passed to humans. Epidemiological investigation is underway to determine how the strain may be transmitted from cows to humans and who is at risk for infection.In other news, concerns have been raised that some hospital-acquired cases of MRSA may be transmitted via bed bug bites. Bed bugs were largely eradicated for decades with the advent of modern sanitation, but there has been a drastic increase in bed bug infestation recently. The bed bugs were found to carry the drug-resistant bacteria that cause a MRSA infection, but it has not been conclusively shown that bed bugs are a vector of the infection that can spread the infection to humans. However, it is likely that they do, and this brings up concerns about pest control policies. Some pest control experts suggest the use of inexpensive systems for monitoring bed bug infestations so that outbreaks can be detected early and exterminated before they become a public health problem.In the United Kingdom, there is legal conflict between the company 3M and the government. The CEO of 3M has been accused of failing to market a device, called BacLite that can detect the presence of MRSA with a fluorescent light within five hours. This is considerably faster than existing testing methods, which typically take 48 hours or more. The BacLite device gained approval in 2006 and is used elsewhere in Europe, yet it has not been marketed in Scotland. Some consumer and health advocates are angry, believing that this device could potentially save the lives of people in an area in which MRSA outbreaks frequently occur. 3M countered that they did not think that device is effective and reliable enough to market.

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