The Friendliest Deadly Bacteria

Researchers might have figured out how the leading cause of hospital infections in the United States is able to adapt to even our last line of antibiotics. It seems that methicillin-resistant Staphylococcus aureu, or MRSA for short, is really good at getting along with other bacteria.

Clonal cluster 5, or CC5, is the predominant strain responsible for most of the infections caused by MRSA. On 12 different occasions since 2002, CC5 has been able to successfully resist treatment using vancomycin, the last line of defense against a bacterial infection. Needless to say, it has no problem with the family of antibiotics derived from penicillin.

The CC5 bacteria studied all lacked an operon, or a set of genes known as bsa. Bsa allows bacteria to produce lantibiotic bacteriocin - basically an antibiotic made by bacteria as a defense against other bacteria. What this means is that CC5 strives to co-exist with other bacteria in mixed infections instead of trying to fight them off. This leads to the CC5 bacteria picking up genes from other random bacteria, and once in a while they acquire resistance to vancomycin.

What the CC5 has in place of the genes for their bacterial antibiotic is a set of genes for enterotoxins. These are human-attacking proteins that while attacking the human host, make it easier for other bacteria to grow in the infection.

All of this adds up to a bacterium that is very conducive to the kind of primordial soup that bacteria thrive in. Not only do they co-exist with other bacteria, they also learn from them, and in return, make infecting humans easier.

The biggest red flag is that MRSA thrives in hospitals, where thousands of other pathogens exist alongside sick humans. Were CC5 to gain a foothold outside of the hospital, the repercussions would be disastrous, considering that even our strongest antibiotic cannot defeat it.

In efforts to curb newly emerging "super strains," doctors strongly advise to finish a medication all the way through, even if one is feeling better halfway down the bottle. Even if one doesn't feel sick, the bacteria could still be living somewhere inside, threatening a relapse or infection of another person.