In a very good article, USA TODAY describes how hospitals across the US are fighting a “Superbug” war. What is a superbug? It is a bacterium that has gained the ability to be resistant to almost all available antibiotics. The article discusses CRE bacteria. In class I have discussed the NDM-1 plasmid which encodes an enzyme called carbapenemase, which cleaves carbapenam antibiotics (which up until now had the been the antibiotic of last resort for extensively resistant bacteria). Both CRE and NDM-1 are not examples of specific bacteria, but of genes that can transfer resistance to a wide array of bacteria. Any bacterium containing the genetic information would be resistant. Examples are that both E. coli and Klebsiella pneumoniae are identified as CRE bacteria.
How does this happen? The animation in the USA Today story is perfect. We take an antibiotic that a SINGLE bacteria may be resistant to. Then, that one bacterium can do one of two things. They can simply grow to fill in the spaces left by the sensitive bacteria, or they can use horizontal gene transfer to transfer antibiotic resistance to other bacteria that hadn’t been antibiotic resistant. Horizontal gene transfer is the ability of bacteria to share genetic information with other bacteria in a population. (Vertical gene transfer is what happens normally when a bacterium divides and replicates it genetic information for its daughter cells). The animation details horizontal gene transfer with both transposons transferring resistance as well as conjugative plasmids via conjugation.
In class, we discuss that once a bacterium gains a conjugative plasmid, it WANTS to share the information with other bacteria. This can create an entire army of bacteria that are superbugs. Where is the best place for this to happen? The human gut is a great place for bacteria to get together and exchange information.
How quickly can this spread? According to the article:
the first known case, at a North Carolina hospital, was reported in 2001, CREs have spread to at least 41 other states
The NDM-1 was first identified in Swedish patient who had visited India for surgery in 2008 and bacteria containing this plasmid has been found in:
India, Pakistan, the United Kingdom, the United States,Canada,Japan and Brazil.
Currently, CRE and NDM-1 bacteria are found primarily in hospital settings. But the concerns are that, similarly to MRSA, these organisms will become more common outside the hospital among the general population, creating a serious healthcare problem that won’t…can’t…be treated with any currently antibiotic therapy.