Antibiotic resistance: Bugs and drugs…

Jim Caryl at Gene Gym is laboring to make antibiotic resistance understandable by the lay public. In Jim’s post Bugs and drugs… he explains the various resistance mechanisms, and in particular “The worrying cocktail” which we must do everything we can to avoid. This is why the emergence of NDM-1 is a potential nightmare:

(…) Thus what the NDM-1 report (raised in my last post) describes is a heady cocktail ripe for troubled times:

Ecological contact + promiscuous mobile genetic elements + multidrug resistance = not good. These tick all the boxes for a situation that should be carefully monitored, as you would any invading pest species in a zoological sense.

In the previous post Future-proofing antibiotics… Jim attempts the optimist’s perspective on Tim Walsh’s NDM-1 study. He links five commentaries on the Walsh study. One of more accessible of these is by microbiologist Hugh Pennington:

(…) A paper describing this new enzyme was published last September. It is full of technical molecular detail, but it uses plain English to say things that send shivers down the spine. The Klebsiella carrying the new gene was fingerprinted to find its type. It was ST14, a type almost identical to ST 15, which is branded as being the “new MRSA” due to its wide international distribution and carriage of other antibiotic resistance markers. So the Klebsiella was already particularly good at spreading and travelling long distances.

Just as unsettling was the finding in stools from the patient of a strain of Escherichia coli that was also carrying the NDM-1 gene. It was on a plasmid, a small DNA structure that can transfer quite easily from bacterium to bacterium. It is very likely that it had jumped from the Klebsiella to the Escherichia while they were living quietly in the patient’s bowels (vice versa is possible, but the practical consequences would be no different).

The original Klebsiella plasmid carried other antibiotic resistance genes as well. No surprise there; they often do. So more bad news. The paper doesn’t mince its words: “The rapid dissemination of this plasmid throughout clinical bacteria would be a nightmare scenario.”

(…) The nightmare scenario is that NDM-1 producers are close to becoming true superbugs that are resistant to everything. The horror model is XDR-TB – extensively drug-resistant tuberculosis, which broke out in South Africa in 2006, and is a significant problem in Russia, among other regions. It is reasonable to say that such strains, which for all practical purpose are so hard to treat that sufferers from them might as well be living in the 1930s, have evolved because of poorly controlled anti-TB drug prescribing. The same is true for the prescription of antibiotics in the Indian subcontinent. But it is hard to see changes coming there any time soon. Even in the UK we could do better. And hoping for new antibiotics remains just that.

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