New Super Bugs

I’ve written here a few times before about the development of antibiotic resistance in bacteria, and many people will have heard about infections caused by methicillin-resistant Staphylococcus aureus (MRSA).   The New York Times now has a report that a new class of antibiotic-resistant organisms is being encountered in hospital settings.  These organisms fall into a broad class of bacteria that are known as Gram negative, because they do not absorb a crystal violet dye used in the Gram staining procedure.  (This is not just an esthetic curiosity.  The two classes of bacteria behave differently because the structure of their cell walls is different.)  Although these infections are, at this point, nowhere near as common as those resulting from MRSA infection, they are potentially a grave threat, because there are very few treatment options available.

…there are several drugs, including some approved in the last few years, that can treat MRSA. But for a combination of business reasons and scientific challenges, the pharmaceuticals industry is pursuing very few drugs for Acinetobacter and other organisms of its type, known as Gram-negative bacteria. Meanwhile, the germs are evolving and becoming ever more immune to existing antibiotics.

Vancomycin, for example, is a very powerful antibiotic that can be used to treat some MRSA infections, but it is not effective at all against Gram-negative organisms.   One of these bacteria, Acinetobacter baumannii, can cause severe infections of the urinary tract and the bloodstream.  Another, Klebsiella pneumoniae, which has been increasingly found in hospitals, can (as its name suggests) cause a serious pneumonia.

When a patient is diagnosed with one of these infections, the treatment options are severely limited.

Doctors treating resistant strains of Gram-negative bacteria are often forced to rely on two similar antibiotics developed in the 1940s — colistin and polymyxin B. These drugs were largely abandoned decades ago because they can cause kidney and nerve damage, but because they have not been used much, bacteria have not had much chance to evolve resistance to them yet.

Sometimes the trade-off is dire: the patient may be forced to run a high risk of kidney failure in order to treat the infection.

The introduction of antibiotics made such an enormous difference in the treatment of infections that it is hard to conceive of how dangerous they once were.  It has been very rare, in the recent past, for patients to die from infections if they had any sort of competent medical care.  If we succeed, through our own stupidity and carelessness, in making antibiotics less effective, we will get reminded that infections are serious much more quickly than we would like.

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