Thursday, November 11, 2010

New NDM-1 Positive Super Bacteria On the Rise

The growing spread of multi-drug resistant pathogens has many people fearing potential epidemics


Posted by Alexandru Nicolae


It all started when a Swedish-Indian citizen traveled to India for a simple visit. In New Delhi, she developed a urinary tract infection by an antibiotic-resistant pathogen called Klebsiella pneumoniae. This new strain was resistant to a specific type of powerful antibiotic called carbapenem, a drug used as a last resort in fighting especially drug-resistant infections. As of November, 2010, many other forms of bacteria including strains of E-coli have been found to possess the same resistance, and they've appeared in places around the world. As of this date, 8 cases have been reported in Toronto, Canada (a long way from India indeed). How exactly are these bacteria foiling our greatest weapons against them?

Carbapenem is a broad spectrum beta-lactam antibiotic that's used to fight diseases like Klebsiella and E-coli when other forms of antibiotic are not working. They're highly resistant to beta-lactamases (bacterial enzymes that destroy beta-lactams) and so they've been extremely helpful in fighting certain infections. The trick that these new bacterial pathogens have up their sleeves is that the version of beta-lactamase they carry to fight our antibiotics is not the usual kind. The new form of the enzyme discovered recently is known as New Delhi Metallo - 1 (NDM-1), found in multiple bacterial species, it is a mutated version of the beta-lactamase enzyme. It exists on the surface coating of these bacteria and tears up any antibiotics that come near, thereby rendering them useless. Because of this unique ability, very few drugs are effective against bacteria carrying the NDM-1 enzyme; they are resistant to all antibiotics we posses with the exception of fluoroquinolones and colistin. To give you an idea of how powerful this defense is, fluoroquinolones are drugs normally used for chemotherapy! That is a scary thought.

The pathogens Klebsiella and E-coli belong to a family of bacteria called Enterobacteriaceae. They're commonly found in the human gut (that's normal in case you were wondering); however, some strains are pathogenic causing disease in humans, usually by producing various toxins that attack the body. The toxins cause illness, and in some cases, death.

According to one source, carbapenem-resistant Enterobacteriaceae isolated from hospital blood cultures have increased from 0% in 2006 to 8% in 2009. This is all before the discovery of the NDM-1-carrying bacteria, and so it is projected to grow. What's even scarier is that the genes responsible for producing NDM-1 may be transferable between bacteria. Going back to the Swedish patient we talked about earlier, the NDM-1 enzyme was in both the Klebsiella isolated from her urine and the E-coli found in her feces. This is worrying, and in my opinion may be linked to its quick spread around the globe.

We've been hearing about increasingly common antibiotic-resistant bacteria in recent years, If I recall correctly a new Tuberculosis strain was talked about in the States for some time. The reason the NDM-1 enzyme may have become so prevalent in the community in India could potentially be from the overuse of antibiotics in that country to treat infections, although it is by no means endemic to India. In the west we seem to be at least increasing our awareness about antibiotic resistance among pathogens, but how many of us still go to the doctor with illnesses not much worse than the common cold and ask for antibiotics to speed up the curative process? Mind you, colds are viral infections and will not respond to antibiotics.

This has the potential to develop into a serious community health issue if not properly addressed. Luckily health officials say there is no need for immediate alarm, the reported number of cases is still quite small. The best thing to do for the moment is to maintain proper hygiene and preventative methods. What are these preventative methods you ask? Good old hand-washing for the most part.

For now, we will have to wait and see what happens. Hopefully it never reaches the scale of an epidemic because of our early preparation.

The only bacterial cultures I want to hear about in the news from now on will be when they're talking about yogurt, I don't think I can stomach anything else.

References:

Yong D, Toleman MA, Giske CG, et cetera. (2009). Characterization of a New Metallo-B-Lactamase Gene, blaNDM-1 and a Novel Erythromycin...Antimicrob Agen and Chemother; 53(12):5046-5054.

Deshpande P, Rodrigues C, Shetty A, et cetera. (2010). New Delhi Metallo-b lactamase (NDM-1) in Enterobacteriaceae: Treatment options with Carbapenems Compromised. J of Assoc of Phys of India;58:147-150.

NDM-1 superbug cases rise in Canada. Yahoo Canada News. (click here for source)

Chen DK, McGreer A, Azavedo JC, Low DE. (1999). Decreased Susceptibility of Streptococcus pneumoniae to Fluoroquinolones in Canada. N Engl J Med; 341:233-239.

Bratu S, Landman B, Haag R, et cetera.(2005). Rapid Spread of Carbapenem-Resistant Klebsiella pneumoniae in New York City: A New Threat to Our Antibiotic Armamentarium. Arch Intern Med;165:1430-1435.

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