December 2008 Archives

The care of the critically ill is full of Catch-22s. Mechanical ventilators deliver life-saving oxygen to failing lungs. But the same intubation introduces bacteria to cause ventilator-associate pneumonia. Worse, in a hospital setting, those bacteria often include some of the world's nastiest, drug-resistant pathogens. In an effort to beat back this threat, nurses wash out patients' mouths with the potent antiseptic chlorhexidine. But that, in turn, tends to ipe out all the patient's mouth bacteria--both good and bad--opening up territory for more drug-resistant hospital bugs to move in. Even scarier hospital, strains of methicillin resistant Staphylococcus aureus (MRSA) are proving increasing resistant to this disinfectant

Now, in the spirit of "if you can't beat 'em ...," doctors at Sweden's Lund University Hospital are deliberately inoculating their patients with "good germs." Specifically, anesthesiologist Bengt Klarin and colleagues are swabbing the mouths of critically ill, intubated patients with a well-studied strain of Lactobacillus plantarum--a normal resident of healthy mouths and the active ingredient in sauerkraut and many other fermented foods.

The probiotic bacteria prevented infection as well as did standard disinfection with chlorhexidine. Using L. plantarum also avoided such common chlorhexidine side effects as mouth irritation and potentially deadly allergic reactions the researchers report.

Here's the full report, in last month's issue of Critical Care. 

A somewhat belated notice: John Maciel, host of the Waterloo, Ontario, talk radio program KW Magazine, has invited me to join him on air this evening between 6 pm and 7 pm Eastern. We'll be talking about Good Germs, Bad Germs. You can listen live online or, if you're in southern Ontario, tune in to FM 98.5 CKWR. I love to hear from listeners. Thanks. JSS

Dubbed AAD, for antibiotic-associated diarrhea, the problem results when antibiotics raze the normal complement of digestive bacteria that live in our intestines. These bacteria not only help us digest our food, they actively protect us from would-be invaders such as the bugs that cause food-poisoning (salmonella, shigella, campylobacter, et al) and colitis (Clostridium difficile, Klebsiella oxytoca, and kin). They also play less-understood roles in regulating immunity and other aspects of our physiology (including fat storage).

(Salmonella on otherwise-barren gut epithelial cells, courtesy the NIH.)

To get an ecological picture of the disruption, researchers at California's Stanford University and Cape Cod's Marine Biological Laboratory used a bacterial-DNA tagging technique to take a before- and after-antibiotic gut census, with the help of three volunteers on a five-day course of Cipro (ciprofloxacin). One of today's most widely used antibiotics, Cipro is considered relatively benign in its gut effects.

Still, by the end of the five days, the Cipro had produced wholesale changes in the abundance of about a third of the approximately 4,000 types of bacteria that had established a stable ecosystem in these three human guts.

None of the three volunteers reported any digestive problems through the brief trial--a finding the researchers took as confirmation of the general redundancy in our gut microflora. i.e. When some species get razed, others can generally pick up the slack. Moreover, the volunteers' gut "ecosystems" had more or less returned to normal by the four-week mark, though a few obscure species never reappeared or remained at abnormally low levels.

These exceptions may suggest that we need to know more about the lasting effects of antibiotics on our intestinal milieu. For example, the researchers note that increased risk of kidney stones results when the gut loses its complement of oxalate-degrading bacteria. The best known of these is Oxalobacter formigenes--a bug that's abundant in children, but which tends to disappear by adulthood (at least in the developed world). The disappearance has generally been attributed to O. formigenes' susceptibility to many commonly used antibiotics.

Here's the full study at PloS Biology.

Okay, you insomniacs looking for something to put you to sleep... and anyone simply craving more of my writing (anyone?): I've posted a dozen or so previously published feature stories that originally appeared in Popular Science, Discover, and National Wildlife magazines. I backdated most of them. So they don't show up under "recent postings." For a full title list go to this site's semi-hidden archives page. Knock yourself out.