Who’s afraid of GBS?

This month, PLoS dedicates quite much attention to the topic of infection disease in newborns. A post written by Beth Skwarecki opens with the dilemma: good or not good? Which microbes do we have to combat and which we shouldn’t?

Excluding the usual big killers (from V. cholera to Campilobacter to EPEC etc…) there are plenty bacteria out there that threaten our health only sometimes, and researchers haven’t get their head around it yet. Such bacteria (some called pathobionts, to embrace their double nature in an utterly ugly name) colonize millions of us, at different location of the bodies and even at different time during development.

Take H. pylori, the stomach bug that made the news in the ‘90 as agent for gastric cancer. Convincing experiments (among which was drinking a flask of bacteria to prove the concept) showed that at least some variants of H. pylori cause peptic ulcers, a fastidious intestinal condition that, in the long run, may lead to cancer. Shocked? What about the fact that H. pylori colonize human beings from the beginning of human beings? We’ve just scratched the surface of why does this bacteria may or may not damage humans, and current medical guidelines aren’t too sure on what to do when they find H. pylori into you.

H. pylori electron microscopy. By Yutaka Tsutsumi, M.D. Professor Department of Pathology Fujita Health University School of Medicine [see page for license], via Wikimedia Commons

The most interesting controversy on bacteria and health comes from studies in newborns. This week, PLoS Medicine published a meta-analysis with the [rather not surprising] conclusion that if your mother is colonized with a bug that may damage you, you have greater risk to be infected. In the conclusion, the paper highlights the urgency to improve hygienization in pregnant women. That’s overall make sense and is supported by good evidence.

But hold on. One of the most discussed mother-to-child bacterial transmission (in the first world, at least) is Group B Streptocossus (GBS for friends), a bacterium that “colonize” (meaning habitat harmlessly) ¼ of women. Of these, 50% will transmit the bacteria to newborns. In some rare cases, such transmission become an infection: CDC counts 1.200 cases of “early onset of infection” in US per year, and 4-6% of them being lethal.

Streptococcus – by GrahamColm

It all sounds logic and solid to justify the use antibiotic during delivery to reduce GBS transmission. Such prophylaxis is adopted in US (I dunno in EU). But as GBS become the new HIV in terms of blocking mother-to-child transmission, the Cochrane consortium updates its systematic review on the matter, and nope: still no data support the idea that antibiotic treatment reduce overall mortality or mortality due to GBS infection. Though the author find a significant reduction of early-onset of infection by GBS, the trials (only three, with less than 1000 women in total) have high chance to be biased, the author said. A proper sized, randomized and double-blind controlled clinical trial is still missing on a now common medical practice.

To conclude, it’s strange that such extreme measurement to control against a rather rare event has failed to be tested for adverse effects, as on the other hand we know that natural microflora vertical transmission is beneficial to newborns, and antibiotic treatment inhibits colonization of all bugs, including the good ones.

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