In spite of the positive name, a probiotic can sometimes exhibit a dark side, one with less than healthy results for the host.
One recent occurrence saw an 11 month old female with trisomy 21 develop a “respiratory syncytial virus (RSV) bronchiolitis with bacterial super-infection secondary to administration of Lactobacillus rhamnosus.” Read the abstract here.
Lactobacilli are the good guys. Usually. Switching sides is why caution must be used in supplementing in vulnerable populations.
Probiotics are interesting. Take Streptococcus pneumoniae. These bacteria cause most cases of pneumonia. But many of us host these colonies but never get sick. Our immune systems keep S. pneumoniae under control. Other probiotic colonies jump in to crowd them out.
But go without sleep, cave in to chronic stress, or deplete your immune defenses with disease or its treatment, and the mighty strep is ready to conquer.
Other streptococci can go both ways. Normal conditions may have them as vital members of the microbiota. They may produce bacteriocins which double as antibiotics. But then may become aggressive if given a chance.
Back to Lactobacillus rhamnosus, the alleged cause of the bronchial infection in the baby girl. This is a common bacterium in yogurt and other fermented foods. It has been extensively studied. Many strains have been shown to have positive effects in a wide array of diseases and conditions. Yet a bronchial infection is decidely negative.
Caution must prevail. We obviously don’t know everything.