… Starting in the early 1960s, Gorbach had worked with the dairy industry to identify the most healthful kinds of milk-digesting bacteria.  In particular, he was interested in finding strains and species that could take up lasting residence in the human colon.  Over twenty years of research, however, he failed to find anything remotely tenacious among the bacteria in American, European, or Asian dairy cultures.  Though most live food bacteria perish in the acid bath of the stomach, many of these milk-digesting bacteria reached the colon alive.  Nonetheless, they disappeared within a day or two.

            Then in 1983, Goldin joined Gorbach’s lab team, and the two men decided to abandon research on dairy bacteria and, instead, search for beneficial lactobacilli in the human digestive tract.  Their new track required the cooperation of fellow scientists, family, and friends, from whom Goldin cajoled donations of stool.

            As they began screening this harvest, Gorbach and Goldin drew up a wish list of desirable traits.  The ideal candidate for a probiotic supplement, they decided, would consistently survive a bath of stomach acid and intestinal bile, adhere strongly to a column of laboratory-cultured intestinal cells, and be able to elbow its way around a petri dish filled with normal intestinal bacteria such as E. colim as well as more dangerous gastrointestinal bugs such as salmonella.

            In the spring of 1985, they isolated a bacterium that scored reasonably well on all three tests:  Lactobacillus GG, now sold as the nutritional supplement Culturelle.  In the two decades since this strain’s discovery, Gorbach, Goldin, and many others have published more than a hundred scientific papers demonstrating its benefits, most clearly its ability to help prevent and relieve gastroenteritis, the intestinal irritation and inflammation that can result from either infection with a gastrointestinal bug or the microflora-disruption of antibiotics.

            Beyond the intestinal tract (if only by an inch), probiotics are also proving their ability to protect against common vaginal and urinary tract infections and reduce the risk of sexually transmitted disease.  In the early 1970s, Canadian urologist Andrew Bruce showed that women who get recurrent vaginal and urinary tract infections tend to have stray E. coli in their vaginas, while the vaginal microflora of women who seldom if ever get these infections consist of a select group of lactobacilli.

These lactobacilli appeared to aggressively discourage the incursion of interlopers from the nearby intestinal tract.  An abundance of follow-up studies confirmed that a healthy vagina was one dominated by lactobacilli.

In the 1980s, Gregor Reid, of the University of Western Ontario, furthered Bruce’s work with a search for a vaginal equivalent to Lactobacilus GG.  Like Gorbach and Goldin, Reid found that dairy lactobacilli such as L. acidophilus didn’t have the right stuff to take up residence where he wanted them.  Nor did Lactobacillus GG.  He began collecting bacterial swabs from the vaginas of women who hadn’t experienced a vaginal or urinary tract infection in several years.  From hundreds of possible candidates, he identified two strains that strongly repelled intestinal bacteria in the lab.  Lactobacillus rhamnosus G-I and L. fermentum RC-14 beat back would-be competitors with an abundance of hydrogen peroxide and a variety of biosurfacants (slippery molecules that make it hard for other bacteria to get a grip).  These two lactobacilli had the added advantage of not being fazed by spermicides, which have a nasty tendency to raze vaginal bacteria and so pre-dispose to infections.

In testing his probiotic, Reid followed the health of more than a hundred women who either swallowed a capsule of the supplement or inserted it as a vaginal suppository.  In either case, the bacteria in the probiotic reach a woman’s vaginal tract, become the predominant residents there, and so restore the kind of lactobacilli microflora associated with resistance to infections.  And in a study with forty women suffering from bacterial vaginosis, the probiotic proved itself a more effective cure than the standard treatment of metronidazole antibiotic gel.  Vaginal flora returned to normal in eighteen of the twenty women taking the probiotic, a cure rate of 90 percent.  By comparison, metronidazole cured just over half – eleven out of twenty women.  Reid published the results of the small clinical trial in 2006, the same year that his probiotic debuted in U.S. and Canadian health food stores as FemDophilus.

Unfortunately, for every scientifically tested probiotic standing on the shelves of vitamin shops and drugstores, there are dozens of outwardly similar products filled with dubiously useful and sometimes mislabeled organisms.  Most are probably harmless.  But some contain antibiotic-resistant bacteria – a huge concern to microbiologists who understand how readily resistance genes can spread from a probiotic to a person’s intestinal microflora and from there to disease-causing organisms.  Some probiotic companies go so far as to tout the antibiotic resistance of their products.

PRESCRIPTION PROBIOTICS

            As a young doctor in the early 1980s, Kristian Roos often puzzled over the stubbornly recurrent strep throat infections that plagued many patients at Sweden’s Gothenburg University Hospital.  Some patients turned up in his clinic several times a year, their flame-red tonsils and throats speckled with white patches.  Roos knew that around a quarter of us continue to harbor Strepctococcus pyogenes in our throats even after antibiotic treatment knocks back its numbers enough to stop active infection.  This persistence partially explained why some people remain predisposed to reinfection.  But it didn’t explain why some, but not others, become persistent carriers.

            Could it be that Strep. pyogenes faced less competition in the throats of tonsillitis-prone patients than it did in those who remained healthy?  In 1985, Roos took the helm of the ear, nose, and throat clinic at Gothenburg’s Lundby Hospital, where he had a better chance of answering this question.  At Lundby, Roos would see more of the routine infections that interested him.  Just as important, the clinic’s regular schedule of wellness checkups gave him the chance to take throat swabs from the healthy as well as the sick.

            Sure enough, Roos found that while most people have an abundance of harmless alpha-streptococci in their throats, those who carried Strep. pyogenes tended to have little to none.  Perhaps the “good” strep were literally keeping their troublesome cousin in check.  The experience of one family backed up Roos’s hunch.  After the youngest child developed a chronic Strep. pyogenes skin infection, the mother began suffering recurrent strep throat.  Strain typing showed that the exact same substrain infected them both, but the boy never developed tonsillitis.  The difference, Roos found, was that the boy carried massive amounts of alpha-streptococci in his throat, while his mother lacked them entirely.

            Roos and several colleagues began studying the many kinds of streptococci bacteria that grew in the throats of the healthy.  By 1995, they had packaged several of these bugs into a throat spray.  In a preliminary study, patients being treated for strep throat received either the probiotic mix or a dummy saltwater spray to use daily for a week after finishing their antibiotics.  Over the next nine weeks, only one of the 51 probiotic users suffered a second bout of strep tonsillitis, compared with 14 of the 61 patients who used the placebo – a tenfold difference in lasting cure.  In a larger study of 342 patients followed for over ten weeks, the difference proved less dramatic but significant:  tonsillitis returned in less than 20 percent of those who spritzed their throats with the live alpha-strep bacteria, compared with 30 percent of those who got the saline spray.  At the end of the study, those using the probiotic were also half as likely to silently carry Strep. pyogenes in their throats as were those who received the placebo.

            While he was hoping and waiting for a pharmaceutical company to develop his probiotic throat spray, Roos began wondering whether a lack of protective bacteria might likewise contribute to the recurrent ear infections that plague so many toddlers.  Stray throat bacteria cause these infections when they become trapped inside a child’s middle ear chamber.  Knowing that some throat bacteria cause more ear trouble than do others, Roos began looking at what lived in the upper throats of healthy children.  In the process, his research team amassed a collection of some six hundred kinds of alpha-streptococci, which they tested and ranked according to their ability to inhibit the four kinds of bacteria that most frequently turn up inside children’s infected ears:  Streptococcus pneumoniae, Haemophilus influenzae, and to a lesser extent, Strep. pyogenes and Moraxella catarrhalis.

            In 1996, Roos packaged the five most ear-protective bacteria into a nasal spray, which he gave to the parents of toddlers with a history of chronic infection.  In a study of 108 children, half received the probiotic spray once daily for ten days, half received squirts of salt water.  At the end of three months, nearly half of those who got the probiotic remained free of ear infections.  The same could be said of less than a quarter of those who got the dummy spray.