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Dandruff is a very common scalp disorder that has occurred for centuries. A new study found that the most abundant bacteria on the scalp are Propionibacterium and Staphylococcus, and that they have a reciprocal relationship with each other - when one is high, the other is low. When compared with a normal scalp, dandruff regions had decreased Propionibacterium and increased Staphylococcus. The researchers suggested that these findings suggest a new way to treat dandruff - to increase the Propionibacterium and decrease the Staphylococcus on the scalp. Stay tuned for possible future treatments using these findings. From Science Daily:

Bacteria the yin and yang of dandruff, says study

Dandruff is not caused by a fungus, as many believe, but by an imbalance between two competing bacteria that naturally colonise the human scalp, according to a study released Thursday. Think of Propionibacterium and Staphylococcus as the yin and yang of healthy hair: when they hold each other in check, so too is dandruff held at bay. But when one dominates the other, the tell-tale white flecks that settle on shoulders like snowdust begin to proliferate, a team of Chinese and Japanese researchers reported.

Dandruff is the most common scalp disorder on the planet, a tonsorial bane for about half the world's population. But experts have differed sharply over the years on its causes and possible cures....A team anchored by Zhang Menghui of Shanghai Jiao Tong University isolated a large number of variables in the ecosystem of the human scalp to see how they interact. In 59 Chinese volunteers aged from 18 to 60 years old, they measured levels of water, several dozen bacteria, sebum—an oily secretion that proliferates in adolescence and early adulthood....Participants washed their hair 48 hours in advance of the tests, and dandruff samples were taken from eight different sections of the scalp.

"Overall, fungi did not exhibit an important role in the severity of dandruff," they concluded.
"The relationship between the bacteria and the dandruff was significantly stronger."
But the scientists also noticed that prevalence of the pesky white particles was higher when the ratio of two dominant bacteria—which normally cancel each other out—was altered. "This study suggests that adjusting the balance of the bacteria on the scalp... might be a potential solution to lessen dandruff," they concluded.










Amazing persistence of the restroom microbial community.From NPR news:

What Microbes Lurked In The Last Public Restroom You Used?

The invisible world of the bathroom isn't pretty — unless you're a microbe. After scanning the microbial zoo of four public restrooms recently, a team of researchers found a diverse swarm of characters that persisted for months despite regular cleaning of the facilities. The goal of the study, published in the December issue of Applied and Environmental Microbiology, was to better understand how communities of bacteria and viruses can shift in these very public places across a couple of months.

To get their down-and-dirty readings, the researchers selected four bathrooms at San Diego State University... They checked two women's restrooms and two men's restrooms (a high-traffic and a low-traffic bathroom for each gender). The bathrooms were thoroughly cleaned at the study's start with bleach solution, which killed any existing germ communities.Then, during the following hours, days, weeks and months of human use, the researchers periodically swabbed soap dispensers, floors and toilet seats in all four restrooms for microbe samples. 

Within one hour of sterilization, the bathrooms were completely recolonized with microbes — just as plants rapidly arrive and populate a newly emerged island. Fecal bacteria dominated, including on toilet seats and on soap dispensers — about 45 percent of the bacteria there were of fecal origin.

In all, the scientists found genetic traces of more than 77,000 distinct types of bacteria and viruses. (At least some of those species were likely dead or dormant, the scientists add; genetic testing detects them all, whatever their status.)

Patterns of regrowth and succession, as some species waned and others replaced them, were surprisingly similar from bathroom to bathroom; within just five hours the population mix in each room stabilized.

When the team tried growing cultures from different surfaces in each room, they found one set of live bacteria in overwhelming abundance: Staphylococcus. Staph's persistence in these studies points to its power as a potential pathogen, Gilbert says. Various versions are common on human skin and inside the nose and other orifices; they generally cause no problems, or trigger only minor skin infections. But staph infections can be serious, or even kill, if the bacteria get into bloodstream, joints, bones, lungs or heart

Gilbert notes that none of the live Staph strains detected in the San Diego bathrooms showed signs of being antibiotic resistant. They were instead relatively harmless "skin bugs that happened to have lost their skin," he says. The team did find genes from MRSA hiding on the floor, as well as traces of some troublemaker viruses, including HPV and herpes virus.

Interestingly, although restrooms that were left open for use for up to two months were cleaned regularly with soap and water, the communities of microbes found there remained relatively unchanged for the full eight weeks of the study.

No need to be scared or grossed out by that finding, Gilbert says..."All human environments contain pathogens — your bedroom, the phone you're talking on, even the bugs inside of you could turn pathogenic at any time," Gilbert tells Shots. "But we desperately need them in our lives." Having a healthy community of good — or even just neutral — microbes can crowd out the bad ones. As we've learned from using broad-spectrum antibiotics in the human body, "sterilization is not necessarily good," he says. "Bacteria come back right away, and they might come back perturbed."


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