#Microbiotiful - Under the nails

Sound familiar? The family next door is alright; you get along with them most of the time. Well, except for ... that’s what you could say about staphylococci. These bacteria like to live on the skin and mucous membranes of humans but usually don’t cause problems, with Staphylococcus epidermidis being a prominent example. Staphylococcus aureus, however, is different. Don’t be fooled by its good looks—golden-yellow colonies, hence "aureus" ("gold" in Latin). This species is a major cause of food poisoning and dangerous infections worldwide, particularly among people with a weak immune system. Staphylococcus capitis is a coagulase-negative species (CoNS) of Staphylococcus. It is part of the normal flora of the skin of the human scalp, face, neck, scrotum, and ears and has been associated with prosthetic valve endocarditis but is rarely associated with native valve infection.

Corynebacterium is a very irregularly shaped bacteria. Some look like the letter V under the microscope, others like a club (hence the name, coryneform means "club-shaped"). The species C. diphtheriae and C. ulcerans can cause diphtheria, a potentially deadly disease if the bacterial cells are themselves infected by a specific virus that prompts them to produce a toxin. Pet dogs can carry corynebacteria into the house, so it’s a good idea to wash your hands after contact—as is, of course, to regularly get your booster injections that should keep you immune.

Several million bacteria are typically attached to the toothbrushes we use, and Micrococcus species feature in great numbers. In fact, they’re basically on all our household objects, from furniture to light switches to the cutlery waiting to go into the dishwasher. No prizes for guessing how they get there—we spread them ourselves. Micrococci form a significant part of our skin’s natural microflora. Luckily they rarely cause us problems, with the possible exception of converting components of the sweat on our bodies and in our clothes into something awfully smelly.  

Species of the mold Cladosporium grow best where it is damp, dark and warm, like in the human intestine. They are abundant throughout nature (except in the polar regions). At least some level of Cladosporium is encountered in just about every household as whenever you open the window, the spores get blown in. Not that this is necessarily a problem—Cladosporium are rarely pathogenic to humans. They are, however, significant allergens and can affect people who suffer from asthma or respiratory diseases where they occur in great numbers.

Normal harmless microorganism. But when the bacillus finds itself locked in a comedone, it infects the pimple, causing inflammation, which gives it a red color, which often makes it take more volume.

Malassezia, sometimes also called Pityrosporum, is the name of a genus of yeast1 of the Fungi imperfecti group, sometimes part of the natural commensal flora of humans (ex Malassezia furfur is present in almost 100% of the population) and of various animals (cats, dogs, and many other mammals).

Trichosporon is a genus of anamorphic fungi in the family Trichosporonaceae. All species of Trichosporon are yeasts with no known teleomorphs (sexual states). Most are typically isolated from soil, but several species occur as a natural part of the skin microbiota of humans and other animals.