Can You Tell a Donut from a Coffee Cup? Exploring Bacteria Concentration on Skin

[chound]

How do you take bacteria from skin and which is the part most concetrated with them?

 

[daveb]

A simple skin scraping works wonders, or even a swab depending on where you take the sample. I'm no expert, but I would assume the highest concentration would be in areas of high humidity (the toes, groin area, etc.) The armpits would probably be a problem if a lot of anti-bacterial underarm deaodorant is used.

 

[Ouabache]

Also going along with daveb's idea of skin areas of high humidity, inside your mouth and anus, both have high concentrations of bacteria. You might even try inside the folds of skin of your bellybutton. You typically sample those areas with a cotton swab and apply to suitable media in a culture plate or slant.

That reminds me of an interesting comment related by a bio professor; the surface inside your mouth (throat, esophagus, stomach, intestines) to your anus, it is considered external to your body. It is continuous with your skin in a cylindrical path through your body, one continuous integument.

 

[Math Is Hard]

That reminds me of an interesting comment related by a bio professor; the surface inside your mouth (throat, esophagus, stomach, intestines) to your anus, it is considered external to your body. It is continuous with your skin in a cylindrical path through your body, one continuous integument.

Now there's something interesting to throw in with the old joke about the topologist who can't tell a donut from a coffee cup!

 

[Curious3141]

Sampling skin for bacteria can be done as simply as touching a sterile agar plate with your finger (then streaking it out).

This basic method, is, in fact, used in some hospital infection control studies to evaluate the magnitude of skin bacterial carriage, where health care workers press their palms against agar plates.

Another, more complete method to do the same, is to rinse your hand (or other body part) in a broth suited for bacterial growth contained within a sterile bag. The broth can then be examined for turbidity and subcultured to determine colony counts and bacterial types.

Medically, the most commonly used method on the intact skin or superficial wounds of patients is to take a sterile swab and sample the area with the tip. This swab is then either rubbed on a plate or immersed in a broth (or both) and culture is carried out.

Skin scrapings are used more often for fungal isolation since the hyphae are imbedded in the outer layers of the skin. Bacterial isolation does not require this measure.

The entire skin surface potentially carries a lot of bacterial commensals. The most heavily contaminated areas are likely to be close to body orifices - the perineal region in close proximity to the openings of the anus and vagina. Intertriginous areas (under the armpits, the groin folds, etc.) are also heavily contaminated. The palms and soles routinely pick up environmental bacteria.

 

[pattylou]

Also under the fingernails/toenails. And these regions will have a higher diversity, as they are simply "dirty" ie less likely to be routinely washed clean.

Speaking of which, the types of bacteria at any given site will vary enormously because of differences in conditions (humidity, salt, etc.)

 

[Ouabache]

Now there's something interesting to throw in with the old joke about the topologist who can't tell a donut from a coffee cup!

I hadn't heard that one. But after reading up on it, I agree, the topological space I described, fits the definition.. For those scratching their heads, Math Is Hard is referring to the mathematical construct topological space, in this case, a torus. (Perhaps this thread now qualifies for crosslisting within a math topic )