Got Staph?

Staphylococcus is a genus of 33 species of bacteria. Often, one associates Staph with the species Staphylococcus aureus, which causes disease in humans. While this particular strain causes hassle and can be life threatening as its effects range from mere pimples to pneumonia, other Staphylococci reside normally on our skin and on mucous membranes of other organisms.

Yesterday, the area around the nose was swabbed and placed in a 7% NaCl broth and sealed with mineral oil to prevent the entry of oxygen. This treatment should enrich for Staphylococcus since most of these are salt tolerant bacteria. You may be wondering why the enrichment is under anaerobic conditions when Staphylococcus live on our skin, where there is definitely oxygen. Well, Staphylococcus are facultative anaerobes. This means that they respire both aerobically (in the presence of O2) and anaerobically (without O2). In order to enrich for Staphylococcus it was necessary to remove oxygen from the system to prevent growth of Micrococcus which is a strict aerobe.

Next week we will see what grows. After a isolating the bacteria and then performing tests on the pure culture it will be possible to identify the strain of bacteria isolated. This will be done using a simple dichotomous tree which includes only the most commonly found species. More on this later!