Staphylococcus is named after the grape bunches its cells form
Under a microscope, staphylococci pile up in irregular clusters that reminded early scientists of grapes, and the name joins the Greek words for a bunch of grapes and a berry. Most of these bacteria live quietly on skin and in noses, yet one species, Staphylococcus aureus, ranks among medicine's most troublesome pathogens.
The Scottish surgeon Alexander Ogston first described clustered round bacteria in pus from an abscess. Friedrich Julius Rosenbach then set up the genus and told S. aureus apart from the organism now called S. epidermidis. Today the naming authority LPSN recognises 76 species, with S. aureus as the type species. In 2020 five species were moved into a new genus, Mammaliicoccus, though databases still disagree over whether that split stands.
These are Gram-positive spheres with a thick cell wall, mostly unable to move or form spores, and able to live with or without oxygen. Many tolerate salty conditions. Laboratories separate them from streptococci with a catalase test, then use coagulase, the ability to clot blood plasma, to sort the groups. Nine species are traditionally counted as coagulase-positive, but a genus-wide study found 13 that clotted at least one of six animal plasmas, mainly through a protein that binds von Willebrand factor.
Species that do not clot plasma are lumped together as coagulase-negative staphylococci, a practical label rather than a true family grouping. They usually belong to the normal flora but can turn opportunistic: S. epidermidis colonises catheters and implants, and S. saprophyticus causes urinary tract infections. The genus turns up well beyond people, on mammals and birds, in foods and even in flower nectar; a 2019 air survey in Delhi found three species floating in polluted air.
S. aureus can ride harmlessly on skin or in the nose, yet it also causes skin infections, pneumonia, bone and heart valve infections and bloodstream disease that may progress to sepsis. Genome sequences of the methicillin-resistant strains N315 and Mu50 revealed many genes for virulence and drug resistance, some carried on mobile elements that let bacteria swap them. Resistant strains, known as MRSA, pose the greatest danger in intensive care and to patients with implanted devices.
Source: Staphylococcus
