What is it: Gram-positive spherical bacterium. It develops between 10°C and 45°C with temperature optimum between 30°C and 37°C; with regard to its pH, it is between 4 and 9 with optimum between 7 and 7.5. Though it is not a sporogenous, staphylococcus show remarkable resistance to unfavourable environmental conditions.
Where does it thrive: in water, on the skin and the mucous membranes. Human beings are constantly exposed to staphylococcus infection risk since most people usually harbour potentially pathogenic staphylococcus.
How does it strike: once it is in our organism it may trigger infections of several types: from skin infections, such as pimples, to lung infections, such as bronchial pneumonia, to blood infections, such as septicaemia. The incidence of staphylococcus infection among the hospital population, which is more likely to have open wounds and a weakened immune system, is particularly high. The onset of such epidemics in specific wards may be highly risky since it causes serious therapeutic and prophylactic problems.
What is it: Gram negative ubiquitous micro-organism form the Enterobacteriaceae family. Its culture is very simple; it is very tolerant of pH variation, with optimum of 7.5. The ideal temperature is 37°C. It is quite heat resistant: it incubates at 45°C.
Where does it thrive: it is found in soil, water, vegetation and intestinal flora of most animals. It is commonly found in the human organism; in the body it is the predominant bacterial facultative species in the large intestine.
How does it strike: some E.Coli strains are the etiologic agents of enteritis, a serious problem for first infancy children (exogenous) since they are caught by ingestion of food contaminated by immune carriers. E. coli is also the most frequent and predominant etiologic agent of (endogenous) urinary ways infections (cystitis, cisto-pyelitis, pyelitis). Besides urinary ways infection, Escherichia coli may cause septicaemia and neonatal meningitis, though it is important to underline that, especially over the last few years, a number of “opportunistic”-type infections have increased, such as those affecting hospital population, e.g. respiratory infections, wound infections, infections ensuing instrumental endoscopy, etc.
What is it: Gram negative bacterium, capable of thriving at a temperature comprised between min. 4 °C and max. 42°C, though it cannot survive below pH 4.5.
Where does it thrive: very commonly found in water, soil and as a commensal bacterium on the cutis and in the intestines. Because of its poor or nonexistent sensitivity to the most common antibiotics, its development is enhanced by any anti-bacterial based treatment which reduces the competition from the remaining microbial population, thus allowing the bacterium to reach otherwise impossible numbers.
How does it strike: predisposed humans, that is, people with a particularly weak immune system, are subject to suffer from several conditions, such as wound infections, burns, meningitis (lumbar punctures) or urinary ways infection ensuing instrumental surgery.
What is it: Very common Gram negative bacterium. It grows at 10- 45°C, in a solution containing up to 6.5% of sodium chloride, at pH 9.6, and survives for approximately 30 minutes at a temperature of 60°C.
Where does it thrive: it is part of the normal intestinal bacterial flora in humans and animals, though it is also found in plants and insects. It is used as faecal contamination indicator in water and food.
How does it strike: bacterium with a low pathogen charge, though it has some genes able to code the resistance to specific antibiotics; thus it manages to survive in environements where those are largely used. Over the last 15 years it was detected to be the cause of hospital infections which mostly affect the urinary ways and surgical wounds, causing bacteremia and even endocarditis. Most infections of enterococcus nature are caused by E. faecalis (85-90%).