What are the distinctive characteristics of Staphylococcus aureus?

S. aureus is an aerobic and facultative anaerobic organism that forms fairly large yellow or white colonies on nutrient rich agar media. The yellow colour of the colonies is imparted by carotenoids produced by the organism.

What are the 5 characteristics of pathogenic S. aureus?

aureus expresses many potential virulence factors: (1) surface proteins that promote colonization of host tissues; (2) invasins that promote bacterial spread in tissues (leukocidin, kinases, hyaluronidase); (3) surface factors that inhibit phagocytic engulfment (capsule, Protein A); (4) biochemical properties that …

How do you identify Staphylococcus aureus?

Two different coagulase tests are commonly used to identify S. aureus. One is a tube test for free coagulase and the other is a slide test for bound coagulase. The tube coagulase test is thought to be the more definitive of the two, however, it can take several hours to overnight to produce a result.

What is the colony characteristics of S. aureus on nutrient agar?

S. aureus – individual colonies on agar are round, convex, and 1-4 mm in diameter with a sharp border. On blood agar plates, colonies of Staphylococcus aureus are frequently surrounded by zones of clear beta-hemolysis.

What physical properties make S. aureus A common hospital acquired pathogen?

aureus can grow in a wide range of temperatures (7° to 48.5°C; optimum 30 to 37°C), pH (4.2 to 9.3; optimum 7 to 7.5), and sodium chloride concentration up to 15% NaCl. S. aureus is a desiccation tolerant organism. About 20-30% of individuals are persistent carriers of S.

Does Staphylococcus cause acne?

Large, painful bumps that look like acne can sometimes be caused by staph bacteria. This bacteria, Staphylococcus aureus, is around us all the time: on our skin, in our noses, on surfaces, and on the ground. Inflamed skin blemishes are the most common type of staph infection.

Is S. aureus DNase positive?

After application and penetration of hydrochloric acid into the medium, DNase positive organisms such as Staphylococcus aureus or Serratia marcescens will be surrounded by clear zones of depolymerized DNA while the medium farer away from the inoculation band will be opaque and whitish due to polymerized DNA.

What is the texture of Staphylococcus aureus?

aureus are circular, smooth, convex, moist, 2-3 mm in diameter on uncrowded plates, gray to jet-black, frequently with light-colored (off-white) margin, surrounded by opaque zone and frequently with an outer clear zone; colonies have buttery to gummy consistency when touched with inoculating needle.

How do you differentiate S. aureus and S. epidermidis?

aureus is often hemolytic on blood agar; S. epidermidis is non hemolytic. Staphylococci are facultative anaerobes that grow by aerobic respiration or by fermentation that yields principally lactic acid. The bacteria are catalase-positive and oxidase-negative.

What are the characteristics of Staphylococcus aureus?

Staphylococcus are spherical cells 0.5 to 1 μm in diameter called cocci, which are arranged in groups, simulating bunches of grapes. Before the Gram staining technique, they are stained purple, that is, they are Gram positive. S. aureus it is not mobile, it does not form spores, some strains have a polysaccharide capsule.

Where is S aureus found in the human body?

S. aureusis found in the environment and is also found in normal human flora, located on the skin and mucous membranes (most often the nasal area) of most healthy individuals.

What is the pathophysiology of aureus infection?

They are a group of proteins (A, B, C, D) that cause pseudomembranous colitis, diarrhea and vomiting and are responsible for food poisoning caused by consuming food contaminated with aureus.

Is S aureus infection life threatening?

Other S. aureusinfections, such as moderately severe skin infections, including furuncles, abscesses, and wound infections, are usually not life-threatening but may be accompanied by significant morbidity and pain. Due to their frequency (several millions annually in the U.S.), they represent a considerable public health burden [6].