- Gram (+) cocci in small/large irregular clusters or in grape-like formation
- Measures 0.5-1.5 micrometer in diameter
- Facultatively anaerobic
- Non-selective. Grows well on ordinary culture media like nutrient agar containing 10% NaCl.
- Pigment producer.
- Temperature growth ranges from 18 oC (minimum growth temperature) to 40oC (maximum growth temperature)
- Produce colonies which are round, small, smooth, glistening and pigmented.
- Staphylococcus aureus – lemon-yellow colonies
- Staphylococcus albus/epidermidis – ivory white
- Staphylococcus citreus – orange
o Of these three species, only Staphylococcus aureus is pathogenic.
Structure and Function
- Capsule – inhibits opsonisation and phagocytosis; protects from C- mediated leukocyte destruction.
- Peptidoglycan – osmotic stability; stimulates production of endogenous pyrogen; leukocyte chemoattractant; inhibits phagocytosis and chemotaxis
- Protein A – binds IgG1, IgG2, IgG4 Fc receptors; inhibits opsonisation and phagocytosis; leukocyte chemoattractant; anticomplimentary.
- Teichoic acid – regulates cationic concentration at cell membrane; receptor for bacteriophages; attachment site for mucosal surface receptors
- Cytoplasmic membrane – osmotic barrier; regulates transport into and out of cell; site of biosynthetic and respiratory enzymes
- Inhabits the skin, mucous membranes of the nose, respiratory tract and lower portion of large intestine.
- Transmitted via mouth by ingestion of contaminated foods especially processed foods like ham, bacon, hotdogs, also foods rich in eggs, milk and carbohydrates like potato salad, custard-filled pastries and ice cream
- Via skin through cuts, wounds and abrations
Signs and Symptoms
- Staphylococcal scalded skin syndrome (Ritter’s disease)
- Furunculosis or boil (abscess formation)
- Small pustule or pimple
- Stye or hordeolum
- Toxic Shock Syndrome
- Impetigo contagiosa (Indian fire)
- Otitis media
- Staphylococcal conjunctivitis
- Staphylococcal meningitis
- Staphylococcal pneumonia
- Hospital acquired infection/nosocomial infections
- Staphylococcal food poisoning
- Penicillin G – drug of choice; cephalosphorin as substitute drug
- For penicillin resistant strains, perform culture and sensitivity test
- Cleanliness and personal hygiene
- Aseptic management of wounds
- Avoid eating left-over foods
Photo credits: www. biology4kids.com