Genus Staphylococcus
Features
§ 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.
Types
§ 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
Cause
§ 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
§ Carbuncle
§ Mastitis
§ Toxic Shock Syndrome
§ Impetigo contagiosa (Indian fire)
§ Paronychia
§ Acne
§ Osteomyelitis
§ Otitis media
§ Staphylococcal conjunctivitis
§ Staphylococcal meningitis
§ Staphylococcal pneumonia
§ Pyelonephritis
§ Hospital acquired infection/nosocomial infections
§ Staphylococcal food poisoning
Treatment
§ Penicillin G – drug of choice; cephalosphorin as substitute drug
§ For penicillin resistant strains, perform culture and sensitivity test
Prevention
§ Cleanliness and personal hygiene
§ Aseptic management of wounds
§ Avoid eating left-over foods
Sources: http://nursingcrib.com/microbiology/genus-staphylococcus