Title : Genus Staphylococcus

 

 

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