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 40^oC (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

Photo credits: www. biology4kids.com

Daisy Jane Antipuesto RN MN

Currently a Nursing Local Board Examination Reviewer. Subjects handled are Pediatric, Obstetric and Psychiatric Nursing. Previous work experiences include: Clinical instructor/lecturer, clinical coordinator (Level II), caregiver instructor/lecturer, NC2 examination reviewer and staff/clinic nurse. Areas of specialization: Emergency room, Orthopedic Ward and Delivery Room. Also an IELTS passer.

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