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

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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