CAM102 Lecture Notes - Lecture 36: Staphylococcus, Staphylococcus Aureus, Flucloxacillin
Bacterial Diseases
Taxonomic Classification
Bergey's Manual of Systematic Bacteriology
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Staphylococcus Aureus
• Domain: bacteria
• Phylum: Firicutes
• Class: Bacilli
• Order: Bacillales
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• Family: staphylococcaceae
• Genus/species: Staphylococccus Aureus
• Gram-positive
• Facultative anaerobe
• Catalase and Coagulase positive
• Ferments manitol
• Protein A positive
In diseases:
• Conjunctivitis
• Lactational Mastitis
• Folliculitis
• Boils
• Carbuncles
Virulence factors
• Polysaccharide capsule: inhibits phagocytosis and facilitates adhesion to host tissue
• Protein A: binds the Fc portion of IgG in an upside down orientation and inhibits phagocytosis
Enzymes
• Hyaluronidase breaks down hyaluronic acid, a component of CT, and is therefore believed to
facilitate spread of the bacteria through tissues
• Coagulase converts soluble plasma fibrinogen into fibrin clots and excludes immune molecules
and cells, and blocks blood vessel causing tissue necrosis
Exotoxins
• Exfoliatin (a specific serine protease that recognises and cleaves cell-cell adhesion mediating
desmosomal adherins in the superficial layers of the skin, responsible for the clinical
manifestation of staphylococcal scalded skin syndrome)
• Toxic shock syndrome toxin a super antigen that causes systemic inflammation, toxic shock
and organ failure
• Enterotoxins a feature in staphylococcal food poisoning
• Alpha toxin a haemolysin
Transmission
• Asymptomatic persistent carriage: occurs in approx 30% of healthy adults but can be higher in
health care workers and patients
• Main sites:
1. Anterior nares
2. Nasopharynx
3. Perineum
4. Other skin sites
• Most infection from self/endogenous
• And exogenous
• Skin and fomite transmission
• Can survive for prolonged periods on dry surfaces
Antiseptic Treatment of wounds
Good wound care practises are effective for minor wounds and infections
• Re-open wound
• Remove foreign material
• Drain abscesses
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Document Summary
Staphylococcus aureus: domain: bacteria, phylum: firicutes, class: bacilli, order: bacillales. Family: staphylococcaceae: genus/species: staphylococccus aureus, gram-positive, catalase and coagulase positive. Virulence factors: polysaccharide capsule: inhibits phagocytosis and facilitates adhesion to host tissue, protein a: binds the fc portion of igg in an upside down orientation and inhibits phagocytosis. Good wound care practises are effective for minor wounds and infections: re-open wound, remove foreign material, drain abscesses, clean wound and surrounding tissue with saline, debridement, apply appropriate dressings. Localised sores: mupirocin ointment: multiple sores or recurrent infection. Flucloxacillin: cephalexin (for penicillin hypers, trimthoprim w/ sulfamethoxazole (for penicillin immediate hypers) Soft tissue destruction: aureus introduced via skin break, wounds or surgery, toxin release causes extensive tissue destruction, can lead to systemic toxicity, organ failure, amputation or death. Inflammation of the conjunctiva: contagious through direct conduct, often purulent, antibiotic treatment: chloramphenicol eye drops/oitment. Staph aureus infection of the breast associated with breastfeeding. Flucloxacillin: cephalexin (for penicillin hypers, clindamycin (for penicillin immediate hypers)
