Staph Infection and MRSA Staphylococcus aureus Emily Jewell

Facultative Anaerobes Cocci Catalase positive Gram positive Facultative Anaerobes

Reservoirs Humans (Healthy) Humans (Infected) Contaminated food Skin –armpits, under breasts, groin Nose –mucosa Humans (Infected) Skin lesions, blood Respiratory mucosa Contaminated food Animals Fur, skin Athletic equiptment Fomites Staph infections turn deadly if the bacteria invade deeper –into the bloodstream, joints, bones, lungs, or heart

Transmission Auto-infection –infecting oneself Person to person –spread via skin-to-skin contact, or sharing towels, sports equiptment, swimming pools, etc Pets –S. aureus may be found on skin, hair, nostrils or saliva of animals Food poisoning –food contaminated with staphylococci released from an infected worker The bacteria enter the body through the skin and respiratory tract.

Mode of Action Enzymes Coagulase –clots plasma, coats bacterial cell to prevent phagocytosis Hyaluronidase –breaks down hyaluronic acid to aid spread of bacteria Deoxyribonuclease Lipase Staphylokinase –dissolves fibrin, aids spread Betalactamase –drug resistance

Mode of Action Continued Toxins Exotoxins Protein A Anchored in bacterial cell wall IgG-binding protein Staphyloxanthin Golden carotenoid pigment Virulence factor Bacterial antioxidant, helps evade the ROS (reactive oxygen species) that host uses to kill pathogens

Biological Effects –vary widely Boils –pus pockets develop in follicles or oil glands Impetigo –rash, oozing blisters Cellulitis –infection of deeper layers of skin, redness and swelling Staphylococcal scalded skin syndrome –from toxins  fever, rash, blisters Blood poisoning Food poisoning –typical symptoms, onset within hours Toxic shock syndrome Septic arthritis

Treatment Antibiotics Penicillin Many bacteria are resistant to penicillin, other antibiotics include: oxacillin or flucloxacillin

MRSA Methycillin Resistant Staphylococcus aureus Caused by inc. use of antibiotics Penicillinase (a form of ß-lactamase) –cleaves the ß-lactam ring of penicillin Hospitals Strain that is resistant to ß-lactam antibiotics Vancomycin is used to combat Glycopeptide antibiotic Inhibits synthesis of peptidoglycan by targeting and binding to amino acids in the bacterial cell wall –preventing cross-linkages from forming