State University of New York at BuffaloSchool of Medicine and Biomedical SciencesDepartment of Microbiology and ImmunologyMicrobiology 301February 6, 2012 D. Dombroski [email protected] 829-2355StaphylococcusFamily: MicrococcaceaeGenus: StaphylococcusSpecies: Staphylococcus aureusStaphylococcus epidermidisStaphylococcus saprophyticusMicroscopic Morphological AppearanceGram positive cocciarrangement – irregular clustersnon-spore formersnon-motileusually no capsuleVirulence FactorsI. Extracellular ProductsA. Protein toxinsHemolysin – lyses red blood cells by disrupting cell membrane Leukocidin – lyses white blood cells by disrupting cell membrane1Enterotoxin – food poisoningToxic Shock Syndrome (TSST-1) – stimulates production of interleukin (IL-1) by macrophages resulting in fever inductionB. EnzymesCoagulase – plasma clotting protein; converts fibrinogen to fibrina. coats bacteria with fibrin and prevents phagocytosisb. aids in attachment Fibrinolysin – digests fibrinogen (fibrin clots) Hyaluronidase (“spreading factor”) – digests hyaluronic acid around host cells promotes invasion Lipase – degrades lipids – allows bacteria to colonize oily skin Penicillinase – hydrolyzes penicillin; drug resistance Catalase – degrades H2O2 – a toxic metabolic end product Exfoliatin or epidermolytoc toxin – protease that causes peeling of superficial skin layers by dissolving intracellular bridgesII. Structural Surface ComponentProtein A – surface component linked to peptidoglycan layer of cell wall; inhibits antibody-mediated clearance of bacteria by binding to IgG. Lipoteichoic acid – binds to tissue components; cell adhesion2Staphylococcus aureus – major pathogen of genusCarriage location – anterior nares, nasopharynx and skinCarriage rate – 30 to 50% of healthy adultsVirulence Factors/Species Identification of Staphylococcus aureuscoagulase positivehemolysin (alpha toxin)leukocidinprotein AcapsuleToxins of Staphylococcus aureusI. Blood cell toxinshemolysinsleukocidinII. Intestinal toxinsenterotoxinsIII. Epithelial toxinsexfoliatin or epidermolytic toxinInfectious Diseases caused by Staphylococcus aureusI. Superficial infections – localized cutaneous infections3II. Toxigenic infectionsA. Staphylococcal Scalded Skin Syndrome (SSSS)B. Toxic Shock Syndrome (TSS)C. Gastrointestinal DiseaseIII. Systemic InfectionsI. Superficial Cutaneous InfectionsPyodermic infections – pimples, boils, carbuncles and impetigoCharacteristic symptom – pus formation – Staphylococcus – pyogenic cocciMode of infection - Staphylococci invade skin at: a. sebaceous gland opening (skin gland)b. hair folliclec. wound- Infection site – abscessPrimary infection sites – face, back of neck, buttocksSymptoms – edema, erythema, pain, pusRisk groups – elderly and young children with poor personal hygieneTreatment – minor lesions self resolve surgical incision and drainage chemotherapy – topical antibiotics4II. Toxigenic InfectionsA. Staphylococcal Scalded Skin Syndrome (SSSS)Virulent feature: exfolatin or epidermolytic toxinseparates epidermal layer from the dermis blistering and peeling of the skin exposes red under layergeneral appearance – burned skinMode of infection - syndrome begins as an erythema around the mouth and nose- spreads rapidly to infect skin of the neck, trunk and extremitiesRisk group – infants and young children < 4 years (neonatal infection)Primary infected sites – umbilical cord and eyes – low mortality rateDeath – secondary infection of the denuded skin by other bacterial pathogensTreatment – topical antibiotic – mupirocinB. Toxic Shock Syndrome (TSS)Incidence of Infection – usage of super absorbent vaginal tamponsVirulent feature – toxic shock syndrome toxin -1 (TSST-1)Mode of infection- super absorbent brands strongly bind Mg++ ions- low concentration of Mg++ triggers TSST-1 production which is absorbed into the bloodstream- TSST-1 (superantigen) that stimulates T-lymphocytes to produce cytokines intravascularly resulting in endothelial cell damage – shock and multisystem organ failure5Initial symptoms - high fever, vomiting, diarrhea and muscle cramps (myalgia)Ten days later – hands and soles of feet develop a sunburn-like rash which results in a peeling of the skinSevere symptoms – shock and multi-organ failureDeath – 2 – 5% respiratory failureHigh risk group/high risk factormenstruating women – usage high absorbancy tamponsnon-menstruating groups – postpartum women with surgical wound infections (hysterectomies)nasal surgery and packingPrevention/Control - removal of cellulose based superabsorbent tampons from market in 1980CDC recommends that tampons are not used continuously during a menstrual cycleTreatment – fluid replacement and chemotherapyC. Toxigenic Gastrointestinal Disease – Food poisoning (food intoxication)Source contamination – food handlerStaphylococcal lesions of skin (hands and nasopharyngeal carriers) contaminate food food unrefrigerated room temperature growth of Staphylococcus aureus production of enterotoxin (exotoxin)6Virulent feature – enterotoxin (exotoxin) heat stable - not inactivated by digestive enzymes -toxin production does not alter food taste or smellAction of enterotoxin - disrupts gastrointestinal liningSymptoms – start in 4 – 6 hours – vomiting, cramps, diarrhea, nauseaRecovery – self-limited – 24 – 48 hoursIII. Systemic Infection/deeper infectionBacteremia – dangerous because the microbes are carried to all body sitesBacteria reach site via:- focus of infection- extensive surgery- traumatic injuriesSystemic infectionsosteomyelitis (inflammation of bone)pneumoniaendocarditis (inflammation of endocardium)meningitis (inflammation of the membrane surrounding the brain and spinal column), andpyoarthritisRisk factor involved in acquiring a systemic infectionPre-condition in an individual: diabetes, burn wounds, extensive surgery, cystic fibrosis, cirrhosis