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62 Cards in this Set
- Front
- Back
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What are some phenotypic characteristics of Staphylococcus?
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Gram Positive, cluster-forming coccus, nonmotile, nonspore forming, facultative anaerobe. Forms golden-yellow colonies, can tolerate high salt concentrations.
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What does it mean to be a facultative anaerobe?
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makes ATP using oxygen if present, but can switch to fermentation. Fermentation of glucose mainly produces lactic acid.
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Describe the catalase positive test.
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Catalase is used to convert hydrogen peroxide to water and oxygen. Catalase-positive is when oxygen forms, as is the case with Staphylococcus.
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What organism is catalase negative?
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Streptoccus
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What does the coagulase test differentiate between?
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Staphylococcus aureus and A coagulase negative species.
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What are the A coagulase negative species?
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S. epidermidis, S. saprophyticus, S. haemolyticus, S. lugdunensis,
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What are some virulence factors?
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Attachment, evasion, invasion, toxin production, and now antibiotic resistance.
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What are MSCRAMM?
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Microbial Surface Components Reacting with Adherence Matrix Molecules. Promote binding to host tissue, especially wounded tissue like fibrinogen, elastin, collagen, fibronectin.
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Name some examples of MSCRAMMs.
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Elastin binding protein, Collagen binding protein, Fibronectin binding protein, clumping factor, coagulase.
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Describe how clumping factor and coagulase work as MSCRAMM.
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Clumping factor and coagulase bind to fibrinogen and convert it to fibrin. Although fibrinogen is soluble in blood plasma, fibrin is deposited on the wound matrix. Fibrinogen also coats many biomaterials in the body.
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What is hyaluronic acid?
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cement that holds the cells together
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What is the purpose of hyaluronase?
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Breaks down the hyaluronic acid to aid in the invasion/spreading of pathogens.
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What are two ways of pathogenic evasion?
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capsule and lipid A
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How does protein A prevent opsonization?
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Binds to the Fc portion of IgG. This prevents recognition of the bacterial cell by the immune system.
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Which antibody is used in opsonization?
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IgG
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What are the four different types of toxins produced by Staphylococcus?
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Cytotoxins, Exfoliative toxins, Enterotoxins, TSST-1
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What are cytotoxins?
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Toxins that play a role in invasion and evasion Acheive toxicity by creating pores in the cell membrane. Toxic for many cells including neutrophils and macrophages.
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What are some examples of cytotoxins and what diseases are they associated with?
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Alpha, beta, delta, and gamma toxins. Panton-Valentine leukocidan which is associated with carbuncles, necrotizing pneumonia, and community acquired MRSA.
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Describe exfoliative toxins and their associated diseases.
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Act from a distance, organisms need not be present. Two types: ETA and ETB. Rare. Cause Staphylcoccyl scalded skin syndrome (SSSS)
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Describe enterotoxins.
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Heat stable (100 degrees for 30 minutes), survive well in stomach, may act as superantigens, cause foodborne intoxication. S. aureus produce 15 foodborne toxins.
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Briefly describe TSST-1
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Described as a superantigen, usually associated with menstrual associated toxic shock syndrome, can penetrate mucosal barriers.
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What are two ways that Staphylococcus have shown antibiotic resistance?
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beta-lactamase and alternative PBP
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Describe how beta-lactamase works.
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deactivate beta-lactams used in antibiotics. Secreted by gram negative bacteria. Methicillin is resistant to beta-lactamase.
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Describe how an alternate PBP works.
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A different peptide binding protein is used and is therefore not recognized by the beta-lactam antibiotics.
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What is the purpose of the agr system?
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accessory gene regulator, regulates the expression of surface proteins (expressed during growth) and exoproteins (expressed during the stationary phase).
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Where is the primary reservoir for Staphylococcus in humans?
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The anterior nares
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How is Staphylococcus spread and what are some risk factors?
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spread by person-person contact and contact with fomites. common in nosocomial infections. Risk factors: presence of foreign body or surgical procedure.
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What is a fomite?
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inatimate object that can harbor pathogenic diseases and thus serve as an object of transmission.
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What is impetigo?
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Contageous skin disease characterized by pustules on the skin.
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1. 0.4 cun lateral to the corner of the mouth.
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St-4
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What is osteomylitis?
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Infection within the bone.
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What is cystitis?
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Infection in the bladder.
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What are the diseases that can be caused by Staphylococcus?
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Stye, boils, carbuncles, pneumonia, emesis, scalded skin syndrome, osteomylitis, sinusitis, hematogenous spread, endocarditis, impetigo, diarrhea, TSS, UTI, cystitis.
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What is Staphylcoccal Scalded Skin Syndrome caused by?
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S. aureus expressing ETA or ETB.
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What are the two forms of SSSS
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Generalized and localized.
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Describe generalized SSSS.
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Toxin produced by local infection spreads throughout the body. no bacteria or pus present in blisters, causes generalized skin scalding. Host will eventually fight off disease, but the toxin is disseminated throughout the body and localized in the skin. Attracted to the molecule that holds skin together.
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Describe localized SSSS.
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Localized spread of toxin around a colonized wound. Individual has some immunity already, and therefore doesn't spread througout the body. Infection and blistering occur in the same area.
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What causes food poisoning?
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Ingestion of preformed enterotoxins. This is intoxication, not an infection. Food is contaminated by human carrier.
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How long does food poisoning last?
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Onset is 4 hours, lasts less than 24 hours.
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What are the two types of TSS?
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Menstrual and non-menstrual.
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What is required for toxin expression in TSS (menstrual)?
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Elevated protein levels, neutral pH, elevated CO2, elevated O2.
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Describe how TSS menstrual occurs.
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By use of high-absorbancy tampons, TSST-1 (regulated by agr) can cross mucosal barriers under the right circumstances.
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What is the difference between menstrual an non-menstrual TSS?
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Menstrual toxins can cross mucosal barriers, non-menstrual cannot. non-menstrual is also caused by enterotoxins in addition to TSST-1 and colonizes in surgical wounds, catheters, etc.
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Describe the clinical manifestations of TSS.
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Fever, hyptension, erythema (skin reddening), affecting multiple organs, mass desquamtion, especially on hands and feet.
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What does pyogenic mean?
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pus-producing.
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What does pyrogenic mean?
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fever-inducing
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What are the four cutaneous infections by Staphylococcus?
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Impetigo, folliculitis, furuncles, carbuncles.
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Describe impetigo.
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Very common in children. Very contagious. Secondary infection common. Cutaneous infection.
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Describe folliculitis.
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infection of the hair follicle.
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Describe furuncles.
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Boils. Large, painful nodules containing pus.
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Describe carbuncles.
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When furuncles coalase and extend into subcutaneous tissue. Risk of bacteremia.
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Describe bacteremia.
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spread of infection through the blood. Can lead to other diseases.
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What are the risk factors of bacteremia?
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Surgical procedures, invasive catheters.
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What are the other diseases that can be caused by bacteremia?
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endocarditis, pneumonia, osteomylitis, septic arthritis.
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What is the mortality rate of endocarditis.
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Requires immediate treatment. Mortality rate is 50%
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Describe oseteomylitis.
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Infection of the bone. Hematogenous spread from bone to bone. Can occur following trauma.
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Describe septic arthritis.
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bacterial infection of the joints.
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What are the two different types of MRSA?
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Hospital acquired, community acquired.
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Describe the hospital acquired MRSA.
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low virulence factors, but extremely high antibiotic resistance.
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Describe the community acquired MRSA.
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High virulence factors, but low anitbiotic resistance.
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Describe the effects of S. epidermidis.
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Although it is part of the normal skin flora, it causes infections in catheters and implants (heart valves). Multi-drug resistance is more common than in S. aureus.
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Describe the effects of S. saprophyticus.
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Causes UTI's predominantly in young, sexually active women.
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