Staph strep and GI Flashcards
Staphylococcus virulence factors
Protein A: unique to staph aureus, major protein component of cell wall binding to Fc portion of IgG binds them backwards
Toxins: hemolysins, leukotoxins, Enterotoxins (superantigens) TSS (toxic shock syndrome totoxin), exfoliative toxins (scalded skin syndrome)
Staph toxins
Staph hemolysins are Beta hemolytic (form the clear area of hemolysis on blood agar)- they damage membranes and produce tissue damage
Leukotoxins: attacks PMNs and macrophages
Enterotoxins: the toxin not the bacteria causes diarrhea and vomiting, symptoms are from ingestion of a perfromed enterotoxin (symptoms occure within 2-6 hours of infection-ie food poisoning, heat stable and resistant to digestive proteases
Super antigens
Enterotoxins and toxic shock syndrome- bind directly to MHC2 and TCR independent of antigen stimulating T cells and massive cytokine storm
Exfoliative toxins 2 forms (ETA and ETB)- proteases that lyse intercellular attachments between epidermal cells, causing scaled skin syndrome
Staph aureus treatment
drain wound, remove foreign body
Antibiotic therapy - Nafcillin (Methacillin subgroup) not penecillin due to MRS mutations in the penecillin binding protein
Vancomyocin often used -lead to VRSA
Streptococci
Charachteristics: gram positive arranged in pairs (s. pneuo) or chains (s. pyogenes)
Most are facultative anaerobes (ferment carbs resulting in lactic acid production0
Catalase negative
Cell wall carbohydrates: aka Lancefield typing: group A (pyogenes) and group B (s. agalactiae)
Hemolytic pattern: Alpha partial hemolysis, Beta-complete clearing, Gamma-no change in RBC
Barriers to invading pathogens
Epithelial barrier and intestinal motility: shedding and regenereating, turnover helps, antimotility drugs increade and proling susceptibilty to infections
Chemical barrier: gastric acidity and stomach kill some invading pathogens PPIs can make patients more susceptible
Paneth cells: located on the crypts and secrete de3fensisn and lysozymes to kill
Adaptive immunity high concentration of IgA in MALT and breast milk
Microbial Recognition: PRRs recognize PAMPS
Commensals
important for driving the maturation of the immune syste3m (natural microbiota monopolies nutrients to prevent pathogens from eating)
Staphylococcus aureus
Egypt scene:
Bundle of grapes looking golden on blood agar Gram positive (Purple robe), Catalase + (will H202->h20), coagulase positive (will coagulate blood), beta hemolytic (completely lysis RBC), Manitol salt agar (ferments manitol and will convert the pink agar into a yellow pigment)
Protein A (main virulence factor)- cell wall component that binds to Ab to prevent complement opsonization
Colonizes nose (sphincs)
Inflammatory diseases: pneumonia (with patchy infiltrate), with capsules post viral bacterial infection, septic arthritis, large bloody abcesses, endocarditis with iv drug users
Osteomyelitis- bone inflammation (most common cause due to S. aureus)
Scalded skin syndrome due to exfoliative toxin (protease) Toxic shock syndrome due to TSST
Staph food poisoning rapid onset vomiting from ingested toxins in food
MRSA: altering the PBPs that construct the cell wall, Penicillin (nafcillin) is good if the staph isnt MRSA
Vancomyocin is a good treatment
Staphylococcus epidermis and saprophyticus
Hot girl and plumber
Gram Positive
epidermidis:
infects artificial implants and catheters, part of normal skin floura, most common cause of endocarditis due to heart valves, because it has adherins (polysach) can stick to slick surfaces and has a biofilm that allows for resistance. NOVOBIOcin Sensitive (belly button)
VANCOMYOCIN and take out the site of infection
saprophyticus: novobiocin resistant
common cause of UTIs in females that are sexually active
Both are: catalase positive, urease positive (converts urease to amonia), coagulase NEGATIVE
Streptococcus pyogenes (group A strep)
pie makers
long chains of balls
Encapsulated with Hyluranic Acid (pie covered)- made in connective tissue, Beta hemolytic
Infections: impitigo (honey crusted skin infection), pharyngitis (red inflammed throat), cellulitis and erycipola (erythemia of skin)
Toxin: Streptococcoal pyrogenic toxin SPE toxin: scarlet fever (reddeinging and welling of toungue strawberry tongue with pharyngitis and red rash except face), Toxic shock like syndrom super antigen, Necrotizing faciatis (might need amputations) SPE (serotypes A B and C: A and C are the super antigen SPE and B is a protease causing Nec facia)
Rhumatic fever and post streptococcal glomerulonephritis (PSGN): Rhumatic fever (M protein highly antigenic virulence, anti phagocytic, causing high humoral response mimicing myosin (autoimmune attack on heart mitral valve) only happens with pharyngitis form and not the skin disease
Rhumatic fever: JONES (joints, o heart problems, Nodules subcutaneus, erythemia marginatum (red rash with borders, S sydenhams chorea rapid movement of hands and face) early treatment stops R.F.
PSGN: either pharygitis or skin infection cause autoimmune attack type 3 from circulating antibodies that end up in glomerulus ends up puffy face and brown urine after two weeks strep infection cant stop PSGN
Penecillin is the best treatment
Virulence factor: streptolysin O (causes beta hemolysis), streptokinase (causes plasminogen clots blood), DNAases -depolymerizing DNA
Group A strep is BACITRACIN SENSITIVE
We make Anitbodies against group A strep: that can be used for diagnosis in titers
Streptococcus Agalactiae (Group B strep)
Space baby
Gram positive, causes bad infections in babies, hippurate positive, has a poly saccharide capsule. CAMP test positive (there is a zone of hemolysis with S.aureus), beta hemolytic, bacitracin resistant
Meningitis in neonates, sepsis, with pnuemonia thru vagina during birth (profolactic test), give + mom intrapartum penicillin
Streptococcus pneumonia and viridans
jousting tournament:
both are alpha hemolytic (partial hemolysis) green hue on test
Pneumo:
Encapsulated in polysaccaride, except optochin sensative, lancet shaped diplococci, bile soluble (cant grow in bile), causes pnuemonia, rust colored sputum, MOPS pneumonia (meningits, otitis media, pneumonia, sinusitis), protease that cleaves IgA, sickle cell are susceptible,
Treatment: Macrolides, third generation cephlasporin (ceftriaxone). Vaccine for adults: 23 valent IgM, for kids: 7 valent with protein (t-cell dependent IgG)
Viridans:
not encapsulated, optochin resistant, bile resistant/insoluble. Carried in Dental caries, causing endocarditis in damaged valves (mitral valves), adheres to platelets with dextrans
Enterococcus faecium and faecalis
protest at the caucus
UTIs, endocarditis, biliary tree infection
Facalis is more prevalent
Faecium: few occurances but super bug. Can grow in Salty solution (6.5%NaCl), bile resistant, nosicomial infection that are super resistant VRE. lineazolid, and tigecycline
