Infection Biology Flashcards
Cause disease only in immunocompromised people
Opportunistic pathogens
Microbes that can cause disease
Pathogens
Measure of a microbe’s ability to cause disease
Virulence
Number of organisms required to cause disease in 50% of the population
ID50 Infective Dose 50
Mediates attachment of bacteria
Pili
Mediates strong adherence to the surface of human cells
Glycocalyx
Surface proteins that mediate binding to endothelium and to extracellular proteins such as fibronectin
Curli
Accelerates formation of a fibrin clot coating the organisms with a layer of fibrin
Coagulase
Helps spread through subcutaneous tissue
Collagenase and Hyaluronidase
Destroys both neutrophilic leukocytes and macrophages
Leukocidin
Enumerate bacteria with IgA Protease
Streptococcus pneumoniae Haemophilus influenzae Neisseria Meningitidis Neisseria Gonorrhea SHiNe My Gong
Protects against phagocytosis
Polysaccharide capsule
Anticapsular antibodies allow more effective phagocytosis to occur
Opsonization
Cell wall protein of S. pyogenes that is antiphagocytic
M protein
Cell wall protein of S. aureus that prevents complement activation
Protein A
Gram positive and negative bacteria Secreted from the cell Polypeptide Genes located in the plasmid or bacteriophage High toxicity High antigenicity Can be used as vaccines Destroyed rapidly at 60C
Exotoxins
Gram negative bacteria Not secreted from the cell Lipopolysaccharide Genes are found in the bacterial chromosome Low toxicity Low antigenicity No vaccine available Stable at 100C for an hour
Endotoxins
What kind of toxins does tetanus and botulism exhibit A) Endotoxin B) Exotoxin
B) Exotoxin
What kind of toxins does meningococcemia exhibit A) Endotoxin B) Exotoxin
A) Endotoxin
Polypeptides secreted by certain bacteria that alter specific cell functions resulting in the symptoms of disease
Exotoxin
The ONLY exotoxin secreting bacteria that is heat-labile
Staphylococcal enterotoxin
Inhibits elongation of factor II Basically, inhibits protein synthesis
ADP ribosylation
Located in the outer membrane of gram negative bacteria
Lipopolysaccharides
The toxic component of lipopolysaccharides
Lipid A
1) induces the overproduction of cytokines like TNF and IL1 2) activates the complement cascade 3) activates the coagulation cascade resulting in DIC
Lipid A
All bacteria have cell walls composed of peptidoglycan EXCEPT
Mycoplasma pneumoniae (Sterol instead of peptidoglycan)
All gram-positive bacteria have NO endotoxin EXCEPT
Listeria monocytogenes
All bacterial capsules are composed of polysaccharide EXCEPT
Bacillus anthracis
Gram positive cocci Determines pattern of hemolysis
Blood agar
Enteric gram negative rods Selects against gram positive bacteria Differentiates between lactose fermenters and nonfermenters
MacConkey Eosin-methylene blue
Distinguishes lactose fermenters from nonfermenters Distinguishes H2S producers from nonproducers
Triple sugar iron (TSI)
Agar used for Clostridium perfringens
Egg yolk
Agar used for Corynebacterium diphtheriae
Tellurite
Agar used for group D streptococci
Bile esculin
Agar used for staphylococci
Mannitol salts
Agar used for N. meningitidis, N. gonorrhoeae from STERILE sites
Chocolate
Agar used for N. gonorrhoeae from NONSTERILE sites
Thayer-Martin
Agar used for Haemophilus influenzae
Chocolate + Factors X and V
Agar used for Mycobacterium tuberculosis
Löwenstein-Jensen
Agar used for Vibrio Cholerae
Thiosulfate Citrate Bile Salts (TCBS)
Agar used for Bordetella pertussis
Bordet-Gengou
Agar used for Legionella pneumophila?
Charcoal-yeast extract
Agar used for Campylobacter or Helicobacter?
Skirrows (Campi’s)
Agar used for Borrelia burgdorferi?
Barbour-Stoenner-Kelly (BSK)
Agar used for Mycoplasma pneumoniae?
Eaton
Agar used for Pseudomonas aeruginosa?
Cetrimide
Agar used for Salmonella and Shigella?
Xylose-Lysine-Deoxycholate (XLD)
Agar used for Leptospira interrogans?
Ellinghausen-McCullough-Johnson-Harris (EMJH) / Fletcher’s
Determines whether antibodies are present in the patient’s serum Detects the antigens of the organism in tissues or body fluids At least a fourfold increase in titer between the acute and convalescent samples
Serologic tests
Test that is highly specific, quite sensitive and much faster than culture Especially useful for those bacteria that are difficult to culture What is this test and give examples of the organisms?
Molecular tests (Nucleic acid amplification tests, nucleic acid probes, and nucleic acid sequence analysis) Chlamydia and Mycobacterium