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24 Cards in this Set
- Front
- Back
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6Q:
List the general properties of Streptococci. |
6A:
•Gram positive cocci in chains •Catalase negative (staph is catalase positive!) –catalase to differentiate •Ferment sugars → lactic acid → low pH (not facultative, but aerotolerant) •Need enrichment with blood to support growth |
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6Q:
S. pyogenes |
6A:
Hemolysis- beta Lancefield Grp- A Laboratory test- Bacitracin S |
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6Q:
S. agalactiae |
6A:
Hemolysis- Beta Lancefield Grp- B Laboratory test- Hippurate hydrolysis pos |
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6Q:
Intracoccus faecalis |
6A:
Hemolysis- Gamma Lancefield Grp- D Laboratory test- Bile esculin pos |
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6Q:
S. pneumoniae |
6A:
Hemolysis- Alpha Lancefield Grp- none Laboratory test- Optochin S |
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6Q:
Discuss the structural virulence factors for Streptococcus pyogenes (group A strep) |
6A:
•Capsule - hyaluronic acid •Fibrils - consist of M-protein (80 serotypes) and lipoteichoic acid (extends into environment); M-proteins the biggest thing to worry about. •Peptidoglycan layer- just like all other gram + •T and R proteins |
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6Q:
Discuss the soluble virulence factors for Streptococcus pyogenes. |
6A:
Soluble Virulence Factors •Streptokinase- break clot formations •Streptodornase- breaks down DNA •Hyaluronidase- breaks down hyaluronic capsule •Erythrogenic toxin- like that responsible for Scarlett Fever •Nicotinamide adenine dinucleotidase (NADase) •Streptolysins (hemolysins) •Streptolysin O - oxygen labile, antigenic •Streptolysin S - oxygen stabile, nonantigenic |
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6Q:
M Protein |
6A:
Virulence factor in streptococcus. M protein is strongly anti-phagocytic and is a major virulence factor. |
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6Q:
Discribe the laboratory diagnosis for S. pyogenes. |
6A:
•Pharyngitis –Throat cultures –Direct antigen test- swab infected throat, lyse all the material, look for then soluble antigens with the kit •Invasive infections -Gram stain and culture -Blood culture if bacteremia is suspected •Antibodies to S. pyogenes -Streptozyme test – screen; contains 5 of the antigens contained in grp A strep -testing against a bunch of antigens from group A strep -Antistreptolysin O (ASO) titer - quantitate antibodies to streptolysin O -want to see if Abs are present. See if ASO antigen is bound to an RBC. -all these tests were used to treat rheumatic fever. |
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6Q:
Describe the localized diseases caused by S. pyogenes. |
6A:
•Localized infections •Pharyngitis (sore throat) •Scarlet fever- blanching rash •Impetigo- most common cause |
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6Q:
Describe the invasive infections caused by S. pyogenes. |
6A:
•Wounds •Erysipelas- localized in upper layers of the skin •Cellulitis- invade and goes into deeper layers •Puerperal fever- sepsis and death; ass’d with birth •Endocarditis- less common |
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6Q:
Describe the Postinfection diseases caused by S. pyogenes. |
6A:
•Rheumatic fever- most common one that we’re worried about; ass’d with upper respiratory tract infection •Glumerulonephritis |
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6Q:
Describe Scarlet Fever |
6A:
• Erythrogenic toxin produced by lysogenic Grp A streptococci causes rash -has the genetic material to make the toxic -strawberry tongue - should only get it once if you produce the Abs against it. |
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6Q:
Grp B strep (Streptococcus agalactiae) diseases |
6A:
-Infect neonates; mom may have it as normal flora in vaginal area -Septicemia, meningitis, and pneumonia **think sepsis in a neonate→ think Group B strep |
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6Q:
Grp D strep or Enterococcus (Streptococcus) faecalis diseases |
6A:
-Urinary tract infection (UTI) -Wounds -Sepsis |
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6Q:
Viridans strep or alpha strep diseases |
6A:
-#1 cause of Subacute endocarditis -Dental caries (Steptococcus mutans) |
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6Q:
Streptococcus pneumoniae diseases |
6A:
-#1 cause of community-acquired Pneumonia -#1 cause of Otitis media in children -Sinusitis |
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6Q:
Explain the treatment for streptococcal infection. |
6A:
•Penicillin- effective and inexpensive. •Prevention against rheumatic fever -long acting penicillin G -oral penicillin for 10 days |
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6Q:
List the general characteristics of Pseudomonas aeruginosa. |
6A:
*Gram-Negative Nonfermenters •Motile with polar flagella •Oxidase positive that are obligate aerobes (by definition); test for cytochrome C •Grow at 42oC- most pathogenic organisms grow at 39 degrees •Colonies produce a fruity odor •greening of the agar medium •does not ferment glucose •most common one •long gram – rods •opportunistic pathogen |
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6Q:
Describe the virulence factors possessed by P. aeruginosa. |
6A:
•Pili •Polysaccharide capsule •Endotoxin (lipopolysaccharide)- since they’re gram neg. •Many extracellular enzymes- break down about 200 carb substrates •Exotoxin A -Causes ADP-ribosylation of elongation factor 2 → inhibits protein synthesis •Tissue necrosis |
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6Q:
List the common infections caused by P. aeruginosa. |
6A:
*typically infects those who are immunocompromised or those with compromised physical barriers (burn patients) **almost always associated with water! Ecthyma gangrenosum- from working in the rice paddies •Skin infections following burns •Super infections following use of broad-spectrum antibiotics; happens after the first infection •Wounds •Colonize respirators pneumonia- get into wounds; longer than 5 days on respirator •Colonize respiratory tract in patients with Cystic fibrosis pneumonia •Conjunctivitis •Otitis externa (swimmers ear) •Folliculitis from hot tubs or swimming pools |
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6Q:
Describe the prevention and treatment of infections caused by P. aeruginosa. |
6A:
•Clean and sterilize hospital equipment; replace plastic tubing where possible •Minimize unnecessary broad-spectrum antibiotic therapy and prophylaxis -want a specific therapy for a specific infection; don’t use broad unless you have to •Aminoglycoside + piperacillin or ticarcillin by IV -aggressive antibiotic therapy to kill these things |
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6Q:
Pathogenesis of Group A Strep |
6A:
• Encounter - acquired through another infected individual or a carrier • Spread - Grp A strep highly adapted to resist phagocytosis and spread through tissues; from secretions through mouth or nose to transmit • Damage - elicits a strong inflammatory response –Causes release of chemotaxins for white blood cells –Activate complement by the alternate pathway Resists phagocytosis and kills many of the invading cells. **Lysis of WBC’s → release of lysosomal enzymes → damage to surrounding tissue |
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6Q:
Acinetobacter |
6A:
Oxidase negative (aerobic), nonfermentative, nonmotile, pleomorphic organisms •A. anitratus -Cause a variety of nosocomial infections similar to Pseudomonas -Naturally resistant •A. baumanii -Opportunistic infections -American soldiers wounded in Iraq -Multiple drug resistant (MDRAB) |
