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30 Cards in this Set
- Front
- Back
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Which bacteria are G+ with branching filaments? How do you distinguish them? |
- Actinomyces (anaerobe, not acids fast)
- Nocardia (aerobe, acid fast) |
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Which bacteria are G+ rods? How do you distinguish some of them?
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- Clostridium (anaerobe)
- Corynebacterium - Listeria - Bacillus (aerobe) - Mycobacterium (acid-fast) |
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How do you distinguish the G+ cocci?
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- Catalase test
- Coagulase test - Hemolysis |
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Which bacteria are G+ and catalase +? How do you distinguish them?
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Staphylococcus (clusters)
- Coagulase +: S. aureus - Coagulase -: Novobiocin sensitive S. epidermidis and Novobicin resistant S. saprophyticus |
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Which bacteria are G+ and catalase -? How do you distinguish them?
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Streptococcus (chains)
- Distinguish based on hemolysis |
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Which bacteria are G+, catalase +, and coagulase +? Organization?
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S. aureus - cocci in clusters
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Which bacteria are G+, catalase +, and coagulase -? Organization?
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Clusters of cocci: |
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Which bacteria are G+, catalase -, and have partial hemolysis (green)?
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α-hemolytic Streptococcus (chains)
- S. pneumoniae - Viridans streptococci |
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Which bacteria are G+, catalase -, and have complete hemolysis (clear)?
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β-hemolytic Streptococcus (chains) |
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Which bacteria are G+, catalase -, and have no hemolysis?
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γ-hemolytic Streptococcus (chains)
- Group D: Enterococcus - E. faecalis - Non-enterococcus: S. bovis |
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What are the types of hemolysis?
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- α-hemolysis: partial (forms green ring around colonies on blood agar)
- β-hemolysis: complete (forms clear area of hemolysis on blood agar) - γ-hemolysis: none |
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What does α-hemolysis mean? What are the types of bacteria that fall under this category?
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Partial hemolysis (green ring around colonies on blood agar)
*Streptococcus pneumoniae - Catalase (-) - Optochin sensitive - Capsule - Bile soluble (lysed by bile) *Viridans streptococci (eg, S. mutans) - Catalase (-) - Optochin resistant - No capsule - Bile insoluble (not lysed by bile) "OVRPS (overpass): Optochin - Viridans is Resistant; Pneumoniae is Sensitive |
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What does β-hemolysis mean? What are the types of bacteria that fall under this category?
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Comlete hemolysis (clear area around colonies on blood agar)
*Streptococcus pyogenes - Group A Strep - Catalase (-) - Bacitracin sensitive *Streptococcus agalactiae - Group B Strep - Catalase (-) - Bacitracin resistant "B-BRAS: Bacitracin - group B is Resistant, group A is Sensitive" *Staphylococcus aureus - Catalase (+) - Coagulase (+) *Listeria monocytogenes - Tumbling motility - Meningitis in newborns - Unpasteurized milk |
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What does γ-hemolysis mean? What are the types of bacteria that fall under this category?
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No hemolysis
*Enterococcus (E. faecalis) - Grows in bile and 6.5% NaCl - Group D *Non-Enterococcus (S. bovis) - Grows in bile, not 6.5% NaCl |
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What does the "on the office's "staph" retreat, there was no stress" mnemonic mean?
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Staphylococcus - NO StRESs:
Novobiocin - - Saprophyticus is Resistant - Epidermidis is Senstive |
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What does the "overpass" mnemonic indicate?
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OVRPS:
Optochin - Viridans is Resistant - Pneumoniae is Sensitive |
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What does the "B-BRAS" mnemonic indicate?
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B-BRAS
Bacitracin - Group B strep are Resistant - Group A strep are Sensitive |
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Which bacteria:
- G+ cocci in clusters - Protein A (virulence factor) |
Staphylococcus aureus
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Which virulence factor does Staphylococcus aureus use? Mechanism?
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Protein A:
- Binds Fc-IgG - Inhibits complement activation and phagocytosis |
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Where does Staphylococcus aureus colonize / infect?
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- Commonly colonizes: nose
Inflammatory Disease: - Skin infections - Organ abscesses - Pneumonia (often after influenza virus infection) - Endocarditis - Osteomyelitis |
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What does Staphylococcus aureus cause?
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Inflammatory Disease:
- Skin infections - Organ abscesses - Pneumonia (often after influenza virus infection) - Endocarditis - Osteomyelitis Toxin-Mediated Disease - Toxic Shock Syndrome (TSST-1) - Scalded Skin Syndrome (Exfoliative Toxin) - Rapid-onset food poisoning (enterotoxins) MRSA (Methicillin-Resistant S. aureus) - Important cause of serious nosocomial and community-acquired infections - Resistant to methicillin and nafcillin because of altered penicillin binding protein |
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What are the toxin mediated diseases of S. aureus? Toxin?
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- Toxic Shock Syndrome (TSST-1)
- Scalded Skin Syndrome (Exfoliative Toxin) - Rapid-onset food poisoning (enterotoxins) |
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What is an important cause of serious nosocomial and community-acquired infections?
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MRSA (Methicillin-Resistant S. aureus)
- Resistant to methicillin and nafcillin because of altered penicillin binding protein |
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What is TSST? Mechanism of action? What does it cause?
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Toxic Shock Syndrome Toxin → Toxic Shock Syndrome
- Superantigen that binds to MHC II and T-Cell Receptor - Results in polyclonal T-cell activation - Presents as fever, vomiting, rash, desquamation, shock, and end-organ failure |
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What predisposes to Toxic Shock Syndrome?
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Use of vaginal or nasal tampons
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Which bacteria causes rapid food poisoning? Mechanism?
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S. aureus food poisoning is due to ingestion of preformed toxin (enterotoxins)
- Short incubation period (2-6 hours) - Enterotoxin is heat stable → not destroyed by cooking |
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How does S. aureus form an abscess?
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Forms fibrin clot around itself → abscess
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Which bacteria is known for infection prosthetic devices and IV catheters? Mechanism?
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Staphylococcus epidermidis
- Produces adherent biofilms to these medical devices |
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Characteristics of Staphylococcus epidermidis?
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Catalase (+), Coagulase (-) |
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Which bacteria are the first and second most common cause of uncomplicated UTI in young women?
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1. E. coli
2. Staphylococcus saprophyticus |
