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Microbiology > Streptococcal > Flashcards

Streptococcal Flashcards

1
Q

Catalase (-) GM (+) bacteria

A

Streptococcus and Enterococcus

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2
Q

Streptococcus characteristics

A

Gram (+) cocci. Facultative and capnophilic. Fastidious species

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3
Q

Hemolysis of Strep

A

Beta: complete. Alpha: partial. Gamma: none.

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4
Q

Color of hemolysis strep

A

Beta: yellow. Alpha:green. Gamma: white.

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5
Q

Group A Strep (GAS)

A

Only Strep. Pyogenes. Associated with pyogenic infections. Catalase (-). Pronounced beta hemolysis. Requires enriched medium

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6
Q

Epidemiology of S. pyogenes

A

Respiratory droplets. Crowding populations. Deaths usually due to post-infection complications.

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7
Q

Seasonal diseases of S. pyogenes

A

Pharyngitis in winter. Pyoderma in summer

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8
Q

Virulence factors in S. pyogenes

A

Capsule. LTA. M protein. M-like protein. F-protein.

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9
Q

Lipoteichoic Acid

A

Binds to epithelial cells. Accounts for 60% of adhesin

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10
Q

M protein

A

Adhesin. Antiphagocytic. Degrades C3b. Anchored in cell wall/extends to surface with variable sequenece at the distal end. Plasma fibrinogens binds to M-proteins, thus preventing complement activation/opsonization.

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11
Q

M-like protein

A

Binds IgG and IgM. Antiphagocytic

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12
Q

F protein

A

Mediates adherence to epithelial cells and internalization

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13
Q

Viral vs bacterial pharyngitis

A

Viral = 3Cs. Bacterial leads to abcess.

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14
Q

Non-suppurrative complications

A

Rheumatic fever: encapsulated and rich in M proteins.. Acture glomerulonephritis. Typically 1-3 weeks after acute pharyngitis.

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15
Q

Scarlet fever

A

GAS produces erythogenic toxins from lysogenic phi. Diffuse erythematous rash. Strawberry tongue. Rash will disappear in 5-7 days. Signals infaction by harmful GAS.

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16
Q

3 toxin types of S. pyrogenic

A

Exotoxins A, B, C

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17
Q

S. impetigo/pyoderma

A

more common in the summer. Skin colonization preceds clinical infection. Usually in face and legs (minor traumas get infected). S. aureus is main cause, strep pyogenes is second major cause.

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18
Q

Cellulitis

A

Infection involving skin and subQ.

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19
Q

Erysipelas

A

Form of cellulitis, aka butterfly rash.

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20
Q

Necrotizing Fascilitis

A

GAS responsible for 60%. Aka hemolytic strep gangrene. Involves deep fascia.

21
Q

TSS and strep

A

Likely in pts w/ bacteremic GAS. (Always in NF pts). S. pyrogenic exotoxins act as super antigens. Resembles Staph TSS

22
Q

Paricarditis causes in ARF/RHD

A

M proteins cause IgG to cross react with heart proteins. Antibiotic prophylaxis is needed.

23
Q

Identification of S. Pyogenes

A

Beta hemolytic, catalase negative, bacitracin A disc sensitive

24
Q

Only strep that gives a positive PYR test

A

S. Pyogenes

25
Q

Strep. Agalactiae

A

Group B strep. Typical in woman urogenital track. Is a risk factor for postpartum sepsis. Babies can aquire it easily

26
Q

Virulence factors of S. Agalactiae

A

9 capsular polysaccharide types.

27
Q

Diseases of S. Agalactiae

A

Usually older/immunocompromised pts. UTI during/immediately after pregnancy. Puerperal sepsis**

28
Q

Puerperal sepsis

A

Serious septicemia during or shortly after childbirth. More rare in developed countries

29
Q

Identification of S. Agalactiae

A 
CAMP test (98-100% positive)
Bacitracin susceptibility (92% resistant)
30
Q

CAMP test

A

Positive test is hemolysis where the 2 strains intersect (S. Agalactiae and S. Aureus)

31
Q

Viridans Strep

A

Most produce a green pigment on blood agar. Prevalent in the oral cavity and URT.

32
Q

Important Viridans Strep

A 
Strep:
Mitis
Mutans
Salivarius
Sanguis
33
Q

Disease states of viridans strep

A

Sub-acute endocarditis, meningitis, pneumonia. (Dental procedures with preexisting cardiac lesions)

34
Q

Major cause of pneumonia in 1880s

A

S. Pneumoniae

35
Q

Characteristics of S. Pneumoniae

A 
Gram positive coccus
Diplococci
Fastidious (need blood/serum)
Growth enhanced bby CO2
Causes alpha hemolysis on blood agar
36
Q

Leading cause of bacterial sinusitis/middle ear infections

A

S. Pneumoniae

37
Q

Virulence of S. Pneumoniae

A

Can colonized UR with surface adhesins. Produces sIgA protease and pneumolysin (Ply) that kills the ciliated epithelial cells/phagocytes. Lysis causes edema, hemorrhage, bacterial growth.

38
Q

Capsule of S. Pneumoniae

A

Essential for virulence factor. Inhibits phagocytosis and complement pathways

39
Q

Diseases associated with S. Pneumoniae

A

Co-inflection with influenza. Pneumonia, Meningitis, Otitis media, sub-acute endocarditis

40
Q

Bacterial Pneumonia

A

Typically preceded by viral infection. High fever, productive cough, PMNs/lancet shaped diplococci, “rusty” sputum from blood leaks in capillaries. Usually lobar presentation (round in kids).

41
Q

Otitis Media

A

Infection of middle ear/sinusitis. Leading cause of OM is S. Pneumoniae! Pain and fever very common.

42
Q

3 most common causes of otitis media

A

S. Pneumoniae
Moraxella Catarrhalis
Haemophilus Influenzae

43
Q

Bacterial Meningitis and S. Pneumoniae

A

CSF: purulent, high protein, low glucose.
Severe neurological defects in survivors
Most severe bacterial meningitis

44
Q

Identification of S. Pneumonia

A

Catalase negative, bile soluble, optochin sensitive, susceptible to optochin (P disc). Can be tested for in urine. ELISA is 100% in CSF.

45
Q

Enterococcus Characteristics

A

Gram positive, usually pairs or short chains. Resistant to bile**. High salt, highly antibiotic resistant (Vanco-VRE).

46
Q

Epidemiology of Enterococcus

A

Nosocomial is very common. Typical in GI and gut.

47
Q

Most common Enterococcus diseases

A

UTI* mainly nosocomial
Peritonitis (after surgery/abdominal trauma)
Endocarditis (persistent bacteremia)

48
Q

Identification of Enterococcus

A

High salt/bile/temp
Do not lyse RBCs
Positive Pyr test

49
Q

Anaerobic cocci

A

Part of normal flora of oral, GI tract, Genitourinary tract, skin. Susceptible to common antibiotics. Easily treated if identified as anaerobic cocci.

Microbiology (10 decks)

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