Micro Exam 4 Strep/Entero

Lancefield, hemolysis

Strep can be differentiated by ____ groups (group A, B, D) or ____ on agar plate.

Round, negative, chains, hemolysis, aerobic, facultative

Streptococcus is (round/rods), catalase (positive/negative), grow in (clusters/chains), ____ (on agar), (aerobic/anaerobic) and ____ anaerobe.

Encapsulated

Streptococcus, typically only S. pneumonia can be ____.

Staph is catalase positive and grows in clusters

What is the difference between staph and strep?

Beta, hemolysins O and S

What is complete hemolysis? What is it caused by?

S

Is hemolysin O or S stable in oxygen?

Alpha, hydrogen peroxide

What is partial or "green" hemolysis? What is it caused by?

Gamma

What is typically non-hemolytic but may cause some browning of surrounding area?

GBS and GAS

What two strep are beta-hemolytic?

Viridans group strep and S. pneumoniae

What two strep are alpha hemolytic?

S. bovis/gallolyticus, enterococci

What strep is gamma hemolytic? What other species?

Carbohydrate antigens

Lancefield grouping is based on ____ ____ on strep surface.

Streptococcus pyogenes

What species is group A strep?

Streptococcus agalactiae

What species is group B strep?

Streptococcus bovis/gallolyticus, enterococcus

What species is group D strep? What used to belong to this group?

Alpha, mouth, cavities

Viridans group strep (VGS) is typically ____-hemolytic but can be non-hemolytic. They colonize more heavily in the ____ (causing ____).

S. bovis

What strep species was originally put in VGS because t behaves like it in the body but is not clinically classified as VGS?

Exotoxins

GAS (S. pyogenes) is full of ____ that are purposefully released as part of its virulence.

Hyaluronidase, M-protein, streptolysin O, streptolysin S, erythrogenic

GAS (S. pyogenes) virulence:

1. ____ - exotoxin that will help break down cell wall

2. ____-____ - not only binding, limits phagocytosis and complement function

3. ____ ____ - lyses WBC, platelets, RBCs

4. ____ ____ - hemolytic zones on agar plates

4. ____ toxin - rash (ex. Scarlet fever)

Leukocytosis

Streptolysin O lyses WBC, platelets, and RBCs, but there is still a significant ____ from infection because they are lysed when they are trying to engulf strep not just freely engulfed.

Encapsulated, pneumolysin

S. pneumoniae virulence:

1. ____ - protection from antibodies and phagocytic cells

2. Surface proteins

3. ____ - lyses a variety of host cells

Pneumolysin

What virulence factor of S. pneumoniae triggers a MASSIVE immune response?

Mutations, PBPs

Strep can be resistant to beta-lactams. The primary mode is through ____ in ____.

GAS and GBS, GAS

What strep species are associated with skin and soft tissue infection? Which one is specifically associated with necrotizing fasciitis?

GBS

What strep species is associated with neonatal sepsis/meningitis?

GBS, third

Mothers are screened for ____ at the beginning of the ____ trimester to prevent transmission through birth canal causing neonatal sepsis/meningitis.

S. pneumoniae, GAS

What strep species is often associated with otitis media and sinusitis? Strep throat?

S. pnuemoniae

What is the most common bacterial cause of community-acquired pneumonia and meningitis?

Viridans group strep

What strep species is associated with bacteremia and endocarditis?

Native

Viridans group strep is associated with endocarditis of (prosthetic/native) heart valves.

Defined, red, staph

Staph and strep skin and skin structure infections can be differentiated because staph borders are more ____ due to formation of pus pockets while strep is more just ____ skin. If it is an abscess or boil is is more likely (staph/strep).

Fever, white patchy, strawberry tongue, rash, glomerulonephritis

Progression of strep throat:

1. Initial infection, ____, sore throat with ____ ____ appearance resembling EBV

2. Can progress in 2-5 days to a ____ ____ appearance and total body ____

3. If untreated, ~5% of patients will experience a post-strep ____

Trunk, palms, soles

The rash from strep throat often starts on (extremities/trunk) and never extends to ____ and ____

Rheumatic fever

If strep throat is untreated, ~3.5% will develop ____ ____.

M-protein, antibodies, cardiac, skeletal, cytokines, cardiac

Progression of strep throat to rheumatic fever:

1. Cell wall ____-____ of GAS is highly antigenic

2. ____ form against M-protein

3. Antibodies react with ____ myofiber protein and ____ muscles

4. Causes release of pro-inflammatory ____

5. Leading to chronic ____ tissue damage and disease

Valve, thickening, regurgitation, Aschoff, pancarditis

Rheumatic fever can cause:

Erosion of ____ leaflets

(Thinning/thickening) of tissues/valves

Stenosis and ____

____ bodies (lesions in connective tissues)

____

Chorea, months, nodules, arthritis

If left untreated, strep can cause ____ (involuntary movements) several ____ after initial infection, as well as subcutaneous ____ and ____.

GAS

Centor score is a clinical prediction tool to determine the likelihood of ____ pharyngitis in patients presenting with sore throat.

Fever, cough, adults

Centor score criteria are ____, absence of ____, tender anterior cervical lymphadenopathy, and tonsillar exudates. It is only validated in (children/adults).

Biofilm

Strep species (S. mutans) on teeth were one of the first descriptions of ____ formation.

Culture, susceptibilities, rapid, PCR, pneumococcal

Strep diagnostics:

Traditional bacterial ____ and ____

____ strep test - throat swab

Rapid diagnostics with ____

____ antigen testing - blood or urine

100% susceptible to penicillins

Susceptibilities are often not conducted on patients with GAS, GBS, and (most) viridans group strep. Why is this?

Antigens, antibody

The throat swab rapid strep test is detecting ____ from GAS using ____-based reactions.

Cheap, positive

Pneumococcal antigen testing is (cheap/expensive). It is reliable but only when it is (positive/negative) because of low sensitivity.

S. pneumoniae

What strep species has a vaccine?

Streptococcus bovis/gallolyticus

Which strep species, when detected in the bloodstream, should prompt a screening for GI/colon cancer?

Cocci, gamma, diplococci or chains

Enterococcus are round (rod/cocci) and ____-hemolytic. What two arrangements can they be in?

NaCl, Gi tract

Growth in 6.5% ____ differentiates enterococcus (formerly group D) from S. bovis. Where is enterococcus a commensal?

E. faecalis and E. faecium

90%+ Enterococcal infections in humans are secondary to what two species?

IAI, bloodstream, UTI

Enterococci cause ____, although not as common as GN Enterobacterales or GN anaerobes. They also cause ____ infections if they leak from GI tract. They can cause ____, normally involving a Foley catheter.

Endocarditis

Bloodstream infections of Enterococci can lead to ____.

vanA, vanB, lactate, alanine

Enterococcus resistance mechanisms include ____ (most common) and ____ genes linked to vanc resistance. This is the substitution of an AA (____ for ____) not allowing vanc to bind.

ABX

VRE (vancomycin resistant enterococcus) colonization is seen after ____ use (determined by vanA and vanB).

E. faecium, E. faecalis

VRE is way more likely to be (E. faecalis/E. faecium), while (E. faecalis/E. faecium) has 100% susceptibility to ampicillin in Prisma midlands.

PBP, cephalosporins

Enterococci can have a change in ____ resulting in intrinsic resistance to all ____.

Cultures, susceptibilities, rapid

Enterococcus infections can be diagnosed via traditional bacterial ____ and ____ or ____ diagnostics (consistent with other GP organisms discussed).

Yes

Can rapid diagnostics determine the presence of vanA or vanB genes?