Lecture 52 - Gram + Pyogenic cocci: Strep and Enterococci

Question 1

Strep and Enterococci are ______ anaerobes that are Fastidious (require nutrient rich media to grow).

Answer 1

Facultative anaerobes

Question 2

What is the difference between alpha, beta, and gamma hemolysis, and how do bacteria capable of each appear on blood agar?

Answer 2

Alpha –> partial hemolysis, so green halo around bacteria

Beta –> complete hemolysis, so cleared zone around bacteria

Gamma –> no hemolysis, so no special effect.

Question 3

Strep ____ and ____ are both Beta hemolytic, while Strep _____ and Viridans Strep are Alpha hemolytic.

Answer 3

Pyogenes and Agalactiae

Pneumoniae

Question 4

There are a couple ways to distinguish between pyogenes and agalactiae. The first is a _____ group test that uses Abs specific to carbohydrates present on the cell walls of the respective bacteria. _____ have Group A carbs, while ______ have Group B.

Another test is Bacitracin sensitivity test. _____ is typically sensitive, while _____ is resistant.

Another test is the PYR test that tests for an amino peptidase. _____ is positive for the amino peptidase, while _____ is negative.

Answer 4

Lancefield Group test

Pyogenes have group A

Agalactiae have group B

Pyogenes is bacitracin sensitive

Agalactiae is resistant

Pyogenes is + for the amino peptidase

Agalactiae is negative

Question 5

Strep pyogenes is a Group ___, ___-hemolyitic bacteria that can invade intact skin or mucous membranes. It has many virulence factors including:

___ protein that prevents phagocytosis.

____ase, which destroys secratory ____, allowing the bacteria to adhere to target cells in mucous membranes.

___a peptidase, which blocks compliment activation.

Answer 5

Group A, Beta-hemolytic

M protein

IgAase

secratory IgA

C5a

Question 6

Strep pyogenes produces 3 Streptococcal Pyogenic Exotoxins (SPEs). Which ones act as superantigens and which one acts as a cysteine protease on capillaries and causes Scarlet Fever Rash?

Answer 6

SPE-A and C are Superantigens

SPE-B is the cysteine protease

Question 7

Impetigo, Erysipelas, and Cellulitis are all possible skin infections from Strep. Of the three, which is considered contagious and why? Look for these infections in the face and legs, and keep in mind the _______ rash has well defined edges while _____ does not.

Answer 7

Impetigo is considered contagious because it is localized to the outer layer of skin, epidermis. Erysipelas and Cellulitis are deeper, in the dermal and subcutaneous layers, so they can’t spread via contact.

Erysipelas

Cellulitis

Question 8

SPE-producing Step strains can cause TSLS secondary to _______ (one of the Strep skin infections), because the SPE-__ and SPE-__ toxins enter the blood and act as superantigens.

Answer 8

Erysipelas

SPE-A and SPE-C

Question 9

Following infection with Strep pyogenes, some patients suffer Acute Rheumatic Fever from Abs they form against the non-variable region of the pyogenes _____ protein. Its structure is very similar to cardiac _____, so the Abs recognize self-tissue. This is called _____ mimicry. These patients need to be put on prophylactic antibiotics for about ____ years to prevent subsequent infection, which would elicit a more intense Acute Rheumatic Fever.

Answer 9

M protein

Cardiac Myosin

Antigen mimicry

10 years

Question 10

Acute _________ is a post-infection sequela of Strep pyogenes infection (pharyngitis and impetigo) that results from deposition of ______ complexes on the renal basement membrane.

Answer 10

Acute Glomerulonephritis

Immune complexes

Question 11

Strep agalactiae is part of the normal flora of the ____ and ____ and infections are most common in women (this could be a problem for neonates born from an infected mother.)

Answer 11

GU and GI

Question 12

A good way to distinguish Enterococcus faecalis + Strep bovis (both are Group ___ on Lancefield Group test) from Strep pneumoniae + Viridans Strep is via _____ test. The former two are positive and will show dark agar on testing bc of hydrolysis, while the latter two are negative and the agar stays red-pink.

Answer 12

Group D

Esculin test

Question 13

The way to distinguish Enterococcus faecalis from Strep bovis is by plating them on 6.5% NaCl agar. Which one will grow?

Answer 13

Enterococcus faecalis will grow.

Question 14

Strep bovis is also called gallolyticus. It is part of the normal flora in the _____ and infection is often associated with malignancy or a pre-malignant lesion in the _____ (remember the interplay between inflammation and malignancy.)

Answer 14

GI

Colon

Question 15

Enterococcus faecialis and faecium are part of the normal flora in the GU and ___. Which one shows a rapid spread of drug resistance to other Enterococci? Treatment uses a combination of penicillin and ______.

Answer 15

GI

Faecium

Aminoglycosides

Question 16

To distinguish Strep pneumoniae from the rest, an ______ sensitivity test is used. Strep pneumonia is sensitive to it and will be killed when exposed to it. “_______ is the Potion for Strep Pnemoniae.”

Answer 16

Optochin

“Optochin is the Potion for Strep Pneumoniae”

Question 17

Strep ______ is alpha hemolytic and is among the Viridans, and is the one that is mainly responsible for dental caries (cavities).

Answer 17

Mutans

Question 18

Strep pneumoniae is ___ hemolytic and always appears as pairs of cocci (diplococci). Remember it is sensitive to _____ (….is the Potion) and is _____ soluble. Strep pneumoniae infection is associated with ______ (lobar or bronchiolar?) pneumonia (rusty-colored sputum), ____ media, and meningitis. Because Strep pneumoniae is mostly capsulated, people who have had their ____ removed are particularly susceptible.

Answer 18

Alpha hemolytic

Optochin

Bile soluble

Lobar pneumoniae

Otitis media

Spleen