Streptococci and Enterococci

Question 1

What are some key features of acute pharyngitis?

Answer 1

fever, sore throat, headache, cervical lymphadenopathy, exudate; difficult to differentiate from viral infection; 5% asymptomatic carriers; transmitted by respiratory droplets

Question 2

With erysipelas, what is the most affected part of the body?

Answer 2

the legs (used to be the face)

Question 3

What is a key feature of impetigo?

Answer 3

honey crusted lesions

Question 4

True or false: Impetigo and pharyngitis are caused by the SAME strains of S. pyogenes.

Answer 4

False

Question 5

What does the streptokinase virulence factor do?

Answer 5

cleaves fibrinogen and fibrin (“clot buster”) to facilitate spread in infected tissues

Question 6

Scarlet fever is a complication of what?

Answer 6

streptococcal pharyngitis

Question 7

What are some of the key features of scarlet fever?

Answer 7

• rash first appears as tiny red bumps on chest and abdomen 12-48 hours after fever
• accentuation of rash in skin folds (Pastia’s lines)
• circumoral pallor
• sore throat
• fever
• bright red tongue w/ “strawberry” appearance
• desquamation begins after rash fades

Question 8

How does necrotizing fasciitis present?

Answer 8

with malaise, diffuse myalgia, low grade fever, and excruciating pain

Question 9

How does necrotizing fasciitis develop?

Answer 9

It is caused by a S. pyogenes infection deep in the subcutaneous tissues that spreads along the fascial planes, leading to extensive destruction of the muscle and fat. It also leads to systemic toxicity with a mortality rate exceeding 50%.

Question 10

What is Toxic Shock-like Syndrome caused by?

Answer 10

SPEs (Streptococcal Pyrogenic Exotoxins) that are similar to S. aureus TSST-1

Question 11

Which virulence factor is responsible for the rash in scarlet fever?

Answer 11

erythrogenic exotoxin (an SPE)

Question 12

What are the post-streptococcal sequelae we discussed?

Answer 12

• rheumatic fever

- acute glomerulonephritis

Question 13

What are the characteristic lesions associated with rheumatic fever?

Answer 13

cardiac lesions called Aschoff bodies (granulomas)

Question 14

How can we prevent perinatal GBS infection?

Answer 14

Cultures should be performed on vaginal/rectal swabs collected at 35-37 weeks gestation; if mother is found to have GBS, treat her with prophylactic antibiotics.
*Combined vaginal/rectal swab improves isolation rates by 40% over vaginal swab alone

Question 15

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

Answer 15

streptococcus pneumoniae

Question 16

What is a vaccine target for Strep. pneumoniae?

Answer 16

type-specific antibodies to capsular polysaccharide

Question 17

What is the most common clinical presentation of pneumococcal disease among children younger than 2 years?

Answer 17

bacteremia

Question 18

Which member of Bovis group streptococcus is the one to remember and why?

Answer 18

S. gallolyticus ss. gallolyticus (aka, S. bovis biotype I), as it is associated with carcinoma of the colon

Question 19

Vancomycin Resistant Enterococci (VRE) is most often mediated by which species?

Answer 19

E. faecium (plasma-mediated w/ vanA or vanB gene conferring resistance)

Question 20

Which type of atmosphere does Strep prefer? How is this different from Staph?

Answer 20

Strep prefers anaerobic or CO2 atmosphere, while Staph prefers aerobic atmosphere

Question 21

Compare the planes of division of staph and strep.

Answer 21

Strep has only 1 plane of division (perpendicular to long axis of chain), while staph can divide along all 4 planes.

Question 22

Describe the PYR test.

Answer 22

It is a quick spot test that helps identify enterococcus and group A strep. PYR impregnated discs serve as a substrate for detection of pyrrolidonyl peptidase, which will cleave PYR.

Question 23

Which laboratory test is useful for confirming diagnosis of rheumatic fever?

Answer 23

ASO: antibody detection of Anti-Streptolysin O antibodies with latex agglutination (Abs appear 3-4 weeks after initial exposure to group A strep)