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Bacteriology > Streptococci > Flashcards

Streptococci Flashcards

1
Q

Streptococci are gram _____ cocci.

A

Streptocuccus = Gram positive cocci

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2
Q

Streptococcus can be found in _____, _____, or _____ shapes.

A

Chain, diplococci, clusters (rare)

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3
Q

The types of streptococci are differentiated based on their _____

A

Hemolytic properties

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4
Q

In _____ hemolysis, erythrocytes are not destroyed, but a greenish discoloration is observed due to the organisms effects on hemoglobin.

A

Alpha hemolysis

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5
Q

In _____ hemolysis, erythrocytes ARE destroyed, leaving a clearing beneath the organism’s growth.

A

Beta hemolysis

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6
Q

In _____ hemolysis there is actually NO hemolysis

A

Gamma hemolysis

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7
Q

Lancefield Classification/Serogrouping of organisms is based on antigenic variation of what two cell wall components?

A

C-carbohydrates & Glycerol teichoic acid

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8
Q

Which cocci species fit into Lancefield groups A, B, & D, respectively? What hemolysis patterns do they exhibit?

A

A: S. pyogenes - Beta hemolysis

B: S. agalactiae - Beta hemolysis

D: E. faecalis - Alpha/Beta/No hemolysis

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9
Q

Which two species of strep do not fit into any of the Lancefield serogroups? What hemolysis patterns do they exhibit?

A

S. pneumonia - Alpha hemolysis

Viridans group - Alpha hemolysis

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10
Q

Group A strep refers to which species?

A

S. pyogenes

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11
Q

How is S. pyogenes transmitted?

A

Via respiratory droplet/skin to skin contact

Fomite and insect vector transmission is also possible

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12
Q

Which S. pyogenes virulence factor binds fibronectin and fibrinogen? This virulence factor is also responsible for the generation of antibodies that cause rheumatic fever.

A

M protein

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13
Q

What are the Streptococcal Pyogenic Exotoxins?

A

SpeA, SpeB, & SpeC

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14
Q

The streptococcal pyogenic exotoxins act as _____ that interact with macrophages and helper T cells, causing them to release a wide variety of cytokines.

A

Superantigens

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15
Q

Which two streptococcal pyogenic exotoxins are encoded by lysogenic phages? Which of this is related to Scarlet Fever and TSS?

A

SpeA & SpeC

SpeA associated with Scarlet Fever and TSS

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16
Q

Which streptococcal pyogenic exotoxin is located on the bacterial chromosome, and is present in ALL group A strep?

A

SpeB

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17
Q

Group A streptococci that overproduce SpeB have a greater tendency to invade and cause tissue destruction? What is a condition that may arise in patients with such an infection?

A

Necrotizing fasciitis

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18
Q

What are the four criteria of Strep Throat evaluated in order to determine the treatment of a patient?

A

1) Tonsilar exudates
2) Tender cervical adenopathy
3) Absence of cough
4) Fever

If 2-4 of these criteria are met, administer a Rapid Strep Test

If positive, treat with abx. If negative, consider an alternative diagnosis.

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19
Q

What are the two main post-Strep sequelae? Why do they happen?

A

1) Acute Rheumatic Fever
a) Due to M protein sharing epitopes with heart muscle
2) Post-Strep Glomerulonephritis (a few theories on this one)
a) Immune complex deposition in glomerular tissue
b) Cross reactivity between unidentified strep antigens and glomerular membrane components
c) Deposition of nephrostreptokinase-plasmin complexes on GBM with subsequent damage by host plasmin

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20
Q

_____ is a condition characterized by diffuse inflammation of connective tissue w/ severe dermal and subQ inflammation that can be caused by group A Strep. Pathogenesis? Tx?

A

Cellulitis

Path: Organism gets in breaches in skin, then spreads along fascial planes

Tx: Abx

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21
Q

_____ is a condition that can be caused by group A Strep that is characterized by honey colored, crusty lesions around the mouth and on the face. Tx?

A

Impetigo

Tx: Abx

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22
Q

_____ is an inflammatory condition caused by group A strep that is characterized by the involvement of the deep layers of skin with a well defined edge. Tx?

A

Erysipelas

Tx: Abx

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23
Q

_____ is a condition that caused by group A strep that presents with a distinctive rash of pink-red spots covering the entire body. It is usually preceded by _____ or _____. What toxin causes the rash?

A

Scarlet Fever

Usually preceded by strep throat or impetigo.

The toxin responsible for the rash is SpeA

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24
Q

_____ is a life threatening condition caused by group A strep that is associated with the overproduction of SpeB. It progresses rapidly to _____ followed by _____

A

Necrotizing fasciitis

Progresses rapidly to STSS followed by multiple organ failure

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25
Q

Which organism falls under the spectrum of group B Strep? What pattern of hemolysis does it demonstrate?

A

S. agalactiae - Beta hemolysis

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26
Q

T/F Impetigo is a condition that is pathognomonic for Group A strep.

A

FALSE

Though impetigo can be caused by group A Strep, it can also be caused by other organisms (S. aureus, e.g.)

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27
Q

S. agalactiae is a common colonizer of the human _____.

A

GU tract

28
Q

S. agalactiae causes serious disease in what three groups?

A

Young infants, pregnant women, and older adults

29
Q

S. agalactiae is the most common cause of _____ and _____ in infants

A

Sepsis & meningitis

30
Q

What is the clinical presentation of infants with a S. galactiae infection? What is the most common form of disease?

A

Sx (At 0-1 days of life): Respiratory distress, apnea, signs of sepsis.

Most common form of disease is bacteremia (pneumonia and meningitis are less common)

31
Q

A higher proportion of women are carriers of GBS in which three groups?

A

African Americans, women of young maternal age, and nonsmokers

32
Q

T/F: S. galactiae is not a STI

A

TRUE

Even though it colonizes the GU, it is not sexually transmitted

33
Q

T/F: A GBS colonized mother is much more likely to have a colonized newborn than a non-colonized newborn?

A

FALSE

The chances are 50-50 for the mother to have a colonized or non-colonized newborn

34
Q

What percentage of GBS colonized newborns will have early onsrt sepsis, pneumonia and meningitis?

A

2%

35
Q

What are the four obstetric risk factors for early-onset GBS disease?

A

1) Preterm delivery
2) Prolonged rupture of membranes
3) Infection of the placental tissues/amniotic fluid
4) Fever during labor

36
Q

GBS in the mother’s _____ is indicative of heavy colonization, and is a risk factor for early onset GBS disease.

A

Urine

37
Q

Describe the appearance of GBS colonies on blood agar

A

Large mucoid with relatively small zone of hemolysis

38
Q

T/F: The group B strep test is usually given during weeks 35-37 of pregnancy.

A

TRUE

39
Q

A double zone of hemolysis is may be seen with GBS cultured on blood agar if it is _____ after initial incubation

A

Refrigerated

40
Q

If hemolysis identifies a possible GBS colony, a _____ test can confirm its presence.

A

Latex Agglutination

41
Q

Strep pneumoniae causes two diseases in both adults and children. What are they?

A

Adults: Pneumonia and Meningitis

Kids: Otitis media and Sinusitis

(M.O.P.S.)

42
Q

Strep pneumoniae appear as gram _____ cocci in _____.

Do they have a capsule?

A

Gram POSITIVE cocci in PAIRS.

They are encapsulated

43
Q

What virulence factor of Strep pneumo facilitates its invasiveness?

A

Capsule

44
Q

Strep pneumo colonizes _____ cells and secrete their toxins.

A

Epithelial cells

45
Q

What are the four predisposing factors of Strep pneumo pneumonia?

A

1) Splenic dysfunction
2) Alcoholism
3) Anesthesia
4) Previous infection

46
Q

Strep pneumo peneumonia is characterized by a productive cough with a _____ sputum.

A

Bloody/rusty sputum

47
Q

What pattern of hemolysis does Strep pneumo exhibit?

A

Alpha hemolysis

48
Q

What is the treatment for Strep pneumo pneumonia?

A

Levofloxacin (penicillin), ceftriaxone (fluoroquinolone)

49
Q

T/F: Vaccination is available for Strep pneumo

A

TRUE

There are two anti-capsule vaccines available

50
Q

T/F: Vaccination is available for Strep pneumo

A

TRUE

There are two anti-capsule vaccines available (contain multiple serotypes of the capsule)

51
Q

Lab diagnosis of Strep pneumo pneumonia can be accomplished by demonstrating the organism is sensitive to _____

A

Optochin

52
Q

In addition to Strep pneumo, what other organism is a common culprit of otitis media in children?

A

H. influenzae

53
Q

Treatment for otitis media may include _____ in addition to abx.

A

Myringotomy

A small incision is made in the tympanic membrane to drain the pus from the middle ear.

54
Q

After a myringotomy, _____ may be inserted for recurrent infections to relieve pain and pressure and to help in the healing process.

A

Tympanostomy tube

55
Q

After a myringotomy, _____ may be inserted for recurrent infections to relieve pain and pressure and to help in the healing process.

A

Tympanostomy tube

56
Q

In lab diagnosis of Strep pneumo, one should recognize the characteristic _____ of colonies. As the organisms die, the colonies fall apart leaving a dimple that characterizes this process.

A

Autolysis of colonies

57
Q

What three organisms fall under the Viridans Streptococci category?

A

1) S. mutans (cavities)
2) S. milleri (endoarditis)
3) S. sanguinis (endocarditis)

58
Q

T/F S. milleri and S. sanguinis are true pathogens

A

FALSE

They are usually part of normal flora

59
Q

Patients with poor _____ allow S. sanguinis/milleri to disseminate thru the bloodstream, usually ending up on a heart valve.

A

Poor dentition/oral hygiene

60
Q

What is the treatment for a mild SSTI like impetigo? A severe one like necrotizing fasciitis?

A

Mild (impetigo): Penicillin/Tetracycline

Severe (nec. fasc.): Surgery to cut out tissue, empiric abx like vancomycin

61
Q

What two organisms fall under the spectrum of Group D Enterococci?

A

E. faecalis, E. faecium

62
Q

T/F Group D Enterococci can only survive in specific, hospitable environments.

A

FALSE

Enterococci are some tough motherbuggers.

They:

Grow in pH 4-10

Survive in 40% bile, at a temperature range of 5-50 degrees Celsius (30 minutes at 60 degrees)

Refractory to metal salts

Grow in 6.5% NaCl

63
Q

Group D Enterococci are frequently associated with what four conditions? In what two groups are they frequently seen?

A

1) UTI
2) Biliary tract infxns
3) Septicemia
4) Endocarditis

64
Q

E. faecalis is resistant to _____, and therefore requires synergistic treatment with _____ and _____.

A

E. faecalis is resistant to penicillin

Requires synergistic treatment with ampicillin-sulbactam and an aminoglycoside (gentamicin or streptomycin)

65
Q

E. faecalis possess _____ that encode antibiotic resistance which may be transferred to other bacteria.

A

Plasmids

66
Q

E. faecium is resistant to what three drugs? What treatment is used instead?

A

E. faecium is resistant to vancomycin, ampicillin, and gentamicin

Treatment involves nitrofurantoin or linezolid, with synercid as an alternative

Bacteriology (19 decks)

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