Streptococci Flashcards
Streptococci are gram _____ cocci.
Streptocuccus = Gram positive cocci
Streptococcus can be found in _____, _____, or _____ shapes.
Chain, diplococci, clusters (rare)
The types of streptococci are differentiated based on their _____
Hemolytic properties
In _____ hemolysis, erythrocytes are not destroyed, but a greenish discoloration is observed due to the organisms effects on hemoglobin.
Alpha hemolysis
In _____ hemolysis, erythrocytes ARE destroyed, leaving a clearing beneath the organism’s growth.
Beta hemolysis
In _____ hemolysis there is actually NO hemolysis
Gamma hemolysis
Lancefield Classification/Serogrouping of organisms is based on antigenic variation of what two cell wall components?
C-carbohydrates & Glycerol teichoic acid
Which cocci species fit into Lancefield groups A, B, & D, respectively? What hemolysis patterns do they exhibit?
A: S. pyogenes - Beta hemolysis
B: S. agalactiae - Beta hemolysis
D: E. faecalis - Alpha/Beta/No hemolysis
Which two species of strep do not fit into any of the Lancefield serogroups? What hemolysis patterns do they exhibit?
S. pneumonia - Alpha hemolysis
Viridans group - Alpha hemolysis
Group A strep refers to which species?
S. pyogenes
How is S. pyogenes transmitted?
Via respiratory droplet/skin to skin contact
Fomite and insect vector transmission is also possible
Which S. pyogenes virulence factor binds fibronectin and fibrinogen? This virulence factor is also responsible for the generation of antibodies that cause rheumatic fever.
M protein
What are the Streptococcal Pyogenic Exotoxins?
SpeA, SpeB, & SpeC
The streptococcal pyogenic exotoxins act as _____ that interact with macrophages and helper T cells, causing them to release a wide variety of cytokines.
Superantigens
Which two streptococcal pyogenic exotoxins are encoded by lysogenic phages? Which of this is related to Scarlet Fever and TSS?
SpeA & SpeC
SpeA associated with Scarlet Fever and TSS
Which streptococcal pyogenic exotoxin is located on the bacterial chromosome, and is present in ALL group A strep?
SpeB
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?
Necrotizing fasciitis
What are the four criteria of Strep Throat evaluated in order to determine the treatment of a patient?
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.
What are the two main post-Strep sequelae? Why do they happen?
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
_____ 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?
Cellulitis
Path: Organism gets in breaches in skin, then spreads along fascial planes
Tx: Abx
_____ 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?
Impetigo
Tx: Abx
_____ 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?
Erysipelas
Tx: Abx
_____ 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?
Scarlet Fever
Usually preceded by strep throat or impetigo.
The toxin responsible for the rash is SpeA
_____ is a life threatening condition caused by group A strep that is associated with the overproduction of SpeB. It progresses rapidly to _____ followed by _____
Necrotizing fasciitis
Progresses rapidly to STSS followed by multiple organ failure
Which organism falls under the spectrum of group B Strep? What pattern of hemolysis does it demonstrate?
S. agalactiae - Beta hemolysis
T/F Impetigo is a condition that is pathognomonic for Group A strep.
FALSE
Though impetigo can be caused by group A Strep, it can also be caused by other organisms (S. aureus, e.g.)
S. agalactiae is a common colonizer of the human _____.
GU tract
S. agalactiae causes serious disease in what three groups?
Young infants, pregnant women, and older adults
S. agalactiae is the most common cause of _____ and _____ in infants
Sepsis & meningitis
What is the clinical presentation of infants with a S. galactiae infection? What is the most common form of disease?
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)
A higher proportion of women are carriers of GBS in which three groups?
African Americans, women of young maternal age, and nonsmokers
T/F: S. galactiae is not a STI
TRUE
Even though it colonizes the GU, it is not sexually transmitted
T/F: A GBS colonized mother is much more likely to have a colonized newborn than a non-colonized newborn?
FALSE
The chances are 50-50 for the mother to have a colonized or non-colonized newborn
What percentage of GBS colonized newborns will have early onsrt sepsis, pneumonia and meningitis?
2%
What are the four obstetric risk factors for early-onset GBS disease?
1) Preterm delivery
2) Prolonged rupture of membranes
3) Infection of the placental tissues/amniotic fluid
4) Fever during labor
GBS in the mother’s _____ is indicative of heavy colonization, and is a risk factor for early onset GBS disease.
Urine
Describe the appearance of GBS colonies on blood agar
Large mucoid with relatively small zone of hemolysis
T/F: The group B strep test is usually given during weeks 35-37 of pregnancy.
TRUE
A double zone of hemolysis is may be seen with GBS cultured on blood agar if it is _____ after initial incubation
Refrigerated
If hemolysis identifies a possible GBS colony, a _____ test can confirm its presence.
Latex Agglutination
Strep pneumoniae causes two diseases in both adults and children. What are they?
Adults: Pneumonia and Meningitis
Kids: Otitis media and Sinusitis
(M.O.P.S.)
Strep pneumoniae appear as gram _____ cocci in _____.
Do they have a capsule?
Gram POSITIVE cocci in PAIRS.
They are encapsulated
What virulence factor of Strep pneumo facilitates its invasiveness?
Capsule
Strep pneumo colonizes _____ cells and secrete their toxins.
Epithelial cells
What are the four predisposing factors of Strep pneumo pneumonia?
1) Splenic dysfunction
2) Alcoholism
3) Anesthesia
4) Previous infection
Strep pneumo peneumonia is characterized by a productive cough with a _____ sputum.
Bloody/rusty sputum
What pattern of hemolysis does Strep pneumo exhibit?
Alpha hemolysis
What is the treatment for Strep pneumo pneumonia?
Levofloxacin (penicillin), ceftriaxone (fluoroquinolone)
T/F: Vaccination is available for Strep pneumo
TRUE
There are two anti-capsule vaccines available
T/F: Vaccination is available for Strep pneumo
TRUE
There are two anti-capsule vaccines available (contain multiple serotypes of the capsule)
Lab diagnosis of Strep pneumo pneumonia can be accomplished by demonstrating the organism is sensitive to _____
Optochin
In addition to Strep pneumo, what other organism is a common culprit of otitis media in children?
H. influenzae
Treatment for otitis media may include _____ in addition to abx.
Myringotomy
A small incision is made in the tympanic membrane to drain the pus from the middle ear.
After a myringotomy, _____ may be inserted for recurrent infections to relieve pain and pressure and to help in the healing process.
Tympanostomy tube
After a myringotomy, _____ may be inserted for recurrent infections to relieve pain and pressure and to help in the healing process.
Tympanostomy tube
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.
Autolysis of colonies
What three organisms fall under the Viridans Streptococci category?
1) S. mutans (cavities)
2) S. milleri (endoarditis)
3) S. sanguinis (endocarditis)
T/F S. milleri and S. sanguinis are true pathogens
FALSE
They are usually part of normal flora
Patients with poor _____ allow S. sanguinis/milleri to disseminate thru the bloodstream, usually ending up on a heart valve.
Poor dentition/oral hygiene
What is the treatment for a mild SSTI like impetigo? A severe one like necrotizing fasciitis?
Mild (impetigo): Penicillin/Tetracycline
Severe (nec. fasc.): Surgery to cut out tissue, empiric abx like vancomycin
What two organisms fall under the spectrum of Group D Enterococci?
E. faecalis, E. faecium
T/F Group D Enterococci can only survive in specific, hospitable environments.
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
Group D Enterococci are frequently associated with what four conditions? In what two groups are they frequently seen?
1) UTI
2) Biliary tract infxns
3) Septicemia
4) Endocarditis
E. faecalis is resistant to _____, and therefore requires synergistic treatment with _____ and _____.
E. faecalis is resistant to penicillin
Requires synergistic treatment with ampicillin-sulbactam and an aminoglycoside (gentamicin or streptomycin)
E. faecalis possess _____ that encode antibiotic resistance which may be transferred to other bacteria.
Plasmids
E. faecium is resistant to what three drugs? What treatment is used instead?
E. faecium is resistant to vancomycin, ampicillin, and gentamicin
Treatment involves nitrofurantoin or linezolid, with synercid as an alternative
