IDT202 Flashcards
Defining characteristics of S. pyogenes
1) facultative anaerobic
2) gram positive cocci in long chains
3) beta-hemolysis (complete hemolysis)
4) Group A antigen - C-carbohydrate
What is S. progenes sometimes referred to as?
Group A Streptococci (GAS)
What is lance field Group B (GBS) strep called?
streptococcus agalactiae
What are group D streptococci ?
Enterococcus faecalis
What is the major antigenic virulence factor in streptococci?
M-protein; it confers resistance to neutrophil and macrophage phagocytosis
is a strain lacking M-protein virulent?
no
What are the major forms of strep that are discussed?
1) S. pyogenes
2) S. pneumoniae
3) Enterococcus spp
4) S. agalactiae
What are the defining features of streptococcus pneumoniae?
1) gram-positive diplococci
2) alpha-hemolysis
3) lancet shape on gram stain
4) polysaccharide capsule (virulence factor)
What kind of strep is found in the throat?
- viridans strep
- S. pneumoniae
- S. pyogenes
what kind of strep is found in the intestine?
enterococcus faecalis
What kind of strep is found on the skin?
Group A, Group B (vagina)
GBS
S. agalactiae
GAS
S. pyogenes
When doing a throat swab, what structure is swabbed?
tonsils
How are GAS further sub-divided?
by their M-protein reactivity
What types of disease can be caused by M type GAS’s?
1) rheumatic fever (rheumatogenic)
2) acute glomerulonephritis (nephritogenic)
How des Enterococcus spp look on gram stain?
pairs or chains
what are distinguishing characteristics of Enterococcus spp?
1) gamma-hemolysis (non-hemolytic)
2) facultative anaerobes
What are 2 bacteria found in the intestines of humans ?
1) E. faecalis (90%)
2) E. faecium (5-10%)
what are the clinical syndromes that are caused by S.pyogenes (9)?
1) streptococcal pharyngitis
2) scarlet fever (SF)
3) infectious impetigo
4) erysipelas
5) cellulitis
6) streptococcal toxic-shock syndrome
7) necrotizing fasciitis
8) post-streptococcal acute rheumatic fever (PS-ARK)
9) post-streptococcal acute glomerulonephritis (PS-AGN)
What are examples of mild S. progenies infections ?
1) pharyngitis (“strep throat”)
2) impetigo - localized skin infection
what clinical syndrome caused by GAS is associated with extensive toxin release?
1) scarlet fever
2) toxic shock syndrome
What clinical syndrome caused by GAS is associated with invasion and multiplication in the fascia?
necrotizing fasciitis
What does ‘colonization’ mean ?
attachment, growth and multiplication without triggering body defences; no signs and symptoms
What does ‘disease’ mean?
colonization plus body defences active to try to limit further growth/multiplication which leads to signs and symptoms
What are the virulence properties of streptococcus pyogenes ?
1) M-protein - anti-phagocytic
2) lipoteichoic acid - adherence
3) Exotoxin A
4) hemolysins
5) hyaluronidase
6) streptokinase
What virulence factor of GAS facilitates rapid spread of skin infections?
hyaluronidase because it degrades hyaluronic acid which is the ground substance of subcutaneous tissue
How does one treat GAS - strep throat and strep pharyngitis?
penicillin or amoxicillin; macrolide if penicillin allergic
How does Rheumatic fever present?
appears several weeks following initial streptococcal infection, inflammation of the joints and/or heart following an episode of streptococcal pharyngitis.
what types of infections does S. pneumoniae cause?
upper and lower respiratory infections e.g
1) acute sinusitis
2) otitis media
3) pneumonia
4) bronchitis
what does enterococcus normally cause?
1) UTIs (hospital-acquired infections or in the elderly)
2) bacteremia
3) bacterial endocarditis
4) diverticulitis
what bacteria is the major cause of upper and lower respiratory infections?
S. pneumoniae
How do you treat community acquired pneumonia?
With a macrolide/respiratory fluoroguinolone
How do you treat urinary tract infections?
amoxicillin/ampicillin
How do you treat invasive disease (intra-abdominal infections, endocarditis)?
ampicillin/gentamicin
how do you treat otitis media and sinusitis?
amoxicillin and macrolide if allergic to penicillin
what is a super antigen?
exotoxins are a subgroup of super antigens
True or False: Colonization is necessary but may not be sufficient for disease development
TRUE
How can S. pneumoniae infections be treated?
with oral penicillins, IV penicillins, 2nd and 3rd gen cephalosporins, macrolides, or respiratory fluoroquinolones
What antibiotic can treat vancomycin-resistance enterococcus (VRE)?
linezolid or daptomycin
What can be used to treat group D strep if patient is beta-lactam allergic?
vancomycin
how are enterococcal infections frequently treated>?
with intravenous ampicillin or oral amoxicillin with or without an amino glycoside
