Term
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Definition
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Term
streptococcus general characteristics |
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Definition
gram positive coccus (pairs or chains)
facultative anaerobes
capnophilic
fastidious (complex nutritional requirements) |
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Term
streptococcus species differentiation methods (3) |
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Definition
1. serologic properties (lancefield groupings: A-W)
2. hemolysis (alpha-partial; beta-complete; gamma-absent)
3. biochemical & physiological properties |
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Term
streptococcus: group A (GAS) |
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Definition
group A antigen in cell wall (plus other additional type-specific (M & T) antigens)
PYR positive
catalase negative
bacitracin susceptible
beta hemolytic
associated w/ pyogenic (pus generating) infections |
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Term
streptococcus pyogenes:
colonization & transmission |
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Definition
asymptomatic URT colonization; transient skin colonization
person --> person via respiratory droplets
incr risk: crowding in daycare/classrooms
"flesh-eating bacteria" |
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Term
at risk patients for streptococcus pyogenes infection |
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Definition
pharyngitis: 5-15 yoa; winter (RF/AGN)
pyoderma: 2-5 yoa (w/ poor hygiene); summer
TSS: pts w/ soft tissue infection & bacteremia
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Term
streptococcus pyogenes virulence factors (5) |
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Definition
1. capsule (antiphagocytic)
2. LTA (binds epithelial cells ~60% of adhesion)
3. M protein (adhesion; antiphagocytic; degrades C3b)
4. M-like protein (bind IgG & IgM; antiphagocytic)
5. F protein (mediate adhering to epithelial cells & internalization) |
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Term
streptococcus pyogenes: M proteins (virulence factor) |
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Definition
most important virulence factor for GAS infection
>120 serotypes (some w/ epitopes similar to heart tissue proteins)
structure: fibrillar (anchored in cell wall --> surface --> binds plasma fibrinogen => prevent complement activation/opsonization)
sequence: constant proximally, variable distally
*PCR/sequencing of variable region used to serotype
M antibody (only for particular serotype): may overcome phagocytic resistance |
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Term
types of GAS infections (2) |
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Definition
1. suppurrative
pharyngitis, scarlet fever, pyoderma, erysipeias, cellulitis, necrotizing fasciitis, streptococcal toxic shock syndrome
2. non-suppurrative
rheumatic fever & acute glomerulonephritis |
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Term
pharyngitis (strep throat) |
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Definition
common age groups: 5-15 (20-40% of cases)
transmission: respiratory droplets & close contact (esp winter)
progression: 1-4 d incubation --> sore throat; fever; chills; malaise
suppurative complications: peritonsillar OR retropharyngeal abscess *rare w/ early antibiotic treatment
non-supp complications: RF & AGN
diagnosis: rapid strep test + culture
*collecting sample: rub swab over both tonsillar pillars |
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Term
scarlet fever (most characteristics of disease) |
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Definition
streptococcus pyogenes disease (erythrogenic toxin encoded by lysogenic)
cause: streptococcal pyrogenic exotoxins A, B, & C
(toxins spreads via blood --> localizes in skin => diffuse erythematous rash)
progression: initially, rash on upper chest & tongue is furred --> later, tongue is white/red/strawberry --> rash to extremities (esp abdomen & skin folds) --> rash disappears (5-7 d) --> desquamation
*rash rarely on perioral, palm, & sole areas; suppuration rare
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Term
what is important about the scarlet fever rash? |
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Definition
it is generally not serious except that it signals a harmful S. pyogenes infection AND is evidence that a hypersensitivity reaction is occurring (requires prior toxin exposure)
*scarlet fever currently rare (unknown) however toxin producing GAS still prevalent |
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Term
most common bacterial infection causing impetigo/pyoderma |
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Definition
1. staphylococcus aureus (perhaps due to penicillin resistance)
2. streptococcus pyogenes
*skin colonization w/ GAS (minor trauma) precedes clinical infection |
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Term
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Definition
similarities: local signs of inflammation (warmth, erythema, & pain); fever; lymphangitis; lymphadenitis *streptococcus pyogenes
differences:
cellulitis - infection of skin/subcut tissue <= traumatic/surgical wound/insect bite; no apparent entry site
erysipelas - a form of cellulitis; more erythema/elevation; malar area of face => butterfly rash |
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Term
necrotizing fasciitis (NF) |
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Definition
hemolytic streptococcal gangrene (streptococcus pyogenes) *GAS infection ~60% NF cases
affected areas: superficial and/or deep fascia
progression: like cellulitis --> bullaes gangrene; systemic signs (extensive necrosis, obstructed blood supply, inflam fluid along fascial lines)
treatment: extensive debridement & antibiotic treatment |
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Term
streptococcal toxic shock syndrome |
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Definition
*seen in bacteremic pts w/ GAS
cause: streptococcal toxins (superantigens)
presentation: like StaphTTS (fever, malaise, hT, multiple organ failure)
diagnostic criteria existis to differentiate bt/w staph and GAS TSS (created in 1993) |
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Term
name the two post infection complications of GAS disease - when do they occur? |
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Definition
1. acute rheumatic fever/rheumatic heart disease (RF/RHD)
2. acute glomerulonephritis (AGN)
*1-3 wks after acute illness |
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Term
what are ARF & RHD, describe its epidemiology, w/ which GAS disease is it associated? |
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Definition
*nearly ONLY after URT infection (pharyngitis- SLO not inactivated in pharynx => antibody response)
multisystem disease (autoimmune rxn to GAS)
all symptoms resolve EXCEPT cardiac valvular dmg (in RHD)
more common location: under-developed/developing countries |
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Term
mechanism/presentation/tx/dx of ARF/RHD |
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Definition
rheumatogenic GAS: encapsulated; rich in immunogenic M proteins (many epitopes are similar to human tissue proteins)
human ex. myosin, tropomyosin, laminin, actin, keratin
*anti-M IgG cross react w/ heart proteins => pancarditis
ARF presentation: subcut nodules/arthralgia --> arthritis
tx: antibiotic phrophylaxis (to prevent subseq GAS infect)
dx: evidence of recent GAS infection; modified Jones Criteria; anti-SLO for RF |
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Term
AGN: w/ which GAS disease does it associate? dx? recurrence? tx? mechanism? presentation? |
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Definition
pharyngitis AND skin infections (streptolysin O inactivated in skin => NO antibody response
dx: anti-DNaseB for AGN
recurrence unlikely, as only 4-5 M strains => AGN
therefore, do NOT use antibiotic prophylaxis (will not likely be necessary to prevent subseq infe)
mechanism: Ag-Ab-complement complexes on glomerular basement membrane --> glom cap filled w/ monocytes & PMN
presentation: acute inflamm, HT, hematuria, proteinuria, etc. |
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Term
how to culture for streptococcus pyogenes? |
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Definition
culture w/ sulfamethoxazole-trimethoprim to inhibit normal flora |
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Term
how to identify streptococcus pyogenes? |
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Definition
PYR test positive (pyogenes is the only streptococci to => positive result)
optochin resistant (P disk)
bacitracin sensitive (A disk) |
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Term
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Definition
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Term
staphylococcus agalactiae: group, characteristics, epidemiology, & virulence factors |
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Definition
GBS
gram+, facultative, beta-hemolytic, long chains
normal flora of GIT/GUT
mothers-->babies<--other babies
women w/ genital colonization: higher risk for postpartum sepsis
virulence: undefined (capsule, PG, DNases, hyaluronidase, hemolysins)
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Term
some diseases that can be caused by streptococcus agalactiae:
men and non-pregnanat women |
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Definition
bacteremia, pneumonia, bone/skin/soft tissue infections
higher risk: older; pts w/ debilitating underlying disease |
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Term
which group of streptococcus causes more serious infections? |
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Definition
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Term
diseases caused by streptococcus agalactiae:
pregnant women |
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Definition
UTI: during/immediately following pregnancy
endometritis: after delivery
chorioamnionitis: w/ heavy 2nd trimester colonization
puerperal sepsis (rare serious septicemia in pregnant mother): during/shortly after childbirth; starts w/ puerperal fever |
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Term
early onset neonatal disease (streptococcus agalactiae) |
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Definition
mortality rates now decr (5%)
15-30% of survivors from meningitis have lasting complications (eg. blindness, deafness)
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Term
most common cause of meningitis in neonates |
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Definition
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Term
pathogenesis of S. agalactiae disease in newborns |
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Definition
time of acquisition => early or late onset
(happens @ time of birth OR w/ aspiration of infected amniotic fluid)
newborns have few alveolar macrophages, poor PMN chemotaxis/phagocytosis
bacterial cell wall components => sepsis (systemic hT, hypoxia) |
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Term
late onset neonatal disease (streptococcus agalactiae) |
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Definition
> 7 d after birth
transmission: from infected mother or nosocomial
characterized by: bacteremia w/ meningitis; high survival rate; neurologic sequelae |
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Term
identifying features of streptococcus agalactiae |
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Definition
large buttery, beta-hemolytic colonies on blood agar
gram+, catalase-, bacitracin-resistant, CAMP test+
sodium hippurate+ (does hydrolyze)
bile esculin- (does NOT hydrolyze) |
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Term
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Definition
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Term
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Definition
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Term
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Definition
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Term
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Definition
streptococcus pneumoniae is sensitive to optochin (ONLY strep that is NOT resistant) |
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Term
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Definition
streptococcus agalactiae is the ONLY streptococcus w/ positive CAMP test (note the enhanced zone of hemolysis)
CAMP factor is a phospholipase => synergistic hemolysis w/ beta-lysin from certain S. aureus |
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Term
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Definition
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Term
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Definition
streptococcus pneumoniae capnophilic, mucoid (capsule producing) colonies on blood agar
alpha-hemolysis |
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Term
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Definition
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Term
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Definition
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Term
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Definition
pneumococcal pneumonia presenting w/ lobar consolidation |
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Term
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Definition
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Term
characteristics of viridans streptococci |
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Definition
gram+, catalase-, produce green pigment on blood agar, optochin resistant
*streptococcus pneumoniae is the ONLY optochin sensitive viridans streptococcus
most prevalent: oral cavity
=> life-threatening diseases: subacute endocarditis, meningitis, pneumonia |
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Term
growth requirements of streptococcus pneumoniae |
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Definition
fastidious and facultative (requires blood or serum)
enhanced w/ CO2 |
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Term
identification of streptococcus pneumoniae |
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Definition
alpha hemolysis on blood agar
bile salt susceptible |
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Term
how are most streptococcus pneumoniae infections caused? |
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Definition
endogenous (URT --> middle ear, sinuses, meninges, lungs, & blood)
infections from new strains (resp droplets/fomites) are rare |
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Term
six virulence factors of streptococcus pneumoniae |
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Definition
1. PspA (protect from host's complements)
2. hyaluronate lyase (surf protein acts on ECM; incr tissue perm, essential for virulence in pneumon, bacteremia, & meningitis)
3. neuaminidase (cleaves sialic acid from cell surf glycans; change glycosylation & expose host surf (by incr receptors)
4. capsule *primary VF-those w/o are harmless (inhib phago/complement activation)
5. proteases (degrade SIgA => enhance oral/intestinal mucosal infections)
6. pneumolysin (Ply) those w/o are less harmful (binds cholesterol of ciliated bronchial epithelia/phagocytes => pores => edema; hemorrhage; bacterial growth; penetration via epithel --> interstitium/blood |
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Term
most common cause of otitis media |
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Definition
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Term
most common cause of community pneumonia |
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Definition
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Term
pneumonia: presentation & cause |
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Definition
streptococcus pneumonia don't produce sig proteases
presentation: lobar consolidation (seldom destroy parenchyma); often preceded by viral illness; acute onset of high fever; rigors common; productive cough; pleural pain, dyspnea, tachypnea, tachycardia, sweats, malaise
sputum (rusty-from blood leaking out of capillaries) + for: PMN & lancet shaped diplococci |
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Term
most common cause of bacterial sinusitis |
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Definition
streptococcus pneumoniae
most sinusitis has viral origin, but acute sinusitis is usually bacterial
presentation: facial pain, headache, tenderness, fever, nasal discharge |
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Term
most common agent of bacterial meningitis of childhood and adulthood |
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Definition
streptococcus pneumoniae
predisposing conditions: pneumonia, otitis media
>4-20xs fatal/severe neurologic defects than meningitis by other bacteria |
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Term
enterococcus characteristics/identifying features |
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Definition
> 35 species, most common E. faecalis & faecium
gram+ coccus (pairs and short chains), more ovate than streptococci
facultative
high salt/bile/heat stress tolerant
optochin resistant
large white colonies on blood agar
usually non-hemolytic |
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Term
enterococcus epidemiology |
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Definition
enteric
present in human/animal feces/lg intestine/GUT
MOST infections: endogenous
nosocomial: due to cross infection |
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Term
enterococcus virulence factors |
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Definition
not well defined
antibiotic resistance |
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Term
diseases commonly caused by enterococcus |
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Definition
*UTI (less common than E. coli)
presentation: dysuria & pyuria
higher risk: w/ indwelling catheter OR use of broad-spectrum antibiotics
*Peritonitis
presentation: typically acutely ill; febrile; abdominal swelling/tenderness after abdominal trauma/surgery
~Endocarditis (occasionally)
associated w/: persistent bacteremia (acute or chronically) |
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Term
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Definition
Peptostreptococcus
part of normal flora, infections due to spread of these organisms to normally sterile places
colonizations: oral cavity, GIT, GUT, & skin
usually susceptible to penicillin; metronidazole; imipenem; & chloramphenicol
dx: presence of anaerobic coccus assoc w/ infection |
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