Streptococcus Flashcards

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1
Q

Streptococcus pneumoniae

A
  • Gram-positive, lancet-shaped cocci (elongated cocci)
  • Generally found in pairs (diplococci)
  • Non-motile, non-sporulated
  • Fermentor and aerotolerant with lactic acid as the major product
  • Hydrolyses inulin (diferential characteristic)
  • Does not produce catalase
  • > 96 serotypes based on a polysaccharidic capsule
  • Its teichoic acid in the “C polysaccharide”
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2
Q

Streptococcus pneumoniae growth

A
  • Fastidious microorganism, some strains require a 5% CO2 atmosphere
  • Grown usually on blood agar
  • Some strains show enhanced growth under anaerobiosis
  • Growth requires a source of catalase (such as blood) to neutralize the H2O2 produced
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3
Q

Streptococcus pneumoniae differentiation

A
  • Hard to differentiate from other viridans streptococci
  • Solubility in bile salts (deoxycholate)
  • Activation of the autolysins (LytA)
  • Optochin susceptibility
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4
Q

Streptococcus pneumoniae - virulence factors

A
Structural  components
- Capsule
- Teichoic acids
- Choline binding  proteins
- Pilus-like
Toxins / enzymes
- Pneumolysin
- Hyaluronidase
- C5a Peptidase
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5
Q

Streptococcus pneumoniae - infection

A
  • The sole ecological niche is the human nasopharynx
  • Transmission through aerosols
  • sinusitis, otitis conjuntivitis , pneumonia, bacteremia , meningitis
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6
Q

Streptococcus pneumoniae - Diagnostic

A
  • Search for antigen in urine

- Not recommended in pediatric patients!

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7
Q

Streptococcus pneumoniae - Meningitis

A

Diagnose:

  • blood
  • Cerebrospinal fluid (CSF)
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8
Q

Streptococcus pneumoniae - Pneumonia

A

Diagnose:

  • blood
  • sputum
  • broncoscopy
  • antigen in urine
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9
Q

Streptococcus pneumoniae - Antimicrobial resistance

A
  • Resistance to penicillin
  • Resistance to third generation cephalosporins
  • Macrolide resistance (mef e erm)
  • Resistance to new fluoroquinolones
  • Absence of in vitro resistance to vancomycin, linezolid, tigecycline
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10
Q

Streptococcus pneumoniae - Resistance to penicillin

A
- Target modification
(PBPs 1A; 1B; 2A; 2X e 2B)
- Gradual acquisition of foreign DNA
- Genes with a mosaic structure
- Transformation using DNA from other  oral streptococci
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11
Q

Streptococcus pneumoniae - Therapy respiratory infections

A
  • Penicillin (Amoxicillin)
  • Macrolides, Cephalosporins
  • New quinolones (levofloxacin, moxifloxacin) – In cases of high-level penicillin resistance BUT resistance
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12
Q

Streptococcus pneumoniae - Therapy Meningitis, bacteremia

A
  • Penicillin if susceptible
  • Third generation cephalosporins (cefotaxime or ceftriaxone)
  • Vancomycin
  • Association of cephalosporin + vancomycin in empiric therapy
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13
Q

Streptococcus mutans

A
  • Colonizes
    Adhesion to the tooth
    Adhesion to the gum
  • Biofilm formation
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14
Q

Streptococcus pyogenes

Lancefield group A

A
  • Colonizes the respiratory tract (15% - 20% children and young adults) and transiently the skin
  • Survives on dry surfaces
  • Respiratory spread (faringitis) or direct contact (skin lesions)
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15
Q

Streptococcus pyogenes - M Protein

A

(emm gene)

  • Adhesion
  • Complement escape
  • Molecular mimecry
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16
Q

Streptococcus pyogenes - mode of action

A
  • Superantigens
  • Pyrogenic toxins
  • Activation of T-cells without the need for an antigen (Ag)
17
Q

Streptococcus pyogenes - virulence factors

A
Structural  components
-Capsule
-Lipoteichoic acid
-M protein
-Fibronectin-binding proteins
Toxins / enzymes
- Pyrogenic toxins
- Streptolysin S
- Streptolysin O
- Streptokinase
- DNAses
- C5a Peptidase
18
Q

Streptococcus pyogenes - More frequent infections

A
  • Amigdalo-faringitis
  • Scarlet fever
  • Skin and soft tissue infections (impetigo, erysipelas, cellulitis)
  • Toxic-shock syndrome
  • Necrotizing fasciitis
  • Rheumatic fever
  • Glomerulonephritis
19
Q

Streptococcus pyogenes - Antimicrobial resistance

A
  • Penicillin – not described!
  • Macrolides
  • Resulting from target modification
  • Resulting from efflux
    Active efflux (mef genes). M phenotype - Resistance to macrolides (erythromycin, clarithromycin, azithromycin)
20
Q

Streptococcus pyogenes - Therapy

A
  • Penicillin
  • Macrolides (erythromycin, clarithromycin, azithromycin)
    (In Portugal ~ 5% resistance and going down)
  • Association with clindamycin (but erm), dicloxacillin or vancomycin (severe infections)
  • Draining / surgical debridement in severe skin and soft tissue infections (SSTI)
21
Q

Streptococcus agalactiae

Lancefield group B

A
  • Colonizes the oropharynx, GI tract and vagina (10% to 30% of pregnant women)
  • Transmission to the newborn during pregnancy or delivery
  • Increased risk of infection:
    Premature membrane rupture
    Prolonged labor
    Prematurity
    Mother colonized or infected with S. agalactiae
22
Q

Streptococcus agalactiae - Virulence factors

A
Resistance to opsonization and phagocytosis:
- Capsule
- C Protein: alfa and beta C5a peptidase
Invasion:
- Hyaluronidase  
- C5a peptidase
Adherence:
- C5a peptidase
23
Q

Streptococcus agalactiae - More frequent infections

A
Neonatal period
- Early and late neonatal infections  (meningitis, sepsis, pneumonia)  
Pregnant woman
- Infection following childbirth (endometritis)
- Urinary tract infection (UTI)
Non-pregnant adult
- UTI
- Bacteremia
- SSTI
- Other pyogenic infections
24
Q

Streptococcus agalactiae - Serotypes

A

Capsular serotypes:
Ia, Ib, II, III, IV, V, VI, VII, VIII, IX
- III and V: USA, Canada, Zimbabwe, France, Turkey, UK, Czech republic, Argentina, Portugal
- IV: United Arab Emirates
- VI e VIII: Japan

25
Q

Streptococcus agalactiae - therapy

A
  • Penicillin
  • Penicillin (or cephalosporin or vancomycin if penicillin alergic) + Aminoglycoside in serious infections
  • Ampicillin or Nitrofurantoin in UTI
26
Q

Streptococcus agalactiae - Profilaxis

A
  • Vaginal/rectal colonization screen (35 - 37 wks gestation)
  • In colonized pregnant women and when risk factors are present (penicillin, amoxicillin, clindamycin, cefazoline, vancomycin)
  • Conjugate vaccine in development
27
Q

Enterococcus

old Group D streptococci

A
  • Enterococcus faecium (5-10% infecções)
  • Enterococcus faecalis (90% infecções)
  • Microbiota of the GI tract
  • Not very virulent
  • Very resistant
28
Q

Enterococcus - Infections

A
  • Urinary tract
  • Associated with surgical wounds
  • Of the skin and soft tissues Bacteremia (Catheters, Endocarditis)
29
Q

Enterococcus - Resistence

A
  • Intrinsically resistant to low concentrations of penicillin
  • Intrincically resistant to cephalosporins, clindamicin, quinolones, co-trimoxazol, monobactams
  • Acquired resistance to aminoglycosides, macrolides, tetracyclines, chloramphenicol,
  • Glycopeptide and linezolid
  • Resistance to ampicillin
    Change in the target site (PBPs) Production of beta-lactamases – very rare!
  • Resistance to aminoglycosides Modifications – enzymes that alter the aminoglycosides
  • Point mutations – raro
30
Q

Enterococcus - treatment

A
  • Antimicrobial active against the cell wall. Beta-lactam: Ampicillin, Amoxicillin, Glycopeptide: Vancomycin, Teicoplanin
  • Aminoglycoside,Gentamicin, Streptomycin
  • Synergism
  • Multiresistance
31
Q

Enterococcus - growth

A
  • Grows in MacConkey!
  • Grows in the presence of high salt concentrations
  • Grows in a wide range of temperatures (10-45ºC)
  • Grows in the presence of bile salts and hydrolyses esculin