- Colonizes Adhesion to the tooth Adhesion to the gum - Biofilm formation

Streptococcus Flashcards by arya rety

Streptococcus pneumoniae

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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Streptococcus pneumoniae growth

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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Streptococcus pneumoniae differentiation

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

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Streptococcus pneumoniae - virulence factors

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

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Streptococcus pneumoniae - infection

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

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Streptococcus pneumoniae - Diagnostic

Search for antigen in urine

- Not recommended in pediatric patients!

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Streptococcus pneumoniae - Meningitis

Diagnose:

blood
Cerebrospinal fluid (CSF)

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Streptococcus pneumoniae - Pneumonia

Diagnose:

blood
sputum
broncoscopy
antigen in urine

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Streptococcus pneumoniae - Antimicrobial resistance

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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Streptococcus pneumoniae - Resistance to penicillin

- 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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Streptococcus pneumoniae - Therapy respiratory infections

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

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Streptococcus pneumoniae - Therapy Meningitis, bacteremia

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

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Streptococcus mutans

Colonizes
Adhesion to the tooth
Adhesion to the gum
Biofilm formation

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Streptococcus pyogenes

Lancefield group 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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Streptococcus pyogenes - M Protein

(emm gene)

Adhesion
Complement escape
Molecular mimecry

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Streptococcus pyogenes - mode of action

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

Streptococcus pyogenes - virulence factors

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

Streptococcus pyogenes - More frequent infections

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

Streptococcus pyogenes - Antimicrobial resistance

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

Streptococcus pyogenes - Therapy

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)

Streptococcus agalactiae

Lancefield group B

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

Streptococcus agalactiae - Virulence factors

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

Streptococcus agalactiae - More frequent infections

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

Streptococcus agalactiae - Serotypes

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

Streptococcus agalactiae - therapy

- Penicillin - Penicillin (or cephalosporin or vancomycin if penicillin alergic) + Aminoglycoside in serious infections - Ampicillin or Nitrofurantoin in UTI

Streptococcus agalactiae - Profilaxis

- 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

Enterococcus | old Group D streptococci

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

Enterococcus - Infections

- Urinary tract - Associated with surgical wounds - Of the skin and soft tissues Bacteremia (Catheters, Endocarditis)

Enterococcus - Resistence

- 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

Enterococcus - treatment

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

Enterococcus - growth

- 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