Streptococcus Flashcards
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”
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
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
4
Q
Streptococcus pneumoniae - virulence factors
A
Structural components - Capsule - Teichoic acids - Choline binding proteins - Pilus-like Toxins / enzymes - Pneumolysin - Hyaluronidase - C5a Peptidase
5
Q
Streptococcus pneumoniae - infection
A
- The sole ecological niche is the human nasopharynx
- Transmission through aerosols
- sinusitis, otitis conjuntivitis , pneumonia, bacteremia , meningitis
6
Q
Streptococcus pneumoniae - Diagnostic
A
- Search for antigen in urine
- Not recommended in pediatric patients!
7
Q
Streptococcus pneumoniae - Meningitis
A
Diagnose:
- blood
- Cerebrospinal fluid (CSF)
8
Q
Streptococcus pneumoniae - Pneumonia
A
Diagnose:
- blood
- sputum
- broncoscopy
- antigen in urine
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
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
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
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
13
Q
Streptococcus mutans
A
- Colonizes
Adhesion to the tooth
Adhesion to the gum - Biofilm formation
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)
15
Q
Streptococcus pyogenes - M Protein
A
(emm gene)
- Adhesion
- Complement escape
- Molecular mimecry