Streptococcus – MD Nexus

Microbiology

Streptococci are Gram-Positive Cocci

Most Streptococci are Facultative Anaerobes, and Some are Obligate (Strict) Anaerobes
Unlike Staphylococcus, All Streptococci Lack the Enzyme Catalase

Medically-Relevant Members of Streptococcus Genus

Streptococcus Pyogenes (Group A) (see Streptococcus Pyogenes)

Characteristics
- β-Hemolytic (Wide Zone of Complete Hemolysis (2-4 mm Wide)
- Facultative Anaerobe (Can Use Oxygen in Aerobic Respiration, But Can Also Survive without Oxygen Via Fermentation or Anaerobic Respiration)
- Optimal Temperature for Growth is 37°C

Streptococcus Agalactiae (Group B) (see Streptococcus Agalactiae)

Characteristics
- β-Hemolytic (Wide Zone of Complete Hemolysis (2-4 mm Wide)

Streptococcus Dysgalactiae Subspecies Equisimilis (Group C/G) (see Streptococcus-GroupC+GroupG)

Members
- Streptococcus Dysgalactiae Subspecies Equisimilis: large colony, beta-hemolytic human isolates which express Lancefield C or G antigens
- Streptococcus Dysgalactiae Subspecies Dysgalactiae: large colony, variably hemolytic animal isolates which express Lancefield C or G antigens
Characteristics
- XXXXXXXXX

Streptococcus Pneumoniae (see Streptococcus Pneumoniae)

Characteristics
- Pneumococci are Lancet-Shaped, Catalase-Negative, Capsule-Forming Cocci or Diplococci
- α-Hemolytic (Incomplete Hemolysis; 1-2 mm Wide)

Viridans Group Streptococci (see Viridans Group Streptococci)

Characteristics
- α-Hemolytic (Incomplete Hemolysis; 1-2 mm Wide)
- Includes Streptococcal Species Which are Neither β-hemolytic Nor are Tolerant to High-pH Growth Conditions
- They Can Not Tolerate Salt, and Did Not Grow at 10°C
- Most of Them are Normal Flora of the Upper Respiratory Tract of Humans
Members
- Streptococcus Anginosus Group (see Streptococcus Anginosus Group)
  - Streptococcus Anginosus
  - Streptococcus Constellatus
  - Streptococcus Intermedius
- Streptococcus Mitis Group (see Streptococcus Mitis Group)
  - Streptococcus Mitis
  - Streptococcus Gordonii
  - Streptococcus Oralis
  - Streptococcus Sanguis
  - Streptococcus Parasanguis
- Streptococcus Salivarius Group (see Streptococcus Salivarius Group)
  - Streptococcus Salivarius
  - Streptococcus Thermophilus
  - Streptococcus Vestibularis
- Strep Bovis Group (see Streptococcus Bovis Group)
  - Streptococcus Alactolyticus
  - Streptococcus Equinus
  - Streptococcus Gallolyticus (Formerly Streptococcus Bovis) (see Streptococcus Gallolyticus)
- Streptococcus Mutans Group (see Streptococcus Mutans Group)
  - Streptococcus Mutans
  - Streptococcus Rattus
  - Streptococcus Cricetus
  - Streptococcus Downei
  - Streptococcus Sobrinus
  - Streptococcus Macacae

Group F Streptococcus (see xxxx)

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Clinical Manifestations

Cardiovascular Manifestations

Infective Endocarditis (see xxxx)

Epidemiology
- XXXXX
Prevalence of Infective Endocarditis in Streptococcal Bloodstream Infections Is Dependent on Streptococcal Species. Circulation. 2020 Aug 25;142(8):720-730. doi: 10.1161/CIRCULATIONAHA.120.046723 [MEDLINE]
- Background: Streptococci frequently cause infective endocarditis (IE), yet the prevalence of IE in patients with bloodstream infections (BSIs) caused by different streptococcal species is unknown. We aimed to investigate the prevalence of IE at species level in patients with streptococcal BSIs
- Methods: We investigated all patients with streptococcal BSIs, from 2008 to 2017, in the Capital Region of Denmark. Data were crosslinked with Danish nationwide registries for identification of concomitant hospitalization with IE. In a multivariable logistic regression analysis, we investigated the risk of IE according to streptococcal species adjusted for age, sex, ≥3 positive blood culture bottles, native valve disease, prosthetic valve, previous IE, and cardiac device
- Results: Among 6506 cases with streptococcal BSIs (mean age 68.1 years [SD 16.2], 52.8% men) the IE prevalence was 7.1% (95% CI, 6.5-7.8). The lowest IE prevalence was found with Streptococcus pneumoniae (S pneumoniae) 1.2% (0.8-1.6) and Spyogenes 1.9% (0.9-3.3). An intermediary IE prevalence was found with Sanginosus 4.8% (3.0-7.3), Ssalivarius 5.8% (2.9-10.1), and Sagalactiae 9.1% (6.6-12.1). The highest IE prevalence was found with Smitis/oralis 19.4% (15.6-23.5), Sgallolyticus (formerly Sbovis) 30.2% (24.3-36.7), Ssanguinis 34.6% (26.6-43.3), Sgordonii 44.2% (34.0-54.8), and Smutans 47.9% (33.3-62.8). In multivariable analysis using S pneumoniae as reference, all species except S pyogenes were associated with significantly higher IE risk, with the highest risk found with S gallolyticus odds ratio (OR) 31.0 (18.8-51.1), S mitis/oralis OR 31.6 (19.8-50.5), S sanguinis OR 59.1 (32.6-107), S gordonii OR 80.8 (43.9-149), and S mutans OR 81.3 (37.6-176)
- Conclusions: The prevalence of IE in streptococcal BSIs is species dependent with S mutans, S gordonii, S sanguinis, S gallolyticus, and S mitis/oralis having the highest IE prevalence and the highest associated IE risk after adjusting for IE risk factors

References

Clinical Manifestations

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