streptococcus

• Genus


  • Abiotrophia
  • Leuconostoc
  • Lactococcus
  • Pediococcus
  • Aerococcus
  • Gamella
  • Streptococcus
  • Enterococcus
• Abiotrophia


  • Normal flora of oral cavity and upper respiratory tract
  • Need of pyridoxal (vitamin 6) to grow
• Leuconostoc


  • Found in plants and dairy products
  • Resistant to Vancomycin antibiotic
• Lactococcus


  • Found in food or vegetables
• Pediococcus


  • Discovered via pedia patients (children)
  • Found in food or vegetables
  • Resistant to Vancomycin
• Aerococcus


  • Found in the environment and occasionally on the skin
  • Causes UTI (Aerococcus urinae)
• Gemella


  • Normal flora of oral cavity and upper respiratory tract
• Enterococcus


  • Normal flora of digestive system, oropharynx, female genital tract and skin
  • Virulence factors: translocation in intestinal mucosa, hemolysin, lipotechoic acid, gelatinase, superoxide production, peptide inhibitors
  • Causes rare UTI, bacteremia, endocarditis and intraabdominal infection, wound infection and soft tissue infection on immunocompromised patients
  • Resistant to cephalosporins, aminoglycosides and vancomycin
  • PYR (+)
  • Produces brown halo around colony in Bile Esculin Agar
• Streptococci


  • Gram (+), cocci 0.5 – 1.2 um
  • Catalase (-)
  • Oxidase (-)
  • No gas production
  • Non-motile
  • Facultative anaerobe (carbohydrates) except peptostreptococci which are obligate anaerobe
  • Has exotoxin (Gram positive) that lyses RBC
  • Some are capnophilic (high concentrations of carbon dioxide)
• 4 – 5 Drops of H2O2 needed for catalase test (standard)
• 30% H2O2 for Neisseria, 15% H2O2 for Anaerobes, 3% H2O2 for other bacteria (purchase or dilute 30% 1:10 in deionized water prior to use)
• Streptococcus pneumoniae is an example of gas production
• Classification of Streptococci (Academic/Bergey's)

  • Pyogenic group
  • Viridans group
  • Lactic group
  • Enterococcus group
• Classification of Streptococci (Smith and Brown)

  • Alpha-haemolytic streptococci
  • Beta-haemolytic streptococci
  • Gamma-haemolytic/Non-haemolytic streptococci
• Lancefield Classification

  Based on extraction of C carbohydrate for the streptococcal cell wall, devised by Rebecca Lancefield
• Growth temperature ranges

  • Pyogenic: 37°C

  Viridans: 37°C, 45°C

  Enterococcus: 10°C, 37°C, 45°C

  Lactic: 10°C, 37°C
• Streptococcus pyogenes (Group A Streptococcus)


  • Has M Protein which is essential for virulence, encoded by gene emm
  • M Protein helps resist phagocytosis and adhere to mucosal cells
  • Other virulence factors: Fibronectin (binding protein), Lipoteichoic Acid, Hyaluronic Acid Capsule, Hemolysins, toxins and enzymes (Streptolysin O, Streptolysin S, DNase, Streptokinase, Hyaluronidase, Erythogenic exotoxins, Exotoxin B)
  • Causes bacterial pharyngitis, pyodermal infections (impetigo, erysipelas, cellulitis, scarlet fever), necrotizing fasciitis
• Streptococcus pyogenes is the common cause of acute pharyngitis
• Diagnosis methods for acute pharyngitis

  • Culture
  • Direct antigen detection
  • Nucleic acid probe
  • Nucleic acid amplification test
• Acute pharyngitis can also be caused by Streptococcus group C and G
• S. pyogenes is the common cause of acute pharyngitis
• Impetigo (nonbullos impetigo)


  • Small vesicles to weeping lesions
  • Insect bites and abrasions
  • Seen in children
• Erysipelas


  • Rare infection of the skin and subcutaneous tissue
  • Seen in adults
• Cellulitis


  • Deeper invasion of organism
  • With redness (erythema) and edema (nagmamanas)
  • For diabetic patient, may lead to gangrene
• Scarlet Fever


  • Diffuse red rash on upper chest and spreads to trunk and extremities
  • Disappears on the 5th to 7th day followed by desquamation
  • Cause by SPEs
  • Dick's test and Schultz-Charlton test
• Necrotizing Fasciitis

  • Rapid progressing of inflammation and necrosis of the skin, subtaneous fats and fascia
  • "galloping gangrene" or "flesh-eating bacteria syndrome"
  • Life threatening that could lead to TSS
• S. pyogenes infection is prone to progression to deeper tissues (flesh-eating bacteria)
• Streptococcal Toxic Shock Syndrome


  • Entire system collapses leading to death
  • Similar to Staphylococcus TSS
  • GAS produces Erythrogenic exotoxins notably SpeA
• Rheumatic Fever


  • Antigen cross reactivity between antigens and heart tissue
  • Leads to chronic form which is rheumatic heart fever
  • Symptoms: fever, endocarditis, subcutaneous nodules, polyarthritis (more than 4 joints yung masakit)
  • Treatment: penicillin every 21 days
• Acute Glomerulonephritis


  • More common in children than adults
  • Disposition of immune complexes on the glomeruli
  • Symptoms: edema, hypertension, hematuria, and proteinuria
• Specimen Collection

  Transport media is not required as they are resistant to drying
• Gram stain is little value for microscopy
• Culture

  • Swab over posterior pharynx and each tonsillar area then culture either with oxygen or no oxygen
  • Beta hemolytic pattern with small, transparent and smooth with well-defined area
  • Bacitracin sensitive
  • Hydrolyses PYR Test with cherry red color
• Serological Testing

  Through ELISA with sensitivity of 60-90%
• Penicillin

  Drug of choice for rheumatic heart fever - prophylactic doses
• Erythromycin


  Drug of choice
• Group B Streptococci (Streptococcus agalactiae)

  • Has group-B specific antigen
  • Acid stable polysaccharide
• Virulence Factors of Group B Streptococci

  • Capsule
  • Sialic acid
  • Hemolysin
  • CAMP factor
  • Neuraminidase
  • DNase
  • Hyaluronidase
• Meningiditis in Newborns

  • Starts from 3 days after birth but usually within 24 hours
  • Caused by presence of GBS in the vagina of mothers
  • Recommendation: Check pregnant mothers at 35-37 weeks of gestation
• Common causes of meningitis by age group

  • Newborns: Streptococcus agalactiae
  • Children: Haemophilus influenzae
  • Teens to Young Adults: Neisseria meningitidis
  • Senior Citizen: Streptococcus pneumoniae