Streptococcus 2

• What type of pathogens are Streptococcus II?

  Gram-positive pathogens
• Why are enterococci named so?

  Because all enterococci are spherical and live in the intestinal tracts of animals
• Who classified enterococci with group D streptococci?

  Lancefield
• What conditions do enterococci grow in that inhibit Streptococcus growth?

  They grow at temperatures up to 45°C, at pH as high as 9.6, and in 6.5% NaCl or 40% bile salt broths
• What are the two significant pathogenic species of Enterococcus in humans?

  1. faecalis and E. faecium
• Where are E. faecalis and E. faecium found in the human body?

  In the human colon
• How can E. faecalis and E. faecium cause serious disease?

  If they are introduced into other parts of the body via poor personal hygiene or intestinal laceration
• What types of infections do Enterococci cause?

  Healthcare-associated infections, bacteremia, endocarditis, and wound infections
• What specimens are used for laboratory diagnosis of Enterococcus infections?

  • Urine
  • Blood
  • Sputum
  • Wound swab
• What agar can samples be cultured on for Enterococcus identification?

  • Blood agar
  • MacConkey agar
  • CLED agar
• What is the incubation temperature and duration for inoculated agar plates?

  Incubated aerobically at 10–45 ºC for 24 hours
• What is the colony morphology of Enterococci on blood agar?

  They are mainly non-haemolytic but some strains show alpha or beta-haemolysis
• How does E. faecalis appear on MacConkey agar?

  It ferments lactose, producing small dark-red magenta colonies
• What color do colonies of Enterococci appear on CLED agar?

  Small yellow colonies
• What is the Gram staining result for Enterococcus species?

  They are Gram-positive cocci, occurring in pairs or short chains
• What is the principle of the Esculin Hydrolysis Test?

  • Hydrolysis of esculin into glucose and esculetin by an enzyme called esculinase
  • Esculetin reacts with ferric citrate to form a dark brown or black color
• What is the procedure for the Esculin Hydrolysis Test?

  Inoculate bile esculin medium with colonies and incubate at 35-37°C for 24 hours
• What does a reduction of litmus milk indicate in the Litmus Milk Test?

  A change in color of the medium from mauve to white or pale yellow
• What is the procedure for the Litmus Milk Test?

  • Inoculate 0.5 ml of sterile litmus milk medium with the test organism
  • Incubate at 35–37°C for up to 4 hours, examining at half-hour intervals
• What does a white or pale yellow color in the Litmus Milk Test suggest?

  It suggests the presence of Enterococcus
• What are the general characteristics of the Viridans Group?

  They are alpha-hemolytic streptococci that lack group-specific carbohydrates
• Where do Viridans streptococci normally inhabit?

  In the mouth, pharynx, GI tract, genital tract, and urinary tract of humans
• Name some pathogenic species of the Viridans Group.

  1. mitis, S. mutans, and S. sanguis
• How do Viridans streptococci contribute to dental caries?

  They produce dextran from glucose, allowing them to stick to dental surfaces and form dental plaque
• What happens if Viridans streptococci enter the bloodstream?

  They can cause meningitis and endocarditis
• What is another name for Streptococcus pneumoniae?

  Pneumococcus
• What is the Gram staining result for Streptococcus pneumoniae?


  It is a Gram-positive coccus that forms short chains or pairs
• What is a unique feature of Streptococcus pneumoniae regarding Lancefield antigens?

  It lacks Lancefield antigens but incorporates a species-specific teichoic acid into its cell wall
• What are the virulence factors of Streptococcus pneumoniae?

  Polysaccharide capsule, phosphorylcholine, protein adhesin, pneumolysin, and IgA protease
• What disease does S. pneumoniae cause in about 85% of pneumonia cases?

  Pneumococcal pneumonia
• How does pneumococcal pneumonia occur?

  When pneumococci are inhaled from the pharynx into lungs damaged by other conditions
• What are the symptoms of pneumococcal pneumonia?

  Fever, severe shaking chills, productive cough, slightly bloody sputum, and chest pain
• What conditions can lead to pneumococcal pneumonia?

  Previous viral disease, alcoholism, heart failure, or diabetes mellitus
• What can S. pneumoniae cause following viral infections of the upper respiratory tract?

  Sinusitis and otitis media
• How can S. pneumoniae enter the bloodstream?

  Through lacerations, head & neck surgery, or from the lungs during pneumonia
• What specimens are used for pneumococcal lab diagnosis?

  • Sputum
  • Exudate
  • Blood
  • Cerebrospinal fluid
• What does a Gram stain of sputum and cerebrospinal fluid show for pneumococcal infections?

  Gram-positive diplococci
• What is the colony morphology of S. pneumoniae on blood agar?

  • Round, mucoid, alpha-haemolytic colonies
  • Initially raised, later flattened with raised edges
• What is the Gram staining result for S. pneumoniae?

  It is a Gram-positive elongated (lanceolate) diplococcus
• What is the serology test for pneumococcal lab diagnosis?

  • Antigen detection of pneumococcal C polysaccharide in CSF
  • Commercially prepared immunoassay