Streptococci Flashcards
What are some general characteristics of streptococci ?
- gram + cocci (single, pairs, and chains)
- occurs in pairs and chains microscopically
- facultative anaerobes
- catalase (-)
- normal flora of the skin, mucous membrane, mouth, pharynx and urogenital
- hemolytic reactions
What is alpha hemolysis ?
partial lysis of RBC
- greenish discoloration to agar
What is beta hemolysis ?
complete lysis of RBC
- clearing of the agar around colonies
What is gamma hemolysis ?
no lysis of RBC
- no change of the agar around the colonies
Which hemolysis have the biggest impact on human health ?
alpha & beta
What infections are caused by streptococcus pyogenes ?
- strep throat
- tonsilitis
- erysipelas (contagious skin infection)
- impetigo (around nose, mouth, extremities)
- septicemia (systemic infection in the blood)
- pneumonia (respiratory)
- necrotizing fasciitis (flesh eating bacteria)
What is the function of streptolysin O in strep. pyogenes ?
- SLO exotoxin (rare)
- oxygen labile (will destroy/inhibit O2)
- only will perform beta hemolysis in anaerobic conditions
What is the function of streptolysin S in strep. pyogenes ?
- SLS exotoxin (common)
- oxygen stable
- hemolysis occurs under aerobic or anaerobic conditions
What is the function of erythrogenic toxin in strep. pyogenes ?
rash of scarlet fever
- toxin is absorbed and carried by the blood
What is the function of streptokinase/fibrinolysin in strep. pyogenes ?
- breakdown of fibers
- helps organism to spread
What is the function of hyaluronidase in strep. pyogenes ?
breaks down hyaluronic acid which binds connective fibers
What is the function of exotoxins in strep. pyogenes ?
fever and shock
What is the strep bacteria that is a Group A streptococci ?
streptococcus pyogenes
- sensitive to bacitracin (won’t grow in it’s presence)
What is the significance of having post-streptococcal diseases ?
happen after having Strep A infection
- not the infection that causes the disease but it’s the antigen (antigen-antibody reaction)
- your immune system recognizes the antigen as Strep A (when it isn’t) and your body will start to attack the heart valves and glomerulus of the kidney because the antigen of group A resembles this
What are the 2 post-streptococcal diseases ?
- Rheumatic fever: 10-14 days after (joint issues, myocarditis) caused by the system attacking the heart valves
- Glomerulonephritis: caused by attack to glomerulus of the kidney (headache, increased BP, low grade fever, weight gain, facial/periorbital edema)
What is impetigo ?
one of the most common skin infections among kids
- staph aureus or strep pyogenes
- blisters or sores on face, neck, hands, and diaper area
What are some symptoms of scarlet fever ?
rash & tongue may have whitish coating and appear swollen
- reverse strawberry appearance
What are some morphology of Strep. pyogenes ?
- beta hemolytic
- Lancefield group A
- bacitracin sensitive (can’t grow in presence of antibiotic bacitracin)
What are some characteristics of Strep. agalactiae (group B strep) (GBS) ?
- normal flora especially in urogenital and oral cavity
- generally harmless and most don’t even know they have it
- about 25% found in pregnant women
- bacitracin& SXT resistant
What happens if a pregnant person has GBS (group B strep) ?
if tested (+) then they are given IV antibiotics during labor to kill the bacteria
- can’t be done before because it grows back quickly
What infections are caused by group B strep ?
- meningitis and/or septicemia in newborns
- infections in post-partum women
- female urogenital tract
- wound and skin infections
What is some morphology of group B strep ?
- beta hemolytic
- Lancefield Group B
- CAMP test (+)
What is the group B streptococci ?
streptococci agalactiae
What is Lancefield grouping ?
method of grouping catalase-negative & coagulase-negative bacteria based on carb composition of bacterial antigens found on their cell walls
