Gram + Bacteria Flashcards
What are the cocci gram positive bacteria
staphylococcus
streptococcus
enterococcus
Bacilli Gram positive bacteria
Non-spore forming
- corynebacterium
- listeria
- lactobacilli
Spore Forming
- bacillus
- Clostridium
Coagulase Test
mix some bacteria with V of plasma
-if enzyme straphylocoagulase present — blood will clot within 24 hours
- helps differentiate staph. aureus from others (only one that is coagulase +)
What is the catalase test do
does the organism breakdown hydrogen peroxide ?
- +: bubbles
Oxidase test
does the organism produce cytochrome C oxidase ?
- if oxidase +: changes colourless reagent purple
General traits of staphylococcus
Catalase +
Facultative anaerobe
S. Aureus
Most virulent species
Hemolysis: beta/complete lysis/clearing
Normally found in nose, perineal area and skin
When do you have a staph aureus infection
when the bacteria breaches the body’s barriers
- results from their structures/enzymes used to evade phagocytosis/ production f enzymes and toxins
What mechanisms does S. aureus use to evade phagocytosis
1) Neutrophil extravasation + chemotaxis: secretion of SSLs and inhibit host surface receptors
2) Inhibition of complement and phagocytosis: secrete inhibitory factors that impact opsonization
3) Enzymes that prevent neutrophil killing: inhibit granule forming, make antioxidants that inactivate ROS in phagosome
4) production of pore forming toxins
What enzymes does S. aureus have?
Coagulase
Hyaluronidase
Staphylokinase
Beta-lactamase
What does staphylokinase do
causes fibrinolysis; activates plasminogen to plasmid; digests fibrin clots
What does beta-lactamase do
provides resistance to B-lactam antibiotics
Toxins of S. Aureus
Hemolysins
Exfoliative toxins: cause generalized exfoliation seen in staphylococci scalded skin syndrome (SSSS) by dissolved matrix of epidermis
Toxic Shock Syndrome toxin (TSST-1): causes fever, hypotension etc
Enterotoxins: causes of food poisoning, made when S. aureus grows in carbs/protein rich foods
What infections does S. Aureus cause
Food poisoning
TSS
Soft Tissue Infections
Impetigo
SSS
Endocarditis
Osteomyelitis: infection of bone
Staphylococcus epidermidis traits
Gamma hemolytic
Catalase Positive
- normally found on skin and mucosa
- opportunistic pathogen: only causes infection if immune compromised
Staph. saprophyticus
Gamma hemolysis
normally found on skin, genitourinary tract
Infections: UTI
T or F: Streptococcus are normally found in large clumps
F: pairs or chains of cocci
What is the classification of streptococci based off
1) colony morphology + hemolytic reactions
2) Beta hemolytic: are further divides based on cell wall group antigens
3) Biochemical reactions + R to physical or chemical factors
Streptococci Traits
Catalase -
Facultative Anaerobes
don’t form spores
T or F: Strep. pyogenes are group B
F - group A
Streptococcus Pyogenes Traits
Beta hemolytic
Catalase -
*not normal flora *
T or F: Strep. pyogenes has hemolysins that can lyse RBCs and other cells
T - has streptolysins that can lyse both
—- also has streptokinase
What infections does S. pyogenes cause
strep throat
impetigo
cellulitis: red swelling of skin
Necrotizing fasciitis
Bacteremia
Traits of Strep. Agalactiae
Beta hemolytic
Catalase -
normally found in vag and GI tract
Infections: normally causes infections in neonates (postpartum infections, pneumonia, bacteremia etc)
