Gram positive bacteria Flashcards
What are characteristics of of all STAPHYLOcocci
Gram?
Catalase?
Structure?
- Gram-positive
- Catalase: positive
- Structure: grape-like
- Non motile
- Facultative anaerobes
- Salt-tolerant
Which is the most virulent staphylococci?
Staph. Aureus
Staph. Aureus
Found in:
Coagulase?
Found in: normal flora of nose, nasopharynx, perineal skin
Coaglulase: positive
What 3 features of pathogenicity does Staph. aureus result from
- Production of enzymes
- Structures/enzymes that enable to escape phagocytosis
- Production of toxins
How does staph aureus escape phagocytosis (3)
- Protein A:
- provides high affinity for Fe receptor of IgG molecules –> decreases clearance of the bacteria from site of infection - Coagulase:
- fibrin coat protects cells - Bacterial capsule
- facilities attachment to surfaces –> inhibits phagocytosis
Which Staph. Aureus enzymes increase virulence? (4)
- Coagulase
- Hyaluronidase (spreading factor)
- Staphylokinase
- Fibrinolysis: forms plasmin to digest fibrin clots
- allows you to bleed quicker - Beta-lactamase
- provides resistance to B-lactam antibiotics (penicilinns, cephalosporins)
What are examples of Staph. aureus exotoxins (4)
- Hemolysins
- Exfoliative toxins:
- cause staphylococcal scaled skin syndrome (SSSS); desquamtion= skin layer cells comes off in scales or flakes - Toxic-shock syndrome toxin
- cause fever, desquamation/hypotension leading to shock and death - Enterotoxins: important causes of food poisoning
- S. aureus grows in carbohydrate and proteins foods
Staph Epidermidis
Location?
Catalase?
Coagulase?
Location?
- Normal flora of skin and mucosa
Catalase?
- Positive
Coagulase?
- Negative
Which Staph is an opportunistic pathogen?
Staph. epidermidis
What are the virulence factors of Staph. Epidermidis (2)
Exopolysaccharide slime: adherence to medical devices (catheters etc..)
Exotoxins
Staph saprophyticus
Location
Catalase
Coagulase
Virulence factors
Location
- normal flora of: skin, mucous membranes, genitourinary tracts
Catalase
- positive
Coagulase
- negative
Virulence factors
- None
Which staph is a common cause of UTI
Staph saprophyticus
What is common of all streptococci
Gram?
Structure?
Catalase?
Gram positive
Structure: pairs or chains
Catalase: negative
Mostly facultative anaerobes
How do we classify streptococci (5)
- Colony morphology/hemolytic reactions
- Presence of lancefield antitgens: to divide Beta-hemolytic streptococci
- Biochemical reactions/resistance to physical + chemical factors
- Ecologic features (niche)
- Molecular genetics
Strept. Pyogens
Group
Formation
Location
Group: A
Formation: pairs or chains
Location: not part of normal flora
Virulence of Strept. pyogens (6)
- Capsule
- M protein: anti-phagocytic
- Pyrogenic exotoxins/erthrogenei
- toxic shock syndrome, scarlet fever - Streptokinase (fibrinolysis)
- digests blood clots –> allows bacteria to escape - Hemolysins: lyse erythrocyte membranes
- Hyalurodinase (spreading factor)
What are examples of infections with Strept. Pyogens (6)
- Acute paharyngitis: Strep throat
- Imeptigo: common in 2-5 yrs
- Cellulitis: skin swelling
- Necrotizing fasciitis: “flesh eating bacteria” destroys tissue in skin
- Bacteremia: infection in organs
- Post-streptococcal disease: auto-immune disorders after this infection
Strept agalactiae
Group
Location
Virulence factors
Group: B
Location: vaginal flora
Virulence factors:
- capsule
What are examples of infections for strep. agalactiae infections
Most common in neonates
Adults:
- post-partum (birth) infections
- immunocomprimised individuals
Enterococci
Group
Location
Virulence factors
Group: D
Location: GI tract, female genitourinary tract
Virulence factors:
- Adhesions
- Cytolysins
resistant to many antimicrobial agents
- first bacteria to develop vancomycin resistance
What infections are caused my enterocci
UTI
- Intra-abdominal infections
Strept Pneumococci
Group
Formation
Location
Group: alpha-hemolytic
Formation: Pairs or chains
Location: Upper respiratory
Strept. Pnemoniae infections caused?
bacteremia
meningitis
bacterial pneumonia
acute otitis media in children
What are the virulence factors of strep. pneumoniae?
- Polysaccharide capsule
- IgA protease
- Pneumolysin: intracellular killing
