Bacteria Flashcards
What kind of bacteria is Staph aureus?
Gram + cocci in clusters Catalase + (Strep is Catalase (-)) Coagulase + (converts fibrinogen to fibrin; compared to other Staph) Beta hemolytic Ferments mannitol (turns agar yellow)
What is the main virulence factor of Staph aureus? What is it’s function?
Protein A; it is part of the cell wall and binds FC portion of antibody; inhibits phagocytosis and complement activation
What part of the body is normally colonized with Staph aureus?
Nares (opening of nose)
Inflammatory diseases caused by Staph aureus (5)
- Pneumonia - patchy infiltrate on X-ray; secondary post viral super infection most often
- Joint problems - septic arthritis
- Skin infections - cellulitis, boils, abscesses
- Acute bacterial endocarditis - IV drug user (Right sided heart infection - tricuspid) (rapid onset, acute)
- Osteomyelitis - Most common cause
Toxin mediated diseases caused by Staph aureus
- Scalded skin syndrome - mediated by exfoliative toxin
- Toxic shock syndrome - super antigen; from foreign package being left in too long
- Food poisoning - Rapid onset from preformed toxin (1-8 hours); vomiting; from meats and cream based foods (mayonnaise)
- MRSA - Alters PBP’s to get away from Methicillin; treatment is Vancomycin or Nafcillin
What should you use to treat MRSA?
Vancomycin
Nafcillin
What kind of bacteria is Staph epidermidis? (5)
Gram + cocci Catalase + Coagulase - Urease + Novobiocin sensitive (opposite of Staph saprophyticus)
What kind of bacteria is Staph saprophyticus? (5)
Gram + cocci Catalase + Urease + Coagulase - Novobiocin resistant (opposite of Staph epidermidis
What does Staph epidermidis classically infect?
- Artificial joints and catheters; covers everywhere
2. Endocarditis for artificial heart valves - most common cause of artificial valves
What do you treat Staph epidermidis endocarditis? Why?
Vancomycin; it is resistant to many ABx
Why is Staph epidermidis so good at infecting plastic/foreign surfaces?
Can produce adherent biofilms
What disease does Staph saprophyticus cause?
UTI in sexually active females - SECOND most common cause behind E. coli
What does Staph epidermidis contaminate?
Blood cultures; component of normal skin flora
What kind of bacteria is Strep pyogenes?
Gram positive cocci in chains/pairs (Group A)
Catalase -
Beta hemolytic
Bacitracin sensitive
What kind of bacteria is Strep agalactiae?
Gram positive cocci in chains (Group B)
Catalase -
Beta hemolytic
Bacitracin RESISTANT
Pyogenic diseases that Strep pyogenes causes (2)
- Pharyngitis - strep throat
- Impetigo - honey crusted
- Cellulitis
- Erysipelas - most common cause of
Toxigenic diseases that Strep pyogenes causes (2)
- Scarlet fever - strawberry tongue, pharyngitis, rash that spares face
- Toxic shock like syndrome - super antigen - SpeA, SpeC
- Necrotizing fasciitis - SpeB
Immunologic diseases that Strep pyogenes causes (2)
- Rheumatic fever
2. Post-Strep Glomerulonephritis
Impetigo more commonly precedes __________ than ________.
Impetigo more commonly precedes glomerulonephritis than pharyngitis.
How do you detect Strep pyogenes infection?
ASO titer
Treating S. pyogenes with Penicillin can prevent which complications?
Penicillin can prevent Acute Rheumatic Fever
It CANNOT prevent Acute Glomerulonephritis
Signs of Post-Strep Glomerulonephritis
Type III hypersensitivity
Coca cola colored urine and facial puffiness 2 weeks after Strep infection
What is responsible for Acute Rheumatic Fever after Strep infection?
M protein - it interferes with opsonization and is similar to antigen on cardiac myocytes (Strong humoral response created against it)
What does Streptokinase do? What bacteria has it?
Strep pyogenes; it converts plasminogen to plasmin
What kind of capsule does Strep pyogenes have?
Hyaluronic acid capsule (not immunogenic)
Defining characteristics of Strep agalctiae
Gram + cocci Group B strep Beta hemolytic Bacitracin RESISTANT Polysaccharide capsule CAMP test positive
What is the significance of CAMP factor?
What bacteria produces CAMP factor?
Enlarges the area of hemolysis formed by S. aureus
Strep agalactiae
Diseases in Strep agalactiae
Neonatal meningitis + sepsis + pneumonia
Why do you need to screen pregnant women for Strep agalactiae? When do you screen them? How do you treat if infected?
It colonizes vagina and there is no vaccine so babies passing through vaginal canal can become infected
Screen at 35-37 weeks; treat with intrapartum penicillin prophylaxis
1 cause of meningitis in neonates
Strep agalactiae (other causes are Listeria and K1 E. coli)
Alpha hemolytic strep
Strep pneumoniae
Strep viridans
Strep pneumo characteristics
Polysaccharide capsule Optochin sensitive Lancet shaped diplococci Bile soluble IgA protease
Strep pneumo is the most common cause of:
- Meningitis
- Otitis media
- Pneumonia
- Sinusitis
What is treatment of choice for outpatient CAP?
Azithromycin
What is pneumococcus associated with in sickle cell disease and splenectomy patients?
Rusty sputum and sepsis
What accounts for Strep pneumo resistance?
Polysaccharide capsule
Treatment for Strep pneumo
Macrolide (Erythromycin)
3rd gen. Cephalosporin (Ceftriaxone)
Vaccines for Strep pneumo
Adults - 23 talent polysaccharide; T cell independent (only IgM)
Children - 7 talent conjugation; more robust T cell response (IgG)
Strep viridans characteristics
No capsule
Optochin resistant
Bile resistant
What diseases do viridans Strep cause?
Dental caries (mutans) subacute bacterial endocarditis (sanguinis)
Makes dextrans, which bind to fibrin-platelet aggregates on damaged heart valves
Viridans strep
Group D Strep
Enterococci (E. faecalis and E. faecium)
What are enterococci found?
Normal colonic flora
What diseases do enterococci cause?
UTI
Biliary tract infections
Subacute endocarditis (following GI/GU procedures)
Which enterococci species is more common?
E. faecalis
Which enterococci species is more dangerous?
E. faecium (bile resistant)
Why are nosocomial enterococci infections dangerous?
They are resistant to everything
Vancomycin-resistant enterococci
How do you treat Vancomycin-resistant enterococci?
Linezolid
Tigecycline
Which bacteria is associated with colon cancer?
Strep Bovis (group D strep) -Can also cause bacteremia and subacute endocarditis
What kind of toxin does Corynebacterium diphtheriae cause diphtheria with?
Via exotoxin encoded by B-prophage –> inhibits protein synthesis via ADP-ribosylation of EF-2
Pseudomembranous pharyngitis (gray-white membrane) with lymphadenoapthy, myocarditis and arrhythmias
Corynebacterium diptheriae
How is Corynebacterium transmitted?
By respiratory droplets
Gram positive rods with metachromatic granules and + Elek test for toxin
Corynebacterium diptheriae
ABCDEFG of Corynebacterium
ADP ribosylation B-prophage Corynebacterium Diphtheriae Elongation Factor 2 Granules
Black colonies on cystine-tellurite agar (plated on Loeffler’s medium)
Corynebacterium diphtheriae
Bacterial spores; cause which disease?
a. Bacillus anthracis
b. Bacillus cereus
c. Clostridium botulinum
d. Clostridium difficile
e. Clostidium perfringens
f. Clostridium tetani
g. Coxiella burnetii
a. Anthrax
b. Food poisoning
c. Botulism
d. Antibiotic-associated colitis
e. Gas gangrene
f. Tetanus
g. Q fever
How does Bordetella pertussis toxin work?
It ADP ribosylates Gi (inactivates it) and causes over activation of adenylate cyclase that elevates cAMP production and increases secretions and mucus production –> makes it more difficult to clear bacteria
Black eschar
Bacillus anthracis (cutaneous)
What kind of bacteria is Bacillus anthracis?
Gram positive rods in CHAINS
Obligate AEROBE
What kind of capsule does Bacillus anthracis have?
polypeptide capsule (contains D-glutamate) - ONLY BACTERIUM with this
Bacillus anthracis toxins
- Edema factor: adenylate cyclase causes increased cAMP and fluid enters extracellular space –> inhibits host defenses and phagocytosis
- Lethal factor: Exotoxin that cleaves MAP kinase (normally controls cell growth) and causes tissue necrosis
a. What does edema factor do?
b. What bacteria is it associated with?
a. It activates adenylate cyclase to cause increased cAMP and fluid enters the extracellular space –> inhibits host defenses and phagocytosis
b. Bacillus anthracis
a. What does lethal factor do?
b. What bacteria is it associated with?
a. Exotoxin that cleaves MAP kinase and causes tissue necrosis
What diseases does Bacillus anthracis cause?
a. Cutaneous anthrax - painless papule –> black eschar
b. Pulmonary anthrax - Wool sorter disease
What is presentation of cutaneous anthrax?
Painless papule surrounded by vesicles –> ulcer with black eschar 5 f
What is presentation of cutaneous anthrax?
Painless papule surrounded by vesicles –> ulcer with black eschar (can uncommonly progress to bacteremia and death)
What is presentation of pulmonary anthrax? How do you get it?
Inhalation of spores –>
What is presentation of pulmonary anthrax? How do you get it?
Inhalation of spores –> flu like symptoms that rapidly progress to fever, pulmonary hemorrhage, mediastinitis and shock
How do you treat pulmonary anthrax (wool sorter’s disease)?
Fluoroquinolones
How do you treat pulmonary anthrax (wool sorter’s disease)?
Fluoroquinolones
How do you treat pulmonary anthrax (wool sorter’s disease)?
Fluoroquinolones
Characteristics of Clostridia bacteria
Gram positive, spore forming, obligate anaerobic bacilli
Characteristics of Clostridia bacteria
Gram positive, spore forming, obligate anaerobic bacilli
Who is at risk for Listeria infection?
Infants
Pregnant women
Immunocompromised
Elderly
Who is at risk for Listeria infection?
Infants
Pregnant women
Immunocompromised
Elderly
Branching, filamentous gram positive rods with SULFUR GRANULES
Actinomyces israelii
Reheated rice syndrome
Bacillus cereus
Food poisoning caused by spores that survive cooking rice/pasta
Bacillus cereus