Gram positive bacteria - rods and branching Flashcards
Which two bacteria are gram+ branching filaments?
Actinomyces and Nocardia
Which bacteria is gram+ branching filament and anaerobic?
Actinomyces
Which bacteria is gram+ branching filament and acid-fast?
Nocardia
Which gram+ branching filament is found in normal oral flora?
Actinomyces
Which gram+ branching filament is found in soil?
Nocardia
What disease manifestations are associated with Actinomyces?
- oral/facial abscesses that drain through sinus tracts
- yellow sulfur granules
What is actinomyces treated with?
Penicillin
What disease manifestations is Nocardia associated with?
Immunocompromised: pulmonary infections
Immunocompetant: Cutaneous infxns after trauma
What is nocardia treated with?
Sulfonamindes
Which gram+ organisms are found in rods?
Clostridium, Bacillus, Listeria, Corynebacterium
Which gram+ rods are spore-forming?
Clostridium and Bacillus
What are the sub-species of Clostridium?
Perfringens
Difficile
Botulinum
Tetani
How are all clostridia classified?
Gram+, spore-forming, obligate ANAEROBIC bacilli
What toxin is C. tetani associated with? How does the toxin work?
tetanospasmin, an exotoxin causing tetanus. Tetanospasmin is a protease that cleaves SNARE proteins, preventing release of GABA and glycine neurotransmitters from Renshaw cells in spinal cord.
What is the presentation associated with C. tetani?
Spastic paralysis, trismus (lockjaw), risus sardonicus (raised eyebrows and open grin)
How can C. tetani be prevented/treated?
Antitoxin
Tetanus vaccine (+ booster)
Diazepam for muscle spasms
What toxin is C. botulin associated with? How does the toxin work?
Botulinum toxin; pre-formed, heat-labile toxin. Released upon death of bacteria. Cleaves SNARE proteins, inhibiting release of Ach at the neuromuscular junction.
What is the presentation associated with C. botulinum?
Adult botulism: from ingestion of pre-formed toxin. Cranial nerve palsies, muscle weakness, respiratory paralysis
Infant botulism: from ingestion of spores (honey). Floppy baby, constipation.
Wound Botulism: puncture wounds/deep space. No GI prodrome.
What is the treatment for botulism?
Anti-toxin, human BIG for infant bot, penicillin, supportive therapy.
What is the toxin associated with C. perfringens? How does it work?
12 toxins, including Alpha-toxin, lecithinase, which splits lecithin into phosphocholine and diglyceride
What does C. perfringens cause?
Myonecrosis (gas gangrene), and hemolysis.
What toxin is associated with C. difficile?
Toxin A: Enterotoxin, binds to brush border of the gut.
Toxin B: Cytotoxin, causes cytoskeletal disruption via actin depolymerization
What presentation is associated with C. difficile? What precipitates C. diff infection?
Pseudomembranous colitis –> diarrhea.
Abx use precipitates, esp clindamycin or ampicillin.
How to diagnose C. diff?
Detect toxins in stool by PCR
How to treat C. diff?
Metronidazole or oral vancomycin.
If recurrent, try fidaxomicin, or fecal transplant.
What toxins are associated with Bacillus cereus?
- Spores survive cooking. Keeping rice warm –> germination of spores and enterotoxin formation.
- Emetic type: Cereulide, preformed toxin, heat stable. N/V w/in 1-5 hrs
- Diarrheal type: Heat labile, similar to e.coli/cholera toxin.: Watery, non-bloody diarrhea and GI pain w/in 8-18hrs.
What antibiotics work for B. Cereus
For food poisoning, none (caused by pre-formed toxin).
For eradication, resistant to beta-lactam abx. Vanc/clinda.
No capsule!
What kind of capsule does B. anthracis have?
Polypeptide capsule containing D-glutamate. Anti-phagocytic.
What toxin is B. anthracis associated with? How does it work?
Exotoxin: 3 proteins
- Protective antigen (PA) –> Binding B subunit, allows entry into target cell
- Edema factor (EF) –> Calmodulin-dependent adenylate cyclase, increases cAMP, impairs neut function and causes massive edema (disrupts water hemostasis)
- Lethal factor (LF) –> Zinc metalloproteinase that inactivates protein kinase. Stimulates mac to release TNFalpha and IL-1B, which contributes to death.
What is the most common presentation of B. anthracis?
Cutaneous anthrax (95%): painless papule surrounded by vesicles –> ulcer w/ black eschar, painless, necrotic. Uncommonly progresses to bacteremia/death.
What can inhalation of B. anthracis cause?
Pulmonary anthrax: inhalation of spores causes flu-like symptoms that rapidly progresses to fever, pulmonary hemorrhage, mediastinitis, and death.
What is the reservoir of B. anthracis?
Sheep, goats, cattle. (*woolsorter’s disease).
What is the vaccine for anthrax?
Composed of protective antigen (PA). For high risk individuals.
How is anthrax treated?
Cipro/doxy
Raxibacumab (inhalational)
What are corynebacterium shaped like?
Club shaped
What two cultures do corynebacterium appear on?
Cysteine-tellurite agar: black colonies
Loeffler’s medium: gram+ rods, >12 hrs stain with methylene blue–> metachromic (blue and red) granules - Babes-Ernst.
What encodes the diphteriae exotoxin?
B-prophage (lysogenic conversion)
What is the exotoxin of diphtheriae?
B(binding)-subunit permits entry into cardiac and neural tissue
A (actin)-subunit inhibits protein synthesis by inactivating EF2 via ADP-ribosylation.
What are the sx of diphtheria?
Pseudomembranous pharyngitis +LAD - gray/white exudate.
Myocarditis/AV conduction block/arrythmia
Neural involvement: peripheral nerve palsies, GB-like sx, palatal and cranial neuropathies
What does the vaccine for diphtheria contain?
Formalin-inactivated exotoxin: antibodies to B-subunit are protective.
What are the tests for diphtheria toxin?
Schick test: injection of exotoxin into skin
Elek test: detects toxin - looks for precipitin 45 degree lines.
What do listeria look like?
Gram positive non-spore forming rods, have flagella; “rocket tails” that allow intracellular movement and cell to cell spread across cell membranes, avoiding antibody. “Tumbling motility”
What is the virulence factor of listeria?
Only gram+ organism to produce endotoxin.
Listeriolysin O and phospholipases allow escape from phagolysosomes of macrophages.
Hemolysin - heat labile and antigenic.
Where is listeria acquired from?
Unpasteurized dairy products, cold deli meats, transplacental transmission, or vaginal transmission.
What are the presentations of listeria?
- Amnionitis, septicemia, and abortion in preggos
- Meningitis in neonates, elderly, and immunosuppressed
- Granulomatosis infantiseptica
- Gastroenteritis in healthy individuals.
What is the treatment for listeria?
Ampicillin/trimethoprim/sulfamethoxazole for meningitis
