Micro - Clinical Bacteriology (Gram + Rods) Flashcards
Pg. 130-131 Sections include: Corynebacterium diptheriae Spores: bacterial Clostridia (with exotoxins) Anthrax Bacillus cereus Listeria monocytogenes
What disease does Corynebacterium diphtheriae cause, and how?
Causes diptheria via exotoxin endoded by Beta-prophage; Potent exotoxin inhibits protein synthesis via ADP-ribosylation of EF-2
What are the symptoms of Diphtheria?
(1) Pseudomembranous pharyngitis (grayish-white membrane) with LAD (2) Myocarditis (3) Arrhythmias
How is a lab diagnosis of Diphtheria made?
(1) Gram-positive rods with metachromatic (blue and red) granules (2) Elek’s test for toxin
What prevents diphtheria?
Toxoid vaccine
What special agar is used to isolate Corynebacterium diphtheriae, and how does it appear on this agar?
Cystine-tellurite agar; Black colonies
What does Coryne mean?
Club shaped
What is a useful mnemonic to relate to Corynebacterium diphtheria?
ABCDEFG = (1) ADP-ribosylation (2) Beta-prophage (3) Corynebacterium (4) Diphtheria (5) Elongation Factor 2 (5) Granules (metachromic)
When do spore-forming bacteria produce spores, and why?
End of stationary phase, when nutrients are limited
What advantages do spores have?
Highly resistant to heat and chemicals
What is found in the core of spores?
Dipicolinic acid
What is important to remember about the metabolism of spores?
No metabolic activity
How are spores killed?
Must autoclave (as is done to surgical equipment) by steaming at 121 C for 15 minutes
What are 3 examples of spore-forming gram-positive bacteria that are found in soil? What are 3 examples spore formers not found in soil?
SOIL - (1) Bacillus anthracis (2) Clostridium perfringens (3) C. tetani; OTHER - (1) B. cereus (2) C. botulinum (3) Coxiella burnetii
What kind of bacteria are Clostridia?
Gram-positive, spore-forming, obligate anaerobic bacilli
What are the Clostridia with exotoxins?
(1) C. tetani (2) C. botulinum (3) C. perfringens (4) C. difficile
What kind of exotoxin does C. tetani produce? What is the general mechanism of this exotoxin? What other toxin has the same general mechanism?
TETANOSPASMIN (exotoxin causing tetanus); Tetanus toxin is a protease that cleaves releasing proteins for neutrotransmitters; Botulinum toxin
In general, what is tetanus? More specifically, what is the mechanism by which it occurs?
Tetanic paralysis; Tetanospasmin blocks glycin and GABA release [inhibitory neurotransmitters] from Renshaw cells in spinal cord
What symptoms does tetanus cause?
(1) Spastic paralysis (2) Trismus (lock jaw) (3) Risus sardonicus
What kind of exotoxin does C. botulinum produce? What is the general mechanism of this exotoxin? What other toxin has the same general mechanism?
BOTULINUM TOXIN; Protease that cleaves releasing proteins for neurotransmitters; Tetanospasmin (i.e., Tetanus toxin)
What is botulinum toxin? What is the specific mechanism by which it works?
Preformed, heat-labile exotoxin; Inhibits ACh release at neuromuscular junction, causing botulism
What kind of paralysis does botulism cause? What is this disease called in babies?
Flaccid paralysis; Floppy baby syndrome
What is the cause of botulism in adults versus babies?
ADULTS - ingestion of preformed toxin; BABIES - ingestion of spores in honey –> floppy baby syndrome
What exotoxin does C. perfringens produce? What kind of activity does it have?
Alpha toxin (lecinthinase); phospholipase (activity)
What does C. perfringens’ alpha toxin (i.e., lecinthinase) cause?
Cause myonecrosis (gas gangrene) & hemolysis; Think: “PERFringens PERForates a gangrenous leg”
What kind of exotoxin(s) does C. difficile produce? What is/are the mechanism(s) of this/these exotoxin(s)?
(1) Toxin A (enterotoxin) - binds to brush border of the gut (2) Toxin B (cytotoxin) - destroys the cytoskeletal structure of enterocytes (causing pseudomembranous colitis)
To what does C. difficile (and its two exotoxins) often occur secondary? Give specific examples.
Antibiotic use, especially clindamycin or ampicillin
How is C. difficile diagnosed?
Detection of one or both toxins (A and B) in stool
What does C. difficile cause?
DIfficile causes DIarrhea
How is C. difficile treated?
Metronidazole or Oral Vancomycin
Name and describe the bacteria that causes Anthrax. In this description, include gram stain, morphology, what it produces, & what makes it unique.
Bacillus anthracis - gram-positive, spore-forming rod that produces anthrax toxin; Only bacterium with a polypetide capsule (contains D-glutamate)
How is cutaneous anthrax transmitted? How does it present?
Contact; Boil like lesion => Ulcer with black eschar/crust (painless, necrotic) => uncommonly progresses to bacteremia and death
How is pulmonary anthrax transmitted? How does it present?
Inhalation of spores; Flu-like symptoms that rapidly progress to fever, pulmonary hemorrhage, mediastinitis, & shock
In general, what is Woolsorters’ disease? With which bacteria and condition should you associate it?
Inhalation of spores from contaminated wool; Bacillus anthracis - Pulmonary anthrax
What does bacillus cereus cause? What is it sometimes called in this case, and why?
Food poisoning; Reheated rice syndrome - Spores survive cooking rice & Keeping rice warm results in germination of spores & enterotoxin formation
Again, what kind of disease in general does Bacillus cereus cause? What are the types of this disease? What are their symptoms and time course?
Food poisoning; (1) EMETIC TYPE - nausea and vomiting within 1-5 hours (2) DIARRHEAL TYPE - watery, nonbloody diarrhea and GI pain in 8-18 hours
With what kinds of food is the emetic type of food poisoning caused by B. cereus seen?
Rice and pasta
What is the preformed toxin of B. cereus to remember? What kind of food poisoning does it cause?
Cereulide; Emetic type
What kind of microbe is Listeria monocytogenes?
Facultative intracellular microbe; (also gram + rod)
How is L. monocytogenes acquired?
By ingestion of unpasteurized milk/cheese and deli meats, via transplacental transmission, by vaginal transmission during birth
How does L. monocytogenes move from one cell to another, and what advantage does this have? What is a defining characteristic of its movement?
Form “rocket tails” (via actin polymerization) that allow them to move through cytoplasm and into cell membrane, thereby avoiding antibody; Characteristic tumbling motility
What disease(s) does L. monocytogenes cause in pregnant women?
(1) Amnionitis (2) Septicemia (3) Spontaneous abortion
What disease(s) does L. monocytogenes cause in immunocompromised patients?
Meningitis
What disease(s) does L. monocytogenes cause in neonates?
(1) Granulomatosis infantiseptica (2) Neonatal meningitis
What disease(s) does L. monocytogenes cause in healthy individuals?
Mild gastroenteritis
How is L. monocytogenes treated? Be specific to condition and affected population.
Gastroenteritis usually self-limited (in healthy individuals); Ampicillin in infants, immunocompromised patients, & elderly in empirical treatment of meningitis
What is unique about L. monocytogenes among other gram positive organisms?
Only gram-positive organism to produce LPS
