Lecture 5 Flashcards
There are __ medically important gram positive bacteria.
6
describe/ name the 6 important bacteria
2 cocci (staphylococci and streptococci)
4 rods (2 spore forming and 2 non spore forming)
Name the 2 spore forming, gram positive bacteria
Bacillus and Clostridium
describe the 2 spore forming, gram positive bacteria
- releases exotoxins
- biochemically different due to its use of oxygen
Bacillus is anaerobic or aerobic
aerobic
Cereus is anaerobic or aerobic
anaerobic
What are the 2 pathogenic species of Bacillus
B.anthracis, B. cereus
- causes the disease anthrax
- only bacteria with capsule made of protein (poly-D-glutamic acid)
-prevents phagocytosis
Bacillus anthracis
who does anthrax infect?
herbivores such as cow and sheep or humans exposed to spores by direct contact with infected animals or soils
What condition is most optimal for B.anthracis
37 degrees Celsius, increased in CO2 and serum proteins
B. anthracis was used for
chemo treatment
chemical peel masks
biological terrorism
phagocytosis
biological terrorism
where is the B.anthracis plasmid encoded on
PXO1
What are the 3 proteins for B. anthracis
- edema factor (EF): disrupts water homeostasis
- protective antigen (PA): promotes entry of EF into phagocytic cells (similar to B subunit of A-B toxins)
- lethal factor (LF): zinc metalloprotease that inactivate protein kinase
What are the 2 mandatory plasmids for bacterial virulence
PXO1 and PXO2
Antibiotics for B.anthracis
Antibiotics: penicillin, doxycyclin, ciprofloxacin or levofloxacin
What is the difference between B.cereus and B.anthracis
motile, non capsulated and resistant to penicillin
B. cereus effects of disease
food poisoning (nausea, vomiting and diarrhea) when spore are present in food, which survive initial cooking process
What do B. cereus do in food ? how do we stop germination?
They germinate in food and release enterotoxin. Food must be exposed to high temperature and/ or reirrigated in order to inactivate spores
2 types of enterotoxins are made
Heat- liable toxin (similar to cholera and LT from E. coli
1. Nausea, abdominal pain, diarrhea
2. Last usually 12-24 hours
Heat-stable toxin
1. Similar to S. aureus food poisoning
2. short incubation period
3. severe nausea and vomiting
4. Limited diarrhea
A patient presents w/ food poisoning (and examination of food reveals B. cereus) can antibiotics be given?
-antibiotic therapy will not alter the course of patient symptoms this is b/c its the preformed toxin that cause the food poisoning
What are Clostridium species?
- Gram positive, spore forming rods, anaerobic
- famous for botulism, tetanus, gas gangrene and pseudomembranous colitis
-exotoxin are extra powerful; rapidly diagnose or patient dies
-produces lethal neurotoxin that causes rapidly fatal food poisoning
- neurotoxin blocks release of acetylcholine (Ach) from nerve terminals in autonomic nervous system
Clostridium botulinum
flaccid muscle paralysis results (Clostridium botulinum)
- afebrile
- bilateral cranial nerve palsies
- double vision
- difficulty swallowing
- general muscle weakness (leads to sudden respiratory paralysis and death)
What does Botulism result from? how to destroy spores?
-adult botulism result form eating smoked fished
-improperly prepared home canned vegetables. Properly cooking
-infant botulism associated to fresh honey contamination with spores
How does improper canning allow for optimal growth of spores
anaerobic condition allowing for growth and synthesis of neurotoxin
What happens during infant botulism?
- spores germinate and bacteria colonize infants intestinal tract
- neurotoxin release
- constipation for 2-3 days, followed by difficulty swallowing and muscle weakness (floppy baby)
What is the treatment for Clostridium Botulinum
antitoxin, neutralizes unbound free neurotoxin in bloodstream
-intubation and ventilatory support until respiratory muscle resume activity
-gram positive, spore forming, anaerobic
-skin trauma by an object with contaminated spores (step on a rusty nail)
-found in soil and animal feces
Clostridium tetani
What happens once Clostridium tetani is in your wound
-will germinate as long as there is anaerobic conditions
exotoxin in Clostridium tetani is called _________ and causes sustained contraction of skeletal muscle (tetany)
tetanospasmin
where does tetanospasmin act on
inhibitory Renshaw cells interneurons (prevent release of GABA and glycine, which inhibit neurotransmitters)
What happens after GABA and glycnine is released
- inhibitory interneurons allow motor neurons to send high frequency impulses to muscle cells (sustained tetany ensues)
what are clinical presentation of tetanus include?
sever muscle spasms (trismus, aka lockjaw), grotesque grinning expressions (risus sardonicus)
When is the mortality rate high in tetanus
once lockjaw is acheieved
is there a vaccine for tetanus
humans are given formalin-inactivated toxin (tetanus toxoid) every 10 years as booster and is part of the DPT shot
-gas gangrene
-mature in anaerobic conditions and produce gas
-common in soldier wounded in battle
Clostridium Perrigin
What are the steps of cellulitis/wound infection
1.necrotic (dead) skin exposed to bacteria
2. bacteria grows and damages local tissue
3. palpitation reveals moist, spongy, crackling consitency to skin due to gas (creptius)
clostridial myonecrosis
1.innoculated with trauma into muscle, secretes exotoxin destroying adjacent muscle
2.gas formation when are fermented from action of enzyme
3.CT scan will show pocket of gas within muscles and subcutaneous tissue
4.enzyme degrades muscle (gets thin, blackish fluid exuding skin)
5. atal unless identified and treated very early with hyperbaric oxygen and
antibiotics (such as penicillin), with removal of necrotic tissue
clostridium difficile is more common than anthrax, tetanus, and botulism (T/F)
T
what cause the growth of clostridium difficle
responsible for antibiotic-associated pseudomembranous enterocolitis
- arises from overuse of broad spectrum antibiotics (ampicillin, clindamycin, and
cephalosporins), which destroy normal intestinal flora
what part of the body does C. difficile infect
the colon
C.difficile What does toxin A cause? Toxin B? what are the symptoms
A. Diarrhea,
B. cytotoxic to colonic cells.
symptoms: Severe diarrhea, abdominal cramping and fever
When would a doctor thing that C.difficile is a viable diagnoses
when patient develops diarrhea on antibiotics (toxin in stool confirms diagnosis)
What is the treatment plan for C. difficile
- discontinue initial antibiotic regimen
- Administer metronidazole or vancomycin by mouth since they are not absorbed orally into bloodstream.
What are the names of non-spore forming rods
Listeria monocytogenes and Cornyebacterium diphtheririae
How many protective barriers can Listeria monocytogenes cross?
- blood-brain, gastrointestinal, and
feto-placental
Gram positive, non spore forming, crosses 3 protective barriers
-may leads to general malaise, meningitis, spontaneous abortions
general malaise, to meningitis to spontaneous
abortions (stillbirth) to death
why is listeria monocytogenes considered a facultative intracellular organism
it can live outside or within cells
what is not a problem for medical proffesionals when treating L. monocytogenes
antimicrobial resistance (treatments include ampicillin and trimethroprim-sulfamethoxazole)
L. monocytogenes is a psychrophile what does this mean?
it survives in the refirgerator
What does Corynebacterium diphtheriae do?
causes diphtheria
- colonizes the pharynx, forming a grayish pseudo membrane composed of fibrin, leukocytes,
necrotic epithelial cells and C. diphtheriae cells
- from here, bacteria releases powerful exotoxin into bloodstream
- exotoxin damages heart and neural cells by interfering with protein synthesis
What is the 3 step treatment of Corynebacterium diphtheriae
Treatment consists of 3 steps
1- antitoxin to inactivate circulating toxin
2- penicillin or erythromycin to kill the bacteria
3- DPT vaccine (D = diphtheria)
What is a unique way to get ride of C. diptheriae
lysogenized by a temperate bacteriophage
Bacteriophage codes for diphtheria exotoxin, which contains two subunits. What are they called and what do they do?
Bacteriophage codes for diphtheria exotoxin, which contains two subunits. The B subunit
binds to target cells and allows A subunit to enter, and the A subunit blocks protein synthesis
(inactivates elongation factor EF2)
