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22 Cards in this Set
- Front
- Back
Spore Forming Rods
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Bacillus and Clostridium
Release of potent exotoxins causes disease |
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Bacillus anthracis
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Causative agent of anthrax
UNIQUE protein capsule, antiphagocytic Aerobic growth conditions Spores are very stable, resistant to heat, drying, UV and disinfectants; spores germinate and toxins are made Humans exposed to spores usually through contact with animals or soil Used in bio-terrorism and warfare |
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Bacillus anthracis exotoxin
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Encoded on pXO1 plasmid
Plasmid contains virulence factors which are transcribed optimally @ 37 C, increased CO2 and serum proteins ?? Where are these conditions found ?? Exotoxin composed of 3 separate proteins: Edema factor (EF) Protective antigen (PA) Lethal factor (LF) Separately proteins are not toxic, but combined are lethal pXO2 plasmid encodes capsule genes **BOTH plasmids required for virulence** |
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Prevention and Treatment of Bacillus antracis
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RAPID treatment is essential
Antibiotics: penicillin, doxycyclin, ciprofloxacin or levofloxacin Vaccine against PA protein is available Remember: capsule protects AND is made of protein cutaneous and respiratory routes for spores animal hides and/or soil |
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Bacillus cereus
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Causes food poisoning when spores enter food product
Motile, non-encapsulated, resistant to penicillin ENTEROTOXIN is responsible for illness 2 types of enterotoxin (i) Heat labile: nausea, abdominal pain, diarrhea. Lasts 12-24hrs (ii) Heat stable: SEVERE nausea and vomiting, short incubation Antibiotic treatment useless….preformed toxins |
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Clostridium
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Anaerobic > differentiates this bacteria from other
spore-forming bacilli Botulism, tetanus, gas gangrene and pseudomembranous colitis POWERFUL EXOTOXINS RAPID DIAGNOSIS |
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Clostridium botulinum
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Rapidly fatal food poisoning from lethal neurotoxin
Neurotoxin blocks Ach release in autonomic system; flaccid muscle paralysis: Afebrile, bilateral cranial nerve palsies, double vision, trouble swallowing, muscle weakness Respiratory paralysis DEATH Treatment: antitoxin and respiratory assistance Smoked fish, improperly canned vegetables Proper cooking destroys spores |
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Action of Botulinum Neurotoxin
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Botulism toxin inhibits the release of acetylcholine, not allowing the muscle to contract.
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Infant Botulism
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Honey contamination with spores
Spores germinate and bacteria colonizes intestine Neurotoxin release 2-3 days of constipation Trouble swallowing, muscle weakness |
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Clinical Manifestations of Clostridium botulinum
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1. entry
2. absorption 3. spread of toxin 4. disease (flaccid paralysis) |
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Clostridium tetani
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Tetanus
Rusty nail contaminated with spores punctures skin; wound provides anaerobic environment Exotoxin: tetanospasmin Sustained contraction of skeletal muscles Severe muscle spasms (lock jaw); high mortality at this stage Booster (inactivated toxoid) given every 10 years |
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Clinical Manifestations of Clostridium tetani
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1. entry
2. spread of toxin 3. no exit 4. disease (rigid paralysis, jaw locked, cardiac failure, respiratory failure) |
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Clostridium perfringens
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Gas gangrene
Seen in soldiers wounded in battle |
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2 classes of clostridium perfringens infection
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i) Wound infection/cellulitis
-necrotic skin exposed to bacteria, damage to local tissues; skin feels moist, spongy, with ‘crackly’ pockets (ii) Clostridial myonecrosis -bacteria inoculated from trauma into muscles; exotoxin secretion destroys adjacent muscles; as muscles degrade get black fluid excreeted from skin -FATAL unless treated with oxygen, antibiotics (penicillin) and removal of damaged tissue |
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Clostridium difficile
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Causes antibiotic-associated
pseudomembranous colitis Seen more commonly in hospitals than tetanus, anthrax or botulism Overuse of broad-spectrum antibiotics destroys normal intestinal flora Infects colon and releases exotoxins Toxin A: diarrhea Toxin B: cytotoxic to colon cells |
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Clostridium difficile symptoms and treatment
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Symptoms: severe diarrhea, abdominal cramping, fever
Possible cause of diarrhea in patients on antibiotics Treatment discontinue antibiotic treatment Administer metronidazole or vancomycin |
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Clinical manifestations of Clostridium
difficile |
1. entry
2. spread 3. disease |
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Non-Spore Forming Rods
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2 medically important bacilli
Listeria monocytogenes and Corynebacterium diptheriae |
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Listeria monocytogenes
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Causative agent of listeriosis; immunocompromised are at
high risk Found in foods such as soft cheeses, unpasteurized milk, cold cuts, pâté PSYCHROPHILE survives in refrigerator Variety of symptoms: General malaise, diarrhea, meningitis, septicaemia, still-birth/abortions Facultative intracellular aerobe Crosses 3 protective barriers (blood-brain, GI and fetoplacental) Treatment: ampicillin or trimethoprim-sulfamethoxazole |
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Clinical Manifestations of Listeria
monocytogenes |
1. entry
2. invasion 3. spread 4. disease (meningitis, endocarditis) 5. exit |
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Corynebacterium diptheriae
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Causative agent of diptheria
Colonization of pharynx and release of exotoxins into bloodstream Exotoxin damages heart and neural cells Treatment (3 steps): (i) Antitoxin (ii) Penicillin or erythromycin (iii) DPT vaccine Can be lysogenized by a bacteriophage (virus that infects bacteria) |
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Clinical manifestations of C. diptheriae
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1. entry
2. spread 3. disease 4. exit |