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32 Cards in this Set
- Front
- Back
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What are the 3 general pathogenic mechanisms for the development of bacterial gastroenteritis?
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1. Ingestion of preformed toxin - rapid onset of illness
2. Ingestion of organism that produce toxins in vivo that cause disease - may be sudden or delayed onset 3. Infection by enteroinvasive organism - delayed onset of illness |
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Which 2 bacteria affect illness via preformed toxin?
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1. Staph. aureus
2. B. cereus (short inc) |
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Which 5 bacteria affect illness via toxin production in vivo?
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1. C. perfringens
2. B. cerceus (long inc) 3. C. difficile 4. EHEC 5. ETEC |
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Which 4 bacteria affect illness via tissue invasion?
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1. C. jejuni
2. Salmonella 3. Shigella 4. EIEC |
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How does Staph. aureus cause GI illness?
Treatment? |
- ingestion of preformed enterotoxin
- 24 types of toxin - resist degradation in GI tract Treatment = REHYDRATION ONLY |
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What are the cellular characteristics of Bacillis cereus?
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- Gram Positive
- Beta Hemolytic - Catalase Positive - Highly motive / Spore Forming |
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How does Bacillis cereus cause GI illness?
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Either:
1. Ingestion of preformed emetic toxin (sudden illnes, 1-6 hours) 2. Ingestion of large number of bacteria, followed by toxin production. Illness 8-16 hours. |
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What are symptoms of Bacillis cereus?
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- Vomiting
- Cramps - Diarrhea |
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What are the cellular characteristics of Clostridium perfringens?
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- Gram Positive rods
- Beta Hemolytic - Spore Forming |
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How does Clostridium perfringes cause GI illness?
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- Ingestion of organism followed by production of Type A enterotoxin in vivo
- Damages intestinal epithelium |
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What are the only 2 Diarrheal GI Pathogens that require treatment with antibiotics?
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1. Shigella dysenteria - floroquinolone
2. Clostridium difficile - Oral Vancomycin, metronidazole, (and stop offending antibiotic) Everything else is simply treated via rehydration |
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What are the cellular characteristics of the Shigella spp. (4 diff species)?
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- Gram Negative Rods
- Oxidase Negative - Non-motile - Non lactose fermenter |
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How does Shigella cause GI illness?
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- Cross M cells in epithelial (recall: M cells are dendritic cell which present antigens present in gut)
- Causes apoptosis of macrophages - Cell-Cell spread via actin - Low infection dose (~10) |
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Who does Shigella infect?
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- 3RD most common enteropathogen in US
- Higher risk in crowded places / daycare centers |
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What are the syptoms of Shigella?
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Severe presentation, affects lower GI
- BLOODY, MUCOID DIARRHEA - High Fever - Vomiting within 1-3 days |
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How is Shigella treated?
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Fluoroquinolone (1 of only 2 GI bacteria to be treated by antibiotic)
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What are cellular characteristics of Salmonella spp.?
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- Gram Negative Rods
- Oxidase Negative - Motile - Non Lactose Fermenter |
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How does Salmonella spp. cause GI illness?
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- Crosses M cells (similiar to Shigella)
- Apoptosis of macrophages - Invades epithelial cells basolaterally AND disseminates systemically - LARGE infection dose (different from Shigella) - |
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Is Salmonella common?
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- Yes, either 1ST or 2ND most common enteropathogen
- Tied with CAMPYLOBACTER JEJUNI |
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What are the symptoms of Salmonella?
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- Gastroenteritis with 1-3 days
- TYPHOID FEVER - ROSE SPOTS |
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What are the cellular characteristics of Campylobacter jejuni?
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- Gram Negative
- Curved Rods - Oxidase Postive - Catalase Positive |
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How does Campylobacter jejuni cause GI illness?
Common? |
- 1 of the 4 INTRACELLULAR bacteria
- Incubation 1-3 days - Acute inflammatory enteritis - Edema in mucosa Very common - Either 1ST/2ND most common enteropathogen (tied w/ Salmonella) |
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What is a rare complication of Campylobacter jejuni?
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Guillain-Barre syndome
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What are the cellular characteristics of E. Coli?
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- Gram Negative Rods
- Oxidase Negative - Lactose Fermenter - Grows on Blood agar |
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How many different E. Coli species cause disease?
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6
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Which E. coli is the most common source of traveler's diarrhea?
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Enterotoxigenic E. coli (ETEC)
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What is the leading cause of infintile diarrhea in developing countries?
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Enteropathogenic E. coli (EPEC)
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What is the leading cause of bloody diarrhea in developed countries?
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Enterohemorrhagic E. coli (EHEC)
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What are the cellular characteristics of Clostridium difficile?
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- Gram Positive Rods
- Spore Forming - OBLIGATE ANAEROBES |
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What are the major virulence factors of Clostridium difficile?
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2 enterotoxins that target Ras proteins:
1. TcdA 2. TcdB - Disrupts tight junctions - Cytopathic effects |
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When does Clostridium difficile usually develop?
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- After treatment with antibiotic causes normal gut flora to reduce, allow C. difficle to propagate
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How is Clostridium difficile treated?
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- oral Vancomycin
- Metronidazole - If possible, stop offending antibiotic |
