Chapter 25: Microbial Diseases of the Digestive System

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Chapter 25 Microbial Diseases of the Digestive
System
Trichinellosis larva become encysted in muscle
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The Human Digestive System
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Normal Microbiota

• Millions of bacteria per ml of saliva
• Large numbers in large intestine
• 100 billion bacteria per gram of feces

Defenses

• Stomach Acidic
• Small intestine Paneth cells

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Dental Caries (Tooth Decay)
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The Stages of Tooth Decay
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Bacterial Diseases of the Mouth
Disease Pathogen
Dental caries Streptococcus mutans
Periodontal disease Porphyromonas spp.
Acute necrotizing gingivitis Prevotella intermedia
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Diseases of Lower Digestive System

• Infection Growth of a pathogen
• Incubation is from 12 hours to 2 weeks
• Fever
• Intoxication Ingestion of toxin
• Symptoms appear 1 to 48 hours after ingestion
• Gastroenteritis Diarrhea or
• Dysentery (Severe diarrhea accompanied by blood
  or mucus)
• Treatment Oral rehydration therapy

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Staphylococcal Food Poisoning
Pathogen Staphylococcus aureus
Foods (custards, cream pies, ham are high risk) Staphylococcus is salt tolerant and can grow in salty foods like ham
Symptoms Nausea, vomiting, and diarrhea within a few hours
Intoxication/Infection Intoxication Enterotoxin (superantigen)
Diagnosis Phage typing
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Events in Staphylococcal Food Poisoning
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Shigellosis (Bacillary Dysentery)
Pathogen Shigella spp.
Symptoms Abdominal cramps, fever, tissue damage and dysentery in 12 hrs to 2 wks (possible death in children lt5)
Etiology Infection spread person to person
Intoxication/Infection Infection Endotoxin and Shiga exotoxin
Diagnosis Isolation of bacteria
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Invasion of Intestinal Wall by Shigella
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Shigellosis
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Salmonella

• 50 serotypes in US
• Spread through feces contact or with contact of
  contaminated pet reptiles, chicken their eggs
• Bacteria spread throughout body in phagocytes
• 13 of recovered patients become chronic carriers

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Disease Salmonellosis Typhoid Fever
Pathogen Salmonella enterica Salmonella typhi
Mode of transmission Food, water Water, person to person
Symptoms Nausea, diarrhea, cramps within 12-36 hrs High fever, significant mortality
Intoxication/ Infection Infection Endotoxin Infection Endotoxin
Diagnosis Isolation of bacteria serotyping Isolation of bacteria serotyping
Mortality lt1 infants elderly Quinolones cephalosporins
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Salmonellosis
Gram negative rods
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Determine the Salmonella Source
Food Exposed Exposed Not Exposed Not Exposed
Food ill (a) Not ill (b) ill (c) Not ill (d)
Chicken salad 47 40 6 13
Cole slaw 32 20 21 33
Fruit salad 34 30 19 23
Potato salad 42 39 11 14
Tomato salad 47 24 6 29
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Determine the Salmonella Source
Food Relative Risk
Chicken salad 1.71
Cole slaw 1.58
Fruit salad 1.17
Potato salad 1.18
Tomato salad 3.86
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Vibrios

• Cholera
• Vibrio cholerae serotypes that produce cholera
  toxin
• Toxin causes host cells to secrete Cl, HCO, and
  water
• Noncholera vibrios
• Usually from contaminated crustaceans or mollusks
• V. cholerae serotypes other than O1, O139,
  eltor
• V. parahaemolyticus
• V. vulnificus

Gram negative rods
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Disease Cholera Noncholera vibrios Noncholera vibrios
Pathogen Vibrio cholerae O1 and O139 V. parahaemolyticus V. vulnificus
Symptoms Diarrhea with large water loss (rice water stools) Cholera-like diarrhea, but generally milder Rapidly spreading tissue destruction
Intoxication/Infection Cholera toxin (exotoxin) Infection, enterotoxin Infection, siderophores
Diagnosis Isolation of bacteria Isolation of bacteria Isolation of bacteria
Often through contaminated seafood (shrimp)
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Escherichia coli Gastroenteritis

• Pathogenic E. coli O157H7
• Attach to intestinal cells with fimbriae
• Produce toxins
• May aggregate

Most species are harmless and help produce
Vitamin K in the intestines
Gram negative rods
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Escherichia coli O157H7 Gastroenteritis
Disease Travelers Diarrhea STEC
Pathogen Enterotoxigenic, enteroinvasive, enteraggregative E. coli Shiga-toxin-producing E. coli
Symptoms Watery diarrhea Shigella-like dysentery hemorrhagic colitis and hemolytic uremic syndrome
Most common cause of Travelers diarrhea
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Escherichia coli Gastroenteritis
Disease Travelers Diarrhea STEC
Intoxication/Infection Infection Endotoxin Via contaminated water food Infection Shiga exotoxin Food, water, fecal contamination
Diagnosis Isolation of bacteria Isolation of bacteria
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Campylobacter Gastroenteritis
Pathogen Campylobacter jejuni
Symptoms Fever, abdominal pain, diarrhea
Intoxication/Infection Infection
Diagnosis Isolate bacteria
Reservoir Chickens, cows milk
second most common cause of diarrhea in the
United States
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Helicobacter Peptic Ulcer Disease
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Helicobacter Peptic Ulcer Disease
Pathogen Helicobacter pylori
Symptoms Peptic ulcers from the Helicobacter growing in the mucosa (makes NH3 that neutralizes stomach acid)
Intoxication/Infection Infection
Diagnosis Urea breath, bacterial culture
Treatment Antimicrobial drugs
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Yersinia Gastroenteritis
Pathogen Y. enterocolitica, Y. pseudotuberculosis
Symptoms Abdominal pain and diarrhea, usually mild may be confused with appendicitis
Intoxication/Infection Infection Endotoxin
Diagnosis Bacterial culture serotyping
Transmitted Meat, milk (can grow in refrigerator!)
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Clostridium and Bacillus Gastroenteritis
Pathogen C. perfringens C. difficile B. cereus
Symptoms Diarrhea Diarrhea to colitis Nausea and vomiting diarrhea
Intoxication/Infection Infection Exotoxin Infection Exotoxin Intoxication
Diagnosis Isolation of bacteria Cytotoxin assay Isolation of bacteria
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Clostridium and Bacillus Gastroenteritis
Pathogen C. perfringens C. difficile B. cereus
Transmitted Metronidazole discontinue other antibiotic therapy
Source of Infection Meats Elimination of normal microbiota Rice dishes
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Viral Diseases of the Digestive System
Disease Mumps Viral Gastroenteritis Viral Gastroenteritis
Pathogen Mumps virus Rotavirus Norovirus
Symptoms Swollen parotid glands Vomiting, diarrhea, 1 wk Vomiting, diarrhea, 23 days
Incubation 1618 days 13 days 1448 hrs
Diagnosis Symptoms EIA PCR
Treatment Preventive vaccine Oral rehydration Oral rehydration
In 2040 of men past puberty, the mumps virus
can cause Orchitis (visible swelling of the
testicles)
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Hepatitis Viruses
Disease Transmission Pathogen Chronic Liver Disease? Vaccine?
Hepatitis A Fecal-oral (esp. seafood) Picornaviridae No Inactivated virus
Hepatitis B Parenteral, STI Hepadnaviridae Yes Recombinant
Hepatitis C Parenteral Filoviridae Yes None
Hepatitis D Pareteral, HBV coinfection Deltaviridae Yes HBV vaccine
Hepatitis E Fecal-oral Caliciviridae No HAV vaccine
HAV 50 of cases are subclinical HBV is very
serious, spread through body fluids
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Hepatitis B Virus (HBV)
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Applications of Microbiology A Safe Blood Supply

• Nucleic acid testing (NAT) is used to test
  donated blood and plasma
• HCV
• HIV
• West Nile virus
• Virus-inactivation is used on plasma

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Diseases in Focus Viral Hepatitis

• After eating at one restaurant, 355 people were
  diagnosed with the same hepatitis virus.
• Can you identify infections that could cause
  these symptoms?

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Diseases in Focus Viral Diseases of the
Digestive System

• An outbreak of diarrhea began in mid-June, peaked
  in mid-August, and tapered off in September. A
  clinical case was defined as diarrhea (three
  loose stools during a 24-hour period).
• Can you identify infections that could cause
  these symptoms?

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Mycotoxin Intoxications
Disease Ergot Poisoning Aflatoxin Poisoning
Pathogen Claviceps purpurea Aspergillus flavus
Symptoms Reduced blood to limbs Liver cirrhosis liver cancer
Intoxication/ Infection Mycotoxin in grain Mycotoxin in food
Diagnosis Sclerotia in food Immunoassay for toxin in food
Treatment None None
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Giardia lamblia
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Giardiasis
Pathogen Giardia lamblia
Symptoms Protozoan adheres to intestinal wall, diarrhea, abdominal cramps, nausea may persist for weeks
Reservoir Water or mammals
Diagnosis FA test
Treatment Metronidazole quinacrine
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Cryptosporidium hominis
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Cryptosporidiosis
Pathogen Cryptosporidium hominis
Symptoms Self-limiting diarrhea may be life-threatening in immunosuppressed people
Reservoir Cattle water
Diagnosis Acid-fast stain FA ELISA
Treatment Oral rehydration
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Cyclospora Diarrheal Infection
Pathogen Cyclospora cayetanensis
Symptoms Watery diarrhea
Reservoir Humans birds
Diagnosis Microscopy
Transmission Contaminated produce, human to human, bird droppings
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Entamoeba histolytica (Amoebic Dysentery)

• Transmission through water/food contaminates or
  human to human
• Parasite that feeds on Red Blood Cells
• Severe infections result in abscesses.

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Worldwide Prevalence of Helminthic Diseases
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Tapeworms

• contracted by the consumption of undercooked
  beef, pork, or fish containing encysted larvae
  (cysticerci)

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Tapeworms and Hydatid Disease
Disease Tapeworm Hydatid Disease
Pathogen Taenia saginata T. solium Diphyllobothrium latum Echinococcus granulosus
Symptoms Neurocysticercosis Tissue damage
Intermediate Host Cattle, pigs, fish Humans
Definitive Host Humans Dogs
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Tapeworms and Hydatid Disease
Disease Tapeworm Hydatid Disease
Diagnosis Microscopic exam of feces Praziquantel albendazole
Treatment Serology X-ray exam Surgical removal albendazole
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Hydatid Disease
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Ophthalmic Cysticercosis
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Echinococcus granulosus
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Pinworms
Pathogen Enterobius vermicularis
Symptoms Itching around anus
Intermediate host Humans
Definitive host Humans
Diagnosis Microscopy
Treatment Pyrantel pamoate
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Pinworms
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Roundworms
Disease Hookworms Ascariasis Trichinellosis
Pathogen Necator americanus, Ancyclostoma duodenale Ascaris lumbricoides Trichinella spiralis
Symptoms Anemia Few Few
Intermediate Host Larva in soil Human Mammals
Definitive Host Human Human Human
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Roundworms
Disease Hookworms Ascariasis Trichinellosis
Diagnosis Microscopy Microscopy Biopsy ELISA
Treatment Mebendazole Mebendazole Mebendazole corticosteroids
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Ascariasis lumbricoides
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Heartworm
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Hookworms
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Life Cycle of Trichinella spiralis