1. Gastrointestinal infections

2. In a relatively short time following birth a "normal" flora is established in each part of this tube. Each end of the tube, the oral cavity and the colon, is heavily colonized while the central part of the tube, the stomach, duodenum, jejunum and the proximal half of the ileum, are lightly colonized.

3. Microbial flora:

4. Barriers A. Mucosal epithelium C. Mucous. D. Acidity of the stomach.
E. Bile
F. IgA.
G. Gut motility
H. Peyer's patches.
I. Normal flora
Bacteroides, Prevotella, Clostridium, and Peptostreptococcus Escherichia, Proteus and Pseudomonas

5. Some of the more common factors that compromise barriers
A. Ingestion of antacids
B. Antibiotic therapy
C. Glucosteroid therapy
D. Cancer chemotherapy
E. Radiation therapy
F. Ingestion of pre-formed toxins with food and/or water (Staphylococcus= enterotoxin).
G. Ingestion of microorganisms that produce toxins/enzymes/ immune suppression factors in situ (E. coli, Shigella, Salmonella).
H. Anatomic alterations.

6. Epidemiology
Nearly all persons have had dental caries sometime in their life. Most people have at least one case of diarrhea each year. Children average 2-3 episodes of diarrhea in a year. Diarrhea is the most common cause of death in the developing world. There are over 76 million cases of food poisoning each year in the U.S. Most of the time these diseases are self-limiting and people do not go to their physician unless their symptoms become severe or chronic.

7. Pathogenesis
Intoxication
Attachment
Invasion

8. Intoxication Staphylococcus aureus Botulism
produces an enterotoxin in improperly stored food that upon ingestion causes primarily nausea and vomiting.
Botulism

9. Attachment surface of the epithelial cells
- ETEC E. coli, Giardia lamblia
- watery diarrhea without inflammatory cells or blood in the stools

10. Invasion Campylobacter, Shigella, Salmonella, Rotavirus, Norwalk agent
watery diarrhea (viral gastroenteritis) to bloody mucus covered stool (dysentery; Shigellosis), to invasion of the bloodstream (enteric fever; Salmonella typhi).

11. Manifestations
Mouth; various lesions, dental cavities, tooth pain/sensitivity to hot and/or cold, bleeding gums, petechia, facial pain and/or swelling, abscesses, cellulitis.
Salivary glands: jaw pain when swallowing, swelling under jaws.
Esophagus: dysphagia (difficulty in swallowing), odynophagia (painful swallowing; unique to infectious causes of esophagitis), heartburn, atypical chest pain, regurgitation.
Stomach: vomiting, epigastric pain that occurs 90 min to 3 hours after eating; eating relieves the pain; belching, indigestion, heartburn.

12. Manifestations
Small intestines: large volume watery diarrhea, sometimes fatty stools, increased bowel sounds, cramps, diffuse abdominal pain, no guarding or rebound tenderness, rarely has white blood cells in stool.
Large intestines: small volume bloody diarrhea with mucus in it (dysentery), cramps, diffuse abdominal pain, rarely any guarding or rebound tenderness, frequently has white blood cells in stool, fever.
Liver: upper right quadrant pain of the abdomen, fever, icterus, clay-colored stools, dark urine.
Gallbladder (cholecystitis and cholangitis): Jaundice, right upper quadrant pain, high fever, chills.
Peritoneum: sharp localized abdominal pain aggravated by motion, fever, chills, constipation, abdominal distension, decreased bowel sounds, guarding, rebound tenderness.

13. Laboratory examination
Stools: watery, mucoid or bloody + cultivation
Blood culture for septicemia
Serological tests (e.g., typhoid fever, amebiasis)
Toxin assays
- Fibroblast cell assay for toxin A and B produced by C. difficile.
- ELISA tests (LT of E. coli and cholera toxin of Vibrio cholerae)

14. Infections of the Teeth, Jaw and Mouth
Dental caries- Streptococcus mutans (most common cause; initiates dental cavity), Lactobacillus sp. (appear to be important in progression of lesion deep into enamel and the dentine).
Plaque-associated periodontal disease- gingivitis/periodontal disease- is a polymicrobial process.
The following are commonly seen in these infections: Eubacterium sp., Peptostreptococcus micros, Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Bacteroides forsythus, Fusobacterium nucleatum, Prevotella intermedia, Capnocytophaga sp., Selenomonas sp., Spirochaetes.

15. Diseases of the Periapical Tissue and Jaw
Dentoalveolar abscess- an abscess that forms at the end of the tooth root. (obligate anaerobes, Streptococcus milleri).
Periodontal abscess- an abscess that forms deep in the gums along the tooth root following advanced periodontal disease. Gram-negative rods, streptococcus viridans, anaerobic streptococci, and spirochaetes.
Ludwig’s angina- a cellulitis of the sublingual and submandibular spaces (floor of the mouth). Can rapidly become fatal without treatment (mortality rate before the antibiotic era was 50%) Streptococci, Bacteroides, Fusobacterium, Staphylococcus aureus
Osteomyelitis of the jaw- an inflammation of the bone (medullary space) and the muscles around it. More commonly affects the mandible. (Gram-negative rods, anaerobic streptococci, Actinomyces israelii)

16. Infections of the Tongue and Mouth
Stomatitis is an inflammation of the mucosal surfaces in the mouth and on the tongue.
HSV 1 and 2 viruses and Candida albicans are the most common causes of this inflammation.
- gingivostomatitis
Angular Cheilitis (angular stomatitis, perlèche) is an inflammation of the angles of the mouth. Candida albicans. Staphylococcus aureus

17. Infections of the Esophagus
Candida albicans (most common cause)
Cytomegalovirus (CMV)
Herpes simplex virus (HSV)
Varicella-zoster virus (VZV)
Human Immunodeficiency Virus (HIV)
Other fungi (eg, Aspergillus, Histoplasma, Cryptococcus, Blastomyces)
Epstein-Barr virus (EBV)
In HIV-infected hosts - CMV, HSV, Mycobacterium avium-intracellulare, idiopathic
Human papillomavirus (HPV)
Poliovirus
Bacterial species (eg, normal flora, Mycobacterium tuberculosis, Mycobacterium avium-intracellulare, other)
Parasitic infections ( Trypanosoma cruzi, Cryptosporidium, Pneumocystis, Leishmania donovani)

18. Infections of the Stomach and Upper Duodenum
Chronic Gastritis- is the inflammation or irritation of the stomach lining. Chronic gastritis is usually caused by Helicobacter pylori.
Peptic ulcer disease (PUD)
Duodenal ulcer disease 
Gastric ulcer disease
Helicobacter pylori is also the cause of most of these ulcers
(60-70%).

19. Infections and Intoxications of the Intestines
Bacteria:
Staphylococcus aureus, Bacillus cereus, Clostridium perfringens, Clostridium botulinum, Escherichia coli (ETEC, EPEC, EHEC, EAEC, EIEC), Salmonella sp., Shigella sp., Campylobacter sp., Yersinia enterocolitica, Clostridium difficile, Vibrio cholerae, Vibrio parahemolyticus, Listeria monocytogenes, Aeromonas hydrophila, Plesiomonas sp.

20. Infections and Intoxications of the Intestines
Viruses
Rotaviruses, Norwalk virus, Noroviruses (Norwalk-like viruses), Adenoviruses, Astroviruses, other Caliciviruses, Parvoviruses
Parasites- Giardia lamblia, Entamoeba histolytica, Cryptosporidium parvum, Cyclospora cayetanensis, Diphyllobothrium latum, Ascaris lumbricoides, Trichuris trichiura, Taenia solium, Taenia saginata

21. Intoxications
Bacteria-
Staphylococcus aureus, Bacillus cereus, Clostridium perfringens, Clostridium botulinum

22. Small intestine infections
Bacteria- E. coli (ETEC, EPEC), Clostridium perfringens, Cholera sp., Vibrio sp.
Viruses- Rotavirus, Adenovirus, Calicivirus, Astrovirus, Norwalk virus, Noroviruses (Norwalk-like viruses)
Parasites- Giardia lamblia, Cryptosporidium parvum, Ascaris lumbricoides, Taenia solium, Taenia saginata, Cyclospora cayetanensis

23. Large intestine infections
Bacteria- E. coli (EHEC, EIEC, EAEC), Shigella sp., Salmonella sp., Campylobacter sp., Yersinia sp., Aeromonas sp., Plesiomonas sp., Clostridium difficile
Parasites- Entamoeba histolytica, Trichuris trichiura

24. FOOD TOXEMIA ETIOLOGICAL AGENTS:
Staphylococcus aureus (gram+, aerobic, coccus),                    
Bacillus cereus (gram+, aerobic, rod),
Clostridium perfringens Type A (gram+, anaerobic, rod),
Clostridium botulinum (gram+, anaerobic, rod)

25. VIRAL GASTROENTERITIS
Rotavirus, Adenovirus, Astrovirus, Calicivirus (Noroviruses and Norwalk virus).

26. Bacterial Gastroenteritis- Noninflammatory (no fecal WBC’s) Escherichia coli INFECTION
Enterotoxigenic E. coli (ETEC)- infantile diarrhea and Traveler’s diarrhea
Enteropathogenic E. coli (EPEC)- diarrhea in infants less than 6 months of age
Enteroaggregative E. coli (EAEC)- a major cause of Traveler’s diarrhea, a more persistent diarrhea

27. Vibrio
Vibrio cholerae

28. Other causes of noninflammatory gastroenteritis GIARDIASIS
Giardia lamblia (duodenalis) cysts

29. Cryptosporidium parvum is a coccidium parasite.
Other causes of noninflammatory gastroenteritis primarily associated with immunocompromised hosts. CRYPTOSPORIDIUM PARVUM 
Cryptosporidium parvum is a coccidium parasite.
Cyclospora cayetanensis, Isospora belli, and Microsporida (Enterocytozoon bieneusi)