1. Microbial Diseases of the Digestive System25
Microbial Diseases of the Digestive System

2. Microbial Diseases of the Digestive System
2nd most common illness in US
Transmitted in food and water after being shed in the feces of infected people/animals
Fecal-oral cycle can be broken by
Proper sewage disposal
Disinfection of drinking water
Proper food preparation and storage- more of our food products are grown in countries with poor sanitation

3. The Digestive System
Figure 25.1

4. Normal Microbiota
>700 species in mouth, each microliter of saliva contains millions
Enormous amounts in large intestine, up to 40% of fecal mass
Bacteroides, E. coli, Enterobacter, Klebsiella, Lactobacillus, Proteus
Most assist in enzymatic digestion and synthesis vitamins

5. Dental Caries
Unlike any exterior surface, teeth do not shed surface cells but have hard exterior which allows accumulation of microbes: plaque (biofilm)
Caries-enamel and dentin are eroded exposing the pulp to bacteria, Streptococcus mutans
Saliva-flushes the mouth & food “brushes”
Before table sugar in 1600’s, caries not a problem
Preventive care: brush, floss, cleanings, low sugar
Figure 25.3

6. Periodontal Disease
Caries of cementum and gingivitis caused by streptococci, actinomycetes, and anerobic gram neg. Inflammation and degeneration of structures supporting the teeth
Gingivitis- bleeding gums while brushing
Periodontitis (chronic gum disease)- pus pockets form around teeth, loosening teeth
Acute necrotizing ulcerative gingivitis, Vincent’s disease, trench mouth- painful chewing, foul breath

7. Bacterial Diseases of the Lower Digestive System
Symptoms usually include diarrhea, gastroenteritis, and dysentery (severe diarrhea: bloody/ mucus) and fever. Treated with fluid and electrolyte replacement- oral hydration. Gastroenteritis- diseases causing inflammation of stomach and intestinal mucosa.
Infection is caused by growth of a pathogen:
Incubation is from 12 hours to 2 weeks.
Intoxication caused by ingestion of bacterial toxin:
Symptoms appear 1 to 48 hours after ingestion, no fever

8. Staphylococcal Food Poisoning
Staphylococcus aureus
Improperly stored foods become contaminated by handling, bacteria grows & releases toxins.
Illness due to ingesting enterotoxin (which can withstand boiling up to 30 min.) Toxins triggers brain’s vomit reflex.
Symptoms: nausea, vomiting, diarrhea begin 1-6 hours after eating, lasts 24 hours
Figure 25.6

9. Shigellosis (Bacillary Dysentary)
Longer incubation period: 12 hours to 2 weeks, reflecting the time needed to grow in host
Shigella producing Shiga toxin
Sym : Fever, abdominal cramps, doesn’t enter blood
Trans: person to person with outbreaks in families, day-care, etc.
Shiga toxin causes inflammation and bleeding, up to 20 bowel movements/day
Figures 25.7, 25.8

10. Salmonellosis/ (Salmonella gastroenteritis)
Salmonella enterica
Incubation hours
Sym: moderate fever, nausea, cramps, diarrhea
Septic shock can occur in infants and elderly
Proper cooking poultry (& cutting board cleanup), eggs or pet reptiles
Figure 25.9

11. Typhoid Fever Salmonella typhi
Sym: fever, malaise after 2 week incubation, lasting 2-3 weeks
Bacteria is spread throughout body in phagocytes.
Trans: by contact with human feces
1 to 3% recovered patients become carriers, harboring Salmonella in their gallbladder.
Vaccines for high risk labs, military personnel

12. Cholera Vibrio cholerae serotypes that produce cholera toxin.
Sym: watery stools with mucus “rice water stools” & vomiting, could lose 3-5 gallons fluid/day
Trans: water
Figure 25.11

13. Noncholera Vibrios
Trans: contaminated crustaceans or mollusks: raw oysters, shrimp, crab
Sym:Abdominal pain, vomiting, burning stomach

14. Escherichia coli Gastroenteritis
Occurs as traveler's diarrhea and epidemic diarrhea in nurseries. “boil it, peel it or don’t eat it”
50% of feedlot cattle may have enterohemorrhagic strains in their intestines, but do not suffer symptoms
Enterohemorrhagic strains such as E. coli O157:H7 produce Shiga toxin, which causes diarrhea. USDA found 90% of ground meats contaminated (cook well).
Shiga toxins can affect kidneys to cause hemolytic uremic syndrome.

15. Campylobacter Gastroenteritis
Campylobacter jejuni
2nd most common cause of diarrhea in US
on almost all retail chicken
60% of cattle transmit in feces and milk
Sym: Abdominal cramps, fever, diarrhea, dysentery

16. Helicobacter Peptic Ulcer Disease
Helicobacter pylori
Sym: Peptic ulcer disease (stomach ulcers), gastritis, GI ulcers, can lead to stomach cancer
Produces ammonia, which neutralizes stomach acid allowing bacteria to colonize creating ulcer
Treated with antibiotics
Figure 11.12

17. Helicobacter Peptic Ulcer Disease
Figure 25.14

18. Yersinia Gastroenteritis
Y. enterocolitica and Y. pseudotuberculosis
Can reproduce at 4°C, so refrigeration doesn’t effect it
Usually transmitted in meat and milk
Sym: diarrhea, fever, headache, abdominal pain

19. Clostridium Infections
Clostridium perfringens Gastroenteritis
Grow in intestinal tract, producing exotoxin
Associated with meats contaminated with intestinal contents during animal slaughter.
Clostridium difficile–associated diarrhea
Grows following antibiotic therapy
Associated with hospitalized patients and nursing home residents.

20. Bacillus cereus Gastroenteritis
Cause of outbreaks of food borne illness
Heating does not always kill the spores which germinate as the food cools
Asian rice dishes susceptible
Ingestion of bacterial exotoxin produces mild symptoms: nausea, vomiting, diarrhea

21. Viral Diseases of Digestive System
Viruses do not reproduce in the digestive system like bacteria, they invade many organs associated with the system.

22. Mumps Mumps virus enters through respiratory tract via saliva.
Infects parotid glands days later: swelling, fever
Prevented with MMR vaccine
Figure 25.15

23. Hepatitis
Inflammation of the liver with necrosis of the hepatocytes and swelling due to a mononuclear response.
Sym: loss of appetite, malaise, fever, jaundice
At least 5 different viruses cause hepatitis
Hepatitis may result from drug or chemical toxicity, Epstein-Barr (EB)virus, cytomegalovirus (CMV)

24. Hepatitis Transmission symptoms Chronic liver disease? Vaccine?
Hepatitis A
Fecal-oral
Fever, headache, jaundice No
Inactivated virus
Hepatitis B
Parenteral, STD
progress liver damage
Yes
Recombinant
Hepatitis C
Parenteral
chronic
Hepatitis D
Pareteral, HBV coinfection
Sever liver damage, high mortality rate
HBV vaccine
Hepatitis E
Pregnant women high mortality rate

25. Viral Gastroenteritis
Rotavirus:
90% of children under 3 have been infected
1-2 day incubation; 1 week illness
Norovirus:
“winter vomiting virus”
1-2 day incubation; 1-3 day illness
Treated with rehydration
Figure 25.17

26. Fungal diseases of the Digestive system
Some fungi produce mycotoxins.
If ingested can damage kidney, liver, blood diseases, nervous system disorders, even cancer
Diagnosis based on finding the fungi or mycotoxins in the suspected food.

27. Mycotoxins Claviceps purpurea Fungus grows on grains causing smut
Produces ergot: Toxin restricts blood flow to limbs; causes hallucination
Aspergillus flavus
Mold grows on grains
Produces aflatoxin: Toxin causes liver damage; liver cancer

28. Protozoan diseases of Digestive System
Ingested as resistant, infective cysts and are shed in greatly increased numbers as newly produced cysts.

29. Giardiasis Giardia lamblia Flagellated, attached to intestinal wall,
Trans: contaminated water
Sym: malaise, nausea, gas, weakness, flatulance, weight loss, cramps
Figure 25.18

30. Cryptosporidiosis Cryptosporidium hominis
Transmitted by oocysts in contaminated water, mostly from cattle
Sym: headache, sweats, vomiting, severe abdominal cramps, and diarrhea
Figure 25.19

31. Cyclospora Diarrheal Infection
Cyclospora cayetanensis
Transmitted by oocysts in contaminated water on berries or uncooked foods
Sym: watery diarrhea
Protist was first identified in 1993

32. Amoebic Dysentery (Amoebiasis)
Entamoeba histolytica
Amoeba feeds on RBCs and GI tract tissues
Sym: severe dysentery containing blood/mucus
Severe bacterial infection will occur if GI wall is perforated
Figure 12.18b

33. Helminthic diseases of the Digestive System
Poor sanitation
Few symptoms
Not all make cysts
Have definitive host where adult form lives
Are multicelluar
Well adapted to host or vice versa

34. Helminthic Diseases of the Digestive System
Figure 25.21

35. Tapeworms Taenia Transmitted as larve in undercooked meat
Cysticerci may develop in humans are travel to other organs (even the eye)
Diagnosed by observing feces
Figure 12.27

36. Tapeworms
Figure 25.22

37. Hydatid Disease Echinococcus granulosus
Definitive host: Dogs, wolves transmit to humans via feces
Migrate to liver, lungs, brain
Treatment is surgical
Figure 25.23

38. Pinworms Enterobius vermicularis Definitive host: Humans
Transmitted by ingesting eggs, exit via anus (causing itching)

39. Hookworms Larvae in soil hatched from eggs shed in feces
Larvae bore through bare skin; migrate to intestine
Figure 12.30

40. Ascariasis Ascaris lumbricoides Is an intestinal roundworm
Transmitted by ingesting Ascaris eggs via mouth, nose, anus
larvae penetrate into lymphatics and capillaries around intestines
larvae migrate to the pharynx, get swallowed and return to intestines to mature
Figure 25.25

41. Trichinosis Trichinella spiralis
Larvae encyst in muscles of humans and other mammals (pork and bear)
migrate from intestines to blood and various body tissues
Transmitted by ingesting larvae in undercooked meat or handling meat
Figure 25.26a–b