Microbial Diseases of the Digestive System 25 Microbial Diseases of the Digestive System

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

The Digestive System Figure 25.1

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

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

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

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

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

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

Salmonellosis/ (Salmonella gastroenteritis) Salmonella enterica Incubation 12-36 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

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

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

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

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.

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

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

Helicobacter Peptic Ulcer Disease Figure 25.14

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

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.

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

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

Mumps Mumps virus enters through respiratory tract via saliva. Infects parotid glands 16-18 days later: swelling, fever Prevented with MMR vaccine Figure 25.15

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)

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

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

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.

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

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

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

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

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

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

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

Helminthic Diseases of the Digestive System Figure 25.21

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

Tapeworms Figure 25.22

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

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

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

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

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