Presentation on theme: "Microbial Diseases of the Digestive System"— Presentation transcript:
1Microbial Diseases of the Digestive System 25Microbial Diseases of the Digestive System
2Microbial Diseases of the Digestive System 2nd most common illness in USTransmitted in food and water after being shed in the feces of infected people/animalsFecal-oral cycle can be broken byProper sewage disposalDisinfection of drinking waterProper food preparation and storage- more of our food products are grown in countries with poor sanitation
4Normal Microbiota>700 species in mouth, each microliter of saliva contains millionsEnormous amounts in large intestine, up to 40% of fecal massBacteroides, E. coli, Enterobacter, Klebsiella, Lactobacillus, ProteusMost assist in enzymatic digestion and synthesis vitamins
5Dental CariesUnlike 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 mutansSaliva-flushes the mouth & food “brushes”Before table sugar in 1600’s, caries not a problemPreventive care: brush, floss, cleanings, low sugarFigure 25.3
6Periodontal DiseaseCaries of cementum and gingivitis caused by streptococci, actinomycetes, and anerobic gram neg. Inflammation and degeneration of structures supporting the teethGingivitis- bleeding gums while brushingPeriodontitis (chronic gum disease)- pus pockets form around teeth, loosening teethAcute necrotizing ulcerative gingivitis, Vincent’s disease, trench mouth- painful chewing, foul breath
7Bacterial 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
8Staphylococcal Food Poisoning Staphylococcus aureusImproperly 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 hoursFigure 25.6
9Shigellosis (Bacillary Dysentary) Longer incubation period: 12 hours to 2 weeks, reflecting the time needed to grow in hostShigella producing Shiga toxinSym : Fever, abdominal cramps, doesn’t enter bloodTrans: person to person with outbreaks in families, day-care, etc.Shiga toxin causes inflammation and bleeding, up to 20 bowel movements/dayFigures 25.7, 25.8
10Salmonellosis/ (Salmonella gastroenteritis) Salmonella entericaIncubation hoursSym: moderate fever, nausea, cramps, diarrheaSeptic shock can occur in infants and elderlyProper cooking poultry (& cutting board cleanup), eggs or pet reptilesFigure 25.9
11Typhoid Fever Salmonella typhi Sym: fever, malaise after 2 week incubation, lasting 2-3 weeksBacteria is spread throughout body in phagocytes.Trans: by contact with human feces1 to 3% recovered patients become carriers, harboring Salmonella in their gallbladder.Vaccines for high risk labs, military personnel
12Cholera Vibrio cholerae serotypes that produce cholera toxin. Sym: watery stools with mucus “rice water stools” & vomiting, could lose 3-5 gallons fluid/dayTrans: waterFigure 25.11
13Noncholera VibriosTrans: contaminated crustaceans or mollusks: raw oysters, shrimp, crabSym:Abdominal pain, vomiting, burning stomach
14Escherichia 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 symptomsEnterohemorrhagic 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.
15Campylobacter Gastroenteritis Campylobacter jejuni2nd most common cause of diarrhea in USon almost all retail chicken60% of cattle transmit in feces and milkSym: Abdominal cramps, fever, diarrhea, dysentery
16Helicobacter Peptic Ulcer Disease Helicobacter pyloriSym: Peptic ulcer disease (stomach ulcers), gastritis, GI ulcers, can lead to stomach cancerProduces ammonia, which neutralizes stomach acid allowing bacteria to colonize creating ulcerTreated with antibioticsFigure 11.12
18Yersinia Gastroenteritis Y. enterocolitica and Y. pseudotuberculosisCan reproduce at 4°C, so refrigeration doesn’t effect itUsually transmitted in meat and milkSym: diarrhea, fever, headache, abdominal pain
19Clostridium Infections Clostridium perfringens GastroenteritisGrow in intestinal tract, producing exotoxinAssociated with meats contaminated with intestinal contents during animal slaughter.Clostridium difficile–associated diarrheaGrows following antibiotic therapyAssociated with hospitalized patients and nursing home residents.
20Bacillus cereus Gastroenteritis Cause of outbreaks of food borne illnessHeating does not always kill the spores which germinate as the food coolsAsian rice dishes susceptibleIngestion of bacterial exotoxin produces mild symptoms: nausea, vomiting, diarrhea
21Viral Diseases of Digestive System Viruses do not reproduce in the digestive system like bacteria, they invade many organs associated with the system.
22Mumps Mumps virus enters through respiratory tract via saliva. Infects parotid glands days later: swelling, feverPrevented with MMR vaccineFigure 25.15
23HepatitisInflammation of the liver with necrosis of the hepatocytes and swelling due to a mononuclear response.Sym: loss of appetite, malaise, fever, jaundiceAt least 5 different viruses cause hepatitisHepatitis may result from drug or chemical toxicity, Epstein-Barr (EB)virus, cytomegalovirus (CMV)
25Viral Gastroenteritis Rotavirus:90% of children under 3 have been infected1-2 day incubation; 1 week illnessNorovirus:“winter vomiting virus”1-2 day incubation; 1-3 day illnessTreated with rehydrationFigure 25.17
26Fungal diseases of the Digestive system Some fungi produce mycotoxins.If ingested can damage kidney, liver, blood diseases, nervous system disorders, even cancerDiagnosis based on finding the fungi or mycotoxins in the suspected food.
27Mycotoxins Claviceps purpurea Fungus grows on grains causing smut Produces ergot: Toxin restricts blood flow to limbs; causes hallucinationAspergillus flavusMold grows on grainsProduces aflatoxin: Toxin causes liver damage; liver cancer
28Protozoan diseases of Digestive System Ingested as resistant, infective cysts and are shed in greatly increased numbers as newly produced cysts.
30Cryptosporidiosis Cryptosporidium hominis Transmitted by oocysts in contaminated water, mostly from cattleSym: headache, sweats, vomiting, severe abdominal cramps, and diarrheaFigure 25.19
31Cyclospora Diarrheal Infection Cyclospora cayetanensisTransmitted by oocysts in contaminated water on berries or uncooked foodsSym: watery diarrheaProtist was first identified in 1993
32Amoebic Dysentery (Amoebiasis) Entamoeba histolyticaAmoeba feeds on RBCs and GI tract tissuesSym: severe dysentery containing blood/mucusSevere bacterial infection will occur if GI wall is perforatedFigure 12.18b
33Helminthic diseases of the Digestive System Poor sanitationFew symptomsNot all make cystsHave definitive host where adult form livesAre multicelluarWell adapted to host or vice versa
34Helminthic Diseases of the Digestive System Figure 25.21
35Tapeworms Taenia Transmitted as larve in undercooked meat Cysticerci may develop in humans are travel to other organs (even the eye)Diagnosed by observing fecesFigure 12.27
37Hydatid Disease Echinococcus granulosus Definitive host: Dogs, wolves transmit to humans via fecesMigrate to liver, lungs, brainTreatment is surgicalFigure 25.23
38Pinworms Enterobius vermicularis Definitive host: Humans Transmitted by ingesting eggs, exit via anus (causing itching)
39Hookworms Larvae in soil hatched from eggs shed in feces Larvae bore through bare skin; migrate to intestineFigure 12.30
40Ascariasis Ascaris lumbricoides Is an intestinal roundworm Transmitted by ingesting Ascaris eggs via mouth, nose, anuslarvae penetrate into lymphatics and capillaries around intestineslarvae migrate to the pharynx, get swallowed and return to intestines to matureFigure 25.25
41Trichinosis Trichinella spiralis Larvae encyst in muscles of humans and other mammals (pork and bear)migrate from intestines to blood and various body tissuesTransmitted by ingesting larvae in undercooked meat or handling meatFigure 25.26a–b