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Escherichia coli
most strains are commensal, but some can cause diarrhea
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E. coli associated with diarrhea
EPEC, ETEC, EIEC, STEC (EHEC), EAggEC, DAEC
nonhuman reservoir - STEC (EHEC)
use toxins - ETEC, STEC (EHEC), EAggEC
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E. coli diagnosis
- serotyping
- bioassays - for detection of toxin, tissue culture, invasion assay
- genetic probes and PCR
- detection of EHEC/STEC
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salmonella diseases
- non-typhoidal salmonellosis or enterocolitis
- - aymstomatic infection is most common
- - prevention - proper food handling and storage, cooking food thoroughly, hand washing
- Typhoid fever (enteric fever)
- 1-3% of people will carry and shed organisms for over a year after resolution of symptoms
- preventable with vaccines- also proper sanitation, food handling and washing hands
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salmonella transmission and diagnosis
- person to person via fecal-oral route
- from animal reservoir (enterocolitis only)
- diagnosis through culture of stool or blood
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salmonella invasive pathogenesis
- enter though the M cells
- survive and replicate inside macrophages
- enter lymph nodes, lymphatics and blood stream
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Giardia lamblia
- reservoir - intestines of humans and other animals
- transmission - person to person by fecal-oral route
- causes giardiasis (beaver fever)
- most common protozoan causing diarrhea
- cysts are infective stage
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hepatitis A virus (HAV)
- reservoir - humans
- transmission - fecal-oral
- diagnosis - detection of IgM specific antibodies
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HAV pathogenesis
- traffics to liver, infects hepatocytes
- does not cause cytotoxicity - immune mediated
- antibody response that confers lifelong protection
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HAV prevention
- hygiene
- sanitation
- vaccine - reduced incidence in US
- immune globulin
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ascariasis
- caused by helminth ascaris lumbricoides
- most common helminth infection - 1/4 of world's population is infected
- eggs can survive many years in environment
- transmission is fecal-oral
- reservoir is humans and pigs
- diagnosis by ova in stool
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Acarsis lumbricoides lifecycle
- adult worms made in intestine
- produces fertilized eggs, shed in feces
- eggs develop into infective embryo
- ingested by humans, hatch and invade intestine
- carried to lungs, migrate to throat and swallowed
- develop in intestine
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ascariasis clinical
- can be asymptomatic for a long time
- depend on intensity of infection and location - pulmonary, nutritional deficiency, obstruction of small intestine
- worms can migrate
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ascariasis treatment and prevention
- treatment - antihelminthics
- prevention - poverty alleviation, hygiene, sanitation, sewage systems, education and health awareness, mass treatment
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current issues related to foodborne illnesses
- emerging and re-emerging foodborne pathogens
- changing epidemiology of foodborne diseases
- reasons for emergence and increase in incidence of foodborne diseases
- drug-resistant infections due to food
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classification of foodborne diseases
- toxin-mediated (without infection)
- chemical poisoning
- infection
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infection vs. intoxication
- infection - disease caused my microorganism establishing infection in human host
- longer incubation period
- intoxication - disease caused by ingestion of toxin
- microorganism multiplies in food and produces toxin, not in human host
- short incubation period
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prion diseases
neurodegenerative disease due to accumulation of abnormal protease-resistant protein in the neurons
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changing epidemiology of foodborne diseases
- new or previously unrecognized pathogens
- new vehicles and reservoirs of infection
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reasons for emergence and increase in incidence of foodborne diseases
- industrialization and technology - mass distribution and production
- globalization
- antibiotics in animal feed
- change in types of animal feed
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solutions to increase in incidence of foodborne diseases
- stopping use of antibiotics in food
- feed animals naturally
- smaller, localized production of food
- stricter government oversight
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