Week 3 - Food Poisoning

Food poisoning

Occurs via sources other than bacteria, ex: consuming food/water contaminated with heavy metals

Gastroenteritis definition

Inflammation of the stomach and intestines

• Can occur via processes other than bacteria (ex: irritable bowel disease)

Most common cause of food poisoning

• Campylobacter most common bacteria

• Salmonella 2nd most common

• Shiga toxin producing E. coli 3rd most common

Campylobacter

• Found in gut of cattle, poultry, and swine

• Microaerophilic - need a lower amount of oxygen than in air

• Catalase pos & oxidase pos

• Gram neg curved rods

Campylobacter transmission

• Has capsules

• Doesn't always cause infection

• Infectious dose is low

• C. jejuni & C. fetus cause reproductive failure in ruminants

• Remains outside intestinal epithelial cells

• Motility is required for infectivity

Salmonella

• Found in gut of vertebrates

• Facultative anaerobes

• Catalase pos, oxidase neg

• Do not ferment lactose

• Do not have capsules

• Are flagellated

Salmonella transmission

• Common carriers are reptiles and birds

• Causes no disease in carriers

• Facultative intracellular pathogen

• Infect the ovaries of chicken and spread vertically

• Person to person spread possible

Shiga toxin producing E. coli (STEC)

• Found in mammalian gut

• Facultative anaerobes

• Catalase pos, oxidase neg

• Can ferment lactose

• Are flagellated

STEC transmission

• Found in farm animals (mainly cattle)

• Less common in other animals

• Animals do not get sick

• Person to person spread possible

• Infectious dose is low

• Very dangerous to humans

Contamination of STEC

• Fecal contamination during slaughter gets contaminate on external surface of meat

• "Mincing" up meat mixes external with internal

• Using manure from infected cattle to fertilize crops can contaminate lettuce & vegetables

Classification system of pathogens

• Classified according to how dangerous they are to humans and/or how difficult to treat the infection

• Number system 1-4, 1 = low risk

• STEC = 3, toxin it produces is very dangerous & treatment can cause more toxin release

Listeria

• Not commensal in animals, causes disease in animals & humans

• Gram pos

• Facultative anaerobes

• Catalase pos, oxidase neg

• Able to replicate at refrigeration temps

• Facultative intracellular pathogen

• Cause severe/deadly disease

Listeria transmission

• Found in ruminants, swine, birds, cats, & dogs

• Found in unpasteurized dairy products, fish, and cured meats

• Facultative intracellular pathogens but don't stay in GIT

• Can migrate to CNS and cause sepsis and meningitis

• Few infections but high mortality rate