Lecture 1: foodborne outbreaks

Some gram negative foodborne pathogens

salmonella, shigella, E.coli, campylobacter 

Some gram-positive foodborne pathogens

Listeria, staphylococcus, clostridium, bacillus

What are the characteristics of salmonella?

• widespread, gram negative enterobacteria

• meat, eggs, unpasteurized milk, eggs, shrimp, cream filled deserts, poultry

• sick after 6-48 hours, sick for 4-7 days, most recover without treatment

• stomach pain, fever, chills, diarrhea and headache\

• low infective dose (15-20 cells) 

• Pathway: bacteria adhere to small intestine lining, can break through wall and get into blood

• example: peanut butter, Cheerios, shawns- trucks carry raw egg product and then was used to carry cream- nationwide outbreak

What are the characteristics of shigella?

• gram negative enterobacteria

• sick 1-2 days after infected

• bloody diarrhea, fever, abdominal pain, feel like you got to poop (tenesmus)

• easily passed around in nursing homes and daycare

• fecal oral route

What are the characteristics of E.coli?

• cattle fecal material

  • feces get on cattle carcass during slaughter and ground up with meat

• gram negative enterobacteria

• spread by poor food washing, not washing hands

• example: apple cider (apples dropping in feces and transmit EHEC)

What are the characteristics of Campylobacter

• C. jejuni

• common in animals, shellfish, and unpasteurized milk, CHICKEN

• sensitive to O2, drying, freezing, salting, acid

• has a heat liable toxin (heat can destroy it)

• can be controlled with proper food handling

• microaerophilic curved/s-shaped gram-negative rod 

• cause gastroenteritis and lead to Gulain-Barre syndrome

• cramps, headache, fever, watery or bloody stools

• 400-500 cells

• sick after 2-3 days

• can become antibiotic resistant (presence of antibiotics in animal food)

What are the characteristics of Listeria?

• gram positive, short rods

• facultative anaerobic, no endospores 

• beta hemolysis: narrow band after stabbing BAP

• mobile at 30

• catalase +

• oxidase -

• incubation of 3-70 days (very difficult to track down)

• L.monocytogenes

  • very virulent

  • about 1600 illnesses, 250 deaths annually in US

• found in soil, IN cantaloupe outbreak

• dairy products

• food handling issue, hot dogs and deli meat

• pathogenicity: septicemia, meningitis, encephalitis, intrauterine/cervical infection (VERY DANGEROUS IN PREGANCY)

• nausea, vomiting, diarrhea 

What are the characteristics of Staphylococcus aureus?

• caused by enterotoxin

  • heat can kill bacteria but not toxin

• vomiting 2-8 hours after eating

• example: UIndy pasta bar chef w boil on hand

• gram positve

What are the two types of clostridium?

perfringines and botulinum, GRAM + RODS

What are the characteristics of clostridium perfringens?

• common in nature

• 6.3 minutes generation time

• heat liable toxin (heat will destroy)

  • 74C destroys

• sub terminal spores survive cooking and grow

• 6-24 hours incubation

• cramps and diarrhea, nausea

• large infective dose rate 

• cooked meat, poultry, gravy

What are spores?

a reproductive cell capable of developing into a new individual without fusion with another reproductive cell

What are the characteristics of clostridium botulininum?

• very dangerous

• 12-36 hours after eating=sick

• spores

• canned food

• like anaerobic environment

• example: potatoes not canned properly

• botox

Infant botulism

• caused by clostridium botulism

• honey has Botulism

  • digestive tract does not destroy spores

  • toxin carried through blood and block ACH

What are the characteristics of bacillus cereus

• gram positive rod

• spore forming

• facultative anaerobe

• nature: rice, potatoes, casserole

• Can cause diarrheal illness (10-16 hours) or vomiting illness (1-6 hours)

• example: TexMex buffet in Columbus- no place in food prep to wash hands and food was not hot enough

  • fried rice had B.cereus

  • chicken has C.perfrigens

Mannitol Egg Plates (B.cereus)

• MYP agar

• yolk in media provides lecithin

• has beef extract, peptone, nitrogen, vitamins and minerals

• mannitol as carb (sugar) source

• phenol red as pH indicator

• microbials to prevent other bacteria growing

• Bacteria ferment mannitol: acidic, colonies are yellow

• Bacteria produce pectinase: zone of white precipitate around colonies

• B.cereus turns pink/red, have nethcinase

Norovirus

• 1/15 in US annually

• 70,000 hospitalized, 800 die

• come in contact through food

• cruise ships, nursing homes

• example: mom’s nursing home and ceaser salad

• sick after 12-48 hours, sick for 1-3 days

• nausea, vomiting, diarrhea

• can still be shedding after 2 weeks

• temporarily immune against strain