Lecture 24 10/17/24 Flashcards
What is foodborne illness?
any illness resulting from the consumption of food contaminated by pathogenic bacteria, viruses, parasites, chemicals, or natural toxins
What typically results in foodborne illness?
-improper handling
-improper preparation
-improper storage
What is foodborne intoxication?
ingestion of food containing “preformed” chemical toxicants; the toxins cause illness instead of the bacteria that produced the toxins
What are examples of foodborne intoxication?
-staphylococcal food poisoning
-botulism
What is foodborne infection?
pathogens in food survive the digestive processes and overcome the host’s natural defenses
What is an invasive foodborne infection?
organism penetrates the lining of the GI tract and subsequently multiplies
What are the characteristic signs of an invasive foodborne infection?
-dysentery/blood in feces
-fecal leukocytes
-fever
Which pathogens are examples of invasive foodborne infections?
-EIEC
-Salmonella spp.
-Listeria monocytogenes
What is a non-invasive foodborne infection?
organism multiplies in the GI tract without penetrating the GI tract
What is the characteristic sign of a non-invasive foodborne infection?
watery diarrhea
Which pathogens are examples of non-invasive foodborne infections?
-ETEC
-Vibrio cholerae
-Clostridium perfringens
How does foodborne intoxication differ from foodborne infection?
intoxication:
-usually presents within 1 to 7 hours
-usually lacks a fever
infection:
-requires 8 hours to several weeks to present
-fever occurs due to inflammatory response to pathogens
What are the typical growth requirements for foodborne pathogenic bacteria?
-temp. between 40-140 deg. F
-pH greater than 4.6
-water activity greater than 0.85
-variable O2 and nutrient requirements
What are the top 5 foodborne pathogens that result in hospitalization?
-Salmonella spp.
-Norovirus
-Campylobacter spp.
-Toxoplasma gondii
-E. coli (STEC) O157
What are the characteristics of E. coli?
-gram neg. rod
-found in water and food contaminated with feces
-characterized by varying degrees of diarrhea
What are the six pathogenic strains of E. coli in humans?
-EHEC
-ETEC
-EIEC
-EPEC
-EAEC
-DAEC
What are the characteristics of Shiga Toxin E. coli (STEC)?
-E. coli that produces shiga-like toxins or vero toxins
-similar/identical toxin to Shigella dysentariae toxin
-neutralized by shigatoxin antiserum
-cytotoxic
-causes fluid accumulation in GI tract
-causes hemorrhagic colitis
-group of concern is EHEC, which includes O157 and non-O157 STEC
What are the characteristics of enterohemorrhagic E. coli (EHEC)?
-most virulent, with severe clinical disease
-most common strain is E. coli O157:H7
-cattle is primary reservoir host
What do the O and H stand for in E. coli serotyping?
O: cell wall antigen
H: flagellar antigen
What are the characteristics of E. coli distribution and prevalence?
-preferred temp. between 45 and 122 deg. F
-63,000 cases of EHEC in US each year
-world-wide distribution
-low infection rate in cattle and humans
What is the epidemiology of E. coli in humans?
-all ages susceptible, but most common and severe in children and elderly
-children under the age of 5 have highest overall incidence
-children under the age of 5 have highest incidence of hemolytic uremic syndrome
What are the characteristics of E. coli transmission?
-incubation period of 3-4 days
-adults able to spread disease for 1 week
-children able to spread disease for 3 weeks
-common in summer and fall
-seen in rural pop.
What are the clinical signs of E. coli in humans?
-diarrhea ranging from mild and watery to severe and hemorrhagic
-nausea
-vomiting
-abdominal pain
-possibly asymptomatic
What are the characteristics of hemolytic uremic syndrome?
-thrombocytopenia
-hemolytic anemia
-main cause of acute renal failure in children
-case fatality rate around 3.5%
What are the characteristics of thrombocytopenic purpura?
-neurologic symptoms
-thrombocytopenia
-hemolytic anemia
-mortality rate in elderly around 50%
What are the potential routes of transmission for E. coli?
-indirect fecal-oral route in food
-direct fecal oral route between humans or animal and human
What are the common sources of E. coli outbreaks?
-raw/undercooked ground beef/beef products
-raw milk
-unpasteurized fruit juices
-various water sources
-petting zoo animals
-person-to-person
-various produce
What are the prevention steps at the individual level for E. coli?
-wash hands, kitchen surfaces, and utensils
-avoid cross-contamination of other foods
-do not eat raw/undercooked ground beef/products
-cook ground beef to 160 deg. F internal temp.
-practice personal and food safety hygiene at petting zoos
What are the prevention steps at the community level for E. coli?
-surveillance
-notification of disease to health officials
-pasteurization and hygienic slaughter
-waste disposal
-public education and awareness
What are the prevention steps at the livestock level for E. coli?
-proper animal husbandry
-vaccination
-probiotics
-stress reduction
-antemortem inspection
What are the clinical signs of E. coli in animals?
-EHEC: usually asymptomatic
-ETEC: colibacillosis
What are the top five foodborne pathogens that result in death?
-Salmonella spp.
-Toxoplasma gondii
-Listeria monocytogenes
-Norovirus
-Campylobacter spp.
What are the characteristics of Listeria monocytogenes?
-gram pos. rod
-13 serotypes
-reportable disease
-ubiquitous in environment
-found in moist environments, soil, and decaying vegetation
-persistent in food manufacturing environments
What makes Listeria monocytogenes hard to kill in food?
-can grow at refrigeration temps
-salt tolerant
What is the epidemiology of Listeria monocytogenes?
-reservoirs include domestic and wild mammals, birds, and man
-may be free living
-can survive in soil for months to years
-widely distributed by farming techniques and spreading of manure
-can contaminate vegetables, animal feed, and water
What are the characteristics of non-invasive listeriosis?
-fever
-muscle aches
-nausea
-diarrhea
-generally resolves in healthy people
What are the characteristics of invasive listeriosis?
-causes septicemia and meningitis
-pregnant women more susceptible
-mother likely to recover while fetus does not survive
What are the characteristics of listeriosis mortality?
-severe form has a case fatality rate of 15-30%
-increases to 70% with meningitis
-increases to 50% with septicemia
-increases to 80% in perinatal/neonatal infections
What are the incubation periods for listeriosis?
non-invasive: 9-48 hrs
invasive: 2-6 weeks
What are the food sources of Listeria?
-raw milk
-raw or smoked fish/seafood
-meat (including deli meat)
-cheese, especially soft
-ice cream
-raw fruits and vegetables
How is Listeria diagnosed?
-culture from tissue, blood, CSF or sterile site
-stool culture not helpful due to intestinal carriers
How is Listeria treated?
antimicrobial therapy consisting of ampicillin +/- gentamicin; cross BBB
How do humans acquire trichinosis?
eating raw/undercooked meat from animals infected with Trichinella cysts
What is the epidemiology of trichinosis?
-Trichinella spiralis is most common cause in humans
-worldwide dist.
-most cases in US come from eating undercooked wild game rather than pork
What are the clinical signs of trichinosis?
1-2 days:
-GI signs
2-8 weeks:
-muscle pain
-swelling of face
-weakness/fatigue
-chills
-itchy skin/rash
-cough
-fever
-headache
-constipation
How are trichinosis and taeniasis prevented and controlled?
-cook whole cuts of meat to 145 deg. F and allow to rest for 3 minutes before consumption
-cook poultry to 165 deg. F and allow to rest for 3 minutes before consumption
-cook ground meat and all wild game to 160 deg. F
What are the characteristics of Taeniasis?
-Taenia saginata/beef tapeworm
-Taenia solium/pork tapeworm
-can lead to cysticercosis in humans
-infections from eating raw/undercooked beef or pork
What are prions?
family of rare progressive neurodegenerative disorders affecting humans and animals
What are the characteristics of prions?
-long incubation periods
-spongiform changes associated with neuronal loss
-failure to induce inflammatory response
What is the theory behind bovine spongiform encephalopathy pathogenesis?
agent is a modified form of normal protein that changes into pathogenic form to damage CNS of cattle