Lect 5 : Foodborne pathogens Flashcards
What are the 3 foodborne illness associated with MOs in food?
Infection, intoxication, toxico-infection
How does infection cause us to fall ill?
- Food/water contaminated with virus/bacteria is ingested
- MOs multiply within the gastrintestinal infection to high enough levels to cause sickness
MOs must be viable when consumed to cause infections. True or False?
True
What is the infectious dose for infectionsin general ? (amount of MO we need to consume before causing infection)
Low infectious dose of 10 to 10^6
How long does it take before we get infectons (from time of ingestion)?
> 14 h
What symptom are food infections associated with?
Fever
How to food intoxications occur?
Ingestion of a preformed microbial toxin in a food
does MO need to be viable for intoxication to occur?
No
How long does it take to get intoxication after ingesting the affected food?
< 1-14h
way shorter than infection as bacteria do not need time to multiply, the toxin alr formed
How long does symptoms occur in a toxicoinfection?
12h to 12 days
Are most foodborne pathogens gram positive or negative? Why?
Gram negative, because they have an outer membrane consisting of many virulence factors, which causes sickness
What are the characteristics of Salmonella?
- gram
- shape
- motile (capable of motion)?
- flagella
- gram neg
- rod
- yes, motile
- peritrichous flagella (distributed evenly around cell)
The genus is Salmonella.
What is the family and 2 pathogenic species of salmonella we are concerned with?
Family : Enterobacteriaceae
Species : S. enterica !!!!! and S. bongori
ENTERica ! ENTERS and invades your gastrointestinal tract
How many different types of serovars does Salmonella have?
> 2600
What is the main type of foodborne illness associated with Salmonella?
Infection
** What are the 2 main serovars of Salmonella that cause foodborne infections?
S. Enteritidis
S.Typhimurium
Humans get Salmonellosis from Salmonella. What are some typical symptoms?
- Fever/ chills
2. Headache - Abdominal pain
- Diarrhea
- Nausea / vomitting
What is the infective dose of salmonella?
10-10^6 (considered low infectious dose)
How can salmonella be treated usually, and for severe cases ?
Self-limiting (self treated)
- by drinking oral fluids
Severe cases :
- IV fluid drip for severe diarrhea
- antibiotics
Why does WHO report more cases of salmonella infections in DEVELOPED countries rather than developing countries?
Though developing countries may have poorer hygiene, developed countries have more robust surveillance systems to report cases of salmonella outbreaks
- developing countries -> cases may not be reported
Thus WHO reports higher incidence of Salmonella cases
Where do Salmonella colonise? [4]
Gastrointestinal tracts of
- farm animals
- wild animals (including bird, reptiles)
- pets and zoo animals
- humans after infection
TLDR : gastrointestinal tracts of animals + infected humans
What does it mean by Salmonella is very “smart”?
Salmonella can sense subtle environmental cues brought about by genotype or physiological state of plant host and respond with distinct patterns of gene expression accordingly
What are the implicated foods for Salmonella?
Almost all foods
**Meat, eggs
Fruits and vegetables, seafood, cereals, bakery, RTE foods
Is Salmonella aerobic/anaerobic/facultative anaerobic?
Is it a thermophile/mesophile/psychrophile/psychrotroph?
facultative anaerobic (can survive harsh processing conditions, so prob not fully aerobic/fully anaerobic)
mesophile
How to prevent salmonella from growing? [5]
- maintain cold chain!!! (storing food at 4°C, slows growth as Salmonella is a mesophile)
- good hygiene on farm and during slaughtering
- avoid cross contamination
- cleaning and disinfection of food preparation surfaces
- thorough cooking and heating of foods
What kinds of foods can increase heat resistance of Salmonella?
High fat/protein food –> offer protection for salmonella to hide in
What are the characteristics of STEC (shiga like toxin producing E. Coli)?
- gram
- shape
- motile (capable of motion)?
- flagella
- gram neg
- rod
- yes, motile
- petrichous flagella (distributed evenly around cell)
** Same as salmonella
Most strands of E.Coli are non pathogenic. True or False?
True. E.coli belong to normal intestinal microbiota of humans and animals
What are pathogenic E.Coli classified by?
Classified by their different virulence factors.
What are the names of the 2 important pathogenic E.Coli and what symptoms do they cause?
- Enterohemorrhagic E.Coli (EHEC)
- bloody diarhea and hemoytic uermic syndrome - Shiga like toxin-producing E.Coli
- severe diarrhea, stomach cramps, vomitting
What is the infectious dose of EHEC in what kind of food product and how to treat EHEC?
0.3-15 CFU/g in frozen groud BEEF patties (cattle)
- No treatment available and antibiotics only promote Shiga toxin production
What does EHEC haemolytic uraemia syndrome result in?
Lifelong disability and defects
Why is EHEC/STEC important/relevant?
Although it is not very prevalent (less incidence), it results in severe disease
What is the major reservoir of STEC?
reservoir : habitat where MO multiply
in cattle
What are the characteristics of Virbrio?
- gram
- shape
- motile (capable of motion)?
- flagella
- gram-negative
- straight/curved rods
- motile
- polar flagella (1 flagella on 1 side)
The three impt species of Vibrio are
V.parahaemolyticals
V. vulnificus
V. cholerae
What is the infectious dose of V.parahaemolyticals?
What are its symptoms?
10^5-10^7 CFU
SYMPTOMS :
-WATERY DIARRHEA
- fever
- abdominal cramps
- nausea / vomitting
In general, Vibrio is mild/serious with a high/low infectious dose
mild
high -> need more to get infected
in which regions of the world is vibrio most prevalent in?
Coastal / tropical areas
How to prevent Vibrio from growing to very high levels and causing sickness? [3]
- keep at 4°C or frozen
- cook sufficiently
- prevent cross ccontamination of raw and cooked seafood
What are the characteristics of Campylobacter?
- gram
- shape
- motile (capable of motion)?
- flagella
- gram neg
- spirally curved rods (spiralla)
- RAPID motility, corkscrew-like motion
- AMPHITRICHOUS : single polar flagellum at one or both ends of the cell
What are the 2 species of Campylobacter that are foodborne pathogens? (Not impt)
** C. jejuni
C.coli
What is the infectious dose of C. jejuni (campylobacter)?
What are its symptoms? [3]
<1000 CFU
Fever, diarrhea, abdominal cramps
How to treat infection by Campylobacter?[2]
- fluids as long as diaarrhea lasts
- antibiotics
In terms of foodborne outbreaks for Campylobacter, are most cases from general outbreaks or sporadic cases in household settings?
Household settings
What is the main reservoir of Campylobacter?
Animal reservoir
- gastrointestinal tract of poultry, cattle, pigs, wild birds, rodent, flies
- detected in 25-80% POULTRY (domestic fowl, such as chickens, turkeys, ducks, and geese.)
What foods are affected by Campylobacter?
25-80% of poultry
common in raw milk
Does Campylobacter develop in the food chain?
No
How to prevent food infection by Campylobacter?
Cook raw meats well and avoid cross contamination
What are the characteristics of Listeria Monocytogenes?
- gram
- shape
- motile (capable of motion)?
- flagella
- ** gram positive
- short rods
- motile
- peritrichous flagella
(same as salmonella and STEC) just gram diff
What is the minimum infectious dose for Listeria monocytogenes?
Difficult to determine but around >100 viable cells
Which are the at risk population groups for Listeria Monocytogenes?
YOPI
Young
Old
Pregnant
Immunocompromised
What are the symptoms of listeriosis?
Dependant on state of host
- fever and muscle pain (nausea and diarrhea is rare)
- inflammation of brain
- abortion/stillbirth/premature labour (preg)
What are the reservoirs of Listeria Monocytogenes? [3]
- ubiquitous (present everywhere) in the envrionment such as water, soil,….
- food processing environments
- preserved products with a long shelf life in the refrigerator
How to prevent Listeria Monocytogenes?[2]
- raw foods of animal origins must be completely cooked
- no cross-contamination of raw and uncooked foods
NOTE : impossible to completely eradicate from foods (ubitiqous in environment)
