5 - Staphylococcal Intoxication Flashcards
Foodborne intoxication occurs from ________________________
ingestion of a food containing a preformed toxin
What are the 5 general characteristics of a foodborne intoxication?
1) Toxin is produced by a pathogen while growing in the food
2) The toxin can be heat stable or heat liable
3) Ingestion of a food containing active toxin, not viable cells is necessary for poisoning
4) Symptoms generally occur quickly, as early as 30 minutes after ingestion
5) Febrile symptoms are not present
What are the 2 things that represent Staphylococcal intoxication:
- grape-like cocci
- vomiting
Staphylococcal typical scenario example:
temperature-abused breakfast on a flight
T or F: recently the prevalence of staph aureus has drastically declined
T, due to better use of refrigeration to store food and improved sanitary practices that can control contamination by Sa.
Staphylococcus aureus is gram_____
postive cocci
Give some characteristics about staph aureus:
- gram positive cocci
- exists as either single cells or grape like clusters
- nonmotile, noncapsular
- non-spore forming, sensitive to heat treatment
- facultative anaerobes but grow rapidly under aerobic conditions
Staph aureus cells are killed at ______ for 12 mins, or _____ for 15 seconds
66
72
Staphylococcus aureus are mesophiles and can grow between ______ but grow rapidly between _______
7-48C
20-37C
What is special about staph aureus?
They can grow at relatively low Aw (0.86), low pH (4.8) and under high salt and sugar conditions
*They can grow under several adverse conditions, but are poor competitors against other organisms, therefore they do very well when adverse environments give them a competitive advantage
T or F: S.aureus is a very common cause of human and animal infections
T
_____________ is commonly used to define the sequence type (ST) or allelic profile based on the sequences of 7 housekeeping genes found in all strains of S. aureus.
Multilocus sequencing typing (MLST)
How many housekeeping genes are found in all strains of S.aureus?
7
If a group of STs share at least _ of _ alleles, the group of STs can be defined as a __________
5, 7 clonal complex (CC).
Five CCs are predominant in human colonization and infection: __________
CC1 CC5 CC8 CC30 CC45
The Sa accessory genome is made of several _______________ which can be transferred horizontally (20% of the Sa genome)
mobile genetic elements
However, S. aureus has a very advanced _________________ that occurs in each of it’s lineages and prevents horizontal gene transfer from occurring between different clonal complexes.
restriction modification system
Most Sa genomes carry between ________ prophage genomes, phage genomes have enterotoxins
1-4
Many enterotoxins are on mobile genetic elements, ____________ are required for foodborne intoxication
enterotoxins
Sa causes foodborne illness through the ingestion of the ______ not the organism
toxin
Enterotoxin:
a toxin that acts on the gastrointestinal tract
Endotoxin:
a toxin that is structurally associated with the bacterial cell (LPS)
Exotoxin:
a toxin that is usually secreted into the extracellular fluid but can be intracellular or injected directly into eukaryotic cells
Exfoliative toxins:
dermolytic exotoxins produced exclusively by Sa that cause the symptoms of impetigo or scalded skin syndrome
All Sa enterotoxins are also:
exotoxins
Sa produces several types of enterotoxins (A to J, without F) that all have a high degree of _______________, and all cause ______________
homology
gastroenteritis
Enterotoxin F, once thought to be an enterotoxin, turned out to be an endotoxin and causes _____________ (Sa enterotoxin B can also be associated with toxic shock syndrome)
toxic shock syndrome
B
Enterotoxins are made throughout most of the __________________
exponential growth phase
Enterotoxin production can be inhibited by the presence of ______
glucose
Enterotoxins may be involved in _______________ in Sa
quorum-sensing
Staphylococcal toxin is unique because it is ______________________
very heat stable – not destroyed by boiling or canning
- therefore when it is in a food it’s there!
The toxin stimulates the ______ and _______ nerves
vagus
sympathetic
___________ are a main environmental source of Sa, we have it on our skin, the interior of the nose is the main site, it spreads by direct contact, skin fragments, and respiratory droplets (blood supply)
people
*also found in erupted acne in humans
Sa is able to ________ our cells and live ____________
invade
intracellularly
T OR F: Sa can acquire resistance to heavy metals and antibiotics
T
T OR F: animals cannot carry Sa
F
Sa is often a cause of _______________, and a variety of infections in agricultural animals
bovine mastitis
What happens when a cow with mastitis is milked?
The bacteria can contaminate milk and dairy products, the cow can also contaminate automated milkers, and facilities contaminating other batches of milk
*If they can grow, the toxins may survive pasteruization
What are common food products associated with S.aureus?
- ground beef
- pork sausage
- shrimp
- oyster
Most contamination is traced to ___________ during food preparation
humans
Organism grows optimally at 37C-40C, only ___ hours required at this temperature for sufficient toxin production
3 (importance to properly refrigerate your food)
contributing factors are:
- inadequate refrigeration
- preparing foods too far in advance
- poor personal hygiene (just wash your hands people)
- inadequate cooking
- prolonged use of warming plates (ie. buffet)
Give me characteristics of staphylococcal intoxication:
- very quick onset (30 mins), mean incubation is 4.4 hours, 10hrs is max time to onset
- self-limiting and recovery in 24-48h
- most cases are not reported
- outbreaks are seasonal (picnics)
- there is NEVER fever
- almost everyone vomits, other symptoms can have nausea, diarrhea, and abdominal pain
is death rare with staph intoxication?
yes
purified toxin is considered a _________ agent
bioterrorism
What does the FDA says about the infectious dose?
- above 10^5 cells/g can cause disease
- 1ng/g of toxin in food can cause illness
Methicillin-resistant Sa (MRSA) carry the _______ gene
mecA
MRSA is the causative agent of _________________________________
soft tissue and skin infection, along with necrotizing fasciitis
How do you prevent staph intoxication?
- hand washing, glove wearing, avoid hiring people with active skin infections
- adequate refrigeration, or continued heating of prepared food (re-heating doesnt help)
- preservatives could be used to kill or arrest growth of the organism
__________ are the important factor and allow symptoms to have a very fast onset
the toxins
staph aureus resides on ____________
skin, nares and hair of humans and animals (any foodstuff that involve human contact, or is from a food producing animal can potentially be infected
Results of Sa food contamination will depend on _________________
the genetic makeup of the particular organisms (does it have the enterotoxin gene)
