Microbial Foodborne Infections and Intoxications Flashcards
What is Gastro-enteritis?
Inflammation of the digestive tract, causing nausea, vomiting, abdominal pain, diarrhoea, eventually fever
What are the causes of Gastro-enteritis?
- Viral= norovirus, rotavirus, adenovirus
- Bacterial= infection (viable microorganisms/ intoxication (only toxin)
- Parasite= giardia, cryptosporidium, Entamoeba, histolytica
Which bacteria cause infection or intoxication?
- Infection = campylobacter spp, salmonella spp, shigella spp, listeria monocytogenes
- Intoxication= clostridium perfringens, bacillus cereus, staph aureus, clostridium botulinum, vibrio cholerae
- Both= E.Coli
Describe serious symptoms
- Invasive diarrhoea
- Duration >3 days
- >
- 5 stools a day
- T>38* “Bloody” diarrhoea (dysentery, colitis)
- Bad general condition
What is the differences in presentation in the small or large bowel?
- Small (fluid secretion/ nutrient absorption)= watery diarrhoea, abdominal cramping, bloating, gas
- Large (absorb fluid and salt)= watery or bloody/ mucoid diarrhoea, low abdominal pain, fever
Which pathogens show which presentations?
- Watery, no fever= cholera
- Watery, fever= norovirus, rotavirus, ETEC, Bacillus cereus, Staph Aureus
- Bloody, no fever= Entamoeba histolytica, campylobacter, salmonella
- Bloody, fever= shigella, campylobacter, non-typhi salmonella, C. perfringens, EIEC/ EHEC
What are the modes of transmission?
- Food, drinking water, person to person
- Endogenous pathogens, contaminated with faeces
- Not cooked thoroughly
- Faecal contamination of hands and clothes, contact fingers put in mouth
What is the infective dose?
The number of pathogens needed to cause disease in the new host
- Varies with pathogen
- Relatively high for all bacteria
- Enteric least, cholerae highest
Describe campylobacter infection
Commonest cause of diarrhoea in the developed World ❖ C. jejuni and C. coli ❖ Associated with poultry (frozen), wild birds and other animals - milk and water ❖ Sporadic in rich countries ❖ Incubation: 24-72h; Duration: 1 week ❖ Very wide range of clinical manifestations ❖ !! Guillain-Barré Syndrome!! Immune response to nerves -Microaerophilic, gram-negative curved rods, non-spore forming, grow well at 42 degrees (birds)
Describe Non-typhi salmonella spp infection
❖ Major cause of foodborne disease world-wide (2nd after Campylobacter) ❖ Associated with poultry/eggs (>< Typhi: Only human reservoir) ❖ Sporadic and outbreaks ❖ Incubation: 6-48h; duration: 1-7 days ❖ Very wide range of clinical manifestations ❖ Often serious: fever, diarrhoea, vomiting -Gram-negative, non-spore forming, facultatively anaerobic bacilli -MDR antibiotic
Describe Clostridium perfringens intoxication
❖ Associated with bulk cooking of meat
❖ Warm food - contamination by spores which
germinate.
❖ A culture of vegetative bacteria is ingested
❖ Bacteria sporulate in small intestine and produce an
enterotoxin
❖ Destruction of villus tips with
resultant pain and diarrhoea
❖ (+ Myonecrosis!)
❖ Often large outbreaks
❖ Incubation: 8-22h;
duration: 1-2 days
-Aerotolerant, gram-positive rods, forming endospores
-Supportive treatments
Describe Clostridium botulinum intoxication
❖ « Botulism » = toxin-mediated paralytic illness ❖ 3 big clinical manifestations ❖ « Neuro-Botulism » ❖ Foodborne Botulism ❖ Wound botulism ❖ Widely distributed in Nature - Produces the most powerful natural toxin ❖ Soils, lake sediments, vegetables, GI tract of mammals, birds and fish. Home-canned or fermented foods ❖ 1μg lethal for 200000 mice or one human -Anaerobic, spore-forming, toxin types A-G
Describe Staph Aureus intoxication
❖ Common skin organism
❖ Contaminates salted foods and dairy produce
❖ Toxins = heat stable!
❖ Incubation: 2-6 h; Duration: 1-24 h
❖ Very acute vomiting response often followed by
diarrhoea
❖ Staph enterotoxins are bacterial
super antigens
-Gram positive coccus, aerobe (facultative anaerobes), nonmotile, non-spore forming
Describe Bacillus cereus intoxication
❖ Resist extreme temperature - form biofilms
❖ Spore germinate in warm cooked rice
❖ Spores ingested - Vegetative cells - Toxin
❖ Acute vomit response followed by diarrhoea
❖ Incubation: 1-5 h; Duration: 12-24 h
❖ Separate toxins for vomiting
and diarrhoea responses!
(ingestion of toxin directly for
vomiting response)
-Aerobic (or facultatively anaerobic), spore-forming gram positive bacilli
Describe norovirus intoxication
❖ Most common viral cause of epidemic gastroenteritis worldwide ❖ « Winter vomiting disease » ❖ Can be sporadic/Small outbreaks (families, the work-place)/ Larger outbreaks (cruise ships, hospitals (ward closures)) ❖ 220.000 deaths/year (children in developing world++) ❖ Extremely stable (heat&cold) ❖ Usually spread directly (feco-oral or droplets of vomit) but some outbreaks associated with shellfish (filter-feeders/ sewage contamination) ❖ Vomiting, diarrhoea, low grade fever ❖ Incubation: c. 24- 48h; Duration: 1-2 days -Small, round structured RNA viruses
