Food-borne bacterial infections Flashcards
What are the defences against infection in the GI tract of the mouth?
Flow of liquids
Saliva
Lysozyme
Normal bacterial flora
What are the defences against infection in the GI tract of the oesophagus?
Flow of liquids
Peristalsis
What are the defences against infection in the GI tract of the stomach?
Acid pH
What are the defences against infection in the GI tract of the small intestine?
Flow of gut contents Peristalsis Mucus: bile Secretory IgA Lymphoid tissue (Peyer’s patches) Shedding and replacement of epithelium Normal flora
What are the defences against infection in the GI tract of the large intestine?
Normal flora
Peristalsis
Shedding and replication of Mucus
What are food-borne diseases?
Results from contamination of food by pathogens that can or cannot multiply in the food
What is food poisoning?
Results from microorganisms having grown on the food to produce
What are the two types of food poisoning?
Infection-type food poisoning
Toxin-type food poisoning
What is infection-type food poisoning?
A sufficiently large population to produce an infective dose
What is toxin-type food poisoning?
Toxin (s) in the food (toxin causes clinical symptoms)
What are some examples of infection-type food poisoning?
Salmonella, Clostridium perfringens, E. coli- GI symptoms
Listeria monocytogenes- systemic symptoms
What are some examples toxin-type food poisoning?
Staphylococcus aureus- enterotoxin
Clostridium botulinum- neurotoxin
Bacillus cereus- emetic and diarrhoeal toxins
What are the two main food-related pathogens in the UK?
Campylobacter- food-borne
Salmonella- food poisoning
What are the main food vesicles for passing disease?
Meat and poultry
What are the greatest singe cause of human morbidity and mortality in the world?
Diarrhoeal diseases
How many people are affected with a gastrointestinal infection in the UK each year?
1 in 5
What is the cost of gastrointestinal infection?
£0.75 billion
How many people with a gastrointestinal infection attend a GP?
1 in 6 cases
What are the possible reasons for the increase in food-related illness?
Increase in large-scale catering
Fast food, convenience foods, packed meals-inadequate storage and reheating
Increase in factory farming (more potential pathogens in animals)
Changing patterns of shopping and food storage in the hormone
“Healthy eating”- non-processed, non-preserved food (not cooking fresh food, preserved foods have anti-bacterial products)
Staff, untrained in hygiene, working in catering establishments
Increase in travel
What is the structure of salmonella?
Motile, non-sporing Gram-negative rods
Facultative anaerobes
How many types of serotypes are there in Salmonella?
> 2000
What are serotypes?
Serotypes are groups within a single species of microorganisms, such as bacteria or viruses, which share distinctive surface structures.
What is S. Typhi?
Human, systemic infection (typhoid fever)- no animal source- bloodstream and reticuloendothelial system infection
Where does food poisoning salmonella come from?
Animal source
e.g. S. Enteritidies, S. Typhimurium- fever, diarrhoea, vomiting, abdominal pain
What is typhoid and enteric fever?
Invasive disease restricted to humans
What is typhoid and enteric fever associated with?
Associated with lack of public health services
Associated with contaminated food/water
What is typhoid and enteric fever caused by?
Salmonella Typhi
Salmonella Paratyphi A, B, C
What is the source of salmonella?
Live in food animals GI tract
How can cross-contamination spread?
From raw meat and poultry to cooked food
Inadequate cooking and storage temperature
What is the steps of pathogenesis for salmonella?
Toxins not clearly demonstrated
Localised invasion of intestinal mucosa- facultative intracellular parasites
Type III secretion systems essential for virulence
Bacteria pass through M cells, taken up by macrophages, multiply and lyse macrophages
Inflammatory response gives rise to disease symptoms
Patients may continue to excrete the organism for weeks/months after recovery
What are the steps of salmonella invading epithelial cells?
Cell opens up Produces a ruffle Induce membrane ruffle Goes inside the cell Goes into a vacuole Into the lamina propria of the gut Immune response produces macrophages Results in blood in diarrhoea
What induces membrane ruffles?
Proteins
What type of pathogen is salmonella?
Intracellular
Can survive and grow inside cells
What does salmonella prevent allowing it to live in the cell?
Prevents the phagolysosome fusion
What is Campylobacter?
C. jejuni (normal flora in chicken)- slender, motile, Gram-negative curved or spiral rods
What are sources of getting campylobacter?
Common gut inhabitants of animals, poultry, domestic pets
Meat infected with gut contents at slaughter
Survive well on chickens processed rapidly and staying moist
Cross contamination
How does campylobacter survive in the GI tract?
Capsule
At what age is person to person transmission of campylobacter more likely?
Children
What is c. jejuni and c. coli most frequently identified to cause?
Acute infective bacterial diarrhoea
What is zoonosis?
Pathogens acquired from animals via food (or direct contact)
What is the pathogenesis of c. jejuni and c. coli?
Facultative intracellular parasites
What do c. jejuni and c. coli invade?
The mucous membranesof the gut and produce
Cytotoxin (s)- responsible for tissue
Destruction and inflammatory diarrhoea
What does c.jejuni and c.coli cause?
Causes blood in diarrhoea
Sets up response in lamina propria
Causes white cell production
Caused by tissue invasion
What are the 3 general preventative measures?
Prevention of contamination of food
Prevention of growth of pathogen
Rejection of suspected foods
