Campylobacter Flashcards
most common bacterial cause of
infectious intestinal disease in England and Wales.
about three times more common than Salmonella
Most infections are caused by two species
C. jejuni ; C. coli
symptom
abdominal pain
Mild watery diarrhoea
– mainly seen in people in developing countries
Severe diarrhoea with inflammation of the gut
– mainly seen in industrialized nations
a bacterial pathogen causing foodborne illness without
multiplying within the food
how many cases reported in 2009
58,000 reported
Real number may be as high as 450,000 due to
under-reporting. 80 deaths
Characteristics of the family with ______
sequence similarity of their ribosomal RNA molecules
- small curved or spiral rods
– microaerophilic
– do not metabolise carbohydrates
– adapted to live in mucus lining of the intestines
can Subdivided into two families
– Campylobacter, Arcobacter
– Helicobacter, Wolinella, Flexispira
Species of Campylobacter
15 species including:
- C. jejuni -major human enteric pathogen worldwide (80-95% of cases)
- C. coli - (often associated with pigs) (5-20% of cases)
- C. fetus -major veterinary pathogen (
Properties of Campylobacter species
- Gram-negative, curved or spiral rods
- Small size
- Rapid ‘darting’ corkscrew motility - long polar flagella
Grow best with [gas]
reduced oxygen (~5%) and increased CO2 (5-10%)
Optimum & minimum temperature for growth
about 42°C (body temperature of birds)
Minimum growth temperature about 30°C (cannot
normally grow in foods)
Growth condition and nutrient
•Do not metabolize sugars
•Have small genome with few stress response regulons
•Sensitive to heating, freezing, drying, acid, etc.
•Form coccoid cells in old cultures or when exposed to
oxygen (some people think this is a survival mechanism)
Campylobacter infection
- Mainly present in chicken
- Contamination of aqauatic reservoirs
- Present in milk
- Contamination through pets
Infective dose
Infective dose is low
– less than 1,000 cells needed
– children and young adults susceptible
severe type of infection incubation time
usually 2- 5 days, sometimes up to 10 days
severe type of infection Symptoms
• Often starts with fever and headache (50% of people)
• Abdominal pain and diarrhoea (profuse, bloody, mucus)
• Self-limiting (10 days max.). May continue to shed
organisms in faeces without showing symptoms
• Vomiting is uncommon
• Rarely causes death
Complications
Reactive arthritis – inflammation of the joints – usually lasts 2-3 weeks but sometimes much longer – disease mechanism not fully understood
• Guillain-Barré syndrome
– occurs 1-3 weeks after onset of enteritis
– immune attack on myelin sheaths of nerve cells
– can lead to paralysis
– occurs in 1 in 1,000 infections
Treatment
• Usually no special treatment is necessary
– diarrhoea lasts for 2-3 days
– abdominal pain lasts longer
– usually clears up within 10 days but sometimes
longer
– faeces remain positive for 2-7 wks
• Severe cases
– antibiotics (fluoroquinolones, erythromycin)
– rehydration with fluids
Mechanisms
Still poorly understood
– many factors likely to be involved but conclusive
evidence is hard to obtain
– sequence genome to look for genes associated with
virulence in other organisms
– examine behaviour of mutants with particular genes
knocked out
– no suitable animal model available
– can test colonization of chickens, but Campylobacter
lives as harmless commensal in poultry – colonizes
caecum but rarely causes disease
– tissue culture experiments are an alternative
Adaptation to living in gut
Microaerophilic metabolism
– Low oxygen levels near to gut epithelial cells (but not
anaerobic)
Cell shape and motility
– ability to penetrate viscous mucus lining of gut
Iron acquisition
Iron acquisition for Adaptation to living in gut
– intense competition for iron in the gut
– Campylobacter can acquire iron from iron-containing molecules
obtained from the host e.g. haemin or haemoglobin
– siderophores are high affinity iron-binding molecules
– Campylobacter can make use of siderophores such as
enterochelin produced by other bacteria in the gut
Mechanisms for Adaptation to living in gut
Chemotaxis
– attracted towards fucose (a sugar component of mucin)
and serine; repelled by bile acids
• Motility
– long polar flagella and spiral shape help cells to burrow into mucus layer
• Adhesion
– fimbriae similar to those in E. coli have been reported in Campylobacter and may be involved in adhesion
• Invasion
– the ability to invade human cells varies widely between strains
• Toxins
– Campylobacter produce a toxin which does not seem to be a unique characteristic of pathogenic strains.
infections source
- Poultry meat believed to be important
- Unpasteurized milk
- Water
- Domestic pets
Campylobacter in humans
• Most cases are sporadic (scattered with no
obvious pattern)
• Few large outbreaks from a common source
Campylobacter in animals
- Found in poultry, wild birds, cattle, pigs, domestic pets, faecal material in environment
- Well adapted to live in the gut of wild and domestic birds
- Does not cause disease under natural conditions
• Broiler chickens become colonized within 2-3 weeks of life and remain colonized until
slaughter
In 2008, UK has % of broiler chicken sample contained
Campylobacter
In the UK 42% of samples contained less that 100
Campylobacter per gram (cfu/g) and 27% contained
more than 1,000 Campylobacter per gram (cfu/g)
The counts of Campylobacter on broiler carcasses
varied widely between samples
Campylobacter in poultry at slaughter
19
Campylobacter in poultry bought from supermarkets and shops
20
Factors leading to infection
- Consumption of undercooked meats (e.g. BBQ)
- Cross contamination in the kitchen
- Contaminated milk
- Contaminated water
- Occasional faecal-oral route (children and pets)
infection Incidents and consequences
- Free (unpasteurised) milk at a primary school
- Bird-pecked bottles at a day nursery
- Canteen in UK University serving cooked chicken
•Large economic cost of disease - sick days, loss of
production, etc.
Controlling Campylobacter
• FSA has agreed new targets with industry
stakeholders to cut Campylobacter levels in chicken
• Three categories of contamination: (1,000 cfu/g)
• The agreed target is to reduce bird levels in the
highest contamination category from 27% to 10% by
2015, which the FSA says could reduce
Campylobacter cases by up to 30%.
How many chicken slaughtered in UK each year.
About 850m
How to cut Campylobacter?
- Modified atmosphere packaging
- Better farm hygiene
- Hot water treatment or steaming chicken carcasses
- Use of electrolysed water
- Anti-microbial washes such as lactic acid (requires EU approval)
- Better farm hygiene
How to improve farm hygiene
- Hygiene barrier (footwear)
- Hygiene barrier (outside of farm)
- Financial incentives for producers
- Vaccination
- Fly Control
- Earlier Slaughter Age
- UV Water Treatment
- Thinning
