campylobacter jejuna Flashcards
as a new disease
- campylobacter fetus was well established as a veterinary pathogen in cows/ sheeps and rarely humans
- in 1972 first report of C.jejuni isolated from faeces of patients with enteritis using a filter technique
- employed a microaerobic environment
what did Mark Skirrow demonstrate
- 1977
- demonstrated that campylobacters could be isolated from faeces of patients with diarrhoea using a new method
- involved a selective antibiotic containing medium and incubation in an atmosphere of 5% oxygen at 43 degrees
campylonacter jejuni - the organism
- gram negative, motile, spiral
- campylobacter derived from Grek for curved rod
- microaerophilic - similar to related bacterium helicbacter pylori
- grows best at 37-42 degrees
- higher temps are selective and represent higher body temperatures of avian species
- belongs to epsilon subdivision of the proteobacteria
the disease
- classic symptoms of infection are an acute self limiting gastroenteritis
- estimated 2-5 days incubation following ingestion
- sometimes fever
- typically, 3 -10 days of inflammatory diarrhoea follow with presence of leukocytes
- can contain blood, pus, mucus
- abdominal cramping common
- infection resolves generally without treatment
- bacteraemia is rare - immunocompromised
what can more serious cases be treated with
antibiotics e.g. erythromycin or fluoroquinolones
- resistance is now problematic
diagnosis
- direct microscopy of faecal samples - spiral bacteiral with a characteristic rapid darting motility
- latex agglutination with specific antisera coated on beads
- PCR
- typically based on culture of organism on antibiotic containing selective agar plates incubated at 42 degrees
- colony morphology, gram stain and phenotypic tests
treatment and resistance
- most of those infected will not seek medical support and infection will resolve
- staying hydrated is important
- antibiotics are used for more serious cases
- typically, macrolides erythromycin and azithromycin or fluoroquinolones typically ciprofloxacin
- floroquinolone resistance is increasingly problematic
- multi drug resistance is also emerging
campylobacter in the UK
- commonest cause of bacterial gastroenteritis in the UK
- estimated 500,000 cases in england and wales annually
- summer peak is consistent feature around June/ July
- in low and middle income countries constant exposure to campylobacter is thought to lead to immunity in adults
- there is significant infant mortality assicated with this endemic infection
campylobacter and chickens
- estimated 70% of campylobacter cases linked to chicken
- it is commensal in chickens
- colonise to very high numbers in the chicken caecum
- carriage is largely asymptomatic
- no effective strategy to reduce levels of campylobacter in this food product
virulence
- lack of classical virulence features
-no T3SS though does have flagella based system for injecting proteins - no enterotoxins though do produce cytolethal distending toxin
key properties of organism
- cell shape and flagella mediated motility
- ability to generate cell surface structural diversity for longer term colonisation in animal hosts
- mimicry of host gangliosides on cell surface by lipooligosaccharide
- secretion of proteins into host cells via. flagella based secretion system
generating strain diversity - natural transformation
- C.jejuni naturally competent for DNA up take and transformation
- specific uptake system to transport DNA across membrane barriers into cytoplasm
RecA recombinase for integration of homologous DNA into the chromosome - naturally transformable bacteria recognise closely related DNA through presence of short hyperabundant DNA uptake equences
- C. jejuni does not use this mechanism to recognise DNA from other campylobacters
- in contract a campopylobacter transformation system methyltransferase methylates RAATTY sites on C. jejuno DNA and only methylated DNA can transform in campylobacter strains
generating strain diversity - phase variation
- a number of campylobacter genes contain intragenic homopolymeric tracts
- typically, single nucleotide repeats of 8-12 G or C residues
- these are error prone during replication so that the number of repeats varies randomly
- this leads to reversible on-off switching of production of functional protein
- influence structure of LOS, CPS and flagellin glycan
- creates extensive surface diversity
C.jejuni lipo-oligosaccharide
the C.jejuni outer membrane contains LOS - truncated structure that lacks O antigen which is present in LPS
- terminates in a short oligosaccharide
- in many strains, this region contains unusual sugar sialic acid
- by coating the cell in human ganglioside - lipe epitopes C.jejuni will potentially reduce recognition by the host and consequent immune response
- this can lead to autoimmunity due to production of antibodies against C.jejuni LOS
how many cases can lead to giullain- barre or miller-fish syndrome
approx 1 in 1000 cases of C.jejuni infection
