clostridium difficile separating key facts from fiction s p borriello 16.5.08
TRANSCRIPT
Clostridium difficile
Separating key facts from fiction
S P Borriello
16.5.08
1. Pathogenesis
- colonisation resistance
- virulence factors of C.difficile
2. Laboratory diagnosis
3. Treatment and Management
Why should we be interested?
1.It is the most common identifiable cause of nosocomial gut infection
2.It kills
3.It is preventable
PATHOGENESIS
A risk of infection with C. difficile follows antibiotic treatment and
exposure to C. difficile
This risk increases with age. The majority of cases are older
than 60 years.
Disease follows infection with toxigenic strains of C. difficile
and production of toxin in vivo.
Why is it that you need antibiotic treatment to make you susceptible to infection. It is due to the barrier
effect of the normal gut bacteria (colonisation resistance).
What antibiotics cause this disease?
All of them other than parenteral aminoglycosides.
Even chemotherapeutic agents eg 5-fluorouracil can have this effect.
Some antibiotics do seem to pre-dispose to infection more than others eg:
Clindamycin
Cephalosporins, especially 3rd generation
Antibiotic Weighted odds ratio
(95% CL)
Erythromycin 3.5 (2.1 – 5.8)
Clindamycin 7.8 (3.8 – 16.1)
Ceftazidine 28.8 (12.7 – 65.1)
Cefotaxime 36.2 (19 - 68.9)
C. Difficile is due to overgrowth of strains resistant
to the inciting antibiotic
NONO
In the animal model the biggest difference between antibiotics seems to be the length of time susceptibility
is induced.
Comparison of antibiotics in hamsters
Antibiotic Number of deaths on day
(3mg) 1 3 4
Ampicilllin 4/4 1/4 -
Cefuroxime 4/4 0/4 -
Flucloxacillin 6/6 7/8 2/8
C. difficile can cause a range of disease from mild diarrhoea
A number of factors could contribute to outcome of infection eg
Host factors
Degree of disruption of colonisation resistance
Virulence of the C. difficile strain
COMPARATIVE VIRULENCE OF C. DIFFICLE
No. of strains Source Virulence Serogroup Ribotype
5
1
1
3
PMC
AAD
Animal
Infant
High
Medium
Weak
Weak/none
A(x3) S3
I
C
G, ?(x2)
5
9
12
1, 20, 26
Virulence factors of C. difficile
1. Toxins
2. Adhesion
3. Fimbriae
4. Enzymes
5. Capsule
Both toxins A and B are the largest bacterial protein toxins known.
Toxin A 300 kDa
Toxin B 270 kDA
Effects of toxins A and B
A B
Cytotoxicity + +
Haemagglutination + -
Increase vascular permeability + +
Haemorrhage + +
Fluid accumulation + -
Virulence factors of C. difficile
1. Toxins
2. Adhesion
3. Fimbriae
4. Enzymes
5. Capsule
Virulence factors of C. difficile
1. Toxins
2. Adhesion
3. Fimbriae
4. Enzymes
5. Capsule
Virulence factors of C. difficile
1. Toxins
2. Adhesion
3. Fimbriae
4. Enzymes
5. Capsule
Virulence factors of C. difficile
1. Toxins
2. Adhesion
3. Fimbriae
4. Enzymes
5. Capsule
LABORATORY DIAGNOSIS
1. Do not investigate formed stools
2. Do not investigate infants under six months
Faecal cytotoxin is the gold standard.
Vero cells are the best choice cell line.
Kits are available for toxin A or toxin A and B.
Those that detect both are most sensitive.
There also exist toxin A-ve B+ve strains which cause diseases.
Toxin A kits miss these.
Culture is best achieved by growth on a selective medium incorporating cyloserine (250mg/l) and cefoxatin (8mg/l).
Colonies fluoresce under long wave UV light.
Alcohol (1 : 1 ratio) or heat (75˚c 20 mins) can be used to select for spores as an alternative isolation procedure.
CONTROL / PREVENTION
1. Limit antimicrobial use
2. Good infection control
- Hand washing
- Enteric precautions
- Clean environment
Decontamination must remove spores
Decontamination
Hospital Surfaces: Routine cleaning
Equipment: 2% alkaline buffered glutaraldehyde
TREATMENT OF CASES (Conventional)
Stop the precipitating antibiotics (15-25% success)
Vancomycin 125mg qds 7-10 days
OR
Metronidazole 400mg tds 7-10 days
TREATMENT OF CASES (Unconventional)
1. Faecal enemas / faecal flora cocktails
2. Probiotics
- lactobacilli- Saccharomyces boulardii
3. Non-toxigenic C. difficile