1. Chapter 18 Anaerobic bacteria

2. Classification spore-forming anaerobes Clostridium --G+
exogenous infection --pathgen
non-spore-forming anaerobes
G+, G- cocci, bacilli
endogenous infection—opportunistic infection

3. Content Clostridium C. tetani C. botulinum C. perfringens C. difficile
Non-spore-forming anaerobes

4. I. Clostridium General characteristics
gram-positive, spore-forming bacilli
Distributed in soil and intestine of human and animal
obligate anaerobes
motile -- peritrichous flagella
(exception: C. perfringens—nonmotile)
Exotoxin--- typical clinical symptoms

5. I. Clostridium
C. tetani
C. botulinum
C. perfringens
C. difficile

6. C. tetani

7. C. tetani--Characteristics
anaerobic gram-positive rod that forms terminal spores—”drumstick”
motile with peritrichous flagella
No capsule
tetanospasmin

8. C. tetani--Pathogenicity
portal of entry: wound
conditions of infection
regional anaerobic environment
deep and narrow wound, contamination of soil or foreign bodies
necrotic tissues
contamination of aerobes or facultative anaerobes

9. C. tetani-- Pathogenicity
Virulence factors
Tetanospasmin
Protein (neurotoxin)
Heat-labile (65℃, 30min) and protease-labile
Toxoid available(artificial active vaccination)
Mechanisms

10. Mechanisms of tetanospasmin
toxin → inhibitory interneuron → blocks the release of neurotransmitters from the presynaptic membrane of inhibitory interneurons, e.g., glycine and γ–aminobutyric acid ( inhibit the motor neuron) → spastic paralysis (rigid paralysis)
excitatory transmitter: acetylcholine
inhibitory transmitter: glycine and γ–aminobutyric acid

11. Mechanisms of tetanospasmin
spastic paralysis (rigid paralysis)

12. C. tetani-- Pathogenicity
Disease-tetanus
latent period: 4-5d ～ several weeks
typical symptoms:
rigid paralysis
Opisthotonos
Lockjaw, sardonic smile
Drooling, sweating, irritability

13. C. tetani-- Pathogenicity
Disease-neonatal tetanus
a frequent cause of death in developing countries
most common causes: cutting the umbilical cord with unsterilized instruments or infection of the umbilical stump
the fatality rate: around 50%
the common death cause: respiratory failure

14. Microbiological test
Typical manifestations and injury history help diagnosis.
Microscopic detection and isolation culture are usually not used .

15. C. tetani-- Immunity Antitoxin immunity
Gained by active or passive immunization

16. C. tetani-- Control for children: basic immunization Prevention
Active immunization: tetanus toxoid
for children: basic immunization
DPT(diphtheria toxoid, pertussis vaccine, tetanus toxoid)
for a high-risk group : toxoid booster

17. C. tetani-- Control Urgent prevention
Proper care of wounds: surgical debridement
Passive immunization: tetanus antitoxin
urgent prevention (along with toxoid)
As soon as possible
Allergic skin test before use

18. C. tetani– treatment
Large dose and early use of TAT because TAT can not neutralize exotoxin that have already bound with receptor on nervous target cell
Special treatment
administration of antibiotics
supportive measures

19. Pathogen of gas gangrene and food poisoning
C. perfringens
Pathogen of gas gangrene and food poisoning

20. C. perfringens --Characteristics
Shape and structure
Large G+ rods
Subterminal endospore
Capsule
Nonmotile

21. C. perfringens --Characteristics
Cultivation
strict anaerobic
double zones of hemolysis
generation time : 8-10 minutes
carbohydrate fermentation---active metabolism
Inner zone: θ toxin
complete
Outer zone: α toxin
Incomplete

22. stormy fermentation

23. C. perfringens --Characteristics
Classification
five toxigenic types (A through E)
A cause most of human infections +
Type
α, Alpha
β, Beta
ε, Epsilon A B C D E
ι, Iota

24. C. perfringens -- Pathogenicity
Virulence factors
αtoxin
produced by all strains
the most potent toxin→
exhibits lecithinase activity→
destroys erythrocytes, leukocytes, and platelets,muscle cells,
endothelial cell

25. Increasing of vascular permeability
Massive hemolysis and bleeding,
tissue necrosis
Dysfunction of heart and liver

26. C. perfringens -- Pathogenicity
Virulence factors
Enterotoxin
produced by types A(most), C, and D
heat-labile
Toxin of food poisoning
Others
collagenase, hemolysin, proteinase, DNase (deoxyribonuclease)

27. C. perfringens -- Pathogenicity
Disease
Gas gangrene
Occurrence
Transmission: trauma
Pathogens: 60～80％ cases by type A
Conditions: localized anaerobic environment
Manifestation: sudden outset, emphysema, edema(crepitation) necrotic tissues, foul-smelling, toxemia, shock

28. C. perfringens -- Pathogenicity
Disease
Food poisoning
transmission: gastrointestinal tract
pathogens: type A
manifestation: short incubation period (10hrs) cramps and watery diarrhea --- self-limiting

29. Laboratory diagnosis Quick diagnosis and treatment Direct slide smear
Isolation culture
Animal test
Food poisoning diagnosis

30. Prevention and control
Prompt and extensive surgical debridement of involved area and excision of all devitalized tissue
Antibiotics
Polyvalent antitoxin
Hyperbaric oxygen

31. C. Botulinum
pathogen of botulism

32. C. botulinum---Characteristics
Gram positive rod
Subterminal endospore
Noncapsule
Obligate anaerobe

33. Racket shaped

34. C. botulinum--- Pathogenicity
Virulence factor— botulinum toxin
neurotoxin
relatively heat-labile: 100℃, 10min; 80℃, 20min
types: A, B, C, D, E, F, G
the most potent toxic material known
10,000 times
potassium cyanide(KCN)

35. mechanism of action:
Botulinum toxin is absorbed from the gut and binds to receptors of presynaptic membranes of motor neurons
blocking the presynaptic release of the neurotransmitter acetylcholine → lack of muscle contraction and flaccid paralysis

36. Mechanisms of botulinum toxin
flaccid paralysis

37. Sausages, seafood products, sweat bean sauce, and canned food
C. botulinum--- Pathogenicity
Disease—Botulism
Endospore → germinate → toxin → flaccid paralysis
Sausages, seafood products, sweat bean sauce, and canned food
Food poisoning
Infant botulism
Wound botulism
 Ducks displaying the characteristic flaccid paralysis caused by the disease
Honey

38. C. botulinum--- Pathogenicity
Disease
Food poisoning
transmission: ingestion of toxin-contaminated food
manifestation: flaccid paralysis
double vision, blepharoplegia ,dysphagia, difficulty in breathing and speaking
gastrointestinal symptoms are rare
limb muscles rarely involved
cause of death: respiratory failure

39. C. botulinum--- Pathogenicity
Disease
infant botulism
transmission: ingestion of organism-contaminated food(honey)
manifestation: constipation, poor feeding, difficulty in sucking and swallowing, weak cry, loss of head control--- Floppy baby
prevention: free of honey under 1 year old

40. C. botulinum--- Pathogenicity
Disease
wound botulism
Rare
Transmission: trauma

41. Control and treatment
Destroy the spores in food,preventing spore germination or destroy toxin.
Patients with botulism require adequate ventilatory support
Trivalent botulinum antitoxin(A,B,E)

42. C. difficile

43. C. difficile --- Pathogenicity
Virulence factor
exotoxin A: enterotoxin
exotoxin B: cytotoxin
Disease
pseudomembranous colitis: dysbacteriosis
antibiotic-associated diarrhea

44. C. difficile --- Control
Treatment
discontinuation of causative antibiotics
administration of sensitive antibiotics
Prevention
no vaccine
use antibiotics only in necessary

45. non-spore-forming anaerobes

46. Characteristics include both G+ and G- bacilli and cocci.
members of the normal flora
cause: endogenous infection
23 genera and 10 genera pathogenic to human

47. Conditions causing disease
Change of habitat
Decrease of host defense
Dysbacteriosis
Local anaerobic environment formation

48. Characteristics of infections
endogenous infection throughout body, most chronic
nonspecific manifestations, most pyogenic
local abscess ,tissue necrosis, septicemia
foul-smelling discharge, sometimes gas formation
direct smear positive, aerobic culture negative
have no response to some antibiotics such as aminoglycisides

49. Diseases septicemia infections in central nervous system dental sepsis
pulmonary infections
intraabdominal infections
infections of the female genital tract

50. Question
1. Make a list of the major pathogenic Clostridial species, indicating the virulence factors and diseases they cause.
2. What are the principle of treatment and prevention for the infection by C.tetani?
3. Make a list of conditions in which can cause disease infected by non-spore-forming anaerobes.
4. What affect do tetanospasmin and botulinum toxin have on muscles?
5. Choose the best answer
1) the primary toxin associated with invasive C.perfringens infection is
a. neuraminidase b. alpha toxin c. hyaluronidase d. coagulase
2) a neurotoxin that causes flaccid paralysis is
a. tetanospasmin b. botulinum toxin c. αtoxin d. enterotoxin

51. occurrence development of anaerobic environments (e.g., deep wound)
spores → vegetative cells → toxins and invasive enzymes ↓
tissue destruction and necrosis;
carbohydrate fermentation and gas (H2; ,CO2) formation
and accumulation in the tissue
restrict the blood supply (flow)
increases the tissue necrosis