1. Anaerobic bacteria
1

2. Classification
• spore-forming anaerobes
Clostridium
G+
• non-spore-forming anaerobes
G+, G-
cocci, bacilli
2

3. Section Ⅰ Clostridium
3

4. General characteristics
• gram-positive, spore-forming bacilli
• obligate anaerobes
• motile -- peritrichous flagella
(exception: C. perfringens—nonmotile)
• the sporangia– swollen
• typical clinical symptoms
4

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

6. C. tetani
6

7. 7

8. Characteristics
• anaerobic gram-
positive rod that forms
terminal spores
• motile with peritrichous
flagella
• tetanospasmin
8

9. 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

10. Pathogenicity
• Virulence factors
– Tetanospasmin
• Protein (neurotoxin)
• Heat-labile (65℃, 30min)
• Mechanisms
10

11. Mechanisms of tetanospasmin
toxin → peripheral nerve fibers / lymph and
blood → spinal cord and brain stem →
inhibitory interneuron → blocks the release of
neurotransmitters from the presynaptic
membrane of inhibitory interneurons→ inhibit
the motor neuron → spastic paralysis (rigid
paralysis)
麻痹性痉挛
excitatory transmitter: acetylcholine
inhibitory transmitter: glycine and γ–aminobutyric acid
11

12. Mechanisms of tetanospasmin
spastic paralysis (rigid paralysis)
12

13. Pathogenicity
• Disease-tetanus(neonatal tetanus)
latent period: 4-5d ～ several weeks
typical symptoms:
Opisthotonos
13
Lockjaw, sardonic smile

14. 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 90%
– the common death cause:
respiratory failure 14

15. Immunity
• Antitoxin immunity
• Weak
potent exotoxin
rapid combination with target cells
• Toxoid vaccine
15

16. Control
• Proper care of wounds: surgical debridement
• Active immunization: tetanus toxoid
for children: basic immunization: DPT(diphtheria toxoid,
pertussis vaccine, tetanus toxoid)
for a high-risk group : toxoid booster
• Passive immunization: tetanus antitoxin
urgent prevention (along with toxoid)
As soon as possible
• Special treatment
– administration of antibiotics
– supportive measures 16

17. C. perfringens
17

18. Characteristics
• Shape and structure
– Subterminal endospore
– Capsule
– Nonmotile
18

19. Characteristics
• Classification
– five toxigenic types (A through E)
– αtoxin: the most potent toxin→exhibits lecithinase
activity→destroys erythrocytes, leukocytes, and
platelets→ hemolysis, tissue necrosis
Type α, Alpha β, Beta ε, Epsilon ι, Iota
A +
B + + +
C + +
D + +
E + + 19

20. Characteristics
• Cultivation
anaerobic
double zones of hemolysis
carbohydrate fermentation (lactose)
Inner zone: θ toxin
complete
Outer zone: α toxin
Incomplete
Stormy
20
fermentation

21. Pathogenicity
• Virulence factors
– α toxin
• produced by all strains
• acts as a lecithinase
• diagnosis: Nagler reaction--egg yolk agar
21

22. Pathogenicity
• Virulence factors
– Enterotoxin
• produced by types A(most), C, and D
• heat-labile
– Others
• collagenase, hemolysin, proteinase, DNase
(deoxyribonuclease)
22

23. Pathogenicity
• Disease
– Gas gangrene
• Occurrence
• Transmission: trauma
• Pathogens: 60 ～ 80 ％ cases
by type A
• Manifestation: sudden outset,
emphysema, edema, necrotic
tissues, foul-smelling, toxemia,
shock
23

24. Pathogenicity
• Disease
– Food poisoning
• transmission: gastrointestinal tract
• pathogens: type A
• manifestation: short incubation period (10hrs)
diarrhea
self-limiting
– Necrotizing enteritis
• pathogens: type C
• highly fatal in children 24

25. Control
• Care of trauma: debridement
• Antimicrobial therapy
• Antitoxin
• Hyperbaric oxygen
• Symptomatic care for food poisoning
25

26. C. botulinum
26

27. Characteristics
• Gram positive rod
• Subterminal
endospore
• Noncapsule
• Obligate anaerobe
27

28. Pathogenicity
• Virulence factor—botulinum toxin
– neurotoxin
– relatively heat-labile and resistant to protease
– types: A, B, C, D, E, F, G
– the most potent toxic material known
potassium times
10,000
cyanide(KCN)
mechanism of action
Toxin → gut → blood → cholinergic synapses → block the
release of exciting neurotransmitter, e.g., acetylcholine →
flaccid paralysis 28

29. Mechanisms of botulinum toxin
flaccid paralysis
29

30. Pathogenicity
• Disease—Botulism
– from Latin botulus, "sausage"
Sausages, seafood
products, milk, and
 Food poisoning canned vegetables
 Infant botulism
Honey
 Wound botulism
30

31. Pathogenicity
• Disease
– Food poisoning
• manifestation:
flaccid paralysis: double vision, dysphagia,
difficulty in breathing and speaking
rare gastrointestinal symptoms
cause of death: respiratory failure
31

32. Pathogenicity
• Disease
– infant botulism
• manifestation: constipation, poor feeding,
difficulty in sucking and swallowing, weak
cry, loss of head control.
Floppy baby
• prevention: free of honey
32

33. Pathogenicity
• Disease
– wound botulism
• Rare
• Transmission: trauma
33

34. Medicine
Blepharospasm
34

35. C. difficile
35

36. Pathogenicity
• Virulence factor
exotoxin A: enterotoxin
exotoxin B: cytotoxin
• Disease
pseudomembranous colitis
antibiotic-associated diarrhea
36

37. Control
• Treatment
discontinuation of causative antibiotics
administration of sensitive antibiotics
• Prevention
no vaccine
use antibiotics only in necessary
37

38. non-spore-forming
anaerobes
38

39. Characteristics
• include both G+ and G- bacilli and cocci.
• members of the normal flora
• cause: endogenous infection
39

40. Non-spore forming anaerobes
G am negat i ve
r G am posi t i ve
r
Baci l l us C occus Baci l l us C occus
Bact er i odes Vei l l onel l a Pr opi oni bact er i um Pept ost r ept ococus
Pr evot el l a Bi f i dobact er i um
Por phyr omonas Eubact er i um
Fusobact er i um Act i nomyces
40

41. Conditions causing disease
• Change of habitat
• Decrease of host defense
• Dysbacteriosis
• Local anaerobic environment formation
41

42. Characteristics of infections
• endogenous infection throughout body, most chronic
• nonspecific manifestations, most pyogenic
• foul-smelling discharge, sometimes gas formation
• direct smear positive, aerobic culture negative
• have no response to some antibiotics such as
aminoglycisides
42

43. Diseases
• septicemia
• infections in central nervous
system
• dental sepsis
• pulmonary infections
• intraabdominal infections
• infections of the female genital
tract
43

44. occurrence
development of anaerobic environments (e.g., deep
wound)
spores → vegetative cells
↓
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
44