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
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
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
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
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
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
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
37. Control
• Treatment
discontinuation of causative antibiotics
administration of sensitive antibiotics
• Prevention
no vaccine
use antibiotics only in necessary
37
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
Notas del editor
Figure Victim of tetanus , a soldier wounded at the battle of Corunna in 1809, is seen in a drawing made by the Scottish surgeon and anatomist Sir Charles Bell and published in 1832 in his book The Anatomy and Philosophy of Expression . The patient's muscles are working against one another, leaving him in a state of spastic paralysis; his jaw is set in the "sardonic smile" of tetanus, or lockjaw.
Ducks displaying the characteristic flaccid paralysis caused by the disease