Transcript C tetani

Anaerobic Bacteria
Category
• Spore-forming:
rod, Gram (+)--- Clostridium
• Nonspore-forming:
see next slides
Category
Spore-forming: rod, Gram (+)--- Clostridium
Nonspore-forming:
Rod, Gram (+)
Propionibacterium丙酸菌属
Rod, Gram (-)
Cocci, Gram (+)
Cocci, Gram (-)
Bifidobacterium
Lactobacillus
Eubacterium
Actinomyces
Bacteroides
Fusobacterium梭菌属
Campylobacter
Peptococcus
Peptostreptococcus
Veillonella
Clostridium Species
• The clostridia are opportunistic pathogens.
Nonetheless, they are responsible for some of
the deadliest diseases including gas gangrene,
tetanus and botulism. Less life-threatening
diseases include pseudomembranous colitis
(PC) and food poisoning.
• cause disease primarily through the production
of numerous exotoxins.
• perfringens, tetani, botulinum, difficile
Clostridium Tetani
Pathogenesis of tetanus caused by C tetani
General introduction
• C tetani is found worldwide. Ubiquitous in
soil, it is occasionally found in intestinal
flora of humans and animals
• C.tetani is the cause of tetanus,or lockjaw.
When spores are introduced into wounds
by contaminated soil or foreign objects
such as nails or glass splinters
BIOCHEMICAL CHARACTERISTICS
• Morphology: long and slender;
peritrichous flagella,no capsule,
terminal located round spore(drumstick apperance), its diameter
greater than vegetative cell.
• Culture:obligate anaerobic; Gram(+);
swarming occures on blood agar, faint
hemolysis.
• Biochemical activities:does not
ferment any carbohydrate and
proteins.
• Resistance: tolerate boiling for 60
min.alive several ten years in soil.
• Classification and Antigenic Types:
C tetani is the only species. There are
no serotypes
2-5 x 0.3-0.5um
Pathogenicity
• No invasiveness; toxemia
retrograde transport to
(exogenous infection）
(CNS)
• produces two exotoxins:
delitescence：a few
tetanolysin, (unknown)and
tetanospasmin(a kind of
days to several weeks
neurotoxin, toxicity strong)
The two animal species
• The actions of
most susceptible to this
tetanospasmin are complex
and involve three components
toxemia are horses and
of the nervous system: central
humans.
motor control, autonomic
function, and the
neuromuscular junction.
Clostridium tetani -Tetanospasmin
• disseminates systemically
• binds to ganglioside receptors
– inhibitory neurones in CNS
• glycine
– neurotransmitter
• stops nerve impulse to muscles
• spastic paralysis痉挛性麻痹
• severe muscle contractions and spasms
• can be fatal
Tetanospasmin
Clinical Manifestations
• The initial symptom is cramping and twitching of
muscles around a wound. The patient usually has no
fever but sweats profusely and begins to experience
pain, especially in the area of the wound and around
the neck and jaw muscles (trismus).
• Portions of the body may become extremely rigid,
and opisthotonos角弓反张(a spasm in which the
head and heels are bent backward and the body
bowed forward) is common.
• Complications include fractures, bowel impaction,
intramuscular hematoma, muscle ruptures, and
pulmonary, renal, and cardiac problems
Clinical Manifestations
DISEASE
CLINCAL MANIFESTATIONSA
Generalized
Involvement of bulbar and paraspinal muscles(trismus
or lockjaw, risus sardonicus, difficulty swallowing,
irritability, opisthotonos);involvement of autonomic
nervous system(sweating, hyper thermia, cardiac
arrhythmias, fluctuations in blood pressure)
Cephalic
Primary infection in head,particularly ear;isolated or
combined involvement of cranial nerves, particularly
seventh cranial nerve; very poor prognosis
Localized
Involvement of muscles in area of primary injury;
infection may precede generalized disease; favorable
prognosis
Neonatal
Generalized disease in neonates; infection typically
originates from umbilical脐带stump;very poor prognosis
in infants whose mothers are nonimmune
Tetanus.
Epidemiology
• 1 million cases of tetanus occur annually in the
world,with a mortality rate ranging from20% to 50%.
But rare in most developed countries.
• In some developing countries, tetanus is still one of the
ten leading causes of death, and neonatal tetanus
accounts for approximately one-half of the cases
worldwide.
• In less developed countries, approximate mortality
rates remain 85% for neonatal tetanus and 50% for
nonneonatal tetanus.
• In the United States, intravenous drug abusers have
become another population with an increasing
incidence of clinical tetanus
• In untreated tetanus, the fatality rate is 90% for the
newborn and 40% for adults.
Immunity
• Humoral immunity(antitoxin)
• There is little, if any, inate immunity and the
disease does not produce immunity in the
patient.
• Active immunity follows vaccination with
tetanus toxoid
Diagnosis
• Diagnosis is primarily by the clinical symptoms
(above). The wound may not be obvious.
• C tetani can be recovered from the wound in
only about one-third of the cases.
• It is important for the clinician to be aware that
toxigenic strains of C tetani can grow actively
in the wound of an immunized person.
• Numerous syndromes, including rabies and
meningitis, have symptoms similar to those of
tetanus and must be considered in the
differential diagnosis.
Vaccination
• infant
• DPT (diptheria, pertussis, tetanus)
• tetanus toxoid
– antigenic
– no exotoxic activity
Control
• The offending organism must be removed by
local debridemen清创术
• toxoid
• TAT; Metronidazole (For more serious
wounds)
• Because of their immunodeficiency state,
AIDS patients may not respond to
prophylactic injections of tetanus toxoid
C. perfringens
• soil, fecal contamination
• gas gangrene
– swelling of tissues
– gas release
* fermentation products
• wound contamination
Toxins
toxin
Biological Feature
Types of Toxins
A
B
C
D
E

lecithinase; increase the
vascular permeability; hemolytic;
produces necrotizing activity
+
+
+
+
+

Necrotizing activity,
induces hypertension by
causing release of
catecholamines.
－
+
+
－
－

increase the permeability
of gastrointestinal wall
－
－
－
+
－

Necrotizing activity;
increase the vascular
permeability
－
－
－
－
+
Toxins
• Many of these toxins have lethal, necrotizing,
and hemolytic properties;
• The alpha toxin produced by all types of C.
perfringens, is a lecithinase that lyses
erythrocytes, platelets, leukocytes, and
endothelial cells. And its lethal action is
proportionate to the rate at which it splits
lecithin to phosphorylcholine and diglyceride.
• The theta toxin has similar hemolytic and
necrotizing effects.
• DNAase, hyaluronidase, a collagenase are
also produced
Enterotoxin
• Many strains of type A produce enterotoxin,
which is a heat-labile protein and destroyed
immediately at 100 ℃.
• Trypsin treatment enhances the toxin activity
threefold.
• The toxin is produced primarily by type A
strains but also by a few type C and D strains.
• It disrupts ion transport in the ileum(primarily)
and jejunum by inserting into the cell
membrane and altering membrane
permeability.
• As superantigen.
Pathogenesis
• Tissue degrading enzymes
– lecithinase [ toxin]
– proteolytic enzymes
– saccharolytic enzymes
• Destruction of blood vessels
• Tissue necrosis
• Anaerobic environment created
• Organism spreads
Without treatment death
occurs within 2 days




effective antibiotic therapy
debridement
anti-toxin
amputation & death is rare
Gas gangrene
• Gas gangrene is a life-threatening disease with a poor
prognosis and often fatal outcome.
• Initial trauma to host tissue damages muscle and impairs
blood supply----lack of oxygenation
• Initial symptoms : fever and pain in the infected tissue.;
more local tissue necrosis and systemic toxemia.
Infected muscle is discolored (purple mottling) and
edematous and produces a foul-smelling exudate; gas
bubbles form from the products of anaerobic
fermentation.
Gas gangrene
• As capillary permeability increases, the
accumulation of fluid increases, and
venous return eventually is curtailed.
• As more tissue becomes involved, the
clostridia multiply within the increasing
area of dead tissue, releasing more toxins
into the local tissue and the systemic
circulation.
Food poisoning
• Enterotoxin producing strains.
• These bacteria are found in mammalian
faeces and soil.
• Small numbers of the bacteria may also be
found in foods and they may propagate
rapidly to dangerous concentrations if the
food is improperly stored and handled.
Food poisoning
• more than 108 vegetative cells are ingested
and sporulate in the gut, the toxins can act
rapidly in the body, causing severe diarrhea in
6-18 hours, dysentery, gangrene, muscle
infections
• The action of C. perfringens enterotoxin
involves marked hypersecretion in the
jejunum and ileum, with loss of fluids and
electrolytes in diarrhea.
Cellulitis, Fasciitis
• Cellulitis, Fasciitis
• Fasciitis : a rapidly progressive, destructive
process in which the organisms spread through
fascial plan es.
• Fasciitis causes suppuration and the formation
of gas
• Absense of muscle involvement
• rapidity
• Necrotizing Enteritis
• Rare, acute necrotizing process in the jejunum
• Abdominal pain, bloody diarrhea, shock, and
peritonitis
• Mortality: 50%
• Beta-toxin-producing C. perfringens type C
• Septicemia
Who is at risk?
• Surgical patients; patient after trauma with
soil contamination.
• People who ingest contaminated meat
products (without proper refrigeration or
reheating to inactivate endotoxin)
Epidemiology
• C. perfringens type A: the intestinal tract of
humans and animals, soil and water
contaminated with feces. forms spores
under adverse environmental conditions
and can survive for prolonged periods.
• Type B to E strains colonize the intestinal
tract of animals and occasionally humans.
Epidemiology
• Type A: gas gangrene, soft tissue
infections and food poisoning
• Type C: enteritis; necroticans
Laboratory identification
• lecithinase production
Double Hemolysis Circles
C. botulinum
Biological Features
•
•
•
•
•
•
Anaerobic
Gram-positive
rod-shaped
sporeformer
produces a protein neurotoxic.
soil, sediments of lakes, ponds, decaying
vegetation.
• intestinal tracts of birds, mammals and
fish.
Division
---A, B, C1, D, E, F, and G.
---type A. 62%
---Not all produce toxin.
---C and D not
---G plasmid encoded.
Transmission
---spores heat resistant.
canning.
anaerobic environment
---Botulism
eating uncooked foods
spores
---GI, duodenum, blood stream,
neuromuscular synapses.
Virulence factors
---bacterial protease
---light chain,A,50 kDa;
heavy chain,100kDa.
---disulfide bond.
---A potent toxin
• binds peripheral nerve receptors
– acetylcholine neurotransmitter
• inhibits nerve impulses
• flaccid paralysis
• death
Botulinum
– respiratory
– cardiac failure
toxin
Botulinum toxin
• Bioterrorism
– not an infection
– resembles a chemical attack
– 10 ng can kill a normal adult
Epidemiology
---4: foodborne, infant, wound, undetermined.
---Certain foods; wound not.
---Foodborne botulism, consumption.
---Infant botulism, 1976, under 12m.
---ingestion, colonize and produce toxin in the
intestinal tract of infants.
honey.
---increased.
---internationally recognized.
Clinical syndromes
---18-36 hours:
---weakness, dizziness,dryness of the mouth.
---Nausea,vomiting.
---Neurologic features: blurred vision,
inability to swallow, difficulty in speech,
descending weakness of skeletal muscles,
respiratory paralysis.
Botulism(肉毒中毒)
• food poisoning
– rare
– fatal
• germination of spore
• inadequately sterilized canned food
– home
• not an infection
Infection with C. botulinum
• Neonatal botulism
– uncommon
– the predominant form of botulism
– colonization occurs
• no normal flora to compete
• unlike adult
Wounds
– extremely rare
– an infection
Immunity
---specifically neutralized, antitoxin.
---toxoided, make good antigens.
---does not develop, amount toxic.
---Repeated occurrence.
---Once bound, unaffected by antitoxin.
---circulating toxin ,neutralized , injection of
antitoxin.
---treated immediately with antiserum.
---multivalent
toxoid,unjustified,infrequency.
experimental vaccine.
Diagnosis
---by clinical symptoms alone
---differentiation difficult.
--- most direct and effective: serum or
feces.
---most sensitive and widely used:
mouse neutralization test. 48h.
Culturing of specimens 5-7d.
Treatment
• Individuals known to have ingested food with
botulism should be treated immediately with
antiserum.
• antibiotic therapy (if infection)
• Vaccination will not protect hosts from
botulism, however passive immunisation
with antibody is the treatment of choice for
cases of botulism.
Prevention
---proper food handling and preparation.
--- spores survive boiling (100 degrees at 1 atm)
1h.
---toxin heat-labile, boiling or intense heating,
inactivate the toxin.
---bulge, gas, spoiled.
C. difficile
•
•
•
•
•
After antibiotic use
Intestinal normal flora --greatly decreased
Colonization occurs
Enterotoxin secreted
Pseudomembanous colitis
Pseudomembranous Colitis
• Pseudomembranous colitis (PC) results
predominantly as a consequence of the
elimination of normal intestinal flora through
antibiotic therapy.
• Symptoms include abdominal pain with a
watery diarrhea and leukocytosis.
"Pseudomembranes" consisting of fibrin,
mucus and leukocytes can be observed by
colonoscopy.
• Untreated pseudomembranous colitis can be
fatal in about 27-44%.
Therapy
• Discontinuation of initial antibiotic (e.g.
ampicillin)
• Specific antibiotic therapy (e.g. vancomycin)
Obligate (strict)
anaerobes
•
•
•
•
no oxidative phosphorylation
fermentation
killed by oxygen
lack certain enzymes
– superoxide dismutase
* O2-+2H+ H2O2
– catalase
* H2O2 H20 + O2
– peroxidase
* H2O2 H20 /NAD to NADH
Strict anaerobe infectious
disease
•
•
•
Sites throughout body
Muscle, cutaneous/sub-cutaneous necrosis
Abscesses
Bacterial Flora of the Body
Site
Total Bacteria
(per/ml or gm)
Upper Airway
Nasal Washings
103-104
Saliva
108-109
Tooth Surface 1010-1011
1:1
Gingival Crevice
1011-1012
Gastrointestinal Tract
Stomach
102-105
Small Bowel
102-104
Ileum
104-107
Colon
1011-1012
Female Genital Tract
Endocervix
Vagina
108-109
108-109
Ratio
Anaerobes:Aerobes
3-5:1
1:1
1000:1
1:1
1:1
1:1
1000:1
3-5:1
3-5:1
Problems in identification of
anaerobic infections
• air in sample (sampling, transportation)
– no growth
• identification takes several days or longer
– limiting usefulness
• often derived from normal flora
– sample contamination can confuse
Virulence Factors
1. Anti-phagocytic capsule
•
Also promote abscess formation
2. Tissue destructive enzymes
•
B. fragilis produces variety of enzymes (lipases,
proteases, collagenases) that destroy tissue 
Abscess Formation
3. Beta-lactamase production
•
B. fragilis – protect themselves and other species
in mixed infections
4. Superoxide dismutase production
•
Protects bacteria from toxic O2 radicals as they
move out of usual niche
Characteristics of Anaerobic
Infections
1. Most pathogenic anaerobes are usually
commensals
•
Originate from our own flora
2. Predisposing Conditions
– Breeches in the mucocutaneous barrier
•  displace normal flora
– Compromised vascular supply
– Trauma with tissue destruction
– Antecedent infection
Characteristics of Anaerobic
Infections
3. Complex Flora
4. Synergistic Mixture of
• Multiple species
Aerobes & Anaerobes
– Abdominal Infection  Avg of 5 •
E. coli  Consume O2
species
– Allow growth of
• 3 anaerobic
• 2 aerobic
anaerobes
– Less complex then nl flora
• Anaerobes  promote
– Fecal flora 400 different
growth of other bacteria by
species
being antiphagocytic and
• Those predominant in stool
are not infecting species
producing B-lactamases
– Veillonella, Bifidobacterium
 rarely pathogenic
– Species uniquely suited to
cause infection predominate
Clues to Anaerobic Infection
1.
2.
Infections in continuity to mucosal surfaces
Infections with tissue necrosis and abscess
formation
Putrid odor
Gas in tissues
Polymicrobial flora
Failure to grow in the lab
3.
4.
5.
6.
BIOCHEMICAL KITS
–
e.g. API SYSTEM
GAS CHROMATOGRAPHY
–
volatile fermentation products
Bacteroides fragilis
• Major disease causing strict anaerobic
after abdominal surgery
non-spore-former
• Prominent capsule
– anti-phagocytic
– abscess formation
• Endotoxin
– low toxicity
– structure different than other
lipolysaccharide
• Enterobacteriaceae (facultative anaerobes)
– commonly cause disease
– low numbers gut flora
• Strict anaerobes
– much less commonly cause disease
– high numbers gut flora
.