MICROBIOLOGY PPT LECTURE NOTES | Karya Tulis Ilmiah
Anaerobic Bacteria
Category
Spore-forming:
rod, Gram (+)--- Clostridium
Nonspore-forming:
see next slides
Category
Sporerod, Gram (+)--- Clostridium
forming:
Nonspore-forming:
Propionibacterium 丙酸菌属
Bifidobacterium
Lactobacillus
Eubacterium
Actinomyces
Rod, Gram (-) Bacteroides
Fusobacterium 梭菌属
Campylobacter
Rod, Gram (+)
Cocci, Gram (+) Peptococcus
Cocci, Gram (-)
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 lifethreatening 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(drum-stick 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
(exogenous infection ）
produces two exotoxins:
tetanolysin, and
tetanospasmin(a kind of
neurotoxin, toxicity strong)
The actions of
tetanospasmin are
complex and involve three
components of the
nervous system: central
motor control, autonomic
function, and the
neuromuscular junction.
retrograde transport
to (CNS)
delitescence ： a few
days to several
weeks
The two animal
species most
susceptible to this
toxemia are horses
and humans.
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
crania
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
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)
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
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
Types of Toxins
A
B
C
D
E
－
+
+
－
－
－
－
－
+
－
+
－
+
－
+
－
+
－
+
+
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 foulsmelling 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
Upper Airway
Nasal Washings
Saliva
Tooth Surface
Gingival Crevice
Gastrointestinal Tract
Stomach
Small Bowel
Ileum
Colon
Female Genital Tract
Endocervix
Vagina
Total Bacteria
Ratio
(per/ml or gm) Anaerobes:Aerobes
103-104
108-109
1010-1011
1011-1012
3-5:1
1:1
1:1
1000:1
102-105
102-104
104-107
1011-1012
1:1
1:1
1:1
1000:1
108-109
108-109
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
Multiple species
• Abdominal Infection Avg
of 5 species
3 anaerobic
2 aerobic
• Less complex then nl flora
• Fecal flora 400 different
species
Those predominant in stool
are not infecting species
• Veillonella,
Bifidobacterium rarely
pathogenic
• Species uniquely suited to
cause infection
predominate
4. Synergistic Mixture
of Aerobes &
Anaerobes
E. coli Consume O2
• Allow growth
of
anaerobes
Anaerobes promote
growth of other
bacteria by being
antiphagocytic and
producing Blactamases
Clues to Anaerobic Infection
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
1.
2.
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
.
Category
Spore-forming:
rod, Gram (+)--- Clostridium
Nonspore-forming:
see next slides
Category
Sporerod, Gram (+)--- Clostridium
forming:
Nonspore-forming:
Propionibacterium 丙酸菌属
Bifidobacterium
Lactobacillus
Eubacterium
Actinomyces
Rod, Gram (-) Bacteroides
Fusobacterium 梭菌属
Campylobacter
Rod, Gram (+)
Cocci, Gram (+) Peptococcus
Cocci, Gram (-)
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 lifethreatening 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(drum-stick 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
(exogenous infection ）
produces two exotoxins:
tetanolysin, and
tetanospasmin(a kind of
neurotoxin, toxicity strong)
The actions of
tetanospasmin are
complex and involve three
components of the
nervous system: central
motor control, autonomic
function, and the
neuromuscular junction.
retrograde transport
to (CNS)
delitescence ： a few
days to several
weeks
The two animal
species most
susceptible to this
toxemia are horses
and humans.
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
crania
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
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)
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
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
Types of Toxins
A
B
C
D
E
－
+
+
－
－
－
－
－
+
－
+
－
+
－
+
－
+
－
+
+
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 foulsmelling 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
Upper Airway
Nasal Washings
Saliva
Tooth Surface
Gingival Crevice
Gastrointestinal Tract
Stomach
Small Bowel
Ileum
Colon
Female Genital Tract
Endocervix
Vagina
Total Bacteria
Ratio
(per/ml or gm) Anaerobes:Aerobes
103-104
108-109
1010-1011
1011-1012
3-5:1
1:1
1:1
1000:1
102-105
102-104
104-107
1011-1012
1:1
1:1
1:1
1000:1
108-109
108-109
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
Multiple species
• Abdominal Infection Avg
of 5 species
3 anaerobic
2 aerobic
• Less complex then nl flora
• Fecal flora 400 different
species
Those predominant in stool
are not infecting species
• Veillonella,
Bifidobacterium rarely
pathogenic
• Species uniquely suited to
cause infection
predominate
4. Synergistic Mixture
of Aerobes &
Anaerobes
E. coli Consume O2
• Allow growth
of
anaerobes
Anaerobes promote
growth of other
bacteria by being
antiphagocytic and
producing Blactamases
Clues to Anaerobic Infection
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
1.
2.
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
.