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Unformatted text preview: Anaerobic Bacteria Category
rod, Gram (+)--Clostridium
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Sporerod, Gram (+)--- Clostridium
Rod, Gram (+)
Bifidobacterium Rod, Gram (-) Bacteroides
Cocci, Gram (+) Peptococcus
Cocci, Gram (-) Lactobacillus
Veillonella Clostridium Species
Clostridium 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
Clostridium Pathogenesis of tetanus caused by C tetani General introduction
General 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
BIOCHEMICAL 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
Pathogenicity No invasiveness; toxemia (exogenous infection 丙
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 丙 a few days to several weeks
The two animal species most susceptible to this toxemia are horses and humans. Clostridium tetani -Tetanospasmin
Clostridium disseminates systemically binds to ganglioside receptors • inhibitory neurones in CNS
glycine • neurotransmitter
stops nerve impulse to muscles spastic paralysis 丙丙丙丙丙
severe muscle contractions and spasms can be fatal Tetanospasmin
Tetanospasmin Clinical Manifestations
Clinical 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 丙丙丙丙 (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 Generalized CLINCAL MANIFESTATIONSA 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
Neonatal Involvement of muscles in area of primary injury; infection may precede generalized disease; favorable prognosis
Generalized disease in neonates; infection typically originates from umbilical 丙丙 stump;very poor prognosis in infants whose mothers are nonimmune Epidemiology
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 onehalf 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
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 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 onethird 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
Vaccination • infant
• DPT (diptheria, pertussis, tetanus)
• tetanus toxoid
– no exotoxic activity
Control The offending organism must be removed by local debridemen 丙丙丙
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 α
τ Types of Toxins
A B C D E lecithinase; increase the vascular permeability; + + + + + Necrotizing activity, induces hypertension by － + + 丙 丙 － － － + 丙 丙 丙 丙 丙 + hemolytic; produces necrotizing activity causing release of catecholamines.
increase the permeability of gastrointestinal wall
Necrotizing activity; increase the vascular permeability Toxins
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
Enterotoxin Many strains of type A produce enterotoxin, which is a heatlabile protein and destroyed immediately at 100 ℃.
Trypsin treatment enhances the toxin activity threefold.
The toxin is produced primarily by typeA 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
Organism Without treatment death
occurs within 2 days
occurs effective antibiotic therapy
amputation & death is rare Gas gangrene
Gas Gas gangrene is a lifethreatening disease with a poor prognosis and often fatal outcome. Initial trauma to host tissue damages muscle and impairs blood supplylack 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
Gas 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
Food 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
Food more than 108 vegetative cells are ingested and sporulate in the gut, the toxins can act rapidly in the body, causing severe diarrhea in 618 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, 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
Betatoxinproducing C. perfringens type C Septicemia Who is at risk?
Who Surgical patients; patient after trauma with soil contamination.
People who ingest contaminated meat products (without proper refrigeration or reheating to inactivate endotoxin) Epidemiology
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
Epidemiology Type A: gas gangrene, soft tissue infections and food poisoning
Type C: enteritis; necroticans Laboratory identification
• lecithinase production
lecithinase Double Hemolysis Circles C. botulinum
C. Biological Features
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.
eating uncooked foods
---GI, duodenum, blood stream,
neuromuscular synapses. Virulence factors
Virulence ---bacterial protease
---light chain,A,50 kDa;
---A potent toxin binds peripheral nerve receptors
• acetylcholine neurotransmitter
inhibits nerve impulses flaccid paralysis
• respiratory • cardiac failure toxin Botulinum toxin
• 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.
---internationally recognized. Clinical syndromes
---weakness, dizziness,dryness of the mouth.
---Neurologic features: blurred vision,
inability to swallow, difficulty in speech,
descending weakness of skeletal muscles,
respiratory paralysis. Botulism( －－－－ )
Botulism food poisoning • rare
germination of spore inadequately sterilized canned food • home not an infection Infection with C. botulinum
C. 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
--- most direct and effective: serum or
---most sensitive and widely used:
mouse neutralization test. 48h.
Culturing of specimens 5-7d. Treatment
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. proper food handling and preparation. spores survive boiling (100 degrees at 1 atm) 1h. toxin heatlabile, boiling or intense heating, inactivate the toxin. bulge, gas, spoiled. C. difficile
• After antibiotic use
Intestinal normal flora --greatly decreased
Pseudomembanous Pseudomembranous Colitis
Pseudomembranous 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 2744%. Therapy
Therapy Discontinuation of initial antibiotic (e.g. ampicillin)
Specific antibiotic therapy (e.g. vancomycin) Obligate (strict) anaerobes
• no oxidative phosphorylation
killed by oxygen
lack certain enzymes
– superoxide dismutase
* O2-+2H+ H2O2
* H2O2 H20 + O2
* H2O2 H20 /NAD to NADH
/NAD Strict anaerobe infectious
disease Sites throughout body Muscle, cutaneous/subcutaneous necrosis
Abscesses Bacterial Flora of the Body
Site Total Bacteria
(per/ml or gm) Upper Airway
Tooth Surface 10101011
10111012 Gastrointestinal Tract
10111012 Female Genital Tract
108109 Ratio Anaerobes:Aerobes
35:1 Problems in identification of
• air in sample (sampling, transportation)
– no growth
• identification takes several days or longer
– limiting usefulness
• often derived from normal flora
– sample contamination can confuse
sample Virulence Factors
1. 1. 1. 1. Antiphagocytic capsule • Also promote abscess formation • B. fragilis produces variety of enzymes (lipases, proteases, collagenases) that destroy tissue Abscess Formation Tissue destructive enzymes Betalactamase production • B. fragilis – protect themselves and other species in mixed infections 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 •
1. Originate from our own flora • Breeches in the mucocutaneous barrier displace normal flora
Compromised vascular supply
Trauma with tissue destruction
Antecedent infection Predisposing Conditions •
• Characteristics of Anaerobic
3. Complex Flora Multiple species • Abdominal Infection Avg of 5 species Those predominant in stool are not infecting species • Veillonella, Bifidobacterium rarely pathogenic • Species uniquely suited to cause infection predominate Allow growth of anaerobes
Anaerobes promote growth of other bacteria by being antiphagocytic and producing Blactamases • 3 anaerobic
2 aerobic • Less complex then nl flora
• Fecal flora 400 different species 4. Synergistic Mixture of Aerobes & Anaerobes E. coli Consume O2 Clues to Anaerobic Infection
Infections in continuity to mucosal surfaces
Infections with tissue necrosis and abscess formation Putrid odor
Gas in tissues
Failure to grow in the lab 1.
6. BIOCHEMICAL KITS • e.g. API SYSTEM • volatile fermentation products GAS CHROMATOGRAPHY Bacteroides fragilis
• Major disease causing strict anaerobic
Major after abdominal surgery non-spore-former
• Prominent capsule
– abscess formation
– 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
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- Fall '11