BACTEROIDES FRAGILES: Gram-Negative Pleomorphic Rod
ANAEROBES
BACTEROIDES FRAGILES: Gram-Negative Pleomorphic Rod
Name-Derivation:
Epidemiology / At Risk: #1 bacteria of normal GI flora. 1010-1011 bacteria / gram
Can survive on skin and mucosa.
At Risk: Immunocompromised
Manifestations: Bugs enter through a compromise in GI-tract. Initial infection is polymicrobic, but as other bugs use up the oxygen, Bacteroides can grow.
Pelvic Inflammatory Disease
Intra-abdominal abscess; peritonitis
Sustained Bacteremia: Not endotoxic, and not transient, but in between.
Processing:
Specimen: Exudate. Will be polymicrobic early on.
Must use anaerobic transport medium.
Stain: Gram-negative rods contain intracytoplasmic vacuoles.
Culture: Blood agar with antibiotics.
Identification:
Strict (Aerotolerant) Anaerobe
Direct-FA on capsule to verify its presence. It is not readily visible in culture.
Gas-Liquid Chromatography of metabolic byproducts. Anaerobes are difficult to culture.
Virulence:
Isobutyric and Succinic Acid: Biochemical byproducts are toxic to Salmonella and Shigella. Thus our normal flora are protective against Salmonella.
Capsule: Allows adhesin to peritoneum.
Antichemotactic and antiphagocytic for PMN's.
Aids to inhibit intracellular killing once the bugs are phagocytosed.
Superoxide Dismutase: makes it aerotolerant
Catalase: induced by hemin, thus produced in the blood.
Enzymes: Hyaluronidase, DNAse, Heparinase contribute to invasiveness.
LPS: Contains Lipid-A, but it is not as toxic as E. Coli endotoxin. Only mild endotoxic effect.
Enterotoxin: Diarrhea. This toxin only carried by a few strains.
beta-Lactamase
Treatment: Abscesses must be surgically drained. Metronidazole.
CLOSTRIDIUM PERFRINGES: Gram-Positive rod, spore-former
Epidemiology / At Risk: Normal flora; found as spores in the GI-tract.
Manifestations:
Food-Poisoning: TYPE-A. Found in meats, gravy.
8-24 hours after meal.
Water diarrhea, no perforation, resolves spontaneously.
No Vomiting. No fever.
Heating doesn't prevent it. It only drives out the oxygen.
Necrotizing Enteritis: TYPE-C. More prevelant in other countries.
Necrotizing invasion of small intestine, leading to necrosis, perforation, and death.
Gas Gangrene (Myonecrosis): TYPE-A. Spreading of initial tissue damage.
Predisposing Factor: Must have trauma with damage to muscle, and reduced bloodflow.
Reduced pH (6.5 or lower) causes autolysis of muscle proteins and release of amino acids ------> spores use them as energy resource and germinate.
Fatal without treatment.
Cellulitis: TYPE-A. Subcutaneous damage without muscle damage. Infection spreads along fascial planes.
Processing:
Specimen: Exudate, blood, feces.
Stain: Plump Gram(+) rods with square ends and a capsule.
No inflammatory cells.
Culture: Egg-Yolk Agar. Lecithin is present to test for Lecithinase activity.
Double-zone of hemolysis: beta-hemolysis on inside, plus hazy zone of partial hemolysis on outside.
Identification:
Strict (Aerotolerant) Anaerobe
SEROTYPING: Based on ability to produce four different exotoxins: alpha, beta, ,
There are types A-E
Type-A is most prevelant in U.S.
Gas-Liquid Chromatography for speciation.
Virulence:
Very fast (10 minute) generation time.
Exotoxins: At least 12 are produced. Some main ones
Alpha Toxin: Lecithinase. Hydrolyzes lecithin and sphingomyelin, to lyse mitochondria, RBC's, and WBC's.
Responsible for the larger zone of incomplete hemolysis.
It's an exotoxin so it can go awayfrom the cell.
Beta Toxin: Cytotoxin, responsible for necrotizing enteritis.
Theta Toxin: Oxygen-labile hemolysin.
Responsible for smaller zone of beta-hemolysis.
Toxic to heart muscle, leading to myocarditis as a cardiac complication (from toxemia)
Invasiveness: Due to extracellular enzymes; proteases, collegenases, DNAses.
Enterotoxin: Only released upon sporulation and lysis of a vegetative cell.
Thus it is not a true exotoxin (only released upon lysis)
Causes watery diarrhea, no dysentery.
Vaccine / Prevention: Clean and debride wounds for prevention.
Treatment: Antibiotics, intermittent hyperbaric oxygen treatment.
CLOSTRIDIUM TETANI: Gram-positive spore-forming rod.
Epidemiology / At Risk: Spores are uniquitous in the soil and introduced through puncture wounds.
Manifestations: Tetanus. A microgram of toxin is sufficient to kill.
Spore Germination:
Once spores introduced, they can lie dormant for years if wound remains well aerated.
As aeration is reduced (such as with age, for example), spores germinate and release exotoxin.
Exotoxin is taken up by nerve cells ------> retrograde transport to post-synaptic dendrites, where the exotoxin exerts its effect.
Generalized Tetanus: Lockjaw. Toxin may ascend to brain and affect respiratory center. ANS involvement and generalized spasms. Death by respiratory arrest. Symptoms:
Dysphagia
Drooling
ANS involvement: sweating, hyperthermia, cardiac arrhythmias.
Localized Tetanus: Localized spasm in area of infection. It may spread to generalized tetanus.
Cephalic Tetanus: Primary infection in head.
Processing:
Specimen: Only a few organisms in the lesions. Diagnosis is clinical -- not by microbiology.
Culture: Swarming Growth in culture. Thin surrounding film and faint beta-hemolysis.
Amplified in cooked hamburger broth. Selected for by heat.
Identification:
Opportunstic Strict Anaerobe
Genus is identified by colony morphology.
Somatic Antigen O: Fortunately there is only one serotype of Antigen-O, so that a vaccine is easy to make and effective.
Virulence:
Tetanospasmin: Heat labile, potent, antigenic exotoxin.
AB-Toxin cleaved in light (A) and heavy (B) fragments by an endogenous protease.
Fragment-B binds to ganglioside receptor of a nerve cell.
Fragment-A is taken up by endocytosis. Acidifcation of the vesicle causes Fragment-A to be release into cytoplasm.
Effect: Fragment-A moves up axon retrograde to the post-synpatic receptor. It blocks release of GABA and Glycerine at the post-synaptic terminal.
This results in unregulated excitatory post-synaptic potentials on nerve terminal, leading to spastic paralysis of skeletal muscle and respiratory arrest.
Vaccine / Prevention:
VACCINE: Given against the O-Antigen in cell wall.
Alum-precipitated toxoid (more immunogenic but can cause hypersensitivity): given to infants and children, and never-before immunized adults.
Children given at age 2, 4, 6, and 15-18 months.
Ammonium-precipiated toxoid: Given as a booster shot every ten years thereafter.
People are usually over-vaccinated for this bug.
ANTITOXIN: Given prophylactically if someone is potentially exposed (has a puncture wound) and has not been vaccinated within 5 years.
Tetanus toxin itself is not inherently immunogenic.
If a documented vaccine has been administered in last 5 years, no antitoxin is necessary.
Treatment: To someone who has never been vaccinated, the antitoxin is given in one arm, and a vaccine is given in the other arm, simultaneously. The two will not intermix if given in separate arms.
CLOSTRIDIUM BOTULINUM: Gram-positive spore forming rod.
Epidemiology / At Risk: Spores are in soils and sediment. Found in foods preserved at home at room temperature; old canned foods or self-canned foods.
Manifestations:
Food-Born Botulism: Usually found in alkaline foods, consumed without heating.
Initial Symptoms: Weakness, diziness, constipation.
Toxin is then absorbed from small intestine into blood and nerve cells.
Terminal Symptoms: Blurred vision, dry mouth, peripheral and respiratory flaccid paralysis. Death.
Infant Botulism: Infant at risk up to 1 year of age. After 1 year, GI ingestion of spores is not a problem.
Cause: Ingestion of spores, usually in unpasteurized honey.
Organisms replicate in GI tract and release toxin. Toxin is not readily absorbed through mucosa, but it can be absorbed if the problem is neglected.
Presents as failure to thrive, but can progress to flaccid paralysis.
Wound Botulism: Rare, similar clinical presentation as food botulism.
Processing:
Specimen: Blood, gastric contents, or food. Feces for children.
Serology: Do an assay for the toxin in the blood.
Stain: On infant feces, will find gram-positive rods.
Culture: Blood agar. Heat to boiling for 10 minutes to induce sporulation.
Smooth colonies, beta-hemolysis.
Identification:
ELISA can be used on culture for detection of toxin.
Oppotunstic Strict Anaerobe
Serotypes:
8 serologic types of toxin: A, B, C1, C2, D, E, F, G. All of them act the same.
Only types A, B, E affect humans.
Virulence:
Botulin Exotoxin: The most potent toxin known to man, i.e. lowest amount required to kill.
Phage-mediated, heat labile toxin. Antigenic. The toxin is released upon cell lysis.
MECHANISM: AB-Toxin. Fragment-A is translocated up neuron and blocks release of Acetylcholine ------> Flaccid Paralysis.
Enzyme resistance: Acid stable. Our bodies actually break down the toxin into fragments that are more toxic.
Host Immune Response: No persistent antibody to the toxin, therefore no lifelong immunity.
Again, the toxin is not inherently immunogenic.
Vaccine / Prevention: Alum-precipitated toxoid, only for lab workers.
PREVENTION: Head food, don't give unpasteurized honey to babies.
Antitoxin is available for types A, B, and E.
Treatment:
Ventilatory Support
Administer antitoxin.
Gastric Lavage to wash out any unabsorbed toxin.
BACTEROIDES FRAGILES: Gram-Negative Pleomorphic Rod
Name-Derivation:
Epidemiology / At Risk: #1 bacteria of normal GI flora. 1010-1011 bacteria / gram
Can survive on skin and mucosa.
At Risk: Immunocompromised
Manifestations: Bugs enter through a compromise in GI-tract. Initial infection is polymicrobic, but as other bugs use up the oxygen, Bacteroides can grow.
Pelvic Inflammatory Disease
Intra-abdominal abscess; peritonitis
Sustained Bacteremia: Not endotoxic, and not transient, but in between.
Processing:
Specimen: Exudate. Will be polymicrobic early on.
Must use anaerobic transport medium.
Stain: Gram-negative rods contain intracytoplasmic vacuoles.
Culture: Blood agar with antibiotics.
Identification:
Strict (Aerotolerant) Anaerobe
Direct-FA on capsule to verify its presence. It is not readily visible in culture.
Gas-Liquid Chromatography of metabolic byproducts. Anaerobes are difficult to culture.
Virulence:
Isobutyric and Succinic Acid: Biochemical byproducts are toxic to Salmonella and Shigella. Thus our normal flora are protective against Salmonella.
Capsule: Allows adhesin to peritoneum.
Antichemotactic and antiphagocytic for PMN's.
Aids to inhibit intracellular killing once the bugs are phagocytosed.
Superoxide Dismutase: makes it aerotolerant
Catalase: induced by hemin, thus produced in the blood.
Enzymes: Hyaluronidase, DNAse, Heparinase contribute to invasiveness.
LPS: Contains Lipid-A, but it is not as toxic as E. Coli endotoxin. Only mild endotoxic effect.
Enterotoxin: Diarrhea. This toxin only carried by a few strains.
beta-Lactamase
Treatment: Abscesses must be surgically drained. Metronidazole.
CLOSTRIDIUM PERFRINGES: Gram-Positive rod, spore-former
Epidemiology / At Risk: Normal flora; found as spores in the GI-tract.
Manifestations:
Food-Poisoning: TYPE-A. Found in meats, gravy.
8-24 hours after meal.
Water diarrhea, no perforation, resolves spontaneously.
No Vomiting. No fever.
Heating doesn't prevent it. It only drives out the oxygen.
Necrotizing Enteritis: TYPE-C. More prevelant in other countries.
Necrotizing invasion of small intestine, leading to necrosis, perforation, and death.
Gas Gangrene (Myonecrosis): TYPE-A. Spreading of initial tissue damage.
Predisposing Factor: Must have trauma with damage to muscle, and reduced bloodflow.
Reduced pH (6.5 or lower) causes autolysis of muscle proteins and release of amino acids ------> spores use them as energy resource and germinate.
Fatal without treatment.
Cellulitis: TYPE-A. Subcutaneous damage without muscle damage. Infection spreads along fascial planes.
Processing:
Specimen: Exudate, blood, feces.
Stain: Plump Gram(+) rods with square ends and a capsule.
No inflammatory cells.
Culture: Egg-Yolk Agar. Lecithin is present to test for Lecithinase activity.
Double-zone of hemolysis: beta-hemolysis on inside, plus hazy zone of partial hemolysis on outside.
Identification:
Strict (Aerotolerant) Anaerobe
SEROTYPING: Based on ability to produce four different exotoxins: alpha, beta, ,
There are types A-E
Type-A is most prevelant in U.S.
Gas-Liquid Chromatography for speciation.
Virulence:
Very fast (10 minute) generation time.
Exotoxins: At least 12 are produced. Some main ones
Alpha Toxin: Lecithinase. Hydrolyzes lecithin and sphingomyelin, to lyse mitochondria, RBC's, and WBC's.
Responsible for the larger zone of incomplete hemolysis.
It's an exotoxin so it can go awayfrom the cell.
Beta Toxin: Cytotoxin, responsible for necrotizing enteritis.
Theta Toxin: Oxygen-labile hemolysin.
Responsible for smaller zone of beta-hemolysis.
Toxic to heart muscle, leading to myocarditis as a cardiac complication (from toxemia)
Invasiveness: Due to extracellular enzymes; proteases, collegenases, DNAses.
Enterotoxin: Only released upon sporulation and lysis of a vegetative cell.
Thus it is not a true exotoxin (only released upon lysis)
Causes watery diarrhea, no dysentery.
Vaccine / Prevention: Clean and debride wounds for prevention.
Treatment: Antibiotics, intermittent hyperbaric oxygen treatment.
CLOSTRIDIUM TETANI: Gram-positive spore-forming rod.
Epidemiology / At Risk: Spores are uniquitous in the soil and introduced through puncture wounds.
Manifestations: Tetanus. A microgram of toxin is sufficient to kill.
Spore Germination:
Once spores introduced, they can lie dormant for years if wound remains well aerated.
As aeration is reduced (such as with age, for example), spores germinate and release exotoxin.
Exotoxin is taken up by nerve cells ------> retrograde transport to post-synaptic dendrites, where the exotoxin exerts its effect.
Generalized Tetanus: Lockjaw. Toxin may ascend to brain and affect respiratory center. ANS involvement and generalized spasms. Death by respiratory arrest. Symptoms:
Dysphagia
Drooling
ANS involvement: sweating, hyperthermia, cardiac arrhythmias.
Localized Tetanus: Localized spasm in area of infection. It may spread to generalized tetanus.
Cephalic Tetanus: Primary infection in head.
Processing:
Specimen: Only a few organisms in the lesions. Diagnosis is clinical -- not by microbiology.
Culture: Swarming Growth in culture. Thin surrounding film and faint beta-hemolysis.
Amplified in cooked hamburger broth. Selected for by heat.
Identification:
Opportunstic Strict Anaerobe
Genus is identified by colony morphology.
Somatic Antigen O: Fortunately there is only one serotype of Antigen-O, so that a vaccine is easy to make and effective.
Virulence:
Tetanospasmin: Heat labile, potent, antigenic exotoxin.
AB-Toxin cleaved in light (A) and heavy (B) fragments by an endogenous protease.
Fragment-B binds to ganglioside receptor of a nerve cell.
Fragment-A is taken up by endocytosis. Acidifcation of the vesicle causes Fragment-A to be release into cytoplasm.
Effect: Fragment-A moves up axon retrograde to the post-synpatic receptor. It blocks release of GABA and Glycerine at the post-synaptic terminal.
This results in unregulated excitatory post-synaptic potentials on nerve terminal, leading to spastic paralysis of skeletal muscle and respiratory arrest.
Vaccine / Prevention:
VACCINE: Given against the O-Antigen in cell wall.
Alum-precipitated toxoid (more immunogenic but can cause hypersensitivity): given to infants and children, and never-before immunized adults.
Children given at age 2, 4, 6, and 15-18 months.
Ammonium-precipiated toxoid: Given as a booster shot every ten years thereafter.
People are usually over-vaccinated for this bug.
ANTITOXIN: Given prophylactically if someone is potentially exposed (has a puncture wound) and has not been vaccinated within 5 years.
Tetanus toxin itself is not inherently immunogenic.
If a documented vaccine has been administered in last 5 years, no antitoxin is necessary.
Treatment: To someone who has never been vaccinated, the antitoxin is given in one arm, and a vaccine is given in the other arm, simultaneously. The two will not intermix if given in separate arms.
CLOSTRIDIUM BOTULINUM: Gram-positive spore forming rod.
Epidemiology / At Risk: Spores are in soils and sediment. Found in foods preserved at home at room temperature; old canned foods or self-canned foods.
Manifestations:
Food-Born Botulism: Usually found in alkaline foods, consumed without heating.
Initial Symptoms: Weakness, diziness, constipation.
Toxin is then absorbed from small intestine into blood and nerve cells.
Terminal Symptoms: Blurred vision, dry mouth, peripheral and respiratory flaccid paralysis. Death.
Infant Botulism: Infant at risk up to 1 year of age. After 1 year, GI ingestion of spores is not a problem.
Cause: Ingestion of spores, usually in unpasteurized honey.
Organisms replicate in GI tract and release toxin. Toxin is not readily absorbed through mucosa, but it can be absorbed if the problem is neglected.
Presents as failure to thrive, but can progress to flaccid paralysis.
Wound Botulism: Rare, similar clinical presentation as food botulism.
Processing:
Specimen: Blood, gastric contents, or food. Feces for children.
Serology: Do an assay for the toxin in the blood.
Stain: On infant feces, will find gram-positive rods.
Culture: Blood agar. Heat to boiling for 10 minutes to induce sporulation.
Smooth colonies, beta-hemolysis.
Identification:
ELISA can be used on culture for detection of toxin.
Oppotunstic Strict Anaerobe
Serotypes:
8 serologic types of toxin: A, B, C1, C2, D, E, F, G. All of them act the same.
Only types A, B, E affect humans.
Virulence:
Botulin Exotoxin: The most potent toxin known to man, i.e. lowest amount required to kill.
Phage-mediated, heat labile toxin. Antigenic. The toxin is released upon cell lysis.
MECHANISM: AB-Toxin. Fragment-A is translocated up neuron and blocks release of Acetylcholine ------> Flaccid Paralysis.
Enzyme resistance: Acid stable. Our bodies actually break down the toxin into fragments that are more toxic.
Host Immune Response: No persistent antibody to the toxin, therefore no lifelong immunity.
Again, the toxin is not inherently immunogenic.
Vaccine / Prevention: Alum-precipitated toxoid, only for lab workers.
PREVENTION: Head food, don't give unpasteurized honey to babies.
Antitoxin is available for types A, B, and E.
Treatment:
Ventilatory Support
Administer antitoxin.
Gastric Lavage to wash out any unabsorbed toxin.