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188 Cards in this Set
- Front
- Back
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What are seven gram-positive rods?
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1) Clostridia
2) Corynebacteria 3) Listeria 4) Bacillus 5) Propionibacterium 6) Lactobacillus 7) Erysipelothrix |
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What is the morphology of Clostridia
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Gram Positive Rod
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What are the oxygen requirements of clostridia?
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obligate anaerobes
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What are four important species of Clostridium?
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C. perfringens
C. botulinum C. difficile C. tetani |
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Which of the four important species of Clostridia form spores?
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ALL clostridia form spores.
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Which Clostridia are motile?
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All Clostrida except C. perfringens
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Where is Clostridia commonly found?
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Human intestines, aquatic area, soil, and sewage.
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Why is clostridia difficult to kill?
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They form endospores that are resistant to many disinfectants and to short periods of boiling.
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What process is effective in killing clostridia?
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Autoclaving @ 121C, under pressure, for 15 minutes.
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Where can C. perfringens be found in humans?
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Normal flora of the lower GI tract and vagina.
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Where are C. perfringens spores commonly found?
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soil
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What is the rate of growth for C. perfringens?
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FAST
Population can double every 10 minutes |
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What are three pathogenic substances secreted by C. perfringens?
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1) Exotoxin
2) Enterotoxins 3) Degradative enzymes |
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How are C. perfringens strains grouped?
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By the activity of their exotoxins
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What are the different groups of C. perfringens?
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Groups A & E
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What is the most common strain in human infection?
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Type A strains
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What are two major toxins elaborated by C. perfringens?
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Alpha toxin
Enterotoxin |
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What is alpha toxin?
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A lecithininase (phospholipase C3)
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What makes alpha toxin pathogenic?
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Lyses endothelial cells, erythrocytes, leukocytes, and platelets
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Where does enterotoxin act?
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Terminal small intestine.
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What makes enterotoxin pathogenic?
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Binds epithelial cell receptors and interferes with ion transport, eventually causing loss of intracellular proteins and fluids.
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What are some of the degradative enzymes produced by C. perfringens?
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DNAses hyaluronidase, proteases, and collegenases.
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What makes DNAses pathogenic?
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Degrades viscous deoxyribonucleic acid (DNA) in necrotizing tissue, promoting the spread of infection.
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What are five conditions commonly associated with C. perfringens?
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1) Myonecrosis (gas gangrene)
2) Cellulitis 3) Food poisoning 4) Necrotizing enteritis 5) Endometritis |
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What is myonecrosis?
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Bacterial invasion of healthy muscle tissue producing crepitations secondary to subcutaneous gas formation
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What are two common predisposing factors for myonecrosis?
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Open wounds and fractures.
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Do other organisms normally infect sites of C. perfringens infections?
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YES
Other anaerobes and facultative bacteria are commonly present |
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What is seen in smears of tissue and exudates of affected tissue?
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Large, G+ rods, cellular debris, often other bacteria, rarely spores and no neutrophils.
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What is the characteristic finding on C. perfringens colonies in blood agar?
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double zone of hemolysis
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What produces the gas in myonecrosis?
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Fermentation of carbohydrates
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What is the prognosis of untreated clostridial myonecrosis?
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Death within a coupe of days from gangrene.
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What is the cause of death in myonecrosis?
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Shock and multiple-organ failure secondary to intrvascular dissemination of exotoxin
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What is key to prevention and treatment of myconecrosis?
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Cleaning and debridement fo the wound.
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Which antibiotic commonly used to treat myonecrosis?
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Penicillin
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What else can be helpful in disrupting the progression of myonecrosis?
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Hyperbaric oxygen chambers.
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What is clostridial cellulitis?
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An accute inflammatory disorder of the skin with myonecrosis.
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What is the treatment for clostridial cellulitis?
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Incision of the skin in front of the infection leading edge.
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What are the most common vehicles for C. perfringens food poisining?
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Poultry
Fish Beef Pork |
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What causes C. perfringens food poisioning?
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Heat-labile toxin
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What are the common symptons of food poisoning with C. perfringens
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Nausea
Abdominal cramps Diarrhea without fever Diarrhea with fever |
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How soon after eating food contaminated with C. perfringens does one become symptomatic?
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8-18 hours after ingestion because bacteria has to grow and produce the toxin.
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What is the treatment for C. perfringens food poisoning?
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Supportive care because the disease is self-limiting.
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What is necrotizing enteritis?
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An uncommon acute ulcerative process in the small intenstine resulting in separation of the mucosal and submucosal layers forming large denuded areas.
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What is necrotizing enteritis also know as?
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Enteritis necroticans or Pigbel
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What is the mortality rate for necrotizing enteritis?
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50%
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What is endometritis?
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Infection of the uterine endometrium frequently caused by anaerobic organism.
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What predisposes an individual to clostridial endometritis?
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Inadequate sterilized instruments of incomplete abortion.
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What is the clinical progression of untreated clostridial endometritis?
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Gangrene of uterine tissue, toxemia, and eventual bacteremia.
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Where are C botulinum spores classically found?
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Soil
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What do the C. botulinum spores usually contaminate?
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Foods, including honey, vegetables, and meats.
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When does C. botulinum become a problem for humans?
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When contaminated foods are canned and vacuum packed without adequate sterilization, leading to germination and toxin production.
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What causes botulism?
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A neutoroxin called botulinum toxin
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What are the most common types of botulinum toxin?
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A
B E |
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What is the pathogenesis of botulinum toxin?
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A zinc metalloprotease that blocks the release of acetylcholine at peripheral cholinergic synapses by cleaving specific SNARE proteins (e.g. synaptobrevins)
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What is the resultant type of paralysis regarding botulinum toxin?
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Flaccid paralysis
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How does the toxin reach the peripheral cholinergic synapses?
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Hematogenous spread secondary to intestinal absorption.
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When are symptoms first observed after botulinum toxin ingestion?
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12-36 hours
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What are three clinical manifestations of C. botulinum
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Infant botulism
classic botulism Wound botulism |
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What is the most common form of botulism in the US?
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Infant botulism (floppy baby syndrome)
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What is the classic source of C. botulinum spores causing disease?
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Honey
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What are the common symptoms of infant botulism?
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Feeding difficulties, lethargy, decreased muscle tone.
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What are common symptoms of classic botulism?
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Double vision, difficulty swallowing, and other cranial nerve dysfunctions.
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What is the mortality rate of classic botulism?
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15%
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What is the most common caues of death in classic botulism?
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Respiratory failure
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What is wound botulism?
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Botulism occurring as a result of absorption of toxin from an infected wound.
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How is botulism commonly treated?
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Trivalent antitoxin against the three common types (A, B, and E)
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How can botulinum toxin be used therapeutically?
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In small doses, it can be used to relieve strabismus, to decrease poststroke spasticity, or to reduce wrinkles.
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What percentage of the population carries C. difficile in their GI tracts?
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~3%
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What is the disease most commonly associated with C. difficile?
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Pseudomembranous colitis
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What is pseudomembrane composed of?
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Mucus, inflammatory cells, fibrin, and cellular debris.
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What is the classic presentation of C. diff.?
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Nonbloody diarrhea after broad-spectrum antibiotic treatment (e.g. clindamycin or Beta-lactam antibiotics)
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Why does C. diff occur after broad-spectrum antibiotic treatment?
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Suppression of normal flora by antibiotics allows proliferation of C. difficile.
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Are neutrophils found in the diarrhea associated with C. diff?
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Approximately 50% of the time.
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How is C. difficile transmitted?
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Fecal-oral route or by contact with spores found on bedding and toilets.
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What are the exotoxins produced by pathogenic strains called?
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Exotoxins A & B
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Which exotoxins of C. diff are enterotoxin?
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Toxin A
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Which C.diff toxin is a cytotoxin?
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Toxin B
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Which C. diff toxin is predominantly responsible for pseudomembrane formation?
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Toxin B
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What laboratory test is used to diagnose C. difficile?
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Enzyme-linked immunoabsorbent assay (ELISA) test for exotoxins A&B.
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How is pseudomembranous colitis generally treated?
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Supportive care, discontinuation of offending drug, and starting of new antibiotics.
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Which antibiotics are most commonly used for C. difficile?
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Metronidazole or Vancomycin
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Why are metronidazole and vancomycin used for C. difficile?
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These antibiotics suppress C. difficile and allow normal flora to reestablish themselves.
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What is the characteristic histologic morphology of C. tetani?
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Tennis racquet shaped rods.
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Are smears and cultures generally effective in diagnosis of C. tetani?
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NO
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What is a common portal of entry for c. tetani?
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Wound contact (puncture lesions) with infected soil.
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What is the incubation period for C. tetani toxin production?
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4 days to several weeks.
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What is another term for tetanus toxin?
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Tetanospasmin
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What is the structure of tetanospasm?
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A light fragment (A) bonded to a heavy fragment (B) by a disulfide bond.
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What role does the light fragment (A) play?
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Acts as a protease and blocks release of inhibitory neurotransmitter glycine and gamma-aminobutyric acid (GABA)
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What role does the heavy fragment (B) play?
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Controls binding to neurons and aids in the cellular penetration of light fragment A
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How is tetanus toxin transported systemically?
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hematogenously
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How is tetanus toxin transported neuronally?
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Retrograde neuronal transport
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How does tetanus typically present?
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Spastic paralysis at site of infection.
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What symptom is pathognomomic for tetanus?
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Lock jaw (trismus).
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What is the characteristic grimace in affected people called?
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Risus sardonicus
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What is the most common cause of death with tetanus?
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Respiratory failure
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What is crucial in effctive diagnosis and treatment of tetanus?
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Clinical suspicion because treatment is empirical.
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What is used in the pharmacologic treatment of tetanus?
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Antitoxin
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What else is used in treating tetanus?
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1) Sedatives and muscle relaxants to prevent spasm.
2) Penicillin and common wound care |
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Why is tetanus rare today in developed countries?
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Childhood immunizations against the tetanus exotoxin and booster shots have decreased incidence.
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What is given for tetanus immunizations?
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tetanus toxoid
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What is tetanus toxoid?
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Formalin inactiveated, but antigenic tetanus toxin.
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What other vaccines are usually given with this vaccine during childhood immunizations?
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Diptheria toxin and pertussis antigens.
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What is the recommended immunization schedule?
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1) 2, 4, 6, & 18 months
2) booster upon school entry 3) Boosters every 10 years afterward |
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Why is tetanus seen more often in the elderly?
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Failure to followup on booster shots.
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What are the two non-spore forming G+ rods?
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Corynebacterium diptheriae
Listeria monocytogense |
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What are the oxygen requirements of the two non-spore forming G+ rods?
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Facultative anaerobic
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What is the morphology of C. diptheriae?
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Small
Pleomorphic Unencapsulated G+ rods |
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How are collections of C. diptheriae commonly described?
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Chinese characters
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How is C. diptheriae usually spread?
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Respiratory droplets
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How can one become infected with C. ditheriae other than by respiratory droplets?
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Puncture wound or cut
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What is the pathogenesis of diptheria?
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Absorption of an exotoxin composed of an A and a B fragment.
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How does this diptheria toxin affect the cell?
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Inhibits eukaryotic protein synthesis
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What is the role of fragment A in diphtheria toxin?
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Adenosine diphosphate ribosylation of elongation factor-2 resulting in EF-2 inactivation and blockage of the translocation of polypeptidyl-transfer ribonucleic acid. (tRNA).
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What is the role of fragment B in diphtheria toxin?
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Binding to cell and delivery of fragment A
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Where is the toxin encoding diphtheria DNA found?
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In a bacteriophage
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Which strains of bacteriophages can produce C. diptheriae capable of active infection?
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Lysogenic strains
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Why can lysogenic strains produce C. diphtheriae capable of active infection?
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Lysogeny allows bacteriophage integration into the bacterial genome and toxin (protein) expression.
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Where is the toxin encoding diphtheria DNA found?
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In a bacteriophage
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Which strains of bacteriophages can produce C. diptheriae capable of active infection?
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Lysogenic strains
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Why can lysogenic strains produce C. diphtheriae capable of active infection?
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Lysogeny allows bacteriophage integration inot the bacterial genome and toxin (protein) expression.
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Where does C. diphtheriae usually infect humans?
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Throat and nasopharynx
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What is a classic clinical manifestation of C. diphtheriae infection?
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Pseudomembrane pharyngitis.
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What is psdudomembrane pharyngitis.
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An adherent, thick and gray exudateive pseudomembrane forming in the throat or nasopharynx with lymphadenopathy
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What are two rare clinical manifestations of diphtheria?
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Myocarditis
Neuritis of cranial nerves |
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How does the host neutralize the toxin?
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Antibody formation
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How is clinical C. diphtheriae diagnosed?
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Although no quick and reliable lab tests exists, cultures may yield G+ rods with blue and red granules.
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How is C. diphtheria definitively diagnosed?
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Isolation of C. diphtheriae via potassium tellurite containing Tinsdale agar and demonstration of toxin production via precipitin reaction.
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How is diphtheria treated?
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Empiric treatment, i.e., immediate administration of hores serum antitoxin and antibiotics.
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Which antibiotics can be used?
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Penicillin g and erythromycin
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How is diptheria prevented
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DTaP vaccine
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What are diphtheroids?
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Corynebacterium species similar to C. diphtheriae.
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What patient population gets affected by diptheroids?
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Immunosuppressed
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Which antibiotic is used to treat diphtheroids?
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Vancomycin
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What is the morphology of Listeria?
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Intracellular, small, G+ rods
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What type of hemolytic reaction do the rods show?
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narrow zone of Beta-hemolysis
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What feature helps distinguish Listeria from streptococcus?
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Listeria are catalase positive
Streptococcus are catalase negative |
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What morphologic features do Listeria and Corynebacterium share?
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Nonspore-forming G+ rods
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What nonmorphologic feature distinguishes listeria from Corynebacterium?
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Listeria exhibits a tumbling motion and motility at room temperature
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What is the important pathogenic species of Listeria?
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Listeria monocytogenes.
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What populations are most commonly infected by Listeria?
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Pregnant women
Fetuses of infected mothers Immmunocompromised individuals |
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How do most people become infected with listeria?
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Via foot
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Does transmission from mother to child occur across the placenta or during the delivery?
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Transmission can occur in both situations.
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How does Listeria enter cells?
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Via phagocytosis
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How does Listeria penetrate the phagocytic vacuole to enter the cytoplasm?
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Pyroduction of listeriolysin O toxin
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Cell Listeria move from cell to cell?
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YES
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How does listeria move from cell to cell?
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Forms a "battering ram" by hijacking host cell actin to provide a portal of entry from one to another.
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What type of enymes aid in this passage across the cell membrane?
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Phospholipases
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What are three clinical manifestations of listeria?
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Meningitis
Sepsis Gastroenteritis outbreaks |
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What are two uncommon clinical manifestations of Listeria?
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Endocarditis
Lymphadenitis |
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How do infected mothers present?
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Flu-like illness or asymptomatically
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What is characteristic of gastroenteritis secondary to listeroisis?
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Watery diarrhea, fever, and headache
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How is the diagnosis of listeria infection usually made?
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Gram stain and culture
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What are the antibiotics commonly prescribed to treat listeria infections?
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Ampicililin and Gentamicin (esp. in newborns)
TMP/SMX and supportive care |
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What is the morphology of Bacillus?
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Bluntended G+ rods
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What are the oxygen requirements of bacillus?
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Obligate or facultative aerobes
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Does bacillus form endospores?
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YES
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What are the two more commonly known pathogenic species of bacillus?
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Bacillus anthracis
Bacillus cereus |
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What do B. anthracis affect more commonly, humans or animals?
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Animals
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Which animals are comoonly affected by B. anthracis?
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Herbivores, e.g., sheep
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How are humans exposed to B. anthracis?
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Inhalation of spores, ingestion of contaminated food, and contact with contaminated animal products
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What are common entry sites of B. anthracis?
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Skin, mucous membrane and respiratory tract.
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When exposed, what is the contaminating agent?
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Endospores
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Are B. anthracis spores easily killed?
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NO
The spores are both head resistant and difficult to eradicate via chamical or physical means. |
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What are three virulence factors of B. anthracis?
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1) Antiphagocytic capsule (D-glutamate polymers)
2) Edema factor (exotoxin) 3) Lethal toxin (exotoxin) |
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What is edema factor?
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A calmodulin-dependent adenylate cyclase, increasing cyclic adenosine monophosphage resulting in severe edema
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What is lethal toxin?
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A protease responsible for cleaving the kinase that activates the mitogen activated protein kinase (MAPK) signal transduction pathway, inhibiting cell growth, increasing the production of tumor necrosis factor and causing cell death.
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What are two clinical manifestations of B. anthracis?
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Cutaneous anthrax
Pulmonary anthrax |
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What is the most common form of anthrax seen in humans?
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Cutaneous anthrax
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What are the five stages of cutaneous anthrax?
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papule
Black, painless "malignant" pustules Invasion of regional lymph nodes Invasion of bloodstream Sepsis |
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What is the overall mortality of cutaneous anthrax?
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20%
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What antibiotics are commonly used for the treatment of anthrax?
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Penicilin
Tetracyclines Ciprofloxacin |
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What is another term for pulmonary anthrax?
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Woolsorters disease
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What is the cause of pulmonary anthrax?
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Inhalation of B. anthracis spores.
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What findings are characteristic of pulmonary anthrax?
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Mediastinal widening and sometimes hemorrhagic lymphadenitis.
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What is the overall mortality of untreated pulmonary anthrax?
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Almost 100%
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How is B. cereus morphologically different from B. anthracis?
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They are unencapsulated and motile.
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What is B. cereus classically associated with?
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Food poisoning, especially from reheated fried rice.
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What is the route of entry for disease causing B. cereus spores?
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The gastrointestinal tract.
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What are the two toxins produced by B. cereus?
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1) Heat-labile toxin
2) Heat-stable toxin |
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Can each toxin produce different types of food poisoning?
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Yes
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How is the heat-labile toxin similar to cholera toxin?
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Both result in ADP ribosylation of a G-protein that stimulates the productin of cAMP via adenylate cyclase
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What is the presentation of disease caused by heat-labile toxin?
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Watery, nonblody diarrhea, nausea, and abdominal pain 18 hours after ingestion lasting 12-24 hours.
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What is the presentation of disease caused by the heat-stable toxin?
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Acute onset of nausea and vomiting with some diarrhea 4 hours after ingestion.
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How do you treat food poisoning caused by B. cereus?
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Supportive care
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Which anaerobic bacteria is associated with acne?
|
Propionibacterium acnes
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Which G+ rod is normal flora for mucous membranes and produces lactic acid?
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Lactobacillus
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Which G+ rod is associated with skin infections found most often in those who deal with animal meat, i.e., butchers?
|
Erysipelothrix rhusiopathiae
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