Pathogenic Anaerobic Gram-Positive Bacilli

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Pathogenic Anaerobic Gram-Positive Bacilli
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Corynebacteria (Genus Corynebacterium)
ØAerobic or facultatively anaerobic ØSmall,
pleomorphic (club-shaped), gram-positive bacilli
that appear in short chains (V or Y
configurations) or in clumps resembling Chinese
letters ØCells contain metachromatic granules
(visualize with methylene blue stain) ØLipid-rich
cell wall contains meso-diaminopimelic acid,
arabino-galactan polymers, and short-chain
mycolic acids ØLysogenic bacteriophage encodes
for potent exotoxin in virulent strains
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Distinguishing Features of CMN Group
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Pathogenic Corynebacterial Species

• Corynebacterium diphtheriae
• Corynebacterium jeikeium
• Corynebacterium urealyticum

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Corynebacterium urealyticum ØUrinary tract
infections (UTIs) rare but important ØUrease
hydrolyzes urea release of NH4, increase in pH,
alkaline urine, renal stones
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Corynebacterium jeikeium ØOpportunistic
infections in immunocompromised (e.g., patients
with blood disorders, bone marrow transplants,
intravenous catheters) ØMultiple antibiotic
resistance common (MDR) ØCarriage on skin of up
to 40 of hospitalized patients (e.g., marrow
t-plants)
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Corynebacterium jeikeium Carriers
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• Corynebacterium diphtheriae
• ØRespiratory diphtheria (pseudomembrane on
  pharynx) and cutaneous diphtheria
• ØPrototype A-B exotoxin acts systemically
• Toxoid in DPT and TD vaccines
• ØDiphtheria toxin encoded by tox gene introduced
  by lysogenic bacteriophage (prophage)
• ØSelective media cysteine-tellurite serum
  tellurite Loefflers
• ØGravis, intermedius, and mitis colonial
  morphology

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Epidemiology of Diphtheria
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Incidence of Diphtheria in the USA
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Incidence of Diphtheria in Former Soviet Union
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Virulence Factors in Corynebacterium Species
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Diphtheria tox Gene in Beta Bacteriophage and
Prophage
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See Handout on Exotoxins
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Mechanism of Action of Diphtheria Toxin
Inhibition of Protein Synthesis
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Molecular Structure of Diphtheria Toxin
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Diagnostic Schick Skin Test
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In vivo Detection of Diphtheria Exotoxin
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Listeria monocytogenes

• ?Gram-positive beta-hemolytic bacillus
• ?Multiply at refrigerator temperatures (4oC)
• ?Tumbling motility at room temperature
• CAMP Test positive (like Group B Streptococcus)

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Where do we find Listeria?

• Intestinal tract of mammals birds (especially
  chickens)
• Persists in soil
• Soft cheeses unwashed raw vegetables
• Raw or undercooked food of animal origin
• Luncheon meats
• Hot dogs
• Large scale food recalls have become common

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Epidemiology of Listeriosis
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Epidemiology of Listeria Infections
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Listeriosis

• Neonates, elderly immunocompromised
• Granulomatosis infantiseptica
• Transmitted to fetus transplacentally
• Early septicemic form 1-5 days post-partum
• Delayed meningitic form 10-20 days following
  birth
• Intracellular pathogen
• Cell-mediated and humoral immunity develop
• Only cell-mediated immunity is protective

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Methods That Circumvent Phagocytic Killing
See Chpt. 19
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Intracellular Survival Replication of Listeria
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Erysipelothrix rhusopathiae

• Gram-positive non-motile bacillus forms
  filaments
• Occupational disease of meat and fish handlers,
  hunters, veterinarians
• Preventable with protective gloves clothing
• Erysipeloid in humans erysipelas in swine
  turkeys
• Organisms enter through break in skin
• Nonsuppurative, self-limiting skin lesions with
  erythema and eruption
• Peripheral spread may lead to generalized
  infection, septicemia and/or endocarditis
• Organisms can be isolated from skin biopsy

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Epidemiology of Erysipelothrix Infection
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REVIEW
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• Corynebacterium diphtheriae
• ØRespiratory diphtheria (pseudomembrane on
  pharynx) and cutaneous diphtheria
• ØPrototype A-B exotoxin acts systemically
• Toxoid in DPT and TD vaccines
• ØDiphtheria toxin encoded by tox gene introduced
  by lysogenic bacteriophage (prophage)
• ØSelective media cysteine-tellurite serum
  tellurite Loefflers
• ØGravis, intermedius, and mitis colonial
  morphology

REVIEW
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Diphtheria tox Gene in Beta Bacteriophage and
Prophage
REVIEW
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See Handout on Exotoxins
REVIEW
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Mechanism of Action of Diphtheria Toxin
Inhibition of Protein Synthesis
REVIEW
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Corynebacterium jeikeium ØOpportunistic
infections in immunocompromised (e.g., patients
with blood disorders, bone marrow transplants,
intravenous catheters) ØMultiple antibiotic
resistance common (MDR) ØCarriage on skin of up
to 40 of hospitalized patients (e.g., marrow
t-plants)
REVIEW
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Corynebacterium urealyticum ØUrinary tract
infections (UTIs) rare but important ØUrease
hydrolyzes urea release of NH4, increase in pH,
alkaline urine, renal stones
REVIEW
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Listeria monocytogenes

• ?Gram-positive beta-hemolytic bacillus
• ?Multiply at refrigerator temperatures (4oC)
• ?Tumbling motility at room temperature
• CAMP Test positive (like Group B Streptococcus)

REVIEW
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Epidemiology of Listeria Infections
REVIEW
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Listeriosis

• Neonates, elderly immunocompromised
• Granulomatosis infantiseptica
• Transmitted to fetus transplacentally
• Early septicemic form 1-5 days post-partum
• Delayed meningitic form 10-20 days following
  birth
• Intracellular pathogen
• Cell-mediated and humoral immunity develop
• Only cell-mediated immunity is protective

REVIEW
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Intracellular Survival Replication of Listeria
REVIEW
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Erysipelothrix rhusopathiae

• Gram-positive non-motile bacillus forms
  filaments
• Occupational disease of meat and fish handlers,
  hunters, veterinarians
• Preventable with protective gloves clothing
• Erysipeloid in humans erysipelas in swine
  turkeys
• Organisms enter through break in skin
• Nonsuppurative, self-limiting skin lesions with
  erythema and eruption
• Peripheral spread may lead to generalized
  infection, septicemia and/or endocarditis
• Organisms can be isolated from skin biopsy

REVIEW
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