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43 Cards in this Set
- Front
- Back
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Listeria Species feats
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Non-sporeforming, facultative Gram-positive bacilli
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Clinical Settings for Listerial Infections
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Neonatal sepsis/meningitis
Meningitis or parenchymal brain infection in patients with underlying disease Meningitis or parenchymal brain infection in adults > 50 years Simultaneous meningeal and parenchymal brain infection Fever during pregnancy, particularly in the third trimester |
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Listerial Infections can cause Meningitis or parenchymal brain infection in patients with underlying disease like
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Hematologic malignancies, AIDS, organ transplantation, or corticosteroid immunosuppression
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Listeria Meningitis Presentation is usually,
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acute,
May be subacute and may mimic tuberculous meningitis Ataxia, tremors, seizures Fluctuating mental status more common Blood cultures positive in 75% of cases |
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When analyzing CSF from listeria meningitis patients
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Gram stain of CSF is negative in many cases
CSF glucose may be normal in more than 60% of cases Mononuclear cell predominance is present in about one-third of cases |
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Food-Borne Listeriosis
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cabbage, cole slaw, soft cheeses, and shrimp
raw milk and vegetables, fish, poultry, fresh and processed meats and fish |
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Food-Borne Listeriosis may cause
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self-limited febrile enteritis with nausea, vomiting, and diarrhea
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Universal Dietary Recommendations for Preventing Foodborne Listeriosis
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Thoroughly cook food from animal sources
Beef, pork, and poultry Thoroughly wash vegetables before eating Keep uncooked meats separate from vegetables, cooked food, and ready-to-eat foods Avoid consumption of unpasteurized milk or food made from raw milk Wash hands, knives, and cutting boards after handling uncooked foods |
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Isolation of Listeria monocytogenes is incubated at 4C because
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Cold enrichment for recovery from stool, food, or environmental specimens.
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L. monocytogenes on blood sheep agar
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“Soft” β-hemolysis on sheep blood agar
At 24 hr, β-hemolytic underneath colony Catalase-positive Motile at 25oC Bile esculin-positive |
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Therapy for Listeria monocytogenes Infections
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Ampicillin recommended
Gentamicin may be added in some cases Alternative agent to ampicillin is TMP/SMX Other agents are bacteristatic, not bactericidal Committee for Clinical Laboratory Standards (CLSI) Plasmid-borne resistance to chloramphenicol, macrolides, and tetracyclines has been identified |
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Erysipelothrix spp. characteristics
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Regular, facultative, nonsporeforming, Gram-positive rods
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Erysipelothrix spp. causes
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Causes swine erysipelas
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Significance of Erysipelothrix rhusiopathiae
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Infections in animals (e.g., swine, cattle)
Erysipeloid Sepsis and bacteremia Native and prosthetic valve endocarditis In urban areas, patients like construction workers are exposed to animal waste without knowing and get infected with erysipelothrix. If patient has heart problems this organism can develop endocarditis |
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Identification of Erysipelothrix rhusiopathiae
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Gram-positive/variable rods, coccobacilli, or filaments
Catalase-negative Non-motile Hydrogen sulfide-POSITIVE in Kligler’s iron agar (KIA) (Only gram +organism that does this) Nitrate-, esculin-, urease-, xylose-, maltose-, and mannose-negative “BOTTLE-BRUSH” growth in gelatin stab culture E. rhusiopathiae (sucrose - negative) E. tonsillarum (sucrose-positive) |
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Lactobacillus spp feats
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Gram-positive, non-sporeforming, slender rods; occasionally in pairs, chains
Facultative (some are anaerobic) Glucose fermentation: LACTIC ACID , with minor acetic, formic, and succinic acids |
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Lactobacillus is found in
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Normal flora of the vagina, gastrointestinal tract, and oropharynx of humans
Normal flora or other animals Found in nature (e.g., water, silage, sewage) Used in food processing industries (e.g, dairy products, grains, meats, fish) Probiotics: Lactobacillus acidophilus (in yogurt) |
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Lactobacilli Facultative species produce
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hydrogen peroxide (H2O2), while anaerobic species do not
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Significance of Lactobacillus Species
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Opportunistic agents
Endocarditis Bacteremia in compromised hosts Cancer, transplantation, AIDS, diabetes Pleuropulmonary infections |
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Risk Factors for Lactobacillus Bacteremia
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Persistent neutropenia
Use of broad-spectrum antimicrobial agents Immunosuppressive therapy for allograft transplantation Chemotherapy for cancer Use of invasive gastrointestinal, respiratory tract, and gynecological instrumentation or procedures |
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Some Lactobacillus species are resistant to
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vancomycin
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Non-lipophilic Corynebacteria species DO NOT REQUIRE
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lipids for growth
Lipophilic species REQUIRE lipid for growth |
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Lipophilic Corynebacteria on blood agar
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Since blood agar contains RBC’s, there is LIPID PRESENT, so lipophilic species will grow (below)
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Lipophilic Corynebacteria on chocolate agar
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chocolate agar contains powdered hematin and NO LIPID, lipophilic species do not grow on chocolate agar (right, bottom)
Non-lipophilic species grow luxuriantly on both blood agar AND chocolate agar |
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Lipophilic Corynebacteria
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Corynebacterium jeikeium
Corynebacterium urealyticum |
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Corynebacterium diphtheriae Toxinogenicity associated with
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lysogenization with the β-corynephage
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Corynebacterium diphtheriae Toxinogenic/non-toxinogenic strains associated with
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endocarditis and other serious infections, primarily among the homeless and IV drug users
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Diphtheria Toxin: Structure
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AB toxin, A being the biological active domain.
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Corynebacterium diphtheriae course
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Described as white early in the course of the illness, the diphtheritic pseudomembrane becomes dark gray and leather-like
Results from local toxin production Spread of the membrane indicates more systemic toxicity Tonsillar, anterior cervical, and submandibular lymphadenopathy Swelling of the neck (so-called “bull neck” appearance) Continued progression may lead to respiratory distress and death |
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Isolation of Corynebacterium diphtheriae Non-selective routine media
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Sheep blood agar and/or CNA agar
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Isolation of Corynebacterium diphtheriae
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Cystine-tellurite-blood agar
Modified Tinsdale agar C. diphtheriae, C. pseudotuberculosis, and C. ulcerans form black colonies with brown haloes |
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Isolation of Corynebacterium diphtheriae Media containing cystine and tellurite
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Contains coagulated beef serum and egg
Characteristic morphology when stained with methylene blue |
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see slide
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45
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Diphtheria Toxin Toxic effects on the heart
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Diffuse myocardiopathy in 20-70%
Circulatory collapse Acute congestive heart failure |
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Diphtheria Toxin Peripheral and central nervous system involvement
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Paralysis of the soft palate and posterior pharynx
Oculomotor and ciliary paralysis Risk of aspiration and pneumonia |
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Diphtheria Toxineffects on liver, and kidneys
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Fatty degeneration
Focal necrosis |
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Diphtheria Toxin causes death due to
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Death from cardiac failure or paralysis of the diaphragm
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Corynebacterium diphtheriae Non-lipophilic on sheep blood agar appearance
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Grey-white, smooth, non-hemolytic colonies
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Corynebacterium diphtheriae tx
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erythromycin or penicillin, along with anti-toxin
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ELEK Test slide 49
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ELEK
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Most frequently isolated Corynebacterium species from human clinical specimens
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Corynebacterium amycolatum
Lacks cell wall mycolic acids (“a-mycolate”) Forms dry, matte, “waxy” and “wrinkly” colonies on blood agar |
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in a premature infant Corynebacterium amycolatum causes
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fatal sepsis.
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Corynebacterium amycolatum isolated from
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from wounds, blood, joint fluid, bone, and the urinary tract
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