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Corynebacterium and Other Non Spore-forming Gram-Positive Rods Chapter 16 PowerPoint Presentation
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Corynebacterium and Other Non Spore-forming Gram-Positive Rods Chapter 16

Corynebacterium and Other Non Spore-forming Gram-Positive Rods Chapter 16

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Corynebacterium and Other Non Spore-forming Gram-Positive Rods Chapter 16

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    1. Corynebacterium and Other NonSpore-forming Gram-Positive Rods Chapter 16 Corynebacterium sp. Listeria monocytogenes Erysipelothrix rhusiopathiae

    2. Corynebacteria Significant Corynebacterium species C. xerosis C. pseudodiphtheriticum C. pseudotuberculosis C. jekeium C. ulcerans Rhodococcus equi Arcanobacterium haemolyticum

    3. Corynebacterium Species General characteristics Found as free-living saprophytes in fresh and salt water, in soil and in the air Members of the usual flora of humans and animals (often dismissed as contaminants) Often called diphtheroids Corynebacterium diphtheriae is the most significant pathogen Other species may cause infections in the immunocompromised hosts

    4. Corynebacterium Species: General Characteristics Morphology Gram-positive, nonspore-forming rods Arrange in palisades: L-V shape; Chinese characters Pleomorphic: club-ends or coryneform Beaded, irregular staining

    5. C. diphtheriae: Agent of Diphtheria Toxigenic Corynebacterium diphtheriae Worldwide distribution but rare in places where vaccination programs exist Exotoxin, Diphtheria toxin, as the virulence factor Not all C. diphtheriae strains produce toxin Toxin is produced by certain strains Lysogenized by bacteriophage with toxin gene (tox+) Toxin is antigenic

    6. Toxigenic Corynebacterium diphtheriae Toxin consists of two fragments A: Active fragment Inhibits protein synthesis Leads to cell/tissue death B: Binding Binds to specific cell membrane receptors Mediates entry of fragment A into cytoplasm of host cell

    7. Clinical Forms of Diphtheria Respiratory Acquired by droplet spray or hand to mouth contact Non-immunized individuals are susceptible Non-respiratory Systemic Skin and cutaneous forms

    8. C. diphtheriae: Causative Agent of Diphtheria Respiratory diseasediphtheria Incubation period2 to 5 days Symptoms: sore throat, fever, malaise Toxin is produced locally, usually in the pharynx or tonsils Toxin causes tissue necrosis, can be absorbed to produce systemic effects Forms a tough grey to white pseudomembrane which may cause suffocation

    9. C. diphtheriae: Causative Agent of Diphtheria C. diphtheriae pseudomembrane WBC + organism

    10. Clinical Infections: Non-Respiratory Disease Systemic infections Toxin is absorbed in the blood stream and carried systemically Affects the kidneys, heart, and nervous system Death occurs due to cardiac failure Cutaneous form More prevalent in the tropics Infections occur at the site of minor abrasions Maybe superinfected with Streptococcus pyogenes and/or Staphylococcus aureus

    11. Treatment Infected patients treated with anti-toxin and antibiotics Anti-toxin produced in horses Antibiotics have no effect on circulating toxin, but prevent spread of the toxin Penicillin drug of choice

    12. Laboratory Diagnosis Microscopic morphology Gram-positive, nonspore-forming rods, club-shaped, can be beaded Appear in palisades and give "Chinese letter" arrangement Produce metachromatic granules or Babes Ernst bodies (food reserves) which stain more darkly than remainder of organism

    13. Laboratory Diagnosis: Cultural Characteristics Loeffler's slant or Pai's slantUsed to demonstrate pleomorphism and metachromatic granules ("Babes Ernst bodies) Growth on Serum Tellurite or modified Tinsdale exhibits brown or grayish? to black halos around the colonies

    14. Laboratory Diagnosis: Cultural Characteristics BAP@ 24-48 hours small, grey translucent colonies Small zone of ?- hemolysis also seen

    15. Laboratory Diagnosis Identification Confirm identification by fermentation reactions (glucose +) Catalase positive Urease negative Non-motile

    16. Laboratory Diagnosis Toxigenicity testing Elek test p. 413 Immunodiffusion test Organisms are streaked on media with lox Fe content to maximize toxin production. Identification of C. diphtheriae does NOT mean the patient has dipheria. Must show the isolate produces the toxin.

    17. C. diphtheriae Treatment: antitoxin Prevention: DPT immunization

    18. C. jekeium Clinical Infections Septicemia Meningitis Pulmonary disease Populations Affected Immunosuppressed IV drug users Recent invasive procedure

    19. C. jekeium Colony Morphology Isolation & identification BAP: 48-72 hours @ 35oC in ambient air or 5% CO2 small, gray-white colony, nonhemolytic Gram stain: pleomorphic, club-shaped GPR arranged in V forms or palisades

    20. C. jekeium Lab Diagnosis Identification Nitrate reduction= negative Urea= negative Sucrose= negative Glucose= positive

    21. C. jekeium Susceptibility testing Exhibits resistance to multiple antibiotics Susceptible to vancomycin

    22. Differentiating Characteristics of Corynebacterium Species

    23. Listeria monocytogenes: General Characteristics Gram-positive, nonspore-forming rods Only human pathogen in genus Widespread in nature Known to infect a wide variety of animals Human exposure is limited; direct or indirect Transient colonization occurs without disease

    24. Listeria monocytogenes: Clinical Infections Adults Septicemia/meningitis in the compromised/elderly Mild flu-like syndrome in pregnant women could be fatal to fetus Ingestion of contaminated food (cottage cheese, coleslaw, chicken, hot dogs, lunch meat) Neonatal Early onset from intrauterine transmission results in sepsis; high mortality rate Late onset manifests as meningitis; lower mortality rate

    25. Listeria monocytogenes: Virulence Factors Hemolysin ( Listeriolysin O)- damages macrophage Catalase Superoxide dismutase Phospholipid C P60 surface protein- induces phagocytosis thru adhesion and penetration

    26. Laboratory Diagnosis: L. monocytogenes Identification Microscopic morphology Gram Positive nonspore-forming coccobacillary, pairs or short chains Colony Morphology Grows well on blood agar; colonies produce a narrow zone of hemolysis similar to Group B Streptococcus Small, round and translucent

    27. Laboratory Diagnosis: L. monocytogenes Grows well at 0.5 C to 45 C Because of this temperature range, especially the cooler end of the range, this organism grows well in refrigerated products, such as cream, cheese, deli meats, etc. Can sometimes be isolated after cold enrichment (hold broth at 4 C for several weeks and subculture)

    28. Laboratory Diagnosis: L. monocytogenes Identification Catalase positive Motility: Motile at 25o C; "umbrella" type ? Tumbling motility in hanging drop preparations (this can be seen on Gram Stain Tutor at

    29. Laboratory Diagnosis: L. monocytogenes Identification CAMP test Produces a block type of hemolysis in contrast to arrow-shape produced by Group B Streptococcus

    30. Differentiating Characteristics between L. monocytogenes and Other Gram Positive Bacteria

    31. Erysipelothrix rhusiopathiae: General characteristics Gram positive, nonspore-forming, pleomorphic rods (can produce long filaments) Distributed in nature Can cause disease in animals (swine, turkey, sheep); swine is the main reservoir Humans acquire the infection through occupational exposure, such as cuts & scratches (fish handlers, animal products)

    32. Erysipelothrix rhusiopathiae: Clinical Infections Erysipeloid Self-limiting localized infection at the site of inoculation Produces painful swelling, usually on the hands or fingers Heals within 3 to 4 weeks Endocarditis May occur in those who have had valve replacements Disseminated infections may occur, but rarely

    33. Laboratory Diagnosis: Erysipelothrix rhusiopathiae Microscopic Morphology Pleomorphic, gram-positive thin rods that may form long filaments, may be arranged singly, in short chains, or in a V shape

    34. Laboratory Diagnosis: Erysipelothrix rhusiopathiae Identification Catalase negative CO2 is required Distinguishing characteristic: Production of H2S on TSI Microaerophilic Nonmotile Test tube brush growth in semisolid motility media

    35. Laboratory Diagnosis: Erysipelothrix rhusiopathiae Colony Morphology Grows on blood or chocolate agarcolonies may appear gray or translucent, pinpoint with alpha hemolysis or nonhemolytic

    36. Treatment: Erysipelothrix rhusiopathiae Penicillin, cephalosporin, erythromycin

    37. Characteristics of Corynebacterium, Listeria, and Erysipelothrix

    38. Lactobacillus Widely distributed in nature Normal flora of mouth, GI tract and female genital tract Treat with pencillin plus an aminoglycoside resistant to vancomycin (helps in diagnosis) Clinical Infections Bacterial vaginosis Bacteremia, endocarditis, meningitis (rare)

    39. Lactobacillus Microscopic Morphology Long, slender gram positive pleomorphic bacilli Non-spore forming Colony Morphology Microaerophilic SBA: pinpoint, a- hemolytic colonies Lab Diagnosis Catalase negative