1 / 56

Gram Positive Rods

Gram Positive Rods. Listeria. Small Gram positive rods or coccobacilli (<2 μ m ) Tolerate wide temperature and pH range Small haemolytic colonies on blood agar ( β haemolysis ) Facultative anaerobes Catalase positive, oxidase negative Tumbling motility at 25 degrees Aesculin hydrolysed

mada
Download Presentation

Gram Positive Rods

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Gram Positive Rods

  2. Listeria • Small Gram positive rods or coccobacilli (<2μm) • Tolerate wide temperature and pH range • Small haemolytic colonies on blood agar (β haemolysis) • Facultative anaerobes • Catalase positive, oxidase negative • Tumbling motility at 25 degrees • Aesculin hydrolysed • Do not grow on MacConkey agar • Environmental • Outbreaks related to silage

  3. Listeria spp L. monocytogenes meningoencephalitis septicaemia abortion pyogenic infection L. ivanovii abortion, systemic infection L. innocua non-pathogenic L. seeligeri “ L. welshimeri “ L. grayi “

  4. Epidemiology • Common commensal (tonsils, intestine) and environmental organisms • grow at temperatures 4 - 45°C, pH 6.0 - 9.6 • Incidence relates to management/husbandry, (silage feeding), seasonal • predisposed by trauma, immunocompromise, hormonal alterations

  5. Diagnosis • Specimens: • Visceral form: liver, kidney or spleen • Neural form: spinal fluid, brain stem • Abortion: placenta, foetal abomasal contents • Blood smear is not very informative • Isolation: grow aerobically on both blood and MacConkey agars at 37°C for 24-48h • Colonies appear transparent after 24 hours and greyish in 48 hours. Pathogenic strains show β haemolysis • L. Monocytogenes is CAMP +ve with Staph aureus • L. Ivanovii is CAMP +ve with Rhodococcus equi CAMP test

  6. Listeriosis - Ruminants • Meningoencephalitis • Most common form = circling disease (small ruminants) • animal circles in one direction only • unilateral facial paralysis, difficulty in swallowing • fever, blindness, headpressing • paralysis, death in 2 - 3 days

  7. Listeriosis - Ruminants • In pregnant animals, may localize in placentomes • cross-over to amniotic fluid, multiplies • ingested by fetus, causes fetal death, abortion • In milking cows, mammary gland can be involved • subclinical mastitis, contamination of milk • may survive low temp pasteurization inside MØ • lengthy survival in nature • growth at low temperatures • Entry also by nasal mucosa, conjunctivae • Direct access to nervous system via dental plates of trigeminal ganglia

  8. Pathogenesis • tooth loss & cutting naïve/neonatal pregnancy animal •  • oral inoculation epithelial invasion •  • trigeminal nerve bacteraemia •  • brain stem neonatal placentitis •  septicaemia  • meningoencephalitis abortion • “circling disease”

  9. Silage and sheep Listeria encephalitis (bacteria in brain) A –Circling disease in sheep B – Cranial nerve paralysis

  10. Pathogenic mechanisms • Facultative intracellular parasites surviving in macrophages and epithelial cells • Cell uptake induced by bacterial protein internalin (inlA) • Inside the cell they escape the phagolysosome, multiply in the cytoplasm and via actin based motility spread laterally to adjacent cells • They escape epithelium and are taken up by PMN and macrophages • These cells are killed and the organism may spread systemically

  11. Pathogenic mechanisms • Bacteria polymerize actin, form tails • hollow mesh forms on surface, left behind as bacterium moves through cytoplasm, invade adjacent cells • actin depolymerized as organism moves (turnover) • Major virulence factor mediating intracellular survival is a cholesterol binding cytolysin called listeriolysin (LLO) • Shares 40-50% aa similarity to other thiol activated toxins • Mediates escape from phagocytic vesicle

  12. LLO • Cholesterol-directed pore-forming cytolysin (>22 members) • Bind to cholesterol-containing membranes • Insertion • Oligomerization (20-80 mers) • Pore (20-30 nM) formation

  13. Epidemiology of Human Listeriosis • enteric Listeria in animals •  • contamination of carcase, milk or food crops •  • Ingestion (pate, soft cheese, coleslaw) •  • colonisation of tonsils and intestine •  • immunocompetent immunocompromised • (neonate, elderly, pregnancy) •  • asymptomatic septicaemia • meningitis • abortion

  14. Consequences of human L. monocytogenes infection

  15. Associated Foods • Milk products – raw pasteurised • Cheeses • Meat and poultry products – Raw, cooked ready to eat meat and poultry (sporadic and epidemic) • Seafood – fresh, frozen and processed seafood

  16. Consequences of human L. monocytogenes infection • Entry via GI tract, ~ 20 h incubation period • usually asymptomatic/mild, influenza-like symptoms in adult humans, transient gastroenteritis • more serious infection immunocompromised • CNS infections (encephalitis, meningitis), fatal bacteremia • puerperal sepsis • crosses placenta  in utero fetal infection • stillbirths, preterm labor • infant born with systemic infection

  17. Cutaneous listeriosis (in vets) • 17 cases, all with lesions on fore or upper arms, or hands • 16 farmers, veterinarians • 1 butcher • Most developed lesions 1-4 days after attending congenitally infected bovines

  18. Erysipelothrix rhusiopathiae • Gram positive rods (1-2.5μm) • Commensal: widespread in animals, infects man • Grows: 4-37°C • Catalase negative, oxidase negative • Facultative anaerobic, non-motile • Opaque, pin-point, non-haemolytic colonies • infection & disease: mainly in pigs; sheep, turkeys, others • Smooth (S) and rough (R) forms associated with different diseases • Acute septicaemia in pigs, turkeys, sub-acute skin lesions in pigs – S • Chronic arthritis in sheep, endocarditis in pigs - R

  19. Erysipelothrix rhusiopathiae

  20. Pathogenesis commensal: tonsils, RES, bone marrow, many organs mainly R or R/S depression of host defences multiplication of virulent strains (reversion to S?) entry via tonsils or cuts/abrasions invades neutrophils  septicaemia urticarial form arthritis/endocarditis fever malaise persistent anorexia fever erosive DIC DIC chronic inflammation haemorrhage lymphadenitis epidermal lesions fatal ("Diamonds")

  21. Swine erysipelas (diamond skin disease)

  22. Actinomycete Group • Gram positive • Catalase positive • Many are acid fast (mycolic acid in cw) • Slow growing - survive in macrophages • Pleomorphic (coccobacilli to filamentous). Very small (<1μm) • Many saprophytic – some opportunist • Pathogenic genera Actinomyces spp. Nocardia spp. Arcanobacterium spp. Dermatophilus spp. Corynebacterium spp. Eubacterium spp. Rhodococcus spp.

  23. Actinomycete diseases • Pyogenic • Granulomatous • Include: abscesses, pyelonephritis, lymphadenitis, osteomyelitis • Chronic inflammation – focal lesions • Some highly-host adapted • CMI protective – A/bodies mainly non-protective • In vitro - sensitive to some antibacterials • In vivo – poor response - intracellular location

  24. Actinomyces • Actinomyces bovis, Actinomyces viscosus, Actinomyces suis • (Most) non-acid fast branching rods • non-motile • microaerophilic or anaerobic • Colonies are non-haemolytic, small and white • Produce pyogenic, granulomatous reactions - “sulphur granules”

  25. Actinomyces bovis • Normal flora - anaerobic • Thick yellow pus – “sulphur granules” • (occ. confused with wooden tongue) • Causes actinomycosis or Lumpy jaw in cattle (other tissues). Invasion through wound/rough feed/damaged mucosa – Bone infection – osteomyelitis – animal stops eating, loses weight • Soft tissue infection • Mastitis

  26. Actinomyces bovis • Infection endogenous • Organism lives in the mouth normally • Pathology the result of tissue trauma, lesions or prolonged irritation • Treat – lesions small, circumscribed – surgery, abscesses drained, packed with gauze and iodine + penicillin

  27. Gram stain,A. bovis Sulphur granules 48 hour culture, A. bovis

  28. Lumpy Jaw

  29. Actinomyces viscosus • Mainly dogs (cats, pigs, goats, cattle, horses). • Fimbriae - adherence to teeth – plaque • Similar lesions to Nocardia (Nocardia rarely produces granules) • Localised, pyogranulomatous lesions • Two main conditions - Thoracic lesions (pleural, pericardial fluid, lung lesions) and osteomyelitis • Treatment – prolonged Actinomyces suis – mastitis in pigs (sows), trauma initiates disease

  30. Nocardia • Strictly aerobic • Gram-positive, pleomorphic (filaments, rods, cocci – branching) • Widely distributed – soil, water, air, sewage • 0.5 – 1.2 μm in size • Acid fast • Non-motile • Non-spore-forming

  31. Nocardia • 12 species – pathogenic to birds, goats, cats, dogs, fish, horses, cattle and humans • Nocardia asteroides most frequent nocardial pathogen – subcutaneous infections in dogs • N. brasiliensis – pneumonia in horses • Colonies are vivid white – occasionally pigmented

  32. Nocardia

  33. Nocardia • Organism inhaled, in wound or ingested • Direct or haematogenous spread • Prevents phagocytosis • Chronic invasive pyogenic infections (no sulphur granules) • 3 clinical forms – cutaneous, respiratory (pyothorax) and systemic (pyrexia, cough, neurological, resembles distemper) • Dogs – 3x more common in males, Cats – mainly thoracic infection • Treatment: difficult and prolonged – not penicillin

  34. Dog, Nocardia Fluid from chest 4 day culture from fluid

  35. Dermatophilus congolensis • Facultatively anaerobic • Gram positive, non acid fast • filamentous, branching – filaments mature they fragment and release motile flagellate spores • Septation of filaments – zoospores (motile) Beaded, ‘Tram-track’ – the infectious form • CO2chemotactic to zoospores – zoospores germinate form filament form new zoospores – repeating the cycle Pathogenesis • Commensal/spore entry – injury/ wet damage • Colonisation – keratinase production. Aid spread and growth • Strong host response, neutrophil and lymphocyte exudation. • EPIDERMIS ONLY

  36. Dermatophilus congolensis • Dermatitis – cattle, dog, cat, man • Sheep – ‘lumpy wool’, ‘strawberry foot’ • Horse – ‘mud fever’, ‘greasy heel’, ‘rain scald’ • Treatment – Pen/Strep. Tetracyclines • No effective vaccine Dermatophilus in a horse Dermatophilus lesions, SHEEP

  37. Corynebacterium • Small pleomorphic, Gram-positive rods • Chinese letters • Facultatively anaerobic, non-motile • Catalase positive, oxidase negative • Pyogenic • Common commensals • Colonies are white, small, dry, non-haemolytic (except C.pseudotuberculosis). • Genus originally created for the important human pathogen C. diphtheriae, the cause of diphtheria in man

  38. CAMP Test CAMP-Inhibition Test 1. Staphylococcus aureus 2. C.pseudotuberculosis 3. C.renale 4. Rhodococcus equi

  39. Corynebacterial species of veterinary interest C. renale group: • C. renale • C. pilosum • C. cystitidis All cause cystitis and pyelonephritis in cattle Diphtheria group: • C. diphtheriae • C. ulcerans • C. pseudotuberculosis Various diseases of cats, cattle, horses, small ruminants and humans

  40. Corynebacterium renale group • C. renale > C. cystitidis > C. pilosum • Opportunist – highly adapted • Causes cystitis, pyelonephritis, balanoposthitis • Predisposing factors - pregnancy, parturition, post mating • 90% bulls – C. cystitidis - prepuce

  41. Cow with C. renale infection Urine, C. renale C. renale on milk agar

  42. Corynebacterium renale group • Pathogenesis • Adhere to urogenital mucosa • “Stress” • Proliferation • Ascending infection • Inflammation • Cystitis/pyelonephritis • Virulence factors Pili - adherence Renalin - cell lysis Urease Caseinase

  43. The “diphtheria group” • Highly-related (based on DNA hybridisation studies) • C. diphtheriae – diphtheria (humans) • C. pseudotuberculosis – various pyogenic infections • C. ulcerans – nasal congestion (cats), mastitis (cattle) • Susceptible to infection with β-corynephages • C. pseudotuberculosis +C. ulcerans zoonotic pathogens • C. diphtheriae normally only a human pathogen

  44. Corynebacterium diphtheriae • Occasionally isolated from infected wounds in horses (potential environmental reservoir?) • Ironically, horses were the original heroes in fight against diphtheria An illustration from the Nov. 17, 1894, issue of Scientific American, showing doctors drawing blood from a horse to produce antitoxin for diphtheria

  45. Corynebacterium ulcerans • Significant increase in human infections caused by C. ulcerans • Same organism isolated from several domestic cats with bilateral nasal discharge (2002-2003) • Strains isolated from domestic cats were found to exhibit the predominant types observed among human clinical isolates, suggesting that C. ulcerans isolated from cats could be a potential reservoir for human infection

  46. Corynebacterium pseudotuberculosis • C. pseudotuberculosis (pseudes-tuberculosis) • Thought to have spread from Europe with expanding colonial powers • 2 biotypes identified: • “ovis”: non-nitrate reducing, infect sheep/goats (CLA) • “equi”: nitrate reducing, infects predominantly horses

More Related