Mycobacteria_and_Related_Acid_Fast_Resp1_5155_2023_Benson.pptx

Mycobacteria and Related Acid-Fast Bacteria 5155: Respiratory System I December 4th, 2023 8 - 9 AM CDC Image #23000 Marc Benson, Ph.D. • • • • Office: 317 E-mail: [email protected] Phone: (575) 674-2317 Office Hours: By appointment or stop by office Reading Material Murray et al. Medical Micro...

Mycobacteria and Related Acid-Fast Bacteria 5155: Respiratory System I December 4th, 2023 8 - 9 AM CDC Image #23000 Marc Benson, Ph.D. • • • • Office: 317 E-mail: [email protected] Phone: (575) 674-2317 Office Hours: By appointment or stop by office Reading Material Murray et al. Medical Microbiology, 8th ed. Chapter 22: Mycobacterium and Related Acid-Fast Bacteria 1 Copyright Notice • All reproduction or use of copyrighted materials shall comply with provisions of applicable law. Individuals are responsible for maintaining copyright compliance in good faith and with each intended use. Please consult BCOM Policy B5041 and the copyright guidelines located on https://bcomnm.org/copyrightguidelines/ for detailed information • BCOM prohibits duplication, distribution, or use of copyrighted materials by students, faculty and staff unless a fair use or other exemption applies, or permission has been obtained from the work's rights holder (which may or may not be the author/creator) • Infringement of copyright law may be considered a violation of the College’s Code of Professional Conduct. Anyone found liable for civil and/or criminal copyright infringement may be responsible for any monetary damages suffered by the College due to such violation(s) of this policy or related law or regulation Lecture Outline Mycobacterium tuberculosis Mycobacterium leprae Mycobacterium avium complex Nocardia spp. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Pre-Lecture Clicker Questions Objectives General Information Epidemiology Virulence Factors and Pathogenesis Disease Laboratory Diagnostics Summary Slide Clicker Post-Lecture Questions Learning Catalytics Questions 3 Pre-Lecture Clicker Questions Lecture Outline Mycobacterium tuberculosis Mycobacterium leprae Mycobacterium avium complex Nocardia spp. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Pre-Lecture Clicker Questions Objectives General Information Epidemiology Virulence Factors and Pathogenesis Disease Laboratory Diagnostics Summary Slide Clicker Post-Lecture Questions Learning Catalytics Questions 5 Objectives • • • • • • • List the key physiological and growth characteristics of mycobacteria Describe the pathogenesis of M. tuberculosis infection and the processes involved in generation of a granuloma Compare and contrast the laboratory methods used to diagnose tuberculosis List the drugs most commonly used to treat tuberculosis Describe the epidemiology and clinical manifestations of disease caused by M. leprae and M.avium complex Recognize the morphology of Nocardia in culture Describe the most common clinical manifestations of Nocardia infection 6 Lecture Outline Mycobacterium tuberculosis Mycobacterium leprae Mycobacterium avium complex Nocardia spp. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Pre-Lecture Clicker Questions Objectives General Information Epidemiology Virulence Factors and Pathogenesis Disease Laboratory Diagnostics Summary Slide Clicker Post-Lecture Questions Learning Catalytics Questions 7 Mycobacterium tuberculosis General Biology • Mycobacterium tuberculosis complex • M. tuberculosis • M. leprae • M. africanum • M. bovis • M. bovis BCG (bacilli Calmette-Guérin strain) Disease • M. tuberculosis can involve any organ; most infections are restricted to the lungs in immunocompetent individuals • Tuberculosis was called consumption cal-met gay-ran • Cell wall includes mycolic acids • Lipid, waxy; clumpy appearance on stain • Resistant to drying Kinyoun stain; an acid-fast stain Murray, Patrick R., PhD, Medical Microbiology, Chapter 22, Copyright © 2021, Elsevier Inc. All rights reserved. • M. tuberculosis – aerobic, acid-fast, intracellular rods • Gram positive • Nonmotile • Does not form spores • Gram stain not useful due to mycolic acids, so use acid-fast stain • Very slow growth (8 weeks; ~24 hour doubling time) 8 Mycobacterium tuberculosis Epidemiology Ziehl-Neelsen Stain; an acid-fast stain CDC Image #23000 • Humans are the only natural reservoir • Estimated 25% of world population infected • WHO - 2018 - 10 million new infections; 1.5 million deaths • 0.5 million infected with drug-resistant TB • In U.S. - 2018 - ~9,000 new infections • Highest in California, New York, New Jersey, Texas, Florida • Transmission • • Inhalation of infectious aerosolized droplet • Large particles trapped and removed by mucociliary escalator • Small particles reach alveolar space to establish infection Infection established with 1-200 bacilli (low infectious dose) Estimated TB incidence rates, 2021 • Patient Risk Factors • • • • • • • ~60% cases - foreign-born in U.S. Homeless individuals Individuals that abuse drugs and alcohol Prisoners HIV+ individuals Individuals who work with the above Impaired immunity 9 Global tuberculosis report 2022 WHO Mycobacterium tuberculosis Virulence Factors • Major virulence mechanisms: • Prevention of phagosome-lysosome fusion • Survive and replicate in phagosome • Mycobacterial lipids • Lipoarabinomannan (LAM) • Limits maturation of phagosomes • Mannose-capped (ManLAM) – attachment to mannose receptor and DC-SIGN ESX/EsxA Macrophage • Sulfolipid • Inhibits phagosome-lysosome fusion • Cord factor (trehalose-6,6’-dimycolate; TDM) • Responsible for the serpentine (cord-like) growth pattern in vitro • Inhibits phagosome-lysosome fusion • Induces TNFα production • Granuloma formation Mycobacterial proteins • Protein tyrosine phosphatase (PtpA) – Interacts with the host vacuolar H+ ATPase and the vacuolar protein sorting protein to prevent membrane fusion and phagosome acidification Modified from Stutz MD. Mycobacterium tuberculosis: Rewiring host cell signaling to promote infection. J Leukoc Biol. 2018 Feb;103(2):259-268. • 10 Mycobacterium tuberculosis Virulence Factors Modified from Stutz MD. Mycobacterium tuberculosis: Rewiring host cell signaling to promote infection. J Leukoc Biol. 2018 Feb;103(2):259-268. • Type VII Secretion System (ESX-1) • Secretes factors (EsxA; ) into phagosomal lumen • Promotes membrane rupture • Enhances inflammatory response by allowing bacteria to get detected by host cytoplasmic DNA sensor (see next page) 11 Mycobacterium tuberculosis Pathogenesis - Innate Immunity Immune Evasion Strategy • Recognition by pattern recognition receptors (PRRs) on alveolar MΦ • Mannose receptors, DC-SIGN, complement receptors, scavenger receptors, Fc receptors, TLRs, NLRs • Since mycobacteria are intracellular, initial recognition by host cells is necessary • Antimicrobial pathways activated • Vitamin D pathway enhances antimicrobial activity (see directed study on immunodeficiencies for more info) • Proinflammatory cytokines and chemokines produced • PMN, monocyte recruitment • • • In phagosomes/lysosomes, • ROS and NO-mediated killing • • • • M. tuberculosis can replicate in PMNs Monocytes differentiate to MΦ or DCs and utilized for dissemination to pulmonary lymph nodes Inflammation involved in tissue damage Initially prevents NF-κB signaling to prevent cytokine response Neutralizes ROS/NO Prevents phagosome-lysosome fusion (LAM, sulfolipid, cord factor, PtpA) • In cytoplasm, • Cytoplasmic DNA sensors (CDS) recognize mycobacterial • Promotes inflammation and immune cell DNA and trigger autophagy (mechanism by which vacuole recruitment forms within cytosol and eliminates cytoplasmic components) • In susceptible individuals, NK cell activity • Natural Killer (NK) cells lower. Also IL-10-mediated suppression • Recognize infected cells and kill them 12 Mycobacterium tuberculosis Pathogenesis - Innate Immunity • Inflammation • As with any infection, the balance of the inflammatory response is critical - this avoids excessive tissue destruction while fighting the infection • Unregulated high inflammation • ↑ transmission of bacteria • More lung cavitation • Low inflammation • Unregulated infection • • TNFα – a major proinflammatory cytokine in M. tuberculosis elimination • Involved in granuloma maintenance Apoptosis versus necrosis of host cell • Apoptosis limits bacterial dissemination (M. tuberculosis prevents apoptosis) • Necrosis enhances bacterial dissemination • TNFα Function: • Secreted by MΦ and T cells • Vascular endothelial cells increase E- selectin (low affinity adhesion for circulating PMNs and monocytes) • Integrin become high affinity on PMNs • Induces production of acute phase proteins from hepatocytes • Induces fever Mycobacterium tuberculosis Pathogenesis – Antigen Presentation • Antigen Presentation • Dendritic cells (DC), antigen presenting cells, infected with M. tuberculosis, migrate to draining lymph nodes to present, on MHCII, antigen to naïve T cells • Bacterial cells can also migrate to lymph nodes, get recognized by resident APCs, and antigen presented to naïve T cells • Immune evasion • M. tuberculosis impairs antigen presentation in APC APC activation of naïve T cell Costimulation is a central principle in T cell activation as the TCR recognition of the MHCII-antigen complex is not sufficient to activate the naïve T cell DC Activation of naive T cells requires interaction of : 2 1 1) TCR:MHCII-peptide complex AND 2) CD28:B7 costimulatory molecules Without costimulation: • The T cell becomes anergic (unresponsive to antigen), a type of peripheral tolerance Immune Receptors and Signal Transduction Abbas, Abul K., MBBS, Cellular and Molecular Immunology, Chapter 7, 145-178 Copyright © 2018 Copyright © 2018, 2015, 2012, 2007, 2005, 2003, 2000, 1997, 1994, 1991 by Elsevier, Inc. 14 Mycobacterium tuberculosis Pathogenesis – Adaptive Immunity • CD8+ T cells also play a role in M. tuberculosis elimination • Main feature is to limit reactivation • Two methods of target cell killing • Perforin/granzyme-mediated cell killing • Perforin is released and forms pores in target membrane • Granzymes (serine proteases) enter the host cell and targets multiple proteins, including caspases, which initiate apoptosis • Fas/FalL-mediated cell killing • Activated CTLs express the Fas ligand (FasL) which recognizes Fas on target cells • The FasL:Fas interaction signals the target cell to undergo apoptosis 15 Mycobacterium tuberculosis • The CD4+ T cell response, specifically Th1 cells, is a key factor in controlling Mycobacterium tuberculosis • IFN-γ and IL-12 are additional key cytokines essential for M. tuberculosis elimination • This cell mediated immune response is responsible for the formation of granulomas (non-replicating bacteria) Infected MΦ Classical MΦ activation M1 IFN- γ Th1 -γ N IF -12 IL Fib ro bla st • Macrophage-mediated killing of intracellular pathogens Th0 naïve T cell Granuloma APC • Classical pathway of MΦ activation (M1 macrophage) • MΦ with ingested bacteria upregulate the costimulatory CD40 molecule, MHCII presentation, and the IFN-γ receptor • Th1 cells engage the MΦ through TCR and CD40L receptors and secrete IFN-γ • IFN-γ mediated activation induces the MΦ to: • Enhance phagolysosomal killing • Secrete proinflammatory cytokines • Increase B7 costimulatory molecules for subsequent naive T 16 cell activation Abbas, Abul K., MBBS, Cellular and Molecular Immunology, Copyright © 2018 Copyright © 2018, 2015, 2012, 2007, 2005, 2003, 2000, 1997, 1994, 1991 by Elsevier, Inc. Pathogenesis – Adaptive Immunity Mycobacterium tuberculosis Pathogenesis – Reactivation • Reactivation of a latent infection is due to the multiplication and escape from the granuloma • Process not well characterized, but this is what is known: • CD4+ T cell depletion • TNFα impairment Fib ro bla st • Individual highly infectious (high transmission) Granuloma Mycobacterium tuberculosis Disease Latent TB • Not active infection; no symptoms • • • • Primary TB First exposure Flu-like symptoms Ghon focus Three outcomes • Heal • Progressive TB • Latent TB • • Ghon focus –area of inflammation, often with central necrosis Ghon complex – combination of lung lesion with lymph node involvement Caseation – necrotic tissue that resembles soft cheese • • • • • • Progressive Primary TB No latency Resembles bacterial pneumonia Heavy pulmonary involvement Children < 5 and AIDS patients Secondary/Reactivation TB Second exposure or reactivation Fever, hemoptysis (blood in sputum), cough, unexplained weight loss, night sweats, trouble breathing Upper lobes of lung affected Rapid caseation due to hypersensitivity reaction Miliary TB • Spread of bacteria to other parts of body • Formation of tubercules (lesions) 18 Frank, Karen M., Robbins & Cotran Pathologic Basis of Disease, Chapter 8, Copyright © 2021 by Elsevier, Inc. All rights reserved. Mycobacterium tuberculosis Laboratory Diagnostics Microscopy Acid fast stain – used to stain Mycobacterium • Ziehl-Neelsen stain Basic carbolfuchsin penetrates mycolic acids • Kinyoun stain • Auramine-rhodamine – fluorescent stain of mycolic acids Gram positive but Gram stain not useful Carbolfuchsin Acid alcohol Methylene blue CDC Image #23000 Acid fast stains Carbolfuchsin (red/purple dye) Acid alcohol wash (decolorization) Methylene blue (green counter stain) • Nucleic acid tests have been developed 19 Mycobacterium tuberculosis Laboratory Diagnostics Culture methods • M. tuberculosis grows very slow (~24 hours doubling time) • For sputum samples, the contaminating bacteria are removed by a decontaminating agent (i.e. NaOH) • Specialized medium • Lowenstein-Jensen medium • Malachite green – prevents growth of other organisms that may have survived decontamination • Egg suspension – fatty acids and protein; also provides solid surface for growth (coagulation of albumin) • Middlebrook medium • Agar used for solid surface instead of egg • Colony shape • Colorless, raised with wrinkled surface and irregular edges CDC# 16484 Mycobacterium tuberculosis Laboratory Diagnostics Tuberculin/PPD/Mantoux test • Individuals who have had Mycobacterium tuberculosis infection have produced memory CD4+ T cells to mycobacterial antigens – results in a type IV hypersensitivity reaction • Exposure to PPD (tuberculin purified protein derivative) will activate these memory CD4+ T cells, release proinflammatory cytokines, and recruit macrophage, resulting in an indurated skin lesion 48-72 hours later •Type IV hypersensitivity is also delayed type hypersensitivity (DTH) •Cell-mediated reaction • Th1, Th2, CTL (CD8+) •2 days to weeks post exposure An Overview of Best Practice Guidelines for Mycobacterium tuberculosis Screening and Treatment Ivansek, Nancy, PA-C, MA, Physician Assistant Clinics, Volume 2, Issue 2, 219-227 Copyright © 2016 Elsevier Inc. Abbas, Abul K., MBBS, Cellular and Molecular Immunology, Copyright © 2018 Copyright © 2018, 2015, 2012, 2007, 2005, 2003, 2000, 1997, 1994, 1991 by Elsevier, Inc. 21 Mycobacterium tuberculosis Vaccine • The BCG (Bacillus Calmette-Guerin) vaccine is a live attenuated stain of M. bovis • Not used in the U.S. • PPD test is positive in vaccinated individuals, the IGRA are not • Most effective against disseminated TB in children • Administered via the intradermal route 22 Mycobacterium tuberculosis General • • • • • Aerobic, acid-fast, intracellular rods Nonmotile, non-spore forming Slow growth (~24 hr doubling time) Cell wall includes mycolic acids Gram positive but stain not useful Summary Pathogenesis • Epidemiology • • • • Human natural reservoir 25% world population infected Transmission • Infectious aerosolized droplets Low infectious dose Risk factors • • HIV positive, immunodeficient, in U.S., foreign born, alcohol/drug abuse, living in close proximity Working with the above Vaccine • Live attenuated M. bovis BCG (Bacillus Calmette-Guerin) vaccine • Most effective against disseminated TB in children Immune evasion • Replicate in APCs and PMNs, neutralize ROS/NO, prevents inhibits phagosomelysosome fusion, NK cell population low, Impairs antigen presentation • • Virulence factors • Liparabinomannan (LAM) – limits maturation of phagosomes • Sulfolipid – inhibits phagosome-lysosome fusion • Cord factor (trehalose dimycolate) - Serpentine (cord-like) growth, inhibits phagosome-lysosome fusion, TNFα-mediated granuloma formation • Type VII secretion system (ESX-1) - promotes phagosomal membrane rupture, enhances TNFα production Disease CD4+ Th1 and CD8+ major cells for elimination IFN-γ, IL-12, and TNFα major cytokines for elimination Lab Diagnosis • Acid fast stains (Ziehl-Neelsen, Kinyoun) • Nucleic acid test • Culture Methods • Slow growth • Lowenstein-Jensen and Middlebrook media • Colony shape – colorless, raised with wrinkled surface and irregular edges • Tuberculin/PPD/Mantoux test • PPD (M.tb antigen) activates memory CD4+ T cells • Type IV hypersensitivity reaction • BCG vaccinated patients will be positive • IFN-γ release assay • Measures IFN-γ produced by sensitized T cells stimulated by M.tb antigen • BCG vaccinated patients will be negative • General Symptoms • Persistent cough with mucus • Dyspnea • Chest pain • Hemoptysis (cavitary disease; tissue destruction) • Weight loss • Fatigue • Night sweats 23 Lecture Outline Mycobacterium tuberculosis Mycobacterium leprae Mycobacterium avium complex Nocardia spp. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Pre-Lecture Clicker Questions Objectives General Information Epidemiology Virulence Factors and Pathogenesis Disease Laboratory Diagnostics Summary Slide Clicker Post-Lecture Questions Learning Catalytics Questions 24 Mycobacteria leprae General Biology and Epidemiology Mycobacteria leprae - aerobic, acid-fast, obligate intracellular rods • Nonmotile • Non-spore forming • Prefers lower temperature of body • Extremely slow growth (doubling time ~14 days) Acid-fast stain – skin tissue specimen Cell wall includes mycolic acids • Gram positive but Gram stain not useful; use acid-fast stain Disease • Causes leprosy, or Hansen disease, a chronic granulomatous infection of the skin and peripheral nerves Epidemiology • 90% of cases in Brazil, Madagascar, Mozambique, Tanzania, Nepal • In U.S., 50 diagnosed per year • Armadillos are naturally infected • Mycobacteria lepromatosis endemic in Mexico CDC Image #17322 Transmission • Believed to include close contact with an infected individual over months • Believed to be transmitted by infectious aerosolized droplets 25 Mycobacteria leprae Virulence Factors and Pathogenesis • Not as much known as M. tuberculosis • Targets macrophage and Schwann cells • Cannot replicate outside of cells – obligate intracellular • TLR1 and TLR2 on Schwann cells recognize M. leprae and apoptosis results • M. leprae PGL-1 (phenolic glycolid-1) associates with macrophage and induces nitric oxide, which may play a role in peripheral neuropathy 26 Mycobacteria leprae • Leprosy (Hansen disease) Disease • Disease of skin and nerves • Replicates primarily in relatively cool tissue: hands and face • Two types, determined by T cell response (Th1 vs Th2) : Lepromatous Leprosy Tuberculoid Leprosy • • • • • Few dry scaly skin lesions that lack sensation • Th1 response • Neuronal involvement • Paucibacillary (low number of organisms) Claudio Guedes Salgado, M.D., and Josafa Goncalves Barreto, M.D. Leonine Facies: Lepromatous Leprosy, N Engl J Med 2012; 366:1433 Multiple lesions, nodules Th2 response Sensory loss Disfiguring • Lesions may ulcerate • Leonine facies • Multibacillary (many, many organisms) CDC 19222 Leonine facies UptoDate 82693 CDC 19225 Mycobacteria leprae Laboratory Diagnostics • Does not grow in cell-free medium • Histopathology of biopsy specimens (main lab diagnostic) • Acid-fast stains • Few bacteria (paucibacillary) in tuberculoid leprosy • Many bacteria (multibacillary) in lepromatous leprosy (red snapper) • NAAT Acid-fast stain from skin smear Histopathology of skin tissue – acid fast stain 28 Mycobacterium leprae Summary General • Aerobic, acid-fast, obligate intracellular rods • Nonmotile, non-spore forming • Causes leprosy, or Hansen disease, a chronic granulomatous infection of the skin and peripheral nerves • Slow growth (doubling time ~14 days) • Prefers lower temperature of body • Cell wall includes mycolic acids • Gram positive but not useful stain Immunology M2 Tuberculoid Lepromatous Epidemiology • 90% of cases in Brazil, Madagascar, Mozambique, Tanzania, Nepal • In U.S., 50 diagnosed per year Lab Diagnostics • Armadillos are naturally infected • • Does not grow in cell-free medium Acid-fast stains • Few bacteria (paucibacillary) in tuberculoid leprosy • Many bacteria (multibacillary) in lepromatous leprosy • 2 disease manifestations • Tuberculoid - ↑ Th1, INF-γ • Lepromatous - ↑ Th2, IL-4 Transmission • Believed to include close contact with an infected individual over months • Believed to be transmitted by infectious aerosolized droplets Disease Pathogenesis • Similar to M. tuberculosis, although virulence factors differ • M. leprae also infects Schwann cells 29 Lecture Outline Mycobacterium tuberculosis Mycobacterium leprae Mycobacterium avium complex Nocardia spp. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Pre-Lecture Clicker Questions Objectives General Information Epidemiology Virulence Factors and Pathogenesis Disease Laboratory Diagnostics Summary Slide Clicker Post-Lecture Questions Learning Catalytics Questions 30 Mycobacterium avium complex Summary General • Includes M. avium and M. intracellulare • May see MAC or MAIC • Acid-fast, intracellular rods • Nonmotile, non-spore forming • Slow growth • Cell wall includes mycolic acids • Opportunistic pathogen Pathogenesis • Biofilm a virulence factor • Translocation across epithelial layer to infect MΦ • Similar to M. tuberculosis, although virulence factors differ Epidemiology • Ubiquitous in the environment • Forms biofilms • Resistant to antibiotics and disinfectants • In U.S., opportunistic infection in immunocompromised (seen more than M.tb and M. leprae) Lab Diagnostics • Colonies • Smooth from clinical isolates • Rough from environment • Molecular methods • Nucleic acid tests • PCR restriction fragment analysis Transmission • Inhalation, ingestion, dermal contact Disease • Pulmonary infection most common (solitary nodule common) • In AIDS patients, disseminated disease with high bacterial burden • Lady Windermere syndrome (Oscar Wilde play) -rare • Elderly non-smoking females • Lingular/middle lobe infiltrates with patchy, nodular appearance • Few symptoms with high mortality/morbidity Risk Factors • Pulmonary disease (COPD, cystic fibrosis) • Smokers • AIDS patients (low T cells) 31 FYI M. marinum • Causes fish tank granuloma (aquarium granuloma) • Clusters of superficial nodules/papules Cream-colonies • Turn yellow when exposed to light (photochromogenic) VisualDx: ID:636567 • Acid-fast stain from skin 32 Lecture Outline Mycobacterium tuberculosis Mycobacterium leprae Mycobacterium avium complex Nocardia spp. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Pre-Lecture Clicker Questions Objectives General Information Epidemiology Virulence Factors and Pathogenesis Disease Laboratory Diagnostics Summary Slide Clicker Post-Lecture Questions Learning Catalytics Questions 33 Nocardia spp. General Biology and Epidemiology • Nocardia asteroides, N. brasiliensis, N. caviae • Gram positive rods that form branched filaments • Weak acid fast staining due to tuberculostearic acid and short mycolic acids • Differentiates from Actinomyces • Aerobic • Catalase positive • Found worldwide in soil, decaying matter, and water • Exogenously acquired by inhalation, traumatic introduction, or ingestion • Risk factor • Immunocompromised individuals Mycobacterium and Related Acid-Fast Bacteria. Murray, Patrick R., PhD, Medical Microbiology, Chapter 22, 218-233.e1 Copyright © 2016, Elsevier Inc. All rights reserved. Nocardia spp. Virulence Factors and Pathogenesis • Major pathogenic mechanism is to avoid phagolysosomal killing • Survive oxidative burst of immune cells by catalase and superoxide dismutase production • Survival and replication in macrophage mediated by: • Cord factor (trehalose dimycolate glycolipid) • Prevent acidification of lysosome Nocardia spp. Clinical Disease • Bronchopulmonary disease • Generally seen in immunocompromised patients • Pneumonia - dyspnea, fever, and cough • Cavitation with spread to pleura • Dissemination to CNS or skin common http://www.neurorad.org/nrr/nrr/b106/dx.htm • Causes nocardiosis abscess • Cutaneous infection • Mycetoma (usually in the foot) - painless, chronic infection with subcutaneous swelling and sinus tract formation • Lymphocutaneous infection • Cutaneous nodules and ulcerations along the lymphatics (resembles sporotrichosis; Sporothrix shenckii) • Brain abscess • Single or multiple abscess formation • May present as chronic meningitis initially Nocardia spp. Laboratory Diagnostics • When cultured, slower growing on most medium (5-7 days) • Growth on BCYE (buffered charcoal yeast extract) – prevent growth of commensals • Colonies may form aerial hyphae • If Gram stain is performed, branched filaments • If acid-fast stain is performed, weakly positive • Catalase positive aerial hyphae Mycobacterium and Related Acid-Fast Bacteria. Murray, Patrick R., PhD, Medical Microbiology, Chapter 22, 218-233.e1 Copyright © 2016, Elsevier Inc. All rights reserved. Mycobacterium and Related Acid-Fast Bacteria. Murray, Patrick R., PhD, Medical Microbiology, Chapter 22, 218-233.e1 Copyright © 2016, Elsevier Inc. All rights reserved. Nocardia spp. General Characteristics Summary • Gram positive rods that form branched filaments • Aerobic, catalase positive • Stain weakly acid fast due to tuberculostearic acid and short mycolic acids Epidemiology • • • Worldwide in soil, decaying matter, and water Exogenously acquired Immunocompromised at risk Virulence Factors/Pathogenesis • Avoid phagolysosomal killing by producing catalase and SOD • Survival and replication in macrophage • Cord factor (trehalose dimycolate glycolipid) to prevent fusion of the phagosome and lysosome Lab Diagnostics • • • • Slower growing on most medium and BCYE Colonies may form aerial hyphae Weakly positive acid-fast branched filaments Catalase positive Disease • Causes nocardiosis • Bronchopulmonary disease Generally seen in immunocompromised patients Pneumonia dyspnea, fever, and cough Cavitation with spread to into pleura Dissemination to CNS or skin common • Cutaneous infection Mycetoma (usually in the foot) - painless, chronic infection with subcutaneous swelling and sinus tract formation • Lymphocutaneous infection Cutaneous nodules and ulcerations along the lymphatics (resembles sporotrichosis; Sporothrix shenckii) • Brain abscess Single or multiple abscess formation May present as chronic meningitis initially Lecture Outline Mycobacterium tuberculosis Mycobacterium leprae Mycobacterium avium complex Nocardia spp. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Pre-Lecture Clicker Questions Objectives General Information Epidemiology Virulence Factors and Pathogenesis Disease Laboratory Diagnostics Summary Slide Clicker Post-Lecture Questions Learning Catalytics Questions 39 Clicker Post-Lecture Questions And Learning Catalytics Questions TBD 40 Thank you! 41