Microbiology Lesson 19 - Gram-negative Bacteria PDF

Lesson 19 Bacteria of dental interest: Gram -negative spirillum and spirochetes Microbiology PhD. Ana Isabel García Guillén Bachelor in Dentistry Replace this image and adapt the new one to the standardised​ format. Just click right and cut INDEX CONTENTS 1. Fusobacteria 5. Spirochaetes 2. F...

Lesson 19 Bacteria of dental interest: Gram -negative spirillum and spirochetes Microbiology PhD. Ana Isabel García Guillén Bachelor in Dentistry Replace this image and adapt the new one to the standardised​ format. Just click right and cut INDEX CONTENTS 1. Fusobacteria 5. Spirochaetes 2. F. nucleatum 3. Leptotrichia 4. L. buccalis 6. Treponema 7. T. pallidum 8. Oral treponemes 9. Borrelia 10. B. burgdorferi 11. Leptospira spp 2 As a reminder Gram-positive 3 Overview Gram-negative 4 Fusobacteria Generalities • Non-sporing, anaerobic, non-motile, non- or weakly fermentative bacteria • Spindle-shaped bacilli (with fused ends: hence the name) • Inhabitants of the oral cavity, colon and female genital tract • Isolated from pulmonary and pelvic abscesses • Fusospirochaetal infections A photomicrograph of fusobacteria showing characteristic Gram-negative, cigar-shaped cells with pointed ends 5 F. nucleatum Habitat and transmission Several subspecies identified in different habitats • F. nucleatum subsp. polymorphum (healthy gingival crevice) • F. nucleatum subsp. nucleatum (periodontal pockets) • F. nucleatum subsp. vincentii Infections are endogenous 6 F. nucleatum Characteristics • Gram-negative, strictly anaerobic, cigar-shaped bacilli with pointed ends • Often have a central swelling • Biochemical reactions and the acidic end products of carbohydrate metabolism help identification • Remove sulphur from cysteine and methionine to produce odoriferous hydrogen sulphide and methylmercaptan (halitosis) A Gram-stained smear obtained from deep gingival plaque of a patient with acute ulcerative gingivitis showing the fuso-spirochaetal complex. Note: the large cells are PMN 7 F. nucleatum Pathogenicity • Endotoxin (pathogenesis of periodontal disease) • Adherence properties and the fusobacterium adhesin A • Fuso-spirochaetal infections: • Oral spirochaetes (Treponema vincentii and others)*** Acute (necrotizing) ulcerative gingivitis or trench mouth Vincent’s angina (ulcerative tonsillitis causing tissue necrosis) Cancrum oris or noma (sequela of acute ulcerative gingivitis) 8 F. nucleatum Treatment and prevention • Antibiotic and prevention • Fusobacteria are uniformly sensitive to penicillin • Strict anaerobes - sensitive to metronidazole. • Regular oral hygiene and antiseptic mouthwashes are the key to prevention 9 The genus Leptotrichia L. buccalis • • • • • • Oral commensals Gram-negative, strictly anaerobic Slender, filamentous bacilli, usually with one pointed end Leptotrichia buccalis Low proportions in dental plaque Sole representative of this genus 10 Spirochaetes Generalities Diverse group of spiral, motile organisms Three pathogenic genera out of five: Treponema (syphilis, bejel, yaws, pinta, and in the oral cavity) ***(Acute necrotizing ulcerative gingivitis- together with fusobacteria) Borrelia (relapsing fever and Lyme disease) Leptospira (leptospirosis) 11 Spirochaetes Generalities • Cell wall similar to Gram-negative but stains poorly with the Gram stain • Three to five axial filaments fixed to the extremities • Contractions of these filaments give helical shape • Movements by rotation or by flexion • Strictly anaerobic or microaerophilic 12 The genus Treponema T. pallidum • Slender, corkscrew-shaped (6-12 evenly spaced coils) • Can be seen with silver impregnation or immunofluorescent techniques • Strictly anaerobic • Extremely sensitive to drying and heat (dies rapidly outside the body) Treponema pallidum-dark ground illumination 13 T. pallidum Pathogenicity • • • • • Transmission by direct contact with lesions, body secretions, blood, semen and saliva, usually during sexual contact Placental transfer Syphilis (sexually transmitted disease) The virulence factors not well characterized Immunopathology plays a significant role in disease manifestations, especially in the late (tertiary and quaternary) stages of the disease Syphilitic chancre 14 T. pallidum Pathogenicity 15 T. Pallidum Detection • • • • • Cannot be cultured in vitro Can be propagated in the testes of rabbits Treponema pallidum can be used as antigens to detect specific antibody in the patient’s serum. Dark-ground microscopy of tissue fluid from primary and secondary clinical lesions helps identification Serological tests are the mainstay of diagnosis. • Treatment: Penicillin (or tetracycline) • Prevention: early detection 16 T. careteum Pathogenicity • • • • Aetiological agent of pinta Non-venereal skin infection Depigmented and hyperkeratotic skin Mainly dark-skinned natives of Central and South America and the West Indies Typical injuries of pinta disease 17 Oral treponemes Generalities Oral spirochaetes belong to this genus Four have been cultivated: • T. denticola • T. vincentii • T. pectinovarum • T. socranskii Aggressive and chronic periodontitis Aggressive periodontitis 18 Oral treponemes Characteristics • • • • • • • • Motile, helical rods, with irregular spirals (three to eight) Less tightly coiled Gram-negative but stain poorly Variable size used as classification Oral cavity of humans and primates Gingival margin and crevice Transmission unknown Infections are endogenous T. denticola 19 Oral treponemes Characteristics • Oral spirochaetes can be grown in vitro • They are strict anaerobes, slow-growing • Subspecies can be differentiated by fermentation reactions and serology (agglutination). DIAGNOSIS: • Suspect lesions (acute necrotizing ulcerative gingivitis or advanced periodontitis) - examined by Gram-stained smear of deep gingival plaque: characteristic fusospirochaetal complex under light microscopy • Alternatively, dark-ground microscopy may be used 20 Oral treponemes Pathogenicity • • • • • Acute necrotizing ulcerative gingivitis (Vincent’s angina) Advanced periodontal disease Ability to travel through viscous environments, migrate within gingival crevicular fluid and to penetrate sulcular epithelial linings and gingival connective tissue. Virulence factors are little known (endotoxin) T. denticola is more proteolytic than other species and degrades collagen and dentine Acute necrotizing ulcerative gingivitis 21 Oral treponemes Treatment and prevention Penicillin and Metronidazole Good oral hygiene practices 22 Obligately anaerobic Gram-negative Tannerella spp. Porphyromonas spp. Are black-pigmented, anaerobic rods Asaccharolytic pigmented species Major pathogen of periodontal disease Normal oral flora T. forsythia Aggressive agents of periodontal disease P. gingivalis “Red complex" bacteria associated with periodontal disease Tannerella forsythia Treponema denticola Porphyromonas gingivalis 23 Microbial complexes in subgingival plaque SOCRANSKY, S. S., HAFFAJEE, A. D., CUGINI, M. A., SMITH, C. & KENT, R. L., JR. 1998. Microbial complexes in subgingival plaque. J Clin Periodontol, 25, 134‐44. 24 The genus Borrelia B. burgdorferi • Helical spirochaete • Gram-negative microaerophilic • Identification by serology and immunofluorescence 25 B. burgdorferi Pathogenicity Lyme disease Transmitted by ticks and small mammals, and particularly deer Neurological and cardiac manifestations, and arthritis Earliest and most common neurological manifestations Unilateral facial palsy 26 The genus Leptospira • • • • • L. biflexa and L. interrogans (number of serogroups) Stagnant water and wet soil Kidneys of some rodents and domestic animals (zoonosis) Urine serves as a vehicle of transmission Mild febrile illness, fatal attacks of jaundice (high bilirubin levels) and renal failure Dark ground microscopy 27 BIBLIOGRAPHIC REFERENCES Kumar , S. (2016). Essentials of Microbiology. Jaypee Brothers Medical Publishers (P) Ltd. Samaranayake, L. (2012)Essential Microbiology for dentistry .Fourth Edition. Elsevier Ltd. 28 Ana Isabel García Guillén, Ph.D. [email protected] UCAM Universidad Católica de Murcia © © UCAM UCAM