Microbiology Lesson 18: Gram-negative Bacteria PDF

Lesson 18 Bacteria of dental interest: strict anaerobic Gram-negative Microbiology PhD. Ana Isabel García Guillén Bachelor in Dentistry Contents Bacteroides B. fragilis Tannerella T. forsythia Porphyromonas P. gingivalis Prevotella P. intermedia As a reminder Gram-positive 3 Overview Gram-ne...

Lesson 18 Bacteria of dental interest: strict anaerobic Gram-negative Microbiology PhD. Ana Isabel García Guillén Bachelor in Dentistry Contents Bacteroides B. fragilis Tannerella T. forsythia Porphyromonas P. gingivalis Prevotella P. intermedia As a reminder Gram-positive 3 Overview Gram-negative 4 Obligately anaerobic Gram-negative Bacteroides spp. Porphyromonas spp. Found predominantly in the gut Asaccharolytic pigmented species Most common agents of serious anaerobic infections Normal oral microbiota B. fragilis P. gingivalis Tannerella spp. Are black-pigmented, anaerobic rods Agents of periodontal disease Prevotella spp. Major pathogen of periodontal disease Saccharolytic Oral and genitourinary species T. forsythia Some species are periodontopathic Black-pigmented anaerobes (Tannerella, Porphyromonas and Prevotella species) "red complex" bacteria associated with periodontal disease T. forsythia, Treponema denticola and P. gingivalis 5 The genus Bacteroides B. fragilis • Most predominant microbiota in the intestine (1011 cells/gr of faeces) • Serious anaerobic infections such as intra-abdominal sepsis, peritonitis, liver and brain abscesses, and wound infection • Strictly anaerobic, Gram-negative, non-motile, nonsporing bacilli • Polysaccharide capsule is an important virulence factor 6 B. fragilis Pathogenicity • Infections are endogenous and diseases impossible to prevent • Endotoxin and proteases • Many infections are polymicrobial in nature • Facultative anaerobes coliforms can utilize oxygen and facilitate the subsequent growth of Bacteriodes • Sensitive to metronidazole and clindamycin • βlactamase production • Resistant to penicillins, first-generation cephalosporins and aminoglycosides 7 The genus Tannerella T. forsythia • Supragingival and subgingival sites (more common in the latter) • Degree of isolation related to increasing pocket depth • Recovered from sites that converted from periodontal health to disease and sites with periodontal breakdown • Non-motile, pleomorphic, spindle-shaped Gram-negative rods 8 T. forsythia Pathogenicity • Periodontal pathogen in both human and animals • Induces apoptotic cell death • Invades epithelial cells in vitro and in vivo • Virulence factors: endotoxin, fatty methylglyoxal acid and 9 The genus Porphyromonas P. gingivalis • Solely at subgingival sites, particularly in advanced periodontal disease • It is sometimes recovered from the tongue and tonsils • Non-motile, asaccharolytic, short, pleomorphic, Gram-negative coccobacilli 10 P. gingivalis Pathogenicity • Aggressive periodontal pathogen in both humans and • animals • Fimbriae mediate adhesion • Capsule defends against phagocytosis • Collagenase, endotoxin, fibrinolysin, phospholipase A, proteases that destroy immunoglobulins, gingipain • Fibroblast-inhibitory factor • Complement and haem-sequestering proteins Haemolysin 11 P. gingivalis Pathogenicity Fandiño V, Muñoz E, Parra A, Salgado Y. 2013 12 The genus Prevotella Generalities • • • • Human oral cavity P. intermedia associated with periodontal disease P. nigrescens isolated more often from healthy gingival sites Non-motile, short, round-ended, Gram-negative rods 13 P. intermedia Pathogenicity • Shares virulence properties of P. gingivalis • “Orange complex” that precedes the arrival of the “red complex” group of bacteria • Oral non-pigmented species are isolated in occasion on healthy subgingival plaque. 14 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. 15 REFERENCIAS BIBLIOGRÁFICAS Kumar , S. (2016). Essentials of Microbiology. Jaypee Brothers Medical Publishers (P) Ltd. Samaranayake, L. (2012)Essential Microbiology for dentistry .Fourth Edition. Elsevier Ltd. 16 Ana Isabel García Guillén [email protected] UCAM Universidad Católica de Murcia © UCAM © UCAM