* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Gram Positive Bacilli
Survey
Document related concepts
Biological warfare wikipedia , lookup
Meningococcal disease wikipedia , lookup
Leptospirosis wikipedia , lookup
Bioterrorism wikipedia , lookup
Cryptosporidiosis wikipedia , lookup
Oesophagostomum wikipedia , lookup
African trypanosomiasis wikipedia , lookup
Anthrax vaccine adsorbed wikipedia , lookup
Visceral leishmaniasis wikipedia , lookup
Sexually transmitted infection wikipedia , lookup
Coccidioidomycosis wikipedia , lookup
Neonatal infection wikipedia , lookup
Neisseria meningitidis wikipedia , lookup
Anaerobic infection wikipedia , lookup
Steven Hatfill wikipedia , lookup
Transcript
Gram-positive Bacilli Ken B, Waites, M.D. F(AAM) Professor of Pathology Director of Clinical Microbiology Objectives • To review and discuss: • • • • • microbiological characteristics epidemiology virulence factors associated diseases laboratory detection of clinically important gram-positive bacilli. Organism groups to be discussed include: – – – – – – – Bacillus Listeria Erysipelothrix Corynebacterium Rhodococcus Nocardia Tropheryma Bacillus • • • • • • Ubiquitous in soil worldwide Endospore-forming Aerobic/facultative anaerobic Gram-positive bacilli Can be gram-variable Often hemolytic & motile – (except B. anthracis) • Usually catalase positive B. cereus - Gray, spreading -hemolytic colonies on SBA Bacillus Endospores • Thick walled structures formed by vegetative cells • Resistant to radiation, chemicals, heat, desiccation (dipicolinic acid) • Steam autoclaving necessary for destruction Bacillus: Clinical Significance • Common environmental commensals • Occasional opportunistic pathogens & culture contaminants • B. cereus group • B. anthracis • Others Bacillus cereus Group • Gastroenteritis – Heat-stable enterotoxin (emetic form) – Heat-labile enterotoxin (diarrheal form) • Similar to V. cholera – stimulates cAMP watery diarrhea • Contaminated rice, meat, vegetables • Other Clinical conditions – Ocular infections after trauma • Necrotic toxin, hemolysin, phospholipase C – IV-catheter-related sepsis, endocarditis, meningitis • Immunocompromised persons and drug abusers B. anthracis: Anthrax • • • • • Rare in US due to control in animals Enzootic in middle east Transmitted by contact with animal products eschar Spores remain infectious for years Usually cutaneous inoculation - slow healing ulcer, bacilli spread to lymphatics and bloodstream – 20% mortality if untreated – Respiratory anthrax is usually fatal even if treated – GI anthrax also occurs in some Asian countries • Excellent biological warfare agent Gram stain with spores Anthrax Pathogenesis • Poly-D-glutamic acid (protein) capsule – antiphagocytic • 3 component exotoxin Protective antigen (PA) - binds to cells, forms channel that permits EF and LF to enter Edema factor (EF) – adenyl cyclase causes fluid to accumulate at the site of infection and inhibit immune function Lethal factor (LF) -disrupts cell's functions, stimulates TNF-alpha and IL-1beta, kills infected cells Anthrax Vaccine • Made from avirulent, nonencapsulated B. anthracis strain • Requires series of injections and annual boosters • Used in military Listeria monocytogenes •Gram-positive bacilli/coccobacilli •Catalase-positive •Motile •Esculin positive • hemolytic •Multiplies at 4 o C Umbrella motility • Habitat & Sources of Infection – Intestines of mammals, birds – Cheese, other dairy products – Vegetables – Undercooked meat • Epidemiology & Disease – Asymptomatic carriage – Meningitis/sepsis in immunocompromised host – Foodborne illness – Neonatal infections (transplacental) Listeria: Pathogenesis • Organism adapted to grow at low temperatures • Multiplies in cytoplasm of macrophages and epithelial cells • Listeriolysin O (hemolysin) • Asymptomatic carriage reservoir Erisipelothrix rhusopathiae • Gram-positive bacillus • Common in animals • Transmitted to humans by skin wound • Occupational hazard in butchers, farmers, veterinarians • Self-limited skin lesions with erythema & eruption • May spread to bloodstream Aerobic Actinomycetes • Gram-positive, catalase-positive rods • Occur in soil and decaying vegetation + mycolic acid Mycobacterium Corynebacterium - mycolic acid Nocardia Streptomyces Rhodococcus Tropheryma Others Corynebacterium • • • • • • • • Gram-positive, curved pleomorphic rods “Chinese Letters” Aerobic/facultatively anaerobic Grow readily on Sheep blood agar Catalase & oxidase positive Usually non-motile Commensals on skin Some species pathogenic Diphtheria (C. diphtheriae) • Spreads by droplet • Phospholipase D increases vascular permeability & promotes spread • Phage-coded exotoxin (A&B subunits) acts on respiratory mucous membranes interfering with protein synthesis by inactivating EF-2 • Pseudomembrane of fibrin, bacteria, epithelial & phagocytic cells impairs breathing • Toxin spreads to heart, CNS, & adrenals • Selective media (cysteine-tellurite) • Identify in Public Health Labs • Protect by toxoid vaccination - DaPT • < 5 cases/yr in US Other Pathogenic Corynebacteria • C. jeikeium (JK) – Opportunistic bloodstream infections in bone marrow transplant recipients – Multiple antibiotic resistance - except vancomycin and tetracycline – Commonly carried on skin of hospitalized persons • C. urealyticum – Occasional cause of UTI & stones (splits urea) Nocardia • Epidemiology – Ubiquitous in environment • Inhalation • Cutameous inoculation • Pathogenesis Filamentous gram-positive bacilli – Cord factor – prevents phagolysosome fusion & intracellular killing in phagocytes – Catalase – Superoxide dismutase Partial Acidfast Smear Nocardia Diseases • Opportunist (HIV, Malignancy) – Pneumonia – Lung Abscess – Brain Abscess/Meningitis – Cellulitis/ulceration – Mycetoma Suppurative granulomas Fibrosis Necrosis Sinus tracts Nocardia 6 year-old boy with HIV with 2-month-history of fever & cough. Nocardia Lab Diagnosis • Stained smears • Culture - slow growth ~ 7 days in 5% CO2 • Several species associated with human disease • Identify by PCR Nocardia colonies Middlebook 7H11 agar Aerial hyphae Rhodococcus equi • Gram-positive weakly acidfast bacilli that sometimes revert to coccoid forms • Common in animals & environment • Opportunistic lung infections in AIDS & transplant patients • Facultative intracellular pathogen that survives in macrophages, leading to granuloma & abscess Slow-growing, mucoid salmon-colored colonies of R. equi on chocolate agar Tropheryma whippeli • Actinomycete etiologic agent of Whipple’s Disease – a malabsorptioin syndrome affecting the small bowel • Organism cannot be cultured except in tissue culture • Diagnose by histopathology & PCR