tailieunhanh - Chapter 131. Diphtheria and Other Infections Caused by Corynebacteria and Related Species (Part 6)

Microbiology and Laboratory Diagnosis These organisms are non-acid-fast, catalase-positive, aerobic or facultatively anaerobic bacilli. Their colonial morphologies vary widely; some species are small and α-hemolytic (similar to lactobacilli), whereas others form large white colonies (similar to yeasts). Many nondiphtherial coryneforms require special medium (., Löffler's, Tinsdale's, or telluride medium) for growth. Epidemiology Humans are the natural reservoirs for several nondiphtherial coryneforms, including C. xerosis, C. pseudodiphtheriticum, C. striatum, C. minutissimum, C. jeikeium, C. urealyticum, and A. haemolyticum. Animal reservoirs are responsible for carriage of A. pyogenes, C. ulcerans, and C. pseudotuberculosis. Soil is the natural reservoir for R. equi. . | Chapter 131. Diphtheria and Other Infections Caused by Corynebacteria and Related Species Part 6 Microbiology and Laboratory Diagnosis These organisms are non-acid-fast catalase-positive aerobic or facultatively anaerobic bacilli. Their colonial morphologies vary widely some species are small and a-hemolytic similar to lactobacilli whereas others form large white colonies similar to yeasts . Many nondiphtherial coryneforms require special medium . Loffler s Tinsdale s or telluride medium for growth. Epidemiology Humans are the natural reservoirs for several nondiphtherial coryneforms including C. xerosis C. pseudodiphtheriticum C. striatum C. minutissimum C. jeikeium C. urealyticum and A. haemolyticum. Animal reservoirs are responsible for carriage of A. pyogenes C. ulcerans and C. pseudotuberculosis. Soil is the natural reservoir for R. equi. C. pseudodiphtheriticum is part of the normal flora of the human pharynx and skin. C. xerosis is found on the skin nasopharynx and conjunctiva C. auris in the external auditory canal and C. striatum in the anterior nares and on the skin. C. jeikeium and C. urealyticum are found in the axilla groin and perineum particularly in hospitalized patients. C. ulcerans and C. pseudotuberculosis infections have been associated with the consumption of raw milk from infected cattle. Specific Nondiphtherial Coryneforms C. ulcerans This organism causes a diphtheria like illness and produces both diphtheria toxin and a dermonecrotic toxin. C. ulcerans is a commensal in horses and cattle and has been isolated from cow s milk. The organism causes exudative pharyngitis primarily during summer months in rural areas and among individuals exposed to cattle. In contrast to diphtheria C. ulcerans infection is considered a zoonosis and person-to-person transmission has not been firmly established. Nevertheless treatment with antitoxin and antibiotics should be initiated when respiratory C. ulcerans is identified and a contact investigation .

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