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article_Typhoid Mary
Mary Mallon, now known as Typhoid Mary, seemed a healthy woman when a health inspector knocked on her door in 1907, yet she was the cause of several typhoid outbreaks. Since Mary was the first "healthy carrier" of typhoid fever in the United States, she did not understand how someone not sick could spread disease -- so she tried to fight back.

Salmonella typhi (Salmonella enterica subsp. enterica serovar Typhi)

  • General information

    • the following information is not yet verified
      An isolate is confirmed as Salmonella when the specific O serogroup has been determined and biochemical identification has been completed

      Taxonomy
      Family: Enterobacteriaceae

      Natural habitats
      Humans are the only reservoir for Salmonella typhi, indicating that they are adapted to the human host; healthy carriers have been noted.

      Clinical significance
      Strains of Salmonella are categorized as typhoidal and nontyphoidal.

      S. typhi ► typhoidal infection

      Typhoid fever

      Caused by Salmonella typhi, is a serious bloodstream infection, common in the developing world. Typhoid fever typically presents which a sustained debilitating high fever and headache.

      Adults characteristically present without diarrhea. Illness is milder in young children, where it may manifest as nonspecific fever.

      This fever has a low infectious dose (<103), and a long high variable incubation period (1 to 6 weeks)

      It is transmitted through person-to-person contact or fecally contaminated food or water.

      Fatal complications of typhoid most commonly occur in the second or third week of the illness.

  • Gram stain

    • the following information is not yet verified
      Gram negative rods,

      2-5 x 0.7-1.5 μm

  • Culture characteristics

    • the following information is not yet verified

      Facultative anaerobic

      Selective media for the isolation of Salmonella and Shigella from clinical specimens

      XLD / xylose lysine desoxycholate agar
      Salmonella cannot ferment xylose ► red colonies, possible with black discoloration
      Enterobacteriaceae ferment xylose ► yellow colonies

      HEK / hektoen agar
      These bacteria grow with green to blue-green colonies on the agar, possible with black discoloration.

      BA
      colonies are 1-3 mm, usually the S-type, they are large, gray-white and smooth.

      After subculturing there are also R-type ("rough" form), these are grainy, with an irregular surface and a serrated edge.

      McConkey colonies are pale, non lactose fermenter

      BBAØ growth

      Antigen
      Salmonella can be further identified by its possession of somatic (O) and flagellar (h) antigens.

      Salmonella typhi also has a Vi-antigen, which is a capsular antigen

  • Characteristics

  • References

    • James Versalovic et al.(2011) Manual of Clinical Microbiology 10th Edition


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