Vibrio cholerae

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Stool Culture

• Dr. Kiarash Ghazvini
• Department for bacteriology and virology,
• Mashhad University of medical Sciences

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  ????? ??? ???? Salmonella
• Shigella sp
• Campylobacter
• 0157H7, E. Coli
• Yersinia enterocolitica
• Clostridium difficile
• Vibrios cholera
• Aeromonas
• Plesiomonas.
• ?? ????.

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• When a stool specimen is sent to the microbiology
  laboratory for analysis, the physician must
  correctly request the appropriate examination and
  understand the limitations of that test.
• In the United States, stool specimens are most
  commonly sent for "bacterial culture." For most
  laboratories, this means culturing for C jejuni
  and Salmonella and Shigella organisms. If other
  organisms are suspected, the laboratory must be
  notified.

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  ???.

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  (Cary-Blair medium) ??? ? ?????? ???.

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• Refrigeration must be avoided as much as
  possible.
• No preservatives can be added to stool samples
  for bacterial detection. Cary-Blair or other
  suitable transport
• Stool specimens should be transported to the
  laboratory soon after collection.

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Campylobacter jejuni

• C. jejuni grows best at 42 C in an atmosphere
  containing 5 to 10 oxygen. Campylobacter
  species are therefore considered microaerophilic.
• Many laboratories purchase tanks of gas with an
  appropriate mixture to provide an atmosphere for
  culturing this organism.

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Campylobacter jejuni

• In settings where this is not practical (e.g.,
  when evaluating an outbreak in an area without
  immediate access to a laboratory), an acceptable
  atmosphere can be created with little expense by
  using a candle jar.

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Campylobacter jejuni

• C jejuni has characteristic colonial morphology,
  described as "running" and "wet-looking"because
  the colonies seem to run together. Microscopic
  morphology shows the typical gram-negative,
  curved rods that look like a seagull'swings.
• This characteristic morphology of the genus
  Campylobacter differentiates it from P.
  aeruginosa, which also grows at 42 C and is
  oxidase positive.

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Salmonellae

• Salmonella infections are confirmed by culture
• Organisms are most likely to be recovered from
  blood cultures of patients suspected of typhoid
  fever if the specimens are obtained during the
  first week of the infection.

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Salmonellae

• Stool cultures yield the organisms during the
  third and fourth week of the infection.
• Routine microbiologic media such as sheep blood
  agar and MacConkey agar, and highly selective
  enteric media, such as Hektoen enteric (HE) agar
  and xylose-lysine-deoxycholate (XLD) agar are
  used for recovery.
• Serotyping should be performed whenever possible.

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Shigellae

• Shigellae are fragile organisms that do not
  survive well outside the host for a long period.
  These organisms are particularly susceptible to
  acid pH therefore stool samples should be
  processed as soon as they are received in the
  laboratory .

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Shigellae

• Diarrheic stools from patients with suspected
  shigellosis contain pus and blood, a presentation
  typical of an invasive agent.
• Bloody stools must be plated as soon as possible
  on appropriate enteric media.

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Escherichia coli

• Diarrheogenic E. coli do not look different on a
  growth plate from E. coli that do not cause
  diarrheal disease.
• Diagnosis of diarrheal disease caused by E. coli
  requires a high index of suspicion from the
  clinician on the basis of history and physical
  findings.

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Escherichia coli

• In addition, because E. coli are part of the
  normal fecal flora, special tests are needed to
  differentiate these pathogens from the routinely
  isolated nonpathogenic E. coli.
• For example,
• many enterohemorrhagic E. coli do not ferment
  sorbitol. Sorbitol-negative E. coli can be
  selected in the laboratory by using a sorbitol
  plate, such as sorbitol MacConkey agar
• Antisera are also used to screen for specific
  serotypes.
• Enteroinvasive E. coli produce colonies and
  biochemical reactions similar to those of
  Shigella species. Tests to differentiate between
  these pathogens should be performed.

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Yersinia species

• Yersinia sp. grow well at 25 C.
• This characteristic may be used in the
  laboratory.
• Plating and incubation at this temperature and
  the use of selective media (e.g.,
  cefsulodin-irgasan-novobiocin CIN agar) permit
  ready isolation of Yersinia organisms.

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Yersinia species

• Cold enrichment procedures, such as placing fecal
  samples on isotonic saline and keeping them at 4
  C before the inoculation of selective medium,
  have increased recovery of the organism.

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Vibrio species

• Vibrio sp. requires highly selective medium for
  maximum recovery. Thiosulfate-citrate-bile
  salts-sucrose (TCBS) agar inhibits the usual
  colon flora.
• In addition, TCBS agar differentiates
  sucrose-fermenting from non-sucrose-fermenting
  vibrios

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• Salmonella
• Shigella sp
• Campylobacter
• 0157H7 E. Coli
• Yersinia enterocolitica
• Vibrios cholera
• Aeromonas
• Plesiomonas.
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• Hanging latrine on Meghna River, Nepal