What is the role of lab testing in the workup of food poisoning?

Updated: Jun 19, 2018
  • Author: Roberto M Gamarra, MD; Chief Editor: Praveen K Roy, MD, AGAF  more...
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Obtain the following laboratory studies in cases of suspected food poisoning:

  • Gram staining and Loeffler methylene blue staining of the stool for WBCs help to differentiate invasive disease from noninvasive disease.

  • Perform microscopic examination of the stool for ova and parasites.

  • Bacterial culture for enteric pathogens, such as Salmonella, Shigella, and Campylobacter organisms, becomes mandatory if a stool sample shows positive results for WBCs or blood or if patients have fever or symptoms persisting for longer than 3-4 days.

  • Perform blood culture if the patient is notably febrile.

  • CBC with differential, serum electrolyte assessment, and BUN and creatinine levels help to assess the inflammatory response and the degree of dehydration.

  • Assay for C difficile to help rule out antibiotic-associated diarrhea in patients receiving antibiotics or in those with a history of recent antibiotic use.

Histamine food poisoning from gram-negative bacteria in fin-fish products is also common, and Morganella morganii and M psychrotolerans are particularly strong histamine producers. The development of real-time quantitative polymerase chain reaction (RTiqPCR) techniques in conjunction with the use of selective primers and a quantitative enrichment step appear to have the potential to identify and quantify these two species in fish products. [15]

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