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Salmonellosis (Salmonella spp.)
2017 Case Definition

CSTE Position Statement(s)

  • 16-ID-03

Background

In 2011, CSTE updated the salmonellosis case definition, classifying a positive culture-independent diagnostic testing (CIDT) result that is not culture-confirmed as a suspect case. Modification of the 2011 case definition is needed to address underreporting of salmonellosis cases and to make case definitions for enteric bacterial pathogens more consistent. This 2016 case definition changes the case classification for a case with a positive Salmonella CIDT result from suspect to probable.

Clinical Criteria

An illness of variable severity commonly manifested by diarrhea, abdominal pain, nausea and sometimes vomiting. Asymptomatic infections may occur and the organism may cause extra-intestinal infections.

Laboratory Criteria for Diagnosis

Supportive laboratory evidence: Detection of Salmonella spp. in a clinical specimen using a CIDT.

Confirmatory laboratory evidence: Isolation of Salmonella spp. from a clinical specimen.

Epidemiologic Linkage

Probable: A clinically compatible case that is epidemiologically linked to a case that meets the supportive or confirmatory laboratory criteria for diagnosis.

Criteria to Distinguish a New Case from an Existing Case

A case should not be counted as a new case if laboratory results were reported within 365 days of a previously reported infection in the same individual.

When two or more different serotypes are identified from one or more specimens from the same individual, each should be reported as a separate case.

Case Classification

Probable

  • A case that meets the supportive laboratory criteria for diagnosis; OR
  • A clinically compatible case that is epidemiologically linked to a case that meets the supportive or confirmatory laboratory criteria for diagnosis.

Confirmed

A case that meets the confirmed laboratory criteria for diagnosis.

Comments

The use of CIDTs as stand-alone tests for the direct detection of Salmonella in stool is increasing. Specific performance characteristics such as sensitivity, specificity, and positive predictive value of these assays likely depend on the manufacturer and are currently unknown. It is therefore useful to collect information on the type(s) of testing performed for reported salmonellosis cases. When a specimen is positive using a CIDT it is also helpful to collect information on all culture results for the specimen, even if those results are negative. Culture confirmation of CIDT-positive specimens is ideal, although it might not be practical in all instances. State and local public health agencies should make efforts to encourage reflexive culturing by clinical laboratories that adopt culture-independent methods, should facilitate submission of isolates/clinical material to state public health laboratories, and should be prepared to perform reflexive culture when not performed at the clinical laboratory as isolates are currently necessary for molecular typing (PFGE and whole genome sequencing) that are essential for outbreak detection.

Position statement classifies cases as confirmed (a case that meets the confirmed laboratory criteria) AND probable (a case that meets the supportive laboratory criteria for diagnosis OR a clinically compatible case that is epidemiologically linked to a case that meets the supportive or confirmatory laboratory criteria for diagnosis). "Suspected" has been removed.

Beginning in January 2018, cases of salmonellosis should be classified into two different conditions, for submission to the NNDSS : 1) Salmonellosis (excluding paratyphoid fever and typhoid fever), and 2) Paratyphoid fever (caused by Salmonella serotypes Paratyphi A, Paratyphi B [tartrate negative] and Paratyphi C).



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