National case definition: Salmonellosis

Date of last revision/review: December 2023.

National notification

Only confirmed cases of disease should be notified.

Type of surveillance

Routine case-by-case notification to the federal level.

Case classification

Confirmed case

Laboratory confirmation of infection with or without clinical illness:

• Isolation of Salmonella spp. (excluding Salmonella Typhi) from an appropriate clinical specimen (e.g., stool, blood, cerebrospinal fluid, rectal swab, deep tissue wounds, other sterile site, vomit, urine).

Probable case

Clinical illness in a person who is epidemiologically linked to a confirmed case;

or

Detection of Salmonella spp. nucleic acid with or without clinical illness, in an appropriate clinical specimen (dependent on the test used), using a nucleic acid test (NAT), such as a polymerase chain reaction (PCR).

Laboratory comments

Further strain characterization (e.g., serotyping, whole genome sequencing [WGS]) is required for epidemiologic, public health, and clinical management.

Because the current Salmonella NATs cannot distinguish by serotype, a NAT positive result for Salmonella would require further tests to confirm the case as salmonellosis, typhoid fever, or (if applicable) paratyphoid fever.

If more than one target is positive on the gastrointestinal NAT panel, it may be indicative of a cross-reaction, coinfection and/or a single organism harbouring these genes. Reflex culture should be performed to confirm all suspect bacterial NAT signals and to meet requirements for epidemiologic, public health, and clinical management of that organism.

Clinical evidence

Clinical illness may be characterized by the following signs or symptoms: Diarrhea, chills, headache, abdominal pain, nausea, fever and/or vomiting. The severity of illness may vary. While not considered clinical illness, asymptomatic infections may occur.

ICD code(s)

ICD-11 code(s)

• 1A08 Paratyphoid fever
• 1A09 Infections due to other Salmonella
  • 1A09.0 Salmonella enteritis

ICD-10 code(s)

• A01.1 Paratyphoid Fever A
• A01.2 Paratyphoid Fever B
• A01.3 Paratyphoid Fever C
• A01.4 Paratyphoid Fever, unspecified
  • Infection due to Salmonella Paratyphi not otherwise specified (NOS)
• A02 Other Salmonella infections (excluding S. Typhi and S. Paratyphi)
  • A02.0 Salmonella enteritis Salmonellosis
  • A02.1 Salmonella sepsis
  • A02.2 Localized Salmonella infections
  • A02.8 Other specified Salmonella infections
  • A02.9 Salmonella infection, unspecified

Comments

Includes S. Paratyphi (paratyphoid fever). Probable case definitions are provided as guidelines to assist with case finding and public health management, and are not for national notification purposes.

The use of culture independent diagnostic tests (CIDTs) in clinical settings as stand-alone tests for the direct detection of Salmonella in stool is increasing.

Common CIDTs include antigen-based tests and molecular nucleic acid tests (NATs). Although the term CIDT is used by other reporting bodies, Canada has used the terms NAT and PCR in their case definitions to exclude antigen-based CIDTs, which currently are not readily used or available for most enteric bacterial pathogens. In addition, there are concerns regarding the accuracy of antigen-based CIDTs for most bacterial enteric pathogens; thus, the specification of NAT/PCR ensures that an antigen test on the clinical specimen is not interpreted as part of a case count. Note: Some reporting bodies may choose to report NAT and PCR results under the term "CIDT", as they are a form of CIDT when directly performed on the clinical specimen.

Specific performance characteristics such as sensitivity, specificity, positive predictive value, and negative predictive value of these assays likely depend on the method used. It is therefore useful to collect information on the type(s) of testing performed for reported cases. However, due to the variable performance characteristics of NAT methods and the potential for clinical sample degradation during transit, discordant results may occur between testing methods and laboratories. It is best practise to culture the NAT positive specimen as soon as possible, such as performing culture in the laboratory that generated the NAT positive signal. When a specimen is positive using a NAT, it is strongly advised to collect and document information on all culture results for the specimen (i.e., NAT+/culture+ versus NAT+/culture– versus NAT+/culture not done); this information is helpful to inform the development and implementation of CIDT and associated case definitions at the provincial, territorial and national levels.