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Salmonella Infection

Queensland Health Guidelines for Public Health Units

Revision History

 Version  Date  Changes
 1.0 February 2010  Full revision of guideline. 

Infectious Agent

The agent is Salmonella species (excluding S. typhi and S. paratyphi which are notified separately - see typhoid/paratyphoid protocol).

Notification Criteria

Laboratory Definitive Evidence
Isolation or detection of Salmonella species (excluding S. typhi and S. paratyphi which are notified separately).

Community Outbreak Criteria
Geographical or temporal or epidemiologically linked cluster of cases infected with the same Salmonella serotype (or genotype or phage type).

Objectives of Surveillance

  1. To monitor the epidemiology of the disease and to inform public health initiatives.
  2. To detect outbreaks of disease, so as to enable prompt public health responses.

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Notification Procedure

Pathology Laboratories
To notify on initial isolation and on microbiological confirmation by usual means.

Attending Medical Practitioners/Medical Superintendents (or Delegates)
Notify two or more possibly linked cases of gastroenteritis by phone or facsimile.

Institutions (residential care facilities, hospitals)
Notify two or more cases of gastroenteritis within the facility by phone or facsimile.

Reporting to NOCS

Report only confirmed cases.

Confirmed case: A confirmed case requires laboratory definitive evidence.

Public Health Significance and Occurrence

Salmonellosis occurs worldwide and is generally classified as a foodborne illness. The incidence of infection is highest in infants and young children. About 60-80% of all cases occur sporadically. However, large outbreaks associated with hospitals, institutions for children, restaurants and residential care facilities are not uncommon. Outbreaks usually arise from food contaminated at its source or, less often, during handling by an ill person or carrier, but person to person spread can occur.

Deaths are uncommon, except in the very young, very old, debilitated and immunosuppressed. However, morbidity and associated costs of salmonellosis may be high.

Clinical Features

A bacterial disease which commonly manifests as an acute enterocolitis, with sudden onset of headache, abdominal pain, diarrhoea, nausea and sometimes vomiting. Fever is almost always present. Dehydration, especially among infants or in the elderly, may be severe.

The infection usually begins as an acute enterocolitis, and on occasion can develop into septicaemia or focal infection in any tissue of the body.  Infection can infrequently produce abscesses and cause septic arthritis, cholecystitis, endocarditis, meningitis, pericarditis, pneumonia, pyoderma or pyelonephritis.

Reservoir

  • Domestic and wild animals including poultry, swine, cattle and rodents
  • Patients - convalescent carriers and mild and unrecognised cases
  • Pets - tortoises, turtles, lizards and other reptiles, chickens, dogs, cats
  • Chronic carriers are rare among humans and common among birds and animals.

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Mode of Transmission

Ingestion of food contaminated by infected animal or human faeces. Contamination may occur directly or indirectly (transovarial transmission of S. Enteritidis in infected poultry has been documented overseas but not in Australia). Common sources include:

  • Raw and undercooked eggs and egg products
  • Raw milk and raw milk products
  • Raw and undercooked poultry and poultry products
  • Raw red meats and uncooked meat products
  • Raw fruit and vegetables contaminated during growing, harvesting or preparation processes.

Faecal-oral transmission from person to person and animal to person (especially poultry and reptiles).

A number of outbreaks have been reported where cracked or faecally-contaminated eggs have been identified as the source of infection.

Incubation Period

From 6-72 hours, commonly 12-36 hours. Lower infective doses may be associated with longer incubation periods up to 16 days.

Period of Communicability

Through the course of infection; extremely variable, usually several days to several weeks.

A temporary carrier state occasionally continues for months, especially in infants, and 1% of infected adults and 5% of children under 5 excrete the organism for >1 year. Antibiotics can prolong the period of shedding and therefore communicability.

Susceptibility and Resistance

Susceptibility is general and is usually increased by achlorhydria, antacid therapy, GI surgery, prior or current broad spectrum antibiotic therapy, neoplastic disease, immunosuppressive therapy and other debilitating conditions including malnutrition.

HIV infected individuals are at risk for recurrent nontyphoidal Salmonella septicemia and may require long-term antibiotic therapy.

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Management

Cases

Investigation
Only clusters of cases should be investigated.

Investigation should occur if there are two or more cases of gastroenteritis in a residential care facility, hospital or childcare facility. In consultation with the attending medical practitioner or director of nursing or director of the facility, attempt to identify the source of infection, such as ingestion of suspect foods, especially raw or undercooked eggs, milk, meat, poultry and their products, cross contamination of kitchen utensils, exposure to cases or animal faeces, or recent overseas travel.

Restriction
Exclude all cases who are food handlers or carers of patients, children or the elderly from work until 48 hours from cessation of diarrhoea and clinically recovered.

All other cases should be excluded from work or school until 24 hours from cessation of diarrhoea and clinically recovered.

 Exclude all cases from non-residential care facilities (eg. childcare facilities) until 48 hours from cessation of diarrhoea and clinically recovered.

 Isolate all cases occurring in residential care facilities until 48 hours after the cessation of diarrhoea and clinically recovered.

 Asymptomatic carriers need not be excluded from work but the importance of strict personal hygiene and proper hand-washing should be stressed particularly for food handlers.

Counselling
Cases/carers should be advised of the nature of the infection and its mode of transmission.

Advise staff in residential care facilities, hospitals and childcare centres to put in place extra outbreak infection control measures immediately.

Educate about hygiene practices, in particular hand-washing before eating and preparing food, and after going to the toilet.

Contacts

Contact Tracing
Not routinely.

Investigation
Investigation of contacts is not routinely performed in sporadic cases.

Counselling
If contact tracing occurs, educate about hygiene practices, in particular hand-washing before eating and preparing food, and after going to the toilet.

Other Control Measures

Health Education
Educate the general public about proper food preparation and personal hygiene.

Health care facilities should have specific outbreak control protocols to put into place when there are two or more related cases of gastroenteritis regardless of cause. These protocols should include early notification to the local public health unit. Staff working in these health care facilities should receive regular inservice training on infection control measures within their facility.

Community Outbreaks/Epidemics

Investigation

Attempt to identify the source of infection in conjunction with Environmental Health, OzFoodNet and other appropriate agencies.

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Preventive Measures

Exclude cases as described above.

Avoid cross contamination of fresh or cooked foods by uncooked foods or contaminated utensils. Cook poultry, beef, mince and eggs thoroughly before eating.  Do not eat or drink foods containing raw eggs.

Wash fruit and vegetables before eating.

Take care with foods prepared for infants, the elderly and the immunocompromised.

Wash hands, kitchen work surfaces and utensils (esp. cutting boards and blenders) with soap and water immediately after they have been in contact with raw meat or poultry.

Wash hands before eating and preparing food, after going to the toilet and after handling animals, birds or pets.

Feedback

Report to notifying agency.

Summary

Complete outbreak summary report form for OzFoodNet.

Prepare a report of the investigation for the Communicable Diseases Branch, Queensland Health, on request.

References

Heymann, D. (Ed).  2008. Control of Communicable Diseases Manual, 19th edition.  American Public Health Association: Washington.

Hocking AD, (Ed). 2003. Foodborne microorgansims of Public Health significance, 6th edition. Waterloo (NSW): Australian Institute of Food Science and Technology Incorporated, NSW Branch, Food Microbiology Group.

PHLS Advisory Committee on Gastrointestinal Infections. 2004. Preventing person-to-person spread following gastrointestinal infections: guidelines for public health physicians and environmental health officers. Communicable Disease and Public Health, 7 (4): 362-384.

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Last updated: 9 September 2010