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salmonella

Salmonella

introduction

  • Salmonella are Gram negative anaerobe clinically important bacteria and along with Campylobacter are the most common bacterial causes of gastroenteritis
  • certain host factors make humans particularly susceptible to infection, contracted by ingesting contaminated food or water with as little as 200 bacteria ingested, although median load in health adults to cause infection is 1 million non-typhoid bacteria
  • in the developed Western world, Salmonella Enteritidis is the main pathogen
  • travellers to Asia and other regions are at risk of 2 other important Salmonella pathogens which cause an enteric fever, often with constipation rather than diarrhoeal illness:
  • after crossing the intestinal epithelial layer, the bacteria replicate in macrophages in Peyer’s patches, mesenteric lymph nodes, and the spleen. The bacteria may then potentially disseminate to the lungs, gallbladder, kidneys, bone, joints or central nervous system.
  • the non-typhoid types generally produce a more localised illness whilst typhoid produces a systemic illness.
  • severity of disease is related to serotype, dose ingested, and host factors.
  • this page discusses non-typhoid infection, see also Salmonella typhi (typhoid enteric fever)
  • NOTE: The concept of “serovars” is important to the nomenclature regiment for the Salmonella genus. Serovar names also follow the genus, but are not to be confused with species. Unlike species names, serovars are always capitalized and never italicized/underlined.

common sources

non-typhoid

  • poultry (hence the emphasis on ensuring cooked food is NEVER contaminated with uncooked poultry or utensils which have contacted uncooked poultry)
  • eggs
  • dairy products
  • water
  • beef, fruit and vegetables
  • infants may contract it from touching reptiles, riding in shopping cart with poultry, or consuming liquid infant formula.
  • direct contact with animals which act as reservoirs for the bacteria accounts for 6% of nontyphoid cases
    • reservoirs of the bacteria include humans, poultry, swine, cattle, rodents, and pets such as lizards, tortoises, turtles, chicks, dogs, and cats.

host risk factors

  • extremes of age
    • neonates have highest risk
    • those under 20 years and those over 70 years also have high risk (particularly if from nursing homes)
    • case fatality rate for nontyphoid is 1.3% for those over age 50 years
  • immunocompromised states
  • prior antibiotic use (alters faecal flora and increases Salmonella invasion risk)
  • achlorhydria (eg. neonates, proton pump inhibitors (PPIs), antacids) allows more bacteria to survive the gastric juices and enter the intestine
  • recent bowel surgery
  • malnutrition

non-typhoid Salmonella syndromes

gastroenteritis

  • esp. summer months in temperate climates
  • incubation 8-48hrs
  • fever (if present usually subsides by 72hrs), chills, N&V, abdominal cramps, diarrhoea (lasting 3-7 days and often bloody)

bacteraemia

  • usually in immonocompromised patients
  • prolonged or recurrent fevers
  • may seed to local infections eg. bone, joints
  • mycotic abdominal aortic aneurysms may occur

localised infection

  • occurs in 5-10% patients with bacteraemia
  • almost any site can be infected

chronic carrier states

  • stool carriage for > 1 year
  • occurs in 0.2-0.6% nontyphoid cases

ED Mx of nontyphoid Salmonella

  • most cases can be Mx as outpatient with supportive care as per gastroenteritis as most are self-limiting.
  • antibiotics tends to increase adverse effects and prolong stool carriage.
  • Salmonella is a notifiable disease in Victoria
  • food handlers with infection require specific occupational Mx to prevent causing food-borne outbreaks
  • stool culture is usually sent for cases of gastroenteritis with bloody diarrhoea
  • patients with severe illness, are high risk and/or are dehydrated should be considered for admission
    • iv access and iv fluids if dehydrated
    • FBE, U&E
    • look for and treat localised infection
    • consider antibiotics (see below)
      • 2-5 day course, or until fever has resolved
      • flouroquinolone antibiotics or ceftriaxone are often used as antibiotics of choice
      • oral antibiotics if tolerated1):
        • o azithromycin 20mg/kg up to 1g stat then 10mg/kg up to 500mg daily for 6 more days
        • or, o ciprofloxacin 12.5mg/kg up to 500mg bd for 5-7 days
      • iv antibiotics if oral not tolerated:
        • iv ceftriaxone 50mg/kg up to 2g daily until oral Rx as above can be tolerated
        • or, iv ciprofloxacin 10mg/kg up to 400mg bd until oral ciprofloxacin can be tolerated
  • chronic carriers may be considered for 1-3 months of oral antibiotics
  • antibiotic resistance is an increasing problem

indications for admission and antibiotic Rx

  • age < 2 months
  • elderly
  • immunocompromised
  • sickle cell disease
  • prosthetic grafts (patients with infected grafts consider starting empirical vancomycin + ceftriaxone 2g daily 2) )
  • unstable vital signs
  • extraintestinal disease

exclusion from work

  • exclusion from work and social activities should be considered for symptomatic, and asymptomatic, people who are:
    • food handlers
    • healthcare/daycare staff who are involved in patient care and/or child care
    • children attending unsanitary daycare centers
    • older children who are unable to implement good standards of personal hygiene.
  • the exclusion applies until two consecutive stool specimens are taken from the infected patient and are reported negative.
salmonella.txt · Last modified: 2012/01/10 23:32 by gary