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					SALMONELLA INFECTION


Abdelaziz Elamin, MD, PhD, FRCPCH
College of Medicine
Sultan Qaboos University
 INTRODUCTION
  Discovered in 1880 & named after Daniel
Salmon, the pathologist who first isolated the
organism from porcine intestine.

  Salmonella is a motile, gram-negative, rod-
shaped bacteria, which is a leading cause of
bacterial food-borne diseases.
  Of the 2000 strains recognized, human
infection are caused mainly by 5 serotypes,
typhi, paratyphi, typhimurium, choleraesuis &
enteritidis.
 TRANSMISSION
  Infection follows ingestion of contaminated
food or water. Meat, poultry, eggs & diary
products are frequent sources.

  Pets, domestic animals and infected human
are potential reservoirs. Person to person &
animal to human transmission is recognized.

  In healthy humans a dose of about one million
bacteria is necessary to produce symptoms.
PATHOPHYSIOLOGY
   After ingestion salmonella must survive the
 stomach acidic PH & colonize small intestine.

 Salmonella then attach to & penetrate the gut
mucosa resulting in diarrhea from direct
mucosal damage & by action of exotoxins.

   Another portal of entry is invasion of lymphoid
tissue in the GIT (peyer patches) & multiplication
within macrophages leading to bacteremia.
SALMONELLOSIS
  Salmonella typically produces 3 distinct
syndromes: food poisoning, typhoid fever &
asymptomatic carrier state.

  Salmonella gastroenteritis manifest as vomiting
& diarrhea within 6-48 hours after ingestion of food
or drink contaminated with bacteria.

  It is self-limiting, treatment is by water & salts
replacement. Antibiotics are not usually needed.
 MORTALITY & MORBIDITY
  Infection with nontyphoidal salmonella produces
self-limiting gastroenteritis and food poisoning.

  Whereas mortality caused by typhoid fever is
rare in western countries, it is associated with
significant mortality & morbidity in tropical
countries (10-30%).

  Dehydration is the most common complication
of typhoid fever, but serious intestinal & extra-
intestinal complications may occur.
 TYPHOID FEVER
  Typhoid fever is the most serious salmonella
infection with significant morbidity & mortality.

  Caused by salmonella typhi & paratyphi.


  Incubation period is 1-2 weeks.

  Salmonella has somatic (O antigen) & flagellar H
antigen. The O antigen is more specific for
serologic testing.
FREQUENCY
  An estimated 15-30 million cases of typhoid
fever occur globally each year.

  The disease is endemic in many developing
countries in Asia, Central America & Africa.

  Outbreak of typhoid fever have been reported
recently from Eastern Europe.

  Incidence in Sudan is not exactly known, but
estimated as 50 per 100,000 people/year.
PRECIPITATING FACTORS
  Defects in cellular-mediated immunity (AIDS,
Transplant patients & malignancy).

  Defects in phagocytic function (malaria,
histoplasmosis & schistosomiasis).

  Splenectomy or functional asplenia (sickle cell dis)
  Low stomach PH ( patients on anti-ulcer drug).
  Prolonged use of antibiotics (altered gut flora).
  Injured gut barrier (bowel disease or surgery).
DIFFERENTIAL DIAGNOSES
Cryptosporidiosis

Campylobacter infection

Cyclospora

Listeria monocytogenes

Escherichia Coli infection

Shigellosis
 LAB FINDINGS
 Salmonella can be grown from blood or bone
marrow in the 1st week, from stool in the 2nd
week & from urine in the 3rd week.

  Special media are needed for transport & for
culture.

  leukopenia is typical but WBC may be normal.

  Widal test is not diagnostic, titer > 1:320 or 4
fold increase in titer support the diagnosis.
CLINICAL PICTURE
  Symptoms begin with sudden onset of high-
grade fever, headache & dry cough.
  Fever is swinging or may show step ladder
pattern & patient initially feel well & mobile.

  Abdominal pain & toxicity follow soon & by
the end of 1st week spleen is palpable & pink,
discrete, skin rash appears over the trunk.
 Constipation is more common than diarrhea
which is usually greenish in color (pea soup).
CLINICAL PICTURE/2
  Abdominal tenderness & hepatomegaly occur
in 50% of patients.

  The pulse is relatively slow in relation to fever
(Paget sign).

  The tongue is coated with free margins &
halitosis may be present.

  The sweat of some patients smell like yeast.
CLINICAL PICTURE/3
  The 3rd week of illness is the usual time for
complications in the untreated patients.

  Local gut as well as systemic
complications may occur.

  Serious infections may progress rapidly to
drowsiness & coma which is usually fatal
(coma vigil).
  Mortality is unlikely after the 4th week &
patients may become carrier if not treated.
LOCAL COMPLICATIONS
Intestinal hemorrhage

Intestinal perforation

Paralytic ileus

Zenker degeneration of abdominal muscles
SYSTEMIC COMPLICATIONS
 Endocarditis
 Arteritis & arterial emboli
 Cholecystitis
 Hepatic & splenic abscesses
 Pneumonia or empyema
 Osteomyelitis & septic arthritis
 Meningitis
 Urinary tract infection
 TREATMENT
  Medical care include rehydration, antipyretics
& antibiotics.
  Drugs of choice are Ceftriaxone & ciprofloxacin
but Cotrimoxazole & Chloramphenicol are still
used in developing countries. Ampicillin kills
bacilli hiding in the bile & hence prevents or
reduce the carrier state.

  Chronic resistant carrier state may necessitate
cholecystectomy. Surgical care may also be
needed in patients with intestinal complications.
NURSING CARE
  Isolation & barrier nursing is indicated

  Notification of the case to the infection control
nurse in the hospital.

  Trace source of infection.


   continue breastfeeding infants & young children
and give ORS & light diet for other patients in the
first 48 hours.
 PREVENTION
  Education on hygiene practices like hand
washing after toilet use & avoidance of eating in
non hygienic restaurants.

  Proper handling & refrigeration of food even
after cooking.

  Salmonella TAB vaccine is available but
affectivity is low (50% claimed protection).
  Antibiotic prophylaxis is not needed for
house-hold contacts.
PROGNOSIS
  With early diagnosis and prompt treatment
most patients with typhoid fever will recover in
due time.

  Fever & toxicity subsides within 72 hours of
antibiotic treatment.
  Mortality is > 50% in untreated severe typhoid
fever particularly in children & elderly.

  Recrudescence is rare but chronic carrier
state is reported in 10% of patients.

				
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