s almonella
DESCRIPTION
S almonella. Gastroenteritis, typhoid fever, paratyphoid fever. Salmonellae. Over 2000 different antigenic types Originally classified into different species Now! Represent serotypes of a single species Salmonella enterica Various subspecies - PowerPoint PPT PresentationTRANSCRIPT
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Salmonella
Gastroenteritis, typhoid fever,paratyphoid fever
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Salmonellae Over 2000 different antigenic types Originally classified into different species Now! Represent serotypes of a single species
Salmonella enterica Various subspecies Most mammals associated species are found
in subspecies enterica Example: S. enterica subspecies enterica
serotype Enteritidis Simply: S. Enteritidis
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Serotypes Many are host-specific
Certain serotypes are major cause of food-borne infection
Most are benign and restricted
Some salmonellae cause life-threatening systemic infections (such as S. enterica serotypes Typhi and Paratyphi)
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Description and antigenic structure
Enterobacteriaceae
Somatic or “O” antigen (heat-stable LPS)
Flagella or “H” antigen (heat-labile PP)
“H” antigen has two phases (1 and 2)
“Vi” (virulence) antigen in serotype Typhi
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Kauffmann-White classification
Named salmonella as individual species
30 groups based on “O” antigen
Subdivided into groups by “H” antigen
Example: S. typhi (9,12, [Vi]:d-)
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Host range and pathogenicity
Strains of S. enterica are widely distributed
Vertebrates GIT
Certain serotypes: flies and cockroaches
Asymptomatic to self-limiting gastro-enteritis
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Morbidity, mortality and economical loss
Cholerae-suis (pigs)
Dublin (cattle)
Gallinarum-pullorum (poultry)
Abortus-equi (horses)
Abortus-ovis (sheep)
Other serotypes (no host preference)
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Host adapted serotypes
Typhi, Paratyphi A, B and C
Primarily human pathogens
Only found in human
Occasionally, Paratyphi B isolated from cattle, pigs, poultry, exotic reptiles and other animals
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Pathogenicity Enteric fever (typhoid and paratyphoid)
Typhi, Paratyphi A, B and C
Gastroenteritis and food poisoning Typhimurium
Bacteraemia Typhimurium Paratyphi C
Asymptomatic carriers
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Enteric fever Caused by serotypes Typhi, Paratyphi A, B and C
These Salmonellae are usually found only in human
Execrated in faeces and urine of patients and carriers
Typhi is mainly water-borne Paratyphi is mainly food-borne
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Penetration of ileal mucosa
Mesenteric lymph nodes
Lymph
Blood stream
Thoracic duct
Gall bladder Bone marrowLiver
Spleen
Primary bacteraemic phase (7-10 days of the incubation period)
Kidney
Second bacteraemia
Second bacteraemia
Fever and other sings
Fever and other sings
Intestine invasion inflammation and infiltration with mononuclear
followed by necrosis and ulceration
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Other Salmonella infections Bacteraemia
Abscesses
Arthritis
Inflammation of gall bladder
Osteitis
Neonatal meningitis (S. typhimurium)
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Laboratory diagnosis Enteric fever:
Blood , urine and stool
Diarrheal diseases Faeces and blood for culture
Bacteraemia Blood for culture
Abscesses and arthritis Pus for culture
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Duration Rate of isolation Specimens
First 10 daysThird week
75-90%30%
Blood
Second weekThird week
40-50%80%
Faeces
After the second week
25% Urine
Specimen selection in enteric fever
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Isolation
Aerobic incubation at 37 ° C
Faeces Selective media (XLD, DCA, MacConkey) Enrichment media (SF broth)
Blood culture
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Morphology
Gram –ve motile rods
Non-sporing
Non-capsulated (except S. typhi)
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Biochemical test for identification of bacteria
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Serological diagnosis of enterica Antigen tests
Detect S. typhi in faeces Sensitive and specific Detect the bacteria in the first week
Antibody test When no culture or antigen test available Needs careful interpretation Has no value in case of food-poisoning
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Shigella
Non-motile bacteria that conform with the definition of the family Enterobacteriaceae
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Classification of Shigellae Based on antigenic structure and bioactivity
Group A: S. dysenteriae 12 different serotypes
Group B: S. flexneri 10 serotypes
Group C: S. boydii 18 serotypes
Group D: S. sonnei 1 serotype
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Shigella infections Shigella cause bloody diarrhea
(dysentery) and non-bloody diarrhea. Often begins with watery diarrhea
accompanied by fever and abdominal cramps.
May progress to classical dysentery with scant stools containing blood, mucus and pus.
May be asymptomatic infection particularly in case of S. sonnei strains.
Rarely case other infections
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Transmission
Infect only humans
Mostly person-to-person spread
Faecal-oral route through contaminated food and water
House flies
Only few organisms are required to cause infection
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Epidemiology of Shigellosis The most virulent species is S. dysenteriae
serotype 1(Sd 1)
164.7 million case annually
163.2 in developing countries
1.1 million death
61% of mortalities in children < 5 years
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Etiology
S. flexneri (60%)
S. sonnei (15%)
S. boydii (6%)
S. dysenteriae (6%)
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In USA Annual reported cases = 20,000
Estimated undetected cases= 400,000
20% due to international travel
Common cause S. sonnei followed by S. flexneri
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S. dysenteriae Shigellosis Inflammation and ulceration of intestine Severe dysentery (Shiga toxin) Dehydration and protein loss Abdominal cramps Rectal pain Toxaemia High fever High WBCs with neutrophilia
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Causes of death
Circulatory collapse
Kidney failure
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Bacterial virulence
Enterotoxin
Mainly due to bacterial invasiveness
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Laboratory diagnosis Fresh faeces with enrichment media like Gram
Negative (GN) broth or Selenite broth.
Transport medium
pH alkaline
Culture in selective media XLD, DCA and MacConkey
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Serological identification of Shigellae
Polyvalent O group antisera for groups A,B,C, and D
Monovalent O antiserum
e.g monovalent S. dysenteriae 1 for identification of Sd 1
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The end