Salmonella

Question 1

Salmonella

Answer 1

Salmonella

• Salmonella enterica has over 2500 subspecies (serovars/serotypes), causes:
  
  • Typhoid fever (enteric fever)*
  • Gastroenteritis*
  • Osteomyelitis*
  • Reactive arthritis (Reiter syndrome) *
    
    • in 30% patients following gastrointestinal disease
  • Septicemia

Question 2

Salmonella typhi
Typhoid fever

Answer 2

Salmonella typhi
Typhoid fever

• Gram negative rod
• Oxidase negative
• Non-lactose fermentor*
• Motile *
• Produces H2S gas *
• Vi antigen (associated with capsule) *
• Survives inside macrophages *
• Causes Typhoid fever (enteric fever)
• Reservoir: only humans *
• Transmission:
  
  • Fecal-oral route
  • _Typhoid carriers (gall bladder) *_
• Prediposing factors for infection
• Decreased stomach acid
• Sickle cell anemia* (impairment of mononuclear cells)

Question 3

Peyers Patches

Answer 3

Peyers Patches

• Ileum
• Contain macrophages, dendritic cells, B-lymphocytes and T-lymphocytes
• Peyers patches are an important part of immune surveillance and the generation of the immune response.

Question 4

Salmonella typhi – Pathogenesis and disease

(Week 1)

Answer 4

Salmonella typhi – Pathogenesis and disease

• Organism ingested (large number required if stomach acid is normal)
• →Infection begins in ileocecal region, Peyers patches
• →Organism passes through enterocytes, M cells
• →engulfed by macrophages (survive intracellularly)
• →Mesentric lymph nodes + blood
• • transient primary bacteremia
• At Week 1:
  
  • Blood cultures positive*
  • “Rose spots”*
  • Constipation*

Question 5

What’s going on with this boy?

Answer 5

Typhoid fever – Rose spots

Rose spots

• on abdomen, trunk
• only 25% patients

Question 6

Salmonella typhi – Pathogenesis and disease

(week 3)

Answer 6

S.typhi – Pathogenesis and disease

• →Macrophages carry organism to reticuloendothelial system (RES)
• bacteria multiply - liver, spleen, bone marrow, _gall bladder*_
• ** septicemia** (mainly fever)
• →organisms re-enter GI tract (through bile)
• By Week 3:
  
  • Stool cultures positive *
• Salmonella survives intracellularly and replicates inside macrophages *
• When extracellular its’ Vi antigen protects it from complement-mediated killing *

Question 7

Typhoid fever – Clincal disease

Answer 7

Typhoid fever – Clincal disease

• Incubation period: 5-21 days
  
  • Symptoms:
  • Fever
  • Headache
  • **Abdominal pain **
  • enlargement of liver (hepatomegaly)
  • Constipation (occasionally diarrhea)
• Untreated – mortality rate is 15%
• Among survivors symptoms resolve in a month

Question 8

Typhoid

Answer 8

Typhoid

• Complications (if untreated)
  
  • Intestinal hemorrhage
  • Perforation of Peyers patches
  • Rarely endocarditis
• Small percentage of patients on recovery become chronic carriers – reservoir of infection & transmission of disease*
  
  • S.typhi hides in gall bladder*

Question 9

Typhoid - Diagnosis

Answer 9

Typhoid - Diagnosis

• S.typhi can be isolated from:
• Blood cultures*
• Stool cultures*
  
  • Hektoen enteric agar
  • MA – lactose negative
• Other specimens:
  
  • Urine, Bone marrow, tissue biopsy of rose spots
• Widal test*
  
  • Presumptive test (no longer used in US)
  • Antibodies to O and H antigens in patient’s serum detected

Question 10

Typhoid treatment *

Answer 10

Typhoid treatment *

• Fluoroquinolones or 3rd generation cephalosporins
• Vaccines
  
  • Oral vaccine - live attenuated strain of S.typhi
  • Parenteral vaccine – Vi capsular polysaccharide
  • Vaccination recommended for those travelling to endemic areas – Asia, Africa, Latin America

Question 11

Salmonella serovars other than typhi

Answer 11

Salmonella serovars other than typhi
S. enteritidis
S. typhimurium

• Salmonella serovars other than typhi
  
  • S. enteritidis
  • ** S. typhimurium**
• Reservoir: GI tract of animals
  
  • _Chickens*_
  • _Pet turtles*, domestic pets_
• Transmission: Fecal-oral
  
  • Ingestion: chicken products
    
    • Raw chicken, eggs*
• Petting Reptiles
  
  • Snakes , turtles*

Question 12

Salmonella other than S. typhi

Answer 12

Salmonella other than S. typhiGastroenteritis/enterocolitis

• Gastroenteritis/enterocolitis
  
  • Second most common cause after Campylobacter*
• Reactive arthritis
  
  • Post-gastrointestinal infection
• _Osteomyelitis*_
• Sickle cell disease predisposes to ostoemyelitis *
• _Salmonella (paratyphi) is the most common cause of osteomyelitis in sickle cell disease patients (>80%) *_
• Septicemia
  *

Question 13

Salmonella Gastroenteritis

Answer 13

Salmonella Gastroenteritis

Salmonella Gastroenteritis

• 95% cases are foodborne
• Ingestion of Salmonella (large infectious dose – sensitive to gastric acid)
• **→Lowered stomach acid increases risk **
  
  • (antacids, gastrectomy)
• →Invades mucosa ileocecal region → invasive to lamina propria → inflammation
• →watery diarrhea, shallow ulceration
• Septicemia may occur – fever
  
  • Salmonella can be isolated in blood cultures

Question 14

Gastroenteritis treatment

Answer 14

Gastroenteritis treatment

Treatment:

• Gastroenteritis
  
  • Not indicated, may prolong convalescent carrier state
• For invasive disease*
  
  • Fluoroquinolones or
  • 3rd generation cephalosporins or
  • TMP-SMX

Question 15

Identifying Salmonella

Answer 15

Identifying Salmonella

• **GNB, oxidase negative **
• Nonlactose – fermentor
• **Motile (distinguishes from Shigella) **
• H2S
• Vi capsular antigen