16 Shigella

Kiyoshi Shiga

shigella is named after thhis Japanese microbiologist who isolated the first member of the group in 1896 from dysentery epidemic in Japan

Kiyoshi Shiga who isolated the first member of the group in 1896 from dysentery epidemic in Japan

Kiyoshi Shiga who isolated the first member of the group in ____ from ________ epidemic in Japan

Shigella shiga

Shigella dysenteriae is then called?

Enterobacteriaceae

Shigella is under what family

Shigella general characteristics

• Gram negative

• non motile, non sporeforming, non capsulated

• facultative anaerobe

Shigella general characteristics

• Gram ____

• non ____, non _____, non ______

• ______ anaerobe

Shigella general characteristics

• Non-lactose-fermenting except S. sonnei

• Catalase positive except S. dysenteriae type 1 and oxidase negative

Shigella general characteristics

• Non-_______-fermenting except S. _____

• Catalase _____ except S. dysenteriae type 1 and oxidase ______

Shigella cultural characteristics

• Temperature range for growth 10-40’C, optimum at

  37’C

• Deoxycholate citrate agar and xylose lysin deoxycholate agad is useful selective medium (Shigella do nojt have black center as salmonella)

Shigella cultural characteristics

• Temperature range for growth __-40’C, optimum at

  __’C

• _______ citrate agar and ______ lysin deoxycholate agar is useful selective medium (Shigella do nojt have black center as salmonella)

Shigella cultural characteristics

colonies:

• nutrient agar 2 mm in diameter, circular, convex,

  smooth and translucent

• In MacConkey colorless except S. sonnei which is

  pink

• In Salmonella-Shigella agar colorless colonies

Shigella cultural characteristics

colonies:

• nutrient agar 2 mm in diameter, ____, _____,

  smooth and translucent

• In MacConkey _____ except S. sonnei which is

  pink

• In Salmonella-Shigella agar ______ colonies

Shigella viability

• Death point 56’C for 1 hour, 1% phenol for 30

  minutes

• Viable in water and ice for 1 to 6 months

• In feces, dies within a few hours due to acidity

  produced by growth of coliforms

Shigella viability

• Death point __’C for 1 hour, 1% ___ for 30

  minutes

• Viable in ____ and ___ for 1 to 6 months

• In ____, dies within a few hours due to ____

  produced by growth of coliforms

Shigella biochemical reactions

• Catalase positive except S. dysenteriae type 1

• MR positive

• VP, Urease, Citrate, Oxidase, H2S negative

Shigella biochemical reactions

• ______ positive except S. dysenteriae type 1

• _____ positive

• VP, Urease, Citrate, Oxidase, H2S ______

Shigella sonneiClassification based on Biochemical and Antigenic

Characteristics

species that is late lactose fermenter

Classification based on Biochemical and Antigenic Characteristics Shigella

1. Subgroup A: S. dysenteriae 15 serotypes

2. Subgroup B: S. flexneri 8 serotypes

3. Subgroup C: S. boydii 19n serotypes

4. Subgroup D: S. sonnei only 1 serotype

• Shigella dysenteriae most serious form of bacillary

  dysentery (Shiga toxin)

Classification based on Biochemical and Antigenic Characteristics Shigella

1. Subgroup A: S. ______ 15 serotypes

2. Subgroup B: S. _____ 8 serotypes

3. Subgroup C: S. _____ 19n serotypes

4. Subgroup D: S. ______ only 1 serotype

• Shigella dysenteriae

• most serious form of bacillary

  dysentery (Shiga toxin)

1. plasmid antigens

2. invasiveness

3. other toxins (shiga toxins)

Shigella virulence factors

Plasmid antigens

Effectors of plasmid transmit from the bacterial cytoplasm to epithelial cell cytoplasm of colon

Invasiveness

virulent Shigella penetrate the mucosa and epithelial cells of the colon in an uneven manner. Intracellular multiplication leads to invasion of adjacent cells, inflammation and cell death

shiga toxin

toxin which may be neurotoxic, cytotoxic, and enterotoxic. The enterotoxic property is responsible for watery diarrhea.

asymptomatic infection to severe bacillary dysentery

Shigella c/s ranges from?

Two-stage disease

Shigella c/s: watery diarrhea changing to dysentery with frequent small stools with blood and mucus, tenesmus, cramps, fever

early stage

Shigella c/s:

• Watery diarrhoea attributed to the enterotoxic activity of Shiga toxin

• Fever attributed to neurotoxic activity of toxin

1. ingestion

2. Non-invasive colonization and cell multiplication

3. Production of the enterotoxin by the pathogenic bacteria in the small intestine

shigella c/s process involve:

1. Adherence to tissue invasion of large intestine

2. Typical symptoms of dysentery

3. Cytotoxic activity of Shiga toxin increases severity

shigella c/s second stage

man: case or carrier

Shigella pathogenesis:

• source

CONTAMINATED FINGERS, FOOD, FLIES, FOMITES

Shigella pathogenesis:

• mode of spread

person to person

shigella transmission

10-100 viable bacilli

Shigella infective dose

HIGHEST CONCENTRATION IN STOOL DURING EARLY/ACUTE INFECTION: 10³ to 10^9 VIABLE BACILLI PER GRAM OF STOOL

HIGHEST CONCENTRATION IN STOOL DURING ______/______ INFECTION: 10³ to 10^9 VIABLE BACILLI PER GRAM OF STOOL

1. Sampling

2. Selenite F broth (0.4%) used as enrichment and transport media

3. Culture media

4. Biochemical test

Shigella lab diagnosis

Ciprofloxacin, Fluoroquinol, Azithromycin, Pivmecillinam, Ceftriaxone

CFAPC

Shigella treatment and control

• antibiotics

Shigella treatment and control

• Preventing infected individuals from handling food

• Thoroughly washing hands after changing and disposing of an infant’s diaper

• Disinfecting surfaces handled by infected individuals

  
  

Shigella treatment and control

• Preventing infected individuals from _______ food

  
  

• Thoroughly _______ hands after changing and disposing of an infant’s diaper

  
  

• _______ surfaces handled by infected individuals

  
  

Shigella treatment and control

• Not allowing infected children to play in community swimming areas

  
  

• If traveling, consuming boiled or filtered water, fruits peeled by self, and hot meals

  
  

• Proper storage of food

Shigella treatment and control

• Not allowing infected children to ____ in community swimming areas

  
  

• If traveling, consuming boiled or filtered water, fruits peeled by self, and hot meals

  
  

• Proper ______ of food