दशै, तिहारछठ २०७५ को पावन अवसरमा सम्पूर्ण वेबसाइट पाठकहरुमा मंगलमय शुभकामना | Read more>>
Well wishes for all Website Readers on this special occasion of Dashain, Tihar and Chhat 2018

SHIGELLA - Diagnosis and Treatment

Shigella -Introduction, Taxonomy, Cultural characteristics, Biochemical reactions, Virulence factors, Clinical symptoms, Pathogenesis, Laboratory diagnosis, Treatment and control

Shigella -Introduction, Taxonomy, Cultural characteristics, Biochemical reactions, Virulence factors, Clinical symptoms, Pathogenesis, Laboratory diagnosis, Treatment and control

Shigella is named after the Japanese microbiologist Kiyoshi Shiga who isolated the first member of the group in 1896 from epidemic dysentery in Japan which was then called Shigella shiga and is now called as S. dysenteriae.
  • Shigella is an Enterobacteriaceae 
  • Gram-negative, 
  • Non-motile 
  • Facultative anaerobes 
  • Nonspore forming Non-capsulated 
  • Non-lactose fermenting except S. sonnei. 
  • Catalase positive except S. dysenteriae type1 and 
  • Oxidase negative. 
Deoxycholate citrate agar and xylose lysine deoxycholate agar is useful selective medium (Shigella do not have a black center in this medium as Salmonella).

Taxonomy 

Family Enterobacteriaceae
  • Shigella dysenteriae: most serious form of bacillary dysentery (Shiga toxin) 
  • Shigella flexneri: shigellosis in underdeveloped countries 
  • Shigella sonnei: shigellosis in developed countries 
  • Shigella boydii: Less frequently isolated from dysentery patients. 

Classification: based on biochemical and antigenic characteristics. 

  • Subgroup A: S. dysenteriae: 15 serotypes: 
  • Subgroup B: S. flexneri: 8 serotypes. 
  • Subgroup C: S. boydii: 19 serotypes 
  • Subgroup D: S. sonnei: only one serotype 

Cultural characteristics 

Temperature range for growth 10-40°C(Optimum temp 37 °C)

In Nutrient Agar (After overnight culture) 
  • 2 mm in diameter, circular, convex, smooth and translucent. 
In MacConkey agar 
  • Colorless Colony except for S. sonnei (Pink colony) 
In Shigella-Salmonella agar 
  • Colorless Colony 
Viability: 
  • Death point (56°C for 1 hour), 1% phenol for 30 min, Viable in water for days and in ice for 1-6 months, In feces, it dies within few hour due to acidity produced by growth of coliform. 

Biochemical reactions 

  • Catalase positive except dysenteriae type 1. 
  • Methyl red positive 
  • VP negative 
  • Urease negative 
  • Citrate negative 
  • Oxidase negative 
  • No production of H2S 
  • Shigella sonnei is a late lactose fermenter. 

Virulence factors: 

  • Plasmid antigens: Effectors of plasmid transmit from the bacterial cytoplasm to epithelial cell cytoplasm of the 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. Cell death is probably due to cytotoxic properties of shiga toxin that interfere with protein synthesis. The cellular death and resulting phagocytosis response by the host account for the bloody discharge of mucus and pus and shallow ulcers characteristic of the disease. 
  • Other toxins: It has a Shiga toxin which may be neurotoxic, cytotoxic, and enterotoxin. The enterotoxin property is responsible for watery diarrhea. 

Clinical symptoms 

Ranges from asymptomatic infection to severe bacillary dysentery
Two-stage disease: watery diarrhea changing to dysentery with frequent small stools with blood and mucus, tenesmus, cramps, fever.
Early stage:
  • Watery diarrhea attributed to the enterotoxic activity of Shiga toxin 
  • Fever attributed to neurotoxic activity of toxin 
Process involves:
  • Ingestion 
  • Non-invasive colonization and cell multiplication 
  • Production of the enterotoxin by the pathogenic bacteria in the small intestine; 
 Second stage:
  • Adherence to tissue invasion of large intestine 
  • Typical symptoms of dysentery 
  • Cytotoxic activity of Shiga toxin increases severity 

Pathogenesis Source: 

  • Man: Case or carrier. 
  • Mode of spread: Contaminated fingers, food, flies, fomites 
  • Person to person transmission 
  • Infective dose: 10-100 viable bacilli 
  • Highest concentration in stool during early/acute infection 103 to 109 viable bacilli per gram of stool 

Laboratory diagnosis 

Sampling: fresh stool, mucus flakes, and rectal swabs 
Selenite F broth(0.4%) is used as enrichment and transport media (for 9-12 hours) 

Culture media: Non-Selective Bromocresol purple lactose agar, Low selective MacConkey agar, High selective Deoxycholate citrate agar and SS agar. 

Reservoir: 

Man only 

Transmission: 

Faeco-oral route 

Distribution: 

Developing country: S. flexneri 
Developed country; S. sonnei 

Treatment and control: 

Ciprofloxacin, Fluoroquinolone, Azithromycin, Pivmecillinam, Ceftriaxone 
  • Preventing infected individuals from handling food 
  • Thoroughly washing hands after changing and disposing of an infant’s diaper 
  • Disinfecting surfaces handled by infected individuals 
  • 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

For More Notes on Microbiology Click Here.
Also like our facebook page: Microbiology Notes

Like our Facebook Pages
contact for perofessional web development
Name

Act/Policy,7,Culture,1,Current Affairs,4,Data,13,Development,2,Economy,1,Education,4,Exam Paper,4,Geography,7,Health,1,History,2,IQ,2,LokSewa,30,Microbiology,15,Nepal,1,NGO/INGO,4,Objective,8,Politics,1,Random GK,3,Science,4,Science & Health,14,Social,1,Subjective,2,Tips & Tricks,7,Travel,6,TU Notes,2,Website,5,
ltr
item
GITAB - Knowledge Hub: SHIGELLA - Diagnosis and Treatment
SHIGELLA - Diagnosis and Treatment
Shigella -Introduction, Taxonomy, Cultural characteristics, Biochemical reactions, Virulence factors, Clinical symptoms, Pathogenesis, Laboratory diagnosis, Treatment and control
https://4.bp.blogspot.com/-WMU3vH9aCgU/WrSher6oK5I/AAAAAAAAAmQ/k9XdA6Lh3WkGij3edTMO94dgs8a-32zPgCEwYBhgL/s400/Shigella-and-Salmonella-Colonies-on-XLD-Agar.jpg
https://4.bp.blogspot.com/-WMU3vH9aCgU/WrSher6oK5I/AAAAAAAAAmQ/k9XdA6Lh3WkGij3edTMO94dgs8a-32zPgCEwYBhgL/s72-c/Shigella-and-Salmonella-Colonies-on-XLD-Agar.jpg
GITAB - Knowledge Hub
https://www.gitab.com.np/2018/03/shigella-diagnosis-and-treatment.html
https://www.gitab.com.np/
https://www.gitab.com.np/
https://www.gitab.com.np/2018/03/shigella-diagnosis-and-treatment.html
true
6000603883160192241
UTF-8
Loaded All Posts Not found any posts VIEW ALL Readmore Reply Cancel reply Delete By Home PAGES POSTS View All RECOMMENDED FOR YOU LABEL ARCHIVE SEARCH ALL POSTS Not found any post match with your request Back Home Sunday Monday Tuesday Wednesday Thursday Friday Saturday Sun Mon Tue Wed Thu Fri Sat January February March April May June July August September October November December Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec just now 1 minute ago $$1$$ minutes ago 1 hour ago $$1$$ hours ago Yesterday $$1$$ days ago $$1$$ weeks ago more than 5 weeks ago Followers Follow THIS CONTENT IS PREMIUM Please share to unlock Copy All Code Select All Code All codes were copied to your clipboard Can not copy the codes / texts, please press [CTRL]+[C] (or CMD+C with Mac) to copy