Shigella Infections Quiz

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Questions and Answers

What is the primary mode of transmission for Shigella infection?

Direct contact with skin

Airborne transmission

Fecal-oral route (correct)

Vector-borne transmission

Which Shigella species is most commonly found in developing countries?

Shigella boydii

Shigella dysenteriae

Shigella flexneri (correct)

Shigella sonnei

What is a characteristic symptom of shigellosis?

Nausea followed by vomiting

Severe abdominal cramps without diarrhea

Watery diarrhea followed by dysentery (correct)

High fever and rash

What is the incubation period for Shigella infections?

1-3 days Signup and view all the answers

Which characteristic is NOT true for Shigella species?

They are motile gram-negative bacteria Signup and view all the answers

What is the primary cause of mortality in infants due to diarrhea in developing countries?

Shigella infection Signup and view all the answers

Which of the following accurately describes the early stage of Shigellosis?

Watery diarrhea and fever Signup and view all the answers

What is one of the primary virulence factors of Shigella?

Invasiveness and adherence to host cells Signup and view all the answers

What type of diarrhea does Shiga toxin primarily cause in the early stage of infection?

Watery diarrhea Signup and view all the answers

Which diagnostic test is indicated for the presence of polymorphonuclear leukocytes (PMNs) in feces?

Methylene blue staining of feces Signup and view all the answers

What treatment approach is primarily emphasized for managing Shigella infections?

Supportive treatment for dehydration Signup and view all the answers

Which of the following statements about Shiga toxin is correct?

It has both enterotoxic and cytotoxic properties. Signup and view all the answers

What enhances the growth of Vibrio cholerae in laboratory settings?

1% salt addition Signup and view all the answers

What is the primary route of transmission for cholera?

Oral fecal route Signup and view all the answers

What characterizes the stool of a cholera patient?

Rice-water appearance Signup and view all the answers

Which virulence determinant is crucial for cholera toxin's effectiveness?

Bacterial colonization Signup and view all the answers

What percentage of body weight loss indicates moderate dehydration in cholera?

Up to 10% Signup and view all the answers

What type of bacterium is Helicobacter pylori?

Helical and microaerophilic Signup and view all the answers

Why is it difficult to develop a vaccine for cholera?

Unstable strains of Vibrio cholerae Signup and view all the answers

What does the 'TCP' in TCP pili stand for?

Toxin-Capture Proteins Signup and view all the answers

How does Vibrio cholerae tolerate salt in its growth medium?

Through osmotic regulation Signup and view all the answers

Which characteristic is NOT true for the Enterobacteriaceae family?

All species ferment lactose Signup and view all the answers

Which pairing of disease and bacterium is incorrectly matched?

Enterobacter - Tuberculosis Signup and view all the answers

What is a general characteristic of Salmonella?

H2S producing from thiosulfate Signup and view all the answers

How are Salmonella species classified according to the Kauffman-White schema?

Using O and H antigens Signup and view all the answers

What is the prototype disease for enteric fever caused by Salmonella?

Typhoid fever Signup and view all the answers

Which species is categorized as a non-pathogen in the Salmonella genus?

Salmonella bongori Signup and view all the answers

Which statement about Salmonella’s biochemical properties is accurate?

They are resistant to bile salts Signup and view all the answers

Which of the following Salmonella species is most commonly associated with food poisoning?

Salmonella enteritidis Signup and view all the answers

What is the primary result of enteric infections caused by Salmonella?

Acute gastroenteritis Signup and view all the answers

Study Notes

Gram-Negative Rods: Enterobacteriaceae & Vibrio

Gram-negative bacteria are rod-shaped.
Enterobacteriaceae and Vibrio are families of gram-negative rods.
The diagram shows a labeled cross-section of the digestive tract. It includes organs like the pharynx, oral cavity, esophagus, stomach, liver, gallbladder, pancreas, small intestine, large intestine (colon, cecum, appendix), rectum, and anus.

Shigella

Shigella are gram-negative, nonmotile, facultative anaerobes.
Four species are discussed: Shigella sonnei, Shigella flexneri, Shigella boydii, and Shigella dysenteriae.
Shigella sonnei is most common in developed countries, and Shigella flexneri is more common in developing countries.
Shigella are non-lactose fermenting and do not produce gas from glucose.
They are resistant to bile salts.
Shigella dysenteriae is a prokaryote, enteric, and facultatively anaerobic rod, frequently found in water contaminated by human feces.
Shigella cause bacillary dysentery or shigellosis, characterized by bloody feces and abdominal pain.
The infection invades the intestinal epithelium but doesn't penetrate.
This leads to dysentery symptoms appearing 2-3 days post-infection, with mucus, blood, and leukocytes (pus) in the stool.
Watery diarrhea can occur alongside dysentery.
Shigella have 4 groups according to O antigens: A, B, C, and D.
Transmission occurs via the fecal-oral route.
Clinical syndromes include shigellosis and its two stages (early and second).

Salmonella

Salmonella are gram-negative, motile, facultative anaerobes, non-lactose fermenting, and resistant to bile salts.
They produce hydrogen sulfide (H₂S) from thiosulfate.
Salmonella can produce acid only or acid and gas.
Salmonella causes salmonellosis, a generic term for disease that can include enteric fever (typhoid fever, less severe paratyphoid fever), salmonella food poisoning, septicemia, and asymptomatic carriage.
The incubation period for gastroenteritis (acute gastroenteritis) is 12 hours-3 days and 10 to 14 days for enteric fever.
Over 2400 O-serotypes (species) based on Kauffman-White antigenic schema.
Biochemical tests assist in classification.
Salmonella are rod-shaped prokaryotes and cause salmonellosis, commonly from food contamination.
Transmission is fecal-oral.
Important in understanding taxonomy and the clinical syndromes of Salmonella infection.

Vibrio Cholerae

Vibrio cholerae is a Gram-negative, curved, motile rod.
It's sensitive to low pH and tolerant to salt, typically found in aquatic habitats.
Transmitted through the oral-fecal route.
High infective dose is needed to cause infection.
Cyclic epidemics are possible.
Diseases caused by various types of Vibrio cholerae are characterized through mapping water supplies, which leads to identifying and fixing the source of the infection.

Helicobacter Pylori

Helicobacter pylori is a curved gram-negative bacterium
It's microaerophilic and acid-tolerant.
It produces urease, lives in the mucus and epithelial surfaces of the human stomach.
Its genome size is 1.7 MB
It is associated with conditions like asymptomatic colonization, chronic atrophic gastritis, peptic ulcer disease, gastric adenocarcinoma, and lymphoma.
Transmission occurs through oral ingestion.
Historically, Dr. Robin Warren and Dr. Barry Marshall successfully cultured H. pylori, which later earned them a Nobel Prize in 2005.
Non-invasive tests like serology, urea breath, and fecal antigen tests can detect H. pylori.
Invasive tests like endoscopy-based histologic examination (biopsy), urease test and culture can also be performed.

Pseudomonas Aeruginosa

Pseudomonas aeruginosa is an opportunistic pathogen in people, plants, insects, etc.
It's a Gram-negative rod found in water and oxygen environments.
Important clinical manifestations include colonization (initial site), severe and disseminated conditions (like pneumonia, cellulitis, etc.).
Pathogenesis is complex and includes virulence factors like alginate, LPS, flagella, pili, and secreted exotoxins (like exotoxin A, elastases, etc.).
It has antimicrobial resistance mechanisms like chromosomal and plasmid-mediated multi-drug efflux pumps.
Biofilm formation by these bacteria is vital to understanding their success and causing disease.

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Description

Test your knowledge on Shigella infections and their characteristics. This quiz covers key topics such as transmission modes, common species in developing countries, symptoms of shigellosis, and incubation periods. Perfect for students learning about microbiology and infectious diseases.