Vibrio and Campylobacterales MCQs

Explanation: Cholera toxin is produced by Vibrio cholerae and is the main factor responsible for watery diarrhea in cholera. The toxin attaches to receptors on the intestinal epithelial surface and enters the cells. The specific receptor is GM1 ganglioside , a glycosphingolipid located in the intestinal cell membrane. Binding to GM1 initiates endocytosis of the toxin. Inside the cell, the toxin disrupts ion transport, causing massive fluid loss and diarrhea. Explanation of other options: GLUT1 (Option A): Facilitates glucose transport across membranes; not a receptor for cholera toxin. GM2 ganglioside (Option B): A glycosphingolipid, but not the binding site for cholera toxin. Cephalin (Option C): A membrane phospholipid, unrelated to cholera toxin entry. Reference: https://pmc.ncbi.nlm.nih.gov/articles/PMC3089049/

Halophilic vibrios can withstand higher salt concentration (>6%) in contrast to V. cholerae, which can tolerate upto 6%. They are widespread in marine environment. Kanagawa phenomenon: It causes hemolysis on Wagatsuma agar (a special type of high salt blood agar). Reference : Ananthnarayan and Paniker's textbook of Microbiology 12 th edition pg no.487

Tetracycline is the drug of choice and is indicated in household contacts during epidemic.

Ans. is 'd' i.e., Alkaline peptone water om

Vibrio vulnificus: Cutaneous Infection Apart from sepsis, V. vulnificus can also cause primary wound infection (Vulnificus is Latin word for "wound maker" ). Characterized by painful erythematous swelling or cellulitis or even vesicular, bullous or necrotic lesions. It generally affects people without underlying disease, in contrast to sepsis, which is usually observed in patients with underlying disease such as liver disease, iron overload or immunosuppression. Wound infections can also be produced by Vibrio parahaemolyticus. Other options are less likely in comparison to vibrio vulnificus to cause wound infection. Reference: Essentials of Medical Microbiology, by Apurba Sastry and Sandhya Bhat, 3rd edition, page no. 417

Parahemolyticus shows kanagawa phenomenon on Wagatsuma agar. It grows in upto 8% salt solution, shows swarming growth on blood agar. It is known to cause invasive diarrhea. Reference : Essentials of Medical Microbiology, by Apurba Sastry and Sandhya Bhat, 3rd edition, page 417

The above image depicts string test, shown by Vibrio Cholerae. A suspension of the bacteria, along with bile salts gives a positive test. Along with this, Vibrio also shows a positive nitrate reduction test. On a wet mount, it gives a FISH IN STREAM appearance. It is a non- fastidious bacteria. Transport media include autoclaved sea water and VR media. Enrichment media includes Alkaline peptone water and Monsur's taurocholate tellurite agar. Selective media are TCBS, where V.cholerae show yellow colonies and Monsur's GTTA. they are late lactose fermenters. Other options- Kanagawa phenomena is shown by V. parahaemolyticus Black colonies on Tinsdale media are shown by C. diphtheria School of fish appearance is shown by H.ducreyi, while V.cholera shows Fish in stream Appearance Reference : Essentials of Medical Microbiology, by Apurba Sastry and Sandhya Bhat, 3rd edition, page 414

Campylobacter Growth Conditions Microaerophilic Environment: Campylobacter species thrive in a specific atmospheric condition of 5% O2, 85% N2, and 10% CO2 . Unsuitable Conditions: Other oxygen levels or gas compositions do not support the growth of microaerophilic bacteria like Campylobacter. KEY TAKE AWAY: Campylobacter, Helicobacter and Actinomyces Israeli - microaerophilic, require- 5% O2 , 85% N2 and 10% CO2 . Tags: inicet 2022 Reference: Shashtri A. Review of Microbiology and Immunology . 3rd Edition. Chapter: (General Bacteriology), Page no. 25-51.