Shigella and Salmonella MCQs

Heterophile antibodies are typically detected in the Weil-Felix test, which is used to identify certain types of rickettsial infections. The Widal test is used for typhoid fever, and standard agglutination tests are used for various bacterial infections. Key Takeaway: The Weil-Felix test is associated with the detection of heterophile antibodies. Tag: Good to know Tag Line: Easy Reference: Apurva Shastri, Review of Microbiology and Immunology , chapter 12 on antigens – antibody reaction.PP-152.

Principle: It is an agglutination test where H and 0 antibodies against S. Typhi and S. Paratyphi A and B are detected and measured in the patient's sera by using O and H antigens. Reference : Ananthnarayan and Paniker's textbook of Microbiology 12 th edition pg no.300-301

Recommended transport medium for stool specimen is: Sach’s Buffered glycerol saline medium (when Salmonella spp. or Shigella spp. are suspected) Venkatraman Ramkrisnan (VR) medium/ Carry Blair (CB) medium (when Vibrio cholerae is suspected). Reference : Ananthanarayan and Paniker's Textbook of Microbiology 10th edition Chapter 4, Pg 40-45

Ekiri syndrome is a complication seen in Shigellosis. It is most commonly seen in children. It is also called toxic encephalopathy and manifests as altered sensorium, seizures, delirium etc. Reference : Ananthnarayan and Paniker's textbook of Microbiology 12 th edition pg no.481

Explanation: The clinical presentation is classic for enteric fever (typhoid fever caused by Salmonella Typhi). The optimal diagnostic test depends on the duration of illness (mnemonic: BASU ): Week 1: Blood culture (highest yield) (Option C ruled out) Week 2: Antibody test (Widal test) . Antibodies (O and H agglutinins) become detectable. Week 3: Stool culture (organism is shed in feces) (Option B ruled out) Week 4: Urine culture (Option D ruled out) At 2 weeks , the Widal test (demonstrating a rising antibody titer) is the most appropriate serological test. Key Takeaways: Use the BASU mnemonic for diagnosing enteric fever based on week of illness. Blood culture is best early; Widal test is best in the second week.

Explanation: Wilson & Blair medium is a selective agar designed to isolate and identify Salmonella species, particularly Salmonella typhi . The medium contains brilliant green , which suppresses the growth of most other bacteria while allowing Salmonella to grow. It also facilitates identification based on distinctive colony morphology . Explanation of Other Options: PLET medium (Option A): Used for the isolation of Listeria monocytogenes , not Salmonella. BCYE medium (Option B): Buffered Charcoal Yeast Extract (BCYE) agar is intended for Legionella species isolation, not for Salmonella. Stuart's medium (Option D): A transport medium for maintaining pathogen viability during specimen transport; it is not used for Salmonella isolation . Reference: Oxoid - Product Detail

In uncomplicated NTS gastroenteritis, treatment is conservative with fluid replacement. Antibiotic use is associated with increased rates of carriers and relapse, hence is limited to invasive cases only. Reference : Ananthnarayan and Paniker's textbook of Microbiology 12 th edition pg no.480

Patients expressing HLAB27 typically develop autoimmune reactive arthritis after shigellosis. It typically occurs in males less than 40 years of age. The clinical features include early morning arthritis, ocular inflammation and urethritis, classically remembered as can't see, can't pee, can't climb a tree. HLAB54 is associated with Behcet's disease and HLADR04 with Rheumatoid arthritis. Reference: Essentials of Medical Microbiology, by Apurba Sastry and Sandhya Bhat, 3rd edition, page 434