Bacteriology — MCQs

The toxin of the emetic strain of Bacillus cereus resembles in action which of the following?

A 73-year-old woman with a history of diabetes presents with left ear pain and drainage of pus from the ear canal. She has a swelling and tenderness over the left mastoid bone. Which of the following microorganisms is the MOST likely causative agent?

Tumbling motility is characteristic of which of the following bacteria?

A 60-year-old alcoholic smoker abruptly develops high fever, shakes, a severe headache, and muscle pain. He initially has a dry, insignificant cough, but over the next few days he develops marked shortness of breath requiring assisted ventilation. Chest x-ray demonstrates homogeneous radiographic shadowing that initially involves the left lower lobe but continues to spread until both lungs are extensively involved. Culture of bronchoalveolar lavage fluid on buffered charcoal yeast extract (BCYE) demonstrates a coccobacillary pathogen. Which of the following is the most likely causative organism?

Shiga toxin acts by which mechanism?

All of the following Salmonellae are motile except?

Panton-Valentine leucocidin is seen in infection with which bacterium?

A 2-year-old child presents with fever and vomiting, exhibiting neck rigidity. Cerebrospinal fluid analysis reveals over 2000 polymorphs/mm³, protein of 100 mg/dL, and glucose of 10 mg/dL. Gram stain shows Gram-negative coccobacilli, and culture demonstrates growth only on chocolate agar, not on blood agar. What is the causative agent?

The enzyme glucosyl transferase secreted by Streptococcus mutans synthesizes glucans from what substrate?

An 18-year-old woman presents with diplopia, dysarthria, and dysphagia 18 hours after consuming homemade preserves. Examination reveals cranial nerve palsies affecting extraocular movements, difficulty swallowing, and voice changes. Muscle strength is 4/5 in the arms and 5/5 in the legs, with normal reflexes. What is the most likely causative organism?