A traveler returning from Southeast Asia presents with fever, headache, and a maculopapular rash that started on the trunk and spread to the extremities, including the palms and soles. Serological testing is positive for Orientia tsutsugamushi. The vector responsible for transmitting this organism is a:
A microbiology laboratory is processing a sputum sample from a patient with chronic cough and night sweats. After Ziehl-Neelsen staining, acid-fast bacilli are observed. Culture on Lowenstein-Jensen medium is positive after several weeks. Drug susceptibility testing reveals resistance to isoniazid and rifampin. This patient is MOST likely infected with:
A 6-year-old child presents with a pharyngitis characterized by a grayish-white pseudomembrane covering the tonsils and posterior pharynx. Gram stain of the membrane reveals Gram-positive bacilli. Culture on Loeffler's medium shows growth of metachromatic granules. The MOST significant virulence factor associated with this organism's pathogenicity is:
An immunocompromised patient returning from a trip to the southwestern United States presents with fever, cough, and chest pain. Chest X-ray shows diffuse pulmonary infiltrates. Sputum culture grows a dimorphic fungus that forms spherules containing endospores at 37°C. The MOST likely causative agent is:
A patient with a history of solid organ transplantation develops diarrhea and abdominal cramps. Stool studies are negative for bacterial pathogens and C. difficile toxins. Colonoscopy reveals characteristic cytomegalic inclusion bodies in colonic biopsies. The MOST likely causative agent is:
A Gram stain of anaerobic growth from a peritoneal fluid abscess reveals pleomorphic, pale-staining Gram-negative rods. The isolate grows on Bacteroides Bile Esculin (BBE) agar, hydrolyzing esculin (producing black colonies), and is resistant to kanamycin (1000 µg), vancomycin (5 µg), and colistin (10 µg) disks. Which organism group is most likely?
Acyclovir is a commonly used antiviral agent effective against Herpes Simplex Virus (HSV) and Varicella-Zoster Virus (VZV). Its selective toxicity relies on which initial step for activation within infected cells?
A microbiology laboratory is investigating a possible outbreak of Salmonella infection. Serological testing of patient isolates reveals they all possess the same O antigen but different H antigens. This suggests:
Staphylococcus epidermidis, a common cause of healthcare-associated infections, forms biofilms on medical devices. The production of polysaccharide intercellular adhesin (PIA) is a key factor in biofilm maturation. The expression of PIA is primarily regulated by:
The gut microbiome has been implicated in the pathogenesis of autoimmune diseases. Dysbiosis, a disruption in the composition and function of the gut microbiota, can lead to increased intestinal permeability and the translocation of microbial products that trigger inflammatory responses. Which of the following bacterial components is a potent activator of the innate immune system and has been linked to the development of autoimmunity?
