A 23-year old medical student arrives in the student health clinic complaining of difficult in swallowing, sore throat, and chills. Upon examination, she is found to be running a fever and has white patches on her tonsils. A throat swab is positive for streptococcus pyogenes (group A). A diagnosis of acute pharyngitis is made. Her past medical history is unremarkable except an anaphylactic reaction to cefaclor two years ago. Which of the following would be a safe alternative for treating?

Correct Answer: D

Rationale: The correct answer is D: Clindamycin. Clindamycin is a lincosamide antibiotic that is safe to use in patients with a history of anaphylaxis to beta-lactam antibiotics like cefaclor. Clindamycin is effective against streptococcus pyogenes and is a suitable alternative in this case. Amoxicillin (choice A) is a beta-lactam antibiotic similar to cefaclor and may cause a cross-reactive allergic reaction. Meropenem (choice B) is a carbapenem antibiotic and not typically used for acute pharyngitis. Cephalexin (choice C) is a cephalosporin antibiotic and may also cause cross-reactivity in patients with a history of anaphylaxis to cefaclor.

Correct Answer: A

Rationale: The correct answer is A: pharmacotherapeutics. Pharmacotherapeutics focuses on the selection and use of drugs for disease prevention, treatment, and diagnosis. It involves determining the most effective and safe medications for specific conditions based on patient factors. Toxicology (B) is the study of the adverse effects of chemicals, including drugs. Pharmacokinetics (C) focuses on drug absorption, distribution, metabolism, and excretion in the body. Pharmacy (D) involves the preparation and dispensing of medications, but does not specifically address drug selection and application for disease management. Therefore, pharmacotherapeutics is the most suitable discipline for addressing the use of drugs in disease management.

Correct Answer: B

Rationale: The correct answer is B: Clostridium perfringens. In this case, the patient's presentation of infected wound with tissue crepitation, foul odor, and Gram-positive bacteria with centrally located spores that cannot grow in the presence of oxygen is indicative of gas gangrene caused by Clostridium perfringens. This anaerobic bacterium produces various toxins that lead to tissue destruction and gas production in the affected area. Clostridium tetani (choice A) causes tetanus, characterized by muscle stiffness and spasms. Clostridium botulinum (choice C) causes botulism, leading to muscle paralysis. Clostridium difficile (choice D) is associated with antibiotic-associated diarrhea. These choices are incorrect as they do not match the clinical presentation described in the question.

Correct Answer: B

Rationale: The correct answer is B: Bordetella pertussis. This bacterium causes whooping cough by infecting the respiratory tract. It produces toxins that lead to severe coughing fits characteristic of the disease. Clostridium botulinum (A) causes botulism, Streptococcus pneumoniae (C) causes pneumonia, and Neisseria meningitidis (D) causes meningitis, not whooping cough. B. pertussis is the only bacterium specifically associated with whooping cough.

Correct Answer: A

Rationale: Correct Answer: A Rationale: 1. Enteropathogenic E. coli (EPEC) attach to enterocytes via a type III secretion system. 2. Once attached, they form attaching and effacing lesions on the microvilli, leading to microvillus destruction. 3. This mechanism allows EPEC to cause diarrhea by disrupting the normal absorptive function of the intestines. Summary: - B (They are invasive and produce enterotoxin) is incorrect because EPEC are non-invasive and do not produce enterotoxins. - C (Cause disease clinically similar to bacterial) is vague and does not provide specific information about EPEC pathogenesis. - D (None of the above) is incorrect as A is the correct explanation for EPEC pathogenicity.

Correct Answer: B

Rationale: The correct answer is B: Linnaeus. Linnaeus developed the binomial system of nomenclature in the 18th century. This system uses a two-part naming system consisting of the genus and species name to classify and identify organisms. Linnaeus's contribution revolutionized the way organisms are named and classified in the field of biology. Other choices are incorrect as Pasteur is known for his work in microbiology, Martini is not associated with the development of binomial nomenclature, and Jenner is known for developing the smallpox vaccine.

Correct Answer: B

Rationale: The correct answer is B: RG2. RG2 is appropriate for agents associated with human disease that pose a moderate health risk. These agents may cause disease of varying severity, but generally do not result in serious health consequences. Other choices are incorrect because: A: RG1 is for agents not associated with disease in healthy adults, C: RG3 is for agents associated with serious or lethal human disease, and D: RG4 is for agents that pose a high risk of life-threatening disease and for which there are no treatments.

Correct Answer: C

Rationale: The correct answer is C because Endo, Gassner, and Levin are all examples of differential media used in microbiology. These media contain specific components that allow for the differentiation of different types of microorganisms based on their metabolic characteristics or biochemical reactions. Lowenstein-Jensen and Petraniani (choice A) are selective media for mycobacteria, not differential. Apoholate-citrate agar and Brilliant-green phenol-red Lactose agar (choice B) are selective media for Salmonella and E. coli, respectively, not differential. Therefore, the correct choice is C as it includes examples of differential media commonly used for microbial identification.

Correct Answer: C

Rationale: The correct answer is C. Bacterial spores are NOT used for cell division. Bacterial spores are dormant, resistant forms of bacteria that are formed in response to harsh environmental conditions. They are not involved in cell division but rather serve as a survival mechanism for the bacteria. A: They can deform the cell or not - This is true. Bacterial spores can deform the cell or not depending on the conditions. B: They can be terminal, subterminal, and central - This is true. Bacterial spores can be located at different positions within the bacterial cell. D: They are formed for 6-8h - This is incorrect. The formation of bacterial spores can take variable time periods depending on the species and environmental conditions.