A patient presents with a cough that has lasted 5 weeks, accompanied by blood in the sputum and fever. The pathogenic microbe determined to be bacterial is only visible with an acid-fast stain. Based on your knowledge of staining techniques and bacterial cell structure, which antibacterial drug would be appropriate?

• A. Vancomycin.
• B. Bacitracin.
• C. Monobactam.
• D. Isoniazid.

Answer: (D)

Verified step by step guidance

1. Identify the characteristics of the bacterium based on the clinical presentation and staining technique: a cough lasting several weeks with blood in sputum and fever suggests a chronic respiratory infection, and the bacterium is acid-fast positive, indicating it has a waxy, mycolic acid-rich cell wall typical of Mycobacterium species.
2. Recall that acid-fast staining is specifically used to detect bacteria with mycolic acid in their cell walls, such as Mycobacterium tuberculosis, the causative agent of tuberculosis, which fits the clinical picture described.
3. Understand that common antibiotics like Vancomycin, Bacitracin, and Monobactam target bacteria with typical peptidoglycan cell walls and are generally ineffective against mycobacteria due to their unique cell wall structure.
4. Recognize that Isoniazid is a first-line antitubercular drug that specifically inhibits the synthesis of mycolic acids, which are essential components of the mycobacterial cell wall, making it effective against acid-fast bacteria like Mycobacterium tuberculosis.
5. Conclude that based on the acid-fast staining result and the clinical symptoms, the appropriate antibacterial drug is Isoniazid, as it targets the unique cell wall structure of the pathogen.