Final answer:
For a client with a positive TB skin test, isoniazid is the expected prophylactic medication prescribed by healthcare providers to prevent the progression of tuberculosis.
Step-by-step explanation:
When a client has a positive skin test for tuberculosis, the practical nurse (PN) should expect that isoniazid will be prescribed as a prophylactic drug. Isoniazid is an antimetabolite specifically toxic to mycobacteria and is a cornerstone drug in the prevention and treatment of tuberculosis. It is often used in combination with other antibiotics like rifampin or ethambutol, especially in cases of latent tuberculosis infection to prevent the development of active disease. It is important to note that the presence of a positive tuberculin skin test indicates that the patient has been exposed to the bacteria and exhibits a cellular immune response. This requires careful management and adherence to the medication regimen to prevent the development of drug-resistant TB strains, such as multidrug-resistant tuberculosis (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB).