A paramedic would MOST likely be infected with TB if he or she:

The most significant risk of transmitting tuberculosis (TB) in this scenario comes from performing mouth-to-mouth resuscitation on a patient with active untreated TB. Tuberculosis is primarily an airborne infectious disease, spreading through respiratory droplets when an infected person coughs, sneezes, talks, or sings. Engaging in a procedure that involves close contact with the respiratory secretions of an individual with active TB greatly increases the likelihood of inhaling these infectious droplets.

While the other scenarios involve potential risks, they are not as directly connected to the primary mode of transmission for TB. A needlestick injury may pose a risk for bloodborne pathogens but is not the primary concern for TB transmission. Blood-stained vomitus can indicate a variety of conditions, and while it might contain infectious material, TB is not typically spread through such fluids. Being close to a coughing patient with a positive TB skin test indicates exposure, but the actual threat of transmission is much higher during direct inhalation of particles from resuscitation efforts. Therefore, engaging in mouth-to-mouth resuscitation represents the highest likelihood of infection with TB.