Which of the following bloodborne pathogens has become drug-resistant and is considered a "superbug"?

The identification of Methicillin-resistant Staphylococcus aureus, commonly known as MRSA, as a "superbug" is accurate due to its notable resistance to methicillin and other antibiotics. This characteristic makes MRSA a significant public health concern, as it can lead to infections that are more difficult to treat compared to other strains of Staphylococcus aureus that are sensitive to standard antibiotics.

MRSA is typically spread through direct contact with an infected wound or contaminated hands and surfaces, leading to skin infections, pneumonia, and other serious conditions. The term "superbug" refers to bacteria that have developed resistance to multiple antibiotics, posing a challenge in both treatment and infection control. The rise of MRSA emphasizes the importance of proper hygiene, infection prevention protocols, and responsible antibiotic use.

On the other hand, while Clostridium difficile can cause serious gastrointestinal infections, it is not classified as a superbug in the same context. Hepatitis C virus and Human Immunodeficiency Virus, though critical public health concerns, are viruses and do not fit into the category of antibiotic-resistant bacteria. Thus, MRSA is rightly recognized as the superbug among the choices provided.