What term is used to describe a strain of bacteria that is capable of causing disease?

The term that accurately describes a strain of bacteria that is capable of causing disease is pathogenic. A pathogenic strain is one that has the ability to invade a host and ultimately lead to an infectious disease. These bacteria possess specific factors, such as toxins or the ability to evade the host's immune defenses, that enable them to cause harm.

While "virulent" may seem like an appropriate answer because it refers to the severity or harmfulness of a pathogen, it does not universally define all disease-causing bacteria. Not all pathogenic strains are highly virulent; some may cause mild infections, while others can lead to severe disease. Therefore, "pathogenic" is the more encompassing and accurate term for the definition provided in the question.

In contrast to pathogenic bacteria, "non-virulent" refers to those that do not cause disease, and "commensal" strains typically live in or on a host without harming it, sometimes providing a benefit. Hence, the specificity of the term "pathogenic" is crucial in accurately depicting the ability of certain bacteria to invoke disease.