Which of the following organisms is classified as a rapid grower in Group IV?

Mycobacterium phlei is accurately classified as a rapid grower in Group IV. This organism is known for its ability to grow relatively quickly when cultured, typically within 7 to 14 days. Rapid growers in this category are generally those mycobacteria that can be differentiated from slower-growing species based on their growth rates when placed in specific culture conditions.

In contrast, other organisms listed do not exhibit the same rapid growth characteristics. Mycobacterium gordonae is considered a slow grower, and it typically requires more time to be detected in culture. Mycobacterium tuberculosis, which is responsible for tuberculosis, is also a slow-growing organism, often taking weeks to grow in culture, making it necessary to employ additional diagnostic techniques for timely detection. Mycobacterium leprae, the causative agent of leprosy, is a unique case as it cannot be cultured in vitro at all. Instead, it typically requires living host cells for growth.

Understanding the growth characteristics of these organisms is crucial in microbiology, as it assists in the diagnosis and identification of mycobacterial infections in clinical settings. Recognizing Mycobacterium phlei as a rapid grower is beneficial for laboratory processes and timely patient management.