TB: analysis, thinking out loud

This section's lecture is a case study on Tuberculosis which I'm excited about, having spent the past two months plus processing and reporting AFB cultures. Our first assignment is on an article about a Nepalese patient who was detained while attempting to illegally enter the U.S. He'd travelled extensively, including an eight-hour flight to Brazil carrying with him a very rare strain of TB called XDR. The XDR strain of TB arises from misuse or mismanagement of second-line antibiotics in treatment of MDR-TB, which is a result of misuse of first-line antibiotics for TB. 

This reminded me of a patient we had of Chinese descent. He presented with a mixed mycobacterium infection. One culture with MAC and the other with MTB. The physician called furiously stating his patient had no symptoms of TB. However, the patient was a previous positive TB patient. Subsequent cultures included pure isolated MAC and MTB as well as mixed cultures of MAC/MTB.

The DOH susceptibilities reported resistance to all first-line antibiotics. After delayed testing and months of pending results, the final report returned with Susceptible results to second-line antibiotics with a few resistant results. 

I remember wondering how could a seemingly asymptomatic patient present with MDR-TB. My hypothesis was of two: the susceptibility results were skewed because of the mixed cultures, and two, the patient's co-infection with MAC and MTB resulted in plasmid exchange in the DNA of each bacilli producing resistance. Neither hypothesis was tested or further evaluated. I pretty much resumed with life as usual.

Today's assignment however revisits my hypothesis and provides a valid explanation. This patient presented with a recurrent TB infection which indicates a latent infection or an active infection that was not fully treated. Misuse of first-line antibiotics led to his current MDR-TB infection.