Objective: Our aim was to study the influence of efflux pump systems in the resistance of Mycobacterium tuberculosis to fluoroquinolones and linezolid. Methods: We studied the mutations in gyrA and gyrB genes and the influence of efflux pump systems with 2 inhibitors (reserpine and MC 207.110). Results: The effect of the active efflux system on the decrease in sensitivity to ciprofloxacin, moxifloxacin, levofloxacin, ofloxacin, gatifloxacin and linezolid was studied by investigating the variation in the in vitro activity of these compounds when assayed in association with reserpine and MC 207.110. These inhibitors exhibit activity both in strains that are resistant and in strains that are susceptible to these antibiotics. However, they are seen to be most active in resistant strains, since the minimum inhibitory concentration of the antibiotics studied in these strains was reduced between 2- and 6-fold. Conclusions: Therefore, these mechanisms are involved in the resistance to both compounds. It would be of interest to carry out further studies to determine to what extent these active efflux systems influence resistance to the different groups of drugs used in the treatment of tuberculosis, with a view to the possibility of using the inhibitors of these systems in future therapeutic applications.

Urinothorax is a rare cause of transudative pleural effusion secondary to obstructive uropathy. We present a case of urinothorax after shock wave lithotripsy and review the literature. A total of 53 cases have been described previously, and in a few of them, the biochemical characteristics of the pleural fluid were detailed. In general, patients with urinothorax have low pH and glucose levels, and their lactate dehydrogenase level can be very high, resulting in misclassification of the effusion as an exudate. The average pleural fluid to serum creatinine ratio reported in 12 cases was 9.15 (range 1.09–19.8).

The presence of urine in the pleural space (urinothorax) is a rarely recognized cause of pleural effusion. To date, only 58 cases have been reported. In this article the features of urinothorax are analyzed, and clinical and biochemical characteristics are reviewed in order to propose a classification, founded on pathogenic criteria, that will be useful in achieving the diagnosis. Recently reported cases of urinothorax provide a more detailed description of the biochemical characteristics that allow a better understanding of this entity. Urinothorax can be divided into two categories: (1) obstructive urinothorax, due to bilateral obstructive uropathy; and (2) traumatic urinothorax, due to unilateral traumatic injury of the urinary system, mostly iatrogenic. In patients with urinothorax, the pleural effusion usually has the biochemical characteristics of a transudate, with a pH lower than 7.30 and a pleural fluid/serum creatinine ratio higher than 1. These characteristics are not always present, however, and individually are shared by a significant number of pleural effusions of different etiology.