Comamonas testosteroni: Is It Still a Rare Human Pathogen

Comamonas testosteroni (formally Pseudomonas testosteroni) is common environmental bacterium that is not part of the human microbiome. Since its identification as a human pathogen in 1987, numerous reports have drizzled in, implicating this organism for various infections. Although these organisms are of low virulence, some of their obscurity perhaps is due to the incapability of clinical laboratories to identify them. Most of the reported cases are bloodstream infections. We report a case of gastroenteritis caused by this organism in a 65-year-old female with colostomy in situ.

Large-scale Enzymatic Synthesis of 12-Ketoursodeoxycholic Acid from Dehydrocholic Acid by Simultaneous Combination of 3α-Hydroxysteroid Dehydrogenase from Pseudomonas testosteroni and 7β-Hydroxysteroid Dehydrogenase from Collinsella aerofaciens

12-Keto-UDCA is an important optically active component for the drug ursodeoxycholic acid (UDCA). Starting from the three-keto compound dehydrocholic acid, the carbonyl groups at position 3 and 7 have to be reduced stereo- and regioselectively. In this case we applied two hydroxysteroid dehydrogenases for this purpose, the NAD-dependent 3α-HSDH from Pseudomonas testosteroni and the NADP-dependent 7β-hydroxysteroid dehydrogenase from Collinsella aerofaciens. Both enzymes can be produced in high yields by an Escherichia coli strain as recombinant proteins. In order to avoid impurities by the 7a-hydroxysteroid dehydrogenase of Escherichia coli, a mutant strain with an inactivated 7a-enzyme was applied for producing the three enzymes. For bioconversion, the dehydrogenases can be used as crude enzyme samples and are applied simultaneously. A 1.8 L batch of 100mM DHCA incubated at pH = 8.0 and 25°C resulted in 80 g crude product with a quite high purity of ≥ 99:5% as judged by HPLC analysis.