Antibiotic resistance in C. difficile
Clostridiodes difficile (often referred to colloquially as "C. diff") causes severe enteric infection. Metronidazole is a commonly-used antibiotic to treat C. diff infection. However, metronidazole-resistant C. difficile has spread rapidly in hospitals around the world. MADELINE and colleagues conducted a genome-wide association study to determine the cause of metranidazole resistance in C. difficile. They found that a mutation in the promotor region of the gene nimB was significantly associated with metronidazole resistance. Interestingly, the nimB promotor mutation co-occurred with a mutation in gyrA. This gyrA mutation is known to give C. diff resistance to another kind of antibiotic, fluoroquinolones. Both mutations were under positive selection. Together, these results illuminate the genetic basis for C. difficile's rapid spread, and that pandemic C.difficile is resistant to multiple antibiotics. Read the paper here.
Biofilm formation in Gardnerella vaginalis
Bacterial vaginosis is the most common vaginal infection. It is caused by Gardnerella vaginalis, a bacterium which grows as a biofilm. Biofilms are complex communities of bacteria which are adherent, slimy films (think dental plaque). MADELINE and colleagues performed experimental evolution by imposing a strong election pressure: only biofilm-growing Gardnerella were propogated, kept alive. As a result, they observed bigger biofilms in evolved Gardnerella populations. MADELINE discovered convergent adaptation in a number of genes important for biofilm formation in Gardnerella vaginalis and evaluated the selective pressures on these loci in natural infection. Manuscript in prep!