In contrast, Bacteroides are abundant in clinical nonresponders.458 Interestingly, when analyzing the fecal microbiome derived from another metastatic melanoma patient cohort treated with anti-PD-1 immunotherapy, a significantly higher abundance of particular bacterial taxa (such as B. longum, Collinsella aerofaciens, and Enterococcus faecium) was detected in clinical responders than in nonresponders. This evidence concerns the gene PDCD1 and metastatic melanoma.