HP and gastroesophageal reflux disease: However, we noticed that 16S rRNA gene analyses were not able to identify all Bifidobacterium species that are present at high abundance in the gut of NUD/GAS-Hp+, NUD/GAS- Hp−, and GERD-Hp− patients but were present at a significantly lower abundance in the gut of CA/GU-Hp+ patients (Figure 6D).