**4.1 Culture-dependent identification of gastric microbiota**

Initial studies on the bacteria present in the stomach, using culture-based techniques, such as gastric juice cultures and mucosal biopsies were reported even before the isolation of *H. pylori*. In 1977 Savage DC [17] isolated bacteria from the stomach estimated at >103 CFU/g. The predominant phyla were *Firmicutes* (genera *Lactobacillus*, *Streptococcus*, *Clostridium*, and *Veillonella*), *Actinobacteria* (genus *Bifidobacterium*), and *Proteobacteria* (*coliforms*). However, due to the fact that these bacteria are prevalent along the whole GI tract, they were considered transient bacteria, which form small colonies that exist for short periods of time, rather than true gastric colonizers. Later culture-based studies [18–23] find that the most prevalent phylum, regardless of *H. pylori* status, is *Firmicutes*, followed by *Proteobacteria* and *Bacteroidetes*. *Actinobacteria* varies in studies as the second or third most prevalent phylum. The most commonly found genera were *Streptococcus*, *Lactobacillus*, *Bacteroides*, *Staphylococcus*, *Veillonella*, *Corynebacterium*, and *Neisseria*. However, given that culturing conditions for the majority of microbes colonizing the GI tract are not established, culture-based methods are considered to underestimate the gastric microbial diversity and are largely replaced by culture-independent methods.
