Table 1 Evidence collected from human trials indicating associations among different bacterial species and metabolic markers in NAFLD patients

Wong et al. 2013 [10]

16S rRNA pyrosequencing

HP-NASH:16, HC:22

18 to 70 years

Anaerosporobacter in addition with Faecalibacterium were less prevalent in the feces of NASH affected individuals in comparison to normal control groups; however, Parabacteroides and Allisonella were more prevalent.

Mouzaki et al. 2013 [11]

Quantitative real-time PCR

SS:11, NASH:22, HC:17

>18 years

Patients with NASH had more fecal C. coccoides than those with SS and a reduced quantity of Bacteroidetes than those with SS and HC.

Jiang et al. 2015 [12]

16S rRNA Illumina next-generation sequencing

NAFLD:53, HC:32

22–72 years

The gut microbiota of healthy people had significantly more members of five genera compared to NAFLD patients, including Alistipes, Prevotella, Odoribacter, Flavonifractor, and Oscillibacter. As opposed to this, the gut microflora of NAFLD individuals had greater amounts of Escherichia, Anaerobacter, Lactobacillus, and Streptococcus than that of healthy individuals.

Boursier et al. 2016 [13]

16S rRNA gene sequencing

BP-NAFLD:57

60 years

Prevotella abundance reduced whereas Bacteroides abundance considerably increased in NASH and the prevalence of Ruminococcus was noticeably higher in comparison to normal control groups.

Wang et al. 2016 [14]

454 pyrosequencing of the 16S rRNA

NAFLD:43,HC:83

33 to 61 years

In comparison to control groups, the reduction of beneficial Firmicutes, including SCFAs-producing Lachnospiraceae, 7α-dehydroxylating Ruminococcaceae, and beneficial Lactobacillaceae, was observed in NAFLD patients alongside an increase in potentially pathogenic bacteria capable of producing lipopolysaccharides.

Shen F et al. 2017 [15]

16S rDNA amplicon sequencing

NAFLD:25, HC:22

>18 years

In NAFLD patients, the Fusobacteria and Proteobacteria phyla were too prevalent than in the HC. Additionally, the NAFLD group enriched the Streptococcaceae, Enterobacteriaceae, Erysipelotrichaceae, and Lachnospiraceae families, along with the Lachnospiraceae Incertae Sedis, Escherichia Shigella, and Blautia genera.

Del Chierico et al. 2017 [16]

16S rRNA pyrosequencing

NAFLD:61, HC:51

7 to 16 years

Actinobacteria were substantially raised in NAFLD patients as compared to HC, while Bacteroidetes were lower. When compared to controls, NAFLD patients showed higher amounts of Ruminococcus, Bradyrhizobium, Dorea, Peptoniphilus, Anaerococcus, and Propionibacterium acnes and lower amounts of Rikenellaceae and Oscillospira.

Hoyles et al. 2018 [17]

Shotgun metagenomic sequencing

BP-NAFLD women: 56

70 years

Greater amounts of Actinobacteria and Proteobacteria in individuals with steatosis as compared to normal control groups.

Caussy et al. 2018 [18]

Shotgun metagenomics sequencing

BP-NAFLD:156

>18 years

Elevated levels of Proteobacteria, Furmicutes, and Bacteroidetes among NAFLD individuals as compared to normal control groups.

Li et al. 2018 [19]

16S rDNA sequencing

NAFLD:30, HC:37

>18 years

NAFLD patients showed an increase in Firmicutes, higher relative abundance of Lactobacillaceae, Veillonellaceae, and Dorea, as well as elevated levels of Gammaproteobacteria and Erysipelotrichi compared to the control group.

Schwimmer et al. 2019 [20]

Metagenomic shotgun sequencing and 16S rRNA amplicon sequencing

BP-NAFLD children: 87, obese children without NAFLD: 37

8 to 17 years

Lactobacillus and Oribacterium were prevalent in NASH patients, but Oscillibacter, Akkermansia, Lactonifactor, and Enterococcus were more common in people with NAFLD but not NASH.

Tsai et al. 2020 [21]

16S rRNA gene sequencing

NAFLD:25, NASH:25, HC:25

18–70 years

Bacteroidetes levels were greater and Firmicutes amounts were decreased in NAFLD individuals. In comparison to healthy people, patients with NAFL or NASH had lower concentrations of the genus Ruminococcaceae UCG-010, class Clostridia.

Daud et al. 2022 [22]

16S rRNA next-generation Sequencing

NAFLD:21, HC:13

>18 years

The NAFLD group showed lower Firmicutes prevalence but higher Enterobacter abundance as compared to control groups; additionally, Bifidobacterium quantity showed an inverse correlation with NAFLD severity.

Li X et al. 2023 [23]

Combination of metagenome sequencing and LC-MS

HCC: 68, LC: 33, HC: 34

>18 years

Elevated levels of O. splanchnicus and R. bicirculans, as well as five important metabolites: taurochenodeoxycholic acid, ouabain, xanthine, theophylline, and glycochenodeoxycholate related to HCC.