Comparison of bacterial quantities in left and right colon biopsies and faeces

AIM：To compare quantities of predominant and pathogenic bacteria in mucosal and faecal samples.METHODS：Twenty patients undergoing diagnostic colonoscopy with endoscopically and histologically normal mucosa were recruited to the study,14 subjects of which also supplied faecal（F） samples between 15 d to 105 d post colonoscopy.Mucosal biopsies were taken from each subject from the midportion of the ascending colon（right side samples,RM） and the sigmoid（left side samples,LM）.Predominant intestinal and mucosal bacteria including clostridial 16S rRNA gene clusters Ⅳ and ⅩⅣab,Bacteroidetes,Enterobacteriaceae,Bifidobacterium spp.,Akkermansia muciniphila（A.muciniphila）,Veillonella spp.,Collinsella spp.,Faecalibacterium prausnitzii（F.prausnitzii） and putative pathogens such asEscherichia coli（E.coli）,Clostridium difficile（C.difficile）,Helicobacter pylori（H.pylori） and Staphylococcus aureus（S.aureus） were analysed by quantitative polymerase chain reaction（qPCR）.Host DNA was quantified from the mucosal samples with human glyceraldehyde 3-phosphate dehydrogenase gene targeting qPCR.Paired t tests and the Pearson correlation were applied for statistical analysis.RESULTS：The most prominent bacterial groups were clostridial groups Ⅳ and ⅩⅣa＋b andBacteroidetes and bacterial species F.prausnitzii in both sample types.H.pylori and S.aureus were not detected and C.difficile was detected in only one mucosal sample and three faecal samples.E.coli was detected in less than half of the mucosal samples at both sites,but was present in all faecal samples.All detected bacteria,except Enterobacteriaceae,were present at higher levels in the faeces than in the mucosa,but the different locations in the colon presented comparable quantities（RM,LM and F followed byP 1 for RMvs F,P 2 for LMvs F andP 3 for RM vs LM：4.17 ± 0.60 log 10 /g,4.16 ± 0.56 log 10 /g,5.88 ± 1.92 log 10 /g,P 1 = 0.011,P 2 = 0.0069,P 3 = 0.9778 forA.muciniphila;6.25 ± 1.3 log 10 /g,6.09 ± 0.81 log 10 /g,8.84 ± 1.38 log 10 /g,P 1 〈 0.0001,P 2 = 0.0002,P 3 = 0.6893 forBacteroidetes;5.27 ± 1.68 log 10 /g,5.38 ± 2.06 log 10 /g,8.20 ± 1.14 log 10 /g,P 1 〈 0.0001,P 2 ≤ 0.0001,P 3 = 0.7535 forBifidobacterium spp.;6.44 ± 1.15 log 10 /g,6.07 ±1.45 log 10 /g,9.74 ±1.13 log 10 /g,P 1 〈 0.0001,P 2 ≤ 0.0001,P 3 = 0.637 forClostridium cluster Ⅳ;6.65 ± 1.23 log 10 /g,6.57 ± 1.52 log 10 /g,9.13 ± 0.96 log 10 /g,P 1 〈 0.0001,P 2 ≤ 0.0001,P 3 = 0.9317 forClostridium cluster ⅩⅣa;4.57 ± 1.44 log10/g,4.63 ± 1.34 log10/g,7.05 ± 2.48 log 10