Follow-up Survey Of Clostridium Difficile Colonization In Infants And Effects Of Clostridium Difficile Colonization On Intestinal Flora In 6-month-old Infants

Part one Follow-up survey of Clostridium difficile colonization in infantsObjective: Clostridium difficile(CD)is an obligate anaerobic grampositive bacillus generally considered to be the normal flora of the human intestine.The bacteria are mainly transmitted through the faecal-oral route.C.difficile could be asymptomatically colonized in infants for a long period of time,however the cause and influencing factors of colonization are still far more limited.We conducted a 1-year follow-up survey in infants in Shijiazhuang City,Hebei Province to understand the dynamic changes of C.difficile colonization and the influencing factors.Methods:1 A total of 538 stool specimens from 34 infants were collected from December 2016 to March 2018 in Shijiazhuang City,Hebei Province.Fresh stool specimens were collected at 16 points.Basic information was recorded.2 The enriched spore method was used to separate,culture and identify for C.difficile.C.difficile isolates were typed by PCR-ribotyping and analyzed for the presence of toxin genes.3 Antimicrobial susceptibility testing was performed on 11 antibiotics involved levofloxacin,ciprofloxacin,ceftriaxone,meropenem,clindamycin,tetracycline,chloramphenicol,metronidazole,vancomycin,fidaxomicin and tigecycline for the minimum inhibitory concentration(MIC).Results:1.27 of the 34 enrolled infants acquired C.difficile during the first year of life.145 fecal specimens contained C.difficile of total 538 specimens(27.0%,145/538),and 90 were toxigenic strains(62.1%,90/145).2.145 strains were divided into 17 ribotypes.HB2 accounted for thelargest proportion of all ribotypes,accounting for 16.6% of all strains,followed by HB1(11.0%),HB6(11.0%),HB12(10.3%).HB1 and HB6 accounted for the most in toxigenic strains,HB2 accounted for the most in non-toxigenic strains.3.All isolates were highly susceptible to metronidazole,vancomycin,fidaxomicin,tigecycline and meropenem.The resistance rate of clindamycin,ciprofloxacin,and ceftriaxone were 96.3%,71.6%,and 25%,respectively.The resistance rates of chloramphenicol(11.3%),tetracycline(3.7%),and levofloxacin(2.5%)were low,respectively.Conclusions: The colonization rate of C.difficile in infants in Shijiazhuang City,Hebei Province was 27.0%,and toxigenic C.difficile was62.1%.The colonization rate of C.difficile in infants increased with age.17 ribotypes were identified,HB1 and HB6 accounted for the most in toxigenic C.difficile while HB2 accounted for the most in non-toxigenic C.difficile.The C.difficile isolated from infants were highly susceptible to meropenem,and the resistance rates of tetracycline and levofloxacin were relatively low.Part two Effects of Clostridium difficile colonization on the intestinal flora in 6-month-old infantsObjective: Infancy is a critical period for the establishment of intestinal flora,and there is a certain relationship between C.difficile colonization and intestinal flora of infants.However,at present,the effects of C.difficile colonization on the intestinal flora of infants in Shijiazhuang City,Hebei Province is still lacking.In this study,we used 16 S rRNA gene highthroughput sequencing technology to analyze the intestinal flora of 6-monthold infants,and then to understand whether C.difficile colonization has an effect on the intestinal flora in 6-month-old infants.Methods:1 10 infants with C.difficile colonization and 10 infants without C.difficile colonization within 6 months of age in the first part of the experiment were included.Fresh stool specimens were collected at 6 months of age.Basicinformation was recorded.2 The enriched spore method was used to separate,culture and identify for C.difficile.C.difficile isolates were analyzed for the presence of toxin genes.3 Fecal genomic DNA was analyzed by V3 and V4 regions of 16 S rRNA gene results.Results:1.C.difficile colonization had no significant effect on the composition of intestinal flora in 6-month-old infants.2.At the phylum level,the intestinal flora were mainly consisted of Proteobacteria,Firmicutes,Actinobacteria and Bacteroidetes.Firmicutes was the most portion in infants with C.difficile colonization,while Proteobacteria was the most portion in infants without C.difficile colonization.At the genus level,Escherichia/Shigella,Bifidobacterium and Veillonella accounted nearly70%.Veillonella was the most portion in infants with C.difficile colonization,while Escherichia/Shigella was the most portion in infants without C.difficile colonization.3.The significant microbial groups were Clostridiales,Clostridia,Lachnospiraceae,Lachnospiracea_incertae_sedis,Clostridium_XlVa,Ruminoc occaceae,and Flavonifractor in group with C.difficile colonization,were Haemophilus,Pasteurellales and Pasteurellaceae in group without C.difficile colonization.Conclusions: The presence or absence of C.difficile colonization had little effect on the intestinal flora in 6-month-old infants.