To provide a comprehensive analysis of the fecal microbiota in infants with colic, as compared with control infants, during their first 100 days of life.
Microbial DNA of >200 samples from 12 infants with colic and 12 age-matched control infants was extracted and hybridized to a phylogenetic microarray.
Microbiota diversity gradually increased after birth only in the control group; moreover, in the first weeks, the diversity of the colic group was significantly lower than that of the control group. The stability of the successive samples also appeared to be significantly lower in the infants with colic for the first weeks. Further analyses revealed which bacterial groups were responsible for colic-related differences in microbiota at age 1 or 2 weeks, the earliest ages with significant differences. Proteobacteria were significantly increased in infants with colic compared with control infants, with a relative abundance that was more than twofold. In contrast, bifidobacteria and lactobacilli were significantly reduced in infants with colic. Moreover, the colic phenotype correlated positively with specific groups of proteobacteria, including bacteria related to Escherichia, Klebsiella, Serratia, Vibrio, Yersinia, and Pseudomonas, but negatively with bacteria belonging to the Bacteroidetes and Firmicutes phyla, the latter of which includes some lactobacilli and canonical groups known to produce butyrate and lactate.
The results indicate the presence of microbial signatures in the first weeks of life in infants who later develop colic. These microbial signatures may be used to understand the excessive crying. The results offer opportunities for early diagnostics as well as for developing specific therapies.
Comments
Questions Re: Study Design and Interpretation
The recent article by de Weerth and colleagues (1) suggests that early differences in the intestinal microbiota of infants who later do or do not develop colic may partially explain the crying behavior in these two groups. Several clarifications are needed before accepting this proposition. Because of the small sample size and the well-known differences in the fecal flora of breastfed and formula fed infants (2), it would be important to know what formulas were fed to the 4 infants in the colic group and 2 in the control group who were not breastfed. Given the large variability in duration of breastfeeding (Table 1), were any colicky infants initially breastfed, but changed to formula in the early weeks of life?
It appears there were 26 infants with colic from whom fecal samples were available (p. e552). Why did the authors choose to include data from only 12 when they could have more than doubled the sample size of both groups of infants? What is the biological rationale of comparing only the infants who cried the most with those who cried the least? Presumably, the authors thought that comparing the two extremes would increase the likelihood of finding a difference. Barr (3) has pointed out the conundrum we face when using an absolute cut off to distinguish "normal" from "abnormal" crying behavior, since crying can be both a normal behavior and a manifestation of illness. His data suggest that there are some infants with colic who cry <3 hrs/d and some who cry >3 hrs/d who may not have colic.(4) If, however, one uses Wessel's criteria, as the authors did in this study, there seems to be no reason not to include all of the colicky infants.
A link between the degree of diversity of the intestinal microbiota and colic would ideally rely on a temporal association between the two. Here again, additional information would be helpful. The crying behavior diaries were appropriately obtained at 6 weeks; given the aim of the study why were there no concurrent fecal samples? We are provided analyses of a diversity index, a similarity index, a redundancy analysis and, in supplemental material, relative abundance of phyla and of specific bacterial groups. Is there a (micro)biological reason to believe one of these measures of "diversity" or specific "signatures" is more likely to explain differences in crying behavior in colicky and control infants? Overall, there were relatively few significant differences between the groups (discounting P values with asterisks denoting 0.1 > P > 0.05). Figure 2 shows the only differences between colic and control occurred at 14 and 28 days, not thereafter; Figure 3 shows the only difference occurring at 7 to 14 days. It seems highly speculative to suggest that differences in the microbiota at those early ages, which were not documented later, explain the later differences in crying behavior in the two groups. While the data are provocative, any conclusions must remain tentative until more infants have been studied with suitably-timed crying diaries and microbiota samples.
1.de Weerth C., Fuentes S, Puylaert P and de Vos M. Intestinal microbiota of infants with colic: development and specific signatures. Pediatrics 2013;131:e550-e558.
2. Fanaro S, Chierici R, Guerrini P and Vigi, V. Intestinal microflora in early infancy: composition and development. Acta Paediatr Suppl 2003;441:48-55
3. Barr RG. Normality: a clinically useless concept. The case of infant crying and colic. J Dev Behav Ped 1993;14:264-70.
4. Barr RG, Rotman A, Leduc D et. Al The crying of infants with colic: a controlled empirical description. Pediatrics 1992;90:14-21.
Conflict of Interest:
None declared