Review for 10.1186/1471-230X-14-40 (2014)

Reviewer's report
Title:Changes in Gut Bacterial Populations and Their Translocation into Liver
and Ascites in Alcoholic Liver Cirrhotics
Version:1Date:22 October 2013
Reviewer: Marko Kalliomäki
Reviewer's report:
The authors have studied bacterial microbiota in fecal, liver and ascites samples
by RT-qPCR in patients with alcoholic liver cirrhosis in order to evaluate the role
of intestinal bacteria in the pathogenesis of alcoholic liver cirrhosis. By selecting
untypical p-value of 0.1 as a borderline for statistical significance, the authors
have justified themselves for further statistical comparisons where they found
certain significant differences in the amounts of fecal bacteria between the
patients with cirrhosis / heavy alcohol use and healthy volunteers. Similar
findings have already been published earlier. There were, however, no
statistically significant differences in the amounts of bacteria in other samples
(liver, ascites) between the groups studied. I have the following comments.
Major Compulsatory Revisions
1) Bacterial DNA was also found in the most of the non-alcoholic non-cirrhotic
autopsied patients' livers although there were some statistically non-significant
differences in the relative amounts of bacterial species detected. This suggests
that bacterial translocation per se is not a sufficient inducer of cirrhosis in
alcoholic liver disease. Neither the study supports (possibly due to too small
study cohort) the idea that the amount of bacteria translocated would be
important in the pathogenesis.
2) It is interesting that the expression of CD14, a bacterial recognition receptor, in
liver was increased in the patients with alcoholic liver cirrhosis as compared with
non-alcoholics. The authors state that total bacterial DNA amount in liver
correlate with CD14 expression percentage. This statement, however, is
incorrect since no correlation has been shown in the manuscript. The author did
show that the CD14 expression percentage was increased in those liver samples
where bacterial DNA was also detected as compared with those livers without
bacterial DNA detection. However, CD14 was also expressed in the livers without
detected bacterial DNA. Therefore, either a real correlation curve should be
provided or the text concerning the issue (in the abstract, results and discussion)
should be revised.
3) Bacterial DNA was found in half of the ascites samples. The other half did not
contain bacterial DNA, the issue that should also be briefly discussed. Do the
authors have any explanations for that?
4) The section of conclusions presents the main findings inaccurately (too
optimistically concerning the comments above). Therefore, it should be revised.
Minor Essential and Discretionaty Revisions
5) Page 6 (Materials and Methods) and Table 1. One of the study patients was
17 years old although one of the criteria for study was age over 18 years. This
discrepancy should be corrected.
6) Page 7 (Materials and Methods). Were fecal samples taken also from cecum
as stated in the text?
7) Figure 1. Why were the results concerning Enterobacter sp. not shown in the
figure?
8) Discussion (page 11). It is stated that alcoholics also harbored more
gram-negative Bacteroides and Enterobactericaea than healthy controls although
such results were not presented in the section of results. This discrepancy should
be corrected.
9) Discussion (page 12, the end of the first paragraph). It is stated that the
amounts of certain bacteria were higher in cirrhotic livers that in controls and
alcoholics without cirrhosis. SInce there were no statistically significant
differences in these amounts, the text should be revised.
10) Discussion (page 13, the end of the first paragraph, the second last
sentence). The sentence should be corrected.
11) Figures have been numbered incorrectly (from 2 to 6).
Level of interest: An article of importance in its field
Quality of written English: Acceptable
Statistical review: No, the manuscript does not need to be seen by a statistician.
Declaration of competing interests:
I declare that I have no competing interests