Review for 10.1186/1471-230X-14-126 (2014)

Reviewer's report
Title:The effect of virulence factors on the pathogenicity of Staphylococcus
epidermidis on the intestinal organs of rats and mice: an experimental
investigation
Version:2Date:2 March 2014
Reviewer: Atte von Wright
Reviewer's report:
The manuscript describes a straightforward rodent feeding trial to assess the
pathogenicity of Staphylococcus epidermidis isolates displaying different putative
virulence factors. According to the results daily doses of 2 x 10*9 cfu/ml for 14
days resulted in mortalities of 3 -4 animlas in test groups of seven.
Histopathological changes were observed in liver, kidneys, spleen and
gastrointestinal tract. The severity of histopathological lesions roughly correlated
with the number of potential virulence factors. While the experimental work
appears sound, the authors should discuss the relevance of their findings for
actual human infections, as well as address the specific points outlined below:
Major revisions
1) In the abstract the overall mortality in the chronic experiments is stated as 11
out of 28 mice. However, since 7 mice served as controls and did not receive the
bacterial suspensions, the correct treatment related mortality is actually 11 out of
21 mice. The dosage in abstract has been given as cfus/ml, while in the text the
dosages have been expresses as cfus/kg. The latter units should also be used in
the Abstract.
2) In the introduction it is stated the S. epidermidis is a prominent part of the
normal flora of the gut. Some quantitative figures should be given (how many
cfus per g gut content?)
3) In Methods the bacterial isolates should be given proper strain designations or
codes (such as strain collection codes) and these codes should be consistently
used in reporting the results
4) In Methods the bacterial doses adminstered intraperitoneally should be clearly
indicated
5) The histopathological data should be reported in more details, preferably using
tabular presentation. Since the number of animals is relatively limited, tabulating
the findings of each animal is recommended.
6) The authors should clarify in Discussion why no haematology or clinical
chemistry was included in the test regime, why no atttempt was made to check,
whether there had been any invasion of S. epidermidis into the circulation or
whether the bacteria had actually colonised the intestinal tracts.
7) Although the language is generally understandable, there should be an
extesive check, preferably by a native English speaker of the revised manuscript.
At present some paragraphs are clumsy and create wrong imprssion (fro
example in Methods, in section Bacterial Isolates, expressions like "..the third
was from a child from the same health centre showing one virulence factor
expressed as biofilm production." indicate that either the child or the health
centre, rather than the bacterial isolate, displays the biofilme production
phenotype )
Level of interest: An article whose findings are important to those with closely
related research interests
Quality of written English: Not suitable for publication unless extensively edited
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