Author's response to reviews

Author's response to reviews Title: The Influence of Chronic Renal Failure on the Spectrum and Antimicrobial Susceptibility of Uropathogens in Community-Acquired Acute Pyelonephritis Presenting as a Positive Authors: Yeon Soon Jung (kidneyki@hanmail.net) Ho Sik Shin (danieljoseph@hanmail.net) Hark Rim (kidneyki@naver.com) Version: 2 Date: 18 February 2011 Author's response to reviews: see over

Feb 18 th, 2010 Dear We have recently obtained some data on community-acquired acute pyelonephritis presenting as a positive urine culture. The title of the manuscript is The Influence of Chronic Renal Failure on the Spectrum and Antimicrobial Susceptibility of Uropathogens in Community-Acquired Acute Pyelonephritis Presenting as a Positive. We are enclosing an original copy of the manuscript, consisting of 19 pages of text and seven tables. We wish to submit our manuscript for publication in BMC Infectious Disease. Your kind consideration of this paper would be greatly appreciated. These data have not been reported elsewhere, nor has this manuscript been submitted elsewhere. All authors took part in the work and agree with the contents of the manuscript. Correspondence and phone calls regarding the paper should be directed to me at the following address and phone number: Ho Sik Shin, M.D. Department of Internal Medicine, Kosin University College of Medicine, 34 Amnam-dong, Seo-gu, Busan, 602-702, Korea TEL: +82-51-990-6108. FAX: +82-51-990-3048 E-mail: danieljoseph@hanmail.net Sincerely Yours Ho Sik Shin, M.D. 1

Manuscript ID : 7149067835005615 The Influence of Chronic Renal Failure on the Spectrum and Antimicrobial Susceptibility of Uropathogens in Community-Acquired Acute Pyelonephritis Presenting as a Positive Yeon Soon Jung, M.D., Ho Sik Shin, M.D., and Hark Rim, M.D. Thank you for your appropriate comments We have provided detailed responses to your comments below. We agree with the reviewer's opinion regarding the original version of our manuscript. We have revised the manuscript as recommended and very much appreciate the invaluable advice. If you have any additional recommendations, we will make every effort to revise the manuscript accordingly. We are looking forward to your response. <Reviewer 1> Reviewer's report Title: The Influence of Chronic Renal Failure on the Spectrum and Antimicrobial Susceptibility of Uropathogens in Community-Acquired Acute Pyelonephritis Presenting as a Positive Version: 1 Date: 23 January 2011 Reviewer: Kelvin To Reviewer's report: This is a retrospective study comparing the antimicrobial susceptibility in patients with acute pyelonephritis with or without chronic renal failure. The authors have made a reasonable comparison between the two groups of patients. However, there are some major issues that need to be resolved. I. Major compulsory revisions # General comments 1. It is unclear why the authors initiated this study. They need to explain in the introduction whether there is any theoretical basis suggesting why there may be 2

a difference between the two groups. In general, CRF patients are known to be vulnerable to infection due to weakened immunity. As with diabetes mellitus, CRF has long been considered a predisposing factor for APN, but (reference page 3, 2 nd paragraph) 2. The authors have not addressed some important confounders e.g. recent hospitalization (van der Starre WE et al. J Antimicrob Chemother. 2010 Dec 1. PMID: 21123286), association with healthcare (Rodríguez-Baño J, et al. Clin Infect Dis. 2010 Jan 1;50(1):40-8.) In a recent case-control study, recent hospitalization and fluoroquinolone use in the previous six months were independent risk factors for fluoroquinolone resistance in community-onset febrile E. coli UTI. In our study, we excluded cases of previous administration of antibiotics and hospital-acquired APN. (reference page 11, 1 st paragraph) # Discrepancies in data 3. In the text, it stated that there were 502 patients. However, in table 1, it stated that there were 503 patients. In Table 1, the number of patients was changed to 502. 4. In table 3, 100% of E. coli were sensitive to imipenem. However, both table 5 showed that only 95.5% of E. coli were sensitive to imipenem for the >=60ml/min/1.73m2 group, and in table 7, only 95.7% of the E. coli were sensitive to imipenem in the non-dm group. In Table 3, 96.9% of E. coli samples were sensitive to imipenem. # Methods 5. Page 4. One of the exclusion criteria was previous administration of antibiotics. However, the authors did not define what previous means. For example, would they exclude patients who have taken antibiotics before the collection of urine during the same episode only, or would they exclude patients 3

who have taken antibiotics any time during the prior 6 months? Previous administration of antibiotics refers to administration of antibiotics in the previous six months. (reference page 4, 3 th paragraph) 6. How did the author define hospital-acquired APN? These were defined as infections acquired during hospital care, which were not present or incubating at the time of admission. Infections occurring more than 48 hours after admission are usually considered nosocomial. (reference page 4, 3 th paragraph) # Discussion 7. Page 11.The authors have proposed CRF as a risk factor for APN. However, this was based on the comparison of HS-CRP, WBC and ESR values in APN patients with or without CRF. The only conclusion that can be drawn from these results is that patients with CRF had higher values of inflammatory markers when they have pyeloneprhitis. It does not support the concluionconclusion that CRF is a risk factor for APN 1) Deleted sentence: CRF is a risk factor for APN. 2) Inserted sentence: Patients with CRF had higher values of inflammatory markers when they had APN. (reference page 11, 2 nd paragraph) II. Minor essential revisions 1. Page 11, 2nd paragraph. culture was misspelt. This word was corrected. 2. Page 11, 2nd paragraph. The fourth limitation stated by the authors was that the role of etiology and antimicrobial resistance of uropathogens in patients with APN has not been clarified. However, this is exactly what this study is trying to 4

find out. Therefore, it should not be considered as a limitation. This sentence was deleted. 3. Page 11. The author stated that Based on our results, ampicillin, cephalothin, and gentamycin should not b considered as an initial therapeutic regimen in CRF patients with community-acquired APN. However, the resistance rates in non-crf patients were also very high. Therefore, these antibiotics should not be considered in initial therapy for BOTH CRF and non-crf patients. The phase both CRF and non-crf patients was added. 4. Table 1 is not necessary. The necessary demographic and laboratory information has already been described in table 4. Thank you for your comment. Since we want to show the patient demographic and laboratory information in their entirety, we believe Table 1 is necessary 5. Some of the blood test values are probably not necessary eg. cholesterol, triglycerides, direct bilirubin. By including these results, we hope to explain differences in parameters (e.g., cholesterol, etc.) between CRF and non-crf patients. III. Discretionary revisions 1. For E. coli, how many were ESBL producers? There were 31 (6.2%) ESBL producers. 5

<Reviewer 2> Reviewer's report Title: The Influence of Chronic Renal Failure on the Spectrum and Antimicrobial Susceptibility of Uropathogens in Community-Acquired Acute Pyelonephritis Presenting as a Positive Version: 1 Date: 24 January 2011 Reviewer: katsumi shigemura Reviewer's report: This study describes how CRF affects antimicrobial susceptibilities of uropathogens in community acquired acute pyelonephritis (APN). This included an important factor from the viewpoint of infection, but there needs to be rivised in some parts. I. Major comments # Materials and methods 1. Author had better show at least one or more papers for the definition of CRF used in this study. We cited a paper for the definition of CRF used in this study: Johnson CA, Levey AS, Coresh J, Levin A, Lau J, Eknoyan G: Clinical practice guidelines for chronic kidney disease in adults: Part I. Definition, disease stages, evaluation, treatment, and risk factors. Am Fam Physician 2004, 70:869-76. (reference page 5, 3 rd paragraph) 2. Are the patients enrolloed in the study consecutive? or in specially selected? The patients enrolled in the study were consecutive. 3. Did not all the patients take antibiotics when the urine culture was tested? It is better to make this matter cleared. Patients who had received antibiotics in the previous six months were excluded from the study: The exclusion criteria were as follows: 1) age less than 18 years; 2) history of chronic infection; 3) evidence of other infection; 4) previous administration (in 6

the previous six months) of antibiotics (reference page 4) # Results 4. The authors concluded age, WBC, ESR, and CRP are statistically different in non-crf group and CRF group. Reviewer worry if the severity of AP itself is different or not in these 2 groups. Please comment. In general, CRF patients are known to be vulnerable to infection due to weakened immunity. Therefore, we expected the values of HS-CRP, WBC, and ESR to be higher in the CRF group than they were in the non-crf group. We mentioned that the limitations of our study include that the CRF group was older than the non-crf group. 5. Authod decribe DM but there seems no correlation of infection with DM in this study. Please comment why authors include the investigation of DM. In this study, we aim to show that DM per se does not seem to influence the isolation rates of different uropathogens or their susceptibility patterns to antimicrobials and to clarify the role of CRF in the etiology and antimicrobial resistance of uropathogens in patients with APN. (reference page 9) # Discussion p10 1st paragraph; Authors describe how CRF affects microorganisms but they do not. Please comment from this results with other literatutes. We could not find other literature about the effect of CRF on APN microorganisms. P10 2nd paragraph(in a previous,,,) Authors mention the susceptibilities of ampicillin and gentamicin with the presence of CRF but they shoed low sensitivity to these antibiotics. Do they have a meaning? Please comment. 7

Few data are available on the role of CRF as a risk factor for the development of antimicrobial resistance in uropathogens. Therefore, we aim to show that the antimicrobial sensitivities to other antibiotics did not differ between CRF and non-crf patients P11 1st paragraph( Recent cohort,,,) Authors mentioned the relationship between markers (CRP, ESR, and WBC) and CRF. Howeer, reviewer worry if the backgrounds of infection are different in the 2 groups of CRF and non-crf groups as mentioned above. Please comment. In general, CRF patients are known to be vulnerable to infection due to weakened immunity. Therefore, we expected the values of HS-CRP, WBC, and ESR to be higher in the CRF group than they were in the non-crf group. We mentioned in the limitations of our study that the CRF group was older than the non-crf group. P11 3rd paragraph (Based on our,,) Authors concluded ampicillin, cepharotin, and gentamicin were nor recommended in CRF patients but they do not seem as in non-crf, too. Please give conclusion from another statements. Based on our results, ampicillin, cephalothin, and gentamycin should not be considered as an initial therapeutic regimen in either CRF or non-crf patients with community-acquired APN # Tables Table1.and 4 Reviewer does not feel all the information shown here need to demonstrate. Because we want to show patient demographic and laboratory information, we believe that Tables 1 and 4 are necessary. Table 7 Reviewer does not feel table 7 and the description of DM are necessary in this paper. This may cause confusion for the main topic and purpose of this study. 8

DM has long been considered a predisposing factor for APN, and it has been reported that DM per se does not seem to influence the isolation rates of different uropathogens or their susceptibility patterns to antimicrobials. Although the possibility of confusion regarding the main topic of this study exists, we want to show that the antimicrobial susceptibilities of microorganisms isolated in cases of APN in the non-dm and DM groups were not different. 9