A rare case of Aerococcus urinae native valve endocarditis

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Abstract

Background Aerococcus urinae, was initially considered a commensal of the urinary tract, but there is now increasing evidence for its involvement in urinary tract and systemic infections. A. urinae endocarditis has a high mortality rate and occurs mainly in patients with underlying conditions or presence of extraneous material. Case presentation This report handles the case of a 65 year old male with cardiac antecedents, who was admitted to the cardiology department after a syncope of unknown origin and diagnosed with severe mixed aortic valve disease and mitral valve sclerosis through the means of a transesophageal echocardiography (TEE). During hospitalisation, the patient progressively deteriorated with the development of shortness of breath and an inflammatory syndrome. Urinary laboratory analysis showed an A. urinae infection and blood cultures depicted A. urinae growth. Treatment with piperacillin/tazobactam was started empirically. Repeated TEE showed evidence for endocarditis with vegetation and perforation of the mitral valve that required an emergency surgery with mitral valve repair. After surgery, gentamicin and penicillin G were administered for 48 hours, followed by combined ceftriaxone/penicillin G treatment for 6 weeks. At first, flucloxacillin was also associated as the culture of the valve was negative. Finally, 16S rRNA polymerase chain reaction (PCR) on the valve tissue, confirmed the A. urinae endocarditis. Conclusion A. urinae is an underestimated cause of serious infections such as endocarditis. Urinary tract infections mainly in older men can be an entry point for this type of invasive infection.

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  1. The work presented is clear and the arguments well formed. The reviewers have highlighted minor concerns with the work presented. Please ensure that you address their comments. Please provide more detail in the Methods section and ensure that software is consistently cited and its version and parameters included.

  2. Comments to Author

    The case report "A rare case of Aerococcus urinae native valve endocarditis" by Goes et al. describes a 65-year-old patient with A. urinae endocarditis. The manuscript highlights the potential of A. urinae to cause acute endocarditis. The diagnosis was confirmed by blood cultures and 16S rRNA gene sequencing, and in conjunction with the clinical findings, there is no doubt about an accurate diagnosis. As a small suggestion, I would prefer to present the laboratory results in a table rather than in the text to improve readability. Since the discussion addresses the weaknesses of 16S rRNA gene sequencing, it could also be mentioned how these can be counteracted, for example by combining sequencing with imaging techniques in molecular microbiology, such as in situ hybridization, as recommended in the 2023 Duke ISCVID criteria. Additional minor points: - please give details on the microbiological culture methods and duration, which medium did you use and how long were the cultures incubated? - please give further details on the susceptibility of the cultured strain to the antibiotics administered. - please comment on the readmission of the patient after initial discharge - were cultures again positive for A. urinae? - please rephrase the sentence in line 125 'In the majority of cases, endocarditis is associated with S. aureus…' The top three species causing endocarditis are staphylococci, streptococci and enterococci. Are you referring to native or prosthetic valve endocarditis? Or do you have a reference for this statement? - please cite the 2023 Duke ISCVID criteria and the current ESC Guidelines as current gold standard for diagnosis and treatment of endocarditis (line 155). - please correct the term 16S rRNA gene PCR (it's the gene that is amplified). Could you please give more details on the 16S rRNA gene PCR and sequencing used? Was the entire gene amplified or just part of it? - please capitalize the word Gram. - Please rephrase ll. 140-142 - negative culture results of heart valves are often due to previous antibiotic treatment - for Aerococcus treatment, a combination of penicillin plus an aminoglycoside is recommended (u.a. Hirzel C, Hirzberger L, Furrer H, Endimiani A. Bactericidal activity of penicillin, ceftriaxone, gentamicin and daptomycin alone and in combination against Aerococcus urinae. International Journal of Antimicrobial Agents. 2016; 48(3):271-6. https://doi.org/10.1016/j.ijantimicag.2016.05.007 PMID: 27451085), please comment why therapy with Pip/Tazo was continued for three days after blood cultures were positive with Aerococcus and then switched to amoxicillin alone, if I understood correctly? Overall, I would recommend publishing this manuscript. The case report is convincing due to its detailed presentation of the clinical case and a discussion that summarizes the important points. Figures and images were used very well. Since A. urinae endocarditis is diagnosed relatively rarely, this article can help to make doctors physicians aware of the possibility and relevance of this pathogen in infective endocarditis.

    Please rate the quality of the presentation and structure of the manuscript

    Good

    To what extent are the conclusions supported by the data?

    Strongly support

    Do you have any concerns of possible image manipulation, plagiarism or any other unethical practices?

    No

    Is there a potential financial or other conflict of interest between yourself and the author(s)?

    No

    If this manuscript involves human and/or animal work, have the subjects been treated in an ethical manner and the authors complied with the appropriate guidelines?

    Yes

  3. Comments to Author

    This manuscript describes a case of Aerococcus urinae infective endocarditis (IE) Comments 1. Abstract, "has a high mortality rate" is not really true. The mortality rate is relatively low compared to IE caused by other pathogens if you look at case series (see for example https://pubmed.ncbi.nlm.nih.gov/26119199/). 2. Abstract "Urinary laboratory analysis showed an A. urinae infection", a urinary tract infection is a clinical diagnosis. Finding of bacteruria is not enough. Rephrase. 3. Introduction is too short, the bacterium should be presented along with the most common clinical manifestations. 4. Line 80, "The same A. urinae reappeared in his blood cultures", no way of determining if it the same clone. Please rephrase. 5. Line 100, addition of ceftriaxone to benzyl-Pc must be based on a misconception. There is no proof of synergistic effects between these agents on A. urinae. This needs to be commented upon so that others do not think that this should be done! 6. Line 112, what happened after that? Was there evidence of relapse? Valve cultures? Antibiotic treatment? 7. Line 137, biofilm formation and platelet aggregation was shown first by Shannon et al (https://pubmed.ncbi.nlm.nih.gov/20696834/). 8. Line 154, "As discussed earlier, 16S rRNA PCR can detect bacterial DNA even after complete antibiotic treatment which poses a risk of generating false-positive results.". I do not agree, such a case is not false positive. You need to explain that such a patient does not necessarily has an on-going IE.. 9. Line 159, "Infective endocarditis with A. urinae has a poor prognosis with high mortality [17].". I do not agree. Refer to case series instead (see for example https://pubmed.ncbi.nlm.nih.gov/26119199/). See also https://pubmed.ncbi.nlm.nih.gov/31170831/ for a discussion on this matter.

    Please rate the quality of the presentation and structure of the manuscript

    Satisfactory

    To what extent are the conclusions supported by the data?

    Partially support

    Do you have any concerns of possible image manipulation, plagiarism or any other unethical practices?

    No

    Is there a potential financial or other conflict of interest between yourself and the author(s)?

    No

    If this manuscript involves human and/or animal work, have the subjects been treated in an ethical manner and the authors complied with the appropriate guidelines?

    Yes