Trends of Antimicrobial Susceptibility in Clinically Significant Coagulase-Negative Staphylococci Isolated from Cerebrospinal Fluid Cultures in Neurosurgical Adults: a Nine-Year Analysis

ABSTRACT Coagulase-negative staphylococci (CoNS) are the main pathogens in health care-associated ventriculitis and meningitis (HCAVM). This study aimed to assess antimicrobial susceptibility. Moreover, the treatment and clinical outcome were described. All neurosurgical adults admitted to one of the largest neurosurgical centers in China with clinically significant CoNS isolated from cerebrospinal fluid cultures in 2012 to 2020 were recruited. One episode was defined as one patient with one bacterial strain. Interpretive categories were applied according to the MICs. The clinical outcomes were dichotomized into poor (Glasgow Outcome Scale 1 to 3) and acceptable (Glasgow Outcome Scale 4 to 5). In total, 534 episodes involving 519 patients and 16 bacteria were analyzed. Over the 9 years, eight antimicrobial agents were used in antimicrobial susceptibility tests, including six in over 80% of CoNS. The range of resistance rates was 0.8% to 84.6%. The vancomycin resistance rate was the lowest, whereas the penicillin resistance rate was the highest. The linezolid (a vancomycin replacement) resistance rate was 3.1%. The rate of oxacillin resistance, representing methicillin-resistant staphylococci, was 70.2%. There were no significant trends of antimicrobial susceptibility over the 9 years for any agents analyzed. However, there were some apparent changes. Notably, vancomycin-resistant CoNS appeared in recent years, while linezolid-resistant CoNS appeared early and disappeared in recent years. Vancomycin (or norvancomycin), the most common treatment agent, was used in 528 (98.9%) episodes. Finally, 527 (98.7%) episodes had acceptable outcomes. It will be safe to use vancomycin to treat CoNS-related HCAVM in the immediate future, although continuous monitoring will be needed. IMPORTANCE Coagulase-negative staphylococci are the main pathogens in health care-associated ventriculitis and meningitis. There are three conclusions from the results of this study. First, according to antimicrobial susceptibility, the rates of resistance to primary antimicrobial agents are high and those to high-level agents, including vancomycin, are low. Second, the trends of resistance rates are acceptable, especially for high-level agents, although long-term and continuous monitoring is necessary. Finally, the clinical outcomes of neurosurgical adults with coagulase-negative staphylococci-related health care-associated ventriculitis and meningitis are acceptable after treatment with vancomycin. Therefore, according to the antimicrobial susceptibility and clinical practice, vancomycin will be safe to treat coagulase-negative staphylococci-related health care-associated ventriculitis and meningitis.

Reviewer #2 (Comments for the Author): This work by Ye et al. aims to investigate the trends of antimicrobial susceptibility in clinically significant coagulase-negative staphylococci (CoNS) isolated from cerebrospinal fluid (CSF) cultures in a Chinese hospital over a period of 9 years. The authors have concluded that no significant trend of antimicrobial susceptibility was observed in CoNS against the antimicrobials analysed in the study over the period of 9 years. However, the authors have also noted some visible changes, such as the increasing of vancomycin resistance and the 'disappearing' of lizezolid resistance. Although the study informs the overall situation of antimicrobial resistance in clinical CoNS in the Chinese hospital, much is needed to improve the methodology and data presentation in this manuscript in order to support these conclusions.
Major comments: 1. Most of the recruited 2342 patients were excluded (leaving one 519 patients). What is the rationale behind the patient exclusion criteria? For instance, if the authors were to investigate the antimicrobial susceptibility in clinically significant CoNS, why cultures from patients under 18 were excluded? 2. What is a contaminated episode? Figure 1 shows 1344 cultures were positive with CoNS amongst 1116 episodes, if I understand correctly. Then it shows 582 episodes were excluded because of contamination. Could the authors clarify why CoNS positive cultures later considered as contaminations? 3. The authors need to detail the method/methods used for sample collection and bacteria isolation from CSF. The authors also need to provide information on how bacterial speciation was performed and verified. 4. In line 79-82, the authors described that the antimicrobial susceptibility testing (AST) was performed according to CLSI standard and a National Standards. Are both standards the same and what are the differences if not? More importantly, the presentation of the AST data in the manuscript should be improved. Figure 3 is not very informative since one can not easily tell the resistance rate in a specific CoNS species in a specific year. A table providing detailed percentages may be better. 5. It seems that the authors have access to the large amount of patient metadata, but not much analysis was carried out using these data in relation to the antimicrobial resistance in CoNS. It seems to be a missed opportunity. 6. The manuscript needs extensive revision for language and grammar.
Minor comments: 1. The "Trends of antimicrobial susceptibility tests" should change to "Trends of antimicrobial susceptibility", given that the work is investigating antimicrobial susceptibility, not the testing methods. (throughout the manuscript). 2. Line 83: "the breakpoints" should be "the range" 3. Line 97: Why only the first positive culture was analysed in an episode? Are the isolates from in subsequent positive culture the same with the first? 4. Line 107, the authors state that "after exclusion, 534 episodes from 519 patients were analysed"; in Line 111, the authors state 526 (98.5%) survived. This is confusing since the number of patients do not match. 5. A more detailed and clear legend is needed for each figure. 6. Table 3 needs to be improved. a) The table title is not proper. b) Presumably that the numbers in the year columns indicate the number of CoNS tested each year, could the author clarify in the note and add the resistant rate in each separate year?
Editor comment: I would have a native-English speaker proof read manuscript to improve readability.

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In the study of M.M. Yi Ye et al. the retrospective analysis of dynamic antibiotic susceptibility of clinical isolates of coagulase-negative staphylococci (CoNS) isolated from the patients with neurological infections was performed. In order to differentiate the contaminated samples and true infections inclusion criteria were applied. Since the work is exclusively retrospective and the authors used the results of lab information systems only, no experimental studies were carried out. I've got the feeling that the manuscript is more like a report than a research study. Perhaps the work should be supplemented with some clinical data -a detailed description of clinical outcomes, its associations with different species of CoNS, as well as some additional clinical parameters for a proper comparison. Which treatment have the patients received? Was there any correlation with the antibiotic susceptibility data? What was the time period during the treatment after which the cerebrospinal fluid was free of CoNS?
Minor comments: English should be revised.
Which method was used for CoNS identification?
Versions of CLSI, EUCAST should be specified.  Differently, in this manuscript, the clinical outcome was judged after the hospitalization in which the patient had healthcare-associated ventriculitis and meningitis because the treatment was described.

Minor comments: A more detailed and clear legend is needed for each figure.
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