Cumulative survival profiling: a new PAP-based method for detecting heteroresistance in staphylococcal clinical isolates

The area under the population analysis profile (PAP) is used in the gold standard method for detecting heteroresistance in staphylococci. We tested the hypothesis that the initial inoculum strongly influences the area under the population analysis profile. We sought to interpret this dependence and develop a new metric that lacks this dependence to retrospectively detect heteroresistance to vancomycin in coagulase-negative staphylococcal (CoNS) isolates. We tested our hypothesis on 20 PAPs from the heteroresistant positive control isolate (Mu3) and 7 PAPs from one CoNS isolate which is associated with poor clinical response. The area under the PAP depended linearly (p<0.001) on the initial inoculum. We interpreted the slope to be the cumulative survival under vancomycine concentration gradient. The statistical distribution of the cumulative survival for Mu3 and the CoNS isolate constituted the cumulative survival profiles for each. The profiles reflect ed spectrum of response under vancomycine gradient with the left-tail of CoNS isolate profile located near the median of Mu3 profile indicating the heteroresistance of the CoNS isolate and that the most resistant in the spectrum are likely to be associated with poor clinical response. We estimated that about two-third of the CoNS from unique participants are heteroresistant with 80% of heteroresistant isolates may be associated with a poor clinical response. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement EM receives funding from ALSAC. JWR is supported by 1U01AI124302 and 1RO1AI110618. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The study was approved by our institution review board (XPD16-036) All necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes data is available on the link below