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The time-kill (TK) assay is considered the gold standard method for the evaluation of in vitro synergy, but it is a time-consuming and expensive method.<\/jats:p>\n                    <jats:p>\n                      The purpose of this study was to evaluate two methods for testing in vitro antimicrobial combinations: the disk diffusion method through disk approximation (DA) and the agar gradient diffusion method via the MIC:MIC ratio. The TK assay was included as the gold standard. MDR Gram-negative clinical isolates (\n                      <jats:italic>n<\/jats:italic>\n                      \u00a0=\u200962; 28\n                      <jats:italic>Pseudomonas aeruginosa<\/jats:italic>\n                      , 20\n                      <jats:italic>Acinetobacter baumannii<\/jats:italic>\n                      , and 14\u2009\n                      <jats:italic>Serratia marcescens<\/jats:italic>\n                      ) were submitted to TK, DA, and MIC:MIC ratio synergy methods.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>\n                      Overall, the agreement between the DA and TK assays ranged from 20 to 93%. The isolates of\n                      <jats:italic>A. baumannii<\/jats:italic>\n                      showed variable results of synergism according to TK, and the calculated agreement was statistically significant in this species against fosfomycin with meropenem including colistin-resistant isolates. The MIC:MIC ratiometric agreed from 35 to 71% with TK assays. The kappa test showed good agreement for the combination of colistin with amikacin (K\u2009=\u20090.58;\n                      <jats:italic>P<\/jats:italic>\n                      \u00a0=\u20090.04) among the colistin-resistant\n                      <jats:italic>A. baumannii<\/jats:italic>\n                      isolates.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>The DA and MIC:MIC ratiometric methods are easier to perform and might be a more viable tool for clinical microbiology laboratories.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.1186\/s12866-020-01756-0","type":"journal-article","created":{"date-parts":[[2020,4,16]],"date-time":"2020-04-16T01:03:00Z","timestamp":1586998980000},"update-policy":"https:\/\/doi.org\/10.1007\/springer_crossmark_policy","source":"Crossref","is-referenced-by-count":34,"title":["Comparison of methods for the detection of in vitro synergy in multidrug-resistant gram-negative bacteria"],"prefix":"10.1186","volume":"20","author":[{"given":"Juliana Januario","family":"Gaudereto","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Lauro Vieira Perdig\u00e3o","family":"Neto","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Gleice Cristina","family":"Leite","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Evelyn Patricia Sanchez","family":"Espinoza","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Roberta Cristina Ruedas","family":"Martins","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Gladys","family":"Villas Boa Prado","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Flavia","family":"Rossi","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Thais","family":"Guimar\u00e3es","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Anna Sara","family":"Levin","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Silvia Figueiredo","family":"Costa","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"297","published-online":{"date-parts":[[2020,4,16]]},"reference":[{"key":"1756_CR1","doi-asserted-by":"publisher","first-page":"S50","DOI":"10.1016\/j.ijantimicag.2010.11.014","volume":"36S","author":"H Giamarellou","year":"2010","unstructured":"Giamarellou H. 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