{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,18]],"date-time":"2026-08-18T04:32:26Z","timestamp":1787027546349,"version":"build-2736575974"},"reference-count":32,"publisher":"MDPI AG","issue":"5","license":[{"start":{"date-parts":[[2020,4,29]],"date-time":"2020-04-29T00:00:00Z","timestamp":1588118400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001711","name":"Schweizerischer Nationalfonds zur F\u00f6rderung der Wissenschaftlichen Forschung","doi-asserted-by":"publisher","award":["310030_146295\/1"],"award-info":[{"award-number":["310030_146295\/1"]}],"id":[{"id":"10.13039\/501100001711","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Antibiotics"],"abstract":"<jats:p>Increasing antibiotic resistances and a lack of new antibiotics render the treatment of Gram-negative bacterial infections increasingly difficult. Therefore, additional approaches are being investigated. Macrolides are not routinely used against Gram-negative bacteria due to lack of evidence of in vitro effectiveness. However, it has been shown that Pseudomonas spp. are susceptible to macrolides in liquid RPMI-1640 and clinical data suggest improvement in patients\u2019 outcomes. So far, these findings have been hardly applicable to the clinical setting due to lack of routine low-complexity antimicrobial susceptibility testing (AST) for macrolides. We therefore optimized and compared broth microdilution and disk diffusion AST. Multidrug-resistant Gram-negative bacteria (Escherichia coli, Enterobacter cloacae, Klebsiella pneumoniae, Pseudomonas aeruginosa) were tested for azithromycin susceptibility by disk diffusion and broth microdilution in Mueller\u2013Hinton and RPMI-1640 media. Azithromycin susceptibility of Enterobacteriaceae and a subgroup of P. aeruginosa increased significantly on RPMI-1640 agar compared to Mueller\u2013Hinton agar. Further, a significant correlation (Kendall, \u03c4, p) of zone diameters and minimal inhibitory concentrations (MICs) was found on RPMI-1640 agar for E. coli (\u22120.4279, 0.0051), E. cloacae (\u22120.3783, 0.0237) and P. aeruginosa (\u22120.6477, &lt;0.0001). Performing routine disk diffusion AST on RPMI-1640 agar may lead to the identification of additional therapeutic possibilities for multidrug-resistant bacterial infections in the routine clinical diagnostic setting.<\/jats:p>","DOI":"10.3390\/antibiotics9050218","type":"journal-article","created":{"date-parts":[[2020,4,29]],"date-time":"2020-04-29T13:23:45Z","timestamp":1588166625000},"page":"218","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":31,"title":["Increased Azithromycin Susceptibility of Multidrug-Resistant Gram-Negative Bacteria on RPMI-1640 Agar Assessed by Disk Diffusion Testing"],"prefix":"10.3390","volume":"9","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-8167-192X","authenticated-orcid":false,"given":"Milton","family":"Meerwein","sequence":"first","affiliation":[{"name":"Department of Infectious Diseases and Hospital Epidemiology, University of Zurich, 8091 Zurich, Switzerland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Andrea","family":"Tarnutzer","sequence":"additional","affiliation":[{"name":"Department of Infectious Diseases and Hospital Epidemiology, University of Zurich, 8091 Zurich, Switzerland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Michelle","family":"B\u00f6ni","sequence":"additional","affiliation":[{"name":"Department of Infectious Diseases and Hospital Epidemiology, University of Zurich, 8091 Zurich, Switzerland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0052-7991","authenticated-orcid":false,"given":"Fran\u00e7oise","family":"Van Bambeke","sequence":"additional","affiliation":[{"name":"Pharmacologie cellulaire et mol\u00e9culaire, Louvain Drug Research Institute, Universit\u00e9 catholique de Louvain, B-1200 Brussels, Belgium"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Michael","family":"Hombach","sequence":"additional","affiliation":[{"name":"Institute of Medical Microbiology, University of Zurich, 8091 Zurich, Switzerland"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Annelies S.","family":"Zinkernagel","sequence":"additional","affiliation":[{"name":"Department of Infectious Diseases and Hospital Epidemiology, University of Zurich, 8091 Zurich, Switzerland"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2020,4,29]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"363","DOI":"10.7326\/M16-0291","article-title":"Progress in the Fight against Multidrug-Resistant Bacteria? 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