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Trends, Epidemiology, and Management of Multi-Drug Resistant Gram-Negative Bacterial Infections in the Hospitalized Setting
Article

Increased Azithromycin Susceptibility of Multidrug-Resistant Gram-Negative Bacteria on RPMI-1640 Agar Assessed by Disk Diffusion Testing

1
Department of Infectious Diseases and Hospital Epidemiology, University of Zurich, 8091 Zurich, Switzerland
2
Pharmacologie cellulaire et moléculaire, Louvain Drug Research Institute, Université catholique de Louvain, B-1200 Brussels, Belgium
3
Institute of Medical Microbiology, University of Zurich, 8091 Zurich, Switzerland
*
Author to whom correspondence should be addressed.
These authors contributed equally to this work.
Current address: Michael Hombach, Roche Diagnostics International AG, 6343 Rotkreuz, Switzerland.
Received: 20 March 2020 / Revised: 22 April 2020 / Accepted: 26 April 2020 / Published: 29 April 2020
(This article belongs to the Special Issue Antimicrobial Resistance in Gram-Negative Bacteria, 2nd Edition)
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’ 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–Hinton and RPMI-1640 media. Azithromycin susceptibility of Enterobacteriaceae and a subgroup of P. aeruginosa increased significantly on RPMI-1640 agar compared to Mueller–Hinton agar. Further, a significant correlation (Kendall, τ, p) of zone diameters and minimal inhibitory concentrations (MICs) was found on RPMI-1640 agar for E. coli (−0.4279, 0.0051), E. cloacae (−0.3783, 0.0237) and P. aeruginosa (−0.6477, <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. View Full-Text
Keywords: azithromycin; Gram-negative; Pseudomonas aeruginosa; Enterobacteriaceae; susceptibility testing; MIC; disk diffusion; multidrug-resistant azithromycin; Gram-negative; Pseudomonas aeruginosa; Enterobacteriaceae; susceptibility testing; MIC; disk diffusion; multidrug-resistant
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MDPI and ACS Style

Meerwein, M.; Tarnutzer, A.; Böni, M.; Van Bambeke, F.; Hombach, M.; Zinkernagel, A.S. Increased Azithromycin Susceptibility of Multidrug-Resistant Gram-Negative Bacteria on RPMI-1640 Agar Assessed by Disk Diffusion Testing. Antibiotics 2020, 9, 218. https://0-doi-org.brum.beds.ac.uk/10.3390/antibiotics9050218

AMA Style

Meerwein M, Tarnutzer A, Böni M, Van Bambeke F, Hombach M, Zinkernagel AS. Increased Azithromycin Susceptibility of Multidrug-Resistant Gram-Negative Bacteria on RPMI-1640 Agar Assessed by Disk Diffusion Testing. Antibiotics. 2020; 9(5):218. https://0-doi-org.brum.beds.ac.uk/10.3390/antibiotics9050218

Chicago/Turabian Style

Meerwein, Milton; Tarnutzer, Andrea; Böni, Michelle; Van Bambeke, Françoise; Hombach, Michael; Zinkernagel, Annelies S. 2020. "Increased Azithromycin Susceptibility of Multidrug-Resistant Gram-Negative Bacteria on RPMI-1640 Agar Assessed by Disk Diffusion Testing" Antibiotics 9, no. 5: 218. https://0-doi-org.brum.beds.ac.uk/10.3390/antibiotics9050218

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