Loren Dejoies1,2, Sarrah Boukthir1, Gauthier Péan de Ponfilly3, Ronan Le Guen4, Asma Zouari1,5, Sophie Potrel1,5, Anaïs Collet1,5, Gabriel Auger1,5, Hervé Jacquier3, Vincent Fihman4,6, Laurent Dortet7, Vincent Cattoir1,2,5. 1. CHU de Rennes, Service de Bactériologie et Hygiène Hospitalière, Rennes, France. 2. U1230 'ARN régulateurs Bactériens et Médecine', Université Rennes 1, Rennes, France. 3. Hôpital Lariboisière, Service de Bactériologie-Virologie, Paris, France. 4. Hôpitaux Universitaires Henri Mondor, Unité de Bactériologie-Hygiène, Créteil, France. 5. CNR de la Résistance aux Antibiotiques (laboratoire associé 'Entérocoques'), Rennes, France. 6. EA 7380 Dynamyc, EnvA, UPEC, Paris-Est University, Créteil, France. 7. CHU de Bicêtre, service de Bactériologie-Hygiène, Le Kremlin-Bicêtre, France.
Abstract
BACKGROUND: Linezolid-resistant enterococci (LRE) causing infections that are challenging to treat are rising, highlighting the need for reliable screening of LRE clinical isolates. OBJECTIVES: To evaluate the ability of the broth microdilution (BMD) method for LRE detection and to assess the performance of seven commercially available techniques for linezolid susceptibility testing. METHODS: A collection of 100 clinical isolates (80 Enterococcus faecium and 20 Enterococcus faecalis), including 20 optrA-positive isolates, 17 poxtA-positive isolates and 1 optrA/poxtA-positive E. faecium isolate, were studied. MICs were determined after 18 h [Day 1 (D1)] and 42 h [Day 2 (D2)] of incubation and interpreted following EUCAST and CLSI guidelines, which currently provide different interpretative breakpoints. Performance of commercial techniques was compared with BMD results. RESULTS: MIC50/D1 and MIC50/D2 were both 8 mg/L, while MIC90/D1 and MIC90/D2 were 16 and 32 mg/L, respectively. MICD1 values for poxtA-positive isolates were lower than those for optrA-positive isolates. Proportions of susceptible isolates at D1 and D2 were 48% and 41%, respectively, according to EUCAST breakpoints and 35% and 13%, respectively, according to CLSI criteria (the proportions of isolates categorized as intermediate following CLSI recommendations were 13% and 28% at D1 and D2, respectively). Percentage susceptibility assessed by the commercially available techniques was always higher. The four commercial methods allowing MIC determination provided an overall essential agreement of ≥90% at D1. Categorical agreement and error rates were generally improved at D2. CONCLUSIONS: Non-automated methods (Sensititre and UMIC) and, to a lesser extent, gradient strip Etest appear to show an acceptable correlation with the BMD reference method for the detection of isolates with low MICs of linezolid after prolonged incubation.
BACKGROUND:Linezolid-resistant enterococci (LRE) causing infections that are challenging to treat are rising, highlighting the need for reliable screening of LRE clinical isolates. OBJECTIVES: To evaluate the ability of the broth microdilution (BMD) method for LRE detection and to assess the performance of seven commercially available techniques for linezolid susceptibility testing. METHODS: A collection of 100 clinical isolates (80 Enterococcus faecium and 20 Enterococcus faecalis), including 20 optrA-positive isolates, 17 poxtA-positive isolates and 1 optrA/poxtA-positive E. faecium isolate, were studied. MICs were determined after 18 h [Day 1 (D1)] and 42 h [Day 2 (D2)] of incubation and interpreted following EUCAST and CLSI guidelines, which currently provide different interpretative breakpoints. Performance of commercial techniques was compared with BMD results. RESULTS: MIC50/D1 and MIC50/D2 were both 8 mg/L, while MIC90/D1 and MIC90/D2 were 16 and 32 mg/L, respectively. MICD1 values for poxtA-positive isolates were lower than those for optrA-positive isolates. Proportions of susceptible isolates at D1 and D2 were 48% and 41%, respectively, according to EUCAST breakpoints and 35% and 13%, respectively, according to CLSI criteria (the proportions of isolates categorized as intermediate following CLSI recommendations were 13% and 28% at D1 and D2, respectively). Percentage susceptibility assessed by the commercially available techniques was always higher. The four commercial methods allowing MIC determination provided an overall essential agreement of ≥90% at D1. Categorical agreement and error rates were generally improved at D2. CONCLUSIONS: Non-automated methods (Sensititre and UMIC) and, to a lesser extent, gradient strip Etest appear to show an acceptable correlation with the BMD reference method for the detection of isolates with low MICs of linezolid after prolonged incubation.
Authors: Ayesha Khan; William R Miller; Dierdre Axell-House; Jose M Munita; Cesar A Arias Journal: J Clin Microbiol Date: 2022-06-13 Impact factor: 11.677
Authors: Michaël Timmermans; Bert Bogaerts; Kevin Vanneste; Sigrid C J De Keersmaecker; Nancy H C Roosens; Carole Kowalewicz; Guillaume Simon; Maria A Argudín; Ariane Deplano; Marie Hallin; Pierre Wattiau; David Fretin; Olivier Denis; Cécile Boland Journal: J Antimicrob Chemother Date: 2021-12-24 Impact factor: 5.790
Authors: Stefan Schwarz; Wanjiang Zhang; Xiang-Dang Du; Henrike Krüger; Andrea T Feßler; Shizhen Ma; Yao Zhu; Congming Wu; Jianzhong Shen; Yang Wang Journal: Clin Microbiol Rev Date: 2021-06-02 Impact factor: 50.129