María Díez-Aguilar1, María-Isabel Morosini1, Lorena López-Cerero2, Álvaro Pascual2, Jorge Calvo3, Luis Martínez-Martínez4, Francesc Marco5, Jordi Vila5, Adriana Ortega6, Jesús Oteo6, Rafael Cantón7. 1. Servicio de Microbiología, Hospital Universitario Ramón y Cajal and Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS), Madrid, Spain Red Española de Investigación en Patología Infecciosa (REIPI) Instituto de Salud Carlos III, Madrid, Spain. 2. Red Española de Investigación en Patología Infecciosa (REIPI) Instituto de Salud Carlos III, Madrid, Spain Servicio de Microbiología, Hospital Universitario Virgen Macarena and Departamento de Microbiología, Universidad de Sevilla, Sevilla, Spain. 3. Red Española de Investigación en Patología Infecciosa (REIPI) Instituto de Salud Carlos III, Madrid, Spain Servicio de Microbiología, Hospital Universitario Marqués de Valdecilla-IDIVAL, Santander, Spain. 4. Red Española de Investigación en Patología Infecciosa (REIPI) Instituto de Salud Carlos III, Madrid, Spain Servicio de Microbiología, Hospital Universitario Marqués de Valdecilla-IDIVAL, Santander, Spain Departamento de Biología Molecular, Universidad de Cantabria, Santander, Spain. 5. Red Española de Investigación en Patología Infecciosa (REIPI) Instituto de Salud Carlos III, Madrid, Spain Servicio de Microbiología Clínica, Hospital Clínic, Facultad de Medicina and Centro de Investigación en Salud Internacional de Barcelona (CRESIB), Barcelona, Spain. 6. Red Española de Investigación en Patología Infecciosa (REIPI) Instituto de Salud Carlos III, Madrid, Spain Laboratorio de Antibióticos, Bacteriología, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, Madrid, Spain. 7. Servicio de Microbiología, Hospital Universitario Ramón y Cajal and Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS), Madrid, Spain Red Española de Investigación en Patología Infecciosa (REIPI) Instituto de Salud Carlos III, Madrid, Spain rafael.canton@salud.madrid.org.
Abstract
OBJECTIVES: There are different methodological recommendations for in vitro testing of the co-amoxiclav combination. Performance of co-amoxiclav MIC testing for Escherichia coli by the standard ISO microdilution method (ISO 20776-1) was compared using EUCAST (fixed 2 mg/L clavulanate concentration) and CLSI (2 : 1 ratio) interpretive criteria. METHODS: MICs were determined by broth microdilution using a 2 : 1 ratio and fixed clavulanate concentrations (2 and 4 mg/L) for 160 clinical E. coli isolates with characterized resistance mechanisms. Essential agreements, categorical agreements and relative errors were determined. RESULTS: For all isolates, essential agreement between microdilution using 2 mg/L clavulanate and a 2 : 1 ratio was 25.6%. For ESBL-producing isolates, considering EUCAST breakpoints, 55% of isolates tested with 2 mg/L clavulanate were classified as resistant; conversely, 95% of isolates tested with 4 mg/L clavulanate were susceptible. When using CLSI breakpoints and a 2 : 1 ratio, 90% of isolates were susceptible and 10% were intermediate. CONCLUSIONS: Variation in the clavulanate concentration gave different susceptibility testing results, particularly among ESBL-producing E. coli isolates. The in vitro concentration of clavulanate that better correlates with clinical outcome is still under debate and should be established.
OBJECTIVES: There are different methodological recommendations for in vitro testing of the co-amoxiclav combination. Performance of co-amoxiclav MIC testing for Escherichia coli by the standard ISO microdilution method (ISO 20776-1) was compared using EUCAST (fixed 2 mg/L clavulanate concentration) and CLSI (2 : 1 ratio) interpretive criteria. METHODS: MICs were determined by broth microdilution using a 2 : 1 ratio and fixed clavulanate concentrations (2 and 4 mg/L) for 160 clinical E. coli isolates with characterized resistance mechanisms. Essential agreements, categorical agreements and relative errors were determined. RESULTS: For all isolates, essential agreement between microdilution using 2 mg/L clavulanate and a 2 : 1 ratio was 25.6%. For ESBL-producing isolates, considering EUCAST breakpoints, 55% of isolates tested with 2 mg/L clavulanate were classified as resistant; conversely, 95% of isolates tested with 4 mg/L clavulanate were susceptible. When using CLSI breakpoints and a 2 : 1 ratio, 90% of isolates were susceptible and 10% were intermediate. CONCLUSIONS: Variation in the clavulanate concentration gave different susceptibility testing results, particularly among ESBL-producing E. coli isolates. The in vitro concentration of clavulanate that better correlates with clinical outcome is still under debate and should be established.
Authors: Karina-Doris Vihta; Nicole Stoesser; Martin J Llewelyn; T Phuong Quan; Tim Davies; Nicola J Fawcett; Laura Dunn; Katie Jeffery; Chris C Butler; Gail Hayward; Monique Andersson; Marcus Morgan; Sarah Oakley; Amy Mason; Susan Hopkins; David H Wyllie; Derrick W Crook; Mark H Wilcox; Alan P Johnson; Tim E A Peto; A Sarah Walker Journal: Lancet Infect Dis Date: 2018-08-17 Impact factor: 25.071
Authors: Timothy J Davies; Nicole Stoesser; Anna E Sheppard; Manal Abuoun; Philip Fowler; Jeremy Swann; T Phuong Quan; David Griffiths; Alison Vaughan; Marcus Morgan; Hang T T Phan; Katie J Jeffery; Monique Andersson; Matt J Ellington; Oskar Ekelund; Neil Woodford; Amy J Mathers; Robert A Bonomo; Derrick W Crook; Tim E A Peto; Muna F Anjum; A Sarah Walker Journal: Antimicrob Agents Chemother Date: 2020-05-21 Impact factor: 5.191