Session Type: 1-hour Oral Session
Session Title: 1-hour Oral Session
Authors(s): B. Tack (1, 2), L. Hardy (1), M.F. Phoba (3, 4), L. Mbuyi-Kalonji (3, 4), P. Thong (5), P. Lompo (6), L. Kuijpers (7), B. Barbé (1), O. Vandenberg (8, 9, 10), J. Ruiz (11), O. Lunguya (12, 4), J. Jacobs (1, 2)
Authors Affiliations(s): (1) Department of Clinical Sciences, Institute of Tropical Medicine, Belgium, (2) Department of Microbiology and Immunology, KU Leuven, Belgium, (3) Department of Clinical Sciences, Institute of Tropical Medicine, Congo, the Democratic Republic of the, (4) Department of Microbiology, University Teaching Hospital of Kinshasa, Congo, the Democratic Republic of the, (5) Sihanouk Hospital Center of Hope, Cambodia, (6) IRSS/Clinical Research Unit of Nanoro (CRUN), Burkina Faso, (7) Department of Internal Medicine, Netherlands, (8) Center for Environmental Health and Occupational Health, School of Public Health, Université Libre de Bruxelles (ULB), Belgium, (9) Innovation and Business Development Unit, Laboratoire Hospitalier Universitaire de Bruxelles - Universitair Laboratorium Brussel (LHUB-ULB), Belgium, (10) Division of Infection and Immunity, Faculty of Medical Sciences, University College London, United Kingdom, (11) Laboratory of Molecular Microbiology and Bacterial Genomics, Universidad Cientifica del Sur, Peru, (12) Department of Microbiology, National Institute for Biomedical Research, Congo, the Democratic Republic of the
Background:
Non-typhi Salmonella (NTS) cause multidrug resistant invasive infections in low- and middle income countries. Azithromycin is a promising alternative for oral treatment. However, comparative data on azithromycin susceptibility testing (AST) methods and ECOFF for NTS are missing.
Methods:We selected 359 invasive NTS isolated between 2007 and 2017: 312 from DR Congo including 181 azithromycin resistant Salmonella Typhimurium and 47 from Cambodia including 17 azithromycin resistant Salmonella Choleraesuis. We performed AST by agar dilution (reference method), semi-automated broth microdilution (customized Sensititre panel, ThermoFisher), gradient tests (bioMérieux, Liofilchem, HiMedia) and disk diffusion (Rosco, Oxoid, BD, Liofilchem) according to EUCAST. Readings were done by two independent readers. Gradient tests were read at 80% (according to manufacturers’ instructions) and 100% inhibition (MIC80, MIC100). In addition, we determined azithromycin MIC distribution (MIC80 E-test bioMérieux) and ECOFF of 2127 invasive NTS from DR Congo, Burkina Faso, Rwanda and Cambodia (1984 – 2017) using EUCAST ECOFFinder 2.0.
Results:Categorical agreement versus agar dilution was excellent (≥ 98% ) for all methods. Essential agreement was very good for Sensititre (94%) and MIC100 gradient tests (91 – 96%) but moderate for MIC80 gradient tests (57 – 65%) which indicated lower MICs particularly for susceptible NTS (Figure 1, similar data for all products). Interreader agreement was high for agar dilution and Sensititre (both 90% identical, all ≤1 twofold difference) as well as for disk diffusion (≤3mm difference in 96.4 – 99.7%), but lower for gradient tests (MIC80 & MIC100: 36.2 – 53.2% identical, 83.0 – 93.9% ≤1 twofold difference). Trailing endpoints were observed in 31.5% and 24.2% of agar dilution and Sensititre tests (Figure 2). The visual and calculated ECOFF for azithromycin MIC of invasive NTS was 16 mg/l (Figure 3).
Conclusions:
Sensititre and disk diffusion were accurate, precise and user-friendly and therefore suitable methods for azithromycin AST in multicenter studies and field settings, respectively. When read at 80% inhibition, gradient tests were difficult to read and moderately accurate and precise; reading at 100% inhibition improved accuracy. The ECOFF of invasive NTS is identical to the ECOFF of Salmonella Typhi (CLSI and EUCAST) and Salmonella enterica (EUCAST).
Keyword(s): Azithromycin susceptibility, non-typhi Salmonella, ECOFFCOI Institutional Grants: Yes
Session Type: 1-hour Oral Session
Session Title: 1-hour Oral Session
Authors(s): B. Tack (1, 2), L. Hardy (1), M.F. Phoba (3, 4), L. Mbuyi-Kalonji (3, 4), P. Thong (5), P. Lompo (6), L. Kuijpers (7), B. Barbé (1), O. Vandenberg (8, 9, 10), J. Ruiz (11), O. Lunguya (12, 4), J. Jacobs (1, 2)
Authors Affiliations(s): (1) Department of Clinical Sciences, Institute of Tropical Medicine, Belgium, (2) Department of Microbiology and Immunology, KU Leuven, Belgium, (3) Department of Clinical Sciences, Institute of Tropical Medicine, Congo, the Democratic Republic of the, (4) Department of Microbiology, University Teaching Hospital of Kinshasa, Congo, the Democratic Republic of the, (5) Sihanouk Hospital Center of Hope, Cambodia, (6) IRSS/Clinical Research Unit of Nanoro (CRUN), Burkina Faso, (7) Department of Internal Medicine, Netherlands, (8) Center for Environmental Health and Occupational Health, School of Public Health, Université Libre de Bruxelles (ULB), Belgium, (9) Innovation and Business Development Unit, Laboratoire Hospitalier Universitaire de Bruxelles - Universitair Laboratorium Brussel (LHUB-ULB), Belgium, (10) Division of Infection and Immunity, Faculty of Medical Sciences, University College London, United Kingdom, (11) Laboratory of Molecular Microbiology and Bacterial Genomics, Universidad Cientifica del Sur, Peru, (12) Department of Microbiology, National Institute for Biomedical Research, Congo, the Democratic Republic of the
Background:
Non-typhi Salmonella (NTS) cause multidrug resistant invasive infections in low- and middle income countries. Azithromycin is a promising alternative for oral treatment. However, comparative data on azithromycin susceptibility testing (AST) methods and ECOFF for NTS are missing.
Methods:We selected 359 invasive NTS isolated between 2007 and 2017: 312 from DR Congo including 181 azithromycin resistant Salmonella Typhimurium and 47 from Cambodia including 17 azithromycin resistant Salmonella Choleraesuis. We performed AST by agar dilution (reference method), semi-automated broth microdilution (customized Sensititre panel, ThermoFisher), gradient tests (bioMérieux, Liofilchem, HiMedia) and disk diffusion (Rosco, Oxoid, BD, Liofilchem) according to EUCAST. Readings were done by two independent readers. Gradient tests were read at 80% (according to manufacturers’ instructions) and 100% inhibition (MIC80, MIC100). In addition, we determined azithromycin MIC distribution (MIC80 E-test bioMérieux) and ECOFF of 2127 invasive NTS from DR Congo, Burkina Faso, Rwanda and Cambodia (1984 – 2017) using EUCAST ECOFFinder 2.0.
Results:Categorical agreement versus agar dilution was excellent (≥ 98% ) for all methods. Essential agreement was very good for Sensititre (94%) and MIC100 gradient tests (91 – 96%) but moderate for MIC80 gradient tests (57 – 65%) which indicated lower MICs particularly for susceptible NTS (Figure 1, similar data for all products). Interreader agreement was high for agar dilution and Sensititre (both 90% identical, all ≤1 twofold difference) as well as for disk diffusion (≤3mm difference in 96.4 – 99.7%), but lower for gradient tests (MIC80 & MIC100: 36.2 – 53.2% identical, 83.0 – 93.9% ≤1 twofold difference). Trailing endpoints were observed in 31.5% and 24.2% of agar dilution and Sensititre tests (Figure 2). The visual and calculated ECOFF for azithromycin MIC of invasive NTS was 16 mg/l (Figure 3).
Conclusions:
Sensititre and disk diffusion were accurate, precise and user-friendly and therefore suitable methods for azithromycin AST in multicenter studies and field settings, respectively. When read at 80% inhibition, gradient tests were difficult to read and moderately accurate and precise; reading at 100% inhibition improved accuracy. The ECOFF of invasive NTS is identical to the ECOFF of Salmonella Typhi (CLSI and EUCAST) and Salmonella enterica (EUCAST).
Keyword(s): Azithromycin susceptibility, non-typhi Salmonella, ECOFFCOI Institutional Grants: Yes