J Lellouche1, D Schwartz2, N Elmalech2, M A Ben Dalak2, E Temkin2, M Paul3, Y Geffen4, D Yahav5, N Eliakim-Raz6, E Durante-Mangoni7, D Iossa7, M Bernardo7, G L Daikos8, A Skiada8, A Pantazatou9, A Antoniadou10, J W Mouton11, Y Carmeli12. 1. Molecular Epidemiology Laboratory, Tel-Aviv Sourasky Medical Center, Tel-Aviv, Israel; National Laboratory for Antibiotic Resistance and Investigation of Outbreaks in Medical Institutions, National Institute for Antibiotic Resistance and Infection Control, Ministry of Health, Israel. Electronic address: jonathanl@tlvmc.gov.il. 2. Molecular Epidemiology Laboratory, Tel-Aviv Sourasky Medical Center, Tel-Aviv, Israel; National Laboratory for Antibiotic Resistance and Investigation of Outbreaks in Medical Institutions, National Institute for Antibiotic Resistance and Infection Control, Ministry of Health, Israel. 3. Institute of Infectious Diseases, Rambam Health Care Campus, Israel; Faculty of Medicine, Technion, Israel Institute of Technology, Haifa, Israel. 4. Clinical Microbiology Laboratory, Rambam Health Care Campus, Haifa, Israel. 5. Unit of Infectious Diseases, Rabin Medical Center, Beilinson Hospital, Petah Tikva, Israel; Sackler Faculty of Medicine, Tel Aviv University, Ramat-Aviv, Israel. 6. Unit of Infectious Diseases, Rabin Medical Center, Beilinson Hospital, Petah Tikva, Israel; Sackler Faculty of Medicine, Tel Aviv University, Ramat-Aviv, Israel; Department of Medicine E, Rabin Medical Center, Beilinson Hospital, Petah Tikva, Israel. 7. Department of Precision Medicine, University of Campania 'L Vanvitelli' and AORN dei Colli-Monaldi Hospital, Napoli, Italy. 8. First Department of Medicine, Laikon General Hospital, Greece; National and Kapodistrian University of Athens, Athens, Greece. 9. National and Kapodistrian University of Athens, Athens, Greece; Clinical Microbiology Laboratory, Laikon General Hospital, Greece. 10. National and Kapodistrian University of Athens, Athens, Greece; Fourth Department of Medicine, Attikon University General Hospital, Athens, Greece. 11. Department of Medical Microbiology and Infectious Diseases, Erasmus MC, Rotterdam, the Netherlands. 12. Molecular Epidemiology Laboratory, Tel-Aviv Sourasky Medical Center, Tel-Aviv, Israel; National Laboratory for Antibiotic Resistance and Investigation of Outbreaks in Medical Institutions, National Institute for Antibiotic Resistance and Infection Control, Ministry of Health, Israel; Sackler Faculty of Medicine, Tel Aviv University, Ramat-Aviv, Israel.
Abstract
OBJECTIVES: The rise in carbapenem resistance among Gram-negative bacteria has renewed interest in colistin. Recently, the EUCAST-CLSI Polymyxin Breakpoints Working Group declared that broth microdilution (BMD) is the only valid method for colistin susceptibility testing. BMD is not easily incorporated into the routine work of clinical laboratories, and usually this test is incorporated serially, resulting in delayed susceptibility reporting. We tested a strategy of combining VITEK® 2 with a 2 μg/mL colistin agar dilution (VITEK® 2/AD) screening plate to improve performance and time to reporting of colistin susceptibility. METHODS: Colistin susceptibility for 364 clinical isolates was determined by VITEK® 2/AD and compared with the reference standard BMD according to the ISO 20776-1:2007 and CLSI guidelines. The EUCAST colistin susceptibility breakpoint of ≤2 μg/mL was used. Escherichia coli NCTC 13846 served as quality control strain. Agreement, very major error (VME) and major error rates were determined using ISO 20776-2:2007. RESULTS: The VME rate for VITEK® 2 alone was 30.6% (15/49, 95% CI 18.3-45.4%), and was reduced to 10.2% (5/49, 95% CI 3.4-22.2%) using the VITEK® 2/AD combined testing. The combined testing had categorical agreement with BMD of 97% (354/364, 95% CI 95.0-98.7%), and a major error (ME) rate of 1.6% (5/315, 95% CI 0.5-3.7%). Using the combined testing, even against challenging strains, 349 (95.8%, 95% CI 93.3-97.7%) colistin susceptibility results could be reported, and only 15 isolates required further analysis by BMD. DISCUSSION: Our method is simple to apply and allows rapid reporting of colistin susceptibility.
OBJECTIVES: The rise in carbapenem resistance among Gram-negative bacteria has renewed interest in colistin. Recently, the EUCAST-CLSI Polymyxin Breakpoints Working Group declared that broth microdilution (BMD) is the only valid method for colistin susceptibility testing. BMD is not easily incorporated into the routine work of clinical laboratories, and usually this test is incorporated serially, resulting in delayed susceptibility reporting. We tested a strategy of combining VITEK® 2 with a 2 μg/mL colistin agar dilution (VITEK® 2/AD) screening plate to improve performance and time to reporting of colistin susceptibility. METHODS: Colistin susceptibility for 364 clinical isolates was determined by VITEK® 2/AD and compared with the reference standard BMD according to the ISO 20776-1:2007 and CLSI guidelines. The EUCAST colistin susceptibility breakpoint of ≤2 μg/mL was used. Escherichia coli NCTC 13846 served as quality control strain. Agreement, very major error (VME) and major error rates were determined using ISO 20776-2:2007. RESULTS: The VME rate for VITEK® 2 alone was 30.6% (15/49, 95% CI 18.3-45.4%), and was reduced to 10.2% (5/49, 95% CI 3.4-22.2%) using the VITEK® 2/AD combined testing. The combined testing had categorical agreement with BMD of 97% (354/364, 95% CI 95.0-98.7%), and a major error (ME) rate of 1.6% (5/315, 95% CI 0.5-3.7%). Using the combined testing, even against challenging strains, 349 (95.8%, 95% CI 93.3-97.7%) colistin susceptibility results could be reported, and only 15 isolates required further analysis by BMD. DISCUSSION: Our method is simple to apply and allows rapid reporting of colistin susceptibility.
Authors: Carlos Bastidas-Caldes; Jacobus H de Waard; María Soledad Salgado; María José Villacís; Marco Coral-Almeida; Yoshimasa Yamamoto; Manuel Calvopiña Journal: Pathogens Date: 2022-06-08