TY - JOUR
T1 - Establishing breakpoints for amoxicillin/clavulanate and ampicillin/sulbactam for rapid antimicrobial susceptibility testing directly from positive blood culture bottles
AU - König, Elisabeth
AU - Iser, Juliane
AU - Zechner-Sammer, Tanja
AU - Friedl, Herwig
AU - Krause, Robert
AU - Valentin, Thomas
AU - Leitner, Eva
AU - Zollner-Schwetz, Ines
PY - 2023
Y1 - 2023
N2 - Introduction. In 2018, EUCAST released guidelines on rapid antimicrobial susceptibility testing (RAST) directly from positive blood culture bottles for selected bacterial species and antimicrobial agents, but not for the commonly used agents amoxicillin/ clavulanate (AMC) and ampicillin/sulbactam (SAM). Hypothesis/Gap statement. This work addresses the Enterobacterales RAST capability gap for betalactam/betalactamase inhibitor combinations. Aim. We aimed to determine RAST breakpoints for AMC and SAM for Escherichia coli and Klebsiella pneumoniae after 4 and 6 h of incubation directly from positive blood cultures. Methodology. Blood culture bottles were spiked with clinical isolates of E. coli (n=89) and K. pneumoniae (n=81). RAST was performed according to EUCAST guidelines and zones were read after 4 and 6 h. Breakpoints were defined to avoid very major errors. Results. The proportion of readable zone diameters after 4 h of incubation were 90.8% in E. coli and 85.8% in K. pneumoniae isolates. After 6 h of incubation all zone diameters could be read. The proposed breakpoints for E. coli after 6 h of incubation were ≥16 mm S (susceptible), 14–15 mm ATU (area of technical uncertainty) and <14 mm R (resistant) for AMC; ≥15 mm S, 12–14 mm ATU and <12 mm R for SAM; for K. pneumoniae these were ≥16 mm S, 14–15 mm ATU and <14 mm R for AMC; ≥13 mm S, 12 mm ATU, <12 mm R for SAM. Applying our newly set breakpoints, major errors were infrequent (2.6%). Conclusion. We propose novel AMC and SAM breakpoints for RAST directly from positive blood cultures for reading after 4 and 6 h of incubation.
AB - Introduction. In 2018, EUCAST released guidelines on rapid antimicrobial susceptibility testing (RAST) directly from positive blood culture bottles for selected bacterial species and antimicrobial agents, but not for the commonly used agents amoxicillin/ clavulanate (AMC) and ampicillin/sulbactam (SAM). Hypothesis/Gap statement. This work addresses the Enterobacterales RAST capability gap for betalactam/betalactamase inhibitor combinations. Aim. We aimed to determine RAST breakpoints for AMC and SAM for Escherichia coli and Klebsiella pneumoniae after 4 and 6 h of incubation directly from positive blood cultures. Methodology. Blood culture bottles were spiked with clinical isolates of E. coli (n=89) and K. pneumoniae (n=81). RAST was performed according to EUCAST guidelines and zones were read after 4 and 6 h. Breakpoints were defined to avoid very major errors. Results. The proportion of readable zone diameters after 4 h of incubation were 90.8% in E. coli and 85.8% in K. pneumoniae isolates. After 6 h of incubation all zone diameters could be read. The proposed breakpoints for E. coli after 6 h of incubation were ≥16 mm S (susceptible), 14–15 mm ATU (area of technical uncertainty) and <14 mm R (resistant) for AMC; ≥15 mm S, 12–14 mm ATU and <12 mm R for SAM; for K. pneumoniae these were ≥16 mm S, 14–15 mm ATU and <14 mm R for AMC; ≥13 mm S, 12 mm ATU, <12 mm R for SAM. Applying our newly set breakpoints, major errors were infrequent (2.6%). Conclusion. We propose novel AMC and SAM breakpoints for RAST directly from positive blood cultures for reading after 4 and 6 h of incubation.
KW - betalactam/betalactamase inhibitor combinations
KW - blood cultures
KW - bloodstream infection
KW - rapid antimicrobial susceptibility testing
UR - http://www.scopus.com/inward/record.url?scp=85151042878&partnerID=8YFLogxK
U2 - 10.1099/jmm.0.001672
DO - 10.1099/jmm.0.001672
M3 - Article
SN - 0022-2615
VL - 72
JO - Journal of Medical Microbiology
JF - Journal of Medical Microbiology
IS - 3
M1 - 001672
ER -