Same zone diameter, different verdict: clinical and surveillance implications of EUCAST 2025 versus CLSI 2025 breakpoint discordance among Enterobacterales, Staphylococcus and Pseudomonas isolates at Buea Regional Hospital, Cameroon
- 1Buea Regional Hospital
Abstract
BackgroundAST guide both patient management and national AMR surveillance. In Cameroon, laboratories interpret AST using either CLSI or EUCAST standard which may not always give the same conclusion for every case. This study compared EUCAST 2025 and CLSI 2025 interpretations of identical disk diffusion results at Buea Regional Hospital (BRH).
MethodsThis was a retrospective laboratory-based study where raw inhibition zone diameters of Enterobacterales, Staphylococcus and Pseudomonas isolates recorded in the BRH WHONET database (2023 - 2025) were interpreted with EUCAST 2025 and CLSI 2025 standards. Agreement was evaluated using Cohens kappa ({kappa}), with {kappa} < 0.61 considered poor agreement. Major interpretation switches (susceptible {leftrightarrow} resistant) were enumerated, and the standard more associated with non-susceptible outcome was identified using the exact McNemar test.
ResultsA total of 1,198 isolates (748 Enterobacterales, 367 Staphylococcus and 83 Pseudomonas) were included in the analysis. Poor agreement was observed for 4/12 (33.3%) antibiotics against Enterobacterales (lowest: ofloxacin, {kappa} = 0.48), 5/10 (50%) against Staphylococcus (lowest: levofloxacin, {kappa} = 0.08) and 5/7 (71.4%) against Pseudomonas (lowest: cefepime and imipenem, {kappa} = 0.24). Major interpretation switches occurred for 3/12 antibiotics (Amox/clavulanic acid [1.1%], ceftriaxone [0.6%] and ofloxacin [15.6%]) against Enterobacterales, 6/10 against Staphylococcus (minocycline [21.1%], gentamicin [15.9%], rifampicin [14.4%], clindamycin [2.7%], tetracycline [4.5%], levofloxacin [13.7%]) and 2/7 among Pseudomonas (cefepime [20%], ciprofloxacin [3%]). Overall, EUCAST was significantly more likely (p < 0.001) to classify isolates as non-susceptible.
ConclusionPoor agreement between EUCAST 2025 and CLSI 2025 affected one third of the antibiotics tested for Enterobacterales, half for Staphylococcus and close to three quarters for Pseudomonas. Major interpretation switches were quite common for levofloxacin, ofloxacin, gentamicin, minocycline, rifampicin and cefepime. EUCAST was generally more likely to classify isolates as non-susceptible. A single national breakpoint standard is recommended in Cameroon so as to optimize the reliability of its surveillance data.
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BibTeX
@misc{tufon2026same,
title = {{Same zone diameter, different verdict: clinical and surveillance implications of EUCAST 2025 versus CLSI 2025 breakpoint discordance among Enterobacterales, Staphylococcus and Pseudomonas isolates at Buea Regional Hospital, Cameroon}},
author = {K. A. Tufon and H. D. Meriki and K. K. Ngong and A. F. Bolimo and Y. S. Kouanou and N. G. Nyenty and B. T. Gertrude and L. B. G. Legrand and B. B. Ewane and F. M. Tutuwan and E. M. Esum},
howpublished = {medRxiv},
year = {2026},
month = oct,
doi = {10.64898/2026.10.20.26366059},
url = {https://www.medrxiv.org/content/10.64898/2026.10.20.26366059v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Same zone diameter, different verdict: clinical and surveillance implications of EUCAST 2025 versus CLSI 2025 breakpoint discordance among Enterobacterales, Staphylococcus and Pseudomonas isolates at Buea Regional Hospital, Cameroon
AU - K. A. Tufon
AU - H. D. Meriki
AU - K. K. Ngong
AU - A. F. Bolimo
AU - Y. S. Kouanou
AU - N. G. Nyenty
AU - B. T. Gertrude
AU - L. B. G. Legrand
AU - B. B. Ewane
AU - F. M. Tutuwan
AU - E. M. Esum
PY - 2026
DA - 2026/10/20
PB - medRxiv
DO - 10.64898/2026.10.20.26366059
UR - https://www.medrxiv.org/content/10.64898/2026.10.20.26366059v1
AB - BackgroundAST guide both patient management and national AMR surveillance. In Cameroon, laboratories interpret AST using either CLSI or EUCAST standard which may not always give the same conclusion for every case. This study compared EUCAST 2025 and CLSI 2025 interpretations of identical disk diffusion results at Buea Regional Hospital (BRH). MethodsThis was a retrospective laboratory-based study where raw inhibition zone diameters of Enterobacterales, Staphylococcus and Pseudomonas isolates recorded in the BRH WHONET database (2023 - 2025) were interpreted with EUCAST 2025 and CLSI 2025 standards. Agreement was evaluated using Cohens kappa ({kappa}), with {kappa} < 0.61 considered poor agreement. Major interpretation switches (susceptible {leftrightarrow} resistant) were enumerated, and the standard more associated with non-susceptible outcome was identified using the exact McNemar test. ResultsA total of 1,198 isolates (748 Enterobacterales, 367 Staphylococcus and 83 Pseudomonas) were included in the analysis. Poor agreement was observed for 4/12 (33.3%) antibiotics against Enterobacterales (lowest: ofloxacin, {kappa} = 0.48), 5/10 (50%) against Staphylococcus (lowest: levofloxacin, {kappa} = 0.08) and 5/7 (71.4%) against Pseudomonas (lowest: cefepime and imipenem, {kappa} = 0.24). Major interpretation switches occurred for 3/12 antibiotics (Amox/clavulanic acid [1.1%], ceftriaxone [0.6%] and ofloxacin [15.6%]) against Enterobacterales, 6/10 against Staphylococcus (minocycline [21.1%], gentamicin [15.9%], rifampicin [14.4%], clindamycin [2.7%], tetracycline [4.5%], levofloxacin [13.7%]) and 2/7 among Pseudomonas (cefepime [20%], ciprofloxacin [3%]). Overall, EUCAST was significantly more likely (p < 0.001) to classify isolates as non-susceptible. ConclusionPoor agreement between EUCAST 2025 and CLSI 2025 affected one third of the antibiotics tested for Enterobacterales, half for Staphylococcus and close to three quarters for Pseudomonas. Major interpretation switches were quite common for levofloxacin, ofloxacin, gentamicin, minocycline, rifampicin and cefepime. EUCAST was generally more likely to classify isolates as non-susceptible. A single national breakpoint standard is recommended in Cameroon so as to optimize the reliability of its surveillance data.
ER -