Samenvatting

Background
Toxigenic C. diphteriae and C. Ulcerans are the agents of diphtheria. Although diphtheria cases are rare in Europe, an increase has been reported in 2022. 363 diphtheria cases were notified from which approximately one third in people with recent migration history. Furthermore, in 2023 119 cases of diphtheria have in reported so far in the EU/EEA [1]. In Belgium, 25 cases of toxigenic C. diphtheria infection were confirmed among asylum seekers in 2022 [2] and seven in 2023 to date. As antibiotics are important for treatment and prophylaxis, we aimed to evaluate three AST techniques.

Materials and methods
We selected 71 isolates of toxigenic C. diphteriae (n = 35) and C. ulcerans (n = 36), isolated in Belgium. Broth microdilution (BMD) was compared with antimicrobial gradient (Etest®, Biomérieux) and disk diffusion (DD). Interpretation was done according to EUCAST [3]. DD and BMD were compared to Etest® in order to investigate its clinical application as an alternative method for BMD.

Results
Table 1 and 2 present results for C. diphteriae (table 1) and C. ulcerans (table 2). When comparing all methods, we found that these correlate well. Small discordances were found resulting in minor error of classification. Three isolates were resistant to erythromycin of which one resistant to penicillin. Only one C. diphtheriae was found to be multidrug resistant. Overall, Etest® estimates the MIC of the antibiotics 0.5 – 1 dilutions higher or lower than BMD, except for tetracycline where values are overestimated by a median of 1.5 dilutions.

Conclusion
Etest® has the tendency to over –or underestimate MIC in comparison to BMD, especially for tetracycline. However, as BMD is labor intensive and more expensive, Etest® could be used as a more rapid and cost-effective way to evaluate antimicrobial susceptibilities. Some C. diphtheriae isolates were resistant to penicillin and macrolides, which are known as the primary choice of treatment. Moreover, C. diphteriae isolates are more resistant than C. ulcerans. For future research, we aim to evaluate the genomic resistance of these isolates and correlate these resistance genes to the found AST pattern.


References
(1) ECDC, surveillance atlas of infectious diseases, 2023.
(2) Jacquinet S, et al. Outbreak of Corynebacterium diphtheriae among asylum seekers in Belgium in 2022: operational challenges and lessons learnt. Euro Surveill. 2023;28(44):pii=2300130. https://doi.org/10.2807/1560-7917.ES.2023.28.44.2300130
(3) The European Committee on Antimicrobial Susceptibility Testing. Breakpoint tables for interpretation of MICs and zone diameters. Version 13.1, 2023. http://www.eucast.org
Originele taal-2English
StatusPublished - 2024
Evenement34th European congress of clinical microbiology and infectious diseases - Barcelona, Spain
Duur: 27 apr 202430 apr 2024
https://www.eccmid.org/congress-information

Conference

Conference34th European congress of clinical microbiology and infectious diseases
Land/RegioSpain
StadBarcelona
Periode27/04/2430/04/24
Internet adres

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