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2020-07-01

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Si us plau utilitzeu sempre aquest identificador per citar o enllaçar aquest document: https://hdl.handle.net/2445/183494

Assessment of trimethoprim-sulfamethoxazole susceptibility testing methods for fastidious Haemophilus spp.

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Recurs relacionat

https://doi.org/10.1016/j.cmi.2019.11.022

Resum

Objectives: To compare the determinants of trimethoprim-sulfamethoxazole resistance with established susceptibility values for fastidious Haemophilus spp., to provide recommendations for optimal trimethoprim-sulfamethoxazole measurement. Methods: We collected 50 strains each of Haemophilus influenzae and Haemophilus parainfluenzae at Bellvitge University Hospital. Trimethoprim-sulfamethoxazole susceptibility was tested by microdilution, E-test and disc diffusion using both Mueller-Hinton fastidious (MH-F) medium and Haemophilus test medium (HTM) following EUCAST and CLSI criteria, respectively. Mutations in folA, folP and additional determinants of resistance were identified in whole-genome-sequenced isolates. Results: Strains presented generally higher rates of trimethoprim-sulfamethoxazole resistance when grown on HTM than on MH-F, independent of the methodology used (average MIC 2.6-fold higher in H. influenzae and 1.2-fold higher in H. parainfluenzae). The main resistance-related determinants were as follows: I95L and F154S/V in folA; 3- and 15-bp insertions and substitutions in folP; acquisition of sul genes; and FolA overproduction potentially linked to mutations in -35 and -10 promoter motifs. Of note, 2 of 19 H. influenzae strains (10.5%) and 9 of 33 H. parainfluenzae strains (27.3%) with mutations and assigned as resistant by microdilution were inaccurately considered susceptible by disc diffusion. This misinterpretation was resolved by raising the clinical resistance breakpoint of the EUCAST guidelines to ≤30 mm. Conclusions: Given the routine use of disc diffusion, a significant number of strains could potentially be miscategorized as susceptible to trimethoprim-sulfamethoxazole despite having resistance-related mutations. A simple modification to the current clinical resistance breakpoint given by the EUCAST guideline for MH-F ensures correct interpretation and correlation with the reference standard method of microdilution.

Matèries

Malalties bacterianes, Antibiòtics, Estabilitat dels medicaments, Bacils

Matèries (anglès)

Bacterial diseases, Antibiotics, Drug stability, Bacillus (Bacteria)

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Col·leccions

Articles publicats en revistes (Patologia i Terapèutica Experimental)
Articles publicats en revistes (Institut d'lnvestigació Biomèdica de Bellvitge (IDIBELL))

Citació

SIERRA URUEÑA, Yanik, et al. Assessment of trimethoprim-sulfamethoxazole susceptibility testing methods for fastidious Haemophilus spp. Clinical Microbiology and Infection. 2020. Vol. 26, num. 7. ISSN 1198-743X. [consulted: 19 of August of 2026]. Available at: https://hdl.handle.net/2445/183494

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