Impact of amoxicillin therapy on resistance selection in patients with community-acquired lower respiratory tract infections: a randomized, placebo-controlled study

Malhotra-Kumar, S, Van Heirstraeten, L, Coenen, S, Lammens, C, Adriaenssens, N, Kowalczyk, A, Godycki-Cwirko, M, Bielicka, Z, Hupkova, H, Lannering, C, Mölstad, S, Fernandez-Vandellos, P, Torres, A, Parizel, M, Ieven, M, Butler, Christopher C. ORCID: https://orcid.org/0000-0002-0102-3453, Verheij, T, Little, P and Goossens, H 2016. Impact of amoxicillin therapy on resistance selection in patients with community-acquired lower respiratory tract infections: a randomized, placebo-controlled study. Journal of Antimicrobial Chemotherapy 71 (11) , pp. 3258-3267. 10.1093/jac/dkw234

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Abstract

Objectives To determine the effect of amoxicillin treatment on resistance selection in patients with community-acquired lower respiratory tract infections in a randomized, placebo-controlled trial. Methods Patients were prescribed amoxicillin 1 g, three times daily (n = 52) or placebo (n = 50) for 7 days. Oropharyngeal swabs obtained before, within 48 h post-treatment and at 28–35 days were assessed for proportions of amoxicillin-resistant (ARS; amoxicillin MIC ≥2 mg/L) and -non-susceptible (ANS; MIC ≥0.5 mg/L) streptococci. Alterations in amoxicillin MICs and in penicillin-binding-proteins were also investigated. ITT and PP analyses were conducted. Results ARS and ANS proportions increased 11- and 2.5-fold, respectively, within 48 h post-amoxicillin treatment compared with placebo [ARS mean increase (MI) 9.46, 95% CI 5.57–13.35; ANS MI 39.87, 95% CI 30.96–48.78; P < 0.0001 for both]. However, these differences were no longer significant at days 28–35 (ARS MI −3.06, 95% CI −7.34 to 1.21; ANS MI 4.91, 95% CI −4.79 to 14.62; P > 0.1588). ARS/ANS were grouped by pbp mutations. Group 1 strains exhibited significantly lower amoxicillin resistance (mean MIC 2.8 mg/L, 95% CI 2.6–3.1) than group 2 (mean MIC 9.3 mg/L, 95% CI 8.1–10.5; P < 0.0001). Group 2 strains predominated immediately post-treatment (61.07%) and although decreased by days 28–35 (30.71%), proportions remained higher than baseline (18.70%; P = 0.0004). Conclusions By utilizing oropharyngeal streptococci as model organisms this study provides the first prospective, experimental evidence that resistance selection in patients receiving amoxicillin is modest and short-lived, probably due to ‘fitness costs’ engendered by high-level resistance-conferring mutations. This evidence further supports European guidelines that recommend amoxicillin when an antibiotic is indicated for community-acquired lower respiratory tract infections.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Schools > Medicine
Publisher:	Oxford University Press
ISSN:	0305-7453
Date of Acceptance:	16 May 2016
Last Modified:	02 Nov 2022 11:22
URI:	https://orca.cardiff.ac.uk/id/eprint/101783

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