Macrolide resistance determinants and their associations in streptococci from selected livestock and wildlife species from Catalonia, Northeast Spain

Abstract

The increasing macrolide resistance in Streptococcus spp. causing human and animal infections in the last decades is a concern for global health. The objectives of this study were to analyze the macrolide resistance rates of Streptococcus spp. from animals and their resistance determinants. We conducted a retrospective study of an animal Streptococcus collection (307 isolates) from farm, wild animals, and pets in Catalonia, Northeast Spain. Identification was done by MALDI-TOF, and antimicrobial susceptibility to erythromycin and clindamycin was assessed by disk diffusion (EUCAST). Resistant strains were further tested for susceptibility to other antimicrobial agents using disk diffusion and microdilution methods. Selected isolates (n = 50) were subjected to whole-genome sequencing (WGS). Mobile genetic elements (MGEs), such as integrative and conjugative elements (ICEs) and integrative and mobilizable elements (IMEs), were identified using ICEscreen. Streptococcal strains were mainly isolated from domestic swine (50.5%) and wild boars (19.2%), with S. suis (54.4%) and S. hyovaginalis (14%) the predominant species. The macrolide resistance phenotypes found were MLSB (n = 145), M (n = 6), and L (n = 30). Macrolide (84.5%) and lincosamide (94.8%) resistance rates from swine strains were higher than those from other animals (13.2% and 18.4%, respectively, P < 0.001). The predominant resistant genes found were erm(B) (n = 38), tet(O) (n = 28), vga(F) (n = 20), and lnu(B)-lsa(E) (n = 10), and were mostly associated with ICEs or defective ICEs (dICEs) belonging to the Tn5252 family. Animal streptococci presented high macrolide resistance rates, especially concerning swine strains, associated with a variety of resistance determinants. MGEs were the main carriers of resistance determinants and contributors to its spread.