Update on the Mechanisms of Antibiotic Resistance and the Mobile Resistome in the Emerging Zoonotic Pathogen Streptococcus suis

Abstract

Streptococcus suis is a zoonotic pathogen causing important economic losses in swine production. The most commonly used antibiotics in swine industry are tetracyclines, beta-lactams, and macrolides. Resistance to these antibiotics has already been observed worldwide (reaching high rates for macrolides and tetracyclines) as well as resistance to aminoglycosides, fluoroquinolones, amphenicols, and glycopeptides. Most of the resistance mechanisms are encoded by antibiotic resistance genes, and a large part are carried by mobile genetic elements (MGEs) that can be transferred through horizontal gene transfer. This review provides an update of the resistance genes, their combination in multidrug isolates, and their localization on MGEs in S. suis. It also includes an overview of the contribution of biofilm to antimicrobial resistance in this bacterial species. The identification of resistance genes and study of their localization in S. suis as well as the environmental factors that can modulate their dissemination appear essential in order to decipher the role of this bacterium as a reservoir of antibiotic genes for other species.

Non-Penicillin-Susceptible Streptococcus suis Isolated from Humans

“…This gene could contribute to lincosamide and streptogamin B resistance due to the detected clindamycin resistance in S. suis isolates. However, 14.3% of S. suis in our study did not harbor ermB, mef (A/E), or msrD genes, suggesting that, similarly to what has been reported in a previous study [12], other mechanisms such as 23S rRNA methyl transferase (cfr) or macrolide phosphotransferase (mph(C)) are responsible for the macrolide-resistant phenotype displayed by the isolates analyzed here [22].…”

“…Worldwide antimicrobial resistance data available for S. suis indicate that most isolates recovered from both humans and pigs have high resistance to tetracycline and moderate to high resistance to macrolides, e.g., erythromycin [ 12 , 13 , 14 , 15 , 16 , 17 , 19 , 22 ]. Our study confirms those observations.…”

“…Genes tet (B), tet (L), tet (M), tet (O), tet (S), tet (W), tet (40), tet (O/32/O), and tet (O/W/32/O) have been reported [ 12 , 14 , 17 , 19 , 27 , 28 ]. Of these tet genes, tet (O), encoding the ribosome protection protein, is the most frequently described gene in S. suis isolates from pigs and humans worldwide [ 12 , 14 , 17 , 18 , 22 , 27 , 28 ]. In agreement with these previous findings, the tet (O) gene was the predominant tet gene among our isolates.…”

“…In agreement with these previous findings, the tet (O) gene was the predominant tet gene among our isolates. Resistance to macrolides is mainly due to the action of erythromycin ribosomal methylases encoded by erm genes or to macrolide efflux pumps encoded by mef genes [ 22 ]. In this study, ermB (85.7%) was the most frequently detected macrolide gene, replicating previous findings in S. suis isolates recovered from both pigs and humans [ 14 , 17 , 18 , 22 , 23 , 27 , 28 ].…”

“…Resistance to macrolides is mainly due to the action of erythromycin ribosomal methylases encoded by erm genes or to macrolide efflux pumps encoded by mef genes [ 22 ]. In this study, ermB (85.7%) was the most frequently detected macrolide gene, replicating previous findings in S. suis isolates recovered from both pigs and humans [ 14 , 17 , 18 , 22 , 23 , 27 , 28 ]. This gene could contribute to lincosamide and streptogamin B resistance due to the detected clindamycin resistance in S. suis isolates.…”