Genetic diversity and variation in antimicrobial-resistance determinants of non-serotype 2 Streptococcus suis isolates from healthy pigs

Abstract

Streptococcus suis is a leading cause of bacterial meningitis in South-East Asia, with frequent zoonotic transfer to humans associated with close contact with pigs. A small number of invasive lineages are responsible for endemic infection in the swine industry, causing considerable global economic losses. A lack of surveillance and a rising trend in clinical treatment failure has raised concerns of growing antimicrobial resistance (AMR) among invasive S. suis . Gene flow between healthy and disease isolates is poorly understood and, in this study, we sample and sequence a collection of isolates predominantly from healthy pigs in Chiang Mai province, Northern Thailand. Pangenome characterization identified extensive genetic diversity and frequent AMR carriage in isolates from healthy pigs. Multiple AMR genes were identified, conferring resistance to aminoglycosides, lincosamides, tetracycline and macrolides. All isolates were non-susceptible to three or more different antimicrobial classes, and 75 % of non-serotype 2 isolates were non-susceptible to six or more classes (compared to 37.5 % of serotype 2 isolates). AMR genes were found on integrative and conjugative elements previously observed in other species, suggesting a mobile gene pool that can be accessed by invasive disease isolates. This article contains data hosted by Microreact.

Streptococcus suis Research Update: Serotype Prevalence and Antimicrobial Resistance Distribution in Swine Isolates Recovered in Spain from 2020 to 2022

“…Regarding quinolones, the resistance levels obtained were considered intermediate since the AMR values for ENRO and DANO were 49% and 60.9%, respectively. Notably, in all studies encompassing any of these antimicrobials [ 44 , 45 , 47 , 54 , 55 , 56 , 58 ] the resistance levels were considerably lower than those observed in this study. Specifically, the resistances detected were 2%, 9.6%, 1.4%, 11.1%, 2%, 11.5%, and 1%, respectively.…”

“…However, varying levels of resistance have emerged. The resistances detected were 8% [ 56 ] and 66% [ 49 ] for PEN and 19% for AMP [ 58 ]. Moreover, excluding the 66% resistance from the study from 2012 [ 49 ], the remaining AMR levels are recent, as both articles were published in 2022.…”

Colistin resistance and resistance determinants are mobile amongSalmonella entericaisolates from diseased and healthy pigs in Thailand

“…It was therefore interesting to note that healthy pigs also represent a potential reservoir of MDR. This has been noted with other species, with healthy pigs harbouring diverse resistant genotypes of Streptococcus suis (Kittiwan et al, 2022).…”

Commercial farmed swine harbour a variety of pathogenic bacteria and antimicrobial resistance genes

“…Various other groups of antimicrobial resistance genes, such as beta-lactam, lincosamide, macrolide, macrolide-lincosamide-streptogramin B, nucleoside, sulfonamide and trimethoprim resistance genes, were also found across the farms. These findings indicate a strong selective pressure resulting from widespread antimicrobial use and highlight the abundance of antimicrobial resistance organisms in industrially farmed swine [70–72]. Rapid industrialization of agricultural processes has diminished physical barriers to recombination, facilitating the spread of AMR genes between species and gene pools [73], often via the exchange of mobile genetic elements and horizontal gene transfer [74–76].…”