Streptococcus suis outbreak caused by an emerging zoonotic strain with acquired multi-drug resistance in Thailand

Abstract

Streptococcus suis is an emerging zoonotic swine pathogen which can cause severe infections in humans. In March 2021, an outbreak of S. suis infections with 19 confirmed cases of septicemia and meningitis leading to two deaths, occurred in Nakhon Ratchasima province, Thailand. We characterized the outbreak through an epidemiological investigation combined with Illumina and Nanopore whole genome sequencing (WGS). The source of the outbreak was traced back to a raw pork dish prepared from a single pig during a Buddhist ceremony attended by 241 people. WGS analysis revealed that a single S. suis serotype 2 strain belonging to a novel sequence type (ST) of the emergent Thai zoonotic clade CC233/379, was responsible for the infections. The outbreak clone grouped together with other Thai zoonotic strains from CC233/379 and CC104 in a global S. suis phylogeny and capsule switching events between serotype 2 zoonotic strains and serotype 7 porcine strains were identified. The outbreak strain showed reduced susceptibility to penicillin corresponding with mutations in key residues in the penicillin binding proteins (PBPs). Furthermore, the outbreak strain was resistant to tetracycline, erythromycin, clindamycin, linezolid and chloramphenicol, having acquired an integrative and conjugative element (ICE) carrying resistance genes tetO and ermB, as well as a transposon from the IS1216 family carrying optrA and ermA. This investigation demonstrates that multi-drug resistant zoonotic lineages of S. suis which pose a threat to human health continue to emerge.

Virulence genes, resistome and mobilome of Streptococcus suis strains isolated in France

“…S6). Most of them (except Ala460Val, Thr491Ser and Arg514Asp/Gly) have already been described previously in penicillin-resistant isolates of S. suis [45, 63–65]. Two modifications (Met144Ile/Leu/Thr and Val145Ile/Leu) were detected in the glycosyltransferase domain of MraY.…”

Human Streptococcus suis Infections in Thailand: Epidemiology, Clinical Features, Genotypes, and Susceptibility

“…The fourth outbreak was reported in Uttaradit province in May 2019, with 5 confirmed cases and 18 suspected cases [17]. A fifth outbreak occurred for the first time in northeastern Thailand (Nakhon Ratchasima) in 2021, with 21 confirmed cases, including 2 fatal cases [18]. Microbiological analysis of the outbreak S. suis strains showed that the first and second outbreaks were due to serotype 2 with sequence type (ST) 1, while the third outbreak was caused by serotype 2-ST104 and serotype 14-ST105.…”

“…There was no available information about the serotype and STs in the fourth outbreak. The fifth outbreak was caused by serotype 2 with a new ST (ST1656) belonging to the clonal complex (CC) 233/379 [18].…”

“…In total, 1798 cases from 59 reports were identified [6,[8][9][10][11][12][13][14][15][16][17][18][21][22][23][24][25][26]. Most cases were male (n = 1287).…”

“…A recent study investigated an emerging S. suis ST1656 belonging to CC233/379 that caused the fifth outbreak in Thailand carried the MLS B resistance gene ermA and the oxazolidinone and phenicol resistance gene optrA that were found exclusively in the outbreak isolates other than tet(O) and ermB [18].…”