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PubMed1978

The type-specific polysaccharides of Streptococcus suis.

Streptococcus suis types 1 and 2 were subjected to digestion with lysozyme. Serologically type-specific capsular polysaccharides were isolated from the lysates by ethanol precipitation followed by Sepharose 6B chromatography. The purified type 1 polysaccharide has a Kd value of 0.074 on a Sepharose 4B column and contains galactose, glucose, N-acetyl glucosamine, N-acetyl galactosamine, and sialic acid in a molar ratio of 2.42:1.00:1.00:1.13:1.39. The type 2 polysaccharide has a Kd value of 0.185 and is composed of rhamnose, galactose, glucose, N-acetyl glucosamine, and sialic acid in a molar ratio of 1.07:3.17:1.00:0.94:1.00. A comparison is drawn between the type polysaccharides of S. suis and those of group B streptococci.

Carbohydrates↗
PubMed2026

Molecular epidemiology and antimicrobial resistance of human Streptococcus suis isolates in Guangxi, China, 2015-2021.

BACKGROUND: Streptococcus suis (S. suis) is an important zoonotic pathogen and a common colonizer of the upper respiratory tract of pigs. Human infections have been reported in several regions of China, including Guangxi, but genomic and antimicrobial resistance data from this region remain limited. This study investigated the molecular epidemiology, antimicrobial susceptibility, and genomic characteristics of human S. suis isolates collected in Baise City, Guangxi, from 2015 to 2021. METHODS: This retrospective study included 39 non-duplicate clinical isolates confirmed as S. suis by whole-genome analysis. Antimicrobial susceptibility testing was performed using a broth microdilution-based system and interpreted according to the Clinical and Laboratory Standards Institute guidelines. Serotypes were determined by agglutination using type-specific antisera. Whole-genome sequencing was used for species confirmation, multilocus sequence typing, detection of antimicrobial resistance and virulence-associated genes, and core-protein phylogenetic analysis. RESULTS: The median patient age was 55 years, and 36/39 (92.3%) patients were male. Meningitis was documented in 34/39 (87.2%) patients, and hearing impairment occurred in 21/39 (53.8%). Pig- or pork-related exposure was recorded in 15/39 (38.5%) patients. Resistance was highest to tetracycline (38/39, 97.4%), followed by erythromycin and clindamycin (26/39, 66.7% each). Four isolates (10.3%) showed intermediate susceptibility to penicillin, but none were resistant. All isolates remained susceptible to ampicillin, ceftriaxone, levofloxacin, linezolid, vancomycin, and meropenem. Serotype 2 predominated (32/39, 82.1%), followed by serotype 14 (7/39, 17.9%), while ST1 (29/39, 74.4%) and ST7 (7/39, 17.9%) were the two major sequence types. Resistance genes were mainly associated with tetracyclines, macrolides, lincosamides, and aminoglycosides. All ST1 isolates carried mrp and lacked tet(40), while all ST7 isolates showed the reverse pattern. CONCLUSION: Serotype 2 and ST1 predominated among the human S. suis isolates collected at this center. Resistance to tetracycline, erythromycin, and clindamycin was common, while susceptibility to the β-lactams tested was largely preserved. Differences in virulence- and resistance-associated gene profiles were also observed between the major lineages, indicating distinct genetic characteristics among the locally circulating isolates.

Streptococcus suis↗
PubMed2026

Comparative genomic analysis of Streptococcus parasuis and Streptococcus suis reveals mobile element-associated enrichment of antimicrobial resistance and lack of detectable same-MGE colocalization with virulence-associated genes within stable species boundaries.

Streptococcus suis is a major porcine pathogen and a zoonotic agent that causes meningitis and septicemia in humans. Streptococcus parasuis, a recently recognized close relative, remains poorly characterized with regard to its clinical significance and genomic features. In this study, we generated a single-contig closed genome assembly with genome-wide DNA methylation profiles for S. parasuis strain A1, isolated from a diseased pig in Xinjiang, China, and complemented in silico genomic predictions with isolate-level experimental validation of antimicrobial resistance (AMR) genotypes, virulence genotypes, and phenotypic susceptibility for this reference strain. Using this high-quality genome as a reference anchor, we performed comparative genomic analyses across 195 streptococcal genomes, comprising 15 S. parasuis and 180 S. suis strains, to distinguish genome-level co-occurrence of resistance and virulence determinants from their physical colocalization on the same mobile genetic element (MGE).Species boundaries remained clearly delineated at the genomic level, with a median interspecies average nucleotide identity (ANI) of approximately 86.0%, compared with intraspecies ANI medians of 97.5% for S. parasuis and 96.2% for S. suis. Pangenome analysis identified 12,693 gene clusters, of which 1086 were core clusters, and functional annotation revealed significant differences in accessory gene repertoires between the two species. Within this stable genomic framework, S. parasuis genomes carried a higher AMR gene burden; strain A1 harbored 10 AMR genes, multiple virulence-associated genes, three genomic islands, and eight prophage regions. For strain A1, PCR validation confirmed six AMR genes and six virulence genes, and disk diffusion testing demonstrated a multidrug-resistant phenotype consistent with the genotypic profile.Among 235 predicted mobile elements, 19 harbored AMR genes and seven carried Virulence Factor Database (VFDB) homologs, but none carried both categories simultaneously. This finding reflects a lack of detectable same-MGE colocalization under the applied annotation and assembly framework; it should not be interpreted as evidence of biological physical decoupling. Under a random-placement model, the expected number of co-carrying regions was only 0.57, and the probability of observing zero co-carrying regions was P = 0.55. This negative result should be interpreted with caution, given the limited number of cargo-bearing regions and the predominantly draft status of most genomes. Furthermore, the A1 genome contained multiple restriction-modification systems, showed depletion of several methylation motif families in mobile regions, and had limited CRISPR spacer matching evidence, suggesting prior exposure to the relevant sequence space. None of the genomes met our predefined criteria for whole-genome convergence.Collectively, our results support a model in which S. parasuis accumulates AMR-related genes in a modular fashion via mobile elements within stable species boundaries, with no detectable same-MGE colocalization of AMR and virulence determinants under our analytical pipeline. These findings imply that AMR surveillance strategies for this species should prioritize tracking mobile genetic elements rather than inferring wholesale genomic convergence toward S. suis.

Streptococcus suis↗
PubMed1978

Streptococcus suis type II (group R) as a cause of endophthalmitis.

A case is reported of a patient with bilateral endophthalmitis, meningitis, sensorineural deafness, labyrinthitis, and septicaemia due to Streptococcus suis type II (group R). The organism is known to produce epidemic meningitis, septicaemia, and purulent arthritis in piglets, but human infection is rare, and no other case reports of ocular infection are known. The organism was sensitive to penicillin at a minimum inhibitory concentration of 0.03 mg/1.

Deafness↗
PubMed1977

Teichoic acids of group D streptococci with special reference to strains from pig meningitis (Streptococcus suis).

Immunoelectrophoresis revealed in phenol extracts from S. faecalis and S. faecium a mixture of free and lipid-bound teichoic acids, both reactive with Group D antisera. In phenol extracts from S. suis only lipid-bound teichoic acid, also reactive with Group D antiserum, was seen. This difference probably accounts for the low yield of Group D antigen from S. suis as compared with S. faecalis and S. faecium when heating at pH 2 is used for extraction. When phenol is used good yields are obtained from S. suis as well as from S. faecalis and S. faecium. Lipoteichoic acids from S. faecalis and S. faecium have a backbone structure the same as or similar to that of Group A streptococcal teichoic acid. Lipoteichoic acid from S. suis has a structure differing from that of S. faecalis and S. faecium, e.g., possibly in the attachment of its glucosyl substituents. Precipitation reactions between S. suis lipoteichoic acid and Group D antisera were specifically inhibited by glucose. Reactions between S. bovis phenol extracts and some Group D antisera were also specifically inhibited by glucose, but extracts from S. faecalis and S. faecium were not. This may indicate a monosaccharide glucosyl substituent in teichoic acid from S. suis and S. bovis instead of the di- or trisaccharide previously postulated as the glucosyl substituent in the teichoic acid of S. faecalis.

Animals↗
PubMed2026

A descriptive analysis of Streptococcus suis-associated disease in Irish pigs from 2010 to 2024: serotypes, pathology, and antimicrobial resistance.

BACKGROUND: Streptococcus suis is a major cause of respiratory and systemic diseases in post-weaned pigs, leading to significant production losses and animal welfare concerns. This study provides the first long-term national level analysis of Streptococcus suis-associated disease (SSAD) in the Republic of Ireland. We examined the pig diagnostic submissions, characterised serotype distribution, antimicrobial susceptibility, and co-infection patterns from 2010 to 2024. RESULTS: The findings confirm that serotypes 9 and 2 or 1/2 were most frequently associated with disease. We observed a significant shift in recent years where serotype 9 has surpassed serotype 2 or 1/2 in number of occurrences. S. suis was frequently co-detected with viral pathogens including porcine reproductive and respiratory syndrome virus (PRRSV), porcine circovirus type 2, and swine influenza virus (SIV), as well as bacterial pathogens such as Actinobacillus pleuropneumonia and Pasteurella multocida, typically from pneumonic lungs. While resistance to tetracycline and erythromycin was high (44.4% to 65.8%), isolates remained susceptible to first-line beta-lactam antibiotics such as penicillin (7.9% resistance), ampicillin (5.5% resistance) and amoxycillin/clavulanate (0% resistance). CONCLUSION: The observed heterogeneity between and within herds challenges successful implementation of vaccination and highlights the need for ongoing disease monitoring. These findings provide the first in-depth assessment of SSAD in Ireland's pig population which will offer valuable insights for future surveillance efforts, including genomic studies and supporting evidence-based strategies and vaccine selection for controlling S. suis in Irish pig sector.

Ireland↗
PubMed1975

Streptococcal infection in young pigs. IV. An outbreak of streptococcal meningitis in weaned pigs.

Twenty-eight pigs died in an outbreak of streptococcal meningitis in an East Anglian herd. Most were 10-14 weeks old. The outbreak lasted from January to April and was finally controlled by antibiotic therapy. A similar number of losses had occurred in the previous year though no diagnosis had then been made. The causal agent appeared to be a haemolytic streptococcus belonging to group D and provisionally designated Streptococcus suis type 2. It is probably identical with de Moor's group R streptococcus which causes a similar disease in the Netherlands. It is serologically distinct from Streptococcus suis type 1 which causes meningitis in piglets. Type 2 infection in pigs appears to be widespread in England and Wales and to occur in animals up to the age of at least 14 weeks. A comparison is drawn between Str. suis meningitis in pigs and group B streptococcal meningitis in human infants.

Agglutination Tests↗
PubMed1978

Epizootic of concurrent cutaneous streptococcal abscesses and swinepox in a herd of swine.

Concurrent cutaneous abscesses and swinepox were observed in a herd of swine. An ungroupable hemolytic streptococcus was isolated from the abscesses. Tests indicated that streptococci isolated from different swine were similar if not identical. Swinepox lesions were observed on swine only after weaning. Lice (Haematopinus suis) were numerous on the suckling and weaned swine and appeared to be resistant to lindane. Abscesses, swinepox, and lice were eliminated after the swine were treated with an organic phosphate insecticide and antibacterial agents were added to the rations.

Abscess↗
PubMed1979

The distribution of isoprenoid quinones in streptococci of serological groups D and N.

The isoprenoid quinone contents of streptococci of serological groups D and N were investigated. Streptococcus faecalis, S. faecalis subsp. liquefaciens and S. faecalis subsp. zymogenes strains contained demethylmenaquinones with nine isoprene units as their major isoprenologues. Menaquinones with eight isoprene units predominated in S. faecium subsp. casseliflavus and S. faecium subsp. mobilis whereas menaquinones with nine isoprene units constituted the major components in strains of S. cremoris, S. cremoris subsp. alactosus, S. lactis and S. lactis subsp. diacetylactis. Strains of S. avium, S. bovis, S. durans, S. equinus, S. faecium, S. raffinolactis and S. suis contained neither menaquinones nor ubiquinones. The isoprenoid quinone data correlate well with other kinds of data on these organisms and are of value in the classification of these bacteria.

Enterococcus faecalis↗