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Table 2 Summary of the experimental conditions of S. suis co-infection with viral pathogens using in vivo models

From: Review of the speculative role of co-infections in Streptococcus suis-associated diseases in pigs

S. suis co-infection parhogen Age of pigs at the infection
Virus / Bacteria
Route of infection
Virus / Bacteria
Virus strain and dose S. suis strain and dose Main observed effects of co-infection Ref
PRRSV 19 days 26 days IN IN 2 × 104.99 TCID50, high virulent PRRSV strain, genotype 2
2 × 104.47 TCID50, low virulent PRRSV vaccine strain RespPRRS/Repro™
2 × 108.3 CFU; serotype 2 (no further details on the strain) Severity of clinical signs, mortality, and interstitial pneumonia lesions (especially those infected with the high virulent PRRSV strain) [61]
  98 days of sow gestation 5 days IN IN 103.5 TCID50, PRRSV, genotype 2 8 × 107 CFU, serotype 2 (no further details on the strain) Susceptibility of piglets to bacterial infection [52]
  21 days 28 days IN/IM IN/IM 2 × 104.97 TCID50 PRRSV, genotype 2 109 CFU; serotype 7 (no further details on the strain) Clinical signs and mortality [65]
  49 days 42 days* IN IN 2 × 104 TCID50
Asian HP-PRRSV strains; US PRRSV strains, genotype 2
106 CFU; serotype 2 (no further details on the strain) Clinical severity related to PRRSV virulence;
levels of proinflammatory cytokines
[64]
  28 days 21 days* IN IM 106 TCID50
PRRSV MLV-like strain
2 × 108 CFU; serotype 2 low virulence strain (no further details on the strain) Clinical signs and mortality [67]
SIV 35 days 38 days IN IN 2 × 107 egg infectious dose50/mL, H1N1 strain 2 × 106 CFU; serotype 2; ST7 Clinical signs, pathological changes, and cell apoptosis; gene expression for pro-inflammatory mediators [76]
PCV-2 28 days 33 days IN/IM
2 mL/3 mL
IN/IM
2 mL/3 mL
2 × 106.5 TCID50 4.5 × 109 CFU; serotype 2; ST7 Clinical signs; gene expression for pro-inflammatory mediators; gene expression for CD4, CD8, and MHC-II [21]
PRV 63 days 63 days IN IN 5 × 103 TCID50 high or low virulent PRV strains 109 CFU S. suis serotype 2 (no further details on the strain) Clinical signs [107]
  1. * Animals were infected first with S. suis and then infected with a virus.
  2. IM: intramuscular injection; IN: intranasal inoculation; PRSSV: Porcine Reproductive and Respiratory Syndrome Virus; SIV: Swine Influenza Virus; PCV-2: Porcine Circovirus type 2; PRV: pseudorabies virus; TCID50: medium tissue culture infectious dose; CFU: colony-forming units; ST: sequence type.
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