Effect of cefquinome treatment onto tonsillar colonization with Streptococcus suis

Healthy pigs carrying Streptococcus (S.) suis on their tonsils are known to be a source of S. suis transmission in pig herds. S. suis can cause severe clinical disease, especially if co-infection with other pathogens occur. As a precautionary measure in experimental infection trials with other pathogens, pigs are treated with antibiotics to eliminate as much as potentially pathogenic bacteria as possible. The effect of cefquinome treatment was evaluated for pigs colonized with S. suis.

Thirty clinically healthy ten-week-old crossbred piglets from a herd unsuspicious for PRRSV and SIV, but with a prehistory of S. suis serotype 2 -associated diseases such as meningitis, arthritis and sudden deaths, were selected for an infection trial with influenza A virus. After the pigs’ arrival at the isolation facilities tonsillar swabs were immediately taken from all animals and submitted for bacteriological examination. Following, antibiotic susceptibility of recovered S. suis isolates were analyzed by agar disk diffusion test. Accordingly to test results, all pigs were treated intramuscularly on three consecutive days with cefquinome (Cobactan® 2,5 %, 2mg/kg BW). Five days after the last treatment tonsillar swabs were again tested for S. suis. All isolates were characterized by multiplex PCR targeting S. suis housekeeping gene gdh, capsular genes for the differentiation of serotypes 1, 2, 7 and 9, as well as genes for virulence-associated factors epf, mrp, sly and arcA.

Pigs stayed healthy during the examination period. S. suis was isolated from tonsillar swabs prior to treatment from 25 out of 30 piglets (83 %), but isolates did not belong to serotypes 1, 2, 7 or 9. All isolates were negative for epf, mrp and sly, but were positive for arcA. After treatment still 16 out of 30 tonsillar swabs were tested positive for S. suis (53 %). Two of them were tested negative at first examination but positive after treatment. However, a semiquantitative assessment of the bacterial burden resulted in a significant reduction of bacterial growth after treatment.

It was not possible to eliminate S. suis consistently from tonsillar tissue, but bacterial load was significantly reduced. S. suis strains isolated in this study were susceptible to cefquinome in vitro, but adequate antibacterial concentrations might not be achieved in tonsillar tissue.

Disclosure of Interest: None Declared.