Streptococcus suis type 1 infection of sucking pigs

Streptococcus suis: past and present

Steptococcus suis is a Gram-positive, facultatively anaerobic coccus that has been implicated as the cause of a wide range of clinical disease syndromes in swine and other domestic animals. In swine, the disease has spread worldwide but is more prevalent in countries with intensive swine management practices. The disease syndromes caused by S. suis in swine include arthritis, meningitis, pneumonia, septicaemia, endocarditis, polyserositis, abortions and abscesses. S. suis has also been implicated in disease in humans, especially among abattoir workers and swine and pork handlers. In humans, S. suis type 2 can cause meningitis, which may result in permanent hearing loss, septicaemia, endocarditis and death. The pathogenic mechanism of S. suis is not well defined. Several virulence factors have been identified, but their roles in pathogenesis and disease have not been well elucidated. Much work is in progress on characterization of virulence factors and mechanisms, with emphasis on the control of the disease. Because of the non-availability of suitable immunoprophylaxis, control of S. suis infection has depended mainly on the use of antimicrobials.

Biochemical traits and antimicrobial susceptibility of Streptococcus suis isolated from slaughtered pigs

A total of 522 Streptococcus suis isolates were recovered from the tonsils of slaughtered pigs by culturing on media containing different specific antisera. The serogroup reactions were determined by coagglutination. The most frequently isolated serotype was serotype 4 (representing 28.7% of the isolates), followed by serotype 3 (24.9%) and serotype 2 (22.6%). Typable isolates were examined by growth in 6.5% NaCl, amylase activity, acetoin production, susceptibility to optochin and production of acid from mannitol, melibiose, raffinose, salicin, sorbitol and trehalose. Finally, all isolates were tested for antimicrobial susceptibility against ampicillin, cephalotin, lincomycin, neomycin, penicillin, spiramycin and trimethoprim-sulphamethoxazole using the disk-diffusion technique. All isolates were amylase-positive and acetoin-negative, and failed to grow in 6.5% NaCl broth. Nine isolates were optochin-susceptible. Moreover, 10 isolates produced acid from mannitol, 21 produced acid from sorbitol, and 36 and 37 did not produce acid from salicin and trehalose, respectively. Six salicin- and trehalose-negative isolates and two mannitol- and sorbitol-fermenting isolates were found. Biochemical differences between serotypes were not observed. The most active drugs against S. suis were the beta-lactam antibiotics, although only 83.3%, 70% and 78.5% of isolates were susceptible to ampicillin, cephalotin and penicillin, respectively. Half of the isolates were resistant to trimethoprim-sulphamethoxazole, and resistance to lincomycin, neomycin and spiramycin appeared to be very high.

Lesions caused by natural infection with Streptococcus suis type 9 in weaned pigs

In this paper we report on the spectrum and frequency of lesions observed in a prospective study of naturally occurring infections with Streptococcus suis type 9 (SS-9) in weaned pigs. SS-9 produced arthritis, meningitis, interstitial pneumonia, and endocarditis in 100%, 91%, 73%, and 42%, respectively, of pigs dying from the disease. The lesions were similar to those caused by S. suis type 2 (SS-2), however, SS-9 produced a different frequency of lesions. In SS-2 infections, bronchopneumonia is the most commonly observed lesion; meningitis, arthritis, and endocarditis are less frequently observed. Thus, SS-9 produced a different distribution of lesions from that reported for SS-2. Possible explanations for the differences found are discussed.

Streptococcus suis serotypes associated with disease in weaned pigs

Streptococcus suis was recovered from 9 outbreaks of septicaemia and meningitis in weaned pigs between 1979 and 1983. Fifteen isolates from 7 outbreaks were identified as S. suis type 9, and 3 isolates from 2 outbreaks as S. suis type 2. Three further isolates of S. suis type 2 and an isolate of S. suis type 3 were recovered from cases of bronchopneumonia in weaned pigs from 4 other piggeries.