Lancefield group C Streptococcus dysgalactiae is an emerging fish pathogen, which was first isolated in 2002 in Japan. Streptococcus dysgalactiae isolates collected from diseased fish in Japan (n=12), Taiwan (n=12), China (n=2), Malaysia (n=3), and Indonesia (n=1) were characterized using biased sinusoidal field gel electrophoresis (BSFGE), sodA gene sequence analysis, and antimicrobial susceptibility. These isolates exhibited high phenotypic homogeneity irrespective of the countries from where the strains were collected. Seventeen isolates were found to be resistant to oxytetracycline and carried the tet(M) gene, except for the strains collected in Taiwan and the PP1564 strain collected in China. The sodA gene sequence analysis revealed that 23 isolates were identical, except for one Japanese isolate (KNH07902), in which a single nucleotide differed from that of the other isolates. Based on BSFGE typing by ApaI macrorestriction, the isolates - including the Japanese, Taiwanese, and Chinese isolates - could be grouped into one main cluster at a 70% similarity level. However, the macrorestriction genotypes of some isolates were apparently distinct from those of the main cluster.
1. Hubbard x Hubbard (HH) and Shaver x Shaver (SS) chicks given a dietary supplement of either 50 mg/kg oxytetracycline (OTC) or 1 g/kg Lactobacillus culture (LC) were exposed to 36 +/- 1 degrees C for 3 h daily from day (d) 21 to 42. 2. Prior to heat treatment, body weight (d 21) and weight gain (d 1 to d 21) of OTC and LC birds were greater than those fed the control diet. Chicks given LC had the best food efficiency followed by OTC and control birds during d 1 to d 21. Body weight (d 1 and d 21) and weight gain (d 1 to d 21) were greater for HH tlhan SS chicks. 3. After 3 weeks of heat exposure, birds receiving the LC diet had greater body weight and weight gain, higher food intake and lower food efficiency than OTC and control chicks. 4. Antibody production against Newcastle discase vaccine on d 21 was not affected by strain or diet. On d 42, while diet had negligible effect on this variable among the SS broilers, HH birds fed LC had higher antibody production than those on the control diet. 5. Neither strain nor diet had a significant effect on mortality.