[Antimicrobial susceptibility in vitro of 32 drugs against pig Streptococcus isolates in China].

A number of 65 Streptococcus species isolated from diseased pigs were surveyed for in vitro minimal inhibitory concentration (MIC) to 32 drugs by microdilution test. Clinical categorization of isolates as susceptible or resistant was based on MIC interpretative standards of the National Committee for Clinical Laboratory Standards(NCCLS). None of the strains were susceptible to all antimicrobial compounds tested and most strains (96.6%) were multidrug-resistant. High level resistance to streptomycin was also detected. Resistance to sulfonamides (92.3% - 98.3%), aminoglycosides (70.8% - 78.5%), lincosamides (66.2% - 64.6%), tetracyclines (72.3%) and macrolides (53.8% - 67.7%) were most frequent, then beta-lactam (18.5% - 56.9%) and quinolones (36.9% - 78.5%) resistance, while all strains were susceptible to florfenicol, 78.5% strains were susceptible to Taimulin. All resistant strains to beta-lactam were tested for beta-lactamase production and the results were negative.