Identification and antimicrobial resistance of Streptococcus uberis and Streptococcus parauberis isolated from bovine milk samples.

The conventional identification of Streptococcus uberis/parauberis group (n = 137) in clinical and subclinical bovine mastitis samples originating from 111 different farms was compared with identification based on 16 and 23S rRNA gene HindIII RFLP patterns used as operational taxonomic units in numerical analyses. On the basis of ribopattern analysis only 2 isolates belonged to S. parauberis, which is thus not a frequent cause of bovine intramammary infections in Finland. According to in vitro antimicrobial susceptibility testing, Streptococcus uberis is susceptible to beta-lactam antibiotics. The prevalence of erythromycin (15.6%) and oxytetracycline (40.6%) resistance of clinical S. uberis isolates was higher than reported previously among subclinical isolates. The 2 subclinical S. parauberis isolates were susceptible to all the antimicrobials tested.