Forty-two strains of mesophilic lactic streptococci, enterococci, lactobacilli, leuconostoc, staphylococci, and other dairy- and food-related microorganisms were tested for their sensitivity to 30 antibiotic and antimicrobial agents. Elliker's lactic agar served as the growth medium; incubation temperature and times were varied according to individual culture growth requirements. Commercially available multitipped sensitivity discs were used. Almost all the microorganisms investigated, except for Streptococcus thermophilus, exhibited definite resistance to eight different sulfonamides. Most of the strains of starter streptococci and Lactobacillus bulgaricus were sensitive to all 16 antibiotic or antimicrobial agents (included in this survey) used for mastitis control. Strains of Leuconostoc dextranicum, Streptococcus faecalis, Streptococcus durans, and Brevibacterium linens were less affected.
1Journal Paper No. J-7813 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa 50010. Project No. 1838.