A study of the occurrence, phenotypic and genotypic diversity and both in vitro and in vivo growth responses of Enterococcus spp. isolated from bovine origin

by 1978- Petersson-Wolfe, Christina Sonja

The occurrence, phenotypic and genotypic diversity, and both in vitro and in vivo growth response of Enterococcus spp. isolated from bovine origin were investigated. A total of 386 enterococcal and streptococcal isolates from bovine mammary glands (n = 335), beddings samples from a commercial dairy herd (n = 31) and dairy feed samples (n = 20) were collected and used for the current study. Enterococcus spp. represented 42.7% of all isolates collected. When comparing standard biochemical testing to the API 20 STREP system, the two systems were in agreement for 92.1% (152 of 165) of the enterococci, 36.9% (72 of 195) of the environmental streptococci and 50.0% (13 of 26) of the Streptococcus dysgalactiae isolates. An in vitro study was conducted to examine the growth of enterococcal isolates in mammary secretion from various stages of lactation. These results suggest the source of enterococcal isolates and the bacterial species significantly contribute to the ability of that organism to adapt to mammary secretion from various stages of lactation. An in vivo study was conducted to examine the physiologic effects of 4 E. faecium isolates in the bovine mammary gland in early and late lactation. Isolates were selected based on growth response from the in vitro study. Stage of lactation contributed greatly to the ability of the test organism to replicate or grow. Additionally, all 4 tested E. faecium isolates were able to establish intramammary infection. However, poorly adaptive isolates based on in vitro responses were more likely to cause infection and cause clinical signs in vivo than the highly adaptive isolates ii tested. Genotypic evaluation was characterized using pulsed-field gel electrophoresis analysis of SmaI restriction patterns. These data suggest enterococci of bovine origin are genetically diverse while isolates of various sources appear to cluster together. These data have provided initial information regarding growth responses of enterococci in vitro and in vivo. However, further studies are required to examine the factors contributing to virulence. iii