Therapy of Subclinical Mastitis during Lactation.

This study tested the hypothesis that increasing the duration and/or frequency of antimicrobial treatment of subclinical mastitis would result in a higher bacteriological cure rate. Glands with a positive California mastitis test (CMT) from cows with an elevated somatic cell count (>500,000 cells/mL) that had an intramammary infection were randomly assigned at cow level to no treatment (Control; n = 80 glands), intramammary infusion of 200 mg cloxacillin sodium on three occasions at 48 h intervals (3 × 48 h; n = 273 glands), five occasions at 24 h intervals (5 × 24 h; n = 279 glands), or on five occasions at 48 h intervals (5 × 48 h; n = 72 glands). Glands were resampled at 21 (±3) and 28 (±3) days after initiation of treatment. The gland-level cure rate for any pathogen was 5/80 (6.2%), 139/173 (49.8%), 172/297 (61.6%) and 58/72 (80.6%) for Control, 3 × 48 h, 5 × 24 h and 5 × 48 h, respectively. The cure rate for major pathogens (defined as Staphylococcus aureus or Streptococcus spp.) was 4/52 (7.7%), 84/197 (42.6%), 96/183 (52.5%) and 36/48 (75%) for Control, 3 × 48 h, 5 × 24 h and 5 × 48 h, respectively. We conclude that treatment was superior to no treatment, and bacteriological cure rate was higher with the 5 × 24 h protocol than for the 3 × 48 h protocol and was higher with the 5 × 48 h than the 5 × 24 h protocol.

A new growth medium for rapid selection and purification of Clostridium proteoclasticum transposon mutants.

Clostridium proteoclasticum is commonly associated with the rumen microflora of pasture-fed cattle and sheep and has significant hemicellulose degradation abilities. Genes involved in plant fibre breakdown are commonly identified by producing site-specific mutations. However, the genetics of C. proteoclasticum and other closely-related Butyrivibrio/Pseudobutyrivibrio species is not well-established. Therefore random transposon mutants of C. proteoclasticum were generated by conjugation with Enterococcus faecalis containing Tn916. A new counter-selection agar medium was developed containing L-arabinose and D-raffinose as carbon sources, both of which are utilized by C. proteoclasticum only, and also ciprofloxacin, an antibiotic that suppresses the growth of E. faecalis. With this new medium the enhanced growth and more rapid separation of C. proteoclasticum transposon mutants from the background of E. faecalis cells was made, thereby facilitating the selection of transposon mutants and the identification of their Tn916 insertion sites.

Isolation of lactic acid bacteria with inhibitory activity against pathogens and spoilage organisms associated with fresh meat.

The use of lactic acid bacteria (LAB) as protective cultures in vacuum-packed chill-stored meat has potential application for assuring and improving food quality, safety and market access. In a study to identify candidate strains suitable for evaluation in a meat model, agar-based methods were employed to screen 181 chilled meat and meat process-related LAB for strains inhibitory to pathogens and spoilage organisms of importance to the meat industry. Six meat-derived strains, including Lactobacillus sakei and Lactococcus lactis, were found to be inhibitory to one or more of the target strains Listeria monocytogenes, Brochothrix thermosphacta, Campylobacter jejuni and Clostridium estertheticum. The inhibitory agents appeared to be either cell-associated or molecules released extracellularly with bacteriocin-like properties. Variations detected in the antimicrobial activity of LAB associated with changes to test parameters such as substrate composition underlined the importance of further in situ evaluation of the inhibitory strains in stored meat trials.

Adhesion of Yersinia enterocolitica to non-cultured epithelial cells from pig and rabbit ilea.

A simple and reliable method was developed to isolate intact epithelial cells from pig and rabbit ilea and these were used to investigate the adhesion of Yersinia enterocolitica. Hydrophobic interaction was eliminated by treating the bacterial culture with 0.8 M tetramethyl urea (TMU). Virulent strains of Y. enterocolitica had significantly greater attachment than avirulent strains but both attached in a linear dose-dependant fashion. Epithelial cells prepared from pig ilea were attached to more readily than those prepared from rabbit ilea.