Biomedical subjects

P A Murdough

Publications and source records attributed to P A Murdough.

6 recordsLinked to original sources

PubMed1997

Invasion of bovine epithelial cells by verocytotoxin-producing Escherichia coli O157:H7.

The ability of verocytotoxin-producing Escherichia coli (VTEC) O157:H7 to enter selected human (RPMI-4788 and HeLa) and bovine (MAC-T, mammary secretory; MDBK, kidney) epithelial cell lines was evaluated. All VTEC evaluated efficiently entered RPMI-4788 and MAC-T cell lines. VTEC entered MDBK cells at approximately 4% of MAC-T cells. VTEC were not able to invade HeLa cells. Presence of plasmid had no influence on efficiency of entry, nor did production of shiga-like toxin (SLT I or SLT II). Internalization required microfilaments, but not microtubules. Two types of adherence, localized and diffuse, were exhibited depending on isolate and cell line evaluated. Ability of VTEC to invade bovine mammary epithelial cells may be important in pathogenesis in the bovine, may indicate a route by which raw milk may potentially become contaminated, and may provide a reservoir of bacteria for the contamination of workers, equipment and carcass at time of slaughter.

Animals↗

PubMed1996

Effects of freezing on the viability of nine pathogens from quarters with subclinical mastitis.

Milk samples from 45 quarters containing mastitis pathogens were collected from lactating cows to determine the viability of those pathogens after freezing. An initial bacteria count was conducted, and samples were divided into 2-ml portions and frozen. Weekly bacteria counts were conducted for 6 wk. Viability after freezing was determined on five isolates of nine bacterial species: Staphylococcus aureus, Staphylococcus hyicus, Staphylococcus chromogenes, Staphylococcus xylosus, Streptococcus agalactiae, Streptococcus dysgalactiae, Streptococcus uberis, Corynebacterium bovis, and Escherichia coli. Bacteria counts were converted to logarithm base 10, and analysis of variance was conducted to determine alterations in viability over the 6-wk period. Freezing of quarter milk samples for 6 wk did not affect viability of any of these pathogens.

Animals↗

PubMed1994

Evaluation of a 1% iodophor postmilking teat sanitizer.

A natural exposure field trial a with positive control was conducted to evaluate bacteriological efficacy and teat conditioning qualities of an experimental postmilking teat dip. An experimental 1% iodine postmilking teat sanitizer with a 10% emollient system was compared with a 1% iodine plus 10% glycerin teat sanitizer. Efficacy of the two sanitizers was equivalent for all new IMI, major pathogens, and environmental pathogens. The products were not equivalent for efficacy against coliforms and coagulase-negative staphylococci. Fewer coliform IMI were diagnosed in the control group than in the treatment group. Differences were determined for efficacy against coagulase-negative staphylococci in favor of the treatment product. The products were equivalent for all clinical mastitis, including previously existing IMI that became clinical. The products were not equivalent for all or new clinical IMI with major pathogens, all environmental pathogens, or coliforms. Fewer infections were diagnosed in the control group than in the treatment group. Teat end and teat skin conditions improved with the use of the triple emollient, postmilking teat sanitizer under the winter conditions experienced during this field trial.

Animals↗

PubMed1994

Winter evaluation of a postmilking powdered teat dip.

A powdered teat dip designed for winter usage was evaluated for bacteriological efficacy and teat conditioning qualities. A positive control, natural exposure field trial was conducted for 3 mo on 509 lactating cows. Two sets of cows, primiparous and multiparous, were used. The trial compared efficacy of a powdered teat dip with a teat dip of 1% iodine plus 10% glycerin. Bacteriological efficacy among primiparous cows was equivalent for all major mastitis pathogens, environmental pathogens, and streptococci other than Streptococcus agalactiae. Efficacy was not equivalent against coagulase-negative staphylococci and all mastitis pathogens. Results suggested that the positive control product was more efficacious. Among multiparous cows, efficacy was equivalent against environmental mastitis pathogens and bacteriologically negative, clinical mastitis. The products were not equivalent against Staphylococcus aureus, coagulase-negative staphylococci, or all major mastitis pathogens, once again suggesting that the positive control product was more efficacious. Data indicated that germicidal activity of the powdered dip was not sufficient to reduce the incidence of new IMI caused by contagious or minor pathogens normally associated with teat skin. Application of a powdered postmilking teat dip during 3 winter mo in Idaho resulted in improved teat end condition among primiparous and multiparous dairy cows. Teat skin condition improved among primiparous but not among multiparous cows.

Allantoin↗

PubMed1993

Evaluation of 57 teat sanitizers using excised cow teats.

Fifty-seven teat dip formulations were tested for germicidal activity with an excised teat assay. Streptococcus agalactiae (ATCC 27956), Staphylococcus aureus (ATCC 29740), and Escherichia coli+ (a wild strain isolated from an Ohio cow 2956RR during the dry period) were used. Log reductions ranged from 5.6480 to 1.8330 for Strep. agalactiae compared with undipped controls. Staphylococcus aureus were reduced from 4.8972 to 1.0102. Escherichia coli were reduced from 5.8677 to 1.1450. The percentages of the products tested that had log reductions < 3 against Strep. agalactiae, Staph. aureus, and E. coli were 24, 30, and 61. Four teat dip formulations contained 4% sodium hypochlorite; all were effective against Strep. agalactiae, Staph. aureus, and E. coli. The three formulations containing glutaraldehyde were effective against the three mastitis pathogens. Formulations containing 1 and .5% iodine were not consistently effective against Strep. agalactiae, Staph. aureus, or E. coli. Teat sanitizers containing .5% chlorhexidine also showed inconsistency. Variations in formulation for products containing iodine or chlorhexidine affected germicidal activity.

Animals↗

PubMed1993

Efficacy evaluations on five chlorhexidine teat dip formulations.

Three developmental postmilking teat dip formulations containing chlorhexidine digluconate were evaluated against Staphylococcus aureus and Streptococcus agalactiae in sequential experimental exposure trials. Two additional commercial chlorhexidine digluconate teat dip products were evaluated in natural exposure trials. Under conditions of experimental challenge, the developmental formulations were efficacious against Staph. aureus but did not significantly reduce incidence of new IMI by Strep. agalactiae. None of the three formulations of a conventional germicide used as teat sanitizers effectively reduced incidence of new Strep. agalactiae IMI under experimental challenge conditions. In the natural exposure trials with negative controls, a .35% chlorhexidine teat sanitizer had efficacy of 88.7% against Staph. aureus and 51.4% against Strep. agalactiae. The .5% chlorhexidine product reduced Staph. aureus and Strep. agalactiae IMI by 86 and 56%, respectively.

Administration, Cutaneous↗