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Biomedical subjects

L K Fox

Publications and source records attributed to L K Fox.

72 records · Page 4Linked to original sources
PubMed1992

Diagnosis of Staphylococcus aureus intramammary infection by detection of specific antibody titer in milk.

The diagnostic value of the determination of Staphylococcus aureus antibody titer in milk as a method for identification of mammary quarters with S. aureus IMI was evaluated. Ten cows with a history of S. aureus IMI and 9 cows with no history of S. aureus IMI were sampled daily for 10 d. Quarter and composite milk samples were collected and processed by standard methods for concentration of S. aureus, S. aureus antibody titer (percentage of positive laboratory control), and SCC (cells per milliliter). Microbiologic culture identified 13 S. aureus-infected quarters from the 10 cows with a history of S. aureus IMI. Only 2 of the 130 samples (1.5%) from these infected quarters had undetectable concentrations of S. aureus. Antibody titers in milk from infected quarters of infected cows were below the previously established level considered to be indicative of IMI in 6 of 130 samples (4.6%). Four samples from infected quarters of infected cows had titers considered to be in the suspect range. The sensitivity of the antibody test was 83% (13% SE) when the suspect samples were included and 86% (12% SE) when they were not. Milk from uninfected quarters of cows with S. aureus IMI tended to have S. aureus antibody titers greater than the test's positive control, which would suggest that the quarters were infected with S. aureus. Antibody titer was below the infection threshold level in all pooled samples of uninfected cows, suggesting that the test correctly identified all cows free of S. aureus IMI.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1992

Comparison of media to isolate Staphylococcus aureus from teat skin and milking unit liners.

Four procedures were compared for isolation of Staphylococcus aureus from swabbing solutions of teat skin and milking unit liners from commercial dairies. In 2 procedures, 0.1 ml of swabbing solutions were added to either 5 ml Vogel-Johnson or Baird Parker broth media and enriched at 37 degrees C, 4 h. Following enrichment, 0.1 ml culture was transferred to modified Baird-Parker agar and incubated at 37 degrees C, 48 h. In the other 2 procedures, 0.1 ml of swabbing solution was directly placed on either blood or modified Baird-Parker agar plates and incubated at 37 degrees C 48 h. Combining results from all methods, Staphylococcus aureus were isolated from 72 of 913 (7.9%) skin samples, and 34 of 268 liners (12.6%). On average, 43.1% (31/72) of the S. aureus isolates were found by the enrichment in liquid Vogel-Johnson procedure. The average isolation percentage for other methods ranged from 19.4% to 25.0%. Isolation of S. aureus from milking unit liner or teat skin swabbing solutions was approximately twice as likely after enrichment in Vogel-Johnson liquid media as opposed to other methods of isolation. This indicates that enrichment in Vogel-Johnson liquid media improved recovery of S. aureus from swabbing solutions.

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PubMed1991

Effects of postmilking teat treatment on the colonization of Staphylococcus aureus on chapped teat skin.

Sixteen Holstein cows were used to test the effect of postmilking teat treatment on colonization and intramammary infection by Staphylococcus aureus on chapped teats. Treatments were (1) chapping the teat and using 1% I2/10% glycerin postdip solution, (2) 1% I2/10% glycerin postdip solution on nonchapped teats, (3) chapping the teat and using 10% glycerin postdip solution, (4) chapping the teat and not using a postdip solution. All mammary glands were free of S aureus teat skin colonization and intramammary infection at the start of the study. Teats selected for chapping were dipped in 1N NaOH prior to 3 applications of S aureus broth culture; cultures were applied at 12-hour intervals on all teats. Treatments were applied after each milking for 30 days and were initiated after the second broth dip. Teat skin swab specimens and milk samples were collected before treatment application. Teat skin condition was scored daily. Nonchapped teats (treatment 2) did not support skin or orifice colonization by S aureus. Treatment-1 teats healed most rapidly and supported less colonization in skin and orifice than did treatment-3 and -4 teats. Teat skin scores and skin colonization were lower for treatment-3 than treatment-4 teats. A correlation between teat skin colonization and teat skin conditions was found. Two intramammary infections were found in treatment-4 quarters and 1 in a treatment-3 quarter.(ABSTRACT TRUNCATED AT 250 WORDS)

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PubMed1991

Fomites and reservoirs of Staphylococcus aureus causing intramammary infections as determined by phage typing: the effect of milking time hygiene practices.

We studied the association of milkers' hands and milking unit liners as fomites, and teat skin as a reservoir, with S. aureus intramammary infections (IMI). Samples were collected from 40 commercial herds and S. aureus isolates were phage typed. Only 10 of 257 isolates were not typable. Of the milk samples, 8.4% had typable S. aureus; 4.5% and 9.2% of the skin and liner swabbings had typable S. aureus. Twenty-three different phage types were identified, 1 type was found in nearly 75% of the herds. Herds in which milking unit backflush was used were less likely to have the same phage type on the liners and the teat skin, and on the liners and milk samples, than herds that did not backflush. A greater percentage of liners had S. aureus of the same type as those causing S. aureus IMI, than skin swabbing solutions with the same type as that associated with IMI. Herds which did not use post-milking teat asepsis (teat dip) did not have a greater percentage of S. aureus isolates on the teat skin, nor were the S. aureus test skin isolates more likely to be of the same type as those causing intramammary infection. Results would suggest that the liner appears to be a significant fomite, that backflushing reduces its significance, and that teat skin is a less significant reservoir for S. aureus intramammary infection.

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PubMed1990

The effect of interferon-gamma intramammary administration on mammary phagocyte function.

The effect of recombinant bovine interferon-gamma on intramammary phagocyte function of mammary gland was studied in 4 Holstein cows (Study 1) and 7 Holstein cows (Study 2). Recombinant bovine interferon-gamma was intramammarily infused on day 6 of the dry period and phagocytes were collected from lacteal secretions and tested in vitro 24 hours later. Results from Study 1 indicate that phagocytosis of Escherichia coli and Staphylococcus aureus was significantly increased after than before interferon treatment. Similarly, the number of bacteria killed/active phagocyte was enhanced by treatment. Results from Study 2 suggested a trend towards increased production of oxygen dependent bactericidal components and increased killing ability by phagocytes exposed to interferon as compared to control phagocytes. These results from both studies suggest that intramammary infusions of bovine interferon-gamma can stimulate phagocyte function during the early phase of the dry period.

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PubMed1990

Mastitis control practices: differences between herds with high and low milk somatic cell counts.

Effects of differences in herd mastitis control management in maintaining low herd average SCC, was studied. Washington State DHI herds with Holstein cattle and enrolled in the SCC program (n = 309) were ranked by percentage of cows in their herd with SCC less less than or equal to 283,000 cells/ml. "Low herds" (n = 28) were among the 56 herds with the highest percentage of cows with SCC less than or equal to 283,000 cells/ml and "high herds" (n = 31) were among the 75 with the lowest percentage of cows with SCC less than or equal to 283,000 cells/ml. Herds were visited annually for 2 yr by a technician who collected samples and recorded data. Geometric mean bulk tank SCC during the year between herd visits was 175,000 and 460,000 cells/ml for low and high herds. Milking time hygiene practices, teat dipping, and dry cow therapy were practiced with equal frequency on low and high herds. Differences in function and maintenance of milking equipment did not discriminate between herd groups. Differences in mastitis control management of low versus high SCC herds were that managers of excellent control herds more frequently had highest producers milked first and clinical cows milked last; had automatic milking unit detachers; kept moisture content of cow bedding lower; and had workers disinfect teat ends prior to intramammary antibiotic treatment. Managers of low herds were more likely to use computers and attend dairy informational meetings. Results suggest subtle differences in mastitis control strategies differentiate the low and high SCC herd groups.

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PubMed1989

Effect of segregation on prevention of intramammary infections by Staphylococcus aureus.

Effectiveness of segregating cows with Staphylococcus aureus intramammary infections was studied over 1 yr. Nine herds were split into control (n = 5) or segregated (n = 4) groups. Cows with S. aureus intramammary infections were milked last in segregated herds. Monthly milk samples were collected aseptically for microbiologic analysis. Mean incidences of S. aureus intramammary infections were 3.7 and 4.3 cases/100 cow-mo in segregated and control herds. The mean prevalence of S. aureus intramammary infections decreased in both segregated and control herds during the study. Mean percentages of cows with S. aureus intramammary infections at the beginning and end of the study were 33.7 and 21.5 in segregated herds and 25.3 and 15.0 in control herds. Cows in all herds with S. aureus intramammary infections were preferentially culled. There were no significant differences in incidence and prevalence of S. aureus intramammary infections between groups, suggesting that S. aureus intramammary infections can be controlled without segregation.

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PubMed1988

Teat skin normal flora and colonization with mastitis pathogen inhibitors.

Isolates of bacteria from normal teats were used to attempt colonization of teats of dry cows or neonatal calves. Isolates for inoculation were chosen on the basis of ability to inhibit mastitis pathogens in vitro, with the ultimate goal of in vivo inhibition of mastitis pathogens at the teat surface. Three bacterial normal flora isolates (Corynebacterium xerosis, Bacillus sp. and Aerococcus viridans) persisted less than 10 days on the teats of dry cows. The fourth isolate, Staphylococcus hominis 1, was studied in greatest detail because studies characterizing the normal teat flora showed staphylococci to be the predominant flora. The S. hominis 1 isolated used for inoculation was an inhibitor of Gram-positive mastitis pathogens. It was a biotype not found on these teats prior to inoculation, thus facilitating identification of the inoculated isolate on sequential sampling. Colonization of newborn calves, before other bacterial flora became established, resulted in recovery of inoculated S. hominis 1 for an average of 51 days or longer. On dry cow teats it was detected for up to 28 days. On several occasions the inoculated S. hominis 1 was found in pure culture. Since many new infections occur during the dry period, the colonization of dry cow teats with S. hominis 1 organisms inhibitory for Gram-positive pathogens should be tested as an adjunct to other methods of mastitis prevention.

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PubMed1988

N-acetyl-beta-D-glucosaminidase activity in whole milk and milk fractions.

Experiment 1 was conducted to determine NAGase activity in skim, fat, and cell pellet fractions of foremilk and stripping milk from infection-free quarters. Changes in milk NAGase activity during a 12 h in vitro incubation were also determined. Eight cows, two quarters per cow, were used. One quarter of each cow received an intramammary infusion of oyster glycogen. N-Acetyl-beta-D-glucosaminidase activity was highest in stripping milk and in milk from infused quarters. The percentages of NAGase activity in skim, fat, and cell pellet fractions were 62.6, 22.4, and 12.6. The NAGase activity of milk incubated in vitro did not significantly change over time. Experiment 2 was conducted to determine if neutrophils lost NAGase activity during extravasation into milk. Leukocytosis was induced in infection-free quarters of five cows. The NAGase activities of peripheral neutrophils and milk neutrophils were not significantly different. Results from both studies suggest that the major source of milk NAGase is the mammary epithelial cell and that milk somatic cells contribute less than 15% of the total milk NAGase activity.

Acetylglucosaminidase↗
PubMed1988

Functional activity of neutrophils from bovine mammary glands infected with Staphylococcus aureus.

To test the effect of Staphylococcus aureus infection on mammary neutrophil function, intramammary neutrophils from S. aureus-infected quarters (n = 8), from adjacent uninfected quarters (n = 8) of S. aureus-infected cows, and from quarters (n = 8) of uninfected cows were collected and incubated with S. aureus in vitro. Mean percent neutrophils phagocytizing, number S. aureus per neutrophil, and log10 viable phagocytized S. aureus/ml were: 53.2, 6.4, and 4.72. Differences in function of neutrophils collected from infected and uninfected quarters were not statistically significant. Results indicate that function of neutrophils from S. aureus-infected quarters is similar to function of neutrophils from uninfected quarters.

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PubMed1988

Function of phagocytes obtained from lacteal secretions of lactating and nonlactating cows.

Phagocytes, macrophages and neutrophils, were obtained from lacteal secretions of lactating (n = 13) and nonlactating cows (n = 14). Secretions from nonlactating cows were collected at 7 and 14 days after cessation of lactation. Phagocytes were incubated in vitro with Staphylococcus aureus or Escherichia coli, and function was assessed by fluorescent microscopy of cell suspensions stained with acridine orange and crystal violet. A greater percentage of macrophages from nonlactating cow secretions collected on day 14 phagocytized bacteria than did those collected on day 7. A greater percentage of macrophages from nonlactating cow secretions collected on days 7 and 14 phagocytized bacteria than did neutrophils obtained from the same secretions. A similar percentage of phagocytes from nonlactating cow secretions phagocytized bacteria, compared with phagocytes from lactating cow secretions. Results indicated that the intramammary macrophage may be most important in defense of the mammary gland during the early nonlactating period, because it was more phagocytic than the neutrophil and was more active at 14 days than at 7 days into the nonlactating period.

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PubMed1987

The effect of intramammary antibiotic therapy at calving on udder health traits.

The effect of intramammary antibiotic therapy at calving on mastitis infection prevalence, linear score milk somatic cell count, and milk NAGase activity, 30 d postpartum, and on milk production, 90 to 120 d postpartum, was tested. Cows (n = 175) were split into treatment and control groups at drying off. All cows received commercial dry cow therapy. At calving, treated cows received commercial lactating cow therapy in all quarters after the first two milkings; control cows were not treated. Composite milk samples were aseptically collected from all cows at drying off, calving, and 30 d postpartum. Udder health traits: linear score milk SCC, NAGase activity, and bacterial content in milk, were determined on all samples. The first three DHI milk weights were recorded for all cows. Treatment and control cows had similar prevalences of intramammary infections during the dry and 30-d postpartum periods. Least squares means of linear score milk SCC and NAGase activities were similar at drying off and calving. Cell count scores were similar between groups; NAGase activities were higher in control cows at 30 d postpartum. Control cows tended to produce more milk postpartum. Results demonstrated no advantage of intramammary therapy at calving in improving milk production or udder health.

Acetylglucosaminidase↗
PubMed1986

Changes in bovine milk secretion following intramammary infusions of concanavalin A, oyster glycogen, or water.

Effects of sterile intramammary infusion of Concanavalin A on milk secretion were contrasted with infusion of oyster glycogen or water. Twenty-four cows were infused intramammary with 100 mg Concanavalin A, oyster glycogen in 20 ml water, or with 20 ml water alone. Concentrations of lactose, somatic cells, immunoglobulins G and A, serum albumin, and activity of N-acetyl-B-D-glucosaminidase were determined in milk. Blood N-acetyl-B-D-glucosaminidase activity and concentrations of blood immunoglobulins G and A and serum albumin were determined. Oyster glycogen and concanavalin A caused inflammation in treated quarters; peak elevations of milk somatic cell counts, serum albumin, immunoglobulin G concentrations, and N-acetyl-B-D-glucosaminidase activity were at 12 to 36 h following treatment. Milk production and lactose concentration were reduced by oyster glycogen and Concanavalin A. Selective indices of relative accumulation of milk immunoglobulins decreased following Concanavalin A and oyster glycogen, whereas the N-acetyl-B-D-glucosaminidase activity selective index generally remained unchanged. Inflammation reduced the selective accumulation of immunoglobulins, and absence of change in the N-acetyl-B-D-glucosaminidase selective index indicated that blood is not a major source of milk N-acetyl-B-D-glucosaminidase.

Acetylglucosaminidase↗
PubMed1985

Effect of infection status on quarter milk production and composition following omitted milking.

Sixteen cows in middle to late lactation were milked for 3.5 days at 12-h intervals except for a 24-h interval between third and fourth milkings. A cowside quarter milking unit was used. Quarters were classified by infection status. Milk chloride, lactose, somatic cell concentrations, N-acetyl-B-D-glucosaminidase activity, and cell differential counts were determined. Following the omitted milking, concentrations of milk chloride and somatic cells were elevated and lactose concentration reduced in infected quarters. In uninfected quarters, chloride concentration increased, and lactose concentration decreased after the 24-h interval. The milk N-acetyl-B-D-glucosaminidase activity was elevated only in quarters infected with major pathogens. Changes of milk secretion induced by an omitted milking are affected by infection status, and additional secretory cell damage in quarters infected with a major pathogen may result from an omitted milking.

Acetylglucosaminidase↗
PubMed1985

Factors related to milk loss in quarters with low somatic cell counts.

Relationship between milk production and milk composition was studied through comparisons of udder halves within cow. Cows were milked by milking unit for separate quarters of udder. Six trials had six cows per trial. Trial length was 3 d, and milkings were at 12-h intervals. Foremilk samples were taken aseptically for bacterial analysis. Milk weights by quarter were recorded, and samples by quarter were analyzed for concentrations of lactose, somatic cells, and chloride. Milk cell differential counts and N-acetyl-B-D-glucosaminidase activity also were determined. Eighty-four percent of quarter milk samples contained less than 400,000 cells/ml. Differences between right and left udder halves with respect to all measurements were computed. For halves of udders within-cow correlation coefficients for differences between production and log(base 2) somatic cell count, lactose, chloride, bacterial presence, neutrophil percent, lymphocyte percent, macrophage percent, and N-acetyl-B-D-glucosaminidase activity were -.16, .23, -.31, .09, .12, .01, -.14, and -.41. Regression coefficients of milk production (kg) on somatic cell count log(base 2) cells per milliliter, lactose (%), chloride (mg/100 ml), and N-acetyl-B-D-glucosaminidase (nmol/min per ml) were -.12, .57, -.05, and -.46. From negative correlations between production and concentrations of chloride, somatic cells, and N-acetyl-B-D-glucosaminidase activity, differences between udder halves in production may be related to changes of the blood-milk barrier, leukocyte diapedesis, and loss of integrity of secretory cells.

Acetylglucosaminidase↗
PubMed1981

Concentrations of glucocorticoids, bovine serum albumin, and somatic cells in mastitic milk.

Milk glucocorticoids, bovine serum albumin, and somatic cells were measured during experimental mastitis. Six cows were allotted evenly into injected and control groups. Injected cows received a single intramammary infusion of .5 mg sterile Escherichia coli endotoxin in a quarter chosen at random. Control cows were untreated. Milk quarter samples were taken from all cows at both milkings and 9 h following midnight milking 1 day prior to glucocorticoid concentrations occurred 9 h postinjection and were 17.5 ng/ml (+/- 10.2), and 4.4 ng/ml (+/- 2.3) in injected and noninjected quarters of the same cows. In injected cows glucocorticoid concentrations returned to baseline within 36 h. Glucocorticoids in control quarters were .4 ng/ml (+/- .3). Peak bovine serum albumin was 27.8 ng/ml (+/- 22.8) and .56 bg/ml (+/- .09) in injected and noninjected quarters in the same cows as compared to a baseline of .2 mg/ml (+/- .04) in control cows. In injected quarters, bovine serum albumin remained elevated for 4 days, and somatic cells were elevated for 6 days after injection. Glucocorticoids, bovine serum albumin, and somatic cells were elevated markedly in injected quarters, and unlike concentrations of bovine serum albumin and somatic cells, elevated glucocorticoids in injected quarters were short lived.

Animals↗
PubMed1981

Effect of cortisol on the bactericidal function of the bovine milk neutrophil in vitro.

Milk neutrophils and Staphylococcus aureus were incubated for 2 hours at a 1:1 ratio in sterile common milk media with various cortisol concentrations. Milk neutrophils were harvested twice at a weekly interval from 6 cows. Mean percentage of phagocytosis (+/- SD) was 20.2 +/- 10.1, 34.6 +/- 21.0, 27.2 +/- 17.8, 30.3 +/- 21.4, and 23.9 +/- 16.7 for treatments with 0, 20, 40, 60, and 10,000 ng/ml. Mean percentage of kill was 12.7 +/- 12.4, 14.9 +/- 11.2, 11.2 +/- 10.9, 12.1 +/- 12.3, and 6.6 +/- 10.3, for 0, 20, 40, 60, and 10,000 ng/ml treatments. Mean percentage of efficiency of kill, a measure of the ability of neutrophil to kill phagocytized bacteria, was 49.5 +/- 40.0, 53.5 +/- 38.8, 46.9 +/- 38.0, 34.9 +/- 35.2, and 27.3 +/- 32.8, respectively. The pharmacologic concentration (10,000 ng/ml) of cortisol depressed kill, whereas physiologic concentrations (20, 40, and 60 ng/ml) of cortisol increased phagocytosis, but did not affect kill.

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