| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
1 Mastitis Research Laboratory, Hill Farm Research Station, Louisiana State University Agricultural Center, Homer 71040
2 West Agro Inc., Kansas City, MO 64153
Corresponding author: William Owens, e-mail: wowens{at}agcenter.lsu.edu
 |
ABSTRACT |
|---|
 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONREFERENCES |
|---|
Key Words: teat dip • Staphylococcus aureus • Streptococcus agalactiae
Abbreviation key: TSA = trypticase soy agar, TSB = tryptic soy broth
|
INTRODUCTION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONREFERENCES |
|---|
The experimental challenge model (NMC protocol B) is the industry standard for manufacturers of agricultural disinfectants for determining efficacy of new teat dip products. Testing of products following these guidelines provides dairy farmers with a "pool" or list of tested products of proven efficacy, and ensures that such products adhere to minimum standards of performance (National Mastitis Council, 2003).
The Hill Farm Research Station dairy herd of 53 Jersey cows was used in a experimental infection trial to determine the efficacy of an iodine teat dip for preventing new IMI with Staphylococcus aureus and Streptococcus agalactiae. The product was provided by West Agro, Inc., Kansas City, MO. The trial was carried out following the general procedures recommended by the National Mastitis Council (NMC) with a published efficacy protocol (Hogan et al., 1990). The trial was performed to provide the manufacturer with a published efficacy protocol that appears in the NMC bibliography of protocol tested teat dips.
|
MATERIALS AND METHODS |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONREFERENCES |
|---|
Sampling schedule.
The bacteriologic status of mammary quarters was determined at the initiation of the trial by collecting and culturing duplicate milk samples. A third sample was collected from specific quarters and cultured when results from the first 2 samples differed. Premilking preparation consisted of washing of teats with water, drying with individual paper towels, and forestripping prior to attachment of teat cups.
The herd is also sampled monthly throughout the year so that all cows have lifetime culture records for all lactations. When needed, this information is used to resolve discrepancies. Milk samples were collected and analyzed weekly during the trial. In instances in which either Staph. aureus or Strep. agalactiae was present for the first time in a previously uninfected quarter, a second sample was collected immediately and cultured. All quarters were eligible for new infections during the trial except 1) those infected with organisms of the same species as challenge organisms, and 2) those with deformed or abnormal teats. Quarters infected during the trial were treated by intramammary infusion of a cephapirin lactating cow product after confirmation of infection. Quarters were treated at each milking for 6 consecutive milkings. Once infected with a challenge organism that quarter was no longer eligible for infection with that organism, regardless of status after therapy.
Collection of milk samples.
Prior to sampling, 2 or 3 streams of foremilk were discarded. Each teat apex was scrubbed for several seconds with a cotton pledget moistened with 70% alcohol. Teats on the opposite side of the udder from the technician were sanitized first, and milk samples were collected in reverse order in sterile, snap-cap plastic tubes and refrigerated at 5°C.
Laboratory culture procedures.
Samples were mixed by shaking, and a 0.01-mL aliquot was streaked on trypticase soy agar (TSA) containing 5% bovine blood. Plates were incubated at 37°C for 48 h and examined to identify microorganisms present. An IMI was confirmed when 1) Staph. aureus or Strep. agalactiae was isolated from a clinical quarter; 2) 2 consecutive samples yielded 500 or more cfu/mL of the same pathogen; or 3) 3 consecutive samples contained 100 to 400 cfu/mL of the same pathogen.
Method of challenge exposure.
At the afternoon milking, Monday through Friday, the lower third of all 4 teats of each cow was experimentally exposed to a challenge suspension containing both Staph. aureus (Newbould 305) and Strep. agalactiae (McDonald 44) immediately after milking machines were removed. Within 5 to 10 s thereafter, 2 teats (right front, left rear) were dipped full length with teat dip; the remaining 2 teats served as undipped controls. Teats were exposed to challenge organisms to increase the number of pathogens impinging on the teat apex, resulting in an increased rate of IMI.
Preparation of challenge suspensions.
Stock suspensions of Staph. aureus (Newbould 305) were prepared weekly. The contents of one lyophilized vial of Staph. aureus were reconstituted in 6 mL of tryptic soy broth (TSB) and incubated at 37°C for 5 to 7 h. This culture was used to inoculate 500 mL of TSB, which was incubated on a gyratory shaker for 16 h. After incubation, bacterial cells were pelleted by centrifugation, washed twice with 0.1% proteosepeptone, and re-suspended to the original volume in proteosepeptone. Serial dilutions were made in proteosepeptone, and 0.1 mL was plated on TSA. Plates were incubated for 24 h at 37°C, and colonies were counted to ascertain the microbial concentration of the stock suspension. This suspension was stored at 5°C and used daily for 1 wk to prepare challenge suspensions of Staph. aureus (Hogan et al., 1990).
Streptococcus agalactiae (McDonald 44) cultures were prepared by thawing a frozen vial of Strep. agalactiae, and a 0.01-mL aliquot was streak plated onto each of 5 TSA plates. Plates were incubated at 37°C for 16 h and stored at 5°C to serve as stock cultures for a 1-wk period. Daily challenge suspensions of Strep. agalactiae were prepared by inoculating 6 mL of TSB with 6 colonies from a TSA stock plate. The 6-mL culture was incubated for 7 h at 37°C on a gyratory shaker. Specific aliquots of the culture were added to pasteurized milk as needed to adjust the concentration of Strep. agalactiae to approximately 5 x 107 cfu/mL.
An aliquot of the Staph. aureus stock suspension was added to the Strep. agalactiae suspension to obtain a concentration of approximately 5 x 107 cfu/mL of Staph. aureus. This bacterial suspension was taken immediately to the milking parlor to challenge teats during the afternoon milking. A plate count was conducted daily on challenge suspensions and recorded.
Statistical methods.
The Student t test was used to evaluate the statistical difference between the dipped and control quarter data. This procedure was described by Hogan et al. (1990). The statistical probability of difference in IMI between the control and dipped quarters is measured from the value of t.
 |
where x1 = number of new IMI in control quarters, x2 = number of new IMI in treated quarters, n1 = (number of control quarters)(days of exposure), n2 = (number of treated quarters)(days of exposure). Percentage reduction = 100[(x1/n1) – (x2/n2)]/(x1/n1). A teat dip is considered efficacious if the reduction is at least 40% (Foret et al., 2003).
Scoring of teat condition.
Characteristics of teat end and teat skin condition in dipped and control teats were scored immediately before the trial was initiated and at the conclusion of the trial to determine any effects of the teat dip products on the condition of teat ends and lateral teat skin. The teats were given a score of 1 to 5 using visual and tactile observation (Goldberg et al., 1994; Neijenhuis et al., 2004). See Table 1
for a description of the ordinal scale and results of the scoring.
|
|
RESULTS AND DISCUSSION |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONREFERENCES |
|---|
. A total of 17 new Staph. aureus IMI were confirmed; 15 in control quarters and 2 in dipped quarters. Nineteen new Strep. agalactiae IMI were confirmed; 14 in control quarters and 5 in dipped quarters. The teat dip reduced the infection rate for Staph. aureus 87.9% (P <0.001) and 66.5% for Strep. agalactiae (P <0.05). Teats were scored for chapping, cracks, and other forms of irritation, both prior to and at the end of the trial. There were no changes in teat end or teat skin characteristics during the trial (Table 1
).
|
Results indicate that this 0.1% product has sufficient germicidal activity to be efficacious in preventing new IMI. Iodine teat dips have been a mainstay of post dip teat antisepsis for many years. High concentrations of iodine in dips have raised concern of potential residues in milk, especially with the advent of premilking application of dips. New formulations and technologies have allowed a decrease in total iodine concentration while maintaining or enhancing bactericidal activity. The I-tech iodine technology has proven to be effective in maintaining iodine bactericidal activity at lowered iodine concentrations, thereby reducing the risk of residues.
Received for publication November 20, 2003. Accepted for publication March 23, 2004.
|
REFERENCES |
|---|
|
TOPABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTS AND DISCUSSIONREFERENCES |
|---|
This article has been cited by other articles:
|
|
 |
|
  K. E. Leslie, E. Vernooy, A. Bashiri, and R. T. Dingwell Efficacy of Two Hydrogen Peroxide Teat Disinfectants Against Staphylococcus aureus and Streptococcus agalactiae. J Dairy Sci, September 1, 2006; 89(9): 3696 - 3701. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
