Päivi J. Rajala-Schultz

Antimicrobial resistance and genotypic characterization of coagulase-negative staphylococci over the dry period

Coagulase-negative staphylococci (CNS) have become the most frequently isolated organisms from bovine intramammary infections in recent years. While antimicrobial resistance (AR) is not considered a major problem among mastitis pathogens, concerns over emerging AR in general are increasing worldwide. Little information exists about the association between AR and one of the most common mastitis control measures, antibiotic dry cow therapy. The primary objective of the current study was to determine the prevalence of AR in CNS isolated before and after antimicrobial dry cow therapy. An additional objective was to genotypically characterize selected CNS isolates using pulsed-field gel electrophoresis (PFGE), to assess diversity and persistence of organisms over the dry period. Resistance against 10 antimicrobials was determined using a broth microdilution method and compared between CNS isolates collected at dry-off and at calving and from cows treated or not treated with intramammary antimicrobial products at dry-off (752 cows in total). Results suggested that increasing age of a cow and dry cow treatment when combined with high milk somatic cell count at dry-off and positive clinical mastitis history, were associated with increased AR to most beta-lactam antimicrobials and sulfadimethoxine. PFGE results suggested considerable diversity among the tested isolates as well as some clusters within cows and herds. PFGE would be useful in distinguishing between potentially persisting infections and cures and reinfections with different CNS strains.

Anti-inflammatory and analgesic effects of intra-articular injection of triamcinolone acetonide, mepivacaine hydrochloride, or both on lipopolysaccharide-induced lameness in horses.

OBJECTIVEnTo assess analgesia, inflammation, potency, and duration of action associated with intra-articular injection of triamcinolone acetonide (TA), mepivacaine hydrochloride, or both in metacarpophalangeal (MCP) joints of horses with experimentally induced acute synovitis.nnnANIMALSn18 horses.nnnPROCEDURESnBoth forelimbs of each horse were injected with lipopolysaccharide (LPS) 3 times. After the first LPS injection, 1 forelimb of each horse was treated with intra-articular injection of mepivacaine (80 mg; n=6), TA (9 mg; 6), or mepivacaine with TA (same doses of each; 6) 12 hours after the initial LPS injection. Contralateral limbs served as control limbs. Joint pain was assessed via lameness score and measurements of vertical force peak and pain-free range of motion of the MCP joint. Periarticular edema was evaluated. Degree of synovial inflammation was determined via synovial fluid analysis for WBC count and total protein concentration. Samples of plasma and synovial fluid were analyzed for TA and mepivacaine concentrations.nnnRESULTSnEach injection of LPS induced lameness and joint inflammation. Mepivacaine effectively eliminated lameness within 45 minutes after injection, regardless of whether TA was also administered, whereas TA reduced lameness, edema, and concentration of synovial fluid protein after the second LPS injection, regardless of whether mepivacaine was also injected. Treatment with TA also induced higher WBC counts and mepivacaine concentrations in synovial fluid, compared with results for mepivacaine alone.nnnCONCLUSIONS AND CLINICAL RELEVANCEnResults suggested TA is a potent analgesic and anti-inflammatory medication for acute synovitis in horses and that simultaneous administration of mepivacaine does not alter the potency or duration of action of TA.

Association of milk yield and infection status at dry-off with intramammary infections at subsequent calving.

The dry period plays an important role in maintenance of udder health. Cows are most susceptible to intramammary infections (IMI) after dry-off and near parturition and drying-off procedures may affect the likelihood of IMI at calving. The objective of this study was to evaluate the association of milk yield and infection status at dry-off with the likelihood of IMI at calving by examining different drying-off methods. Cows (n=112) at the Ohio State University Waterman Dairy Teaching and Research Herd were randomly assigned to either an intermittent or a standard, twice-daily milking group 1 week prior to dry-off. All quarters of all cows in the herd were treated with an antibiotic dry-cow product after the last milking. Milk samples were collected 1 week prior to dry-off (pre-dry), on the day of dry-off, and within 3 d of parturition to determine infection status of the quarters. Association between IMI at calving and cumulative milk yield for the final week of lactation and drying-off method was examined using generalized estimation equations with logic link, accounting for potential confounders, such as pre-dry and dry-off infection status, and for the correlated data structure due to quarters clustered within cows. Intermittent milking significantly reduced milk yield at the end of lactation. Increasing cumulative milk yield during the last week of lactation was significantly associated with a greater probability of IMI at calving for quarters that were uninfected prior to dry-off: uninfected quarters of cows producing more than 115 kg during the last week of lactation were 7.1-times more likely to be infected at calving (P=0.0081) than uninfected quarters of cows producing less than 75 kg. Even though the overall cure rate over the dry period was relatively high at 84%, the odds of a quarter being infected at calving was 7.6- and 3.3-times higher if it was infected at dry-off with major pathogens (P<0.0001) or minor pathogens (P=0.028), respectively, compared with an uninfected quarter at dry-off. The results suggest that decreasing milk yield prior to dry-off may serve as an effective means to maintain good udder health in a herd.

The Effect of Ketoconazole on Whole Blood and Skin Ciclosporin Concentrations in Dogs

BACKGROUNDnCiclosporin (CSA) is approved for the treatment of canine atopic dermatitis. Ciclosporin is metabolized by liver cytochrome P450 enzymes, a process inhibited by ketoconazole (KTZ).nnnHYPOTHESIS/OBJECTIVESnThe aims of this study were to determine skin and blood CSA concentrations when CSA was administered alone at 5.0 (Treatment 1) or 2.5 mg/kg (Treatment 2) and when CSA was administered at 2.5 mg/kg concurrently with KTZ at 5 (Treatment 3) or 2.5 mg/kg (Treatment 4). We hypothesized that skin and blood CSA concentrations in Treatment 1 would not differ from those obtained with T3 or T4.nnnANIMALSnIn a randomized cross-over study, six healthy research dogs received each of the treatments (Treatment 1, 2, 3 and 4) once daily for 7 days.nnnMETHODSnAfter the first, fourth and seventh dose for each treatment, a peak and trough skin punch biopsy sample and whole blood sample were collected and analysed with high-performance liquid chromatography-tandem mass spectrometry. Data were analysed using a repeated measures approach with PROC MIXED in SAS. Pairwise comparisons were performed with least squares means and Tukey-Kramer adjustment for multiple comparisons.nnnRESULTSnMean blood CSA concentrations in Treatment 1 were not different from those in Treatment 2 or 4, but were less than in Treatment 3. Mean skin CSA concentrations in Treatment 1 were greater than in Treatment 2, not different from those in Treatment 4, and less than those in Treatment 3.nnnCONCLUSIONS AND CLINICAL IMPORTANCEnAdministration of CSA and KTZ concurrently at 2.5 mg/kg each may be as effective as CSA alone at 5.0 mg/kg for treatment of canine atopic dermatitis.

The effect of inoculum volume on the microbiologic detection of naturally occurring Staphylococcus aureus intramammary infections.

Currently no standard definitions for the diagnosis of Staphylococcus aureus intramammary infection (IMI) exist. As a result, criteria applied in research to diagnose S. aureus IMIs have varied making comparisons between published works difficult. The goal of the current study was to define the optimal inoculum volume used in the diagnosis of naturally occurring S. aureus IMIs. Microbiologic results from 2 field studies examining S. aureus IMIs were used to examine the effects of inoculum volume on the microbiologic detection of S. aureus. A total of 1,583 milk samples were included in the analysis, and the results of using a 0.01-ml and a 0.1-ml inoculum are presented. Using a 0.01-ml inoculum resulted in a sensitivity of 91% (95% confidence interval [CI]: 88.6–93%) and a specificity of 99.4% (95% CI: 98.6–99.8%). Using the larger 0.1-ml inoculum resulted in a sensitivity of 96.8% (95% CI: 95.2–97.9%) and a specificity of 99.3% (95% CI: 98.4–99.7%). All false-positive samples were from S. aureus–negative quarters in S. aureus–positive cows. There were no false-positive cultures from S. aureus–negative cows. Of the false-negative samples, the majority (77%) were from 6 of the 34 S. aureus–positive quarters. Results from the current study of naturally occurring S. aureus IMIs support the hypothesis that, when using quarter level milk samples, a S. aureus IMI is most accurately diagnosed using a 0.1-ml inoculum. Regardless of inoculum volume, a single quarter sample culture that is positive with S. aureus (≥1 colony-forming unit) is sufficient to diagnose a S. aureus IMI.

A new approach to teaching veterinary public health at the Ohio State University.

Public-health practitioners with expertise in the area of veterinary public health are expected to understand the prevention and control of zoonotic infectious diseases in both human and animal populations. This focus on multiple species is what makes the veterinary public health (VPH) official unique. The development of a new VPH specialization within the existing Master of Public Health (MPH) degree program at the Ohio State University represents a significant new collaboration between the College of Veterinary Medicine and the College of Public Health. The main objective of the VPH specialization is to educate and train professionals to provide them with the skills, knowledge, and resources necessary to protect and improve human health using a One Medicine approach. The program targets a population of students who will likely enter the professional veterinary medicine curriculum but have one year available to enhance their preparatory training in health sciences before beginning the program. A core series of VPH courses was initiated to complement the existing MPH course requirements. The program has been successful in attracting students from the primary target population, but it has also attracted students wanting the MPH as a terminal degree and veterinarians returning to school to expand their career options.