Efficacy of standard vs. extended intramammary cefquinome treatment of clinical mastitis in cows with persistent high somatic cell counts.

Extended duration of clinical mastitis (CM) treatment has been advocated, although results showing its higher efficacy compared with standard treatment are difficult to compare and seem conflicting. In a non-blinded, positively controlled clinical trial with systematic allocation, the efficacy of a standard, 1·5-d cefquinome treatment (ST), and an extended, 5-d intramammary cefquinome treatment (ET) were evaluated. The latter is frequently performed in cows with persistent high somatic cell count (SCC), expecting a better cure. Therefore, cows with CM immediately preceded by at least two consecutive monthly elevated SCC >200 000 cells/ml, were studied. The primary efficacy criteria were bacteriological cure (BC) and clinical cure (CC), while SCC cure was considered a secondary criterion of cure. Least square means of overall BC were not different after ET (79%, n=206) compared with ST (72%, n=203). ET, as compared with ST, improved BC of CM when caused by streptococci, specifically Streptococcus uberis. At day 1·5, only 13% of quarters showed CC, increasing significantly towards 60% at day 5, and 99% at day 14 and at day 21. No significant difference in CC was present between treatment groups. Overall SCC cure was low (22%) and not significantly different between treatment groups, but significantly higher for cases due to enterobacteriacae compared with staphylococci. In conclusion, ET with cefquinome of CM in cows with a persistent high SCC seems to be only indicated when caused by streptococci, mainly Str. uberis but shows no advantage when no information on bacteriological causes of mastitis is available. In our data, absence of CC directly after ST was not related to eventual BC.

Potential of ESBL-producing Escherichia coli selection in bovine feces after intramammary administration of first generation cephalosporins using in vitro experiments.

Selection and spread of Extended Spectrum Beta-Lactamase (ESBL) -producing Enterobacteriaceae within animal production systems and potential spillover to humans is a major concern. Intramammary treatment of dairy cows with first-generation cephalosporins is a common practice and potentially selects for ESBL-producing Enterobacteriaceae, although it is unknown whether this really occurs in the bovine fecal environment. We aimed to study the potential effects of intramammary application of cephapirin (CP) and cefalonium (CL) to select for ESBL-producing Escherichia coli in the intestinal content of treated dairy cows and in manure slurry, using in vitro competition experiments with ESBL and non-ESBL E. coli isolates. No selection of ESBL-producing E. coli was observed at or below concentrations of 0.8 µg/ml and 4.0 µg/ml in bovine feces for CP and CL, respectively, and at or below 8.0 µg/ml and 4.0 µg/ml, respectively, in manure slurry. We calculated that the maximum concentration of CP and CL after intramammary treatment with commercial products will not exceed 0.29 µg/ml in feces and 0.03 µg/ml in manure slurry. Therefore, the results of this study did not find evidence supporting the selection of ESBL-producing E. coli in bovine feces or in manure slurry after intramammary use of commercial CP or CL-containing products.

Genomic analysis of European bovine Staphylococcus aureus from clinical versus subclinical mastitis.

Intramammary infections (IMI) with Staphylococcus aureus are a common cause of bovine mastitis and can result in both clinical (CM) or subclinical mastitis (SCM). Although bacterial isolates of S. aureus differ in their virulence potential it is largely unclear which bacterial virulence factors are responsible for increased clinical severity. We performed a genome wide association study and used a generalized linear mixed model to investigate the correlation between gene carriage, lineage and clinical outcome of IMI in a collection of S. aureus isolates from cattle with CM (n = 125) and SCM (n = 151) from 11 European countries. An additional aim was to describe the genetic variation of bovine S. aureus in Europa. The dominant lineages in our collection were clonal complex (CC) 151 (81/276, 29.3%), CC97 (54/276, 19.6%), CC479 (32/276, 11.6%) and CC398 (19/276, 6.9%). Virulence and antimicrobial resistance (AMR) gene carriage was highly associated with CC. Among a selection of nine virulence and AMR genes, CC151, CC479 and CC133 carried more virulence genes than other CCs, and CC398 was associated with AMR gene carriage. Whereas CC151, CC97 were widespread in Europe, CC479, CC398 and CC8 were only found in specific countries. Compared to CC151, CC479 was associated with CM rather than SCM (OR 3.62; 95% CI 1.38-9.50) and the other CCs were not. Multiple genes were associated with CM, but due to the clustering within CC of carriage of these genes, it was not possible to differentiate between the effect of gene carriage and CC on clinical outcome of IMI. Nevertheless, this study demonstrates that characterization of S. aureus CC and virulence genes helps to predict the likelihood of the occurrence of CM following S. aureus IMI and highlights the potential benefit of diagnostics tools to identify S. aureus CC during bovine mastitis.

Use of partial budgeting to determine the economic benefits of antibiotic treatment of chronic subclinical mastitis caused by Streptococcus uberis or Streptococcus dysgalactiae.

The economic effect of lactational antibiotic treatment of chronic subclinical intramammary infections due to Streptococcus uberis or Streptococcus dysgalactiae was explored by means of partial budgeting. Effects at cow level and herd level were modelled, including prevention of clinical mastitis episodes and the prevention of transmission of infections. Input variables for our deterministic model were derived from literature or based on 2002/2003 dairy prices and farming conditions in The Netherlands. Sensitivity analysis was used to examine the effect of uncertainty around input variables or changes in price estimates. On farms where pathogen transmission was prevented through proper udder health management, 3-d antibiotic treatment during lactation resulted in an average net profit of euro+11.62 over no treatment while 8-d antibiotic treatment had an average negative net result of euro-21.83. Sensitivity analysis showed that profitability depends on the probability of treatment-induced cure, pathogen transmission rates, culling rate, retention pay-off, and costs of antibiotic treatment. Three-day antibiotic treatment of chronic subclinical streptococcal mastitis is economically profitable over a range of input values for cure probabilities, transmission rates and losses due to culling. In contrast, 8-d lactational treatment is only profitable for very valuable animals, on farms where the risk of pathogen transmission is high and/or when the farmer is likely to cull a high percentage of cows with subclinical mastitis. Because bacterial flora, cow characteristics and management differ widely between farms, the economic outcome of lactational treatment of chronic subclinical streptococcal mastitis may be highly farm-dependent.

Effect of penethamate hydriodide treatment on bacteriological cure, somatic cell count and milk production of cows and quarters with chronic subclinical Streptococcus uberis or Streptococcus dysgalactiae infection.

A randomized, controlled field trial was performed in The Netherlands to determine the therapeutic efficacy of parenteral penethamate hydriodide (Leocillin) against naturally occurring, chronic, streptococcal mastitis during lactation. Quarter milk samples were collected from subclinical cases of Streptococcus uberis or Streptococcus dysgalactiae mastitis to determine the effect of treatment on bacteriological cure and somatic cell count (SCC) at quarter level. A quarter was considered to be cured when the bacterial species, isolated prior to treatment, was not isolated from the quarter milk samples taken on days 10 and 20 post-treatment (bacteriological cure), or when a quarter milk SCC (QMSCC) was <250000 cells/ml on days 10 and 20 post-treatment (SCC cure). Longitudinal data analysis was performed to determine the effect of antibiotic therapy on SCC and milk yield at cow level. Bacteriological cure occurred in 59% of 29 treated quarters, while no cure was observed in any of the 21 untreated control quarters. Treatment resulted in a significant decrease in SCC at cow and quarter level in comparison with untreated controls. There was no significant effect of treatment on milk production. Antibacterial treatment of subclinical streptococcal infections during lactation also prevented clinical mastitis. Furthermore, the treatment may contribute to reduction of bulk milk SCC and to prevention of pathogen spread in dairy herds.