Noninferiority trial comparing a first-generation cephalosporin with a third-generation cephalosporin in the treatment of nonsevere clinical mastitis in dairy cows

Outcomes after treatment of nonsevere gram-negative clinical mastitis with ceftiofur hydrochloride for 2 or 5 days compared with negative control

A study was conducted at 3 commercial dairies in California to compare outcomes of treating nonsevere (mild and moderate) gram-negative (GN) clinical mastitis (CM) with intramammary (IMM) ceftiofur HCl (125 mg of ceftiofur HCl per tube) in either 2-d (SP2) or 5-d (SP5) treatment programs compared with nontreatment (CON). In addition, we contrasted results from cases classified as mild and moderate. Four hundred fifteen cases were included in the final dataset, including 135 CON, 133 SP2, and 147 SP5. Milk from quarters with CM was sampled for on-farm culture (OFC) to differentiate gram-positive (GP) and GN bacteria, with results known within 24 h. Those with GN infections were randomly assigned to experimental groups, while those with GP, mixed infections, and contaminated samples did not continue in the study and received standard farm therapy. For cows with GN infections, a sample was submitted for MALDI-TOF assay. Only nonsevere cases were enrolled, and all quarters yielded monocultures of GN species. Clinical scores were obtained 0, 1, 2, 3, 4, 5, 14, 21, and 28 ± 3 d relative to enrollment. Milk samples were collected from quarters 14, 21, and 28 ± 3 d after enrollment, and submitted for routine culture and, when appropriate, submitted to MALDI-TOF evaluation. For many response criteria, there were significant interactions between treatments and CM severity scores at the time of enrollment, with effectiveness of ceftiofur HCl treatment being more beneficial compared with CON as mastitis clinical severity increased. While most treatment responses were significant for animals with mild or moderate GN mastitis, the largest responses were noted among cows with moderate CM cases.

Selective treatment of nonsevere clinical mastitis does not adversely affect cure, somatic cell count, milk yield, recurrence, or culling: A systematic review and meta-analysis

Treatment of clinical mastitis (CM) contributes to antimicrobial use on dairy farms. Selective treatment of CM based on bacterial diagnosis can reduce antimicrobial use, as not all cases of CM will benefit from antimicrobial treatment, e.g., mild and moderate gram-negative infections. However, impacts of selective CM treatment on udder health and culling are not fully understood. A systematic search identified 13 studies that compared selective versus blanket CM treatment protocols. Reported outcomes were synthesized with random-effects models and presented as risk ratios or mean differences. Selective CM treatment protocol was not inferior to blanket CM treatment protocol for the outcome bacteriological cure. Noninferiority margins could not be established for the outcomes clinical cure, new intramammary infection, somatic cell count, milk yield, recurrence, or culling. However, no differences were detected between selective and blanket CM treatment protocols using traditional analyses, apart from a not clinically relevant increase in interval from treatment to clinical cure (0.4 d) in the selective group and higher proportion of clinical cure at 14 d in the selective group. The latter occurred in studies co-administering nonsteroidal anti-inflammatories only in the selective group. Bias could not be ruled out in most studies due to suboptimal randomization, although this would likely only affect subjective outcomes such as clinical cure. Hence, findings were supported by a high or moderate certainty of evidence for all outcome measures except clinical cure. In conclusion, this review supported the assertion that a selective CM treatment protocol can be adopted without adversely influencing bacteriological and clinical cure, somatic cell count, milk yield, and incidence of recurrence or culling.

Intramammary treatment using allogeneic pure platelet-rich plasma in cows with subclinical mastitis caused by Gram-positive bacteria

The aims of the study were (1) to compare the cure risk of intramammary treatment of pure platelet rich plasma (P-PRP) or cefquinome sulfate (CS) in cows with subclinical mastitis (SCM) caused by Gram-positive bacteria, evaluated via somatic cell count (SCC) and the microbiological analysis of milk; (2) to compare the inflammatory/anti-inflammatory response of mammary gland to both treatments through the analyses of interleukins (IL), interferon gamma (IFN-γ), and tumour necrosis factor alpha (TNF-α) in milk. A non-inferiority randomized clinical trial was conducted. The null hypothesis was that cure risk in the experimental group (P-PRP) was inferior to the reference group (CS). A total of 103 cows were selected according to SCC and presence of Gram-positive bacteria, 49 cows were treated with CS and 54 cows were treated with P-PRP after determination of its cellular and molecular quality control. Cure was assessed by milk analyses at day 21 and 22 after treatment. Cows that remained with SCM were retreated at day 26, and cure assessed at day 47 and 48. Overall, bacteriological cure was observed in 16 cows (30%) of the P-PRP group, and 35 cows (71%) in CS group. Staphylococcus aureus cure risk was higher in CS group, but inconclusive for Streptococcus spp. The mean SCC increased in relation to time only in the P-PRP group. A direct relation between time and treatment for IL-1, IL-2, and IL-6 was observed, while no differences were observed for IL-4. Furthermore, IL-1 and IL-2 increased in cows treated twice in both groups. IL-8, IFN-γ, and TNF-α showed a significant interaction between time and treatment. IFN-γ concentration was lower in the P-PRP group compared to the CS on days 0 and 22. Leukocyte counts were lower in P-PRP when compared to whole blood. TGF-β1 and PF4 concentrations were higher in platelet lysates in comparison to P-PRGS and plasma. Moreover, PDGF-BB concentration was significantly higher in platelet lysates in comparison to plasma. Results obtained in this study demonstrate that SCM treated with PRP showed a lower rate of bacteriologic cure when compared to animals treated with CS.

Non-inferiority Trial Investigating the Efficacy of Non-steroidal Anti-inflammatory Drugs and Antimicrobial Treatment of Mild to Moderate Clinical Mastitis in Dairy Cows With Long-lasting Udder Diseases

To reduce ineffective antimicrobial usage in the treatment of non-severe clinical mastitis (CM) in cows with long-lasting udder diseases, non-antibiotic therapy with a non-steroidal anti-inflammatory drug (NSAID) was conducted and evaluated in a non-blinded, positively controlled, non-inferiority trial. Therefore, three-time systemic ketoprofen treatment at intervals of 24 h was evaluated in comparison with the reference treatment of solely antibiotic therapy in a field study on nine free-stall dairy farms located in Northern Germany. Cows with previous CM cases in current lactation and/or with long-lasting high somatic cell counts in preceding dairy herd improvement test days were randomly allocated to one of the two treatment groups in cases of mild to moderate CM. Quarter foremilk samples of the affected quarters were taken for cyto-bacteriological investigation before treatment as well as ~14 and 21 d after termination of therapy. Both treatment groups were compared regarding the bacteriological cure (BC) as the primary outcome. Clinical cure (CC) and no CM relapse within 60 d after the end of treatment (no R60) were chosen as secondary outcomes. The study resulted in the following outcomes: Streptococcus uberis was most frequently identified in microbiological culture from pre-treatment samples, followed by Staphylococcus aureus and Escherichia coli and other coliforms. No significant differences between the NSAID treatment and the reference treatment were detected regarding CC and CM recurrence (no R60). Although the sole ketoprofen therapy resulted in a numerically lower likelihood of BC, there were no significant differences to the reference treatment. Considering the selection criteria in this study, the results indicate that in mild to moderate CM cases exclusive treatment with ketoprofen may constitute an alternative to antimicrobial intramammary therapy, providing an opportunity for reduction of antibiotic usage. However, non-inferiority evaluations were inconclusive. Further investigations with a larger sample size are required to confirm the results and to make a distinct statement on non-inferiority.

What Is Success? A Narrative Review of Research Evaluating Outcomes of Antibiotics Used for Treatment of Clinical Mastitis

Treatment of clinical mastitis is the most common reason that antimicrobials are given to adult dairy cows and careful consideration of treatment protocols is necessary to ensure responsible antimicrobial stewardship. Clinical mastitis is caused by a variety of bacteria which stimulate an immune response that often results in spontaneous bacteriological clearance but can develop into long-term subclinical infections. Use of antimicrobial therapy is most beneficial for cases that are caused by pathogens that have a low rate of spontaneous cure but high rate of therapeutic cure. The purpose of this paper is to review studies that evaluated outcomes of antimicrobial therapy of clinical mastitis. Few studies reported differences in bacteriological cure among treatments and this outcome was rarely associated with clinical outcomes. Return to normal milk appearance was evaluated in most studies but demonstrated little variation and is not a reliable indicator of therapeutic success. Somatic cell count should be measured at quarter-level and will decline gradually after bacteriological clearance. Few researchers have evaluated important clinical outcomes such as post-treatment milk yield or culling. Few differences among approved antimicrobial therapies have been demonstrated and selection of antimicrobial therapy should consider the spectrum of activity relative to etiology.

Negatively controlled, randomized clinical trial comparing different antimicrobial interventions for treatment of clinical mastitis caused by gram-positive pathogens

The general objective of this study was to evaluate the effect of 3 intramammary antibiotic interventions using 2 commercially available antibiotics with narrow- or broad-spectrum activity on cure rates of clinical mastitis (CM) caused by gram-positive bacteria. We also compared the efficacy of treatment protocols, including a negative control, on outcomes at the cow and mammary quarter level. Before the onset of the study, 5,987 animals more than 12 mo old were randomly preassigned to 1 of 4 protocols in the event of gram-positive CM (except for Staphylococcus aureus and Trueperella pyogenes) during lactation: 3 infusions with 62.5 mg of amoxicillin performed 12 h apart (AMOX-L); 5 infusions once a day with 62.5 mg of amoxicillin (AMOX-EL); 5 infusions once a day with 125 mg of ceftiofur hydrochloride (CEFT-L); or negative control, no treatment performed until 5 d after diagnosis (NEG-CTR). Randomization was performed to preassign 90% of cows to one of the antibiotic protocols (30% in each group) and 10% to the negative control. A total of 696 quarter cases of CM met the inclusion criteria and were evaluated in the study. Quarter-level outcomes were assessed based on 5 milk samples collected up to 14 ± 3 d following enrollment (i.e., first day of treatment), whereas variables at the cow level [composite somatic cell count (SCC), milk production, and survival in the herd] were assessed up to 90 d after CM diagnosis. Streptococcus uberis, followed by Streptococcus dysgalactiae, were the main causes of gram-positive CM. Overall, clinical cure was higher for CEFT-L than for AMOX-EL, and no difference was observed between CEFT-L and AMOX-L. Likewise, no significant differences were detected on overall bacteriological cure, although some treatment effects were observed at the species level. Compared with antibiotic-treated groups, quarters assigned to NEG-CTR had higher counts of colony-forming units (cfu), 16S rRNA gene copy numbers, and Streptococcus relative abundance (RA) until d 5 after enrollment. Quarters treated with AMOX-L had higher cfu counts on d 5, 8, and 14 after enrollment compared with the other antibiotic protocols. In addition, the RA of Streptococcus spp. was higher on d 14 after enrollment for AMOX-treated quarters compared with the CEFT-L group. Linear score of SCC was higher for AMOX-treated cows than for CEFT-L in the first test day after CM. However, cows assigned to AMOX-L had higher milk production than those submitted to the AMOX-EL and CEFT-L protocols. In conclusion, the 2-d protocol with 3 intramammary infusions of amoxicillin (narrow-spectrum antimicrobial) had similar overall clinical and bacteriological cures as 5 administrations (once a day) with ceftiofur hydrochloride (wide spectrum). No significant difference was observed on CM recurrence and cow survival. However, quarters treated with 5-d protocols were more effective at reducing milk cfu counts than quarters in the AMOX-L protocol. In addition, lower Streptococcus spp. RA was observed in ceftiofur-treated quarters compared with the amoxicillin protocols at d 14 after CM diagnosis. Based on results of microbiome and bacterial load (quantitative PCR and cfu count) up to 5 d after CM diagnosis, antibiotic use remains an indispensable strategy for treatment of CM caused by gram-positive bacteria.

Critically important antimicrobials are generally not needed to treat nonsevere clinical mastitis in lactating dairy cows: Results from a network meta-analysis

There is ongoing debate regarding whether critically important antimicrobials (CIA) should be used to treat infections in food-producing animals. In this systematic review, we determined whether CIA and non-CIA have comparable efficacy to treat nonsevere bovine clinical mastitis caused by the most commonly reported bacteria that cause mastitis worldwide. We screened CAB Abstracts, Web of Science, MEDLINE, Scopus, and PubMed for original epidemiological studies that assessed pathogen-specific bacteriological cure rates of antimicrobials used to treat nonsevere clinical mastitis in lactating dairy cows. Network models were fit using risk ratios of bacteriological cure as outcome. A total of 30 studies met inclusion criteria. Comparisons of cure rates demonstrated that CIA and non-CIA had comparable efficacy for treatment of nonsevere clinical mastitis in dairy cattle. Additionally, for cows with nonsevere clinical mastitis caused by Escherichia coli and Klebsiella spp., bacteriological cure rates were comparable for treated versus untreated cows; therefore, there was no evidence to justify treatment of these cases with CIA. Our findings supported that CIA in general are not necessary for treating nonsevere clinical mastitis in dairy cattle, the disease that accounts for the majority of antimicrobial usage in dairy herds worldwide. Furthermore, our findings support initiatives to reduce or eliminate use of CIA in dairy herds.

Efficacy of cefquinome and a combination of cloxacillin and ampicillin for treatment of dairy cows with Streptococcus agalactiae subclinical mastitis

A randomized clinical trial was conducted to assess efficacy of intramammary cloxacillin and ampicillin (CLOXIMM), intramammary cefquinome (CEFIMM), and intramuscular cefquinome (CEFIM) to treat Streptococcus agalactiae intramammary infections (Trial 1). Subsequently, two treatment groups were extended to assess whether CLOXIMM was not inferior to CEFIMM (Trial 2). Nine farms were included in the study. Milk samples were collected from all quarters of all lactating cows for microbiological identification of S. agalactiae. Positive cows were randomly allocated into four groups: CLOXIMM, CEFIMM, CEFIM, or negative control (CONTROL). Study outcomes were bacteriological cure at 14 (CURE14), 21 (CURE21), and 14 and 21 (CURE1421) days after treatment onset, and somatic cell count. Logistic regression was used to estimate the odds of cure between each treatment and CONTROL. Non-inferiority analysis was performed considering a one-sided 95% confidence interval (CI) and non-inferiority margins (Δ) of 0.10, 0.15, 0.20, and 0.25. Adjusted S. agalactiae bacteriological cure for CLOXIMM, CEFIMM, CEFIM, and CONTROL was 86, 98, 55, and 25% at day 14; 82, 93, 52, and 0% at day 21; and 82, 92, 40, and 0% at days 14 and 21, respectively. Treatment with CLOXIMM and CEFIMM resulted in greater bacteriological cure rates, as compared with CEFIM or CONTROL, which does not justify the use of CEFIM in S. agalactiae eradication programs. The CURE14 difference between CEFIMM and CLOXIMM was of 12.1 percentage points (95% CI: 0.056–0.184). CLOXIMM was considered not inferior to CEFIMM for Δ = 0.20 or 0.25 and inconclusive for Δ = 0.10 or 0.15. Thus, it should be pondered by veterinarians whether an expected 12.1 (5.6–18.4) percentage points increase in cure rate would justify the use of a fourth-generation cephalosporin, as opposed to a combination of traditional IMM drugs (cloxacillin and ampicillin) to treat S. agalactiae subclinical mastitis.

Use of Rapid Culture Systems to Guide Clinical Mastitis Treatment Decisions

The selective treatment of clinical mastitis based on culture results can reduce antibiotic use by more than 50% without sacrificing treatment efficacy. Local laboratories reporting results in a 24-hour period, or adoption of on-farm milk culture systems, allow producers to make strategic treatment decisions. On-farm culture systems are most reliable when used to classify infections in broad diagnostic categories such as no growth, gram-positive, or gram-negative growth. Diagnostic accuracy is crucial for on-farm culture systems to be efficacious and economically advantageous. Quality assurance is necessary for the success of on-farm culture systems.

Factors associated with microbiological and clinical cure of mastitis in dairy cows

ABSTRACT 709 clinical mastitis cases were analyzed and treated with antimicrobial combination cephalexin-neomycin and the anti-inflammatory prednisolone. A sample of milk was collected to perform a microbiological culture before starting the treatment and 14 days later. Somatic cell count (SCC) was obtained from samples collected on the day of the clinical case (D0), 14 days after (D14) and 28 days after (D28). Of the total, 435 (61.4%) at the D0 exhibited growth of microorganisms. Of the isolated agents, 365 (84%) were Gram-positive, and 66 (16%) were Gram-negative. A clinical cure was achieved in 63% of cases. Bacteriological cure occurred in 75% of cases. Only at D28 after the clinical case a significant SCC reduction was verified. The logistic regression for clinical cure showed significant effects for days in milk and parity (P< 0.05). For bacteriological cure, there were significant effects of Log (SCC) D0; clinical cure and quarter affected (P< 0.05). In the principal component analysis, the Temperature-Humidity Index was associated with reduced clinical cure of clinical mastitis cases.

Antimicrobial resistance in non-aureus staphylococci isolated from milk is associated with systemic but not intramammary administration of antimicrobials in dairy cattle

Non-aureus staphylococci (NAS) are the bacteria most frequently isolated from bovine milk. Objectives of this study were to determine herd-level associations between antimicrobial use (AMU) and prevalence of antimicrobial resistance (AMR) and antimicrobial resistance genes in NAS according to antimicrobials and routes of administration. The AMR profile was determined using a micro-broth dilution method against a panel of 23 antimicrobials for 1,702 NAS isolates obtained from 89 herds. A subset of these isolates (n = 405) was submitted to whole-genome sequencing, and the presence of AMR genes was determined using data from 4 databases. Antimicrobial use was determined for all herds using an inventory of empty drug containers and quantified for each antimicrobial as the number of antimicrobial daily doses administered. Generalized linear models were used to estimate antimicrobial and route-specific associations between AMR in NAS and AMU. Prevalence of multidrug resistance in NAS was associated with systemic use of antimicrobials. Estimated relative risk associated with a 1-unit increase in antimicrobial daily doses per cow-year administered systemically was 1.28. No association was present with either intramammary or intrauterine use. Three drug classes, all of high or very high importance for human medicine, were associated with drug-specific AMR when administered systemically: penicillins, third-generation cephalosporins, and macrolides. Prevalence of tet, erm, and bla_ARL genes in NAS was higher in herds that used more tetracyclines, macrolides, and third-generation cephalosporins, respectively. No association between drug-specific AMU and prevalence of blaZ, mphC, and msrA was identified, irrespective of route of administration. The either weak or nonexistent association between AMR and antimicrobials administered intramammarily suggest that a decrease in AMR of NAS following implementation of selective dry cow therapy would be minimal in comparison to reduced use of systemic antimicrobials.

Use of Preservative Agents and Antibiotics for Increased Poliovirus Survival on Positively Charged Filters

Environmental surveillance of poliovirus (PV) and other non-enveloped viruses can help identify silent circulation and is necessary to certify eradication. The bag-mediated filtration system is an efficient method to filter large volumes of environmental waters at field sites for monitoring the presence of viruses. As filters may require long transit times to off-site laboratories for processing, viral inactivation or overgrowth of bacteria and fungi can interfere with virus detection and quantification (Miki and Jacquet in Aquatic Microb Ecol 51(2):195-208, 2008). To evaluate virus survival over time on ViroCap^™ filters, the filters were seeded with PV type 1 (PV1) and/or MS2 and then dosed with preservatives or antibiotics prior to storage and elution. These filters were stored at various temperatures and time periods, and then eluted for PV1 and MS2 recovery quantification. Filters dosed with the preservative combination of 2% sodium benzoate and 0.2% calcium propionate had increased virus survival over time when stored at 25 °C, compared to samples stored at 25 °C with no preservatives. While elution within 24 h of filtration is recommended, if storage or shipping is required then this preservative mixture can help preserve sample integrity. Addition of an antibiotic cocktail containing cephapirin, gentamicin, and Proclin^™ 300 increased recovery after storage at 4 and 25 °C, when compared to storage with no antibiotics. The antibiotic cocktail can aid sample preservation if access to appropriate antibiotics storage is available and sample cold chain is unreliable. This study demonstrated that the use of preservatives or antibiotics is a simple, cost-effective method to improve virus detection from ViroCap cartridge filters over time.

An update on environmental mastitis: Challenging perceptions

Environmental mastitis is the most common and costly form of mastitis in modern dairy herds where contagious transmission of intramammary pathogens is controlled through implementation of standard mastitis prevention programmes. Environmental mastitis can be caused by a wide range of bacterial species, and binary classification of species as contagious or environmental is misleading, particularly for Staphylococcus aureus, Streptococcus uberis and other streptococcal species, including Streptococcus agalactiae. Bovine faeces, the indoor environment and used pasture are major sources of mastitis pathogens, including Escherichia coli and S. uberis. A faeco-oral transmission cycle may perpetuate and amplify the presence of such pathogens, including Klebsiella pneumoniae and S. agalactiae. Because of societal pressure to reduce reliance on antimicrobials as tools for mastitis control, management of environmental mastitis will increasingly need to be based on prevention. This requires a reduction in environmental exposure through bedding, pasture and pre-milking management and enhancement of the host response to bacterial challenge. Efficacious vaccines are available to reduce the impact of coliform mastitis, but vaccine development for gram-positive mastitis has not progressed beyond the "promising" stage for decades. Improved diagnostic tools to identify causative agents and transmission patterns may contribute to targeted use of antimicrobials and intervention measures. The most important tool for improved uptake of known mastitis prevention measures is communication. Development of better technical or biological tools for management of environmental mastitis must be accompanied by development of appropriate incentives and communication strategies for farmers and veterinarians, who may be confronted with government-mandated antimicrobial use targets if voluntary reduction is not implemented.

Efficacy assessment of an intramammary treatment with a new recrystallized enrofloxacin vs ceftiofur and parenteral enrofloxacin in dairy cows with nonsevere clinical mastitis

A recrystallized form of enrofloxacin as dehydrate-HCl (enro-C) was assessed for bacteriological and clinical cure efficacies in Holstein-Friesian cows affected of nonsevere clinical mastitis. Treatments were enro-C_susp (n = 81), treated with a pharmaceutical suspension of enro-C/quarter; group enro-C_pd (n = 80) treated as above, but using enro-C powder suspended in water; group CF (n = 65), treated with ceftiofur HCl/quarter; and group enro_R (n = 66), treated with standard enrofloxacin solution (5 mg/kg, intramuscular). Cows had a mean milk production of 31 L/day and were 2-3 lactational periods old. Treatments were administered every 24 hr for 3 days. Groups treated with enro-C exhibited statistically significant (p > .05) better clinical cure as compared to groups treated with CF or enro_R (95.06%, 96.25%, 67.79%, and 57.55%, for enro-C_susp , enro-C_pd , CF, and enro_R , respectively). In contrast, probability of bacteriological cure was not statistically different among treatments. Yet, the outstanding clinical and bacteriological cure rates obtained for enro-C for nonsevere cases of mastitis is superior to previously reported data for parenteral enrofloxacin and other antibacterial-intramammary treatments. Impact of using enro-C on the rate and pattern of bacterial resistance, somatic cell counts and milk electric conductivity, must be studied. Also, the use of enro-C for complicated cases of mastitis should be studied and milk withdrawal times must be accurately established.

Noninferiority trial investigating the efficacy of a nonantibiotic intramammary therapy in the treatment of mild-to-moderate clinical mastitis in dairy cows with longer lasting udder diseases

A nonblinded, positively controlled, noninferiority trial was conducted to evaluate the efficacy of an alternative, nonantibiotic therapy with Masti Veyxym^® to reduce ineffective antibiotic usage in the treatment of nonsevere clinical mastitis (CM) in cows with longer lasting udder diseases. The solely intramammary treatment with Masti Veyxym^® (three applications, 12 hr apart) and the combined treatment with Masti Veyxym^® and antibiotics as usual on the farm according to label of the respective product were compared with the reference treatment of solely antibiotic therapy. The matched field study was conducted on eight free-stall dairy farms located in Eastern Germany. Cases of mild-to-moderate CM in cows with longer lasting high somatic cell counts in preceding dairy herd improvement test days and with previous CM cases in current lactation were randomly allocated to one of the three treatment groups. A foremilk sample of the affected quarter was taken before treatment and again approximately 14 days and 21 days after the end of therapy for cyto-bacteriological examination. Primary outcomes were clinical cure (CC) and no CM recurrence within 60 days after the end of treatment (no R60). Bacteriological cure (BC) and quarter somatic cell count (QSCC) cure were chosen as secondary outcomes although low probabilities of BC and QSCC cure for selected cows were expected. The study resulted in the following findings: the pathogens mostly cultured from pretreatment samples were Streptococcus uberis, followed by Staphylococcus aureus and coagulase-negative staphylococci. There were no significant differences between the two test treatments in comparison with the reference treatment regarding all outcome variables. The sole therapy with Masti Veyxym^® resulted in a numerically lower likelihood of BC without significant differences to the reference treatment. The combined therapy group showed a numerically higher nonrecurrence rate than the two other treatment groups and noninferiority compared to the reference treatment was proven. Having regard to the selection criteria of cows in this study, the findings indicated that sole treatment with Masti Veyxym^® in nonsevere CM cases may constitute an alternative therapy to reduce antibiotics. However, noninferiority evaluations were mostly inconclusive. Further investigations with a larger sample size are required to confirm the results and to make a clear statement on noninferiority.

Longitudinal metagenomic profiling of bovine milk to assess the impact of intramammary treatment using a third-generation cephalosporin

Antimicrobial usage in food animals has a direct impact on human health, and approximately 80% of the antibiotics prescribed in the dairy industry are used to treat bovine mastitis. Here we provide a longitudinal description of the changes in the microbiome of milk that are associated with mastitis and antimicrobial therapy. Next-generation sequencing, 16 S rRNA gene quantitative real-time PCR, and aerobic culturing were applied to assess the effect of disease and antibiotic therapy on the milk microbiome. Cows diagnosed with clinical mastitis associated with Gram-negative pathogens or negative aerobic culture were randomly allocated into 5 days of Ceftiofur intramammary treatment or remained as untreated controls. Serial milk samples were collected from the affected quarter and the ipsilateral healthy quarter of the same animal. Milk from the mastitic quarter had a higher bacterial load and reduced microbial diversity compared to healthy milk. Resolution of the disease was accompanied by increases in diversity indexes and a decrease in pathogen relative abundance. Escherichia coli-associated mastitic milk samples had a remarkably distinct bacterial profile, dominated by Enterobacteriaceae, when compared to healthy milk. However, no differences were observed in culture-negative mastitis samples when compared to healthy milk. Antimicrobial treatment had no significant effect on clinical cure, bacteriological cure, pathogen clearance rate or bacterial load.

The value of pathogen information in treating clinical mastitis

The objective of this study was to determine the economic value of obtaining timely and more accurate clinical mastitis (CM) test results for optimal treatment of cows. Typically CM is first identified when the farmer observes recognisable outward signs. Further information of whether the pathogen causing CM is Gram-positive, Gram-negative or other (including no growth) can be determined by using on-farm culture methods. The most detailed level of information for mastitis diagnostics is obtainable by sending milk samples for culture to an external laboratory. Knowing the exact pathogen permits the treatment method to be specifically targeted to the causation pathogen, resulting in less discarded milk. The disadvantages are the additional waiting time to receive test results, which delays treating cows, and the cost of the culture test. Net returns per year (NR) for various levels of information were estimated using a dynamic programming model. The Value of Information (VOI) was then calculated as the difference in NR using a specific level of information as compared to more detailed information on the CM causative agent. The highest VOI was observed where the farmer assumed the pathogen causing CM was the one with the highest incidence in the herd and no pathogen specific CM information was obtained. The VOI of pathogen specific information, compared with non-optimal treatment of Staphylococcus aureus where recurrence and spread occurred due to lack of treatment efficacy, was $20.43 when the same incorrect treatment was applied to recurrent cases, and $30.52 when recurrent cases were assumed to be the next highest incidence pathogen and treated accordingly. This indicates that negative consequences associated with choosing the wrong CM treatment can make additional information cost-effective if pathogen identification is assessed at the generic information level and if the pathogen can spread to other cows if not treated appropriately.

Randomized noninferiority trial comparing 2 commercial intramammary antibiotics for the treatment of nonsevere clinical mastitis in dairy cows

The purpose was to evaluate 2 intramammary treatments for mild-to-moderate cases of clinical mastitis in a noninferiority comparison. Noninferiority trials are intended to show whether a given treatment, hetacillin potassium, has at least comparable efficacy as the reference treatment, ceftiofur hydrochloride. Treatments can be deemed inferior to the reference treatment by an amount less than the margin of noninferiority, or inconclusive if the confidence interval crosses the margin of noninferiority. Cows with clinical mastitis from 6 farms were considered for enrollment. Using a randomized design, cows with mild or moderate mastitis in 1 quarter were assigned to on-label treatment with either ceftiofur or hetacillin. A total of 596 cows met the criteria needed for continued enrollment. Treatment distribution resulted in 309 cows in the ceftiofur group and 287 cows in the hetacillin group. Mixed regression analysis was performed for the following outcomes: bacteriological cure, pathogen cure, clinical cure, postevent milk production and linear score, and survival to d 30 and 60. Cox proportional hazards analysis was used to describe treatment effect on survival and mastitis risks. Bacteriological cure, defined as absence of causative organism in samples retrieved at d 14 and 21 postmastitis, was similar between groups. No significant statistical differences were found in cure risk, and noninferiority of hetacillin relative to ceftiofur for bacteriological cure was conclusive (hetacillin=67%, ceftiofur=72%). Absence of a pathogen on both follow-up samples designated a cow as a pathogen cure. Pathogen cure was similar between treatment groups and noninferiority of hetacillin relative to ceftiofur was shown (hetacillin=35%, ceftiofur=32%). Clinical cure (hetacillin=68%, ceftiofur=64%), postevent milk production (hetacillin=37.0kg, ceftiofur=38.2kg), and linear scores (hetacillin=3.4, ceftiofur=3.1) were also not statistically different between treatment groups. Noninferiority of hetacillin relative to ceftiofur was shown for survival to d 30 and survival to d 60, whereas hetacillin was more likely to have a clinical cure than ceftiofur by d 4. No differences were seen between groups when Cox proportional hazards were performed, neither for exit from the herd in the 60 d following the event nor in the risk for a subsequent mastitis event. These findings can be used to develop farm-specific protocols for clinical mastitis treatment.

Randomized clinical trial comparing ceftiofur hydrochloride with a positive control protocol for intramammary treatment of nonsevere clinical mastitis in dairy cows

The objective of this study was to compare ceftiofur hydrochloride with a positive control protocol for intramammary treatment of nonsevere clinical mastitis in dairy cows. A total of 264 clinical mastitis cases on 11 commercial dairy farms were treated with intramammary infusions, once a day for 4 d using 1 of 2 treatments: (1) ceftiofur hydrochloride 125mg; or (2) control: tetracycline 200mg + neomycin 250mg + bacitracin 28mg + prednisolone 10mg. Streptococcus agalactiae was the most frequently isolated gram-positive pathogen from clinical mastitis, followed by Staphylococcus aureus. Klebsiella spp. and Escherichia coli were the most isolated gram-negative bacteria from clinical mastitis. No significant differences were observed between treatments regarding the overall clinical cure, bacteriological cure, and new infection. No effect of treatment regimen was observed when the bacterial group (gram-positive vs. gram-negative) was evaluated. The overall clinical cure was 0.79 for ceftiofur-treated cows and 0.74 for control-treated cows, whereas the overall bacteriological cure was 0.79 for ceftiofur-treated cows and 0.76 for control-treated cows. Furthermore, the new intramammary infection was 0.10 for cows treated with ceftiofur and 0.11 for cows treated with control. In conclusion, the use of intramammary ceftiofur hydrochloride for treatment of nonsevere clinical mastitis has similar efficacy as a treatment regimen with a combination of antimicrobial agents (tetracycline + neomycin + bacitracin).

Treatment of mastitis in cattle

The understanding of mastitis, its cause, and the rationale for treatment or nontreatment of mastitis under various circumstances continues to evolve. This article presents research-based evidence about the use or nonuse of drugs to treat mastitis. Nondrug factors involved in decision making about mastitis, including cow characteristics and the epidemiology of mastitis, are also briefly discussed. This article provides information that helps in the making of knowledgeable, evidence-based decisions about therapy for mastitis. Focus is primarily on the use of antimicrobial drugs.