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Streptococcus (S.) uberis is a causative agent for clinical and subclinical bovine mastitis which significance for the udder health has increased over the last decades. Molecular diagnosis methods revealed that S. uberis may be subdivided into many different varieties with different epidemiological properties. In addition, some varieties were reclassified as Streptococcus parauberis and Globicatella sanguinis. The present paper reviews S. uberis and its role in modern dairy farming. This pathogen is ubiquitous for which it is considered as environment- associated. Straw bedding and pasture, but also the bovine skin and digestive mucosae are typical localizations inhabited by S. uberis. Due to its capacity to persist within the mammary tissue, some infections may eventually turn cow-associated. In other cases, the infection is short, but in any case, there is a high risk of re-infection. Although many varieties remain susceptible to most antimicrobial agents, the problem for the dairy farm lies in the high rate of re-infection. This paper also reviews risk factors, therapies and measures to control S. uberis at farm level.
The control of clinical mastitis on dairy farms is an essential part of animal health management. Knowledge of the causative microorganisms, the cure rates achievable in the field and essential associated factors are crucial for proper control. The objectives of the present study were to characterize clinical mastitis cases in Germany and to analyze factors influencing cure rates and the recurrence rate. Milk samples of every clinical mastitis case occurring on 12 participating farms were examined cytomicrobiologically. Post-treatment quarter samples were taken after 14 and 21 days. Treatments were performed according to existing farm protocols. Of 2883 clinical mastitis cases, the most prevalent pathogens were Streptococcus (S.) uberis (20.2%) and coliforms (11.6%). In 35% of the milk samples, no bacteriological growth was detected. The overall bacteriological cure rate was 73.3%, while the cytological cure rate was 22.3%, the full cure rate 21.4% and the recurrence rate 18.8%. Regarding the pathogen distribution of severe mastitis, coliform bacteria were detected in 30.5% of the cases, whereas S. uberis was detected in 26.5% thereof. The results show that severe mastitis is caused almost as frequently by Gram-positive as by Gram-negative microorganisms. The low cytological cure rates show that the therapy needs to be further developed with regard to calming the inflammation. The obtained data can be very helpful in assessing internal mastitis scenarios and the effect of measures and therapies.
Streptococcus dysgalactiae is among the most important pathogens causing bovine mastitis. Unfortunately, there is presently a lack of clear knowledge about the mode of transmission — contagious or environmental — of this pathogen. To obtain more information on this, knowledge of the genetic diversity of the isolated microorganisms at the farm level can be useful. To observe the strain variety in different herds of cattle, isolates of Strep. dysgalactiae were collected from clinical mastitis samples at different farms, and the strains were typed using the pulsed-field gel electrophoresis (PFGE) method. Overall, we performed strain typing on 93 isolates from 16 farms in Germany and used an index to describe the degree of contagiosity of Strep. dysgalactiae at each farm. This index (CI) represents the number of isolates divided by the number of strains found in mastitis milk of clinical cases within a period of 14 months. The results differed between the farms. In one farm, all six Strep. dysgalactiae cases that occurred during the study period were caused by a single strain (CI = 6), while in another farm the six cases that occurred were caused by five different strains (CI = 1.2). All other farms fell between these two extremes. This indicates that Strep. dysgalactiae infections can occur via several routes of transmission. At the farm level, strain comparisons are necessary to determine the routes of transmission. Two strains were able to survive on the farm for a minimum of 14 months.
The aim of this study was to define the time-related period of intramammary infections and its relation to risk factors for intramammary infections and clinical mastitis at cow and quarter levels. In total, 269 German Holstein Frisian dairy cows on three farms in Northern and Eastern Germany were included in this study. Quarter milk samples were collected at dry-off, 3 ± 1 days after calving and 17 ± 3 days after calving, for cytomicrobiological examination. Risk factors at quarter- and cow-level associated with intramammary infections and clinical mastitis were recorded during the trial period. Data were analyzed using logistic regression procedures and odds ratios were calculated. Calving for the second time increased the odds of clinical mastitis during the first 100 days of lactation compared to cows calving for the third time or more. A high milk yield after calving was a risk factor for new infections, with environmental pathogens 17 ± 3 days postpartum. A body condition score after calving less than 3.5 was associated with a decreased risk of having an intra-mammary infection (IMI) with non-aureus staphylococci and coryneforms 3 ± 1 days postpartum and consistent body condition between dry-off and early lactation decreased the risk of intramammary infections after calving. The absence of a ring of hyperkeratosis at the teat apex shown at dry-off was associated with a lower risk of intramammary infections with environmental pathogens 17 ± 3 days postpartum. This study shows the important influence of the dry period and early lactation on intramammary infections and clinical mastitis postpartum in dairy cows. Udder quarters may have eliminated pathogens during the dry period in 43.6% of cases in this study. Additionally, new infections occurred during early lactation, so 5.1% more quarters were infected 17 ± 3 days compared to 3 ± 1 days postpartum. New infections can be traced to non-aureus staphylococci and Staphylococcus aureus from dry-off up until 3 ± 1 days postpartum, and to non-aureus staphylococci, Staphylococcus aureus and Streptococcus uberis, after calving. In total, 88.7% of the infected quarters showed new infections with another pathogen species 3 ± 1 days postpartum than at dry-off, and 89.2% of the quarters 17 ± 3 days postpartum than 3 ± 1 days postpartum. In conclusion, the early lactation has just as important an influence on intramammary infections postpartum in dairy cows as the dry period. There is the possibility that udder quarters eliminate pathogens during the early lactation, especially during the dry period. However, there is also the danger that new infections manifest, with a large proportion of new infections occurring after calving. Thus, additional control strategies are of great importance to prevent new infections occurring during early lactation as well as during the dry period to reduce negative effects on milk yield and culling hazards in dairy cows by minimizing the associated risk factors
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.
In order to reduce antimicrobial treatment and prevent environmental mastitis, the aim of the present study was to investigate associations between herd level factors and microbial load on teat ends with environmental mastitis pathogens. Quarterly farm visits of 31 dairy farms over a one-year period were used for statistical analysis. During each farm visit, teat-skin swabs, bedding and air samples were taken and management practices and herd parameters were documented. Total mesophilic bacteria, esculin-positive streptococci and coliform bacteria were examined in the laboratory procedures from teat skin and environmental samples. Esculin-positive streptococci and coliform bacteria on teat ends increased with high temperature–humidity indices (THI) in the barn during the spring and summer. Significantly more coliform bacteria on teat ends were found in herds with an increased percentage of normal or slightly rough teat ends. Cleaning cubicles more frequently, pre-cleaning teats before milking as well as post-dipping them after milking had a decreasing effect of teat-skin load with total mesophilic and coliform bacteria at the herd level. To conclude, teat-skin bacterial load with environmental pathogens is subject to fluctuations and can be influenced by aspects of farm hygiene.
The objective of this study was to investigate the occurrence of bacteremia in dairy cows with severe mastitis. Milk samples were collected from affected udder quarters, and corresponding blood samples were collected from dairy cows with severe mastitis at the time of diagnosis before any therapeutic measures were undertaken. The cultural detection of pathogens in blood classified a bacteremia. Further diagnostic tests were performed to provide evidence of bacteremia. This was realized by PCR with regard to S. aureus, E. coli and S. uberis and the Limulus test. Detection of culturable pathogens in the blood of cows with severe clinical mastitis was rare and occurred in only one of 70 (1.4%) cases. Overall, bacterial growth was detected in 53 of 70 (75.7%) milk samples. S. uberis (22/70), E. coli (12/70) and S. aureus (4/70) were the most frequently isolated pathogens from milk of cows with severe mastitis. PCR was performed in 38 of 70 (54.3%) blood samples. PCR was positive in eight of 38 cases. S. uberis was found most frequently in six blood samples (8.6%). E. coli was found on PCR in one blood sample (1.4%). S. aureus was identified in one blood sample (1.4%). When Coliforms were detected in the quarter milk sample, a Limulus test was performed in the corresponding blood sample. In three of 15 cases, the Limulus test was positive (4.3% of samples). Further studies are needed to investigate the occurrence of bacteremia in cows with severe mastitis in a higher population size.
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.
Staphylococcus aureus is recognized worldwide as one of the major agents of dairy cow intra-mammary infections. This microorganism can express a wide spectrum of pathogenic factors used to attach, colonize, invade and infect the host. The present study evaluated 120 isolates from eight different countries that were genotyped by RS-PCR and investigated for 26 different virulence factors to increase the knowledge on the circulating genetic lineages among the cow population with mastitis. New genotypes were observed for South African strains while for all the other countries new variants of existing genotypes were detected. For each country, a specific genotypic pattern was found. Among the virulence factors, fmtB, cna, clfA and leucocidins genes were the most frequent. The sea and sei genes were present in seven out of eight countries; seh showed high frequency in South American countries (Brazil, Colombia, Argentina), while sel was harboured especially in one Mediterranean country (Tunisia). The etb, seb and see genes were not detected in any of the isolates, while only two isolates were MRSA (Germany and Italy) confirming the low diffusion of methicillin resistance microorganism among bovine mastitis isolates. This work demonstrated the wide variety of S. aureus genotypes found in dairy cattle worldwide. This condition suggests that considering the region of interest might help to formulate strategies for reducing the infection spreading.
The objective of this study was to investigate the association between teat skin colonization and intramammary infection (IMI) with Staphylococcus aureus or Streptococcus agalactiae at the quarter level in herds with automatic milking systems. Milk and teat skin samples from 1,142 quarters were collected from 300 cows with somatic cell count >200,000 cells/mL from 8 herds positive for Strep. agalactiae. All milk and teat skin samples were cultured on calf blood agar and selective media. A subset of samples from 287 quarters was further analyzed using a PCR assay (Mastit4 PCR; DNA Diagnostic A/S, Risskov, Denmark). Bacterial culture detected Staph. aureus in 93 (8.1%) of the milk samples and 75 (6.6%) of the teat skin samples. Of these, 15 (1.3%) quarters were positive in both the teat skin and milk samples. Streptococcus agalactiae was cultured in 84 (7.4%) of the milk samples and 4 (0.35%) of the teat skin samples. Of these, 3 (0.26%) quarters were positive in both the teat skin and milk samples. The PCR detected Staph. aureus in 29 (10%) of the milk samples and 45 (16%) of the teat skin samples. Of these, 2 (0.7%) quarters were positive in both the teat skin and milk samples. Streptococcus agalactiae was detected in 40 (14%) of the milk samples and 51 (18%) of the teat skin samples. Of these, 16 (5.6%) quarters were positive in both the teat skin and milk samples. Logistic regression was used to investigate the association between teat skin colonization and IMI at the quarter level. Based on bacterial culture results, teat skin colonization with Staph. aureus resulted in 7.8 (95% confidence interval: 2.9; 20.6) times higher odds of Staph. aureus IMI, whereas herd was observed as a major confounder. However, results from the PCR analyses did not support this association. Streptococcus agalactiae was isolated from the teat skin with both PCR and bacterial culture, but the number of positive teat skin samples detected by culture was too low to proceed with further analysis. Based on the PCR results, Strep. agalactiae on teat skin resulted in 3.8 (1.4; 10.1) times higher odds of Strep. agalactiae IMI. Our results suggest that Staph. aureus and Strep. agalactiae on teat skin may be a risk factor for IMI with the same pathogens. Focus on proper teat skin hygiene is therefore recommended also in AMS.
