1,721,138 research outputs found
How differential somatic cell counting can help in sustainable herd management.
No full textBovine mastitis is a major cause of economical losses in dairy production. Identification of
infected animals is often difficult, for the etiopathological aspects of the disease, and for the costs of
cyto-bacteriological exams. In the present study we explored the possibility of identifying diseased
animals using only cytological tests.
Milk was sampled from 184 quarters of 50 cows, in 3 herds, and submitted to somatic cell
counting and bacteriological analysis, according to NMC guidelines. Each sample was also
centrifuged, the cell pellet was spread on a slide, stained with May-Grünwald Giemsa, and
evaluated by light microscopy. Relative percentages of leukocytes and three ratios were calculated:
lymphocytes (L%), macrophages (M%), neutrophils (PMN%), and phagocytes per lymphocytes
(Ph/L), macrophages per neutrophils (M/PMN) and neutrophils per lymphocytes (PMN/L). The
ratios were normalized to natural logarithm. Receiver operating characteristic (ROC) curves were
generated for each percentage and ratio. Statistical analysis was performed using Student’s-t test.
Quarters were classified as healthy or diseased based on SCC and bacteriological results. Herd
B and C showed a low and high prevalence of Staphylococcus aureus infected quarters,
respectively, while herd A was free from contagious pathogens.
Differences between groups were significant (P<0.05) for all variables, except for M%.
Natural logarithm (PMN/L) and L% gave the best area under curve values (0.813 and 0.795,
respectively). The overall sensitivity was 82.7% (69.2%, 87.5% and 96.8% in herd A, B and C,
respectively), and the specificity was 63.9%. Based on the different etiologic agents in herd A, a
new ROC analysis for herds free of contagious pathogens was run for both Ln (PMN/L) and L%,
thereby achieving a sensitivity of 79.4%. In conclusion, differential cell count could be used as a
good screening method, reducing the number of bacteriological tests needed, and increasing the
income for farmers
Practical application of a tool to evaluate mastitis risk factors and costs in 25 Italian dairy herds
No full textA practical tool was developed to investigate mastitis risks and costs in dairy herd. This tool is based on a questionnaire and on random sampling of quarter milk. The questionnaire was developed to collect the data in an objective and rationale way, avoiding personal interpretation of data. The aim was to evaluate the different critical points within a dairy herd (i.e. milking, therapy, bedding hygiene) and to calculate mastitis cost by partial budget analysis. Random
sampling of quarter milk is based on epidemiological approach, to maximize the chance to identify prevalent pathogens.
Questionnaires and milk samples were collected in 25 Italian dairy herds during 2010. Data were analyzed to assess mastitis costs, bacteria and risk factors. The results showed that in each dairy herd a prevalent source of infections could be identified (contagious or environmental pathogens). More interestingly, the cost of mastitis showed very large
variations mostly due to the different protocols applied in each farm and not to the different pathogens identified. The tool developed showed to be practical and useful to identify prevalent pathogens and critical factors at herd level, and to
improve herd sustainability by applying more rational and efficient therapeutic protocols
Bovine mammary gland epithelial cells innate immune response to S. Aureus
No full textRecently, epithelial cells (EC) has been recognized as a major source of innate immune components useful to protect mammary gland from infections. A study was designed to investigate the response induced by different S.aureus strains on EC. Ten S.aureus isolated from subclinical mastitis cases in dairy cows of different herds were selected based on their genetic characteristics and antimicrobial susceptibility. A clonal cell line (BME-UV) established from udder primary epithelial cell synthesizing several milk components was used as an in vitro model. Previous studies showed that this cell line can express several cytokines and immune components when stimulated by bacteria or toxins. Bacteria count, lysozyme (LYZ) and NAGase (NAG) concentration were used to assess cellular response, while the strains were classified in two groups by TLR expression: high rate (HR) and low rate (LR).
As expected S.aureus growth both intracellularly and extracellularly. However, extracellular S.aureus showed similar curves when isolates expressing TLRs in high rate and in low rate were considered, while intracellular curves were different. Indeed, in this latter case LR isolates peaked at 10 h PI, then the concentration decreased, while increased around 2 logs in the HR group.
The results of the study confirmed the capability of EC to produce component of innate immunity. However the response was triggered only when bacteria concentration was over 0.5 log10 μg/ml. When LYZ concentration in relation to TLR expression was considered, data showed as extracellular LYZ increased more rapidly in HR than in LR isolates until 10h PI, when the two curves stated to overlap. Intracellular LYZ concentration showed to have a very similar pattern both in HR and LR groups. However, LYZ level were always higher in HR group when compared with LR one.
Extracellular NAG was always very low, while intracellular NAG concentrations were higher than extracellular ones, as expected. Also when TLR expression were considered, a similar pattern for both LR and HR isolates were observed, even if at different mean levels up 10 h PI. Then, the concentration decreased at intracellular level and increased extracellularly.
S.aureus to have different capability to induce innate immune response. However, these difference were influenced by the growth rate and by the site of infection (intracellular/extracellular). The production of innate immune parameters from EC in response to S.aureus infections suggest that these cells could be a target of choice in developing immune-modulators to be used to control bovine mastiti
Relationship between S.aureus gene pattern and dairy herd mastitis prevalence
No full textThe importance to evaluate Staphylococcus aureus virulence analysing the combination of virulence genes is largely recognised, and the recent availability of simplified microarray tools allows performing these analyses also in the dairy field. The combined availability of herd-specific S. aureus mastitis prevalence data, isolates from these herds, and microarray technology offered the opportunity to investigate the relationship between S. aureus genetic pattern and their prevalence among dairy herds. Eleven commercial dairy herds following a S. aureus control programme were enrolled in the study, and 33 S. aureus isolates were collected from these herds. Diagnostic DNA microarrays based on the array-tube platform were used for genotyping of staphylococcal DNA. The genetic analysis of the 157-genes microarray showed as only 19 genes were present in all the isolates considered, and among them the genes coding for the leukocidin subunits (LukF, LukS and LukY), haemolysins (hla, hld and an unnamed haemolysin) and enterotoxin X. Several genes considered in the arrays were absent in all the isolates, including the ones encoding the resistance to most of the antimicrobials, except for tetracycline. In our isolates, some agr alleles were never identified (B-III, C-III, D-III, C-IV and D-IV). The comparison of epidemiological data with the genetic pattern suggests that agr type II is associated to the most diffusive isolates, being recovered from the largest number of herds and with the highest frequency. Microarray technique showed to be a useful method to assess the characteristics of virulence of S. aureus isolated in dairy herds and to investigate the relationship with the prevalence of the microorganism. These results support previous evidence that specific gene patterns could be associated to S. aureus mastitis
Innate immune response of mammary gland epithelial cells to intracellular Staphylococcus aureus
No full textBackground. Non-specific (innate) immune
response plays a major role in defending udder from bacteria invasion. Innate soluble immune defenses are all involved in preventing bacteria adhesion, multiplication and in bacteria killing.
Recent investigations suggested that epithelial cells could have a large and important role as a source for soluble components of immune defenses's. Methods. Ten S.aureus isolates from subclinical mastitis cases in dairy cows of different herds were considered. These isolates
were characterized by different virulence genes patterns. A clonal cell line established from udder epithelial cells (BME-UV), synthesizing several milk components, was used as an in vitro model. Cell line was exposed to S.aureus and the intracellular and extracellular release of Lysozyme and NAGase were assessed from 4 h until 24 h by a fluorescence-based procedure on a microplate fluorimeter. Results. The
preliminary results of this study showed that
S.aureus strains invading epithelial cells elicited an immunological response with levels related to strain characteristics. The pattern of lysozyme concentration was time-dependent and showed an extracellular increase at 24h after exposure to S.aureus. Moreover, it was detectable intracellularly starting at 4h, but not in the surnatant before 24 h. NAGase is a glycosidase and showed a release pattern different from lysozyme, even if it is also considered a lysosomial enzyme. Its extracellular concentration increased at 24h, when cells showed dysfunction, but at cell level
it decreased over the 24 h. Conclusions. These data confirms that epithelial cells could play an important role in udder innate defenses. Moreover, they suggest that the release pattern of the two enzymes considered is different. Lysozyme is involved in antibacterial activity
and could be considered as a marker of
bacteria-induced inflammation. About NAGase,
it could be hypotesized that it is more a marker of cellular damage and an extracellular increase is a sign of cellular dysfunction and/or disruption rather than of inflammation
Epidemiological study of non-contagious intramammary infections in nine commercial dairy herds following a Staphylococcus aureus control programme
No full textChanges in prevalence in intramammary infection. by pathogen type. in herds applying a stringent contagious mastitis control programme was studied. Enrollment of 1651 lactating cows and collection of milk samples was made in this ancillary Study to a cohort study of the dynamics of mastitis prevalence after adoption of a strict contagious mastitis Control programme that targeted the elimination of mastitis caused by Staphylococcus aureus. Nine commercial dairies in Italy Were used. Aseptic collection of milk samples from all lactating cows Was performed at the time of enrollment, from all cows within 7-14 days of entering the lactating herd after the date of enrollment. and from all lactating cows at 2, 4, 7 10 and 14 months after the date of enrollment. Prevalence of intramammary infection by pathogen type was determined from culture of milk samples. Application of the strict contagious mastitis programme did not lead to an increased risk of noncontagious mastitis. The risk of coliform. environmental streptococcal and coagulase-negative staphylococcal intramammary infections decreased after adoption of the programme. The data reported herein indicate that the overall risk for any intramammary infections decreases with adoption of a strict contagious mastitis programme, and that such a programme therefore does not necessarily lead to an increase in environmental mastitis
Epidemiologic study of intramammary infections with Staphylococcus aureus during a control program in nine commercial dairy herds
No full textObjective-To determine the epidemiologic pattern of intramammary infections (IMIs) with Staphylococcus aureus during implementation of a control program in 9 commercial dairy herds.
Design-Cohort study.
Animals-1,651 lactating cows and 53,098 quarter milk samples.
Procedures-Nine herds located in different regions of Italy were enrolled. Control of S aureus infections followed the general principles of contagious mastitis control and was based on precise diagnostic procedures and strict control and segregation of infected cows. All lactating cows in each herd were tested, and those free of S aureus IMI were enrolled as the cohorts. Further additions to the cohort group were cows and heifers free of S aureus IMI, as determined from aseptically collected milk samples taken approximately 7 and 14 days after calving.
Results-After the ninth month of the program, incidence decreased to < 2 new IMIs/100 cow-months in 7 of the herds. At the end of the study, 8 of 9 herds had an incidence of less than or equal to 1 new IMI/100 cow-months. Heifers were most at risk of developing an IMI.
Conclusions and Clinical Relevance-Results suggest that control of S aureus IMIs can be achieved by use of a control program based on segregation and use of hygienic and therapeutic protocols. Analysis of incidence and identification of risk factors in a herd could avoid the possible shortcomings of the program, maximizing the probability of success
Beyond numbers : the numerous and informative patterns of immuno-staphylococcal dynamics
No full textTo evaluate new drugs, the immune system should be considered. Here we evaluated a proof-of-concept that uncovers bacterial-leukocyte interactions. Analyzing longitudinal leukocyte data from bovines infected with either methicillin-resistant (MRSA) or methicillin-susceptible (MSSA) Staphylococcus aureus, two methods were investigated: (i) an approach that assesses lymphocytes, monocytes, or neutrophils, separately, and (ii) a method that, using dimensionless indicators (products, ratios, or combinations derived from leukocyte data), explores the dynamics of leukocyte relationships in three-dimensional (3D) space and identifies data subsets of informative value.
The classic approach not always distinguished infected from non-infected cows. In contrast, the alternative approach differentiated noninfected from infected animals and distinguished early MRSA from early MSSA and late MRSA infections.
Discrimination was associated with the use of dimensionless indicators. When measured in 3D space, such indicators generated a very large number of combinations, which helped detect data subsets usually unobserved, such as non-overlapping infection-negative and -positive subsets, and several disease stages. The validity of such data subsets was determined with biologically interpretable data.
This graphic, pattern recognition-based information system included but did not depend on any one number or variable. Because it can detect functions (relationships that involve two or more elements), in real time, if shown reproducible, the analysis of complex hostmicrobial dynamics could be used to evaluate antimicrobials
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