USO DE FERRAMENTA MOBILE NA AVALIAÇÃO DO BEM-ESTAR DE BOVINOS DE LEITE

Os elementos climáticos podem influenciar o desempenho animal de forma negativa, desta maneira deve-se atuar no sentido de minimizar seus efeitos, utilizando construções adequadas para abrigá-los. As diferenças climáticas entre o país de origem dos bovinos leiteiros e o Brasil impedem que as vacas expressem todo o seu potencial genético para a produção de leite em função do estresse térmico, especialmente durante o verão, onde observam-se altas temperaturas e umidades relativas. O objetivo desse trabalho foi utilizar a ferramenta mobile Orvalho® para cálculo de índices de conforto visando o bem-estar de vacas leiteiras. Foram coletadas variáveis ambientais no galpão de descanso das vacas após ordenha, tais como: Temperatura de bulbo seco (Tbs), Temperatura de globo negro (Tgn) e Umidade relativa do ar (UR). Após a coleta dos dados ambientais, foi calculado o índice de conforto térmico ITGU e ITU através do aplicativo Orvalho® para inferir o estado de estresse térmico dos animais. Como resultado observou-se que os valores apresentados estão dentro dos limites de conforto para bovinos de leite, com ITGU máximo de 72,03 e ITU máximo de 72,46. O app Orvalho® auxiliou de forma prática o cálculo dos índices estudados, demonstrando ser um recurso móvel útil para pequenas avaliações de condições térmicas.

Short communication: High incubation temperature in bovine mammary epithelial cells reduced the activity of the mTOR signaling pathway

Hyperthermia alters utilization of AA in protein synthesis and cell-signaling activity in bovine mammary cells. Essential AA and insulin regulate translation of proteins by controlling the activity of mammalian target of rapamycin (mTOR) signaling pathway. The objectives of this study were to evaluate (1) the effects of incubation temperature on the mTOR signaling pathway and transcription of AA transporters in a bovine mammary alveolar cell line (MAC-T) and (2) the combined effects of incubation temperature and insulin on the mTOR signaling pathway in this cell line. Cells were cultured in medium with 10% fetal bovine serum at 37°C and 5% CO₂. In experiment 1, cells were subjected to 37°C (control) or 41.5°C (high incubation temperature; HT) for 12 h. In experiment 2, cells were assigned to 1 of 4 treatments as a 2 × 2 factorial arrangement, including 2 cell culture temperatures (control and HT) and absence or presence of 1.0 μg/mL of insulin. Proteins were harvested and separated by gel electrophoresis. In experiment 1, gene expression of AA transporters (SLC1A1, SLC1A5, SLC3A2, SLC7A1, SLC7A5, and SLC36A1) were evaluated, and changes of ≥2 fold were deemed significantly different. In experiments 1 and 2, immunoblotting was used to identify total and site-specific phosphorylated forms of protein kinase B (Akt1; Ser473), p70 S6 kinase (S6K1; Thr389), ribosomal protein S6 (rpS6; Ser235/236), and eukaryotic elongation factor 2 (eEF2; Thr56). Phosphorylated and total forms of Akt1, S6K1, rpS6, and eEF2 were quantified and expressed as the ratio of phosphorylated to total protein. In experiment 1, HT resulted in a ≥2-fold increase expression of SLC1A1 and SLC3A2. High incubation temperature reduced the phosphorylated to total ratio of Akt1 and rpS6 and increased the phosphorylated to total ratio of eEF2. In experiment 2, we found no temperature by insulin interactions on phosphorylation state of the protein factors of interest. High incubation temperature reduced the phosphorylated to total ratio of Akt1. The addition of insulin increased the phosphorylated to total ratio of Akt1, S6K1, and rpS6. In summary, HT reduced the activity of the mTOR signaling pathway and increased the expression of AA transporters. High incubation temperature possibly reduced protein translation by reducing the mTOR signaling pathway activity in an effort to adapt to thermal stress. These results may help explain the direct effect of elevated temperature on AA metabolism and protein translation in heat-stressed animals.

Host-pathogen gene expression profiles during infection of primary bovine mammary epithelial cells with Escherichia coli strains associated with acute or persistent bovine mastitis

Escherichia coli intramammary infection (IMI) is often acute with local and systemic clinical manifestations that clear within 7 days. However, if not diagnosed early and treated, E. coli IMI could result in generalized systemic reaction and death. Persistent E. coli IMI is characterized by mild clinical manifestations followed by acute episodes of clinical mastitis during lactation. Factors responsible for pathogenesis of E. coli IMI and variation in clinical manifestations are not known. There are studies indicating that the outcome of E. coli IMI is mainly determined by cow factors. However, recent research demonstrated that virulence attributes of E. coli strains have significant impact on the outcome of E. coli IMI. The aims of this study were; (a) to compare gene expression profiles of PBMEC cocultured with strains of E. coli associated with acute or persistent IMI and; (b) to identify genes of E. coli induced during bacterial interaction with PBMEC. Utilizing cDNA we analyzed gene expression patterns of PBMEC cocultured with strains of E. coli using non-treated PBMEC as negative control. We evaluated also expression patterns of virulence associated genes of E. coli after co-culture with PBMEC using qRT-PCR. Our results showed that infection by both strains induced increased expression of pro-inflammatory cytokines, chemokines and innate immune response and apoptosis related genes. Our qRT-PCR results showed significant up-regulation of ler, eae, flic and iutA genes mainly in the strains of E. coli associated with persistent IMI. The pathogenesis and clinical severity of E. coli IMI may be determined by combined effects of host-pathogen factors.

pGh9:ISS1 transpositional mutations in Streptococcus uberis UT888 causes reduced bacterial adherence to and internalization into bovine mammary epithelial cells

Streptococcus uberis is an important mastitis pathogen that affects dairy cows worldwide. In spite of the economic impact caused by the high prevalence of S. uberis intramammary infections (IMI) in many well-managed dairy herds, pathogenic strategies and associated virulence factors of S. uberis are not well understood. It has been shown that S. uberis attaches to and internalizes into mammary epithelial cells and can survive inside cells for extended periods of time. We hypothesize that early attachment to and internalization into mammary epithelial cells is a critical step for the establishment of intramammary infection. The aim of this study is to identify and characterize chromosomally encoded virulence factors of S. uberis that allow early bacterial attachment to and internalization into mammary epithelial cells. A common approach used to identify virulence factors is by generating random insertion mutants that are defective in adherence to and internalization into mammary epithelial cells using pGh9:ISS1 mutagenesis system. A random insertion mutant library of S. uberis strain UT888 was created using a thermo-sensitive plasmid pGh9:ISS1 carrying ISS1 insertion sequence. Integration of the insertion sequence into the chromosome of these mutant clones was confirmed by PCR and Southern blot. Southern blot analysis of mutant clones also showed that insertional integration was random. Of 1000 random chromosomal insertion mutants of S. uberis strain UT888 screened, 32 had significantly reduced ability to adhere to and internalize into mammary epithelial cells. Chromosomal mapping of insertion sequence integration sites in some of these defective mutants showed integration into penicillin binding protein 2A (pbp2A), sensor histidine kinase, tetR family regulatory protein, phosphoribosylaminoimidazole carboxylase catalytic subunit (purE), lactose phosphotransferase, phosphoribosylamine glycine ligase (purD), and other genes involved in metabolic activities. These proteins may have a significant role in early bacterial colonization of the mammary gland during infection.

Presence of ISS1-like insertion sequence in wild type Streptococcus uberis strains isolated from cases of bovine mastitis

Streptococcus uberis is a major cause of environmental mastitis worldwide. In spite of significant economic losses caused by S. uberis in many well-managed dairy herds, virulence factors and mechanisms associated with the pathogenesis of S. uberis mastitis are not well known. The ability of S. uberis to attach to and internalize into mammary epithelial cells and subsequent intracellular survival enables it to avoid host defense mechanisms. Research to determine virulence factors responsible for these pathogenic strategies involved creating a random chromosomal mutant library of S. uberis strain UT888 using the thermosensitive plasmid pGh9:ISS1 mutagenesis system. During Southern blot analysis of the mutant library, an endogenous element similar to ISS1 insertion sequence of Lactococcus lactis was found. ISS1 is a transposable bacterial insertion sequence isolated originally from L. lactis and are small phenotypically cryptic sequences of DNA with a simple genetic organization and capable of inserting at multiple sites in a target molecule. They are flanked by inverted repeats; generally encode their own transposition functions. A total of 29 of 34 wild type strains of S. uberis evaluated were positive for ISS1 by Southern blot. Insertion of ISS1 might have a significant phenotypic and genotypic role in the S. uberis genome because of its ability to transpose within the genome.

Vaccination of dairy cows with recombinant Streptococcus uberis adhesion molecule induces antibodies that reduce adherence to and internalization of S. uberis into bovine mammary epithelial cells

Streptococcus uberis is an important environmental mastitis pathogen that causes subclinical and clinical mastitis in lactating and nonlactating cows and heifers throughout the world. Previous work from our laboratory suggests that S. uberis adhesion molecule (SUAM) is involved in S. uberis pathogenesis and may be an excellent target for vaccine development. The objective of this study was to evaluate the antibody response of cattle vaccinated with recombinant SUAM (rSUAM). Uninfected primiparous dairy cows (n=30) in late lactation were divided randomly into three groups of 10 cows each: control, 200 μg rSUAM, and 400 μg rSUAM. Cows in groups vaccinated with 200 μg and 400 μg rSUAM received an emulsion containing adjuvant, phosphate-buffered saline (PBS) and affinity purified rSUAM. Cows in the control group received an emulsion containing adjuvant and PBS. Cows were vaccinated subcutaneously in the neck region at drying off (D-0), 28 d after drying off (D+28) and within 7 d after calving. Serum was collected at D-0, D+28, at calving (C-0), calving vaccination (CV), and during early lactation (CV+14). Serum antibody responses were measured by an ELISA against rSUAM. Following the first vaccination a significant increase in anti-rSUAM antibodies was detected at D+28 in cows from groups vaccinated with 200 μg and 400 μg rSUAM when compared to the control group. This increase in anti-rSUAM antibodies continued following the second immunization at D+28; reaching the highest levels in the post-parturient sampling period (C0), after which antibodies appeared to plateau. S. uberis UT888 pretreated with several dilutions of heat-inactivated serum from cows vaccinated with rSUAM, affinity purified antibodies against rSUAM, and to a 17 amino acid long peptide from the N terminus of SUAM (pep-SUAM) were co-cultured with bovine mammary epithelial cells and adherence to and internalization of S. uberis into epithelial cells was measured. Compared to untreated controls, opsonization of two strains of S. uberis with sera from cows vaccinated with rSUAM, with affinity purified rSUAM antibodies, or with affinity purified pep-SUAM antibodies significantly reduced adherence to and internalization of this pathogen into bovine mammary epithelial cells. In conclusion, subcutaneous vaccination of dairy cows with rSUAM during physiological transitions of the mammary gland either from or to a state of active milk synthesis induced antibodies in serum and milk and these antibodies reduced adherence to and internalization of S. uberis into mammary epithelial cells under in vitro conditions. SUAM appears to be an excellent candidate for vaccine development.

Intracellular killing of mastitis pathogens by penethamate hydriodide following internalization into mammary epithelial cells

Penethamate hydriodide was highly effective in killing Streptococcus uberis, Streptococcus dysgalactiae subsp. dysgalactiae and Staphylococcus aureus that internalized mammary epithelial cells. At higher concentrations (32 microg/mL to 32 mg/mL), killing rates ranged from 85% to 100%. At lower concentrations (0.032 microg/mL to 3.2 microg/mL), killing rates ranged from 0 to 80%. Results of this proof-of-concept study demonstrated that: (1) penethamate hydriodide is capable of entering mammary epithelial cells and killing intracellular mastitis pathogens without affecting mammary epithelial cell viability, (2) the in vitro model used is capable of quantifying the fate of mastitis pathogens internalized into mammary epithelial cells, and (3) this in vitro model can be used to determine the effectiveness of antibiotics at killing bacteria within the cytoplasm of mammary epithelial cells.

Adherent and invasive Escherichia coli are associated with persistent bovine mastitis

Bovine mastitis caused by Escherichia coli has traditionally been viewed as a transient infection. However, E. coli can also cause clonal persistent intramammary infection (IMI) in dairy cows. In this study, we explored the possibility that E. coli strains associated with persistent IMI are better able to adhere to, invade, survive and replicate in cultured mammary epithelial cells (MAC-T) than transient strains, and examined their serotype, overall genotype, phylogenetic group, and the presence of known virulence genes. Both transient and persistent E. coli strains adhered to MAC-T cells, but persistent strains invaded MAC-T cells 2.6-63.5 times more than transient strains. Blocking the adhesin/invasin FimH with mannose diminished but did not eliminate adhesion and invasion of any strain. Cytoskeletal and protein kinase inhibitors cytochalasin D, colchicine, genistein and wortmannin dramatically reduced invasion of MAC-T cells by both strains. All of the persistent strains, but only one transient strain, were able to survive and replicate intracellularly in MAC-T cells over 48 h. Transient and persistent strains displayed heterogeneous serotypes and overall genotypes, but similar phylogeny (group A), and lacked virulence genes of invasive E. coli. We have found that E. coli strains associated with persistent IMI are better able to invade and replicate within cultured mammary epithelial cells than transient strains. The invasion process involves the host cytoskeleton and signaling cascades and is not FimH dependent. Our findings suggest that the invasion of mammary epithelial cells and intracellular survival play an important role in the pathogenesis of persistent E. coli mastitis.

Foodborne pathogens in milk and the dairy farm environment: food safety and public health implications

Milk and products derived from milk of dairy cows can harbor a variety of microorganisms and can be important sources of foodborne pathogens. The presence of foodborne pathogens in milk is due to direct contact with contaminated sources in the dairy farm environment and to excretion from the udder of an infected animal. Most milk is pasteurized, so why should the dairy industry be concerned about the microbial quality of bulk tank milk? There are several valid reasons, including (1) outbreaks of disease in humans have been traced to the consumption of unpasteurized milk and have also been traced back to pasteurized milk, (2) unpasteurized milk is consumed directly by dairy producers, farm employees, and their families, neighbors, and raw milk advocates, (3) unpasteurized milk is consumed directly by a large segment of the population via consumption of several types of cheeses manufactured from unpasteurized milk, (4) entry of foodborne pathogens via contaminated raw milk into dairy food processing plants can lead to persistence of these pathogens in biofilms, and subsequent contamination of processed milk products and exposure of consumers to pathogenic bacteria, (5) pasteurization may not destroy all foodborne pathogens in milk, and (6) inadequate or faulty pasteurization will not destroy all foodborne pathogens. Furthermore, pathogens such as Listeria monocytogenes can survive and thrive in post-pasteurization processing environments, thus leading to recontamination of dairy products. These pathways pose a risk to the consumer from direct exposure to foodborne pathogens present in unpasteurized dairy products as well as dairy products that become re-contaminated after pasteurization. The purpose of this communication is to review literature published on the prevalence of bacterial foodborne pathogens in milk and in the dairy environment, and to discuss public health and food safety issues associated with foodborne pathogens found in the dairy environment. Information presented supports the model in which the presence of pathogens depends on ingestion of contaminated feed followed by amplification in bovine hosts and fecal dissemination in the farm environment. The final outcome of this cycle is a constantly maintained reservoir of foodborne pathogens that can reach humans by direct contact, ingestion of raw contaminated milk or cheese, or contamination during the processing of milk products. Isolation of bacterial pathogens with similar biotypes from dairy farms and from outbreaks of human disease substantiates this hypothesis.

Effects of Induced Clinical Mastitis During Preovulation on Endocrine and Follicular Function

The objective of the study was to determine if experimentally induced clinical mastitis before ovulation resulted in alterations of endocrine function, follicular growth, or ovulation. On d 8 (estrus = d 0), cows were challenged (TRT; n = 19) with Streptococcus uberis or were not challenged (control; n = 14). Forty-eight hours after induction of luteal regression on d 12, blood samples were collected to determine estradiol-17beta, LH pulse frequency, and occurrence of the LH surge. Ovaries were scanned to monitor follicular growth and ovulation. Cows with clinical mastitis (n = 12) had elevated rectal temperatures, somatic cell counts, and mammary scores. Estrus and ovulation occurred in 4 of 12 clinically infected cows and in all control cows. Cows that were challenged but did not develop clinical mastitis (n = 5) displayed estrus and ovulated. Due to differences in expression of estrus, cows were further subdivided for analyses into 4 groups: control, TRT-EST (infected cows that displayed estrus; n = 4), TRT-NOEST (infected cows that did not display estrus; n = 8), and NOMAS (cows that were inoculated but did not develop mastitis; n = 4). Ovulation rate was 100% for CON, NOMAS, and TRT-EST compared with 0% for TRT-NOEST cows. Size of the ovulatory follicle ("presumed" ovulatory follicle in TRT-NOEST cows) was similar for all groups. Frequency of LH pulses was decreased in TRT-NOEST compared with CON, TRT-EST, and NO-MAS. Estradiol-17beta increased over time in CON, NO-MAS, and TRT-EST cows, but did not increase in TRT-NOEST cows. Cows with clinical mastitis may exhibit estrus and ovulate normally or have disruptions in normal physiology including decreased LH pulsatility, absence of an LH surge and estrous behavior, suppressed estradiol-17beta, and failure to ovulate.

Extended ceftiofur therapy for treatment of experimentally-induced Streptococcus uberis mastitis in lactating dairy cattle

Streptococcus uberis is an important cause of mastitis in dairy cows throughout the world, particularly during the dry period, the period around calving, and during early lactation. Strategies for controlling Strep. uberis mastitis are poorly defined and are currently inadequate. Objectives of the present study were to evaluate efficacy of ceftiofur, a new broad-spectrum cephalosporin antibiotic, for treatment of experimentally induced Strep. uberis intramammary infections (IMI) in lactating dairy cows during early lactation and to determine whether extended therapy regimens enhanced efficacy of ceftiofur. Efficacy of extended ceftiofur intramammary therapy regimens was investigated in 37 mammary quarters of 23 dairy cows that developed clinical mastitis following experimental infection with Strep. uberis during early lactation. Cows that developed clinical mastitis during the challenge period were allocated randomly to 3 groups representing 3 different ceftiofur treatment regimens: 2-d (n = 7 mammary quarters), 5-d (n = 16 mammary quarters), and 8-d (n = 14 mammary quarters) treatment regimens. For all groups, 125 mg of ceftiofur hydrochloride was administered via intramammary infusion. A bacteriological cure was defined as an experimentally infected quarter that was treated and was bacteriologically negative for the presence of Strep. uberis at 7, 14, 21, and 28 d posttreatment. Percentage of Strep. uberis IMI eliminated was 43, 88, and 100% for the 2-, 5-, and 8-d ceftiofur treatment regimens, respectively. Both the 5- and 8-d ceftiofur extended therapy treatment regimens had significantly higher bacterial cure rates than the standard 2-d ceftiofur treatment regimen. The bacterial cure rate of the 8-d ceftiofur extended therapy group was marginally better (P = 0.052) than the 5-d ceftiofur extended therapy group. Results of this study indicate that ceftiofur therapy was effective for eliminating Strep. uberis experimental IMI, and 5- and 8-d extended ceftiofur therapy regimens were more effective than the standard 2-d treatment.

Detection of Sorbitol-Negative and Sorbitol-Positive Shiga Toxin-ProducingEscherichia coli,Listeria monocytogenes,Campylobacter jejuni, andSalmonellaspp. in Dairy Farm Environmental Samples

Six visits were conducted to four dairy farms to collect swab, liquid, and solid dairy farm environmental samples (165 to 180/farm; 15 sample types). The objective of the study was to determine on-farm sources of Campylobacter jejuni, Salmonella spp., Listeria monocytogenes, and Shiga toxin-producing Escherichia coli (STEC), which might serve as reservoirs for transmission of pathogens. Samples were analyzed using mostly U.S. Food and Drug Administration's Bacteriological Analytical Manual protocols; however, Salmonella spp., L. monocytogenes and STEC were co-enriched in universal pre-enrichment broth. Campylobacter jejuni were enriched in Bolton broth containing Bolton broth supplement. Pathogens were isolated on agar media, typed biochemically, and confirmed using multiplex polymerase chain reaction protocols. Campylobacter jejuni, Salmonella spp., L. monocytogenes, Sorbitol-negative (SN)-STEC O157:H7, and sorbitol-positive (SP)-STEC, respectively, were isolated from 5.06%, 3.76%, 6.51%, 0.72%, and 17.3% of samples evaluated. Whereas other pathogens were isolated from all four farms, SN-STEC O157:H7 were isolated from only two farms. Diverse serotypes of SP-STEC including O157:H7, O26:H11, O111, and O103 were isolated. None of the five pathogen groups studied were isolated from bulk tank milk (BTM). Most pathogens (44.2%) were isolated directly from fecal samples. Bovine fecal samples, lagoon water, bedding, bird droppings, and rat intestinal contents constituted areas of major concern on dairy farms. Although in-line milk filters from two farms tested positive for Salmonella or L. monocytogenes, none of the pathogens were detected in the corresponding BTM samples. Good manure management practices, including control of feral animals, are critical in assuring dairy farm hygiene. Identification of on-farm pathogen reservoirs could aid with implementation of farm-specific pathogen reduction programs.

Dynamics of leukocytes and cytokines during experimentally induced Streptococcus uberis mastitis

Streptococcus uberis causes a significant proportion of clinical and subclinical intramammary infections (IMI) in lactating and non-lactating dairy cows. In spite of this, its pathogenesis is incompletely understood. A study was conducted to determine leukocyte and cytokine dynamics during experimentally induced S. uberis mastitis. Five Jersey and five Holstein cows were challenged via intramammary inoculation of S. uberis into two uninfected mammary glands. Sixteen of 20 challenged mammary glands developed clinical mastitis with peak clinical signs observed at 144 h. The number of S. uberis in milk increased (P<0.05) 48 h after challenge, in spite of an increase in milk somatic cells that began at 18 h (P<0.001) and remained elevated throughout the study. Increased tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta) and interleukin-8 (IL-8) in milk were detected 66 h after challenge (P<0.05). Peak TNF-alpha and IL-8 concentrations occurred 120 h after challenge and preceded peak clinical signs. Experimental S. uberis IMI induced local production of TNF-alpha, IL-1beta and IL-8, which may play a role in the pathogenesis of S. uberis mastitis. Other mediators may be involved in initial leukocyte recruitment to the mammary gland, since increases in milk somatic cells occurred earlier than cytokine production.

Molecular characterization of Salmonella spp. isolated from bulk tank milk and cull dairy cow fecal samples

The consumption of meat from cull dairy cows and of raw milk has been associated with foodborne salmonellosis. This survey was conducted to establish the prevalence of Salmonella in cull dairy cow fecal samples and bulk tank milk and to determine the proportion of Salmonella-positive dairy farms (n = 30) in east Tennessee. Food and Drug Administration bacteriological analytical protocols were generally used for Salmonella isolation. Primary enrichment was performed with lactose broth, and secondary enrichment was conducted with tetrathionate broth. Eosin methylene blue, hektoen enteric, xylose lysine desoxycholate, bismuth sulfite, and brilliant green (BG) were used as isolation agars. BG agars supplemented with individual antibiotics and/or sulfur compounds were also evaluated. Six of 268 (2.24%) bulk tank milk samples and 9 of 415 (2.17%) fecal samples from 7 of 30 (25.3%) dairy farms were Salmonella-positive. Most isolates (11 of 15) were obtained between September and December. Salmonella isolates were further characterized using polyvalent somatic O Salmonella antiserum, o-nitrophenyl-beta-D-galactopyranoside (ONPG), and Analytical Profile Index (API) 20E strips for Enterobacteriaceae. Serological evaluation of presumptive positive Salmonella isolates resulted in substantial numbers of false positives (41.2%). ONPG and API 20E tests enabled further biochemical distinction of the majority of Salmonella spp. from Salmonella Arizonae and closely related members of Enterobacteriaceae like Citrobacter youngae. Pulsed-field gel electrophoresis of SpeI-digested Salmonella DNA was used to subtype isolates. The isolates grouped into four clusters. The baseline information generated in this survey is being used to develop preharvest pathogen reduction programs on selected farms.

Prevalence and molecular characterization of Escherichia coli O157:H7 in bulk tank milk and fecal samples from cull cows: a 12-month survey of dairy farms in east Tennessee

A study on the prevalence of Escherichia coli O157:H7 was conducted on 30 dairy farms in east Tennessee between May 2000 and April 2001. This pathogen was isolated from 8 of 30 (26.7%) dairy farms at various sampling times. A total of 415 fecal samples from cull dairy cows and 268 bulk tank milk samples were analyzed. Overall, 10 of 683 (1.46%) samples (2 of 268 [0.75%] milk samples and 8 of 415 [1.93%] fecal samples) tested positive for E. coli O157:H7. Food and Drug Administration Bacteriological Analytical Manual protocols were used for the conventional isolation and confirmation of E. coli O157:H7. Samples were shake cultured (150 rpm) at 42 degrees C for 24 h in tryptic soy broth containing 2 mg of novobiocin per liter. White colonies isolated on cefixime-tellurite sorbitol MacConkey agar plates were evaluated for fluorescence on sorbitol MacConkey agar supplemented with 0.025 g of methylumbelliferyl-beta-D-glucuronide per liter. Nonfluorescing white colonies were biochemically typed and serologically confirmed. Multiplex polymerase chain reaction profiles of E. coli O157:H7 isolates indicated the presence of common virulence factors (Shiga toxin, enterohemolysin, and intimin) of Shiga toxin-producing E. coli, suggesting the potential human pathogenicity of bacterial isolates. Pulsed-field gel electrophoresis profiles of SpeI and XbaI restriction enzyme-digested genomic DNA were used to establish relatedness among bacterial isolates. Data from this study indicate that both cull dairy cows and bulk tank milk pose a potential hazard with regard to human foodborne illness. It is therefore imperative to develop on-farm and preharvest pathogen reduction programs to control the carriage of E. coli O157:H7 pathogens.

Binding of bovine lactoferrin to Streptococcus dysgalactiae subsp. dysgalactiae isolated from cows with mastitis

Three strains of Streptococcus dysgalactiae subsp. dysgalactiae (UT516, UT519, ATCC 27957) were used to determine if bovine lactoferrin (Lf) binds to bacterial cells by biotin avidin binding assay (BABA), enzyme-linked immunosorbent assay (ELISA), and binding inhibition assay. Binding assays revealed that all strains of S. dysgalactiae subsp. dysgalactiae (S. dysgalactiae) evaluated in this study bound to Lf. However, differences in Lf binding capability among strains and between methods used were detected. Binding of Lf was not inhibited by transferrin (Tf) and Lf moiety molecules (mannose, galactose, and lactose) but by Lf. This study demonstrates that S. dysgalactiae bound to bovine Lf in a specific manner.

Role of collagen in adherence of Streptococcus uberis to bovine mammary epithelial cells

We reported previously that pre-incubation of Streptococcus uberis with collagen induced expression of S. uberis surface proteins. In a subsequent study, we showed that incubation of S. uberis with extracellular matrix proteins, particularly collagen, increased adherence and internalization of S. uberis to mammary epithelial cells. In the present report, the potential mechanism by which S. uberis exploits the presence of collagen to enhance adherence to bovine mammary epithelial cells was evaluated. Adherence assays were conducted with S. uberis pre-treated with and without collagen and co-cultured in medium supplemented with or without collagen. Pre-incubation with collagen followed by co-culture in medium containing collagen up-regulated ligands that enhanced adherence of S. uberis to mammary epithelial cells. Collagen-up-regulated ligand(s) also increased adherence of S. uberis to mammary epithelial cells in the absence of collagen, but adherence was lower than when collagen was present during the adherence assay. Chloramphenicol was added to the culture medium to inhibit bacterial protein synthesis. Adherence decreased significantly in chloramphenicol-treated S. uberis pre-treated or co-cultured in the presence of collagen. These results suggest that S. uberis expresses ligands with affinity for collagen that are up-regulated by collagen. We hypothesize that these ligands increase adherence by using collagen as a bridge between the bacterium and host cell and/or by direct interaction with host cell receptor(s).

Interaction of coagulase-negative Staphylococcus species with bovine mammary epithelial cells

Three coagulase-negative Staphylococcus species (CNS) (Staphylococcus epidermidis, Staphylococcus xylosus and Staphylococcus hyicus), from the milk of cows with mastitis, were used to evaluate adherence to and internalization by bovine mammary epithelial cells, and to investigate involvement of host cell signal transduction and host cell cytoskeleton rearrangement on internalization of CNS. S. xylosus showed highest adherence and internalization values of the species evaluated. Host cell cytoskeleton polymerization and protein kinase (PK) phosphorylation were required for internalization of CNS. Both protein kinase C (PKC) and tyrosine kinase (TPK) pathways were involved, but internalization of S. xylosus occurred preferentially through epidermal growth factor TPK activity. S. epidermidis and S. hyicus seemed to exploit other TPK pathways. Results of this study showed that S. xylosus, S. hyicus and S. epidermidis were able to adhere and internalize bovine mammary cells in a process that appeared to be receptor(s) mediated and exploited host signal transduction and cytoskeleton to induce an uptake signal.

Studies about the mechanism of internalization by mammary epithelial cells of Escherichia coli isolated from persistent bovine mastitis

The purpose of this study was to investigate the interaction between Escherichia coli and primary mammary epithelial cell cultures derived from cows with persistent intramammary infection (IMI). Two strains of E. coli, isolated from the milk of two different cows suffering from persistent E. coli IMI were tested for adhesion to and invasion of three primary mammary epithelial cell cultures derived from mammary biopsies of the two infected cows. Intracellular E. coli were detected during five days post infection in vitro. Both strains of E. coli adhered to and invaded monolayers of all three primary mammary epithelial cell cultures. One strain adhered less but invaded more than the other. Comparison with other mammary pathogens indicated that E. coli invaded the cells less efficiently than Staphylococcus aureus, about as efficiently as Streptococcus dysgalactiae and more efficiently than Streptococcus uberis. The mechanism of E. coli invasion was studied using the cytoskeleton disrupting agents colchicine and cytochalasin D. These compounds inhibited the invasion of E. coli. Invasion of E. coli could also be inhibited by the phosphokinase inhibitors genistein and staurosporin in a dose-dependent fashion. Phorbol-myristyl-acetate (PMA) had no effect on the invasion of E. coli. Histology of mammary tissue revealed chronic inflammatory changes in quarters that were persistently infected by E. coli. Intracellular bacteria were not detected in mammary tissue sections. Polymerase chain reaction (PCR) analysis suggested that the two strains of E. coli lacked genes encoding for bundle-forming pili (bfpA), intimin (eae) and translocated intimin receptor (tir), which are characteristic for enteropathogenic E. coli (EPEC).

Efficacy of a new premilking teat disinfectant containing a phenolic combination for the prevention of mastitis

A teat disinfectant containing a phenolic combination was evaluated in a natural exposure study in two dairy research herds. Premilking teat disinfection was compared with a negative control using a split-udder experimental design. In both herds, premilking and postmilking teat disinfections with the phenolic combination were significantly more effective in preventing new intramammary infection (IMI) than was postmilking teat disinfection only. Clinical mastitis and new IMI by Streptococcus uberis, Streptococcus dysgalactiae, Gram-negative pathogens, and coagulase-negative Staphylococcus species were significantly lower in quarters of cows with teats predipped and postdipped than in quarters with teats postdipped only. No chapping or teat skin irritation was observed. Premilking teat disinfection with the phenolic combination in association with good udder preparation and postmilking teat disinfection can further reduce the occurrence of new IMI by numerous mastitis pathogens during lactation.

Access to care and use of health services by low-income women

Data from the 1997 National Survey of America's Families (NSAF) are used to analyze access to care and use of health care services for low-income women. Three groups of women are examined: those with Medicaid coverage, those with private coverage, and those with no insurance. Findings show that uninsured women faced larger access barriers and utilized fewer services, particularly preventive care services, than women with either public or private coverage. Access and use did not differ greatly between Medicaid and privately covered women. The results suggest that expansions in coverage, either through Medicaid or through private options, could improve access to care for uninsured women.

Influence of bacterial factors on proliferation of bovine mammary epithelial cells

Effects of bovine mastitis pathogen virulence factors on mammary epithelial cell function are not clearly understood. In this study, the effect of streptococcal lipoteichoic acid (LTA), streptokinase, and Escherichia coli lipopolysaccharide (LPS) on proliferation of a primary bovine mammary epithelial cell culture (BTE) and on an established bovine mammary epithelial cell line (MAC-T) was evaluated. Mammary epithelial cells were cultured in the presence of bacterial virulence factors for 48 h at 37 degrees C. BTE cell proliferation was inhibited by streptococcal LTA at 8 and 16 micrograms/ml whereas MAC-T cell proliferation was reduced significantly by concentrations of LTA > or = 2 micrograms/ml. Streptokinase had no effect on proliferation of either MAC-T or BTE cells and LPS inhibited proliferation of BTE but not of MAC-T cells. Effect of LTA and LPS on mammary epithelial cell proliferation could be relevant during the periparturient period when mammary glands are markedly susceptible to new intramammary infection and when mammary epithelial cells undergo extensive proliferation, differentiation and synthesis of milk components.

Adhesion and invasion of Escherichia coli from single and recurrent clinical cases of bovine mastitis in vitro

Seven strains of Escherichia coli, originating from clinical cases of bovine mastitis, and one Salmonella typhimurium control strain were tested for their ability to adhere to, and invade, bovine mammary epithelial cells (MAC-T cells) in vitro. Four of the seven strains were isolated from cows with chronic intramammary infections with recurrent episodes of clinical mastitis and three strains were isolated from single cases of clinical mastitis. Both adhesion and invasion of all strains were dose and time dependent. The four E. coli strains isolated from recurrent cases of clinical mastitis invaded twice as frequently as and three times faster than the strains isolated from single cases of clinical mastitis. By contrast, there was no difference in the amount or speed of adhesion between the two types of strains of E. coli. Adhesion and invasion curves of E. coli resembled a two-step chain reaction, where invasion was the rate-limiting step. Although adhesion and invasion of E. coli has not been demonstrated in vivo yet, the results of the present study may contribute to an understanding of the pathogenesis of chronic intramammary infections caused by E. coli.

Effects of lactoferrin and milk on adherence of Streptococcus uberis to bovine mammary epithelial cells

OBJECTIVE

To determine whether lactoferrin (LF) or milk influenced adherence of Streptococcus uberis to bovine mammary epithelial cells.

SAMPLE POPULATION

Three strains of S uberis from cows with mastitis, pooled milk samples from 3 clinically healthy Jersey cows early in the lactation period, and bovine mammary epithelial cells from a clonal cell line.

PROCEDURES

Adherence of S uberis to bovine mammary epithelial cells in the presence of various concentrations of LF or milk and after pretreatment of bacteria with LF or milk was tested. Bacteria were cultured with mammary epithelial cell monolayers for 1 hour. The culture supernatant was removed, and the epithelial cells were lysed. Adherence index was calculated as number of colony-forming units (CFU) in the cell lysate divided by number of CFU in the supernatant times 10,000.

RESULTS

All 3 strains of S uberis were found to bind to purified LF and LF in milk. Addition of LF to the culture medium enhanced adherence of all 3 strains to mammary epithelial cells, whereas addition of milk enhanced adherence of 2 strains and decreased adherence of the third. Pretreatment of bacteria with LF or milk increased adherence of 1 of the strains but decreased adherence of the other 2. Increased adherence was antagonized by rabbit antibovine LF antibody.

CONCLUSIONS

Results suggest that LF may function as a bridging molecule between S uberis and bovine mammary epithelial cells, facilitating adherence of the bacteria to the cells.

Influence of protein kinase inhibitors on Streptococcus uberis internalization into bovine mammary epithelial cells

Previous reports indicated that bovine mammary epithelial cells internalized Streptococcus uberis, a bovine mastitis pathogen, and that inhibitors of F-actin microfilament polymerization inhibited bacterial internalization into mammary epithelial cells. In the present report, we show that inhibitors of eukaryotic cell tyrosine protein kinase (TPK) and protein kinase C (PKC), staurosporine, genistein and tyrphostin, significantly reduced internalization of S. uberis into mammary epithelial cells. Short-term treatment (15 min) of mammary epithelial cells with 12- O -tetradecanoylphorbol-13-acetate (TPA), shown previously to up-regulate activity of PKC, significantly increased internalization of S. uberis. Conversely, long-term incubation (24 h) of epithelial cells with TPA, which down-regulates PKC activity, significantly reduced the number of internalized S. uberis. These results suggest that protein kinases (TPK and PKC) are involved in internalization of S. uberis into bovine mammary epithelial cells. Identification of host cell surface receptor(s) and ligands that trigger the uptake signal by S. uberis need to be delineated.

Evaluation of a postmilking teat disinfectant containing a phenolic combination for the prevention of mastitis in lactating dairy cows

A trial was conducted for 12 months in a herd of 120 Holstein cows in order to determine the efficacy of a teat disinfectant, which contained a phenolic combination, for the prevention of bovine intramammary infections during lactation. Postmilking teat disinfection was compared to a negative control using a split-udder experimental design. The percentage of quarters newly infected by mastitis pathogens was 45% lower in mammary glands with teats that had been dipped in the experimental teat disinfectant after milking than it was in undipped controls. New infections caused by Streptococcus uberis, Staphylococcus aureus, coagulase-negative Staphylococcus species, and Corynebacterium bovis were significantly lower in mammary glands with teats that had been dipped in the experimental teat disinfectant than in undipped controls. No statistical differences in the incidence of clinical mastitis between treatment groups were observed. No irritation or chapping of teats dipped in the experimental teat disinfectant were observed. The results of this study suggest that the experimental teat disinfectant containing a phenolic combination is an effective postmilking teat disinfectant for use in the prevention of new intramammary infections by both contagious and environmental mastitis pathogens.

Incubation of Streptococcus uberis with extracellular matrix proteins enhances adherence to and internalization into bovine mammary epithelial cells

Two strains of Streptococcus uberis (UT 888 and UT 366) isolated from cows with clinical mastitis were co-cultured with bovine mammary epithelial cells (MAC-T) with and without laminin, fibrinogen, fibronectin or collagen. Incubation of S. uberis with extracellular matrix proteins (ECMPs) increased adherence to and internalization into MAC-T cells. Both strains of S. uberis exhibited greater adherence when co-cultured in the presence of collagen than with any other ECMP. However, adherence was always higher when strains were co-cultured with ECMP than in medium alone. S. uberis UT 888 adhered better to MAC-T cells than S. uberis UT 366. The influence of ECMPs on bacterial internalization into MAC-T cells was similar to adherence, however, differences among ECMPs were less noticeable. S. uberis UT 888 had a higher internalization index than S. uberis UT 366. It is possible that ECMPs induce or up-regulate proteins that selectively adhere to ECMPs which could serve as a bridge between the eukaryotic cell and the bacterial pathogen that leads to internalization of the ECMP-bound pathogen into the mammary epithelial cell.

Adherence and internalization of Streptococcus uberis to bovine mammary epithelial cells are mediated by host cell proteoglycans

The role of cell glycosaminoglycans (GAG) on adherence and internalization of Streptococcus uberis to bovine mammary epithelial cells was evaluated by adherence/internalization competition assays, by removal of GAG from the host cell surface and by inhibition of GAG glycosylation in the host cell. Heparin (HEP), heparan sulfate (HSA), chondroitin sulfate A (CSA) and chondroitin sulfate B (CSB) inhibited adherence and internalization of S. uberis in a dose-dependent manner. However, inhibition was lower with CSA and CSB than that observed with HEP and HSA. Adherence and internalization were also inhibited upon treatment of mammary epithelial cells with GAG lyases. The greatest inhibition was observed with heparinase I. Tunicamycin, an inhibitor of mammalian cell glycosylation of cell surface glycoproteins, markedly inhibited internalization of S. uberis into mammary epithelial cells. Differences between strains were observed. These results suggest that a HSA proteoglycan receptor on the host cell surface may mediate S. uberis adherence to and internalization of bovine mammary epithelial cells.

Decreased growth of Streptococcus uberis in milk from mammary glands of cows challenged with the same mastitis pathogen

Milk samples from mammary glands challenged with Streptococcus uberis and from unchallenged mammary glands were selected for analyses of bacterial growth, antibody response, and lactoperoxidase activity. All challenged mammary glands became infected with isolation of S. uberis and elevated somatic cell counts in milk during the first week after challenge. In vitro growth of the homologous challenge strain and a heterologous strain of S. uberis was significantly lower in milk from challenged mammary glands than in milk from control mammary glands at 3, 5, and 7 days after challenge. Removal of casein significantly reduced bacterial growth. In general, antibodies specific to S. uberis started to increase at day 3 post-challenge and were higher in milk from challenged mammary glands than in milk from control mammary glands. There was also a marked increase in total IgG in milk from challenged mammary glands. Growth of S. uberis increased following heat treatment at 56 degrees C of pooled milk or whey samples from challenged mammary glands. Growth of S. uberis correlated negatively with the specific antibody response to the bacteria (P < 0.001). Lactoperoxidase activity varied among cows and among different samples over time and did not appear to contribute to decreased growth of S. uberis. These results suggest that decreased growth of S. uberis in milk from challenged mammary glands in comparison to milk from control mammary glands could result from the interaction of antibodies with complement components.

Virulence factors of Streptococcus uberis isolated from cows with mastitis

For intramammary infections (IMI) to occur, mechanisms associated with avoidance of phagocytic defenses, rapid growth of bacteria, adherence of bacteria to epithelial cells, and/or bacterial colonization of mammary tissue are probably present. During the last decade, several potential virulence factors of Streptococcus uberis have been identified. Some of these factors are cell-associated while other factors are extracellular. Proposed antiphagocytic factors of S. uberis include capsule, neutrophil toxin, M-like protein and R-like protein. Activation of plasminogen by S. uberis has been proposed as an important mechanism for this organism to obtain nutrients for optimal bacterial growth. Potential virulence factors produced by S. uberis and released extracellularly include hyaluronic acid capsule, hyaluronidase and uberis factor. Streptococcus uberis isolated from bovine IMI adhere to and invade mammary epithelial cells. Involvement of intact microfilaments and de novo eukaryotic protein synthesis are required for bacterial invasion of mammary epithelial cells; a process that appeared to occur by a receptor-mediated endocytosis mechanism. De novo bacterial protein synthesis was also required for invasion of S. uberis into mammary epithelial cells. Furthermore, S. uberis survived within mammary epithelial cells for extended periods of time without losing viability or damaging the eukaryotic cell. Further research directed towards characterization of host-pathogen interactions that take place during the early stages of S. uberis intramammary infection are needed to enhance our understanding of pathogenesis and thus contribute to development of methods to minimize production losses associated with S. uberis mastitis in dairy cows.

Potential virulence factors of Streptococcus dysgalactiae associated with bovine mastitis

Mastitis caused by environmental pathogens is a major problem that affects many well-managed dairy herds. Among the environmental pathogens, Streptococcus dysgalactiae is isolated frequently from intramammary infections during lactation and during the nonlactating period. In spite of its high prevalence, little is known about factors that contribute to the virulence of S. dysgalactiae. During the last decade, several cell-associated and extracellular factors of S. dysgalactiae have been identified; yet, the relative importance of these factors in the transmission and pathogenesis of mastitis caused by S. dysgalactiae has not been defined. Streptococcus dysgalactiae can interact with several plasma and extracellular host-derived proteins such as immunoglobulin G, albumin, fibronectin, fibrinogen, collagen, vitronectin, plasminogen, and alpha 2-macroglobulin. These interactions are mediated by bacterial surface proteins. This organism also produces hyaluronidase and fibrinolysin which may be involved in promoting dissemination of the organism into host tissue. Streptococcus dysgalactiae adheres to and is internalized by bovine mammary epithelial cells in vitro. Involvement of host cell kinases, intact microfilaments and de novo eukaryotic protein synthesis are required for internalization of S. dysgalactiae into bovine mammary epithelial cells; a process that appeared to occur by a receptor-mediated endocytosis mechanism. However, de novo bacterial protein synthesis was not required for epithelial cell internalization. Furthermore, S. dysgalactiae survived within mammary epithelial cells for extended periods of time without losing viability or damaging the eukaryotic cell. Further research on characterization of host-pathogen interactions that take place during the early stages of mammary gland infection will enhance our understanding of pathogenesis of intramammary infection which may contribute to development of methods to minimize production losses due to mastitis.

Managed care's impact on Medicaid financing for early intervention services

Medicaid has been a major source of financing for early intervention services since the inception of the Infants and Toddlers with Disabilities Program in 1986. In this article, the authors analyze Medicaid financing of early intervention services in 39 States before and after the introduction of managed care. The association between level of Medicaid financing and program characteristics, provider arrangements, managed care carve-out policies, and managed care contract requirements is assessed. The authors discuss the reduction of Medicaid financing after managed care and its implications for State Infants and Toddlers with Disabilities Programs, State Medicaid agencies, and managed care organizations.

Eukaryotic and prokaryotic cell functions required for invasion of Staphylococcus aureus into bovine mammary epithelial cells

Eukaryotic and prokaryotic cellular functions required for invasion of Staphylococcus aureus into bovine mammary epithelial cells were investigated. Two strains of S. aureus isolated from milk of cows with clinical mastitis, a primary bovine mammary epithelial cell culture and a bovine mammary epithelial cell line were pretreated with inhibitors of nucleic acid and protein synthesis. In addition, mammary epithelial cells were pretreated with inhibitors of receptor-mediated endocytosis and oxidative phosphorylation. Protein and nucleic acid synthesis in prokaryotic and eukaryotic cells and eukaryotic oxidative phosphorylation were required for invasion of S. aureus into mammary epithelial cells. Inhibition of receptor-mediated endocytosis caused a significant reduction in the number of invading S. aureus. These results suggest that invasion of S. aureus into bovine mammary epithelial cells occurs through a receptor-mediated endocytosis process. Furthermore, eukaryotic oxidative metabolism, protein synthesis and nucleic acid synthesis as well as bacterial protein synthesis are required for bacterial invasion.

Medicaid managed care policies affecting children with disabilities: 1995 and 1996

The authors present findings from a study of State Medicaid managed care enrollment and benefit policies in 1995 and 1996 for children with disabilities. During this time the number of States serving children through fully capitated plans grew by more than one-third, and enrollment of children receiving Supplemental Security Income (SSI) payments and children in subsidized foster care increased. Most States required plans to provide all mandatory and most optional Medicaid services. Although States have begun to make noticeable improvements in their contract language concerning medical necessity and the early and periodic screening, diagnosis, and treatment (EPSDT) benefit, overall State guidance in these areas remains weak.

Adherence of Streptococcus uberis to bovine mammary epithelial cells and to extracellular matrix proteins

Adherence of an encapsulated (UT 101) and a non-encapsulated (UT 102) strain of Streptococcus uberis to a bovine mammary epithelial cell line (MAC-T) and to extracellular matrix proteins (ECMP) including fibronectin, collagen and laminin was investigated. S. uberis was co-cultured at 4 degrees C with MAC-T cell monolayers. Both strains of S. uberis adhered to MAC-T cells. However, the non-encapsulated strain of S. uberis adhered better to MAC-T cells than the encapsulated strain. Preincubation of MAC-T cells with lipoteichoic acid (LTA) and/or treatment of S. uberis with antibodies directed against the carboxyl-terminal half of type 24 M protein reduced adherence of both strains of S. uberis to MAC-T cells. Adherence to ECMP was measured by incubating bis-carboxyethyl-carboxyfluorescein acetomethyl ester (BCECF-AM) labelled S. uberis in 96-well plates coated with fibronectin, collagen or laminin. Both strains adhered to ECMP, however, the encapsulated strain adhered better to ECMP than the non-encapsulated strain. Results of this investigation demonstrated that both strains of S. uberis evaluated were capable of adhering to bovine mammary epithelial cells and to ECMP. Adherence of S. uberis to mammary epithelium may be an extremely important mechanism in the establishment and progression of bovine intramammary infections.

Influence of Streptococcus dysgalactiae surface hydrophobicity on adherence to mammary epithelial cells and phagocytosis by mammary macrophages

Bacterial surface hydrophobicity (SH) plays a role in adhesion of bacteria to host surfaces and ingestion by phagocytic cells. Streptococcus dysgalactiae (n = 60) isolated from bovine intramammary infections were examined for expression of SH after growth in Todd-Hewitt broth (THB) and THB supplemented with skim milk, whey, lactose, and casein. Strains were significantly more hydrophobic after growth in THB and THB plus whey and more hydrophilic after growth in THB plus skim milk. Both trypsin and proteinase K abolished SH in three strains tested. Mild pepsin treatment had little effect on SH, while heat treatment at 70 degrees or 80 degrees C abolished SH in two strains tested. A hydrophilic strain of S. dysgalactiae did not adhere as well to bovine mammary epithelial cells as a hydrophobic strain. Trypsin treatment significantly reduced adherence of a hydrophobic strain of S. dysgalactiae to epithelial cells while adherence of a hydrophilic strain remained unaltered. A hydrophilic strain of S. dysgalactiae was significantly more resistant to phagocytosis by bovine mammary gland macrophages than a hydrophobic strain. Differences in expression of SH may play an important role in determining the ability of S. dysgalactiae to establish successfully within the mammary gland.

Staphylococcus aureus invasion of bovine mammary epithelial cells

Staphylococcus aureus is a frequent cause of mastitis in dairy cows. However, pathogenesis of the infection has not been completely defined. We report the invasion of two strains of S. aureus into a bovine mammary epithelial cell line and a bovine mammary epithelial cell primary culture. Invasion of S. aureus into bovine mammary cells was time-dependent. Transmission electron microscopy of bovine mammary cells invaded by S. aureus showed intracellular replication of the bacterium within membrane-bound vacuoles. Invasion was reduced significantly when bovine mammary epithelial cells were treated with inhibitors of F-actin microfilament polymerization but not when these cells were treated with inhibitors of microtubule formation. Results indicated that S. aureus is capable of invading and replicating inside bovine mammary epithelial cells. Data also suggested that S. aureus invasion of bovine mammary epithelial cells requires active participation of specific components of the cytoskeleton of the epithelial cell.

Phagocytosis of Streptococcus uberis by bovine mammary macrophages: opsonizing effect of bovine antiserum

Five encapsulated and five non-encapsulated strains of Streptococcus uberis were tested for their ability to resist phagocytosis and intracellular killing by bovine mammary macrophages obtained during the non-lactating period. The percentage of phagocytosis and intracellular killing of encapsulated strains ranged from 43 to 51 and from 25 to 40, respectively. By contrast, the percentage of phagocytosis and intracellular killing of non-encapsulated strains ranged from 66 to 74 and from 65 to 75, respectively. Two encapsulated and two non-encapsulated strains were opsonized with homologous and heterologous pre-immune and immune bovine sera. Phagocytosis and intracellular killing of encapsulated strains increased significantly when opsonized with serum of cows vaccinated with a homologous and heterologous encapsulated strain. By contrast, no significant differences were observed when serum from cows vaccinated with a non-encapsulated strain was used. These results suggest that resistance to phagocytosis is a common feature among encapsulated strains of S. uberis, and that cross-reactivity exists between encapsulated strains.

Invasion of bovine mammary epithelial cells by Streptococcus dysgalactiae

Two strains of Streptococcus dysgalactiae, isolated from cows with mastitis, were assayed for their ability to invade, multiply, and induce damage to a bovine mammary epithelial cell line, MAC-T. Invasion of S. dysgalactiae into MAC-T cells was time-dependent, and invasion was inhibited in a dose-dependent manner by cytochalasin B and D, but not by colchicine. The invasion process did not appear to affect viability of mammary epithelial cells, but cellular damage was induced, as indicated by a time-dependent release of increasing amounts of lactate dehydrogenase. No net intracellular bacterial growth was observed, but S. dysgalactiae survived inside MAC-T cells. These results indicated that S. dysgalactiae invaded epithelial cells, induced cellular damage, and was capable of persisting inside bovine mammary epithelial cells.

Bovine mammary epithelial cell invasion by Streptococcus uberis

Streptococcus uberis commonly causes bovine mastitis; however, the pathogenesis of this infection is poorly understood. In this study, the ability of S. uberis to invade mammary epithelial cells in culture was investigated. Two strains of S. uberis isolated from bovine mammary secretions were capable of invading bovine mammary epithelial cells in vitro at different levels, suggesting strain differences in invasiveness. Invasion required microfilaments but not microtubular cytoskeletal elements. No morphological changes in epithelial cells were observed for up to 24 h postinfection, suggesting no cellular injury. Strains of S. uberis evaluated were genetically distinct and differed phenotypically in expression of potential virulence factors. Whether a single factor or combination of factors was responsible for differences in invasiveness was not addressed in this study. These data provide a foundation for a better understanding of the processes used by S. uberis to invade epithelial cells. Epithelial cell invasion may be a potentially important mechanism in the pathogenesis of S. uberis mastitis.

Impaired tracheobronchial clearance of bacteria in calves infected with Mycoplasma dispar

Infection of tracheal organ cultures with Mycoplasma dispar results in degeneration of respiratory epithelial cells with loss of ciliary activity. To assess the effect of these changes on the clearance of bacteria from the respiratory tract, the tracheobronchial clearance of a suspension of Serratia marcescens was determined in calves before and after infection with M. dispar. Tracheobronchial samples were obtained at various times after deposition of the marker bacteria. Clearance of S. marcescens was significant by 3 h after inoculation and only few colonies were detected 4 h after challenge. By contrast, in the same animals 5 days after intratracheal exposure to M. dispar, clearance of S. marcescens did not decrease significantly 4 h after inoculation. Histopathological and scanning electron microscopy (SEM) studies of infected lungs revealed that, as a result of infection with M. dispar, areas of degeneration and destruction of the respiratory ciliated epithelium occur in intermediate and small airways. These lesions may be responsible for the altered clearance observed in these mycoplasma-exposed calves.

Antiphagocytic effect of the capsule of Streptococcus uberis

Non-opsonized encapsulated and non-encapsulated strains of Streptococcus uberis were incubated with bovine mammary macrophages and the percentage of phagocytosis and intracellular killing were determined. Seventy-seven percent of macrophages ingested non-encapsulated organisms with a killing rate of 75%. In contrast, 48% of macrophages ingested encapsulated bacteria with a killing rate of 35%. When strains were opsonized with homologous antiserum, differences were detected in the percentage of phagocytosis (84% vs. 48%) and intracellular killing (52% vs. 35%) of the encapsulated strain only. Effects were partially abolished when antiserum was absorbed with purified capsule, or when macrophages were pre-treated with purified capsular material. Electron microscopy of mammary macrophages incubated with the encapsulated strain of S. uberis showed the microorganism in contact with the macrophage cell membrane without signs of membrane activation. In contrast, the non-encapsulated strain induced formation of pseudopods and membrane ruffling. These results suggest that capsule may protect S. uberis from phagocytosis which may be due to a direct interaction of capsular material with macrophages.

Growth curve, capsule expression and characterization of the capsular material of selected strains of Streptococcus uberis

The pattern of lectin agglutination, expression of capsule during the growth curve, and chemical composition of the capsule were examined in strains of Streptococcus uberis isolated from bovine mastitis. Lectin agglutination was conducted on 40 strains of S. uberis and 82.5% and 77.5% of the strains showed agglutination titers (> or = 1:128) with wheat germ agglutinin and concanavalin A, respectively. Capsule expression during the growth curve and its chemical composition was determined in one strain of S. uberis (UT 101), using a nonencapsulated strain of S. uberis (UT 102) as a negative control. Both strains were grown in Todd-Hewitt Broth (THB) with and without 20% milk whey. Strain UT 101 grown in THB or THB with 20% whey showed maximum numbers of colony forming units per ml (cfu/ml) at 12 hours, with a lag phase ending after 2 hours of growth. Maximum cfu/ml of UT 102 in THB was at 14 hours and 16 hours in THB 20% whey with a lag phase that ended at 2 hours of growth. Higher number of viable bacteria and increased capsule expression of UT 101 were detected in suspensions grown in THB 20% whey than in THB alone. Capsule expression of S. uberis UT 101 was maximal at 10 hours and decreased after 12 hours of growth. In contrast, S. uberis UT 102 showed negligible percentage (< 2%) of encapsulated bacteria during the entire growth curve. Chemical analysis of capsular material and the pattern of lectin agglutination suggest that hyaluronic acid is the major component. These results will be useful for understanding the pathogenesis of infections caused by S. uberis.

Interaction of Mycoplasma dispar with bovine alveolar macrophages

The capacity to avoid phagocytosis and the activation of bovine alveolar macrophages (BAM) by encapsulated Mycoplasma dispar or purified M. dispar capsule was investigated. Encapsulated and unencapsulated M. dispar were cocultured with BAM in the presence or absence of antisera prepared against unencapsulated M. dispar or purified capsule antiserum. Unopsonized mycoplasmas resisted phagocytosis, while only anti-capsule antibodies enhanced the phagocytosis of encapsulated mycoplasmas. BAM were cultured in the presence of purified M. dispar capsule or either live or heat-killed encapsulated or unencapsulated M. dispar. These BAM were then activated with Escherichia coli endotoxin or left without further activation. The supernatants of these cultures were assayed for tumor necrosis factor, interleukin 1, and glucose consumption as indicators of macrophage activation. Tumor necrosis factor and interleukin 1 were produced by BAM stimulated with unencapsulated M. dispar but not when encapsulated M. dispar or its purified capsule was used. Similarly, glucose consumption was increased in the presence of unencapsulated M. dispar, but not when BAM were cocultured with encapsulated M. dispar or purified capsule. When BAM were treated with purified capsule or encapsulated mycoplasmas, they could not be subsequently activated by endotoxin. These results indicate that encapsulated M. dispar or purified capsule exerts an inhibitory effect on the activity of BAM and prevents the activation of these cells.

Capsulelike surface material of Mycoplasma dispar induced by in vitro growth in culture with bovine cells is antigenically related to similar structures expressed in vivo

Electron microscopy has been used to show that Mycoplasma dispar produces an external capsulelike material in vivo that has an affinity for both ruthenium red and polycationic ferritin. This extracellular material is lost upon passage in culture medium but can be regained with a single passage on bovine lung fibroblast (BLF) cells. To confirm that the extracellular material associated with cell-grown mycoplasmas was the same as that observed in infected calves, rabbit antibodies were produced to purified capsulelike material isolated by protease digestion of cell-grown organisms. These antibodies bound to capsulelike material on the surface of M. dispar cells colonizing the bronchial epithelium of infected calves and to capsulelike material from cell-grown mycoplasmas. Calves infected with M. dispar produced antibodies in lung secretions that were capable of binding to the purified capsulelike material. The Fab fragments of rabbit antibodies to in vitro-produced capsulelike material could block this binding, indicating that the capsulelike material was similar in both in vivo-grown and cell-grown organisms. The carbohydrate nature of the capsular material suggested by the ruthenium red and polycationic staining characteristics was confirmed by its binding to Ricinus communis agglutinin, a galactose-specific lectin. These studies confirm that capsule material produced during infections with M. dispar share antigenic determinants with the material produced under in vitro conditions and that association with mammalian cells induces production of this material.