The rapid evolution of antibiotic resistance in Staphylococcus (S.) aureus is of considerable concern. Methicillin-resistant S. aureus (MRSA) strains are especially one of the greatest public concerns since the treatment of infections is more difficult when encountering resistance. In this study, we conducted a nationwide survey on the antimicrobial resistance of S. aureus isolated from raw meat samples collected from 16 countries, including Korea, and investigated the prevalence of MRSA as a possible source of human infection. Of 1,984 meat samples, S. aureus was isolated from 218 (11.0%) samples consisting of 23 (12.1%) from domestic meat and 195 (10.9%) from imported meat. The isolated rates of poultry meat, pork and beef were 12.8%, 7.0% and 10.0%, respectively. With regard to imported meat, the incidence varied from 4.8% to 16.6% from 13 countries, with the exception of Austria and Poland. In a resistance test to 20 antimicrobial agents, one hundred and eighty-four isolates (84.4%) were resistant to one or more antimicrobial agents tested. Especially, 17 (7.8%), 124 (56.9%) and 28 (12.8%) isolates showed a resistance to 3, 2 and 1 drugs, respectively. One isolate originating from domestic beef was resistant to 7 drugs. Another isolate originating from imported poultry meat showed resistance to oxacillin and methicillin by the disk diffusion test and minimal inhibition concentration method, but showed negative for detection of the mecA gene.

A 12-year-old female Tammar Wallaby (Macropus eugenii) died after a 6-day history of depression, anorexia, and coughing. The necropsy revealed pustules of varying sizes on the lung surface from which a pure culture of Staphylococcus aureus was ioslated. Histopathologically, the pulmonary nodules formed typical granulomatous inflammation. The center of the granulomatous foci consisted of a necrotic center and grain particles with gram positive cocci that were surrounded by eosinophilic club-like bodies containing Splendore-Hoeppli material.

This study was carried out to investigate the antibiotic resistance pattern of Enterococcus spp. and Staphylococcus aureus (S. aureus) isolated from chicken feces. All isolates showed high resistance to erythromycin (E) and tetracycline (TE). Of the 63 Enterococcus faecalis (E. faecalis) isolates, 73.0% were resistant to E and 98.4% to TE. Of the 44 Enterococcus faecium (E. faecium) isolates, 50.0% were resistant to E and 95.5% to TE. Of the 52 S. aureus isolates, 57.6% were resistant to E and 96.2% to TE. The prevalence of two and three drugs resistance pattern were 28.6% and 17.5% of E. faecalis, 40.9% and 25.0% of E. faecium and 38.5% and 23.1% of S. aureus, respectively.

Neutrophils are present in milk of cows as a means of suppressing invading pathogens during mastitis. However, the manner by which neutrophils traverse the secretory epithelia is still not clear: do they diapedese between epithelial cells or do they kill epithelial cells to gain entry into milk? We investigated the process of bovine neutrophil diapedesis across bovine mammary gland epithelium in vitro. The bovine mammary epithelial cell line MAC-T, grown on collagen-coated filters, formed a confluent monolayer with characteristic tight junctions, basal-apical polarity, and functional barriers to the dye trypan blue. Neutrophils added on the apical surface of the monolayer were stimulated to diapedese across the epithelium by the addition of Staphylococcus aureus (10(7) colony-forming units/ml) to the basal compartment. Light and transmission electron microscopy revealed the series of events for neutrophil transmigration: accumulation of neutrophils on the surface of epithelial monolayer; projection of pseudopods into intercellular junctions and movement of neutrophils between adjacent epithelial cells; and reapproximation of the lateral epithelial cell membranes and reformation of the apical tight junctions after neutrophils crossed the epithelium. Morphologically, epithelial cell damage caused by neutrophil diapedesis was not evident. This in vitro model provides a two-dimensional epithelial sheet by which neutrophil diapedesis can be qualitatively studied under defined conditions. Results of the study suggest a major mode by which bovine neutrophils diapedese across the alveolar epithelia into milk during mastitis.

The main objective of the study reported here was to generate a panel of monoclonal antibodies (MAB) to bovine neutrophil surface antigens, and to identify MAB that modulate neutrophil chemotaxis, respiratory burst, and phagocytosis. A further objective was to study MAB reactivity with resting and activated neutrophils, to identify activation antigens and adhesion molecules. A panel of 14 MAB was generated by producing murine hybridomas. Neutrophils incubated with MAB at 4 C for 2 hours were used in chemotaxis, respiratory burst, and phagocytosis assays. Chemotaxis was evaluated in Boyden chambers, using Escherichia coli endotoxin-activated fetal bovine serum as the chemoattractant. Respiratory burst was determined by measuring chemoluminescence of neutrophils incubated with 5-amino-2,3-dihydro-1,4-phthalazinedione, and serum opsonized zymosan. Phagocytosis was determined by flow cytometry, using fluorescein-labeled Staphylococcus aureus. The MAB S7G8, S5F8G10, S7E10, and S5F8B8 enhanced chemotaxis (to > 125% of control). The MAB S7E10 and S8D9 enhanced respiratory burst activity (to > 125% of control), whereas MAB S2G8, S4G10, S8G10, and S5F8B8 caused inhibition (to < 75% of control). The MAB S2G8, S4G10, S8G10, and S5F8G10 enhanced phagocytosis (to > 125% of control). Chemotaxis, respiratory burst, and phagocytosis values of neutrophils not bound with MAB served as controls for comparison. The MAB binding for nonactivated neutrophils (at 4 C) ranged from 9 to 100%, and for activated neutrophils (at 37 C; at 37 C with phorbol myristate acetate) from 90 to 100%. Binding of MAB S4F5, S5F8B8, S6C6, S7E10, S8D9, and S5F8G10 increased when neutrophils had been incubated at 37 C. Binding of these MAB was further increased after incubation with phorbol myristate acetate (100 ng/ml) at 37 C, indicating recognition of activation antigens by MAB. The MAB generated in this study appeared to be potential candidates for studying mechanisms of neutrophil function and for enhancing neutrophil function in vitro and in vivo.

Sixteen Holstein cows were used to test the effect of postmilking teat treatment on colonization and intramammary infection by Staphylococcus aureus on chapped teats. Treatments were (1) chapping the teat and using 1% I2/10% glycerin postdip solution, (2) 1% I2/10% glycerin postdip solution on nonchapped teats, (3) chapping the teat and using 10% glycerin postdip solution, (4) chapping the teat and not using a postdip solution. All mammary glands were free of S aureus teat skin colonization and intramammary infection at the start of the study. Teats selected for chapping were dipped in 1N NaOH prior to 3 applications of S aureus broth culture; cultures were applied at 12-hour intervals on all teats. Treatments were applied after each milking for 30 days and were initiated after the second broth dip. Teat skin swab specimens and milk samples were collected before treatment application. Teat skin condition was scored daily. Nonchapped teats (treatment 2) did not support skin or orifice colonization by S aureus. Treatment-1 teats healed most rapidly and supported less colonization in skin and orifice than did treatment-3 and -4 teats. Teat skin scores and skin colonization were lower for treatment-3 than treatment-4 teats. A correlation between teat skin colonization and teat skin conditions was found. Two intramammary infections were found in treatment-4 quarters and 1 in a treatment-3 quarter. On the basis of our findings, we concluded that poor teat skin condition will more readily support S aureus colonization, that a dip of 1% I2 with glycerin helped reduce S aureus colonization and was associated with faster healing, and that glycerin in teat dips may be of value in preventing colonization by S aureus and in promoting healing.

Detection of capsular polysaccharide (CP) in milk of cows with natural intramammary infection caused by Staphylococcus aureus was attempted. Five quarters of 5 cows harboring S aureus strains that produce type-8 CP were selected. Using an ELISA with a monoclonal antibody, type-8 CP was not detected in extracts prepared from fresh milk collected aseptically. By contrast, CP was easily detectable after incubation of infected milk at 38 C for 20 hours. Quantitation of CP in extracts from incubated milk samples by use of ELISA indicated a great variation of CP expression by strains. Although an incubation step was necessary to detect CP, results of the study indicate that CP may be expressed in vivo during intramammary infection caused by S aureus.

Phagocytic and oxidative metabolic activities of bovine blood neutrophils were determined in the presence of glycolytic (NaF) and cytoskeletal (colchicine, cytochalasin B, and prostaglandin E1) inhibitors. Phagocytosis and postphagocytic oxidative metabolic activity, measured by nitroblue tetrazolium reduction, were determined using zymosan, Escherichia coli, Staphylococcus aureus, or Streptococcus agalactiae. Sodium fluoride (1.25 micromolar to 1.25 mM concentrations) did not significantly (P greater than 0.05) inhibit phagocytosis of S aureus and Str agalactiae, whereas phagocytosis of zymosan and E coli was significantly (P less than 0.05) inhibited only at 1.25 mM concentration. Colchicine at 1.25 nM to 1.25 micromolar conce ntrations significantly inhibited phagocytosis of zymosan and E coli, but not of S aureus and Str agalactiae. Cytochalasin B at 1.25 nM to 1.25 micromolar concentrations significantly inhibited phagocytosis of zymosan and all 3 bacteria, whereas prostaglandin E1 was noninhibitory at similar concentrations. Nitroblue tetrazolium reduction, in general, was not significantly affected by NaF and cytoskeletal inhibitors.

The tarsocrural joints of 11 horses were inoculated with 1.2 to 2.16 x 10(6) viable Staphylococcus aureus organisms susceptible to a trimethoprim-sulfadiazine (TMP-SDZ) combination with minimal inhibitory concentration (MIC) of 0.25 microgram of TMP/ml and 4.75 microgram of SDZ/ml. Antimicrobial treatment consisted of oral administration of a TMP-SDZ combination-30 mg/kg of body weight given once daily (group-1 horses) or 60 mg/kg given as 30 mg/kg every 12 hours (group-2 horses). Paired serum and synovial fluid samples were obtained before intra-articular inoculation with the S aureus, after inoculation with S aureus but before antimicrobial treatment, and after inoculation at various hourly intervals after oral administration of the TMP-SDZ combination. The TMP-SDZ combination was administered daily in the 2 dosages for 21 days. Samples were collected after day 3 of repetitive drug administration so that drug steady-state concentration would have been achieved. Serum and synovial fluid samples were analyzed for TMP and SDZ concentrations. Administration of the TMP-SDZ combination at a dosage of 30 mg/kg once daily was not effective in maintaining TMP or SDZ concentrations above the MIC of TMP-SDZ for the S aureus (0.25 and 4.75 microgram/ml for TMP and SDZ, respectively) in the infected synovial fluid or in maintaining adequate TMP concentration in the serum. The alternative use of the TMP-SDZ combination at a dosage of 60 mg/kg given as 30 mg/kg every 12 hours was effective in maintaining serum and synovial fluid concentrations of TMP and SDZ that were greater than the MIC for the infective organism. Sulfadiazine concentration was significantly (P less than or equal to 0.05) lower in the infected synovial fluid sample than that in the corresponding serum sample. We concluded that administration of 60 mg of TMP-SDZ/kg given as 30 mg/kg every 12 hours is more effective than 30 mg/kg given once daily for the treatment of equine infectious arthritis caused by organisms for which the MIC of TMP-SDZ is less than or equal to 0.25-4.75 microgram/ml.

This study was conducted to determine the antimicrobial activity of starch-based biodegradable antimicrobial films incorporated with biosynthesized silver nanoparticles (Ag-NPs) against multiple drug-resistant Staphylococcus aureus food isolates. Herein, the in-vitro antimicrobial activities of Origanum marjorana (OM) leaf extract, OM essential oil, OM nano-emulsion, chemically synthesized Ag-NPs (chem-Ag-NPs), and OM-based biosynthesized Ag-NPs (bio-Ag-NPs) using OM extracts were determined against a cocktail of three pathogenic Staphylococcus (S.) aureus strains isolated from meat products, using the agar well diffusion assay (AWDA). Afterward, homemade starch-based biodegradable antimicrobial films (SBAF) were incorporated with the suitable antimicrobials, based on AWDA and preliminary experiments, and investigated for their antimicrobial properties against S. aureus cocktail through the disc diffusion assay (DDA). The obtained results showed that in WDA, bio-Ag-NPs (1mM) had a significantly higher antimicrobial activity than chem-Ag-NPs (1mM), with inhibition zones accounting for 23 and 19mm, respectively. Whereas both types of nanoparticles were significantly more potent in their antimicrobial properties than different concentrations of OM extract, essential oil, and nano-emulsion (p<0.05). In concern to SBAF incorporated with antimicrobials, SBAF incorporated with chem-Ag-NPs (SBAF/chem-Ag-NPs) showed a significantly stronger antimicrobial effect than SBAF incorporated with bio-Ag-NPs (SBAF/bio-Ag-NPs) in the DDA, while both types of films produced significantly larger zones of inhibition than other antimicrobials (p<0.05). These homemade biodegradable films incorporated with bio-Ag-NPs could be a good alternative to petroleum-based packaging (plastic) in food packaging applications and meanwhile improve food safety and quality. Further studies investigating the effectiveness of these films on bacterial isolates inoculated in real food samples are suggested.