• Journal of Veterinary Clinics
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• v.20 no.2
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• pp.166-171
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• 2003

Milk samples were collected from a total of 418 quarters of 214 Holstein cows. Of these, samples which were positive on California Mastitis Test (CMT) and above 200,000 cells/ml by somatic cell counts were subjected to bacteriological examination and antimicrobial susceptibility test. Major pathogens responsible for mastitis included coagulase-negative staphylococci (34.3%), coagulase-positive staphylococci (21.5%), gran-negative rod (coliforms and noncoliforms: 12.6%) and Streptococcus spp. (8.4%). These strains were tested with 13 antimicrobial agents by the Kirby and Bauer standardized disc diffusion method. The isolated pathogens were mostly susceptible to amoxicillin and cephalothin, but were resistant to erythromycin.

• Asian-Australasian Journal of Animal Sciences
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• v.23 no.5
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• pp.659-664
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• 2010

The present study was to investigate the effect of the transition from conventional to organic dairy farming on the antimicrobial resistant pattern of pathogens in milk. A farm with tie-stall management, with an average herd size of 20 milking cows, was selected based on the owner' willingness to accept, for at least 6 months, the highly restricted protocol developed in this study. Comparisons of bacterial isolates and antimicrobial susceptibilities before changing to an organic farm system (BEFORE) and for 6 months after (AFTER) operating the experimental organic farm system were performed by Fisher's Exact Chi-square tests. Significant levels were defined at p<0.05. During the AFTER period, average frequency of antibiotic treatment was decreased from more than 3 cases/month to less than 1 case/month during which the antibiotic use was authorized only by the veterinarian. In total, 92 and 70 quarter milk samples from 24 and 18 cows during BEFORE and AFTER, respectively, were included in the study. Overall, isolates ranged from a non-resistant level for cephazolin to a very high resistant level to streptomycin (64.71% to 95.45%). Percentages of antimicrobial resistant isolates during BEFORE were significantly higher than during AFTER for ampicillin (43.48% and 5.88%, respectively) and streptomycin (95.45% and 64.71%, respectively). In conclusion, percentages of antimicrobial resistant isolates were decreased after 6 months of operating as an organic farm system.

• Microbiology and Biotechnology Letters
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• v.28 no.4
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• pp.189-194
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• 2000

Microorganisms causing bovine mastitis, swine diarrhea and swine pneumonia were isolated from farms in Chungbuk and Kyunggi Province and the isolates were identified using microbial identification system(MIS). The most common isolates from bovine mastitis were Staphylococcus sp.,Streptococcus sp., and Corynebacterium sp., those from swine diarrhea were Escherichia coli, Salmonella sp., and Clostridium perfringens, those from swine pneumonia were Bordetella bronchiseptica and Pasteurella multocida. Examination of 16 antibiotics against these pathogens revealed that the incidence of antibiotic-resistant microoganisms were very high and that many of these isolates had multiple resistance to various commercially available antibiotics such as penicillin, ampicillin, erythromycin, streptomycin, norfloxacin, and tetracycline. These results suggest that the use of antibiotics in a farm should be controlled in order to decrease the number of antibiotic-resistant microorganisms were very high and that many of these isolates had multiple resistance to various commercially available antibiotics such as penicillin, ampicillin, erythromycin, streptomycin, norfloxacin, and tetracycline. These results suggest that the use of antibiotics in a farm should be controlled in order to decrease the number of antibiotic-resistant microorganisms.

• Journal of Microbiology and Biotechnology
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• v.14 no.3
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• pp.503-508
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• 2004

The antimicrobial substance produced by Lactobacillus bulgaricus was inactivated by protease. It showed inhibitory activity against Staphylococcus aureus ATCC6538, Streptococcus agalactiae ATCC14364, some Gram-positive and Gram-negative bacteria, and characteristics of a bacteriocin. The optimal temperature and culture time for the production of bacteriocin were $30^{\circ}C$ and 10 h, respectively, in the culture of L. bulgaricus. The bacteriocin production started in the exponential phase and reached a maximum at the early stationary phase. Using Staph. aureus ATCC6538 and Strep. agalactiae ATCC14364, known as common bovine mastitis pathogens, as indicator strains for determination of the bacteriocin activity, the antimicrobial activity of the bacteriocin was found to be stable in acidic and neutral pH's (2- 7) even at lOOT, whereas it was lost at high pH (10- 11) and $100^{\circ}C$. The mode of action for the antimicrobial activity was bacteriocidal, and the molecular weight determined by SDS-PAGE and overlay method was 14 kDa.

• Food Science of Animal Resources
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• v.27 no.4
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• pp.543-547
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• 2007

Bovine mastitis is costly infectious disease of dairy cattle, being responsible for significant economic losses all over the world. Also, mastitis has troubled about resistance to antibiotics. The purpose of this study was to screen a novel antimicrobial strain from various sources (raw milk and feeds (from farm of Paju, Dangjin, and Hwasung), commercial milk, Korean traditional fermented foods, and chicken feces). The isolate was screened using triple agar layer method and deferred method was used for confirmation of antimicrobial effect. Seventy six of isolates were screened using triple agar layer method. In these strain, 42 isolates were shown a broad spectrum of autimicrobial activity against mastitis pathogens. Especially, fourteen isolates were shown over 20 mm inhibition zone against S. aureous ATCC 25923. These results suggest that these novel antimicrobial strains could be used for the alternative of antibiotics.

• Journal of Veterinary Clinics
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• v.21 no.2
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• pp.129-132
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• 2004

Causative agents of mastitis were isolated from glandular tissues of 101 culled Holstein cow udders and tested with antimicrobials by standardized disc diffusion method. Pathogens most commonly isolated were coagulase-negative staphylococci (43.9%) and streptococci (21.4%). Most of the udders (88.5%) showed mixed infections with more than two species of bacteria. Antimicrobial sensitivity tests revealed that 90.0% and 84.5% of the isolated organisms were susceptible to amoxicillin and gentamicin, while most organisms were resistant to erythromycin. Coliforms were resistant to ampicillin, cephalothin, cefazolin, erythromycin, kanamycin, neomycin, penicillin and tetracycline and streptococci to erythromycin, kanamycin, neomycin, trimethoprim/sulfamethoxazole and tetracycline.

• Journal of Veterinary Clinics
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• v.5 no.2
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• pp.73-81
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• 1988

Combinations of EDTA-Tris and gentamicin, oxytetracycline in normal bovine milk were examined for synergistic activities aganist Staphylococcus aureus, Streptococcus agalactiae, Corynebacterium Pyogenes, Escherichia coli, Salmonella dublin, Pseudomonas aeruginosa, and proteus spp. isolated from the milk of acute clinical bovine mastitis. The results were summarized as follows: 1. The minimal inhibitory concentrations of EDTA-Tris and gentamicin, oxytetracycline on Escherichia coli, Salmonella dublin, proteus spp., Pseudomonas aeruginosa, Staphylococcus aureus, and Streptococcus agalactiae were markedly reduced. 2. The significant synergistic effects observed when the microorganisms were reacted with EDTA-Tris and gentamicin, oxytetracycline. These findings were respectively verified by kinetic studies of microbial death, using one-fourth minimal inhibitory concentrations of EDTA-Tris, gentamicin, and oxytetracycline.

• Korean Journal of Veterinary Research
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• v.20 no.2
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• pp.119-122
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• 1980

The udders of 28 culled dairy cows were removed at slaughter and bacteria isolated. Isolations of major known mammary pathogens comparised Staphylococcus sp. (40.7%), non-identified Gram's negative rods (33.2%) and E. coli (7.4%). In the mixed infection, Staphylococcus sp. was most frequently involved. Drug sensitivity tests were performed on several bacterial species by disc method. These tests indicated that the microorganisms isolated from clinical mastitis of dairy cows were more resistant to antimicrobial agents than the organisrms isolated from milk samples.

• Journal of Veterinary Science
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• v.19 no.6
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• pp.771-781
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• 2018

Staphylococcus aureus is one of the major pathogens causing bovine mastitis and foodborne diseases associated with dairy products. To determine the genetic relationships between human and bovine or bovine isolates of S. aureus, various molecular methods have been used. Previously we developed an rpoB sequence typing (RSTing) method for molecular differentiation of S. aureus isolates and identification of RpoB-related antibiotic resistance. In this study, we performed spa typing and RSTing with 84 isolates from mastitic cows (22 farms, 72 cows, and 84 udders) and developed a molecular prophage typing (mPPTing) method for molecular epidemiological analysis of bovine mastitis. To compare the results, human isolates from patients (n = 14) and GenBank (n = 166) were used for real and in silico RSTing and mPPTing, respectively. Based on the results, RST10-2 and RST4-1 were the most common rpoB sequence types (RSTs) in cows and humans, respectively, and most isolates from cows and humans clearly differed. Antibiotic resistance-related RSTs were not detected in the cow isolates. A single dominant prophage type and gradual evolution through prophage acquisition were apparent in most of the tested farms. Thus, RSTing and mPPTing are informative, simple, and economic methods for molecular epidemiological analysis of S. aureus infections.

• Journal of Veterinary Clinics
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• v.28 no.6
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• pp.576-580
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• 2011

Silver has potent antibacterial activity against a variety of bacteria while maintaining low toxicity in mammalian cells. This study was conducted to investigate the possible mechanism underlying the bactericidal effects of silver ions against bovine mastitis pathogens using electron microscopy. We used two different bacterial strains, Escherichia coli and Staphylococcus aureus, which are primarily responsible for the majority of bovine mastitis cases. Interaction between the bacteria and silver ions (50 ${\mu}g/mL$, 2 hours) were studied using energy-filtering transmission electron microscopy (EFTEM). EFTEM images showed that E. coli and S. aureus cells treated with the silver ions had distorted plasma membranes, silver ions attached to the outer membranes, scattered electron-light material, and leakage of cell contents from disrupted cell membranes.