Fifteen isolates of Escherichia coli obtained from the blood and tissues of septic foals had plasmid DNA of size ranging from 2.5 to 93 megadaltons. These isolates grew in normal equine serum (serum resistant), a trait previously documented to be expressed by isolates obtained from blood and tissues of septic foals, but not by isolates obtained from the feces of clinically normal horses. Of these isolates, 3 contained conjugal plasmids that encoded resistance to multiple antimicrobial agents linked to serum resistance and, in 1 isolate, to production of aerobactin as well. Serum resistance and production of aerobactin are related to virulence of septicemic E coli from non-equine sources.

A model of bovine pneumonic pasteurellosis, using an indwelling bronchial catheter for inoculation and subsequent lavage of a single main stem bronchus of the lung, was evaluated in a preliminary efficacy trial of an experimental therapeutic compound, Inoculation of 10(7) Pasteurella haemolytica organisms into the bronchus consistently induced a focal pneumonic lesion with typical morphology of pneumonic pasteurellosis in the left or right caudal lung lobe. The experimental treatment caused significant (P < 0.05) reduction in lung lesion volume, compared with that of a saline-treated control. It also caused significant (P < 0.05) reduction in lavage fluid bacterial counts at 48 hours after inoculation, compared with counts in the controls. The inflammatory cell count and the percentage of neutrophils increased markedly in lavage fluids 8 hours after inoculation, but differences were not detected between treatments. Significant differences between treatments were not found in clinical signs, rectal temperature, or histologic changes. This model appears to be a sensitive indicator of treatment efficacy and has the advantage over previous models of pneumonic pasteurellosis of allowing sequential monitoring of the primary lesion site.

Specimens collected from various pyogenic lesions of dogs were culturally examined for staphylococci and all staphylococcal isolates obtained from the specimens were also tested for susceptibility to 14 antimicrobial agents. A total of 123 isolates of staphylococci were identified. Of these, 120 were Staphylococcus intermedius and 3 were S aureus. All isolates were susceptible to oxacillin, cefazolin, cephalothin and amikacin, whereas more than 85% of the isolates were resistant to ampicillin, penicillin G and tetracycline. S intermedius isolates could be divided into 8 different biotypes by biotyping with the most common type accounting for 66.7% of the isolates.

This study was conducted to compare the patterns of mastitic pathogens and the antimicrobial susceptibility of Staphylococcus (S.) aureus from conventional milking (CM) and robotic milking (RM) dairy herds. To accomplish this, the minimum inhibitory concentrations of 14 antimicrobial agents were tested against S. aureus by the microdilution method. Regardless of the milking system, S. aureus, coagulase negative staphylococcus, and Streptococcus uberis were isolated. Additionally, significant differences in the antimicrobial susceptibility of S. aureus isolates between RM and CM farms were only observed in response to tetracycline.

In this study, trends in the sales of antimicrobials for use in livestock facilities and fisheries from 2003 to 2012 were investigated with regard to antimicrobial group, antimicrobial usage, and animal species. The overall amount of antimicrobials sold each year from 2003 to 2007 was 1,500 tons, after which they decreased, with the lowest sales being 936 tons in 2012. The total volume of antimicrobials used for feed additives decreased markedly by 94% from 2003 to 2012, which was mainly attributed to banning of feed additives. However, antimicrobial consumption through self prescription by farmers for disease prevention and treatment increased by 25% from 2003 to 2012. The largest volume of antimicrobials sold was for use in pigs (48~57%), followed by poultry (18~24%), fisheries (11~25%), and cattle (5~8%). Tetracycline was the highest selling antimicrobial, followed by penicillins and sulfonamides, although the overall sale of all three antimicrobials gradually decreased over the study period. This study demonstrated that the total consumption of antimicrobials has gradually decreased since 2008. Nevertheless, usage by nonprofessionals increased, which can ultimately cause emergence and spread of antimicrobial resistance. Thus, early establishment of veterinary prescription guidelines for prudent use of antimicrobials is urgently needed in Korea.

The purpose of present study was to investigate the antimicrobial resistance in Escherichia coli isolated from healthy animals in all provinces of the Republic of Korea. A total of 2,085 E. coli strains isolated from 11,336 fecal samples of healthy animals during 2010-2012 were examined for antimicrobial resistance. Comparison of average resistance rate through the years revealed that tetracycline (47.0% and 76.1%) and streptomycin resistance (42.6% and 64.6%) was most frequently observed in cattle and pigs, respectively. Whereas, in chicken isolates, resistance against nalidixic acid (90.9%) was highest among the antimicrobials tested. Percentage of E. coli that showed multidrug resistance (resistance against¡� three subclasses of antimicrobial agents) was 17.6% (151/860) in cattle, 69.4% (506/729) in pigs, and 86.1% (427/496) in chickens. Overall, the rates of resistance are apparently different between animal species and, in particular, resistance was less prevalent in cattle than in pigs and chickens. In conclusion, this study showed higher prevalence of resistance in commensal E. coli strains to antimicrobial agents in Korean livestock and highlighted the urgent need for measures to regulate the abuse of antimicrobial agents.

Bacterial contamination is an unavoidable finding of the semen collection process in boar and can lead in deleterious effects on semen quality and longevity if left uncontrolled. The purpose of this study is to identify the bacteria in extended boar semen and to select the effective antimicrobials to control of the contaminants. Of 116 extended boar semen samples submitted from eight AI centers in Korea, 39 (33.6%) samples were positive for bacterial contamination. Among 39 contaminated semen, most of them (84.6%) were contaminated with one or two bacterial species and there was no significant difference between two age groups (less-than or equal to 24 and greater than 24 month old). Stenotrophomonas maltophilia (n=18) was the most predominant bacterium followed by Elizabethkingia meningoseptica (n=12), phingomonas paucimobilis (n=12), Myroides spp. (n=5), Ochrobactrum anthropi (n=3), and so on. Enrofloxacin (72.9%), florfenicol (72.9%), bacitracin (49.2%) and tylosin (49.2%) showed higher sensitivity compared with penicillin (13.6%) or aminoglycosides (6.8%-18.6%). Brucella spp., Leptospira spp., Mycoplasma hyopneumoniae, Mycoplasma hyorhinis, Mycobacterium tuberculosis complex were not detected in semen by PCR.

This study was carried out to investigate the serotype, and antimicrobial susceptibility and analyze the plasmid profile for the 145 isolates of L. monocytogenes isolated from livestock products and these product processing plants in Gyeongnam, Korea. All of L. monocytogenes strains belonged to serotype 1/2b (57.9%), 1/2a (20.0%), 4b (11.4%), 1/2c, 3b, 4c (each 2.9%) and 4d (0.7%). Serotype 1/2b, 1/2a, 4b from each source were found predominantly. Serotype 1/2b was predominantly higher than other serotype, and there was no significant difference between serotypes isolated from livestock products and product processing plants.