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.

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.

Shiga toxin (stx) producing Escherichia coli (STEC) causes various clinical signs in animal and himan. In this study, 255 fecal samples from samples from calves showing diarrhea were collected from cattle farms in Chonnam province during the period from January 2005 to July 2005. Twenty six STEC (10%) were isolated from 255 fecal samples by PCR. The isolates displayed three different stx combinations (stx1[69%], stx1 and stx2 [15%], and stx2 [38%]). The isolates were further studied for virulence associated genes and antimicrobial resistance to define the virulence properties.

Samples of milk were collected from 425 halves of 216 dairy goats in Chonnam province over a period of January through August 2003. Bacterial isolation was carried out on those samples, and their antimicrobial susceptibility was tested. Bacteria were isolated from 166 milk samples (39.1%), either singly (74.7%) or in combination (25.3%). Of the 220 isolates, Staphylococcus spp. was the most prevalent (82.6%), followed by Streptococcus spp. (2.7%), Corynebacterium spp. (1.8%), Enterococcus spp. (1.8%), and Pasteurella spp. (1.8%).

The objective of this study was to determine the prevalence of pneumonic bacteria in lungs and nasal swabs of cattle with respiratory diseases. From 95 pneumonic lungs of slaughtered cattle, 41 (43.2%) positive lungs were yielded with 54 pneumonic bacteria, which corresponded to P. multocida (n = 34), A. pyogenes (n = 14) and P. haemolytica (n = 6). One-hundred sixty seven pneumonic bacteria were isolated from 195 nasal swabs in calves, 64.7% (108 isolates) belonged to P. multocida, 16.2% to A. pyogenes, 13.8% to P. haemolytica and 5.4% to H. somnus.

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.

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.