Tuberculosis (TB) is a significant disease for both humans and animals worldwide. The genus Mycobacterium includes several species that cause TB disease in humans and other animals. Amongst the members of the Mycobacterium tuberculosis complex (MTC), M. tuberculosis is mainly a human pathogen, whereas M. bovis has a broad host range and is the principal agent responsible for TB in domestic and wild mammals. M. bovis also infects humans, causing zoonotic TB through ingestion, inhalation. M. bovis accounts for only a small percentage of the reported cases of TB in humans. In recent years, TB in farmed deer has become a disease as public health importance in several countries. Nowadays, there has been rapid outbreak of bovine TB in cattle and deer in Korea. Investigations are needed to elucidate the relative importance of M. bovis on TB incidence in humans, especially in Korea where bovine TB remains a problem. Also, the human sources as the cause of animal infection, M. tuberculosis from the farm workers also important for TB control of animals in Korea. Differentiation between the causative organisms may only be achieved by sophisticated laboratory methods involving bacteriological characteristics, biochemical properties, and routine resistance to pyrazinamide (PZA). M. bovis shows inherently resistant to PZA whereas M. tuberculosis is susceptible to PZA. In this study, we developed a multiplex-PCR assay based on a 12.7-kb fragment for the differential detection of M. bovis and M. tuberculosis. A total of 131 M. tuberculosis complex isolates were randomly obtained from cattle and deers that were PPD positive. they all yielded M. bovis. M. tuberculosis was not isolated from animals. and, a total of 25 M. tuberculosis complex isolates which is resistant to PZA were obtained from patient. PZA resistant MTC in humans was caused entirely by M. tuberculosis. The multiplex-PCR protocol was highly species-specific and time saving for identification of M. bovis and M. tuberculosis. This multiplex-PCR assay will be easily used as a routine monitoring tool in veterinary and medical laboratories.

Salmonellosis constitutes an important public health problem in both developing and developed countries, including Korea. The aims of present study were to investigate the serovar and antimicrobial resistance of Salmonella isolated from food animals and animal products in slaughterhouses and farms. A total of 323 Salmonella were isolated from food animals (n=277) and meats (n=46) during 2010. Of the isolates, 21 different serovars were identified. The predominant serovars were S. Rissen (35%) and S. Montevideo (24.3) in healthy pigs, while S. Enteritidis (25.5%) in healthy chicken. S. Typhimurium (88.8%) was predominant in disease pigs, while S. Gallinarum (29.2%) and S. Montevideo (26.9%) were in diseased chickens. Among meat samples, S. Typhimurium (57.1%) was the most common serovar in pork but S. Enteritidis (38.7%) and S. Montevideo(32.3%) were in chikcen meats. Analysis of antimicrobial resistance patterns revealed that 20.7% of the isolates were sensitive to all the 15 drugs tested. The isolates were frequently resistant to nalidixic acid (47.7%), tetracycline (38.4%), streptomycin (33.7%), and ampicillin (32.8%). The resistance to quinolone and 3rd generation cephalosporins was higher in chicken and chicken meat isolates. Of the 323 isolates, 174 (53.9%) were resistant to one or more CLSI subclass, and 117 (36.2%) showed multiple-resistance. Our findings showed that multiple resistant Salmonella organism are widespread in animals and animal products in Korea. To prevent the transmission or exposure for consumers of antimicrobial resistant Salmonella, policies and guidelines aiming at prudential use of critical antimicrobials for humans are needed.

Campylobacterosis is the most common food borne bacterial disease in many countries. Food animals and animal products are considered to be the reservoir of the Campylobacter species. The aim of this study was to investigate the antimicrobial resistance of Campylobacter spp. from food animals and raw meats in slaughterhouses. A total of 90 Campylobacter jejuni (C. jejuni) and 127 Campylobacter coli (C. coli) were isolated, for which antimicrobial susceptibility was examined using broth dilution method. Resistance to macrolide antimicrobials was higher among C. coli isolates than among C. jejuni. Among both C. jejuni and C. coli isolates, the most frequently observed resistance was to nalidixic acid, ciprofloxacin, and tetracycline. No erythromycin resistance was observed among C. jejuni isolates from cattle, pig and beef. However, 28.3% (n=13) and 25% (n=3) of C. coli isolates from pigs and pork showed resistance to erythromycin, respectively. The predominant profile of multiple resistance among C. jejuni and C. coli isolates was ciprofloxacin/tetracycline/nalidixic acid resistance (46.7%) and ciprofloxacin/nalidixic acid resistance (31.5%), respectively. This finding has important implication for food safety and public health.

Staphylococcus aureus is an important food-borne pathogen, which is present on the skin and mucosa of animals. Some of the S. aureus strains are causative agent of food poisoning syndrome. The aim of this study was to investigate the antimicrobial resistance of S. aureus isolates from raw meats in slaughterhouses during 2010. From 17,874 raw meat samples tested, a total of 190 S. aureus were isolated, for which antimicrobial susceptibility to 17 agents was examined using broth dilution method. Among isolates from beef, chicken and pork, 20 (51.3%), 20 (24.7%) and 9 (12.9%) were sensitive to all antimicrobials tested, respectively. Isolates from pork and chicken meats showed much higher resistance, compared to isolates from beef. Penicillin resistance was the most frequent among isolates from beef (35.3%) and pork (75.7%), while tetracycline resistance was among those from chicken meats (48.1%). A total of 3 methicillin resistant S. aureus (MRSA) were detected from beef (5.1%, 2/39) and pork (1.4%, 1/70). Although the prevalence of MRSA was low, the presence of antimicrobial resistant S. aureus such as MRSA suggests that further investigation and strict surveillance on MRSA and antimicrobial resistance are needed.

There are many researches about the contribution of virginiamycin use in animals to quinupristin/dalfopristin (Q/D) resistance in humans. In this study, the prevalence and mechanisms of streptogramin resistance in Enterococcus faecium from chickens were investigated. A total of 170 E. faecium isolates from 38 chicken farms was tested for antimicrobial susceptibility. Eleven (6.5%) E. faecium isolates were found to be resistant to Q/D. The vatE and ermB genes were detected in 2 (18%) and 6 (55%) of Q/D-resistant E. faecium respectively. By using pulsed-field gel electrophoresis (PFGE), 6 distinct PFGE patterns were identified. These data indicate that Q/D resistance among E. faecium from chickens remains low despite the long history of virginiamycin use. However, we have to concern over antimicrobial resistance in bacteria originated from animals, including the possibility of transfer of resistance genes from animal to human.

A total of 222 udder-half milk samples of lactating goats were collected from two herds in Korea during 2008 and all samples were subjected to bacteriological examination. Somatic cell counts (SCC) were also determined for all samples except for 13 (5.9%), which were collected from halves of udders with clinical mastitis. A total of 85 bacteria were isolated from 82 (36.9%) of 222 milk samples tested. Staphylococci were the predominant pathogens, accounting for almost 70% of the isolates: Coagulase negative staphylococci (CNS) and S. aureus constituted 55% (47/85) and 14.1% (12/85), respectively. Among 209 samples tested for SCC, bacteria were isolated from 36 of 115 (31.3%) samples with SCC of <1×106 cells/㎖ and 38 of 94 (40.4%) samples that had SCC of ≥1×106 cells/㎖, respectively. All S. aureus were detected from samples with SCC of ≥1×106 cells/㎖, while 25 of 47 (61.0%) CNS were isolated from milk samples with SCC of <1×106 cells/㎖. Mean SCC of milk samples that harbored S. aureus and CNS was 4,787×103 cells/㎖ and >1×106 cells/㎖, respectively. All S. aureus and CNS isolates were susceptible to all antimicrobials tested except for penicillin, to which 2 (16.6%) S. aureus and 12 (25.5%) CNS isolates showed resistance.

One hundred one enterococcal isolates from feces of livestock animals in Korea were screened for the presence of bacteriocins. Sixteen of 41 (39%) E. faecalis and 4 of 56 (7.1%) E. faecium isolates showed antimicrobial activity against at least one indicator strain. Only 4 of 20 the enterococcal isolates showing antimicrobial activity possessed at least one bacteriocin gene. While entA and entB were detected in three isolates as a pair of genotype, entQ, bac31, and AS-48 were not found in the enterococcal isolates. In almost all isolates, a correlation between genotype and phenotype of these determinants was not always observed.

Nontuberculous mycobacteria (NTM) often confounds the interpretation of skin test in tuberculosis diagnosis, resulting in false-positive reaction. And, NTM are emerging pathogens that cause opportunistic infections in both humans and animals. The prevalence of NTM on human disease has been well investigated, whereas that of NTM on animal disease is not well established in Korea. The aim of this study was to determine the prevalence of NTM on cattle, which did not have symptoms of tuberculosis disease. A total of 426 isolates were collected in Korean native cattle and dairy cattle from 2007 to 2010. The most frequently isolated organisms were Mycobacterium peregrimum (n=5, 28%), Mycobacterium fortuitum (n=3, 17%), Mycobacterium intracellulare (n=2, 11%), Mycobacterium phlei (n=1, 5.6%), Mycobacterium terrae (n=1, 5.6%), Mycobacterium llatzerense (n=1, 5.6%), and Norcadia spp. (n=1, 5.6%). It seems to be necessary to further study the prevalence of NTM on environment (water, soil, feces) as well as animals.

For the screening of Brucella antibodies in pig, 2,140 pig serum samples were collected from six slaughter house in Korea between 2006 and 2007. The Rose Bengal test (RBT) and serum agglutination test (SAT) were used for initial screening for specific antibodies to Brucella, and competitive enzyme-linked immunosorbent assay (C-ELISA) was used for confirmation of presence of serum antibody for Brucella. Overall, 575 (26.9%) samples resulted in seropositive in RBT. In SAT, 50 (2.3%) and 10 (0.5%) samples showed suspicious positive and positive reaction, respectively, however, all sera tested in this study showed a negative reaction in C-ELISA. SAT and C-ELISA might be applicable as a tool for screening of swine brucellosis.