[Show abstract][Hide abstract] ABSTRACT: Salmonella enterica subspecies enterica serovar 4,,12:i:-, a monophasic variant of Salmonella Typhimurium, has emerged as one of the most common serotypes related to human salmonellosis. In this study, the 22 isolates of S. 4,,12:i:- from food animals were identified by a specific multiplex polymerase chain reaction between 2009 and 2012. The isolation rate of S. 4,,12:i:- accounted for 1.7% (22/1271) of Salmonella spp. isolates from food animal origins: more specifically, 7.6% (18/235) from pigs and 0.6% (4/686) from chickens. The predominant S. 4,,12:i:- isolates in Korea belonged to phage type DT193 (12/22) with ampicillin-streptomycin-sulfonamide-tetracycline (ASSuT) resistance pattern (9/22). The XbaI-pulsed-field gel electrophoresis (PFGE) analysis revealed 11 different pulsotypes, and the major X-1 pattern was shared by 8 isolates. The isolates belonging to pattern X-1 were further subdivided into three BlnI-PFGE patterns and four variable-number tandem-repeat analysis (MLVA) allele combinations. The combining of MLVA and PFGE data could be valuable in characterizing highly clonal strains and discriminating their epidemiological relationship.
[Show abstract][Hide abstract] ABSTRACT: This study was undertaken to screen methicillin-resistant Staphylococcus aureus (MRSA) in animal carcasses and slaughterhouse workers and characterize MRSA isolates identified during 2010-2012 in Korea. A total of 830 (16.4%) S. aureus and 65 (1.3%) MRSA were isolated from 9669 carcass samples. MRSA was more frequently detected in chicken carcasses (1.2%) than in cattle (0.3%) and pig carcasses (0.6%). The prevalence of MRSA in workers was 6.9% (4/58) in chicken slaughterhouse workers, but no MRSA was detected in pig and cattle slaughterhouse workers (0/41). Two different lineages of MRSA were identified (i.e., human-associated type [ST5, ST59, and ST72] and livestock-associated [LA] type [ST398, ST541, and ST692]); only LA MRSA was observed in chicken carcasses, whereas both types were found in cattle and pig carcasses and workers. All human-associated MRSA isolates carried enterotoxin and/or leukotoxin genes, whereas LA MRSA types did not carry these genes, except ST692 type. However, all LA MRSA isolates were multiresistant, whereas human-associated types were susceptible or resistant to fewer than two antimicrobials except ST5. Furthermore, one or more resistance genes were attributed for resistance to aminoglycosides (aac(6')-Ie-aph(2″), ant(4')-Ia, and aph(3')-IIIa), tetracycline [tet(K), tet(L), tet(M), and tet(S)], macrolide-lincosamide-streptogramin B (ermA, ermB, ermC, and ermT), lincosamide [lnu(B)], phenicol-lincosamide-oxazolidinone-pleuromutilin-streptogramin A (cfr), chloramphenicol (fexA), and fusidic acid [fus(C)]. To our knowledge, this is the first report of tet(S) gene in MRSA isolates and first detection of a unique (ST692) type of MRSA in occupational workers. Detection of new types of human-associated and LA MRSA with multiple resistance and virulence genes in food animal products constitutes a potential threat to public health.
[Show abstract][Hide abstract] ABSTRACT: 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.
Korean Journal of Veterinary Research 09/2014; 54(3):131-137. DOI:10.14405/kjvr.2014.54.3.131
[Show abstract][Hide abstract] ABSTRACT: This study compared the antimicrobial susceptibility and prevalence of virulence genes in Salmonella enterica Typhimurium isolated from healthy and diseased pigs in Korea. A total of 456 Salmonella Typhimurium isolated from healthy (n = 238) and diseased (n
= 218) pigs between 1998 and 2011 were investigated. In total, 93.4% of the Salmonella Typhimurium isolates were resistant to at least one antimicrobial agent tested. The isolates were most often resistant to tetracycline (85.7%), followed by streptomycin (83.6%), nalidixic acid (67.3%),
ampicillin (49.3%), chloramphenicol (42.8%), and gentamicin (37.1%). Moreover, multidrug resistance phenotype and resistance to ampicillin, florfenicol, gentamicin, nalidixic acid, neomycin, streptomycin, and tetracycline were significantly higher (P < 0.01) among Salmonella
Typhimurium isolates from the diseased pigs compared with those from the healthy pigs. The most common resistance pattern observed in both groups of isolates was streptomycin-tetracycline. Overall, more than 96% of the isolates tested possessed invA, spiA, msgA, sipB, prgH, spaN, tolC,
lpfC, sifA, sitC, and sopB virulence genes. The prevalence of orgA, pagC, and iroN were 50.2, 74.1, and 91.0%, respectively, whereas isolates carrying cdtB (1.5%), pefA (7.0%), and spvB (14.9%) were identified much less frequently. Furthermore,
the prevalence of invA, lpfC, orgA, pagC, and iroN was significantly higher (P < 0.01) among the isolates from the diseased pigs than in isolates from the healthy pigs. Our results demonstrated that, among diseased pigs, there was significantly higher resistance to
some antimicrobials and greater prevalence of some virulence genes than in healthy pigs, indicating the role these factors play in pathogenesis. Multidrug-resistant Salmonella isolates that carry virulence-associated genes are potentially more dangerous and constitute a public health
concern. Thus, continuous surveillance of antimicrobial resistance and virulence characteristics in Salmonella is essential.
[Show abstract][Hide abstract] ABSTRACT: 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.
Korean Journal of Veterinary Research 06/2014; 54(2):81-86. DOI:10.14405/kjvr.2014.54.2.81
[Show abstract][Hide abstract] ABSTRACT: Apramycin resistance was observed in 22.8% (81 of 355) of Salmonella Typhimurium isolates collected from pigs from 1998 through 2009 in Korea. All apramycin-resistant Salmonella Typhimurium isolates also were cross-resistant to gentamicin and tobramycin. Among the seven types of aminoglycoside resistance genes tested, only four types were detected in the apramycin-resistant Salmonella Typhimurium isolates: aac (3)-IV, aac (3)-II, aac (3)-III, and ant (2'')-I. Although the aac (3)-IV gene was found in all apramycin-resistant Salmonella Typhimurium isolates, aac (3)-II, aac (3)-III, and ant (2'')-I genes were detected in five (6.2%), two (2.5%), and three (3.7%) isolates, respectively. The apramycin-resistant isolates comprised six phage types, of which PT193 (16 of 81 isolates, 19.8%) was most commonly observed. To our knowledge, this is the first report describing characteristics of apramycin-resistant Salmonella Typhimurium isolates in Korea. Further study is warranted to determine whether apramycin use in animals results in cross-resistance to gentamicin, which may affect public health when gentamicin is required for disease treatment in humans.
[Show abstract][Hide abstract] ABSTRACT: Abstract The aim of this study was to determine the presence and persistence of methicillin-resistant Staphylococcus aureus (MRSA) in milk, farm environment, and farmers on 22 dairy cattle farms in Korea during 2008-2009. Genetic relatedness among the MRSA isolates was also investigated. Of 1146 samples examined, 35 of 559 (6.3%) quarter milk samples from 371 cows, four of 86 (4.7%) hand and nose samples from 43 farmers, and 6 of 501 (1.2%) farm environment samples were MRSA positive. Except for three isolates, all MRSA were classified into ST72-spa t324-SCCmec IV with PVL negative, the most predominant clonal type among community-associated MRSA in South Korea. All 35 MRSA-positive milk samples from 19 cows were obtained from a single farm (Farm G) out of 22 (4.5%) farms tested. The farm G was revisited 1 year later and milk samples were collected for examination of MRSA again. Two of six previous MRSA-positive cattle that had been kept on the farm still harbored MRSA genetically identical to MRSA strains, which were isolated from the same farm a year ago. The results of this study provide the evidence of transmission of MRSA among cattle, farm environment, and farmers and also long-term persistence of MRSA in animals.
[Show abstract][Hide abstract] ABSTRACT: A total of 84 extended-spectrum β-lactamase (ESBL)-producing Escherichia coli isolates from cattle, farm workers, and the farm environment isolated from February to September 2008 in the Republic of
Korea were investigated. All 84 ESBL-producing isolates carried blaCTX-M genes that belonged to the CTX-M-1 (n = 35) or CTX-M-9 (n = 49) family. The most predominant CTX-M type identified was CTX-M-14 (n = 49), followed by CTX-M-32 (n = 26). The blaCTX-M genes were identified most commonly in E. coli isolates from feces (n = 29), teats (n = 25), and milk (n = 14). A blaCTX-M-14 gene was also detected in an E. coli isolate from a farmer's hand. Transfer of the blaCTX-M gene from 60 blaCTX-M-positive E. coli isolates to the recipient E. coli J53 strain by conjugation was demonstrated. Plasmid isolation from blaCTX-M-positive transconjugants revealed a large (95- to 140-kb) conjugative plasmid. Almost all (82/84) blaCTX-M genes possessed an insertion sequence, ISEcp1, upstream of the blaCTX-M gene. Only in the case of the CTX-M-14 genes was IS903 downstream of the gene. The blaCTX-M genes were associated with seven kinds of addiction systems. Among them, pndAC, hok-sok, and srnBC were the most frequently identified addiction systems in both wild strains and transconjugants. The spread of blaCTX-M genes was attributed to both clonal expansion and horizontal dissemination. Our data suggest that a combination of multiple
addiction systems in plasmids carrying blaCTX-M genes could contribute to their maintenance in the host cells. To our knowledge, the blaCTX-M-32 gene has not previously been reported in animal isolates from the Republic of Korea.
[Show abstract][Hide abstract] ABSTRACT: To develop a live vaccine candidate using an attenuated strain of Salmonella Typhimurium (ST), biochemical properties, plasmid profile, PFGE patterns and pathogenic analysis of the ST isolate were carried out after sequential passage of the ST isolate in porcine neutrophils. By the passage, the ability of the neutrophil-adapted isolate to utilize d-xylose was lost, while the ability of the strain to ferment trehalose was delayed after 2 or more days of the culture. Also, changes including deletion of the gene fragments were observed in PFGE analysis of the neutrophil-adapted isolates. Two plasmids, 105kb and 50kb, were cured in the strain passaged over 15 times in porcine neutrophils. The 50% of lethal dose () of the parent strain was changed from to by the passage in intraperitoneal injection of the strains into mice. These results suggested that bacterial genotypic and phenotypic responses might be globally altered depending on the inside environment of neutrophils.
Korean Journal of Veterinary Research 03/2013; 53(1). DOI:10.14405/kjvr.2013.53.1.029
[Show abstract][Hide abstract] ABSTRACT: Abstract The purpose of this study was to determine the prevalence and characteristics of CTX-M β-lactamases in Escherichia coli among healthy swine and cattle in Korea. A total of 1212 fecal samples obtained from healthy pigs (n=558) and cattle (n=654) were screened for CTX-M-type extended spectrum β-lactamase (ESBL)-producing E. coli isolates. One hundred and twenty-one E. coli that produced ESBL were subjected to phenotypic and genotypic characterization. A high number (120/558, 21.5%) of swine fecal samples showed the presence of CTX-M β-lactamase-producing E. coli compared to cattle samples (1/654, 0.2%). The most predominant CTX-M-type identified was CTX-M-14 (n=82), followed by CTX-M-15 (n=16). Isolates producing CTX-M-3, CTX-M-27, CTX-M-55, and CTX-M-65 were also identified. Overall, the bla(TEM-1) gene was associated with CTX-M β-lactamase in 55 E. coli isolates. Transfer of bla(CTX-M) gene was demonstrated from 76 out of 121 bla(CTX-M)-positive E. coli isolates to the recipient E. coli J53 by conjugation. Plasmid DNA isolation from the transconjugants revealed a large (90-120 Kb) conjugative plasmid. ISEcp1 and IS903 were detected upstream and downstream of bla(CTX-M) genes in 117 and 91 E. coli isolates, respectively. Our results demonstrated that a combination of clonal expansion and horizontal transmission is spreading bla(CTX-M) genes among swine E. coli. The horizontal dissemination of bla(CTX-M) genes among E. coli was mostly mediated by IncF or IncI1-Iγ plasmids. To the best of our knowledge, this study represents the first report of CTX-M-3, CTX-M-27, CTX-M-55, and CTX-M-65 β-lactamases in bacterial isolates from food animals in Korea. This study revealed that the CTX-M β-lactamase-producing E. coli are widely disseminated among healthy pigs but very rare in cattle in Korea. Increasing prevalence of bla(CTX-M) genes in intestinal E. coli of food animals is a matter of concern and should be carefully monitored.
[Show abstract][Hide abstract] ABSTRACT: The aim of this study was to investigate the prevalence of plasmid-mediated quinolone resistance (PMQR) determinants in Escherichia coli isolated from food-producing animals and to characterize the PMQR-positive isolates. A total of 365 E. coli isolates which were either nalidixic acid resistant and ciprofloxacin susceptible (NALR-CIPS; n=185), or nalidixic acid and ciprofloxacin resistant (NALR-CIPR; n=180) were assessed for the presence of PMQR determinants by polymerase chain reaction. PMQR-positive isolates were further characterized by mutation analysis within the quinolone resistance-determining region (QRDR) of gyrA, gyrB, parC, and parE, phylogenetic group analysis, and pulsed-field gel electrophoresis (PFGE). Fourteen NALR-CIPS (n=8) and NALR-CIP R (n=6) E. coli isolates were positive for PMQR genes. Among them, qnrB4, qnrS1, and aac(6')-Ib-cr genes were detected in two (0.5%), eight (2.2%), and four (1.1%) isolates, respectively. None of the isolates harbored qnrA, qnrC, qnrD, and qepA genes. All but one PMQR-positive isolates harbored one or more point mutations in the QRDR of gyrA, and five of these isolates had additional mutations in the parC gene. Furthermore, one isolate each had additional substitutions in gyrB and parE genes, respectively. The most prevalent mutation was Ser83-Leu within the QRDR of gyrA. Phylogenetic analysis identified three major phylogenetic lineages, with phylogroups A (n=7) and D (n=4) being the most common phylogroups. None of the isolates belonged to virulent phylogroup B2. PFGE demonstrated that a combination of clonal and horizontal gene transmission is disseminating PMQR genes among the veterinary E. coli isolates in Korea. To our knowledge, this is the first report of occurrence of qnrB, qnrS, and aac(6')-Ib-cr genes in E. coli isolated from food-producing animals in Korea. Isolation of PMQR genes from food animals is a matter of concern since they could be transmitted to humans via food animals.
[Show abstract][Hide abstract] ABSTRACT: This study was performed to investigate the prevalence of rectal colonization with multidrug-resistant Escherichia coli in dogs hospitalized at veterinary hospitals in Korea and to assess the molecular epidemiologic traits of this organism. A total of 63 unique E. coli isolates obtained from the rectal swabs of hospitalized dogs were analyzed. Genes encoding CTX-M extended-spectrum β-lactamases (ESBLs) and AmpC enzymes were detected in 21 (33.3%) and 15 (23.8%) canine E. coli isolates, respectively. Twelve canine E. coli isolates harbored both the genes encoding the CTX-M and AmpC enzymes. Six ESBL-producing E. coli isolates also carried the rmtB gene. All 24 E. coli isolates producing CTX-M ESBL and/or CMY-2 were resistant to ciprofloxacin. Furthermore, mutations were found in the gyrA and the parC genes. In most cases, the bla genes of the CTX-M ESBL and AmpC enzymes and the rmtB gene were localized to incompatibility group F (IncF) plasmids. Possible small clonal outbreaks are suggested because some E. coli isolates recovered in the same veterinary hospital were identified as identical sequence types and showed identical banding patterns in repetitive sequence-based polymerase chain reaction. The horizontal transfer of IncF plasmids and the clonal transfer of E. coli strains are suggested to play a role in the dissemination of antimicrobial resistance genes, and this transfer may occur across host species (i.e., between humans and dogs).
[Show abstract][Hide abstract] ABSTRACT: Rabbits are highly susceptible to colibacillosis, and no treatment is able to control the disease effectively. Rabbits raised in a farm in Chonbuk province presenting persistent diarrhea and death were submitted for diagnosis. Ninety percent of the infected animals died; weanlings suffered the most mortality. Necropsies showed prominent hemorrhagic foci along the intestinal and cecal serosae. In histopathological examination, rod-shaped bacteria were observed in the necrotic areas of the tips of villi in the small intestine and neutrophils infiltration was found around the necrotic villous areas. The affected animals consistently yielded Escherichia coli isolates from the intestines. The isolated organism was atypically indole-negative and was nonserotypable using 62 known O group-typing sera. Further microbiological and epidemiological works to recognize and control colibacillosis infection in farmed rabbits in Korea is therefore critical.
[Show abstract][Hide abstract] ABSTRACT: A total of 47 extended-spectrum-cephalosporin-resistant Escherichia coli strains isolated from stray dogs in 2006 and 2007 in the Republic of Korea were investigated using molecular methods. Extended-spectrum β-lactamase (ESBL) and AmpC β-lactamase phenotypes were identified in 12 and 23 E. coli isolates, respectively. All 12 ESBL-producing isolates carried bla(CTX-M) genes. The most common CTX-M types were CTX-M-14 (n = 5) and CTX-M-24 (n = 3). Isolates producing CTX-M-3, CTX-M-55, CTX-M-27, and CTX-M-65 were also identified. Twenty-one of 23 AmpC β-lactamase-producing isolates were found to carry bla(CMY-2) genes. TEM-1 was associated with CTX-M and CMY-2 β-lactamases in 4 and 15 isolates, respectively. In addition to bla(TEM-1), two isolates carried bla(DHA-1), and one of them cocarried bla(CMY-2). Both CTX-M and CMY-2 genes were located on large (40 to 170 kb) conjugative plasmids that contained the insertion sequence ISEcp1 upstream of the bla genes. Only in the case of CTX-M genes was there an IS903 sequence downstream of the gene. The spread of ESBLs and AmpC β-lactamases occurred via both horizontal gene transfer, accounting for much of the CTX-M gene dissemination, and clonal spread, accounting for CMY-2 gene dissemination. The horizontal dissemination of bla(CTX-M) and bla(CMY-2) genes was mediated by IncF and IncI1-Iγ plasmids, respectively. The clonal spread of bla(CMY-2) was driven mainly by E. coli strains of virulent phylogroup D lineage ST648. To our knowledge, this is the first report of bla(DHA-1) in E. coli strains isolated from companion animals. This study also represents the first report of CMY-2 β-lactamase-producing E. coli isolates from dogs in the Republic of Korea.
[Show abstract][Hide abstract] ABSTRACT: The emergence of non-typhoidal Salmonella (NTS) with decreased susceptibilities to fluoroquinolone, ampicillin, or ceftriaxone has been reported worldwide. However, current surveillance studies of resistance among NTS in Korea are limited. Thus, the antimicrobial susceptibilities; resistance mechanisms such as extended-spectrum β-lactamase (ESBL), plasmid-mediated AmpC β-lactamase (PABL), and plasmid-mediated quinolone resistance (PMQR); and molecular epidemiologic characteristics were investigated in the present study.