Prevalence and characterization of Salmonella in pigs from conventional and organic farms and first report of S. serovar 1,4,[5],12:i:- from Korea

Tamang, M.D.,Gurung, M.,Nam, H.M.,Moon, D.C.,Kim, S.R.,Jang, G.C.,Jung, D.Y.,Jung, S.C.,Park, Y.H.,Lim, S.K. Elsevier Scientific Pub. Co 2015 Veterinary microbiology Vol.178 No.1

<P>This study compared the prevalence of Salmonella spp. and their antimicrobial susceptibilities in pigs from conventional and organic farms during 2012-2013 in Korea and characterized them by molecular methods. Altogether, 100 nontyphoid Salmonella were isolated: 47 from 1324 pigs (3.5%) from conventional farms and 53 from 641 pigs (8.3%) from organic farms. The most frequent serovar was Typhimurium (49%) followed by Panama (24%), 1,4,[5],12:i:- (5%), and Virchow (5%). Overall, the isolates were most often resistant to tetracycline (75%) followed by ampicillin (66%), streptomycin (57%), and gentamicin (44%). The prevalence of antimicrobial resistance, multi-drug resistance phenotype, and resistance to tetracycline, ampicillin, and gentamicin were significantly higher in swine Salmonella from conventional farms than those from organic farms. The most common resistance pattern was ampicillin-gentamicin-tetracycline (n = 16). All eight ceftiofur-resistant Salmonella identified produced CTX-M-15. Overall, decreased susceptibility to ciprofloxacin was observed in 39 isolates. Among them, a single isolate was positive for qnrS1 gene. An insertion sequence ISEcp1 was detected upstream of bla(CTX-M) gene in all isolates. The spread of bla(CTX-M-15) gene was attributed to combination of clonal expansion and horizontal dissemination mediated by IncHI2 plasmid. Multilocus variable number of tandem repeats analysis demonstrated clonal dissemination of S. Typhimurium and S. 1,4,[5],12:i:- strains in pigs. To our knowledge, this is the first report of bla(CTX-M-15) gene in S. Virchow from pigs and qnrS1 gene in S. Rissen from animals. This study also reports the first occurrence of Salmonella serovar 1,4,[5],12:i:- from Korea and CTX-M-15 producing Salmonella from pigs in Korea. (C) 2015 Elsevier B.V. All rights reserved.</P>

Detection of novel oxazolidinone and phenicol resistance gene <i>optrA</i> in enterococcal isolates from food animals and animal carcasses

Tamang, Migma Dorji,Moon, Dong Chan,Kim, Su-Ran,Kang, Hee Young,Lee, Kichan,Nam, Hyang-Mi,Jang, Geum-Chan,Lee, Hee-Soo,Jung, Suk-Chan,Lim, Suk-Kyung Elsevier 2017 Veterinary microbiology Vol.201 No.-

<P><B>Abstract</B></P> <P>Altogether 7720 <I>Enterococcus faecalis</I> and 3939 <I>E</I>. <I>faecium</I> isolated from food animals and animal carcasses during 2003–2014 in Korea were investigated to determine if linezolid-resistant (LR) enterococci (≥8μg/ml) are present. Overall, 12 <I>E</I>. <I>faecalis</I> and 27 <I>E</I>. <I>faecium</I> recovered from chickens (<I>n</I> =32), pigs (<I>n</I> =6), and cattle (<I>n</I> =1) were resistant to linezolid and were further characterized using molecular methods Most LR isolates were also resistant to chloramphenicol (97.44%) and florfenicol (92.31%). Molecular analysis showed no mutations in the 23S ribosomal RNA and in the ribosomal protein L3. The <I>optrA</I> gene was found in 89.74% of the LR enterococci, including 12 <I>E</I>. <I>faecalis</I> and 23 <I>E</I>. <I>faecium</I> isolates. Among them, 30 <I>optrA</I>-positive isolates co-carried phenicol exporter gene <I>fexA</I>. Seven LR <I>E. faecium</I> isolates had Asn130Lys mutations in the ribosomal protein L4, of which six also carried <I>optrA</I> gene. None of the isolates carried the mutliresistance gene <I>cfr</I>. Transfer of <I>optrA</I> gene was observed in 16 of the 35 <I>optrA</I>-positive isolates by conjugation. Pulsed-field gel electrophoresis demonstrated that the vast majority of <I>Enterococcus</I> strains carrying <I>optrA</I> gene were genetically heterogeneous. Multi-locus sequence typing revealed eight novel Sequence types among <I>E</I>. <I>faecalis</I> and <I>E</I>. <I>faecium</I> strains. To our knowledge, this is the first report of <I>optrA</I> gene in isolates from cattle and animal carcasses. This is also the first report of <I>optrA</I> gene in Korea. Active surveillance of <I>optrA</I> in enterococci is urgently warranted.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Overall, 12 <I>Enterococcus faecalis</I> and 27 <I>E</I>. <I>faecium</I> were resistant to linezolid. </LI> <LI> The <I>optrA</I> gene was found in all 12 <I>E</I>. <I>faecalis</I> and 23 <I>E</I>. <I>faecium</I> isolates. </LI> <LI> Among them, 30 <I>optrA</I>-positive isolates co-carried phenicol exporter gene <I>fexA</I>. </LI> <LI> First report of <I>optrA</I> gene in isolates from cattle and animal carcasses. </LI> <LI> Fist report of <I>optrA</I> in Korea indicating the emergence of <I>optrA</I> in a new setting. </LI> </UL> </P>

Characterization of plasmids encoding CTX-M β-lactamase and their addiction systems in Escherichia coli isolates from animals

Tamang, M.D.,Gurung, M.,Kang, M.S.,Nam, H.M.,Moon, D.C.,Jang, G.C.,Jung, S.C.,Park, Y.H.,Lim, S.K. Elsevier Scientific Pub. Co 2014 Veterinary microbiology Vol.174 No.3

This study was focused on characterization of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli isolates from chickens and CTX-M associated plasmid addiction systems (PASs) in E. coli from animals using molecular methods. In total, E. coli from nine (9.0%) of the 100 chicken samples examined produced CTX-M type ESBL namely CTX-M-14 (n=4), CTX-M-15 (n=4), and CTX-M-1 (n=1). All of them harbored an additional bla<SUB>TEM-1</SUB> gene. Transfer of bla<SUB>CTX-M</SUB> gene was observed in eight out of the nine bla<SUB>CTX-M</SUB>-positive isolates by conjugation. Plasmid profiling of bla<SUB>CTX-M</SUB>-positive transconjugants revealed a high-molecular weight (95-165kb) plasmid. Pulsed-field gel electrophoresis showed that most CTX-M-producing chicken isolates were genetically diverse. Furthermore, investigation of 92 conjugation-positive E. coli strains carrying bla<SUB>CTX-M</SUB> genes from pigs (n=76), chickens (n=8), and dogs (n=8) identified 230 PASs in the parental strains and 118 in their transconjugants. Among them, hok-sok, pemKI, and pndAC were the most frequently represented PASs in both the parental strains and the transconjugants. Moreover, the hok-sok and pemKI systems were strongly associated to IncF plasmids and the pndAC system to IncI1-Iγ plasmids. Our results suggest that the rapid spread of CTX-M genes in E. coli isolates among the animals could be attributed to the presence of multiple PASs in the CTX-M plasmids. To our knowledge, this is the first report of characterization of CTX-M associated PASs in E. coli isolates from pigs, chickens, and dogs. In addition, CTX-M-1 was detected for the first time in Korea.

Synthesis of colloidal InSb nanocrystals <i>via in situ</i> activation of InCl₃

Tamang, Sudarsan,Kim, Kyungnam,Choi, Hyekyoung,Kim, Youngsik,Jeong, Sohee The Royal Society of Chemistry 2015 Dalton Transactions Vol.44 No.38

<P>Indium antimonide (InSb), a narrow band gap III–V semiconductor is a promising infrared-active material for various optoelectronic applications. Synthetic challenge of colloidal InSb nanocrystals (NCs) lies in the limited choice of precursors. Only a few successful synthetic schemes involving highly toxic stibine (SbH<SUB>3</SUB>) or air- and moisture-sensitive metal silylamides (In[N(Si-(Me)<SUB>3</SUB>)<SUB>2</SUB>]<SUB>3</SUB> or Sb[N(Si-(Me)<SUB>3</SUB>)<SUB>2</SUB>]<SUB>3</SUB>) as the precursor have been reported. We found that commercially available precursors InCl<SUB>3</SUB> and Sb[NMe<SUB>2</SUB>]<SUB>3</SUB> directly form highly crystalline colloidal InSb nanocrystals in the presence of a base such as LiN(SiMe<SUB>3</SUB>)<SUB>2</SUB> or <I>n</I>BuLi. The mean size of the particles can be controlled by simply changing the activating base. This approach offers a one-pot synthesis of InSb NCs from readily available chemicals without the use of complex organometallic precursors.</P> <P>Graphic Abstract</P><P>Indium antimonide (InSb), a narrow band gap III–V semiconductor is a promising infrared-active material for various optoelectronic applications. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c5dt02181b'> </P>

Antimicrobial Susceptibility and Virulence Characteristics of Salmonella enterica Typhimurium Isolates from Healthy and Diseased Pigs in Korea

TAMANG, MIGMA DORJI,GURUNG, MAMATA,NAM, HYANG-MI,MOON, DONG CHAN,JANG, GEUM-CHAN,JUNG, SUK-CHAN,LIM, SUK-KYUNG ational Association for Food Protection 2014 Journal of food protection Vol.77 No.9

<P>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 &lt; 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 &lt; 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.</P>

Prevalence and Mechanisms of Quinolone Resistance Among Selected NontyphoidSalmonellaIsolated from Food Animals and Humans in Korea

Tamang, Migma Dorji,Nam, Hyang-Mi,Kim, Aeran,Lee, Hee-Soo,Kim, Tae-Sun,Kim, Min-Ji,Jang, Geum-Chan,Jung, Suk-Chan,Lim, Suk-Kyung Mary Ann Liebert 2011 Foodborne Pathogens and Disease Vol.8 No.11

Molecular Characterization of Extended-Spectrum-β-Lactamase-Producing and Plasmid-Mediated AmpC β-Lactamase-Producing Escherichia coli Isolated from Stray Dogs in South Korea

Tamang, Migma Dorji,Nam, Hyang-Mi,Jang, Geum-Chan,Kim, Su-Ran,Chae, Myung Hwa,Jung, Suk-Chan,Byun, Jae-Won,Park, Yong Ho,Lim, Suk-Kyung American Society for Microbiology 2012 Antimicrobial Agents and Chemotherapy Vol.56 No.5

<B>ABSTRACT</B><P>A total of 47 extended-spectrum-cephalosporin-resistantEscherichia colistrains 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 23E. coliisolates, respectively. All 12 ESBL-producing isolates carried<I>bla</I>CTX-Mgenes. The most common CTX-M types were CTX-M-14 (<I>n</I>= 5) and CTX-M-24 (<I>n</I>= 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<I>bla</I>CMY-2genes. TEM-1 was associated with CTX-M and CMY-2 β-lactamases in 4 and 15 isolates, respectively. In addition to<I>bla</I>TEM-1, two isolates carried<I>bla</I>DHA-1, and one of them cocarried<I>bla</I>CMY-2. Both CTX-M and CMY-2 genes were located on large (40 to 170 kb) conjugative plasmids that contained the insertion sequence IS<I>Ecp1</I>upstream of the<I>bla</I>genes. Only in the case of CTX-M genes was there an IS<I>903</I>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<I>bla</I>CTX-Mand<I>bla</I>CMY-2genes was mediated by IncF and IncI1-Iγ plasmids, respectively. The clonal spread of<I>bla</I>CMY-2was driven mainly byE. colistrains of virulent phylogroup D lineage ST648. To our knowledge, this is the first report of<I>bla</I>DHA-1inE. colistrains isolated from companion animals. This study also represents the first report of CMY-2 β-lactamase-producingE. coliisolates from dogs in the Republic of Korea.</P>

Short communication: Genetic characterization of antimicrobial resistance in Acinetobacter isolates recovered from bulk tank milk

Tamang, M.D.,Gurung, M.,Nam, H.M.,Kim, S.R.,Jang, G.C.,Jung, S.C.,Lim, S.K. American Dairy Science Association 2014 Journal of dairy science Vol.97 No.2

A total of 176 Acinetobacter isolates, including 57 Acinetobacter baumannii originally obtained from 2,287 bulk tank milk (BTM) samples in Korea was investigated for the genetic basis of antimicrobial resistance using molecular methods. In addition, the occurrence and cassette content of integrons were examined and the genetic diversity of A. baumannii strains identified was evaluated. Aminoglycoside-modifying enzyme genes were detected in 15 (88.2%) of the 17 aminoglycoside-resistant Acinetobacter isolates tested. The most common aminoglycoside-modifying enzyme gene identified was adenylyltransferase gene aadB (n=9), followed by phosphotransferase genes aphA6 (n=7) and aphA1 (n=5). Of the 31 isolates resistant to tetracycline, tet(39) was detected in 20 of them. The genetic basis of resistance to sulfonamide was identified in 15 (53.6%) of 28 trimethoprim-sulfamethoxazole-resistant isolates and 9 (32.1%) of them carried both sul1 and sul2 genes. A bla<SUB>ADC-7-like</SUB> gene was detected in 1 β-lactam-resistant A. baumannii. Furthermore, class 1 integron was identified in 11 Acinetobacter isolates. Two gene cassettes dfrA15, conferring resistance to trimethoprim, and aadA2, conferring resistance to aminoglycosides, were identified in 8 Acinetobacter isolates. None of the isolates was positive for class 2 or class 3 integrons. Pulsed-field gel electrophoresis revealed that most of the A. baumannii strains from BTM samples were genetically diverse, indicating that the occurrence of A. baumannii strains in BTM was not the result of dissemination of a single clone. Elucidation of resistance mechanisms associated with the resistance phenotype and a better understanding of resistance genes may help in the development of strategies to control infections, such as mastitis, and to prevent further dissemination of antibiotic resistance genes. To the best of our knowledge, this is the first report of molecular characterization of antimicrobial-resistant Acinetobacter spp. from milk.

Molecular Characterization of CTX-M β-Lactamase and Associated Addiction Systems in <i>Escherichia coli</i> Circulating among Cattle, Farm Workers, and the Farm Environment

Tamang, Migma Dorji,Nam, Hyang-Mi,Gurung, Mamata,Jang, Geum-Chan,Kim, Su-Ran,Jung, Suk-Chan,Park, Yong Ho,Lim, Suk-Kyung American Society for Microbiology 2013 Applied and environmental microbiology Vol.79 No.13

<P>A total of 84 extended-spectrum β-lactamase (ESBL)-producing <I>Escherichia coli</I> 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 <I>bla</I><SUB>CTX-M</SUB> genes that belonged to the CTX-M-1 (<I>n</I> = 35) or CTX-M-9 (<I>n</I> = 49) family. The most predominant CTX-M type identified was CTX-M-14 (<I>n</I> = 49), followed by CTX-M-32 (<I>n</I> = 26). The <I>bla</I><SUB>CTX-M</SUB> genes were identified most commonly in <I>E. coli</I> isolates from feces (<I>n</I> = 29), teats (<I>n</I> = 25), and milk (<I>n</I> = 14). A <I>bla</I><SUB>CTX-M-14</SUB> gene was also detected in an <I>E. coli</I> isolate from a farmer's hand. Transfer of the <I>bla</I><SUB>CTX-M</SUB> gene from 60 <I>bla</I><SUB>CTX-M</SUB>-positive <I>E. coli</I> isolates to the recipient <I>E. coli</I> J53 strain by conjugation was demonstrated. Plasmid isolation from <I>bla</I><SUB>CTX-M</SUB>-positive transconjugants revealed a large (95- to 140-kb) conjugative plasmid. Almost all (82/84) <I>bla</I><SUB>CTX-M</SUB> genes possessed an insertion sequence, IS<I>Ecp1</I>, upstream of the <I>bla</I><SUB>CTX-M</SUB> gene. Only in the case of the CTX-M-14 genes was IS<I>903</I> downstream of the gene. The <I>bla</I><SUB>CTX-M</SUB> genes were associated with seven kinds of addiction systems. Among them, <I>pndAC</I>, <I>hok-sok</I>, and <I>srnBC</I> were the most frequently identified addiction systems in both wild strains and transconjugants. The spread of <I>bla</I><SUB>CTX-M</SUB> genes was attributed to both clonal expansion and horizontal dissemination. Our data suggest that a combination of multiple addiction systems in plasmids carrying <I>bla</I><SUB>CTX-M</SUB> genes could contribute to their maintenance in the host cells. To our knowledge, the <I>bla</I><SUB>CTX-M-32</SUB> gene has not previously been reported in animal isolates from the Republic of Korea.</P>

Emergence of Extended-Spectrum β -Lactamase (CTX-M-15 and CTX-M-14)-Producing Nontyphoid Salmonella with Reduced Susceptibility to Ciprofloxacin among Food Animals and Humans in Korea

Tamang, M.D.,Nam, H.-M.,Kim, T.-S.,Jang, G.-C.,Jung, S.-C.,Lim, S.-K. AMERICAN SOCIETY FOR MICROBIOLOGY 2011 Journal of clinical microbiology Vol.49 No.7