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>

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.

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.

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

Optimization of stir casting process parameter using response surface meth odology

Senthilkumar KM,Sivakumar A,Rohokale Milind Shivaji,S.K. Tamang,Giriraj M 한양대학교 세라믹연구소 2022 Journal of Ceramic Processing Research Vol.23 No.2

Response surface methodology is used to optimize the stir casting process parameters for the aluminium metal matrixcomposite reinforced with boron carbide with several weight percentages. The stir casting process parameters used in thiswork are the weight percentage of the reinforcing element, stir casting mixing time and particle size of the reinforcing elementused in the fabrication of the metal matrix composite. The levels are chosen and central composite design is implemented tooptimize the tensile strength of the metal matrix composite. The analysis of variance is calculated and the estimated regressioncoefficients for the tensile strength are obtained. Also the residual plots and the contour plots are plotted and discussed here.

Prevalence and antimicrobial susceptibility of Acinetobacter from raw bulk tank milk in Korea

Gurung, M.,Nam, H.M.,Tamang, M.D.,Chae, M.H.,Jang, G.C.,Jung, S.C.,Lim, S.K. American Dairy Science Association 2013 Journal of dairy science Vol.96 No.4

The objective of this study was to determine the prevalence of Acinetobacter spp. in bulk tank milk (BTM) samples from different provinces of Korea and to analyze their antimicrobial susceptibility. Altogether, 2,287 BTM samples were investigated. Among them, Acinetobacter spp. were isolated from 176 BTM samples. Out of 176 Acinetobacter spp., 57 isolates were identified as Acinetobacter baumannii. None of the isolates were resistant to cefepime, imipenem, meropenem, ciprofloxacin, levofloxacin, or colistin. Resistance to amikacin, gentamicin, piperacillin, and cefotaxime was 2.3, 7.4, 2.3, and 4.0%, respectively. Acinetobacter spp. were least susceptible to tetracycline (17.6%), followed by trimethoprim-sulfamethoxazole (15.9%), ceftazidime (10.8%), and ampicillin-sulbactam (10.2%). Overall, A. baumannii strains were susceptible to most of the antimicrobial agents tested compared with other Acinetobacter spp. The Acinetobacter isolates showed 17 different patterns of antimicrobial resistance. The most frequent resistance profile observed was ampicillin-sulbactam (n=13), followed by tetracycline (n=9), ceftazidime-tetracycline (n=8), and trimethoprim-sulfamethoxazole-tetracycline (n=8). The results of this study confirmed that Acinetobacter, including A. baumannii strains, are present in BTM, which clearly showed the importance of examining BTM not only for foodborne pathogens but also for Acinetobacter spp., which could be of public health concern. To the best of our knowledge, this is the first report of Acinetobacter spp. in BTM samples from Korea.