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Antimicrobial susceptibility and occurrence of resistance genes among Salmonella enterica serovar Weltevreden from different countries

Aarestrup FM, Lertworapreecha M, Evans MC, Bangtrakulnonth A, Chalermchaikit T, Hendriksen RS, et al.

J Antimicrob Chemother, 2003 Oct;52(4):715-8.
PMID: 12972453

This study was conducted to investigate the occurrence of antimicrobial resistance among Salmonella Weltevreden isolates from different sources in South-East Asia (Indonesia, Laos, Malaysia, Taiwan, Thailand, Vietnam), Australia, Denmark, New Zealand and the USA.

Matched MeSH terms: Salmonella enterica/genetics*
Fulltext Overview of Molecular Typing Tools for The Characterization of Salmonella enterica in Malaysia

Ngoi ST, Teh CS, Chai LC, Thong KL

Biomed Environ Sci, 2015 Oct;28(10):751-64.
PMID: 26582097 DOI: 10.3967/bes2015.105
Matched MeSH terms: Salmonella enterica/genetics*
Fulltext Mechanisms of resistance in nontyphoidal Salmonella enterica strains exhibiting a nonclassical quinolone resistance phenotype

Gunell M, Webber MA, Kotilainen P, Lilly AJ, Caddick JM, Jalava J, et al.

Antimicrob Agents Chemother, 2009 Sep;53(9):3832-6.
PMID: 19596880 DOI: 10.1128/AAC.00121-09

Nontyphoidal Salmonella enterica strains with a nonclassical quinolone resistance phenotype were isolated from patients returning from Thailand or Malaysia to Finland. A total of 10 isolates of seven serovars were studied in detail, all of which had reduced susceptibility (MIC > or = 0.125 microg/ml) to ciprofloxacin but were either susceptible or showed only low-level resistance (MIC < or = 32 microg/ml) to nalidixic acid. Phenotypic characterization included susceptibility testing by the agar dilution method and investigation of efflux activity. Genotypic characterization included the screening of mutations in the quinolone resistance-determining regions (QRDR) of gyrA, gyrB, parC, and parE by PCR and denaturing high-pressure liquid chromatography and the amplification of plasmid-mediated quinolone resistance (PMQR) genes qnrA, qnrB, qnrS, qnrD, aac(6')-Ib-cr, and qepA by PCR. PMQR was confirmed by plasmid analysis, Southern hybridization, and plasmid transfer. No mutations in the QRDRs of gyrA, gyrB, parC, or parE were detected with the exception of a Thr57-Ser substitution within ParC seen in all but the S. enterica serovar Typhimurium strains. The qnrA and qnrS genes were the only PMQR determinants detected. Plasmids carrying qnr alleles were transferable in vitro, and the resistance phenotype was reproducible in Escherichia coli DH5alpha transformants. These data demonstrate the emergence of a highly mobile qnr genotype that, in the absence of mutation within topoisomerase genes, confers the nontypical quinolone resistance phenotype in S. enterica isolates. The qnr resistance mechanism enables bacteria to survive elevated quinolone concentrations, and therefore, strains carrying qnr alleles may be able to expand during fluoroquinolone treatment. This is of concern since nonclassical quinolone resistance is plasmid mediated and therefore mobilizable.

Matched MeSH terms: Salmonella enterica/genetics*
Draft genome sequence of multidrug-resistant Salmonella enterica serovar Brancaster strain PS01 isolated from chicken meat, Malaysia

Chin PS, Yu CY, Ang GY, Yin WF, Chan KG

J Glob Antimicrob Resist, 2017 06;9:41-42.
PMID: 28300643 DOI: 10.1016/j.jgar.2016.12.017

OBJECTIVES: Salmonella spp. represent one of the main diarrhoeal pathogens that are transmitted via the food supply chain. Here we report the draft genome sequence of a multidrug-resistant Salmonella enterica serovar Brancaster (PS01) that was isolated from poultry meat in Malaysia.
METHODS: Genomic DNA was extracted from Salmonella strain PS01 and was sequenced using an Illumina HiSeq 2000 platform. The generated reads were de novo assembled using CLC Genomics Workbench. The draft genome was annotated and the presence of antimicrobial resistance genes was identified.
RESULTS: The 5 036 442bp genome contains various antimicrobial resistance genes conferring resistance to aminoglycosides, fluoroquinolones, fosfomycin, macrolides, phenicols, sulphonamides, tetracyclines and trimethoprim. The β-lactamase gene blaTEM-176 encoding TEM-176 was also found in this strain.
CONCLUSIONS: The genome sequence will aid in the understanding of drug resistance mechanisms in foodborne Salmonella Brancaster and highlights the need to ensure the judicious use of antibiotics in animal husbandry as well as the importance of implementing proper food handling and preparation practices.

Matched MeSH terms: Salmonella enterica/genetics*
High Phenotypic Variability among Representative Strains of Common Salmonella enterica Serovars with Possible Implications for Food Safety

Abdullah WZW, Mackey BM, Karatzas KAG

J Food Prot, 2018 Jan;81(1):93-104.
PMID: 29271685 DOI: 10.4315/0362-028X.JFP-17-190

Salmonella is an important foodborne pathogen, whose ability to resist stress and survive can vary among strains. This variability is normally not taken into account when predictions are made about survival in foods with negative consequences. Therefore, we examined the contribution of variable phenotypic properties to survival under stress in 10 Salmonella serovars. One strain (Typhimurium 10) was intentionally RpoS-negative; however, another strain (Heidelberg) showed an rpoS mutation, rendering it inactive. We assessed an array of characteristics (motility, biofilm formation, bile resistance, acid resistance, and colony morphology) that show major variability among strains associated with a 10- to 19-fold difference between the highest and the lowest strain for most characteristics. The RpoS status of isolates did not affect variability in the characteristics, with the exception of resistance to NaCl, acetic acid, lactic acid, and the combination of acetic acid and salt, where the variability between the highest and the lowest strain was reduced to 3.1-fold, 1.7-fold, 2-fold, and 1.7-fold, respectively, showing that variability was significant among RpoS-positive strains. Furthermore, we also found a good correlation between acid resistance and lysine decarboxylase activity, showing its importance for acid resistance, and demonstrated a possible role of RpoS in the lysine decarboxylase activity in Salmonella.

Matched MeSH terms: Salmonella enterica/genetics*
Fulltext High resolution melting analysis for rapid mutation screening in gyrase and Topoisomerase IV genes in quinolone-resistant Salmonella enterica

Ngoi ST, Thong KL

Biomed Res Int, 2014;2014:718084.
PMID: 25371903 DOI: 10.1155/2014/718084

The increased Salmonella resistance to quinolones and fluoroquinolones is a public health concern in the Southeast Asian region. The objective of this study is to develop a high resolution melt curve (HRM) assay to rapidly screen for mutations in quinolone-resistant determining region (QRDR) of gyrase and topoisomerase IV genes. DNA sequencing was performed on 62 Salmonella strains to identify mutations in the QRDR of gyrA, gyrB, parC, and parE genes. Mutations were detected in QRDR of gyrA (n = 52; S83F, S83Y, S83I, D87G, D87Y, and D87N) and parE (n = 1; M438I). Salmonella strains with mutations within QRDR of gyrA are generally more resistant to nalidixic acid (MIC 16 > 256 μg/mL). Mutations were uncommon within the QRDR of gyrB, parC, and parE genes. In the HRM assay, mutants can be distinguished from the wild-type strains based on the transition of melt curves, which is more prominent when the profiles are displayed in difference plot. In conclusion, HRM analysis allows for rapid screening for mutations at the QRDRs of gyrase and topoisomerase IV genes in Salmonella. This assay markedly reduced the sequencing effort involved in mutational studies of quinolone-resistance genes.

Matched MeSH terms: Salmonella enterica/genetics*
Application of PCR-based serogrouping of selected Salmonella serotypes in Malaysia

Lim BK, Thong KL

J Infect Dev Ctries, 2009 Jul 01;3(6):420-8.
PMID: 19762954

BACKGROUND: Differentiation of Salmonella enterica into its serogroups is important for epidemiological study. The objective of the study was to apply a multiplex PCR targeting serogroups A, B, C1, D, E and Vi-positive strains of Salmonella enterica commonly found in Malaysia. A separate H-typing multiplex PCR which identified flagellar antigen "a", "b" or "d" was also optimized to confirm clinical serotypes, S. Paratyphi A and S. Typhi.
METHODOLOGY: Sixty-seven laboratory Salmonella enterica strains were tested. Six sets of primers targeting defined regions of the O antigen synthesis genes (rfb gene cluster) and Vi antigen gene (viaB) were selected and combined into a multiplex PCR for O-grouping. Four primers (H-for, Ha-rev, Hb-rev and Hd-rev) were used in the second step multiplex PCR for H-typing. The optimized mPCR assays were further evaluated with 58 blind-coded Salmonella strains.
RESULTS: The multiplex PCR results obtained showed 100% concordance to the conventionally typed serogroups. Validation with 58 blind coded Salmonella strains yield 100% accuracy and specificity.
CONCLUSION: Based on this study, PCR serogrouping proved to be a rapid, alternative method for further differentiation of Salmonella enterica.

Matched MeSH terms: Salmonella enterica/genetics
Fulltext Dissemination of Salmonella enterica sequence types among ASEAN economic community countries

Patchanee P, Boonkhot P, Kittiwan N, Tadee P, Chotinun S

Southeast Asian J. Trop. Med. Public Health, 2015 Jul;46(4):707-19.
PMID: 26867391

Food-borne illness caused by Salmonella enterica remains a public health problem and results in economic loss worldwide. With the up-coming establish- ment of the ASEAN Economic Community (AEC) allowing unrestricted move- ment of labor and goods, there is a higher risk of pathogen transmission among the AEC countries. This study characterized and investigated the spatial and temporal associations of S. enterica strains isolated in AEC countries during 1940- 2012 compared with those isolated in northern-Thailand during 2011-2013. Of the 173 S. enterica strains examined, 68 sequence types (STs) and 32 clonal complexes (CCs) were identified by multi loci sequence typing. Twenty-one strains belonged to four sequence types new to AEC countries, and they constituted only two CCs. A number of strains originated from various countries with multiple hosts, were highlighted. There was evidence of strains circulating in the AEC region well over a decade. Such information will be important in formulating biosecurity measures, as well as in educating regarding the risk of disease transmission in AEC.

Matched MeSH terms: Salmonella enterica/genetics*
Genetic diversity of clinical and environmental strains of Salmonella enterica serotype Weltevreden isolated in Malaysia

Thong KL, Goh YL, Radu S, Noorzaleha S, Yasin R, Koh YT, et al.

J Clin Microbiol, 2002 Jul;40(7):2498-503.
PMID: 12089269

The incidence of food-borne salmonellosis due to Salmonella enterica serotype Weltevreden is reported to be on the increase in Malaysia. The pulsed-field gel electrophoresis (PFGE) subtyping method was used to assess the extent of genetic diversity and clonality of Salmonella serotype Weltevreden strains from humans and the environment. PFGE of XbaI-digested chromosomal DNA from 95 strains of Salmonella serotype Weltevreden gave 39 distinct profiles with a wide range of Dice coefficients (0.27 to 1.00), indicating that PFGE is very discriminative and that multiple clones of Salmonella serotype Weltevreden exist among clinical and environmental isolates. Strains of one dominant pulsotype (pulsotype X1/X2) appeared to be endemic in this region, as they were consistently recovered from humans with salmonellosis between 1996 and 2001 and from raw vegetables. In addition, the sharing of similar PFGE profiles among isolates from humans, vegetables, and beef provides indirect evidence of the possible transmission of salmonellosis from contaminated raw vegetables and meat to humans. Furthermore, the recurrence of PFGE profile X21 among isolates found in samples of vegetables from one wet market indicated the persistence of this clone. The environment in the wet markets may represent a major source of cross-contamination of vegetables with Salmonella serotype Weltevreden. Antibiotic sensitivity tests showed that the clinical isolates of Salmonella serotype Weltevreden remained drug sensitive but that the vegetable isolates were resistant to at least two antibiotics. To the best of our knowledge, this is the first study to compare clinical and environmental isolates of Salmonella serotype Weltevreden in Malaysia.

Matched MeSH terms: Salmonella enterica/genetics*
Pathogenicity and phenotypic analysis of sopB, sopD and pipD virulence factors in Salmonella enterica serovar typhimurium and Salmonella enterica serovar Agona

Khoo CH, Sim JH, Salleh NA, Cheah YK

Antonie Van Leeuwenhoek, 2015 Jan;107(1):23-37.
PMID: 25312847 DOI: 10.1007/s10482-014-0300-7

Salmonella is an important food-borne pathogen causing disease in humans and animals worldwide. Salmonellosis may be caused by any one of over 2,500 serovars of Salmonella. Nonetheless, Salmonella enterica serovar Typhimurium and Salmonella enterica serovar Agona are the second most prevalent serovars isolated from humans and livestock products respectively. Limited knowledge is available about the virulence mechanisms responsible for diarrheal disease caused by them. To investigate the contribution of sopB, sopD and pipD as virulence factors in intracellular infections and the uniqueness of these bacteria becoming far more prevalent than other serovars, the infection model of Caenorhabditis elegans and phenotypic microarray were used to characterize their mutants. The strains containing the mutation in sopB, sopD and pipD genes were constructed by using latest site-specific group II intron mutagenesis approach to reveal the pathogenicity of the virulence factors. Overall, we observed that the mutations in sopB, sopD and pipD genes of both serovars did not exhibit significant decrease in virulence towards the nematode. This may indicate that these virulence effectors may not be universal virulence factors involved in conserved innate immunity. There are significant phenotypic differences amongst strains carrying sopB, sopD and pipD gene mutations via the analysis of biochemical profiles of the bacteria. Interestingly, mutant strains displayed different susceptibility to chemical stressors from several distinct pharmacological and structural classes when compared to its isogenic parental strains. These metabolic and chemosensitivity assays also revealed multiple roles of Salmonella virulence factors in nutrient metabolism and antibiotic resistance.

Matched MeSH terms: Salmonella enterica/genetics
Analysis of Salmonella Agona and Salmonella Weltevreden in Malaysia by PCR fingerprinting and antibiotic resistance profiling

Learn-Han L, Yoke-Kqueen C, Salleh NA, Sukardi S, Jiun-Horng S, Chai-Hoon K, et al.

Antonie Van Leeuwenhoek, 2008 Oct;94(3):377-87.
PMID: 18548329 DOI: 10.1007/s10482-008-9254-y

Forty-eight strains of Salmonella enterica subsp. enterica serovar Agona and 33 strains of Salmonella enterica subsp. enterica serovar Weltevreden were characterized by random amplified polymorphic DNA (RAPD) fingerprinting using 3 different arbitrary primer, Enterobacterial Repetitive Intergenic Consensus-Polymerase Chain Reaction (ERIC-PCR) and antimicrobial susceptibility testing. By using RAPD, 81 strains (44 strains of S. Agona and 33 strains of S. Weltevreden) can be clustered into 14 groups and 6 single isolates whereas ERIC-PCR produced 7 clusters and 3 single isolates. Thirteen antimicrobial agents were used and all the isolates were resistant to erythromycin and showed Multiple Antimicrobial Resistance indexes, ranging from 0.08 to 0.62. Poultry still remain as the common reservoir for multi-drug-resistant Salmonella. On the other hand, vegetables contaminated with S. Weltevreden showed a gain in antimicrobial resistance. Besides that, consistent antibiograms were observed from S. Weltevreden isolated at Kajang wet market on 2000/08/02.

Matched MeSH terms: Salmonella enterica/genetics*
Structural and functional studies of a 50 kDa antigenic protein from Salmonella enterica serovar Typhi

Choong YS, Lim TS, Chew AL, Aziah I, Ismail A

J Mol Graph Model, 2011 Apr;29(6):834-42.
PMID: 21371926 DOI: 10.1016/j.jmgm.2011.01.008

The high typhoid incidence rate in developing and under-developed countries emphasizes the need for a rapid, affordable and accessible diagnostic test for effective therapy and disease management. TYPHIDOT®, a rapid dot enzyme immunoassay test for typhoid, was developed from the discovery of a ∼50 kDa protein specific for Salmonella enterica serovar Typhi. However, the structure of this antigen remains unknown till today. Studies on the structure of this antigen are important to elucidate its function, which will in turn increase the efficiency of the development and improvement of the typhoid detection test. This paper described the predictive structure and function of the antigenically specific protein. The homology modeling approach was employed to construct the three-dimensional structure of the antigen. The built structure possesses the features of TolC-like outer membrane protein. Molecular docking simulation was also performed to further probe the functionality of the antigen. Docking results showed that hexamminecobalt, Co(NH(3))(6)(3+), as an inhibitor of TolC protein, formed favorable hydrogen bonds with D368 and D371 of the antigen. The single point (D368A, D371A) and double point (D368A and D371A) mutations of the antigen showed a decrease (single point mutation) and loss (double point mutations) of binding affinity towards hexamminecobalt. The architecture features of the built model and the docking simulation reinforced and supported that this antigen is indeed the variant of outer membrane protein, TolC. As channel proteins are important for the virulence and survival of bacteria, therefore this ∼50 kDa channel protein is a good specific target for typhoid detection test.

Matched MeSH terms: Salmonella enterica/genetics
Quinolone Resistance Mechanisms Among Salmonella enterica in Malaysia

Thong KL, Ngoi ST, Chai LC, Teh CS

Microb Drug Resist, 2016 Jun;22(4):259-72.
PMID: 26683630 DOI: 10.1089/mdr.2015.0158

The prevalence of quinolone-resistant Salmonella enterica is on the rise worldwide. Salmonella enterica is one of the major foodborne pathogens in Malaysia. Therefore, we aim to investigate the occurrence and mechanisms of quinolone resistance among Salmonella strains isolated in Malaysia. A total of 283 Salmonella strains isolated from food, humans, and animals were studied. The disk diffusion method was used to examine the quinolone susceptibility of the strains, and the minimum inhibitory concentration (MIC) values of nalidixic acid and ciprofloxacin were also determined. DNA sequencing of the quinolone resistance-determining regions (QRDRs) of gyrase and topoisomerase IV genes and the plasmid-borne qnr genes was performed. The transfer of the qnr gene was examined through transconjugation experiment. A total of 101 nalidixic acid-resistant Salmonella strains were identified. In general, all strains were highly resistant to nalidixic acid (average MICNAL, 170 μg/ml). Resistance to ciprofloxacin was observed in 30.7% of the strains (1 ≤ MICCIP ≤ 2 μg/ml). Majority of the strains contained missense mutations in the QRDR of gyrA (69.3%). Silent mutations were frequently detected in gyrB (75.2%), parC (27.7%), and parE (51.5%) within and beyond the QRDRs. Novel mutations were detected in parC and parE. The plasmid-borne qnrS1 variant was found in 36.6% of the strains, and two strains were found to be able to transfer the qnrS1 gene. Overall, mutations in gyrA and the presence of qnrS1 genes might have contributed to the high level of quinolone resistance among the strains. Our study provided a better understanding on the status of quinolone resistance among Salmonella strains circulating in Malaysia.

Matched MeSH terms: Salmonella enterica/genetics

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