Displaying publications 21 - 40 of 50 in total

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  1. 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: Drug Resistance, Bacterial/genetics*
  2. Enterobacteriaceae resistant to third-generation cephalosporins and quinolones in fresh culinary herbs imported from Southeast Asia
    Veldman K, Kant A, Dierikx C, van Essen-Zandbergen A, Wit B, Mevius D
    Int J Food Microbiol, 2014 May 2;177:72-7.
    PMID: 24607424 DOI: 10.1016/j.ijfoodmicro.2014.02.014
    Since multidrug resistant bacteria are frequently reported from Southeast Asia, our study focused on the occurrence of ESBL-producing Enterobacteriaceae in fresh imported herbs from Thailand, Vietnam and Malaysia. Samples were collected from fresh culinary herbs imported from Southeast Asia in which ESBL-suspected isolates were obtained by selective culturing. Analysis included identification by MALDI-TOF mass spectrometry, susceptibility testing, XbaI-PFGE, microarray, PCR and sequencing of specific ESBL genes, PCR based replicon typing (PBRT) of plasmids and Southern blot hybridization. In addition, the quinolone resistance genotype was characterized by screening for plasmid mediated quinolone resistance (PMQR) genes and mutations in the quinolone resistance determining region (QRDR) of gyrA and parC. The study encompassed fifty samples of ten batches of culinary herbs (5 samples per batch) comprising nine different herb variants. The herbs originated from Thailand (Water morning glory, Acacia and Betel leaf), Vietnam (Parsley, Asian pennywort, Houttuynia leaf and Mint) and Malaysia (Holy basil and Parsley). By selective culturing 21 cefotaxime resistant Enterobacteriaceae were retrieved. Array analysis revealed 18 isolates with ESBL genes and one isolate with solely non-ESBL beta-lactamase genes. Mutations in the ampC promoter region were determined in two isolates with PCR and sequencing. The isolates were identified as Klebsiella pneumoniae (n=9), Escherichia coli (n=6), Enterobacter cloacae complex (n=5) and Enterobacter spp. (n=1). All isolates tested were multidrug resistant. Variants of CTX-M enzymes were predominantly found followed by SHV enzymes. PMQR genes (including aac(6')-1b-cr, qnrB and qnrS) were also frequently detected. In almost all cases ESBL and quinolone resistance genes were located on the same plasmid. Imported fresh culinary herbs from Southeast Asia are a potential source for contamination of food with multidrug resistant bacteria. Because these herbs are consumed without appropriate heating, transfer to human bacteria cannot be excluded.
    Matched MeSH terms: Drug Resistance, Bacterial/genetics*
  3. Molecular characterization showed limited genetic diversity among Salmonella Enteritidis isolated from humans and animals in Malaysia
    Ngoi ST, Thong KL
    Diagn Microbiol Infect Dis, 2013 Dec;77(4):304-11.
    PMID: 24139970 DOI: 10.1016/j.diagmicrobio.2013.09.004
    Salmonella enterica serovar Enteritidis (S. Enteritidis) is the most common causative agent of non-typhoidal salmonellosis in Malaysia. We aimed to characterize S. Enteritidis isolated from humans and animals by analyzing their antimicrobial resistance profiles and genotypes. A total of 111 strains were characterized using multiple-locus variable-number tandem repeat analysis, pulsed-field gel electrophoresis, and antimicrobial susceptibility testing. Both typing methods revealed that genetically similar S. Enteritidis strains had persisted among human and animal populations within the period of study (2003-2008). Only 39% of the strains were multi-drug resistant (i.e., resistant to 3 or more classes of antimicrobial agents), with a majority (73%) of these in low-risk phase (multiple antibiotic resistant index <0.20). Limited genetic diversity among clinical and zoonotic S. Enteritidis suggested that animals are possible sources of human salmonellosis. The degree of multi-drug resistance among the strains was generally low during the study period.
    Matched MeSH terms: Drug Resistance, Bacterial/genetics
  4. Fulltext Phenotypic detection of metallo-β-lactamase in imipenem-resistant Pseudomonas aeruginosa
    Khosravi Y, Loke MF, Chua EG, Tay ST, Vadivelu J
    ScientificWorldJournal, 2012;2012:654939.
    PMID: 22792048 DOI: 10.1100/2012/654939
    Carbapenems are the primary choice of treatment for severe Pseudomonas aeruginosa infection. However, the emergence of carbapenem resistance due to the production of metallo-β-lactamases (MBLs) is of global concern. In this study, 90 imipenem- (IPM- or IP-) resistant P. aeruginosa (IRPA) isolates, including 32 previously tested positive and genotyped for MBL genes by PCR, were subjected to double-disk synergy test (DDST), combined disk test (CDT), and imipenem/imipenem-inhibitor (IP/IPI) E-test to evaluate their MBLs detection capability. All three methods were shown to have a sensitivity of 100%. However, DDST was the most specific of the three (96.6%), followed by IP/IPI E-test interpreted based on the single criteria of IP/IPI ≥8 as positive (62.1%), and CDT was the least specific (43.1%). Based on the data from this evaluation, we propose that only IRPA with IP MIC >16 μg/mL and IP/IPI ≥8 by IP/IPI E-test should be taken as positive for MBL activity. With the new dual interpretation criteria, the MBL IP/IPI E-test was shown to achieve 100% sensitivity as well as specificity for the IRPA in this study. Therefore, the IP/IPI E-test is a viable alternative phenotypic assay to detect MBL production in IRPA in our population in circumstances where PCR detection is not a feasible option.
    Matched MeSH terms: Drug Resistance, Bacterial/genetics*
  5. High-level aminoglycoside resistance and virulence characteristics among Enterococci isolated from recreational beaches in Malaysia
    Dada AC, Ahmad A, Usup G, Heng LY, Hamid R
    Environ Monit Assess, 2013 Sep;185(9):7427-43.
    PMID: 23417753 DOI: 10.1007/s10661-013-3110-x
    We report the first study on the occurrence of high-level aminoglycoside-resistant (HLAR) Enterococci in coastal bathing waters and beach sand in Malaysia. None of the encountered isolates were resistant to high levels of gentamicin (500 μg/mL). However, high-level resistance to kanamycin (2,000 μg/mL) was observed in 14.2 % of tested isolates, the highest proportions observed being among beach sand isolates. High-level resistance to kanamycin was higher among Enterococcus faecalis and Enterococcus faecium than Enterococcus spp. Chi-square analysis showed no significant association between responses to tested antibiotics and the species allocation or source of isolation of all tested Enterococci. The species classification of encountered Enterococci resistance to vancomycin was highest among Enterococcus spp. (5.89 %) followed by E. faecium (4.785) and least among E. faecalis. A total of 160 isolates were also tested for virulence characteristics. On the whole, caseinase production was profoundly highest (15.01 %) while the least prevalent virulence characteristic observed among tested beach Enterococci was haemolysis of rabbit blood (3.65 %). A strong association was observed between the source of isolation and responses for each of caseinase (C = 0.47, V = 0.53) and slime (C = 0.50, V = 0.58) assays. Analysis of obtained spearman's coefficient showed a strong correlation between caseinase and each of the slime production (p = 0.04), gelatinase (p = 0.0035) and haemolytic activity on horse blood (p = 0.004), respectively. Suggestively, these are the main virulent characteristics of the studied beach Enterococci. Our findings suggest that recreational beaches may contribute to the dissemination of Enterococci with HLAR and virulence characteristics.
    Matched MeSH terms: Drug Resistance, Bacterial/genetics*
  6. Antimicrobial susceptibility and pulsed-field gel electrophoresis of Shigella sonnei strains in Malaysia (1997-2000)
    Hoe CH, Yasin RM, Koh YT, Thong KL
    J Appl Microbiol, 2005;99(1):133-40.
    PMID: 15960673
    Antimicrobial resistance of Shigella sonnei from Malaysia was determined and subtyping was carried by pulsed-field gel electrophoresis (PFGE) to assess the extent of genetic diversity of these strains.
    Matched MeSH terms: Drug Resistance, Bacterial/genetics*
  7. Transcriptome analysis of Burkholderia pseudomallei SCV reveals an association with virulence, stress resistance and intracellular persistence
    Al-Maleki AR, Vellasamy KM, Mariappan V, Venkatraman G, Tay ST, Vadivelu J
    Genomics, 2020 01;112(1):501-512.
    PMID: 30980902 DOI: 10.1016/j.ygeno.2019.04.002
    Differences in expression of potential virulence and survival genes were associated with B. pseudomallei colony morphology variants. Microarray was used to investigate B. pseudomallei transcriptome alterations among the wild type and small colony variant (SCV) pre- and post-exposed to A549 cells. SCV pre- and post-exposed have lower metabolic requirements and consume lesser energy than the wild type pre- and post-exposed to A549. However, both the wild type and SCV limit their metabolic activities post- infection of A549 cells and this is indicated by the down-regulation of genes implicated in the metabolism of amino acids, carbohydrate, lipid, and other amino acids. Many well-known virulence and survival factors, including T3SS, fimbriae, capsular polysaccharides and stress response were up-regulated in both the wild type and SCV pre- and post-exposed to A549 cells. Microarray analysis demonstrated essential differences in bacterial response associated with virulence and survival pre- and post-exposed to A549 cells.
    Matched MeSH terms: Drug Resistance, Bacterial/genetics
  8. Diverse Plasmids Harboring blaCTX-M-15 in Klebsiella pneumoniae ST11 Isolates from Several Asian Countries
    Kim SY, Ko KS
    Microb Drug Resist, 2019 Mar;25(2):227-232.
    PMID: 30212274 DOI: 10.1089/mdr.2018.0020
    To reveal whether an increase of CTX-M-15-producing Klebsiella pneumoniae ST11 isolates is due to clonal dissemination across the countries, plasmids (pHK02-026, pM16-13, pIN03-01, and pTH02-34) were extracted from four K. pneumoniae isolates collected in Hong Kong, Malaysia, Thailand, and Indonesia, respectively. Complete sequencing of blaCTX-M-15-carrying plasmids was performed. In addition to the four plasmids, a previously sequenced plasmid (pKP12226) of a K. pneumoniae ST11 isolate from Korea was included in the analysis. While pIN03-01 and pTH02-34, which belonged to the incompatibility group IncX3, showed nearly the same structure, the others of IncF1A or IncFII exhibited very different structures. The number and kinds of antibiotic genes found in the plasmids were also different from each other. Cryptic prophage genes were identified in all five blaCTX-M-15-harboring plasmids from the ST11 isolates; P1-like region in pKP12226, CPZ-55 prophage region in pHK02-026, phage shock operon pspFABCD in pM16-13, and SPBc2 prophage yokD in pIN03-01 and pTH02-34. The plasmids with blaCTX-M-15 in the prevailing K. pneumoniae ST11 isolates in Asian countries might emerge from diverse origins by recombination. The prevalence of CTX-M-15-producing K. pneumoniae ST11 clone in Asian countries is not mainly due to the dissemination of a single strain.
    Matched MeSH terms: Drug Resistance, Bacterial/genetics*
  9. Fulltext Next generation sequencing reveals the antibiotic resistant variants in the genome of Pseudomonas aeruginosa
    Ramanathan B, Jindal HM, Le CF, Gudimella R, Anwar A, Razali R, et al.
    PLoS One, 2017;12(8):e0182524.
    PMID: 28797043 DOI: 10.1371/journal.pone.0182524
    Rapid progress in next generation sequencing and allied computational tools have aided in identification of single nucleotide variants in genomes of several organisms. In the present study, we have investigated single nucleotide polymorphism (SNP) in ten multi-antibiotic resistant Pseudomonas aeruginosa clinical isolates. All the draft genomes were submitted to Rapid Annotations using Subsystems Technology (RAST) web server and the predicted protein sequences were used for comparison. Non-synonymous single nucleotide polymorphism (nsSNP) found in the clinical isolates compared to the reference genome (PAO1), and the comparison of nsSNPs between antibiotic resistant and susceptible clinical isolates revealed insights into the genome variation. These nsSNPs identified in the multi-drug resistant clinical isolates were found to be altering a single amino acid in several antibiotic resistant genes. We found mutations in genes encoding efflux pump systems, cell wall, DNA replication and genes involved in repair mechanism. In addition, nucleotide deletions in the genome and mutations leading to generation of stop codons were also observed in the antibiotic resistant clinical isolates. Next generation sequencing is a powerful tool to compare the whole genomes and analyse the single base pair variations found within the antibiotic resistant genes. We identified specific mutations within antibiotic resistant genes compared to the susceptible strain of the same bacterial species and these findings may provide insights to understand the role of single nucleotide variants in antibiotic resistance.
    Matched MeSH terms: Drug Resistance, Bacterial/genetics*
  10. Detection of betalactamase producing bacterial genes and their clinical features
    Hashim RB, Husin S, Rahman MM
    Pak J Biol Sci, 2011 Jan 01;14(1):41-6.
    PMID: 21913496
    The present study was aimed to identify the gene of drug resistance betalactamase producing bacteria and clinical features of the infected patients at Hospital University Kebangsaan Malaysia. Blood samples from the patients were collected, processed and betalactamase producing drug resistance bacteria were identified by antibiotic sensitivity testing. Genes of the drug resistance bacteria were detected and characterized by polymerase chain reaction. A total of 34 isolates of drug resistance Betalactamase producing E. coli and Klebsiella spp. were isolated from 2,502 patients. Most common drug resistance gene TEM was found in 50% of the isolates. 11% was found positive for both TEM and SHV. Next 11% of the isolates expressed only SHV genes. Clinical features of the patients were recorded from where the bacteria isolated. Regarding community affiliations 70.5% of the infected patients were Malay 17.6% were Indian and 11.7% were Chinese. Majority of the patients has an underlying pre-morbid condition as reflected by their diagnosis. Better infection control and hygiene in hospitals, plus controlled and prudent use of antibiotics, is required to minimize the impact of drug resistance betalactamase producing bacteria and the spread of infections.
    Matched MeSH terms: Drug Resistance, Bacterial/genetics*
  11. Fulltext The role of interspecies recombination in the evolution of antibiotic-resistant pneumococci
    D'Aeth JC, van der Linden MP, McGee L, de Lencastre H, Turner P, Song JH, et al.
    Elife, 2021 Jul 14;10.
    PMID: 34259624 DOI: 10.7554/eLife.67113
    Multidrug-resistant Streptococcus pneumoniae emerge through the modification of core genome loci by interspecies homologous recombinations, and acquisition of gene cassettes. Both occurred in the otherwise contrasting histories of the antibiotic-resistant S. pneumoniae lineages PMEN3 and PMEN9. A single PMEN3 clade spread globally, evading vaccine-induced immunity through frequent serotype switching, whereas locally circulating PMEN9 clades independently gained resistance. Both lineages repeatedly integrated Tn916-type and Tn1207.1-type elements, conferring tetracycline and macrolide resistance, respectively, through homologous recombination importing sequences originating in other species. A species-wide dataset found over 100 instances of such interspecific acquisitions of resistance cassettes and flanking homologous arms. Phylodynamic analysis of the most commonly sampled Tn1207.1-type insertion in PMEN9, originating from a commensal and disrupting a competence gene, suggested its expansion across Germany was driven by a high ratio of macrolide-to-β-lactam consumption. Hence, selection from antibiotic consumption was sufficient for these atypically large recombinations to overcome species boundaries across the pneumococcal chromosome.
    Matched MeSH terms: Drug Resistance, Bacterial/genetics*
  12. Fulltext Stenotrophomonas maltophilia in Malaysia: molecular epidemiology and trimethoprim-sulfamethoxazole resistance
    Neela V, Rankouhi SZ, van Belkum A, Goering RV, Awang R
    Int J Infect Dis, 2012 Aug;16(8):e603-7.
    PMID: 22698885 DOI: 10.1016/j.ijid.2012.04.004
    Stenotrophomonas maltophilia is a recently identified nosocomial pathogen in Malaysia. Despite limited pathogenicity, its rate of isolation has increased in recent years. The aim of this study was to investigate the antibiotic susceptibility patterns, antibiotic resistance determinants, and the epidemiology of S. maltophilia at the largest tertiary care hospital in Malaysia.
    Matched MeSH terms: Drug Resistance, Bacterial/genetics
  13. Clarithromycin resistance and point mutations in the 23S rRNA gene in Helicobacter pylori isolates from Malaysia
    Ho SL, Tan EL, Sam CK, Goh KL
    J Dig Dis, 2010 Apr;11(2):101-5.
    PMID: 20402836 DOI: 10.1111/j.1751-2980.2010.00423.x
    To determine the prevalence of primary clarithromycin resistance amongst Helicobacter pylori (H. pylori) strains in Malaysian patients with gastroduodenal diseases, by using restriction fragment length polymorphism (RFLP) in domain V of 23S rRNA.
    Matched MeSH terms: Drug Resistance, Bacterial/genetics*
  14. Elucidating isoniazid resistance using molecular modeling
    Wahab HA, Choong YS, Ibrahim P, Sadikun A, Scior T
    J Chem Inf Model, 2009 Jan;49(1):97-107.
    PMID: 19067649 DOI: 10.1021/ci8001342
    The continuing rise in tuberculosis incidence and the problem of drug resistance strains have prompted the research on new drug candidates and the mechanism of drug resistance. Molecular docking and molecular dynamics simulation (MD) were performed to study the binding of isoniazid onto the active site of Mycobacterium tuberculosis enoyl-acyl carrier protein reductase (InhA) in an attempt to address the mycobacterial resistance against isoniazid. Results show that isonicotinic acyl-NADH (INADH) has an extremely high binding affinity toward the wild type InhA by forming stronger interactions compared to the parent drug (isoniazid) (INH). Due to the increase of hydrophobicity and reduction in the side chain's volume of A94 of mutant type InhA, both INADH and the mutated protein become more mobile. Due to this reason, the molecular interactions of INADH with mutant type are weaker than that observed with the wild type. However, the reduced interaction caused by the fluctuation of INADH and the mutant protein only inflected minor resistance in the mutant strain as inferred from free energy calculation. MD results also showed there exists a water-mediated hydrogen bond between INADH and InhA. However, the bridged water molecule is only present in the INADH-wild type complex, reflecting the putative role of the water molecule in the binding of INADH to the wild type protein. The results support the assumption that the conversion of prodrug isoniazid into its active form INADH is mediated by KatG as a necessary step prior to target binding on InhA. Our findings also contribute to a better understanding of INH resistance in mutant type.
    Matched MeSH terms: Drug Resistance, Bacterial/genetics
  15. 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: Drug Resistance, Bacterial/genetics
  16. From farm to fork: identical clones and Tn6674-like elements in linezolid-resistant Enterococcus faecalis from food-producing animals and retail meat
    Elghaieb H, Tedim AP, Abbassi MS, Novais C, Duarte B, Hassen A, et al.
    J Antimicrob Chemother, 2020 01 01;75(1):30-35.
    PMID: 31605129 DOI: 10.1093/jac/dkz419
    OBJECTIVES: Increasing numbers of linezolid-resistant Enterococcus carrying optrA are being reported across different niches worldwide. We aimed to characterize the first optrA-carrying Enterococcus faecalis obtained from food-producing animals and retail meat samples in Tunisia.

    METHODS: Seven optrA-carrying E. faecalis obtained from chicken faeces (n=3, August 2017) and retail chicken meat (n=4, August 2017) in Tunisia were analysed. Antimicrobial susceptibility was determined by disc diffusion, broth microdilution and Etest against 13 antibiotics, linezolid and tedizolid, respectively (EUCAST/CLSI). optrA stability (∼600 bacterial generations), transfer (filter mating) and location (S1-PFGE/hybridization) were characterized. WGS (Illumina-HiSeq) was done for four representatives that were analysed through in silico and genomic mapping tools.

    RESULTS: Four MDR clones carrying different virulence genes were identified in chicken faeces (ST476) and retail meat (the same ST476 clone plus ST21 and ST859) samples. MICs of linezolid and tedizolid were stably maintained at 8 and 1-2 mg/L, respectively. optrA was located in the same transferable chromosomal Tn6674-like element in ST476 and ST21 clones, similar to isolates from pigs in Malaysia and humans in China. ST859 carried a non-conjugative plasmid of ∼40 kb with an impB-fexA-optrA segment, similar to plasmids from pigs and humans in China.

    CONCLUSIONS: The same chromosomal and transferable Tn6674-like element was identified in different E. faecalis clones from humans and animals. The finding of retail meat contaminated with the same linezolid-resistant E. faecalis strain obtained from a food-producing animal highlights the potential role of the food chain in the worrisome dissemination of optrA that can be stably maintained without selective pressure over generations.

    Matched MeSH terms: Drug Resistance, Bacterial/genetics
  17. Fulltext Imipenem Treatment Induces Expression of Important Genes and Phenotypes in a Resistant Acinetobacter baumannii Isolate
    Dhabaan GN, AbuBakar S, Cerqueira GM, Al-Haroni M, Pang SP, Hassan H
    Antimicrob Agents Chemother, 2015 Dec 14;60(3):1370-6.
    PMID: 26666943 DOI: 10.1128/AAC.01696-15
    Acinetobacter baumannii has emerged as a notorious multidrug-resistant pathogen, and development of novel control measures is of the utmost importance. Understanding the factors that play a role in drug resistance may contribute to the identification of novel therapeutic targets. Pili are essential for A. baumannii adherence to and biofilm formation on abiotic surfaces as well as virulence. In the present study, we found that biofilm formation was significantly induced in an imipenem-resistant (Imp(r)) strain treated with a subinhibitory concentration of antibiotic compared to that in an untreated control and an imipenem-susceptible (Imp(s)) isolate. Using microarray and quantitative PCR analyses, we observed that several genes responsible for the synthesis of type IV pili were significantly upregulated in the Imp(r) but not in the Imp(s) isolate. Notably, this finding is corroborated by an increase in the motility of the Imp(r) strain. Our results suggest that the ability to overproduce colonization factors in response to imipenem treatment confers biological advantage to A. baumannii and may contribute to clinical success.
    Matched MeSH terms: Drug Resistance, Bacterial/genetics*
  18. Antibiotic susceptibility and molecular characterization of Salmonella enterica serovar Paratyphi B isolated from vegetables and processing environment in Malaysia
    Abatcha MG, Effarizah ME, Rusul G
    Int J Food Microbiol, 2019 Feb 02;290:180-183.
    PMID: 30342248 DOI: 10.1016/j.ijfoodmicro.2018.09.021
    Salmonella enterica serovar Paratyphi B (S. Paratyphi B) is a major foodborne pathogen distributed all over the world. However, little is known about the antibiotic resistance, genetic relatedness and virulence profile of S. Paratyphi B isolated from leafy vegetables and the processing environment in Malaysia. In this study, 6 S. Paratyphi B isolates were recovered from different vegetables and drain water of processing areas obtained from fresh food markets in Malaysia. The isolates were characterized by antibiogram, Pulsed-field gel electrophoresis (PFGE) and virulence genes. Antibiotic susceptibility test showed that 3 of the isolates were resistant to the antibiotics. These include S. Paratyphi B SP251 isolate, which was resistant to chloramphenicol, ampicillin, sulfonamides and streptomycin; Isolate SP246 which was resistant to chloramphenicol, sulfonamides and streptomycin and Isolate SP235 showing resistance to nalidixic acid only. PFGE subtyped the 6 S. Paratyphi B isolates into 6 distinct XbaI-pulsotypes, with a wide range of genetic similarity (0.55 to 0.9). The isolates from different sources and fresh food markets location were genetically diverse. Thirteen (tolC, orgA, spaN, prgH, sipB, invA, pefA, sofB, msgA, cdtB, pagC, spiA and spvB) out of the 17 virulence genes tested were found in all of the S. Paratyphi B isolates. Another gene (lpfC), was found only in one isolate (SP051). None of the isolates possessed sifA, sitC and ironN genes. In summary, this study provides unique information on antibiotic resistance, genetic relatedness, and virulotyping of S. Paratyphi B isolated from leafy vegetables and processing environment.
    Matched MeSH terms: Drug Resistance, Bacterial/genetics
  19. Fulltext Elucidating the survival and response of carbapenem resistant Klebsiella pneumoniae after exposure to imipenem at sub-lethal concentrations
    Low YM, Chong CW, Yap IKS, Chai LC, Clarke SC, Ponnampalavanar S, et al.
    Pathog Glob Health, 2018 10;112(7):378-386.
    PMID: 30380366 DOI: 10.1080/20477724.2018.1538281
    The increasing prevalence of antibiotic resistant pathogens poses a serious threat to global health. However, less emphasis has been placed to co-relate the gene expression and metabolism of antibiotic resistant pathogens. This study aims to elucidate gene expression and variations in metabolism of multidrug resistant Klebsiella pneumoniae after exposure to antibiotics. Phenotypic responses of three genotypically distinct carbapenem resistant Klebsiella pneumoniae (CRKP) strains untreated and treated with sub-lethal concentrations of imipenem were investigated via phenotype microarrays (PM). The gene expression and metabolism of the strain harboring blaNDM-1 before and after exposure to sub-lethal concentration of imipenem were further investigated by RNA-sequencing (RNA-Seq) and 1H NMR spectroscopy respectively. Most genes related to cell division, central carbon metabolism and nucleotide metabolism were downregulated after imipenem treatment. Similarly, 1H NMR spectra obtained from treated CRKP showed decrease in levels of bacterial end products (acetate, pyruvate, succinate, formate) and metabolites involved in nucleotide metabolism (uracil, xanthine, hypoxanthine) but elevated levels of glycerophosphocholine. The presence of anserine was also observed for the treated CRKP while FAPγ-adenine and methyladenine were only present in untreated bacterial cells. As a conclusion, the studied CRKP strain exhibited decrease in central carbon metabolism, cell division and nucleotide metabolism after exposure to sub-lethal concentrations of imipenem. The understanding of the complex biological system of this multidrug resistant bacterium may help in the development of novel strategies and potential targets for the management of the infections.
    Matched MeSH terms: Drug Resistance, Bacterial/genetics
  20. DNA markers for tuberculosis diagnosis
    Chin KL, Sarmiento ME, Norazmi MN, Acosta A
    Tuberculosis (Edinb), 2018 12;113:139-152.
    PMID: 30514496 DOI: 10.1016/j.tube.2018.09.008
    Tuberculosis (TB), caused by Mycobacterium tuberculosis complex (MTBC), is an infectious disease with more than 10.4 million cases and 1.7 million deaths reported worldwide in 2016. The classical methods for detection and differentiation of mycobacteria are: acid-fast microscopy (Ziehl-Neelsen staining), culture, and biochemical methods. However, the microbial phenotypic characterization is time-consuming and laborious. Thus, fast, easy, and sensitive nucleic acid amplification tests (NAATs) have been developed based on specific DNA markers, which are commercially available for TB diagnosis. Despite these developments, the disease remains uncontrollable. The identification and differentiation among MTBC members with the use of NAATs remains challenging due, among other factors, to the high degree of homology within the members and mutations, which hinders the identification of specific target sequences in the genome with potential impact in the diagnosis and treatment outcomes. In silico methods provide predictive identification of many new target genes/fragments/regions that can specifically be used to identify species/strains, which have not been fully explored. This review focused on DNA markers useful for MTBC detection, species identification and antibiotic resistance determination. The use of DNA targets with new technological approaches will help to develop NAATs applicable to all levels of the health system, mainly in low resource areas, which urgently need customized methods to their specific conditions.
    Matched MeSH terms: Drug Resistance, Bacterial/genetics
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