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  1. Fulltext A small RNA decreases the sensitivity of Shigella sonnei to norfloxacin
    Gan IN, Tan HS
    BMC Res Notes, 2019 Feb 21;12(1):97.
    PMID: 30791948 DOI: 10.1186/s13104-019-4124-4
    OBJECTIVES: Shigella is a human pathogen that causes shigellosis, an acute invasive intestinal infection. Recent studies in the model bacterium Escherichia coli (E. coli) provided evidence that small regulatory RNAs (sRNAs) can contribute to antimicrobial resistance or susceptibility. One of the sRNAs is SdsR, which increases sensitivity of E. coli against fluoroquinolone by repressing the drug efflux pump, TolC. However, no reports exist about the effect of SdsR on fluoroquinolone resistance in Shigella sonnei (S. sonnei). In this study, we established the effect of SdsR on the sensitivity of S. sonnei to norfloxacin.

    DATA DESCRIPTION: We tested the effects of SdsR and SdsRv2 on fluoroquinolone resistance in S. sonnei in vivo. SdsRv2 is a synthetic version which promotes higher binding stability to tolC mRNA. Overexpression of either SdsR or SdsRv2 lowers the expression of tolC mRNA. Interestingly, SdsR and SdsRv2 promote the growth of S. sonnei in the presence of a sub-inhibitory concentration of norfloxacin. Mutant carrying SdsRv2 showed the highest growth advantage. This phenotype is opposite to the effect of SdsR reported in E. coli. This study is an example that demonstrates the difference in the phenotypic effect of a highly conserved sRNA in two closely related bacteria.

    Matched MeSH terms: Gene Expression Regulation, Bacterial/drug effects*
  2. Fulltext Reversal of ampicillin resistance in MRSA via inhibition of penicillin-binding protein 2a by Acalypha wilkesiana
    Santiago C, Pang EL, Lim KH, Loh HS, Ting KN
    Biomed Res Int, 2014;2014:965348.
    PMID: 25101303 DOI: 10.1155/2014/965348
    The inhibitory activity of a semipure fraction from the plant, Acalypha wilkesiana assigned as 9EA-FC-B, alone and in combination with ampicillin, was studied against methicillin-resistant Staphylococcus aureus (MRSA). In addition, effects of the combination treatment on PBP2a expression were investigated. Microdilution assay was used to determine the minimal inhibitory concentrations (MIC). Synergistic effects of 9EA-FC-B with ampicillin were determined using the fractional inhibitory concentration (FIC) index and kinetic growth curve assay. Western blot experiments were carried out to study the PBP2a expression in treated MRSA cultures. The results showed a synergistic effect between ampicillin and 9EA-FC-B treatment with the lowest FIC index of 0.19 (synergism ≤ 0.5). The presence of 9EA-FC-B reduced the MIC of ampicillin from 50 to 1.56 μg mL(-1). When ampicillin and 9EA-FC-B were combined at subinhibitory level, the kinetic growth curves were suppressed. The antibacterial effect of 9EA-FC-B and ampicillin was shown to be synergistic. The synergism is due the ability of 9EA-FC-B to suppress the activity of PBP2a, thus restoring the susceptibility of MRSA to ampicillin. Corilagin was postulated to be the constituent responsible for the synergistic activity showed by 9EA-FC-B.
    Matched MeSH terms: Gene Expression Regulation, Bacterial/drug effects
  3. Fulltext Lovastatin in Aspergillus terreus: fermented rice straw extracts interferes with methane production and gene expression in Methanobrevibacter smithii
    Faseleh Jahromi M, Liang JB, Ho YW, Mohamad R, Goh YM, Shokryazdan P, et al.
    Biomed Res Int, 2013;2013:604721.
    PMID: 23710454 DOI: 10.1155/2013/604721
    Lovastatin, a natural byproduct of some fungi, is able to inhibit HMG-CoA (3-hydroxy-3 methyl glutaryl CoA) reductase. This is a key enzyme involved in isoprenoid synthesis and essential for cell membrane formation in methanogenic Archaea. In this paper, experiments were designed to test the hypothesis that lovastatin secreted by Aspergillus terreus in fermented rice straw extracts (FRSE) can inhibit growth and CH4 production in Methanobrevibacter smithii (a test methanogen). By HPLC analysis, 75% of the total lovastatin in FRSE was in the active hydroxyacid form, and in vitro studies confirmed that this had a stronger effect in reducing both growth and CH4 production in M. smithii compared to commercial lovastatin. Transmission electron micrographs revealed distorted morphological divisions of lovastatin- and FRSE-treated M. smithii cells, supporting its role in blocking normal cell membrane synthesis. Real-time PCR confirmed that both commercial lovastatin and FRSE increased (P < 0.01) the expression of HMG-CoA reductase gene (hmg). In addition, expressions of other gene transcripts in M. smithii. with a key involvement in methanogenesis were also affected. Experimental confirmation that CH4 production is inhibited by lovastatin in A. terreus-fermented rice straw paves the way for its evaluation as a feed additive for mitigating CH4 production in ruminants.
    Matched MeSH terms: Gene Expression Regulation, Bacterial/drug effects
  4. Fulltext Transcriptional profiles of the response of methicillin-resistant Staphylococcus aureus to pentacyclic triterpenoids
    Chung PY, Chung LY, Navaratnam P
    PLoS One, 2013;8(2):e56687.
    PMID: 23437212 DOI: 10.1371/journal.pone.0056687
    Staphylococcus aureus is an important human pathogen in both hospital and the community that has demonstrated resistance to all currently available antibiotics over the last two decades. Multidrug-resistant isolates of methicillin-resistant S. aureus (MRSA) exhibiting decreased susceptibilities to glycopeptides has also emerged, representing a crucial challenge for antimicrobial therapy and infection control. The availability of complete whole-genome nucleotide sequence data of various strains of S. aureus presents an opportunity to explore novel compounds and their targets to address the challenges presented by antimicrobial drug resistance in this organism. Study compounds α-amyrin [3β-hydroxy-urs-12-en-3-ol (AM)], betulinic acid [3β-hydroxy-20(29)-lupaene-28-oic acid (BA)] and betulinaldehyde [3β-hydroxy-20(29)-lupen-28-al (BE)] belong to pentacyclic triterpenoids and were reported to exhibit antimicrobial activities against bacteria and fungi, including S. aureus. The MIC values of these compounds against a reference strain of methicillin-resistant S. aureus (MRSA) (ATCC 43300) ranged from 64 µg/ml to 512 µg/ml. However, the response mechanisms of S. aureus to these compounds are still poorly understood. The transcription profile of reference strain of MRSA treated with sub-inhibitory concentrations of the three compounds was determined using Affymetrix GeneChips. The findings showed that these compounds regulate multiple desirable targets in cell division, two-component system, ABC transporters, fatty acid biosynthesis, peptidoglycan biosynthesis, aminoacyl-tRNA synthetase, ribosome and β-lactam resistance pathways which could be further explored in the development of therapeutic agents for the treatment of S. aureus infections.
    Matched MeSH terms: Gene Expression Regulation, Bacterial/drug effects
  5. 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: Gene Expression Regulation, Bacterial/drug effects
  6. Potential targets by pentacyclic triterpenoids from Callicarpa farinosa against methicillin-resistant and sensitive Staphylococcus aureus
    Chung PY, Chung LY, Navaratnam P
    Fitoterapia, 2014 Apr;94:48-54.
    PMID: 24508863 DOI: 10.1016/j.fitote.2014.01.026
    The evolution of antibiotic resistance in Staphylococcus aureus showed that there is no long-lasting remedy against this pathogen. The limited number of antibacterial classes and the common occurrence of cross-resistance within and between classes reinforce the urgent need to discover new compounds targeting novel cellular functions not yet targeted by currently used drugs. One of the experimental approaches used to discover novel antibacterials and their in vitro targets is natural product screening. Three known pentacyclic triterpenoids were isolated for the first time from the bark of Callicarpa farinosa Roxb. (Verbenaceae) and identified as α-amyrin [3β-hydroxy-urs-12-en-3-ol], betulinic acid [3β-hydroxy-20(29)-lupaene-28-oic acid], and betulinaldehyde [3β-hydroxy-20(29)-lupen-28-al]. These compounds exhibited antimicrobial activities against reference and clinical strains of methicillin-resistant (MRSA) and methicillin-sensitive S. aureus (MSSA), with minimum inhibitory concentration (MIC) ranging from 2 to 512 μg/mL. From the genome-wide transcriptomic analysis to elucidate the antimicrobial effects of these compounds, multiple novel cellular targets in cell division, two-component system, ABC transporters, fatty acid biosynthesis, peptidoglycan biosynthesis, aminoacyl-tRNA synthetases, ribosomes and β-lactam resistance pathways are affected, resulting in destabilization of the bacterial cell membrane, halt in protein synthesis, and inhibition of cell growth that eventually lead to cell death. The novel targets in these essential pathways could be further explored in the development of therapeutic compounds for the treatment of S. aureus infections and help mitigate resistance development due to target alterations.
    Matched MeSH terms: Gene Expression Regulation, Bacterial/drug effects
  7. Swietenia macrophylla extract promotes the ability of Caenorhabditis elegans to survive Pseudomonas aeruginosa infection
    Dharmalingam K, Tan BK, Mahmud MZ, Sedek SA, Majid MI, Kuah MK, et al.
    J Ethnopharmacol, 2012 Jan 31;139(2):657-63.
    PMID: 22193176 DOI: 10.1016/j.jep.2011.12.016
    Swietenia macrophylla or commonly known as big leaf mahogany, has been traditionally used as an antibacterial and antifungal agent.
    Matched MeSH terms: Gene Expression Regulation, Bacterial/drug effects
  8. High level expression and characterization of a novel thermostable, organic solvent tolerant, 1,3-regioselective lipase from Geobacillus sp. strain ARM
    Ebrahimpour A, Rahman RN, Basri M, Salleh AB
    Bioresour Technol, 2011 Jul;102(13):6972-81.
    PMID: 21531550 DOI: 10.1016/j.biortech.2011.03.083
    The mature ARM lipase gene was cloned into the pTrcHis expression vector and over-expressed in Escherichia coli TOP10 host. The optimum lipase expression was obtained after 18 h post induction incubation with 1.0mM IPTG, where the lipase activity was approximately 1623-fold higher than wild type. A rapid, high efficient, one-step purification of the His-tagged recombinant lipase was achieved using immobilized metal affinity chromatography with 63.2% recovery and purification factor of 14.6. The purified lipase was characterized as a high active (7092 U mg(-1)), serine-hydrolase, thermostable, organic solvent tolerant, 1,3-specific lipase with a molecular weight of about 44 kDa. The enzyme was a monomer with disulfide bond(s) in its structure, but was not a metalloenzyme. ARM lipase was active in a broad range of temperature and pH with optimum lipolytic activity at pH 8.0 and 65°C. The enzyme retained 50% residual activity at pH 6.0-7.0, 50°C for more than 150 min.
    Matched MeSH terms: Gene Expression Regulation, Bacterial/drug effects
  9. Subtractive Protein Profiling of Salmonella typhimurium Biofilm Treated with DMSO
    Yahya MFZR, Alias Z, Karsani SA
    Protein J, 2017 08;36(4):286-298.
    PMID: 28470375 DOI: 10.1007/s10930-017-9719-9
    Salmonella typhimurium is an important biofilm-forming bacteria. It is known to be resistant to a wide range of antimicrobials. The present study was carried out to evaluate the effects of dimethyl sulfoxide (DMSO) against S. typhimurium biofilm and investigate whole-cell protein expression by biofilm cells following treatment with DMSO. Antibiofilm activities were assessed using pellicle assay, crystal violet assay, colony-forming unit counting and extracellular polymeric substance (EPS) matrix assay whilst differential protein expression was investigated using a combination of one dimensional sodium dodecyl sulfate polyacrylamide gel electrophoresis, tandem mass spectrometry and bioinformatics. Treatment with 32% DMSO inhibited pellicle formation, biofilm viability, biofilm biomass and several important components of EPS matrix. Subtractive protein profiling identified two unique protein bands (25.4 and 51.2 kDa) which were present only in control biofilm and not in 32% DMSO-treated biofilm. In turn, 29 and 46 proteins were successfully identified from the protein bands of 25.4 and 51.2 kDa respectively. Protein interaction network analysis identified several biological pathways to be affected, including glycolysis, PhoP-PhoQ phosphorelay signalling and flagellar biosynthesis. The present study suggests that DMSO may inhibit multiple biological pathways to control biofilm formation.
    Matched MeSH terms: Gene Expression Regulation, Bacterial/drug effects*
  10. Black sea cucumber (Holothuria atra Jaeger, 1833) rescues Pseudomonas aeruginosa-infected Caenorhabditis elegans via reduction of pathogen virulence factors and enhancement of host immunity
    Lee WT, Tan BK, Eng SA, Yuen GC, Chan KL, Sim YK, et al.
    Food Funct, 2019 Sep 01;10(9):5759-5767.
    PMID: 31453615 DOI: 10.1039/c9fo01357a
    A strategy to circumvent the problem of multidrug resistant pathogens is the discovery of anti-infectives targeting bacterial virulence or host immunity. Black sea cucumber (Holothuria atra) is a tropical sea cucumber species traditionally consumed as a remedy for many ailments. There is a paucity of knowledge on the anti-infective capacity of H. atra and the underlying mechanisms involved. The objective of this study is to utilize the Caenorhabditis elegans-P. aeruginosa infection model to elucidate the anti-infective properties of H. atra. A bioactive H. atra extract and subsequently its fraction were shown to have the capability of promoting the survival of C. elegans during a customarily lethal P. aeruginosa infection. The same entities also attenuate the production of elastase, protease, pyocyanin and biofilm in P. aeruginosa. The treatment of infected transgenic lys-7::GFP worms with this H. atra fraction restores the repressed expression of the defense enzyme lys-7, indicating an improved host immunity. QTOF-LCMS analysis revealed the presence of aspidospermatidine, an indole alkaloid, and inosine in this fraction. Collectively, our findings show that H. atra possesses anti-infective properties against P. aeruginosa infection, by inhibiting pathogen virulence and, eventually, reinstating host lys-7 expression.
    Matched MeSH terms: Gene Expression Regulation, Bacterial/drug effects
  11. Transcriptome analysis of methicillin-resistant Staphylococcus aureus in response to stigmasterol and lupeol
    Adnan SN, Ibrahim N, Yaacob WA
    J Glob Antimicrob Resist, 2017 03;8:48-54.
    PMID: 27992774 DOI: 10.1016/j.jgar.2016.10.006
    OBJECTIVES: Methicillin-resistant Staphylococcus aureus (MRSA) is an important pathogen with multiple antibiotic resistance that causes morbidity and mortality worldwide. Multidrug-resistant (MDR) MRSA with increased resistance to currently available antibiotics has challenged the world to develop new therapeutic agents. Stigmasterol and lupeol, from the plant Phyllanthus columnaris, exhibit antibacterial activities against MRSA. The aim of this study was to utilise next-generation sequencing (NGS) to provide further insight into the novel transcriptional response of MRSA exposed to stigmasterol and lupeol.

    METHODS: Time-kill analysis of one MRSA reference strain (ATCC 43300) and three clinical isolates (WM3, BM1 and KJ7) for both compounds was first performed to provide the bacteriostatic/bactericidal profile. Then, MRSA ATCC 43300 strain treated with both compounds was interrogated by NGS.

    RESULTS: Both stigmasterol and lupeol possessed bacteriostatic properties against all MRSA tested; however, lupeol exhibited both bacteriostatic and bactericidal properties within the same minimum inhibitory concentration and minimum bactericidal concentration values against BM1 (12.5mg/mL). Transcriptome profiling of MRSA ATCC 43300 revealed significant modulation of gene expression with multiple desirable targets by both compounds, which caused a reduction in the translation processes leading to inhibition of protein synthesis and prevention of bacterial growth.

    CONCLUSIONS: This study highlights the potential of both stigmasterol and lupeol as new promising anti-MRSA agents.

    Matched MeSH terms: Gene Expression Regulation, Bacterial/drug effects
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