Displaying publications 1 - 20 of 56 in total

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  1. Ahmad N, Zakaria WR, Mohamed R
    Helicobacter, 2011 Feb;16(1):47-51.
    PMID: 21241412 DOI: 10.1111/j.1523-5378.2010.00816.x
    The prevalence of antibiotic resistance varies in geographic areas. The information on the antibiotic susceptibility patterns of Helicobacter pylori (H. pylori) in our local setting is therefore relevant as a guide for the treatment options.
    Matched MeSH terms: Helicobacter Infections/microbiology*
  2. Ahmed N, Loke MF, Kumar N, Vadivelu J
    Helicobacter, 2013 Sep;18 Suppl 1:1-4.
    PMID: 24011237 DOI: 10.1111/hel.12069
    We describe features of key additions to the existing pool of publicly accessible Helicobacter pylori genome sequences and sequences of Helicobacter pylori phages from April 2012 to March 2013. In addition, important studies involving H. pylori genomes, especially those pertaining to genomic diversity, disease outcome, H. pylori population structure and evolution are reviewed. High degree of homologous recombination contributes to increased diversity of H. pylori genomes. New methods of resolving H. pylori population structure to an ultrafine level led to the proposal of new subpopulations. As the magnitude of diversity in the H. pylori gene pool becomes more and more clear, geographic and demographic factors should be brought to analysis while identifying disease-specific biomarkers and defining new virulence mechanisms.
    Matched MeSH terms: Helicobacter Infections/microbiology*
  3. Alfizah H, Ramelah M
    Malays J Pathol, 2012 Jun;34(1):29-34.
    PMID: 22870595 MyJurnal
    Infection with Helicobacter pylori cagA-positive strains is associated with gastroduodenal diseases. The CagA protein is injected into gastric epithelial cells and supposedly induces morphological changes termed the 'hummingbird phenotype', which is associated with scattering and increased cell motility. The molecular mechanisms leading to the CagA-dependent morphological changes are only partially known. The present study was carried out to investigate the effect of CagA variants on the magnitude of gastric epithelial cell morphological changes. Recombinant 3' terminal domains of cagA were cloned and expressed in a gastric epithelial cell line and the hummingbird phenotype was quantified by microscopy. The 3' region of the cagA gene of Malaysian H. pylori isolates showed six sub-genotypes that differed in the structural organization of the EPIYA repeat sequences. The percentage of hummingbird cells induced by CagA increased with duration of transfection. The hummingbird phenotype was observed to be more pronounced when CagA with 4 EPIYA motifs rather than 3 or 2 EPIYA motifs was produced. The activity of different CagA variants in the induction of the hummingbird phenotype in gastric epithelial cells depends at least in part on EPIYA motif variability. The difference in CagA genotypes might influence the potential of individual CagAs to cause morphological changes in host cells. Depending on the relative exposure of cells to CagA genotypes, this may contribute to the various disease outcomes caused by H. pylori infection in different individuals.
    Matched MeSH terms: Helicobacter Infections/microbiology
  4. Alfizah H, Ramelah M, Rizal AM, Anwar AS, Isa MR
    Helicobacter, 2012 Oct;17(5):340-9.
    PMID: 22967117 DOI: 10.1111/j.1523-5378.2012.00956.x
    Polymorphisms of Helicobacter pylori cagA and vacA genes do exist and may contribute to differences in H. pylori infection and gastroduodenal diseases among races in the Malaysian population. This study was conducted to characterize the polymorphisms in H. pylori cagA and vacA in Malaysian population.
    Matched MeSH terms: Helicobacter Infections/microbiology*
  5. Alfizah H, Norazah A, Hamizah R, Ramelah M
    J Med Microbiol, 2014 May;63(Pt 5):703-709.
    PMID: 24757218 DOI: 10.1099/jmm.0.069781-0
    Antibiotic resistance is increasing worldwide, and it has been regarded as the main factor reducing the efficacy of Helicobacter pylori therapy. The aim of this study was to determine the phenotype and genotype of antibiotic-resistant strains of H. pylori in the Malaysian population and to evaluate the impact of antibiotic resistance to eradication outcome. One hundred and sixty-one H. pylori isolates were analysed in this study. Metronidazole, clarithromycin, fluoroquinolone, amoxicillin and tetracycline susceptibilities were determined by Etest. PCR followed by DNA sequencing was carried out to determine mutations. The medical records of the patients infected with resistant strains were reviewed to determine the eradication outcome. Metronidazole resistance was encountered in 36.6 % of H. pylori isolates, whereas clarithromycin and fluoroquinolone resistance was observed in 1.2  and 1.9 % of isolates, respectively. All strains tested were susceptible to amoxicillin and tetracycline. Frameshift and nonsense mutations in rdxA and frxA genes resulting in stop codons contributed to metronidazole resistance, which leads to reduced eradication efficacy. A2142G and A2143G mutations of 23S rRNA were identified as causing failure of the eradication therapy. Mutation at either codon 87 or 91 of the gyrA gene was identified in fluoroquinolone-resistant strains. However, the effect of resistance could not be assessed. This study showed that frameshift and nonsense mutations in rdxA or frxA genes and point mutations in the 23S rRNA affected the efficacy of H. pylori eradication therapy.
    Matched MeSH terms: Helicobacter Infections/microbiology*
  6. Amin M, Anwar F, Janjua MRSA, Iqbal MA, Rashid U
    Int J Mol Sci, 2012;13(8):9923-9941.
    PMID: 22949839 DOI: 10.3390/ijms13089923
    A green synthesis route for the production of silver nanoparticles using methanol extract from Solanum xanthocarpum berry (SXE) is reported in the present investigation. Silver nanoparticles (AgNps), having a surface plasmon resonance (SPR) band centered at 406 nm, were synthesized by reacting SXE (as capping as well as reducing agent) with AgNO(3) during a 25 min process at 45 °C. The synthesized AgNps were characterized using UV-Visible spectrophotometry, powdered X-ray diffraction, and transmission electron microscopy (TEM). The results showed that the time of reaction, temperature and volume ratio of SXE to AgNO(3) could accelerate the reduction rate of Ag(+) and affect the AgNps size and shape. The nanoparticles were found to be about 10 nm in size, mono-dispersed in nature, and spherical in shape. In vitro anti-Helicobacter pylori activity of synthesized AgNps was tested against 34 clinical isolates and two reference strains of Helicobacter pylori by the agar dilution method and compared with AgNO(3) and four standard drugs, namely amoxicillin (AMX), clarithromycin (CLA), metronidazole (MNZ) and tetracycline (TET), being used in anti-H. pylori therapy. Typical AgNps sample (S1) effectively inhibited the growth of H. pylori, indicating a stronger anti-H. pylori activity than that of AgNO(3) or MNZ, being almost equally potent to TET and less potent than AMX and CLA. AgNps under study were found to be equally efficient against the antibiotic-resistant and antibiotic-susceptible strains of H. pylori. Besides, in the H. pylori urease inhibitory assay, S1 also exhibited a significant inhibition. Lineweaver-Burk plots revealed that the mechanism of inhibition was noncompetitive.
    Matched MeSH terms: Helicobacter Infections/microbiology
  7. Ansari S, Yamaoka Y
    Int J Mol Sci, 2020 Oct 08;21(19).
    PMID: 33050101 DOI: 10.3390/ijms21197430
    Helicobacter pylori causes persistent infection in the gastric epithelium of more than half of the world's population, leading to the development of severe complications such as peptic ulcer diseases, gastric cancer, and gastric mucosa-associated lymphoid tissue (MALT) lymphoma. Several virulence factors, including cytotoxin-associated gene A (CagA), which is translocated into the gastric epithelium via the type 4 secretory system (T4SS), have been indicated to play a vital role in disease development. Although infection with strains harboring the East Asian type of CagA possessing the EPIYA-A, -B, and -D sequences has been found to potentiate cell proliferation and disease pathogenicity, the exact mechanism of CagA involvement in disease severity still remains to be elucidated. Therefore, we discuss the possible role of CagA in gastric pathogenicity.
    Matched MeSH terms: Helicobacter Infections/microbiology
  8. Ansari S, Yamaoka Y
    Expert Rev Anti Infect Ther, 2020 10;18(10):987-996.
    PMID: 32536287 DOI: 10.1080/14787210.2020.1782739
    Introduction Helicobacter pylori causes, via the influence of several virulence factors, persistent infection of the stomach, which leads to severe complications. Vacuolating cytotoxin A (VacA) is observed in almost all clinical strains of H. pylori; however, only some strains produce the toxigenic and pathogenic VacA, which is influenced by the gene sequence variations. VacA exerts its action by causing cell vacuolation and apoptosis. We performed a PubMed search to review the latest literatures published in English language. Areas covered Articles regarding H. pylori VacA and its genotypes, architecture, internalization, and role in gastric infection and pathogenicity are reviewed. We included the search for recently published literature until January 2020. Expert opinion H. pylori VacA plays a crucial role in severe gastric pathogenicity. In addition, VacA mediated in vivo bacterial survival leads to persistent infection and an enhanced bacterial evasion from the action of antibiotics and the innate host defense system, which leads to drug evasion. VacA as a co-stimulator for the CagA phosphorylation may exert a synergistic effect playing an important role in the CagA-mediated pathogenicity.
    Matched MeSH terms: Helicobacter Infections/microbiology
  9. Boey CC, Goh KL, Lee WS, Parasakthi N
    J Paediatr Child Health, 1999 Apr;35(2):151-2.
    PMID: 10365351
    OBJECTIVES: To determine the prevalence of Helicobacter pylori (H. pylori) in healthy Malaysian children and to discover whether differences exist among children of different races.

    METHODS: Serum samples from asymptomatic children tested for H. pylori seropositivity using an ELISA test.

    RESULTS: Five hundred and fourteen healthy urban Malaysian children aged 0.5 to 17 (mean 5.9) years from three different racial groups had their blood tested for H. pylori antibodies. The overall prevalence was 10.3%. There was no significant difference in the prevalence of infection between boys and girls, but a significant rise was noted with increasing age (P = 0.009). Seropositivity was most common in the Indians and lowest in the Malays (P = 0.001). Father's level of education did not affect the child's rate of H. pylori seropositivity.

    CONCLUSION: The prevalence of H. pylori seropositivity among asymptomatic urban Malaysian children is lowest in Malays. Intermediate in Chinese and highest in Indians. The racial differences found in children are consistent with those found in Malaysian adults.

    Matched MeSH terms: Helicobacter Infections/microbiology*
  10. Castaño-Rodríguez N, Kaakoush NO, Pardo AL, Goh KL, Fock KM, Mitchell HM
    Hum Immunol, 2014 Aug;75(8):808-15.
    PMID: 24929142 DOI: 10.1016/j.humimm.2014.06.001
    Gastric cancer (GC) is a progressive process initiated by Helicobacter pylori-induced inflammation. Initial recognition of H. pylori involves Toll-like receptors (TLRs), central molecules in the host inflammatory response. Here, we investigated the association between novel polymorphisms in genes involved in the TLR signalling pathway, including TLR2, TLR4, LBP, MD-2, CD14 and TIRAP, and risk of H. pylori infection and related GC.
    Matched MeSH terms: Helicobacter Infections/microbiology
  11. Castaño-Rodríguez N, Goh KL, Fock KM, Mitchell HM, Kaakoush NO
    Sci Rep, 2017 11 21;7(1):15957.
    PMID: 29162924 DOI: 10.1038/s41598-017-16289-2
    The gastric microbiome has been proposed as an etiological factor in gastric carcinogenesis. We compared the gastric microbiota in subjects presenting with gastric cancer (GC, n = 12) and controls (functional dyspepsia (FD), n = 20) from a high GC risk population in Singapore and Malaysia. cDNA from 16S rRNA transcripts were amplified (515F-806R) and sequenced using Illumina MiSeq 2 × 250 bp chemistry. Increased richness and phylogenetic diversity but not Shannon's diversity was found in GC as compared to controls. nMDS clustered GC and FD subjects separately, with PERMANOVA confirming a significant difference between the groups. H. pylori serological status had a significant impact on gastric microbiome α-diversity and composition. Several bacterial taxa were enriched in GC, including Lactococcus, Veilonella, and Fusobacteriaceae (Fusobacterium and Leptotrichia). Prediction of bacterial metabolic contribution indicated that serological status had a significant impact on metabolic function, while carbohydrate digestion and pathways were enriched in GC. Our findings highlight three mechanisms of interest in GC, including enrichment of pro-inflammatory oral bacterial species, increased abundance of lactic acid producing bacteria, and enrichment of short chain fatty acid production pathways.
    Matched MeSH terms: Helicobacter Infections/microbiology
  12. Fadilah N, Hanafiah A, Razlan H, Wong ZQ, Mohamed Rose I, Rahman MM
    Br J Biomed Sci, 2016 Oct;73(4):180-187.
    PMID: 27922429
    BACKGROUND: No gold standard has yet been established for the diagnosis of H. pylori infection. A multiplex polymerase chain reaction (mPCR) was developed in this study for rapid, sensitive and specific detection of H. pylori from gastric biopsies.

    METHODS: H. pylori infections were determined by in-house rapid urease test (iRUT), culture, histology and multiplex PCR.

    RESULTS: A total of 140 (60.9%) from 230 patients were positive for H. pylori infection. H. pylori were detected in 9.6% (22/230), 17% (39/230), 12.6% (29/230) and 60% (138/230) of biopsy specimens by culture, iRUT, histology and mPCR, respectively. mPCR identified H. pylori infection in 100% of biopsies with positive histology and culture. All biopsies with positive iRUT yielded positive PCR except two cases. mPCR also detected H. pylori in additional 116, 101 and 109 biopsies that were negative by culture, iRUT and histology, respectively. Positive samples by mPCR showed lower average in H. pylori density, activity and inflammation scores. The Indians showed the highest prevalence of H. pylori infection compared to the Chinese and the Malays. In addition, Chinese patients with older age were significantly infected compared to other ethnicities.

    CONCLUSION: PCR was able to detect the highest numbers of positive cases although the lowest average scores were recorded in the activity, inflammatory and H. pylori density.

    Matched MeSH terms: Helicobacter Infections/microbiology
  13. Fauzia KA, Miftahussurur M, Syam AF, Waskito LA, Doohan D, Rezkitha YAA, et al.
    Toxins (Basel), 2020 07 24;12(8).
    PMID: 32722296 DOI: 10.3390/toxins12080473
    We evaluated biofilm formation of clinical Helicobacter pylori isolates from Indonesia and its relation to antibiotic resistance. We determined the minimum inhibition concentration (MIC) of amoxicillin, clarithromycin, levofloxacin, metronidazole and tetracycline by the Etest to measure the planktonic susceptibility of 101 H. pylori strains. Biofilms were quantified by the crystal violet method. The minimum biofilm eradication concentration (MBEC) was obtained by measuring the survival of bacteria in a biofilm after exposure to antibiotics. The majority of the strains formed a biofilm (93.1% (94/101)), including weak (75.5%) and strong (24.5%) biofilm-formers. Planktonic resistant and sensitive strains produced relatively equal amounts of biofilms. The resistance proportion, shown by the MBEC measurement, was higher in the strong biofilm group for all antibiotics compared to the weak biofilm group, especially for clarithromycin (p = 0.002). Several cases showed sensitivity by the MIC measurement, but resistance according to the MBEC measurements (amoxicillin, 47.6%; tetracycline, 57.1%; clarithromycin, 19.0%; levofloxacin, 38.1%; and metronidazole 38.1%). Thus, biofilm formation may increase the survival of H. pylori and its resistance to antibiotics. Biofilm-related antibiotic resistance should be evaluated with antibiotic susceptibility.
    Matched MeSH terms: Helicobacter Infections/microbiology
  14. Goh KL, Manikam J, Qua CS
    Aliment Pharmacol Ther, 2012 May;35(9):1097-102.
    PMID: 22404486 DOI: 10.1111/j.1365-2036.2012.05054.x
    BACKGROUND:
    H. pylori eradication failures are difficult to treat and rescue therapies often consist of complex treatment regimens.

    AIM:
    To determine an effective and practical rescue therapeutic strategy for H. pylori treatment failures using two consecutive regimens: first rescue therapy - rabeprazole 20 mg t.d.s. and amoxicillin 1 g t.d.s. for 2 weeks and for failures a further second rescue therapy - rabeprazole 20 mg b.d., levofloxacin 500 mg b.d., amoxicillin 1 g b.d. for a further 2 weeks.

    METHODS:
    Consecutive patients who failed the proton pump inhibitor (PPI) 1-week triple therapy were recruited for the study. H. pylori status was determined by a C(13) urea breath test.

    RESULTS:
    One hundred and forty-nine patients received the first rescue therapy. Seven were not compliant to medication/defaulted follow-up. Eradication success- first rescue therapy: per protocol (PP) analysis-107/142 (75.4%) (95% CI (68.3-82.4%) and intention to treat (ITT) analysis-107/149 (71.8%) 95% CI (64.6-79.0%). Thirty-one of 35 patients who failed the first rescue therapy received the second rescue therapy. All were compliant with medications. Eradication success- PP and ITT was 28/31 (90.3%) 95% CI (74.2-98.0%). The cumulative eradication rate using both rescue therapies: PP analysis- 135/138 (97.8%) 95% CI: (93.8-99.6%), ITT analysis- 135/149 (90.6%) 95% CI: (84.7-94.8%).

    CONCLUSIONS:
    A 2-week high dose PPI-amoxicillin dual therapy followed by a PPI-amoxicillin-levofloxacin triple therapy were highly successful in achieving eradication in H. pylori treatment failures.
    Matched MeSH terms: Helicobacter Infections/microbiology
  15. Goh KL, Chan WK, Shiota S, Yamaoka Y
    Helicobacter, 2011 Sep;16 Suppl 1:1-9.
    PMID: 21896079 DOI: 10.1111/j.1523-5378.2011.00874.x
    This review summarizes studies on the epidemiology and public health implications of Helicobacter pylori published in peer-reviewed journals from April 2010 through March 2011. Prevalence rates vary widely between different geographical regions and ethnic groups. An interesting study from the USA identified the degree of African ancestry as an independent predictor of H. pylori infection. Two studies have demonstrated early childhood as the period of transmission of infection and identified an infected sibling as an important risk factor. An oral-oral route of spread has been substantiated with several studies showing the presence of H. pylori in the oral cavity. Studies have shown the presence of H. pylori in drinking water and the role of poor living conditions and sanitation in H. pylori infection, supporting an oral-fecal route of spread. Screening for H. pylori as a gastric cancer pre-screening strategy has been described in Japan, and the importance of H. pylori eradication as a gastric cancer-prevention strategy has now been further emphasized in Japanese guidelines. Two studies have shown a decrease in the burden of dyspepsia and peptic ulcer disease with H. pylori eradication.
    Matched MeSH terms: Helicobacter Infections/microbiology
  16. Goh KL, Navaratnam P
    Helicobacter, 2011 Jun;16(3):241-5.
    PMID: 21585611 DOI: 10.1111/j.1523-5378.2011.00841.x
    OBJECTIVE: Bacterial resistance to antibiotics is the single most important determinant of treatment success. The objective of this study was to determine the prevalence of Helicobacter pylori resistance to clarithromycin, amoxicillin, metronidazole, tetracycline, levofloxacin, rifabutin, and furazolidone in our local bacterial strains.
    METHODS: Samples from consecutive ninety patients were obtained for culture and sensitivity testing. Resistance to individual antibiotics were tested using the E-test and MIC(90) read from the strips. Resistance to rifampicin and nitrofurantoin were used as a surrogate for rifabutin and furazolidine.
    RESULTS: There was a high prevalence of resistance to metronidazole 68/90 (75.5%). No male (34/45 (75.5%) versus female (35/45 (77.7%) difference in frequency of metronidazole resistance was noted (p = 1.000). There was zero resistance (0) to clarithromycin, levofloxacin, amoxicillin, and nitrofurantoin/furazolidone. Resistance to rifampicin/rifabutin was for breakpoints of 1 and 4 μg/mL of 14.4 and 2.2% respectively.
    CONCLUSIONS: Although there was high bacterial resistance to metronidazole, the absence of resistance particularly to the key antibiotics used in H. pylori eradication therapy: clarithromycin and levofloxacin is reassuring to note. Continued monitoring of antibiotic resistance should be carried out.
    Matched MeSH terms: Helicobacter Infections/microbiology*
  17. Goh KL, Parasakthi N, Peh SC, Anderson PE, Tan KK
    Singapore Med J, 1995 Dec;36(6):619-20.
    PMID: 8781634
    Omeprazole has been shown to have a suppressive effect on Helicobacter pylori. The aim of this study was to determine if prolonged treatment with omeprazole would result in a higher eradication rate than short course treatment. Twenty patients with endoscopy proven duodenal ulcers and unequivocal evidence of Helicobacter pylori (HP) infection based on culture, histology, urease test and Gram's stain of a fresh tissue smear were treated with omeprazole 40 mg om for 2-4 weeks. Following ulcer healing, patients received either maintenance omeprazole 20 mg om or placebo for up to one year. All 20 patients had healed ulcers following a 2-4 week course of omeprazole 40 mg om.. All were negative for HP at the end of treatment. Thirteen patients received short course therapy with omeprazole only, followed by placebo. On follow-up endoscopy at 3 months, only one of 13 (7.7%) had eradicated the bacteria. Seven patients received maintenance treatment with omeprazole 20mg om for one year. Following completion of treatment, patients were followed up at 1, 3 and 6 months. Only one of 7 (14.3%) patients had eradicated the infection on long term follow-up. The eradication rates of HP with both short and long course omeprazole monotherapy were low.
    Matched MeSH terms: Helicobacter Infections/microbiology
  18. Gunaletchumy SP, Seevasant I, Tan MH, Croft LJ, Mitchell HM, Goh KL, et al.
    Sci Rep, 2014 Dec 11;4:7431.
    PMID: 25503415 DOI: 10.1038/srep07431
    Helicobacter pylori infection results in diverse clinical conditions ranging from chronic gastritis and ulceration to gastric adenocarcinoma. Among the multiethnic population of Malaysia, Indians consistently have a higher H. pylori prevalence as compared with Chinese and Malays. Despite the high prevalence of H. pylori, Indians have a relatively low incidence of peptic ulcer disease and gastric cancer. In contrast, gastric cancer and peptic ulcer disease incidence is high in Chinese. H. pylori strains from Chinese strains predominantly belong to the hspEAsia subpopulation while Indian/Malay strains mainly belong to the hspIndia subpopulation. By comparing the genome of 27 Asian strains from different subpopulations, we identified six genes associated with risk of H. pylori-induced peptic ulcer disease and gastric cancer. This study serves as an important foundation for future studies aiming to understand the role of bacterial factors in H. pylori-induced gastro-duodenal diseases.
    Matched MeSH terms: Helicobacter Infections/microbiology*
  19. Gunaletchumy SP, Teh X, Khosravi Y, Ramli NS, Chua EG, Kavitha T, et al.
    J Bacteriol, 2012 Oct;194(20):5695-6.
    PMID: 23012278
    Helicobacter pylori is the main bacterial causative agent of gastroduodenal disorders and a risk factor for gastric adenocarcinoma and mucosa-associated lymphoid tissue (MALT) lymphoma. The draft genomes of 10 closely related H. pylori isolates from the multiracial Malaysian population will provide an insight into the genetic diversity of isolates in Southeast Asia. These isolates were cultured from gastric biopsy samples from patients with functional dyspepsia and gastric cancer. The availability of this genomic information will provide an opportunity for examining the evolution and population structure of H. pylori isolates from Southeast Asia, where the East meets the West.
    Matched MeSH terms: Helicobacter Infections/microbiology
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