Displaying publications 41 - 60 of 118 in total

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  1. Expression of recombinant proteins of Orientia tsutsugamushi and their applications in the serodiagnosis of scrub typhus
    Tay ST, Rohani MY, Ho TM, Devi S
    Diagn Microbiol Infect Dis, 2002 Oct;44(2):137-42.
    PMID: 12458119
    In this study, recombinant proteins that encompassed the AD I-AD III regions of 56 kDa immunodominant gene of 2 Orientia tsutsugamushi (OT) serotypes; Gilliam and TA763 were expressed in Escherichia coli. Both recombinant proteins exhibited serologic cross-reactivity with the rabbit antisera against various OT serotypes, as evaluated by enzyme-linked immunosorbent assay (ELISA), but not against other rickettsial species, including Rickettsia typhi, R. prowazekii and TT118 SFG rickettsiae. The feasibility of using the recombinant proteins as a diagnostic reagent was further evaluated by ELISA using sera from blood donors and scrub typhus patients. The results suggested a higher affinity of the antihuman IgM than IgG with both recombinant proteins. The IgM ELISA findings were agreeable with the results of indirect immunoperoxidase (IIP) assay especially with sera of high antibody (1:1600). However, more than one antigen are probably needed for development of an effective assay for serodiagnosis of scrub typhus in endemic areas.
  2. Antibodies to Orientia tsutsugamushi, Rickettsia typhi and spotted fever group rickettsiae among febrile patients in rural areas of Malaysia
    Tay ST, Ho TM, Rohani MY, Devi S
    Trans R Soc Trop Med Hyg, 2000 9 7;94(3):280-4.
    PMID: 10974999
    A serosurvey was conducted in 1995-97 among 1596 febrile patients from 8 health centres in Malaysia for antibodies against Orientia tsutsugamushi (OT), Rickettsia typhi (RT) and TT118 spotted fever group rickettsiae (SFGR) by using an indirect immunoperoxidase assay. A total of 51.4% patients had antibody against at least 1 of those rickettsiae. Antibody to SFGR was most prevalent (42.5%), followed by RT (28.1%) and OT (24.9%). The seroprevalences of antibodies to SFGR, RT or OT alone were 12.4, 3.6 and 4.3%, respectively. Antibodies against more than 1 species of rickettsiae were presence in 31.1% of the patients, suggesting the possibility of co-infection, previous exposures or serological cross-reactivities. Seroprevalence of the various rickettsiae varied according to locality, with SFGR antibodies being the most prevalent in most areas. There was no significant association of prevalence of rickettsial antibody with gender. The seroprevalence of OT, SFGR and RT increased with patient age but an increase of antibody titre with age was not significant. Those working in the agricultural sectors had significantly higher seroprevalence of OT, SFGR and RT than those not related with agricultural activities. Scrub typhus remains a public health problem with an estimated annual attack rate of 18.5%. Tick typhus and murine typhus as shown in this serosurvey appear much more widespread than scrub typhus in this country.
  3. Fulltext Phylogeny and putative virulence gene analysis of Bartonella bovis
    Tay ST, Kho KL, Lye SF, Ngeow YF
    J Vet Med Sci, 2018 Apr 18;80(4):653-661.
    PMID: 29311425 DOI: 10.1292/jvms.17-0448
    Bartonella bovis is a small Gram-negative bacterium recognized as an etiological agent for bacteremia and endocarditis in cattle. As few reports are available on the taxonomic position of B. bovis and its mechanism of virulence, this study aims to resolve the phylogeny of B. bovis and investigate putative virulence genes based on whole genome sequence analysis. Genome-wide comparisons based on single nucleotide polymorphisms (SNP) and orthologous genes were performed in this study for phylogenetic inference of 27 Bartonella species. Rapid Annotation using Subsystem Technology (RAST) analysis was used for annotation of putative virulence genes. The phylogenetic tree generated from the genome-wide comparison of orthologous genes exhibited a topology almost similar to that of the tree generated from SNP-based comparison, indicating a high concordance in the nucleotide and amino acid sequences of Bartonella spp. The analyses show consistent grouping of B. bovis in a cluster related to ruminant-associated species, including Bartonella australis, Bartonella melophagi and Bartonella schoenbuchensis. RAST analysis revealed genes encoding flagellar components, in corroboration with the observation of flagella-like structure of BbUM strain under negative straining. Genes associated with virulence, disease and defence, prophages, membrane transport, iron acquisition, motility and chemotaxis are annotated in B. bovis genome. The flagellin (flaA) gene of B. bovis is closely related to Bartonella bacilliformis and Bartonella clarridgeiae but distinct from other Gram-negative bacteria. The absence of type IV secretion systems, the bona fide pathogenicity factors of bartonellae, in B. bovis suggests that it may have a different mechanism of pathogenicity.
  4. LC-MS analysis reveals biological and metabolic processes essential for Candida albicans biofilm growth
    Munusamy K, Loke MF, Vadivelu J, Tay ST
    Microb Pathog, 2021 Mar;152:104614.
    PMID: 33202254 DOI: 10.1016/j.micpath.2020.104614
    Candidiasis is the most common fungal infection associated with high morbidity and mortality among immunocompromised patients. The ability to form biofilm is essential for Candida albicans pathogenesis and drug resistance. In this study, the planktonic cell and biofilm proteomes of C. albicans SC5314 strain analyzed using Liquid Chromatography-Mass Spectrometry (LC-MS) were compared. In total, 280 and 449 proteins are annotated from the planktonic cell and biofilm proteomes, respectively. The biofilm proteome demonstrated significantly higher proportion of proteins associated with the endomembrane system, mitochondrion and cytoplasm than planktonic proteome. Among proteins detected, 143 and 207 biological processes are annotated, of which, 38 and 102 are specific to the planktonic cell and biofilm proteomes, respectively, while 105 are common biological processes. The specific biological processes of C. albicans planktonic cell proteome are associated with cell polarity, energy metabolism and nucleotide (purine) metabolism, oxido-reduction coenzyme metabolic process, monosaccharide and amino acid (methionine) biosynthesis, regulation of anatomical structure morphogenesis and cell cycling, and single organism reproduction. Meanwhile, regulation of cellular macromolecule biosynthesis and metabolism, transcription and gene expression are major biological processes specifically associated with C. albicans biofilm proteome. Biosynthesis of leucine, isoleucine, and thiocysteine are highlighted as planktonic-related pathways, whereas folate metabolism, fatty acid metabolism and biosynthesis of amino acids (lysine, serine and glycine) are highlighted as biofilm-related pathways. In summary, LC-MS-based proteomic analysis reveals different adaptative strategies of C. albicans via specific biological and metabolic processes for planktonic cell and biofilm lifestyles. The mass spectrometry data are available via ProteomeXchange with identifiers PXD007830 (for biofilm proteome) and PXD007831 (for planktonic cell proteome).
  5. Identification of a novel SHV-β-lactamase variant (SHV-144) in a Malaysian multidrug-resistant Klebsiella pneumoniae isolate
    Al-Marzooq F, Yusof MY, Tay ST
    Jpn J Infect Dis, 2013;66(6):555-7.
    PMID: 24270152
  6. Detection of IgM antibodies against Legionella pneumophila serogroup 1 in Malaysian blood donors and patients with respiratory illnesses: evaluation of enzyme-linked immunosorbent assay and indirect immunofluorescence assay
    Tay ST, Lakhbeer Singh HK, Ramasame SD, Vadivelu J
    Jpn J Infect Dis, 2009 Sep;62(5):409-10.
    PMID: 19762997
  7. Molecular investigation of Anaplasma spp. in domestic and wildlife animals in Peninsular Malaysia
    Koh FX, Panchadcharam C, Sitam FT, Tay ST
    Vet Parasitol Reg Stud Reports, 2018 08;13:141-147.
    PMID: 31014863 DOI: 10.1016/j.vprsr.2018.05.006
    Anaplasma spp. are Gram-negative obligate intracellular, tick-borne bacteria which are of medical and veterinary importance. Little information is available on Anaplasma infection affecting domestic and wildlife animals in Malaysia. This study investigated the presence of Anaplasma spp. in the blood samples of domestic and wildlife animals in Peninsular Malaysia, using polymerase chain reaction (EHR-PCR) assays targeting the 16S rRNA gene of Anaplasmataceae. High detection rates (60.7% and 59.0%, respectively) of Anaplasma DNA were noted in 224 cattle (Bos taurus) and 78 deer (77 Rusa timorensis and one Rusa unicolor) investigated in this study. Of the 60 amplified fragments obtained for sequence analysis, Anaplasma marginale was exclusively detected in cattle while Anaplasma platys/Anaplasma phagocytophilum was predominantly detected in the deer. Based on sequence analyses of the longer fragment of the 16S rRNA gene (approximately 1000 bp), the occurrence of A. marginale, Anaplasma capra and Candidatus Anaplasma camelii in cattle, Candidatus A. camelii in deer and Anaplasma bovis in a goat was identified in this study. To assess whether animals were infected with more than one species of Anaplasma, nested amplification of A. phagocytophilum, A. bovis and Ehrlichia chaffeensis DNA was performed for 33 animal samples initially screened positive for Anaplasmataceae. No amplification of E. chaffeensis DNA was obtained from animals investigated. BLAST analyses of the 16S rDNA sequences from three deer (R. timorensis), a buffalo (Bubalus bubalis) and a cow (B. taurus) reveal similarity with that of Candidatus Anaplasma boleense strain (GenBank accession no.: KX987335). Sequence analyses of the partial gene fragments of major surface protein (msp4) gene from two deer (R. timorensis) and a monitor lizard (Varanus salvator) show the detection of a strain highly similar (99%) to that of A. phagocytophilum strain ZJ-China (EU008082). The findings in this study show the occurrence of various Anaplasma species including those newly reported species in Malaysian domestic and wildlife animals. The role of these animals as reservoirs/maintenance hosts for Anaplasma infection are yet to be determined.
  8. Proteinase, phospholipase, biofilm forming abilities and antifungal susceptibilities of Malaysian Candida isolates from blood cultures
    Tay ST, Abidin IA, Hassan H, Ng KP
    Med Mycol, 2011 Jul;49(5):556-60.
    PMID: 21254967 DOI: 10.3109/13693786.2010.551424
    This study was conducted to determine the proteinase, phospholipase, and biofilm forming abilities of Candida isolates in blood cultures of specimens from patients at the University Malaya Medical Center, Kuala Lumpur, Malaysia. Proteinase and phospholipase activities were detected in 93.7% and 73.3%, respectively, of 15 Candida albicans isolates. Amongst the 26 non-C. albicans Candida isolates, proteinase and phospholipase activities were detected in 88.5% and 7.7% of the isolates, respectively. There was no significant difference in the expression levels of proteinase amongst the Candida isolates studied (P = 0.272), but the phospholipase activity of C. albicans was significantly higher than that of the non-C. albicans Candida isolates (P = 0.003). There was no significant difference in the biofilm forming abilities of C. albicans and non-C. albicans Candida isolates on the polystyrene microtiter wells (P = 0.379). In addition, the findings of this study demonstrate increased resistance of Candida isolates in biofilms to amphotericin and fluconazole, as compared to their planktonic counterparts.
  9. Detection of haemolytic activity of campylobacters by agarose haemolysis and microplate assay
    Tay ST, Devi S, Puthucheary SD, Kautner IM
    J Med Microbiol, 1995 Mar;42(3):175-80.
    PMID: 7884798
    There are several methods for the detection of haemolytic activity in campylobacters. However, we found the haemolytic effect of campylobacters on conventional blood agar plates to be variable, inconsistent and difficult to interpret. Blood agarose plates showed campylobacter haemolytic activity more clearly. The incubation conditions (temperature and gaseous) appear to be important for the expression of this activity. Ninety four percent of the Campylobacter isolates examined were found to be haemolytic by the microplate assay with minimal haemolytic units that ranged from 1 to 64. Haemolytic activity was detected only from live bacterial cultures and not from any of the 50 bacterial culture supernates, which suggests that campylobacters may possess a cell-associated haemolysin. The identification of such haemolytic activity in a large number of campylobacters (94%) suggests its potential role as a virulence factor in campylobacter gastroenteritis.
  10. Evaluation of PCR-RFLP analysis targeting hsp65 and rpoB genes for the typing of mycobacterial isolates in Malaysia
    Ong CS, Ngeow YF, Yap SF, Tay ST
    J Med Microbiol, 2010 Nov;59(Pt 11):1311-1316.
    PMID: 20688949 DOI: 10.1099/jmm.0.021139-0
    In this study, PCR-RFLP analysis (PRA) targeting hsp65 and rpoB gene regions was evaluated for the identification of mycobacterial species isolated from Malaysian patients. Overall, the hsp65 PRA identified 92.2 % of 90 isolates compared to 85.6 % by the rpoB PRA. With 47 rapidly growing species, the hsp65 PRA identified fewer (89.4 %) species than the rpoB PRA (95.7 %), but with 23 slow-growing species the reverse was true (91.3 % identification by the hsp65 PRA but only 52.5 % by the rpoB PRA). There were 16 isolates with discordant PRA results, which were resolved by 16S rRNA and hsp65 gene sequence analysis. The findings in this study suggest that the hsp65 PRA is more useful than the rpoB PRA for the identification of Mycobacterium species, particularly with the slow-growing members of the genus. In addition, this study reports 5 and 12 novel restriction patterns for inclusion in the hsp65 and rpoB PRA algorithms, respectively.
  11. Phenotypic and genotypic characterization of two closely related subgroups of Candida rugosa in clinical specimens
    Tay ST, Tan HW, Na SL, Lim SL
    J Med Microbiol, 2011 Nov;60(Pt 11):1591-1597.
    PMID: 21700741 DOI: 10.1099/jmm.0.032854-0
    In this study, six clinical isolates (two from blood, two from urine and one each from a bronchoalveolar lavage and a vaginal swab) were identified as Candida rugosa based on carbohydrate assimilation profiles using API 20C AUX and ID32 C kits (bioMérieux). Sequence analysis of the D1/D2 domain of the yeasts differentiated the isolates into two subgroups, A and B (three isolates per subgroup), which were closely related (99.1-99.6 % nucleotide similarity) to C. rugosa strain ATCC 10571. Compared with the C. rugosa type strain, the intergenic transcribed spacer (ITS) nucleotide similarity for subgroup A was only 89.2 % (29 mismatches and one deletion) and for subgroup B was 93.7 % (20 mismatches). All isolates grew green colonies on Oxoid Chromogenic Candida Agar, with darker pigmentation observed for subgroup A. All isolates were able to grow at 25-42 °C but not at 45 °C. The isolates had identical enzymic profiles, as determined by API ZYM (bioMérieux) analysis, and produced proteinase. High amphotericin MICs (≥1 µg ml(-1)) were noted for two isolates from each subgroup. Dose-dependent susceptibility to fluconazole (MIC 32 µg ml(-1)) was noted in a blood isolate. The biofilms of the isolates demonstrated increased resistance to amphotericin and fluconazole. The greater ITS sequence variability of subgroup A isolates is in support of this yeast being recognized as a distinct species; however, further verification using more sophisticated molecular approaches is required. A sequence comparison study suggested the association of subgroup A with environmental sources and subgroup B with clinical sources. Accurate identification and antifungal susceptibility testing of C. rugosa are important in view of its decreased susceptibility to amphotericin and fluconazole. The ITS region has been shown to be a valuable region for differentiation of closely related subgroups of C. rugosa.
  12. Fulltext Molecular survey and sequence analysis of Anaplasma spp. in cattle and ticks in a Malaysian farm
    Tay ST, Koh FX, Kho KL, Ong BL
    Trop Biomed, 2014 Dec;31(4):769-76.
    PMID: 25776603 MyJurnal
    This study was conducted to determine the occurrence of Anaplasma spp. in the blood samples of cattle, goats, deer and ticks in a Malaysian farm. Using polymerase chain reaction (PCR) and sequencing approach, Anaplasma spp. was detected from 81(84.4%) of 96 cattle blood samples. All blood samples from 23 goats and 22 deer tested were negative. Based on the analysis of the Anaplasma partial 16S ribosomal RNA gene, four sequence types (genotypes 1 to 4) were identified in this study. Genotypes 1-3 showed high sequence similarity to those of Anaplasma platys/ Anaplasma phagocytophilum, whilst genotype 4 was identical to those of Anaplasma marginale/ Anaplasma centrale/ Anaplasma ovis. Anaplasma DNA was detected from six (5.5%) of 109 ticks which were identified as Rhipicephalus (formely known as Boophilus) microplus ticks collected from the cattle. This study reported for the first time the detection of four Anaplasma sequence types circulating in the cattle population in a farm in Malaysia. The detection of Anaplasma DNA in R. microplus ticks in this study provides evidence that the ticks are one of the potential vectors for transmission of anaplasmosis in the cattle.
  13. Fulltext Enzymatic profiling of clinical and environmental isolates of Burkholderia pseudomallei
    Liew SM, Tay ST, Wongratanacheewin S, Puthucheary SD
    Trop Biomed, 2012 Mar;29(1):160-8.
    PMID: 22543616 MyJurnal
    Melioidosis has been recognized as an important cause of sepsis in the tropics. The disease caused by an environmental saprophyte Burkholderia pseudomallei, affects mostly adults with underlying immunocompromised conditions. In this study, the enzymatic profiles of 91 clinical and 9 environmental isolates of B. pseudomallei were evaluated using the APIZYM system, in addition to assessment of protease, phospholipase C and sialidase activities using agar plate methods and other assays. The activity of 10 enzymes - alkaline phosphatase, esterase, esterase lipase, lipase, leucine arylamidase, valine arylamidase, cystine arylamidase, acid phosphatase, naphthol-AS-BI-phosphohydrolase and N-acetyl-β-glucosaminidase were detected in >75% of the clinical isolates. The majority of B. pseudomallei isolates in this study exhibited protease and phospholipase activities. No sialidase activity was detected. Five Burkholderia thailandensis isolates had similar APIZYM profiles as B. pseudomallei clinical isolates except for the lower detection rate for N-acetyl-β-glucosaminidase. The subtle differences in the number of enzymes secreted and the levels of enzymatic activities of phenotypically identical clinical and environmental strains of B. pseudomallei give weight to the fact that the causative agent of melioidodis originates from the environment.
  14. Fulltext The integron prevalence of extended-spectrum beta-lactamase producing enterobacterial isolates in a Malaysian teaching hospital
    Ibrahim N, Wajidi MF, Yusof MY, Tay ST
    Trop Biomed, 2011 Dec;28(3):668-71.
    PMID: 22433898 MyJurnal
    The increased frequency of antibiotic resistance is known to be associated with the dissemination of integrons in the Enterobacteriaceae. This study determined the prevalence and type of integrons amongst 160 extended-spectrum beta-lactamase producing enterobacterial isolates kept in our culture collection. Integrons were detected in 98(61.3%) isolates, including 28(62.2%) Escherichia coli, 34(64.2%) Klebsiella spp., 27(61.4%), Enterobacter spp. and 9(50.0%) Citrobacter spp. investigated in this study. Restriction analysis of the integron gene fragments revealed that class I integron was the principal integron detected in 92(57.5%) of our isolates. Class II integron was detected in 6(3.8%) of our isolates, while no class III integron was detected in this study. The high rates of integron prevalence particularly of the class I integron in the E. coli and Klebsiella spp. concur with previous studies in other geographical regions. The higher (≥50%) integron prevalence of Citrobacter and Enterobacter isolates comparing to previous studies suggests the potential of these isolates as sources for dissemination of resistance determinants. The finding in this study serves as a basis for further study on the antibiotic resistance mechanisms of enterobacterial species in this teaching hospital.
  15. Revisiting oral thrush in South-East Asian patients: A review of published studies (2000-2020)
    Karajacob AS, Al-Maleki AR, Tay ST
    J Oral Pathol Med, 2022 Jan;51(1):98-105.
    PMID: 34859509 DOI: 10.1111/jop.13266
    BACKGROUND: Oral thrush, a clinical condition due to an overgrowth of Candida yeasts in the oral cavity, is prominent in patients with immunosuppression. As recent updates on oral thrush in South-East Asian (SEA) countries are lacking, this review aimed to address the epidemiology, clinical features and distribution of Candida species, based on published studies in SEA countries over the last two decades.

    METHODS: Published studies on oral candidiasis (2000-2020) were retrieved from PubMed, Scopus, ISI Web of Science and Google Scholar databases to provide information on the incidence and factors affecting oral thrush cases in SEA countries.

    RESULTS: A total of 22 cross-sectional studies involving 3697 subjects from five SEA countries were reviewed in this study. The most frequently reported population were human immunodeficiency virus (HIV)-infected patients. The overall incidence rates amongst HIV-infected patients ranged from 20.7% to 97.0%, while incidence rates ranging from 0% to 72.7% were recorded for non-HIV-infected populations. Pseudomembranous candidiasis and erythematous candidiasis were the most common clinical presentations of oral thrush lesions. Candida albicans was the most common species identified in SEA studies. As oral thrush assessments were made merely based on clinical diagnosis, culture results were not available for most studies.

    CONCLUSION: This review highlights that most studies reporting on oral candidiasis in SEA countries were based on HIV-positive patients. Data are still lacking on oral candidiasis amongst non-HIV immunocompromised and immunocompetent patients. Increasing awareness on the diagnosis, treatment and consequences of this infection, and improved laboratory methods are essential for the management of oral candidiasis in this region.

  16. Prevention practices of vaginitis among Malaysian women and its associated factors
    Wan Muda WM, Wong LP, Tay ST
    J Obstet Gynaecol, 2018 Jul;38(5):708-715.
    PMID: 29526143 DOI: 10.1080/01443615.2017.1405923
    Information on vaginal-related issues among Malaysian women is very limited. This study aimed to explore factors associated with preventive practices of vaginitis among Malaysian women. A cross-sectional computer-assisted telephone interview survey of a representative sample of multi-racial Malaysian women aged 18-50 years old was conducted from January to April 2014. Women from 1446 households responded to the survey and nearly one-third (32.1%) reported to have experienced vaginitis. In multivariate analyses, respondents in the urban locality were more likely to practice vaginitis prevention (OR = 1.40, 95% CI = 1.06-1.84) compared with those in the rural areas. Respondents who perceived low susceptibility to vaginitis were less likely to practice vaginitis prevention (OR = 0.72, 95% CI = 0.57-0.91) compared with responders who highly perceive susceptibility. Respondents who had no formal education were less likely to practice vaginitis prevention (OR = 0.16, 95% CI = 0.05-0.48) compared with those with tertiary education. This study showed that comprehensive education and health programmes need to focus on women with a low educational level, living in rural areas and women with low perceived susceptibility to vaginitis. Impact statement What is already known on this subject? Little is known about vaginitis issues among women in Malaysia. This study provides information regarding vaginitis among Malaysian women by looking at the factors associated with prevention practices. What do the results of this study add? From our study, factors associated with prevention practices were found to be educational level, locality, and perceived susceptibility of vaginitis. Those who perform fewer vaginitis prevention practices were women with a low educational level and those who live in rural areas. From the Health Belief Model, women with a low perceived susceptibility of vaginitis were less likely to carry out vaginitis prevention practices. What are the implications of these findings for clinical practice and/or further research? The findings may provide additional insights for policy makers and healthcare providers to deliver effective approaches in order to improve prevention practices of vaginitis among women in multi-ethnic communities. This study has identified points of interest which need to be put in attention for women's health section which has been overlooked in Malaysia.
  17. Fulltext Candida auris: A Mini Review on Epidemiology in Healthcare Facilities in Asia
    Thatchanamoorthy N, Rukumani Devi V, Chandramathi S, Tay ST
    J Fungi (Basel), 2022 Oct 26;8(11).
    PMID: 36354893 DOI: 10.3390/jof8111126
    Candida auris, a newly emerging healthcare-associated yeast pathogen from the Metschnikowiaceae family, was first described in the ear canal of an elderly Japanese patient in 2009. The yeast is one of the causative agents of candidemia, which has been linked with nosocomial outbreaks and high mortality rates in healthcare facilities worldwide. Since its first isolation, the occurrence of C. auris in six continents has becomes a grave concern for the healthcare professionals and scientific community. Recent reports showed the identification of five geographically distinct clades and high rates of antifungal resistance associated with C. auris. Till date, there are no effective treatment options, and standardized measures for prevention and control of C. auris infection in healthcare facilities. This leads to frequent therapeutic failures and complicates the eradication of C. auris infection in healthcare facilities. Thus, this review focuses on the recent understanding of the epidemiology, risk factors, diagnosis, transmission and prevention and control strategies of C. auris infection in healthcare facilities in Asia.
  18. Fulltext Correction: First isolation and identification of Cystobasidium calyptogenae from the oral samples of an elderly patient presenting with angular cheilitis
    Karajacob AS, Goh JPE, Kallarakkal TG, Tay ST
    Eur J Med Res, 2022 Dec 06;27(1):277.
    PMID: 36471451 DOI: 10.1186/s40001-022-00884-9
  19. Isolation and PCR detection of rickettsiae from clinical and rodent samples in Malaysia
    Tay ST, Rohani MY, Ho TM, Devi S
    Southeast Asian J Trop Med Public Health, 2002 Dec;33(4):772-9.
    PMID: 12757225
    Isolation of rickettsiae from patients' blood samples and organ samples of wild rodents from areas with high seroprevalence of rickettsial infections was attempted using cell culture assay and animal passages. L929 mouse fibroblast cells grown in 24 well tissue culture plate were inoculated with buffy coat of febrile patients and examined for the growth of rickettsiae by Giemsa, Gimenez staining and direct immunofluorescence assay. No rickettsiae were isolated from 48 patients' blood samples. No symptomatic infections were noted in mice or guinea pigs infected with 50 organ samples of wild rodents. There was no rickettsial DNA amplified from these samples using various PCR detection systems for Orientia tsutsugamushi, typhus and spotted fever group rickettsiae.
  20. Antigenic types of Orientia tsutsugamushi in Malaysia
    Tay ST, Rohani MY, Ho TM, Devi S
    Southeast Asian J Trop Med Public Health, 2002 Sep;33(3):557-64.
    PMID: 12693591
    The seroprevalence of various Orientia tsutsugamushi (OT) strains among Malaysian patients with suspected scrub typhus infections was determined using an indirect immunoperoxidase (IIP) assay. IgG against a single OT strain were detected in six sera (3 Karp, 1 Gilliam and 2 TC586), whereas IgM antibodies against a single OT strain (Gilliam) were noted in 3 sera (Gilliam). IgG reactive to all OT strains were present in 33 (47.1%) of the 70 sera and IgM reactive to all OT strains were present in 22 (78.6%) of the 28 sera. The fact that most sera were reactive to multiple OT strains suggests that group-specific antigens are involved in scrub typhus infections, whereas very few were due to strain-specific epitopes present on these strains. Peak IgG and IgM titers were noted more frequently against Gilliam, Karp, and TA763 strains: this suggests that these strains may be the commonest infecting strains among Malaysian patients. Two predominant OT polypeptides consistently reacted with patients' sera were the 70 kDa and 56 kDa proteins.
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