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L Tay

Publications and source records attributed to L Tay.

At least 19 recordsLinked to original sources
PubMed2005

Rapid Identification of pathogenic rapidly growing mycobacteria by PCR-restriction endonuclease analysis.

INTRODUCTION: The accuracy and practicality of PCR-restriction endonuclease analysis (PRA) for rapid identification of pathogenic rapidly growing mycobacteria (RGM) isolates were evaluated. MATERIALS AND METHOD: PRA identification using an amplified 439-bp segment (amplicon) of the 65-kDa heat shock protein gene was compared to identification by conventional methods, for 39 clinically significant RGM isolates. RESULTS: The accuracy of PRA in the identification of RGM isolates was comparable to that of conventional methods. Moreover, PRA was able to identify RGM faster, within 2 to 3 working days compared to conventional methods which require 2 to 4 weeks to perform and complete different tests. CONCLUSION: PRA methodology could be easily incorporated into the clinical laboratory setting. This would be beneficial for the management of patients with infections due to pathogenic RGM.

Bacterial Proteins↗
PubMed2005

Use of ligase chain reaction in early diagnosis of tuberculous meningitis.

INTRODUCTION: Nucleic acid-based amplification tests are currently licensed only for the detection of Mycobacterium tuberculosis in pulmonary specimens. There are insufficient data for extrapulmonary specimens. The aim of this study is to investigate the diagnostic value of these investigations in tuberculous meningitis. MATERIALS AND METHODS: We performed a prospective study using a commercial ligase chain reaction DNA amplification technique [Ligase chain result (LCx) M. tuberculosis; Abbott Laboratories, Abbott Park, IL, USA] on cerebrospinal fluid (CSF) to diagnose tuberculous meningitis and compared the results with standard microbiological data. Conflicting cases were resolved according to the final clinical diagnosis. A total of 54 CSF specimens from 54 patients were tested. RESULTS: Six (11.1%) specimens were culture-positive for M. tuberculosis; of these, only 1 (1.9%) was smear-positive. The sensitivity, specificity, positive predictive value and negative predictive value of the LCx assay, compared with culture results, were 66.7%, 100%, 100% and 96%, respectively. After resolution according to clinical data, the sensitivity, specificity, positive predictive value and negative predictive value were 33.3%, 100%, 100% and 75%, respectively. All controls had negative LCx results. There were no false positives. CONCLUSION: LCx assay is highly specific and complements conventional laboratory diagnostic methods (CSF smear and culture) in the diagnosis of tuberculous meningitis. In the appropriate clinical context, a positive result is strongly suggestive of tuberculosis and could enable antituberculous treatment to be started immediately.

Humans↗
PubMed2004

Preliminary study on rapid identification of Mycobacterium tuberculosis complex isolates by the BD ProbeTec ET system.

The BD ProbeTec ET system for identification of Mycobacterium tuberculosis complex (MTBC) isolates from BACTEC 12B culture vials was evaluated in comparison with BACTEC NAP (p-nitro-alpha-acetylamino-beta-hydroxy-propiophenone) differentiation. Of 145 mycobacterial isolates tested, comprising 89 MTBC and 56 non-tuberculous mycobacteria (NTM), BD ProbeTec ET correctly identified 87 MTBC and 56 NTM but missed two MTBC. Three NTM were misidentified when NAP was incubated at 37 degrees C only. Overall sensitivity, specificity and positive and negative predictive values were respectively 97.8, 100, 100 and 96.6 % for the BD ProbeTec ET system and 100, 94.6, 96.7 and 94.6 % for NAP.

Bacteriological Techniques↗
PubMed2002

Early identification of Mycobacterium tuberculosis complex in BACTEC cultures by ligase chain reaction.

A total of 1431 acid-fast bacilli (AFB) in Bactec culture vials from 1427 patients was differentiated by the Bactec NAP method and tested by the LCx Mycobacterium tuberculosis ligase chain reaction system. In all, 1321 of 1325 M. tuberculosis complex (MTBC) isolates were correctly detected by the LCx assay. All the 106 non-tuberculous mycobacteria (NTM) isolates were negative by the LCx assay. No false MTBC-positive result was obtained from NTM isolates. However, the LCx assay failed to detect four MTBC isolates from one patient. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were 99.7, 100%, 100% and 96.4%, respectively. These data suggest that the LCx system can be used to identify MTBC in AFB-positive Bactec broth cultures when the growth index is > or = 100. The method gives a 100% PPV and allows a faster turnaround time for MTBC than the NAP test.

Humans↗
PubMed2000

Influence of immunogenicity on the pharmacokinetics of BMS-191352, a Pseudomonas exotoxin immunoconjugate, in rats and dogs.

BMS-191352 is an immunotoxin construct of modified Pseudomonas exotoxin conjugated to a fragment of the BR96 monoclonal antibody. We have investigated the potential for immunogenicity of BMS-191352 and its influence on the pharmacokinetics in rats and dogs. BMS-191352 was administered intravenously at doses of 0.75, 1.5, and 3 mg m(-2) once every two days for a total of five doses in rats, and 1.2, 2.4, and 4.8 mg m(-2) once every three days for a total of five doses in dogs. Blood samples were collected on days 1 and 9 in rats, and on days 1, 7, and 13 in dogs to monitor pharmacokinetics and anti-BMS-191352 immune response. Plasma concentrations of BMS-191352 and serum anti-BMS-191352 antibody titre were determined using ELISA assays. Pharmacokinetics were assessed using a non-compartmental method. Anti-BMS-191352 antibodies were not observed in rats within the drug administration interval. In all dogs, except one, markedly higher anti-BMS-191352 antibody titres were observed on day 13 compared with days 1 and 7, and its magnitude was independent of BMS-191352 dose. The single dose kinetics of BMS-191352 in rats and dogs were linear and the drug exposures were generally dose proportional. Mean half-life, total body clearance, and volume of distribution were 1.74 h, 3.35 mL min(-1) m(-2), and 0.27 Lm(-2) in rats, respectively, and 4.27 h, 6.28 mL min(-1) m(-2), 1.19 L m(-2) in dogs, respectively. The multiple-dose (day 9) kinetics in rats were similar to the single-dose kinetics. In dogs, the disposition of BMS-191352 on day 7 was similar to that on day 1; however, there was a precipitous reduction in the systemic drug exposure (by 5- to 110-fold) and marked increase in drug clearance on day 13. These changes in the kinetics of BMS-191352 were attributed to the generation of anti-BMS-191352 antibodies. In the one dog that did not develop anti-BMS-191352 antibodies, the pharmacokinetics were unchanged. The pharmacokinetics of BMS-191352 may be perturbed due to an immune response thus restricting the therapeutic utility of the immunotoxin.

ADP Ribose Transferases↗
PubMed1999

Validation of an ELISA for the quantitation of lanoteplase, a novel plasminogen activator.

An ELISA was developed and validated for the quantitation of lanoteplase in human citrated plasma. The ELISA employed a monoclonal anti-lanoteplase antibody absorbed onto 96-well microtiter plates to capture lanoteplase in citrated human plasma samples containing PPACK, a protease inhibitor. The captured lanoteplase was detected using a biotinylated rabbit anti-lanoteplase polyclonal antibody. The standard curve range in human plasma for the ELISA was 7-100 ng/ml. Assessment of individual standard curve variability indicated reproducible responses with r2 values of > or = 0.985. The accuracy (% DEV) and precision (%RSD) estimates for the ELISA based on the predicted values from quality control (QC) samples were within 7.3% and 11%, respectively. Cross-reactivity with t-PA was determined to be less than 11% by ELISA. The stability of lanoteplase was established in human citrated PPACK plasma for 24 hours at 4 degrees C, for 2 months at -20 degrees C, for 22 months at -70 degrees C, three weeks at room temperature, and through four freeze/thaw cycles. To quantify lanoteplase plasminogen activator (PA) activity, a commercially available chromogenic activity assay was also validated. This method and its application is described briefly here. The lanoteplase ELISA as well as the commercial activity method were successfully employed to evaluate the pharmacokinetic parameters of lanoteplase in support of clinical Phase II/III studies.

Amino Acid Chloromethyl Ketones↗
PubMed1999

Evaluation of three nucleic acid amplification methods for direct detection of Mycobacterium tuberculosis complex in respiratory specimens.

Two hundred thirty respiratory specimens from 230 patients were analyzed by using COBAS AMPLICOR PCR, Amplified Mycobacterium tuberculosis Direct Test, and ligase chain reaction methods. Results were compared with those of smear microscopy and radiometric culture (Bactec) methods. No significant differences were observed among the results of the three methods, which are acceptable for direct detection of M. tuberculosis complex in respiratory specimens.

Bacteriological Techniques↗
PubMed1998

Group B Streptococcal septicaemia/meningitis in neonates in a Singapore teaching hospital.

Our aims were to establish the incidence and clinical characteristics of early and late onset Group B Streptococcal (GBS) septicaemia in neonates in our hospital over a period of 1 year. Routine screening for maternal GBS was not standard practice in the hospital. GBS was isolated from high vaginal swabs (HVS) obtained antenatally or postnatally for risk factors as determined by the obstetrician or neonatologist in charge. Data obtained were analyzed separately and these did not form part of the study. By a system of clinical case review and follow-up, mail, telephone and home visits, the outcome of all 15,062 livebirths in the hospital over a 1-year period were verified and reported. Our results show a low incidence of GBS infection in neonates in the hospital: early onset disease was 0.265 per 1,000 livebirths and late onset a quarter of that. The majority of our cases of early onset GBS disease were in premature infants. Because of our low incidence, prophylaxis schedules would have to ensure an acceptably smaller number of mothers exposed to antibiotics over and above the current level and the cooperation of our obstetricians. We have devised a schedule incorporating a current PROM (prelabour premature rupture of membranes) protocol which would result in only an additional 2.2% of mothers requiring prophylactic antibiotics.

Age of Onset↗
PubMed1997

Evaluation of Amplicor- and IS6110-PCR for direct detection of Mycobacterium tuberculosis complex in Singapore.

One hundred and seventy-eight samples from 168 individuals were tested for Mycobacterum tuberculosis complex (Mtc) using Amplicor PCR, IS6110-PCR (in-house), acid fast (AF)-staining and culture. Thirty-one samples were positive by culture, but 37 samples were later resolved to be truly positive for Mtc. Of these, Amplicor detected 32 (86.5%), IS6110-PCR detected 31 (83.6%), and AF-staining 21 (56.8%). None of the 141 Mtc-negative samples was positive by these tests, thus giving 100% specificity. Although the IS6110-PCR was more sensitive than Amplicor in detecting spiked Mtc DNA, it was not more sensitive than the latter in detecting Mtc in clinical samples. Reasons likely to account for the PCR false negativity were (i) sample inoculum size, (ii) nonuniform samples due to clumping effect of Mtc and (iii) the absence of target gene sequences for IS6110-PCR. Culture negativity, on the other hand, was likely to be associated with nonviable Mtc. Amplicor PCR is promising for direct detection of Mtc. The IS6110-PCR, however, may not be as suitable because of possible existence of IS6110-deleted Mtc strain in Singapore.

DNA, Bacterial↗
PubMed1997

Comparison of polymerase chain reaction and conventional culture for the detection of legionellae in cooling tower waters in Singapore.

A total of 80 cooling tower water samples were investigated for legionellae using both cultural and polymerase chain reaction (PCR) methods. PCR was performed with the Perkin Elmer EnviroAmp Legionella kit. Forty-seven samples (58.8%) were found positive by both methods; 29 samples (36.3%) were positive by PCR only, while four samples (5%) showed PCR inhibition despite the adoption of the more stringent sample preparation protocol especially designed to eliminate inhibitors.

Air Conditioning↗
PubMed1994

Genome fingerprinting of Salmonella typhi by pulsed-field gel electrophoresis for subtyping common phage types.

The genomic DNA of 39 strains of Salmonella typhi isolated from local residents and patients who had visited countries in the Asian region was analysed for restriction fragment length polymorphisms (RFLP). Pulsed-field gel electrophoretic (PFGE) analysis of Xba I- and Spe I-generated genomic restriction fragments established 22 PFGE types whereas phage typing differentiated the 39 isolates into 9 distinct phage types. This study showed that PFGE is more discriminatory than phage typing as it is capable of subtyping S. typhi strains of the same phage types. Genetic relatedness among the isolates was determined. Seven major clusters were identified at SABs of > 0.80 and the remaining 13 isolates were distributed into minor clusters which were related at SABs of less than 0.80. In conclusion, PFGE analysis in conjunction with distance matrix analysis served as a useful tool for delineating common S. typhi phage types of diverse origins from different geographical locales and separated in time.

Adolescent↗
PubMed1994

Vibrio cholerae 0139 'Bengal' in Singapore.

Vibrio cholerae 0139 was isolated from five patients with cholera-like illness. All were imported cases. Laboratory investigations found our five isolates in show similar morphological, biochemical and serological characteristics to the V. cholerae 0139 strains causing epidemics in Bangladesh and India. Our isolates were toxin producers resistant to streptomycin and co-trimoxazole. No local transmission was known to have occurred following introduction of these imported cases.

Adult↗
PubMed1994

An outbreak of methicillin-resistant Staphylococcus aureus in a neonatal intensive care unit in Singapore: a 20-month study of clinical characteristics and control.

Methicillin resistant Staphylococcus aureus (MRSA) is a major infection control problem in many countries. There have been many reports of outbreaks in neonatal nurseries including, in our part of the world, Australia, Hong Kong and Malaysia. A recent outbreak of MRSA in the neonatal intensive care unit in the Kandang Kerbau Hospital, Singapore, presented us with the opportunity to study the clinical characteristics of the outbreak and the effects of infection control measures. Neonates admitted to the neonatal intensive care unit were studied over a 20-month period. They were all screened for nasal colonisation on admission and weekly thereafter. Infections were documented. Over this period there were altogether 2,576 admissions of which 85 infants had nasal colonisation with MRSA (3.3%) and 28 developed infections (1%). Although the majority of infants colonised by MRSA suffered no ill effects, 3 had septicaemia and 2 had septicaemia with osteomyelitis. There were no deaths. Standard infection control measures with barrier nursing and the use of mupirocin nasal ointment were ineffective, and control was achieved only after strict cohorting together with the use of mupirocin was instituted. This was done without additional costs to the department and without additional nurses or doctors.

Cross Infection↗
PubMed1993

A survey of postoperative wound infections in obstetrics and gynaecology--the Kandang Kerbau Hospital experience.

Postoperative wound infection is of great importance to both the surgeon and patient. This study covers 6,639 major operations in Kandang Kerbau Hospital, Singapore over a 12-month period. The overall wound infection rate was 2.26%. The highest wound infection rate occurred in hysterectomies and the lowest in laparoscopies. There was a good correlation between monthly caesarean wound infection rate and number of caesarean sections. Staphylococcus aureus was the most common organism isolated. The wound infection rate was also higher in crowded wards and among some surgeons. After distribution of the survey results, we noted a decrease in wound infection rate for some surgeons and a changing pattern in the use of antibiotics. A further study of other risk factors was encouraged.

Anti-Bacterial Agents↗
PubMed1992

Genome fingerprinting by pulsed-field gel electrophoresis and ribotyping to differentiate Pseudomonas aeruginosa serotype O11 strains.

The performance of ribotyping and pulsed-field gel electrophoresis was compared in the differentiation of a collection of 44 Pseudomonas aeruginosa serotype O11 strains isolated in seven hospitals in Singapore. Digestion of genomic DNA by EcoRI and SacI followed by Southern hybridization with the Pseudomonas aeruginosa 16S and 23S rRNA gene revealed seven distinct ribotypes. Ribotyping using a combination of both enzymes revealed 11 ribotypes. In contrast, electrophoretic analysis differentiated 41 different strain types among the 44 clinical isolates using either SpeI or DraI. Pulsed-field gel electrophoresis demonstrated greater sensitivity than ribotyping in the differentiation of Pseudomonas aeruginosa strains of the same ribotype and could thus be used alone in epidemiological investigations of hospital outbreaks of Pseudomonas aeruginosa serotype O11 infection.

DNA Fingerprinting↗
PubMed1992

Epidemiology and control of an outbreak of typhoid in a psychiatric institution.

An outbreak of typhoid caused by Salmonella typhi of the same Vi-phage type (D1) and of the same antibiogram was reported in a large psychiatric institution in Singapore. A total of 95 (4.8%) of the 1965 inmates were infected, 47 with symptoms and 48 asymptomatic. Transmission was through close person-to-person contact and not through contaminated food or water. The source of infection could not be established. The outbreak was brought under control by maintaining a high standard of environmental sanitation, active search for fever and diarrhoeal cases, identification of asymptomatic cases by rectal swabbing, and isolation of those found to be infected. Mass immunization with two doses of heat-phenol inactivated typhoid vaccine was also carried out concurrently. The vaccine was found to have an efficacy of 65.8% in preventing clinical illness.

Adult↗