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Biomedical subjects

K Y Yuen

Publications and source records attributed to K Y Yuen.

At least 199 records · Page 11Linked to original sources
PubMed1995

Acute pyelonephritis caused by Mycoplasma hominis.

A 59-yr-old male alcoholic with bilateral nephrocalcinosis and upper urinary tract stones presented with fever, acute abdominal signs and ascites. Laparotomy revealed the presence of 1.5 litres of ascitic fluid and confirmed right-sided acute pyelonephritis. Culture of urine from the renal pelvis obtained during surgery was positive for Mycoplasma hominis. Initial therapy with cefuroxime failed and doxycycline was later initiated when culture was positive for Mycoplasma hominis, with definite clinical improvement. This is an unusual case of acute pyelonephritis with peritoneal signs and ascites due to Mycoplasma hominis in an elderly male who had no recent history of urinary tract instrumentation.

Alcoholism↗
PubMed1995

Monitoring of leukocyte cytomegalovirus DNA in bone marrow transplant recipients by nested PCR.

A nested PCR assay for the detection of human cytomegalovirus (CMV) DNA was evaluated by weekly monitoring of blood samples taken from 101 bone marrow transplant (BMT) recipients. When peripheral blood leukocytes were used as the source of CMV DNA, even a modified assay with stringent temperature-cycling conditions was as sensitive as the standard assay. The sensitivity, specificity, and positive predictive value of two consecutively positive leukocytic PCR results with this modified assay in predicting CMV disease of 101 patients submitting 1,441 peripheral blood leukocyte samples were found to be 92.1, 63.5, and 60.3%, respectively. The positive predictive value of patients' seropositivity for CMV was 40%, while that of viremia was 72%. However, viremia followed CMV disease by a median of 1.5 days, while the first leukocytic positive PCR assay preceded disease by a median of 14 days. By use of the criteria of two consecutively positive PCR results instead of recipient CMV seropositivity for starting preemptive ganciclovir treatment, 38 of the 43 recipients with isolated single positive or negative assays (groups I and II) would be spared unnecessary ganciclovir treatment. Moreover, two other findings support the use of antiviral prophylaxis before engraftment in high-risk cases and subsequent preemptive treatment of patients with two consecutively positive PCR assays. First, for 7.9% of 76 patients with positive assays (groups II and III), the first positive PCR assay occurred before engraftment, which implied the presence of viral DNA in the blood (DNAemia) soon after transplantation. Second, isolated single positive assays which were clustered around the second to sixth weeks after transplantation were found for 18 patients (group II) and could represent abortive episodes of CMV infection.

Adolescent↗
PubMed1995

IS6110 based amplityping assay and RFLP fingerprinting of clinical isolates of Mycobacterium tuberculosis.

AIMS: To evaluate the usefulness of two IS6110 based typing methods, an amplityping assay and restriction fragment length polymorphism (RFLP) analysis, for fingerprinting respiratory isolates of Mycobacterium tuberculosis. METHODS: For amplityping, a pair of primers which amplify the intervening sequence between the repetitive insertion sequence IS6110 was used to generate a banding pattern which was confirmed by hybridisation. This assay was compared with conventional chromosomal DNA RFLP typing in the evaluation of 110 epidemiologically diverse isolates. RESULTS: Polymerase chain reaction (PCR) amplityping generated a single pattern in Hong Kong Chinese strains, but two and four diverse patterns in Filipino and Vietnamese strains, respectively, and could be completed within four days. When compared with chromosomal DNA RFLP typing, which took three weeks to complete, four different RFLP patterns could be seen among the Chinese strains, while seven patterns were found in the Filipino and Vietnamese strains. No change in amplityping or RFLP patterns was found in 36 sequential isolates from the same patients after anti-tuberculosis treatment for up to 12 months, despite the emergence of resistance in three of these strains. No specific amplityping or RFLP pattern could be related to different patterns of drug susceptibility. CONCLUSION: PCR amplityping could be used initially as a rapid typing method to distinguish strains originating from different localities. This could be important for investigation of outbreaks of tuberculosis--for example, in refugee camps.

Bacterial Typing Techniques↗
PubMed1995

Pulmonary infections in bone marrow transplantation: the Hong Kong experience.

The pattern of pulmonary infections in 59 consecutive bone marrow transplantations in Hong Kong was reviewed. Compared with published data from other marrow transplant units, we had a lower incidence of cytomegalovirus pneumonitis (1.7%) and a higher incidence of mycobacterial infections (5%). The latter is probably related to the high background prevalence of tuberculosis in the local population. Treatment with antituberculous drugs was effective.

Bacterial Infections↗
PubMed1995

Penicillium marneffei infection in a patient with SLE.

We describe a patient with SLE who was infected by the fungus Penicillium marneffei. She was initially misdiagnosed as having disseminated tuberculosis. The correct diagnosis was finally made by bone marrow culture and she responded to a prolonged course of amphotericin B, flucytosine and itraconazole. The clinical presentation and histology of penicilliosis are very similar to those of Mycobacterium tuberculosis. In Southeast Asia, penicilliosis should be considered as a differential diagnosis in patients with SLE who present with fever and lymphadenopathy.

Adult↗
PubMed1995

Rapid Mycobacterium species assignment and unambiguous identification of mutations associated with antimicrobial resistance in Mycobacterium tuberculosis by automated DNA sequencing.

OBJECTIVE: To develop and demonstrate the utility of automated DNA sequencing strategies for rapid and unambiguous identification of Mycobacterium species and mutations associated with antimicrobial resistance in Mycobacterium tuberculosis. DESIGN AND SPECIMENS: A 360-base pair segment of the gene (hsp65) encoding a 65-kd heat shock protein was characterized from 91 isolates assigned to 24 Mycobacterium species by traditional biochemical techniques. Areas of seven genes recently shown to contain mutations associated with antimicrobial resistance in M tuberculosis strains were also sequenced in a sample of 128 resistant organisms. Early positive BACTEC 460 cultures and acid-fast, bacterium-positive sputum specimens from patients with tuberculosis were also studied. RESULTS: Automated DNA sequencing identified species-specific polymorphism in the target segment of hsp65, successfully identified organisms to the species level in smear-positive sputum samples, and unambiguously characterized seven genes associated with antimicrobial resistance in M tuberculosis. CONCLUSIONS: Rapid identification of M tuberculosis and other Mycobacterium species is possible by automated DNA sequencing of a portion of hsp65. The technique is also feasible for analysis of some smear-positive sputum specimens. Unambiguous characterization of target segments of genes harboring mutations associated with antimicrobial resistance in M tuberculosis is possible from primary patient specimens. Taken together, the data demonstrate the feasibility of mycobacterial species identification and potential to identify mutations associated with antimicrobial resistance in less than 48 hours.

Alleles↗
PubMed1994

Serodiagnosis of Penicillium marneffei infection.

Diagnosis of Penicillium marneffei infection is often made late. We evaluated an indirect immunofluorescent antibody test for P marneffei in serum from 103 patients with persistent fever and from 78 normal subjects. Germinating conidia (initial tissue-invasion phase) and yeast-hyphae (tissue multiplication phase) forms were used as antigen. All 8 documented P marneffei cases (8%) had an IgG titre of 160 or more; the other 95 patients and all the healthy controls had an IgG titre of 40 or below. Blood culture was positive in only 1 case with HIV infection. Biopsy and culture of tissues were necessary for confirmation in the other 7 cases. The test could provide rapid presumptive diagnosis and supplement conventional culture.

Antibodies, Fungal↗
PubMed1994

Sequence variation of the amino-terminal antigenic domains of glycoprotein B of human cytomegalovirus strains isolated from Chinese patients.

To study the genetic variation of human cytomegalovirus (HCMV) in Asian populations, the amino-terminal antigenic domains of glycoprotein B of HCMVs isolated from ethnic Chinese transplant patients were cloned and sequenced. The nucleotide and encoded amino acid sequences were compared with published sequences of AD169 and Towne laboratory strains. Within the region sequenced, 9 out of 15 clinical isolates (60%) possessed a peptide configuration similar to that of strain AD169 while 6 isolates (40%) displayed a peptide configuration similar to that of strain Towne. The nucleotide and amino acid identities of AD169-like clinical isolates exhibited variations of 95.4%-99.6% and 95.4%-100% respectively, whereas the identities of Towne-like clinical isolates were within the range of 97.3%-100% and 96.6%-100% at the nucleotide and amino acid levels. The previously defined neutralizing epitope was conserved among the clinical isolates sequenced while unique non-conservative amino acid substitutions were detected in the non-neutralizing epitope within the amino-terminal antigenic domain of glycoprotein B of all AD169-like isolates (Y- > S) and one of the Towne-like isolates (R- > Q).

Amino Acid Sequence↗
PubMed1994

Association between polyomaviruria and microscopic haematuria in bone marrow transplant recipients.

The association of polyomaviruria and microscopic haematuria was studied by the use of electron microscopy (EM) and the polymerase chain reaction (PCR) in bone marrow transplant (BMT) recipients. The incidence of BK virus (BKV) and JC virus (JCV) excretion was further elucidated by means of restriction enzyme analysis of the PCR products. Polyomaviruses were detected in 43 (51.2%) of the 84 samples, 13 (30.2%) of which had a virus concentration detectable by EM. By typing with BamHI cleavage, 29 (67.4%) of the 43 positive patients were found to be excreting only BKV and the remaining 14% (32.6%) were excreting both BKV and JCV. Microscopic haematuria was present in 17 (20.2%) of 84 urine samples collected from different patients within 4 months post-transplant. The incidence of microscopic haematuria was significantly higher, 34.9% (P < 0.01), in patients with polyomaviruria than in those without (4.9%) but no difference was observed between the BKV-excreting and BKV/JCV-co-excreting patients. Microscopic haematuria was not present, however, in 53.8 and 65.2% of polyomavirus-excreting patients when virus was detected by EM and PCR respectively. While most episodes of microscopic haematuria observed were self-limiting and asymptomatic, three patients excreting polyomavirus had symptoms of cystitis and one of them had renal impairment that was otherwise unexplained. We thus conclude that polyomaviruses probably contribute to damage of urinary tract tissue in some BMT recipients.

Adolescent↗
PubMed1994

Changing epidemiology of human salmonellosis in Hong Kong, 1982-93.

A comprehensive analysis of the epidemiology of salmonellosis in a major hospital in Hong Kong from 1982-93 is reported. The trend of salmonella isolations over the past 12 years and changes in the occurrence of individual serotypes are delineated. A total of 5328 isolates were analyzed. Groups B (Salmonella typhimurium and S. derby) and E (S. anatum) were the commonest serogroups isolated from the intestinal tract in all age groups. A significant increase in the isolation of group D salmonellae has been observed since 1989. This is accounted for by a substantial rise in S. enteritidis isolation as seen in Western countries, despite a concomitant decrease of S. typhi. The extraintestinal isolation index (EII) is proposed as an index of the virulence potential of individual serotypes and serogroups. Group D salmonella was found to be the most invasive serogroup. While group D was the predominant serogroup isolated from extraintestinal sites in patients older than 1 year, group B serotypes (especially S. typhimurium) were more frequently seen in infants younger than 12 months.

Adolescent↗
PubMed1994

Adhesion and colonisation of Candida krusei on host surfaces.

Candida krusei is an emerging pathogen, especially in immunocompromised hosts. As the adherence of this organism both to host epithelial surfaces and to catheter and prosthetic surfaces appears to be important in the pathogenesis of superficial as well as systemic candidoses, the adhesion of 20 oral isolates of C. krusei and five oral isolates of C. albicans was compared with the following substrates: cultured (HeLa) epithelial cells, buccal epithelial cells (BEC) from healthy adults and bone marrow transplant patients, and acrylic (polymethylmethacrylate) surfaces. Animal experiments in Sprague Dawley rats were also conducted to evaluate the relative oral carriage rate of the two Candida spp. C. krusei isolates adhered in far greater numbers to acrylic surfaces than to either of the cell surfaces. Significant intra-species differences in C. krusei adhesion for acrylic surfaces were noted between 74 (39%) of 190 pair comparisons in contrast to 18 (9.5%) of 190 with HeLa surfaces (p < 0.05). A positive correlation was also observed between the adhesion of C. krusei isolates to HeLa cells and acrylic surfaces. Five isolates of C. albicans showed very low adherence to HeLa surfaces when compared with BEC obtained from either healthy individuals or bone marrow transplant patients. The adherence of C. albicans to BEC from the healthy individuals was c. 12-fold greater than that of C. krusei, a figure similar to the relative murine oral carriage rate of the two Candida spp.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Parenteral aminoglycoside therapy. Selection, administration and monitoring.

Aminoglycosides are potent water-soluble antibiotics, with peak concentration-dependent bactericidal activity against many pathogenic aerobic Gram-negative bacilli and Staphylococcus aureus. For systemic therapy, they must be given parenterally (intravenously or intramuscularly). In the body they remain largely extracellular, but penetration into cerebrospinal fluid and other secretions is meagre. They display trough concentration-dependent reversible nephrotoxicity and The commonly irreversible ototoxicity, which may present after treatment ceases. Gentamicin is the usual all-purpose agent of choice, tobramycin is slightly more effective against Pseudomonas aeruginosa infections, amikacin is the least susceptible to degradation by bacterial enzymes and netilmicin is probably the least toxic. Clinical and drug concentration monitoring have a role in therapy. Aminoglycosides exhibit enduring antibacterial activity (especially against Gram-negative bacilli) many hours after tissue concentrations become negligible. Appreciation of this postantibiotic effect is leading to replacement of conventional multiple daily doses by large single daily doses. The latter regimens confer at least equivalent efficacy and less risk of toxicity (particularly renal). However, single daily dosage may be unsuitable for immunocompromised patients and in those with infective endocarditis, where there is insufficient experience. Cotreatment with beta-lactams is commonly used in order to exploit the synergism between these agents, particularly in enterococcal endocarditis and severe Gram-negative sepsis. Liposomal aminoglycosides are promising parenteral formulations. After being taken up by phagocytes they reach the liver, spleen and sites of inflammation; subsequently they are gradually released. To substantiate the applicability of these hitherto experimental formulations, findings from clinical studies are keenly awaited.

Aminoglycosides↗
PubMed1993

Use of PCR in routine diagnosis of treated and untreated pulmonary tuberculosis.

AIMS: To assess the routine use of a polymerase chain reaction (PCR) assay for the direct detection of Mycobacterium tuberculosis in expectorated sputum specimens. METHODS: A pair of primers (20-mer) were designed to amplify the 38 kilodalton protein of M tuberculosis. The specificity of the assay was evaluated in 31 M tuberculosis strains, 15 atypical mycobacterium species, and several commensal bacteria of the upper respiratory tract. The assay was subsequently applied to 519 sputum specimens from 85 inpatients of a chest hospital in Hong Kong. RESULTS: An amplified product of 239 base pairs was found in all M tuberculosis strains, standard strains of M bovis, and M africanum but not in the other bacterial strains tested. For the 51 patients with pulmonary radiographic lesions, the diagnosis of pulmonary tuberculosis was subsequently confirmed by both culture and PCR in 41 of them. Five patients who were treated before admission were positive by PCR alone. All but one patient in the control group (patients with acute exacerbation of chronic obstructive airway diseases) or those with atypical mycobacterial diseases were PCR negative. The PCR remained positive after four weeks of anti-tuberculosis treatment in 29 patients, 16 of whom had become culture negative. CONCLUSION: This PCR assay is a useful technique for the diagnosis of untreated and recently treated cases of pulmonary tuberculosis.

Base Sequence↗
PubMed1993

Fatal necrotizing fasciitis due to Vibrio damsela.

A patient who succumbed to fulminant necrotizing fasciitis due to Vibrio damsela after injury by a rabbitfish is described. Despite the absence of any known underlying illness, he did not respond to appropriate antibiotic therapy and radical surgical intervention. This represents the first documented case of necrotizing fasciitis due to this organism, and is also the first reported case in Southeast Asia inflicted by rabbitfish.

Animals↗