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Kwok-Yung Yuen

Publications and source records attributed to Kwok-Yung Yuen.

At least 91 records · Page 5Linked to original sources
PubMed2003

AFLMP1 encodes an antigenic cel wall protein in Aspergillus flavus.

We have previously reported the cloning and characterization of the MP1 gene in Penicillium marneffei and the AFMP1 gene in Aspergillus fumigatus and their use for serodiagnosis of penicilliosis and aspergilloma and invasive aspergillosis, respectively. In this study, we describe the cloning of the AFLMP1 gene, which encodes the homologous antigenic cell wall protein in Aspergillus flavus, the most common Aspergillus species associated with human disease in our locality and in other Asian countries and the second most common Aspergillus species associated with human disease in Western countries. AFLMP1 codes for a protein, Aflmp1p, of 273 amino acid residues, with a few sequence features that are present in Mp1p and Afmp1p, the homologous antigenic cell wall proteins in P. marneffei and A. fumigatus, respectively, as well as several other cell wall proteins of Saccharomyces cerevisiae and Candida albicans. It contains a serine- and threonine-rich region for O glycosylation, a signal peptide, and a putative glycosylphosphatidylinositol attachment signal sequence. Specific anti-Aflmp1p antibody was generated with recombinant Aflmp1p protein purified from Escherichia coli to allow further characterization of Aflmp1p. Indirect immunofluorescence analysis indicated that Aflmp1p is present on the surface of the hyphae of A. flavus. Finally, it was observed that patients with aspergilloma and invasive aspergillosis due to A. flavus develop a specific antibody response against Aflmp1p. This suggested that the recombinant protein and its antibody may be useful for serodiagnosis in patients with aspergilloma or invasive aspergillosis, and the protein may represent a good cell surface target for host humoral immunity.

Amino Acid Sequence↗
PubMed2003

Invasive Streptococcus iniae infections outside North America.

Streptococcus iniae, a fish pathogen causing infections in aquaculture farms worldwide, has only been reported to cause human infections in North America. In this article, we report the first two cases of invasive S. iniae infections in two Chinese patients outside North America. While the first patient presented with bacteremic cellulitis, which is the most common presentation in previous cases, the second patient represents the first recognized case of S. iniae osteomyelitis. Both S. iniae strains isolated from the two patients were either misidentified or unidentified by three commercial systems and were only identified by 16S rRNA gene sequencing. Since no currently available commercial system for bacterial identification includes S. iniae in its database, 16S rRNA gene sequencing is the most practical and reliable method to identify the bacterium at the moment. In contrast to the distinct genetic profile described previously in clinical isolates from Canada, the present two isolates and a clinical isolate from a Canadian patient were found to be genetically unrelated, as demonstrated by pulsed-field gel electrophoresis. Morphologically, colonies of both isolates were also larger, more beta-hemolytic and mucoid, which differ from the usual morphotype described for S. iniae. Owing to their habit of cooking and eating fresh fish, the Asian population is strongly associated with S. iniae infections. As a result of the difficulty in making microbiological diagnosis in patients with cellulitis and the problem of identification in most clinical microbiology laboratories, the prevalence of S. iniae infections, especially in the Asian population, may have been under-estimated.

Adult↗
PubMed2003

Tsukamurella conjunctivitis: a novel clinical syndrome.

In this report, we describe the first three cases of Tsukamurella conjunctivitis in the literature. All three patients presented with congestion of one eye with small amounts of serous discharge for 1 to 2 days. All three recovered after 10 days of treatment with polymyxin B-neomycin or chloramphenicol eyedrops. Sequencing of the 16S rRNA genes of the three isolates recovered from the serous discharge of the three patients showed that they were all Tsukamurella species. The phenotypic characteristics of the isolate obtained from one patient best fit the phenotypic profile of Tsukamurella pulmonis, whereas those of the other two best fit that of Tsukamurella tyrosinosolvens.

Actinomycetales↗
PubMed2003

Seronegative bacteremic melioidosis caused by Burkholderia pseudomallei with ambiguous biochemical profile: clinical importance of accurate identification by 16S rRNA gene and groEL gene sequencing.

An aerobic gram-negative bacterium was isolated from the blood and sputum of an 84-year-old, chair-bound nursing home resident with acute bacteremic pneumonia. Although the phenotypic characteristics suggested that the bacterium could be Burkholderia pseudomallei, the Vitek 1 system (GNI+), which can successfully identify 99% of B. pseudomallei strains, showed that the bacterium was "unidentified." Immunoglobulin G against the lipopolysaccharide (LPS) of B. pseudomallei, as detected by an LPS-based enzyme-linked immunosorbent assay with 95% sensitivity, was negative in both the acute-phase and convalescent-phase sera. Sequencing of the groEL gene showed that the isolate was B. pseudomallei. Proper identification of the bacterium in this study is crucial, since there would be a radical difference in the duration of antimicrobial therapy.

Aged↗
PubMed2003

Clinical role of beta-lactam/beta-lactamase inhibitor combinations.

The use of beta-lactamase inhibitors in combination with beta-lactam antibiotics is currently the most successful strategy to combat a specific resistance mechanism. Their broad spectrum of activity originates from the ability of respective inhibitors to inactivate a wide range of beta-lactamases produced by Gram-positive, Gram-negative, anaerobic and even acid-fast pathogens. Clinical experience confirms their effectiveness in the empirical treatment of respiratory, intra-abdominal, and skin and soft tissue infections. There is evidence to suggest that they are efficacious in treating patients with neutropenic fever and nosocomial infections, especially in combination with other agents. beta-Lactam/beta-lactamase inhibitor combinations are particularly useful against mixed infections. Their role in treating various multi-resistant pathogens such as Acinetobacter species and Stenotrophomonas maltophilia are gaining importance. Although, generally, they do not constitute reliable therapy against extended-spectrum beta-lactamase producers, their substitution in place of cephalosporins appears to reduce emergence of the latter pathogens. Similarly, their use may also curtail the emergence of other resistant pathogens such as Clostridium difficile and vancomycin-resistant enterococci. beta-Lactam/beta-lactamase inhibitor combinations are generally well tolerated and their oral forms provide effective outpatient therapy against many commonly encountered infections. In certain scenarios, they could even be more cost-effective than conventional combination therapies. With the accumulation of so much clinical experience, their role in the management of infections is now becoming more clearly defined.

Animals↗
PubMed2002

DNA immunization using a secreted cell wall antigen Mp1p is protective against Penicillium marneffei infection.

None of the vaccines used in dimorphic fungal infections utilized the mucosal route for immunization, whereas only one utilized a secreted protein as antigen, despite knowing that infections caused by dimorphic fungi are usually acquired through inhalation. In this study, we investigated the usefulness of Mp1p (a secreted cell wall antigen encoded by MP1)-based vaccines for generation of protective immune responses against Penicillium marneffei infection using a mouse model, and compared the relative effectiveness of intramuscular MP1 DNA vaccine, oral mucosal MP1 DNA vaccine delivered by live-attenuated Salmonella typhimurium, and intraperitoneal recombinant Mp1p protein vaccine. The serum IgM level of the Mp1p protein vaccine group at day 7 and the serum IgG levels of the Mp1p protein vaccine group at days 7 and 21 were significantly higher than those of the other groups (P<0.0001). The serum IgG level of the MP1 DNA vaccine group was significantly higher than that of the corresponding control group and oral mucosal MP1 DNA vaccine group (one dose) at day 21 (P<0.0001 and <0.05, respectively). The groups of mice immunized with intramuscular MP1 DNA vaccine, oral mucosal MP1 DNA vaccine, and intraperitoneal Mp1p protein vaccine showed significantly higher Mp1p-specific lymphocyte proliferation index (LPI) than the control groups. The interferon-gamma (IF-gamma) levels of supernatant of splenic cell cultures obtained from mice after intramuscular MP1 DNA vaccine, mucosal MP1 DNA vaccine (three doses), or intraperitoneal Mp1p protein vaccine administration were higher than that which occurred after mucosal MP1 DNA vaccine (one dose) administration or those of controls. Interleukin-4 (IL-4) was not detectable in the supernatant of splenic cell cultures obtained from all groups of mice. The percentage survival of the mice immunized with intramuscular MP1 DNA vaccine, oral mucosal MP1 DNA vaccine (three doses), oral mucosal MP1 DNA vaccine (one dose), intraperitoneal recombinant Mp1p protein, oral live-attenuated S. typhimurium control, and intramuscular pJW4303 DNA control at day 60 after wild type P. marneffei challenge were 100, 60, 40, 40, 40, and 0%, respectively. The survival of mice in the MP1 DNA vaccine group was significantly better than those of the oral mucosal MP1 DNA vaccine (three doses) group (P<0.05), oral mucosal MP1 DNA vaccine (one dose) group (P<0.005), recombinant Mp1p protein group (P<0.005), S. typhimurium aroA strain group (P<0.05), and pJW4303 group (P<0.00001). Although, the mechanism by which intramuscular MP1 DNA vaccine offered the best protection against P. marneffei infection remains to be elucidated, the present observation prompted further clinical trials on the use of MP1 DNA immunization on asymptomatic human immunodeficiency virus carriers in P. marneffei endemic areas.

Administration, Oral↗
PubMed2002

Characterization of a novel insertion sequence, IS Bp1, in Burkholderia pseudomallei.

During screening for antigenic proteins in Burkholderia pseudomallei, a novel insertion sequence, IS Bp1, was found by sequence similarity searches. IS Bp1 contains two overlapping ORFs of 261 bp ( orfA) and 852 bp ( orfB), encoding 87 and 284 amino acid residues, respectively, and an imperfect inverted repeat. The putative protein encoded by orfA (OrfA) is similar to the OrfA in insertion sequences of the IS 3 family in other bacteria, showing 49% and 76% amino acid identity and similarity, respectively, with the transposase encoded by IS D1 of Desulfovibrio vulgaris vulgaris. The putative protein encoded by orfB (OrfB) is similar to the OrfB in insertion sequences of the IS 3 family in other bacteria, showing 43% and 62% amino acid identity and similarity, respectively, with the transposase encoded by IS 1222 of Enterobacter agglomerans. Sequence analysis of OrfA showed the presence of an alpha-helix-turn-alpha-helix motif, as well as the putative leucine zipper at its 3' end, for possible DNA binding to the terminal inverted repeats. Sequence analysis of OrfB showed the presence of a DDE motif of aspartic acid, aspartic acid, and glutamic acid, a highly conserved motif present in OrfB of other members of the IS 3 family. Furthermore, several other conserved amino acid residues, including the arginine residue located seven amino acids downstream from the glutamic acid residue, were observed. PCR amplification of the IS Bp1 gene showed a specific band in 65% of the 26 B. pseudomallei strains tested. Southern blot hybridization after XhoI or SacI digestion showed nine different patterns of hybridization. The number of copies of IS Bp1 in those strains that possessed the insertion sequence ranged from three to 12. Using several insertion sequences and a combination of insertion-sequence-based and non-insertion-sequence-based methods such as ribotyping will probably increase the discriminatory power of molecular typing in B. pseudomallei.

Bacterial Proteins↗
PubMed2002

Haemophilus segnis polymicrobial and monomicrobial bacteraemia identified by 16S ribosomal RNA gene sequencing.

This paper reports a case of Haemophilus segnis polymicrobial bacteraemia and a case of H. segnis monomicrobial bacteraemia identified by 16S ribosomal RNA gene sequencing. In the first case, a gram-negative aerobic coccobacillus was isolated with Streptococcus intermedius and S. sanguis from the blood culture of a 32-year-old intravenous drug addict with left thoracic empyema. In the second case, a gram-negative aerobic coccobacillus was isolated from the blood culture of an 82-year-old woman with Clostridium difficile colitis and septicaemic shock. Both gram-negative coccobacilli grew on chocolate agar as colonies of 1 mm in diameter after incubation for 24 h at 37 degress C in air with CO2 5%, but only to pinpoint sizes on blood agar under the same incubation conditions. Both strains were factor V-dependent, but not factor X-dependent. For the first isolate, the Vitek system (NHI) showed that it was 56% likely to be Actinobacillus actinomycetemcomitans and 40% Neisseria subflava; whereas the API system (NH) showed that it was 58% likely to be H. aphrophilus/paraphrophilus and 42% H. parainfluenzae. For the second isolate, the Vitek system (NHI) showed that it was 95% likely to be H. influenzae VIII; whereas the API system (NH) showed that it was 58% likely to be H. aphrophilus/paraphrophilus and 42% H. parainfluenzae. 16S rRNA gene sequencing showed that there were four base differences between isolate 1 and H. segnis and two base differences between isolate 2 and H. segnis, indicating that both isolates most closely resembled a strain of H. segnis. Only two cases of H. segnis bacteraemia were found in the English scientific literature, one in a case of infective endocarditis and the other in a case of pancreatic abscess. Including the present two cases, the overall mortality of H. segnis bacteraemia was 50%.

Adult↗
PubMed2002

Thermo-tolerant Campylobacter fetus bacteraemia identified by 16S ribosomal RNA gene sequencing: an emerging pathogen in immunocompromised patients.

Eight Campylobacter isolates that were able to grow at 25 degrees C and 42 degrees C and had the same biochemical profile were isolated from the blood of eight immunocompromised patients. Conventional biochemical tests were unable to determine whether they were isolates of thermo-tolerant C. fetus, H2S-negative C hyointestinalis, or a new Campylobacter species. Sequencing of the 16S ribosomal RNA genes showed that all eight isolates had the same nucleotide sequence and this was identical to that of C. fetus (GenBank accession no. AF219233). All eight patients had underlying disease and two died despite antibiotic treatment. Because of the ability of C fetus to grow over a wide range of temperatures and a higher incidence of bacteraemia by this organism than C. jejuni in the past 5 years in Hong Kong, thermo-tolerant C fetus may be an emerging pathogen in immunocompromised patients in the years to come.

Aged↗
PubMed2002

Potential benefit of plasma exchange in treatment of severe icteric leptospirosis complicated by acute renal failure.

Leptospirosis is a common zoonosis seen worldwide, but it is rare in our locality (Hong Kong). Clinical manifestations of leptospirosis are variable and may range from subclinical infection to fever, jaundice, hemorrhagic tendency, and fulminant hepato-renal failure. Severe hyperbilirubinemia and acute renal failure have been associated with high mortality. We report our experience with a patient who developed severe Weil's syndrome with marked conjugated hyperbilirubinemia and oliguric acute renal failure. These complications persisted despite treatment with penicillin and hemodiafiltration. Plasma exchange was instituted in view of the severe hyperbilirubinemia (970 micromol/liter). This was followed by prompt clinical improvement, with recovery of liver and renal function. The beneficial effects of plasma exchange could be attributed to amelioration of the toxic effects of hyperbilirubinemia on hepatocyte and renal tubular cell function. We conclude that plasma exchange should be considered as an adjunctive therapy for patients with severe icteric leptospirosis complicated by acute renal failure who have not shown rapid clinical response to conventional treatment.

Acute Kidney Injury↗
PubMed2002

Identification by 16S rRNA gene sequencing of Lactobacillus salivarius bacteremic cholecystitis.

An anaerobic, nonsporulating, gram-positive bacterium was isolated from blood and bile pus cultures of a 70-year-old man with bacteremic acute cholecystitis. The API 20A system showed that it was 70% Actinomyces naeslundii and 30% Bifidobacterium species, whereas the Vitek ANI system and the ATB ID32A Expression system showed that it was "unidentified." The 16S rRNA gene of the strain was amplified and sequenced. There were 3 base differences between the nucleotide sequence of the isolate and that of Lactobacillus salivarius subsp. salivarius or L. salivarius subsp. salicinius, indicating that the isolate was a strain of L. salivarius. The patient responded to cholecystectomy and a 2-week course of antibiotic treatment. Identification of the organism in the present study was important because the duration of antibiotic therapy would have been entirely different depending on the organism. If the bacterium had been identified as Actinomyces, penicillin for 6 months would have been the regimen of choice. However, it was Lactobacillus, and a 2-week course of antibiotic was sufficient.

Aged↗
PubMed2002

Detection of cell wall galactomannoprotein Afmp1p in culture supernatants of Aspergillus fumigatus and in sera of aspergillosis patients.

Mannoproteins are important and abundant structural components of fungal cell walls. The AFMP1 gene encodes a cell wall galactomannoprotein of Aspergillus fumigatus. In the present study, we show that Afmp1p is secreted into the cell culture supernatant at a level that can be detected by Western blotting. A sensitive enzyme-linked immunosorbent assay (ELISA) developed with antibodies against Afmp1p was capable of detecting this protein from the cell culture supernatant of A. fumigatus. The anti-Afmp1p antibody is specific since it fails to react with any protein from lysates of Aspergillus flavus, Aspergillus niger, Aspergillus terreus, Penicillium marneffei, Candida albicans, Cryptococcus neoformans, Blastomyces dermatitidis, and Histoplasma capsulatum by Western blotting. In addition, this Afmp1p antigen-based ELISA is also specific for A. fumigatus since the cell culture supernatants of the other eight fungi gave negative results. Finally, a clinical evaluation of sera from invasive aspergillosis patients indicates that 8 of 15 (53%) patients are Afmp1p antigen test positive. Furthermore, an Afmp1p antibody test was performed with these serum specimens. The combined antibody and antigen tests for invasive aspergillosis carry a sensitivity of 86.7% (13 of 15). The specificities of the tests are high since none of the 138 control sera, including 100 from normal blood donors, 20 from patients with penicilliosis marneffei, 6 from patients with candidemia, 8 from patients with typhoid fever, and 4 from patients with melioidosis, was positive by either test. In conclusion, the combined Afmp1p antibody and antigen tests are highly sensitive and specific for A. fumigatus invasive aspergillosis.

Antibodies, Fungal↗
PubMed2002

Streptococcus sinensis sp. nov., a novel species isolated from a patient with infective endocarditis.

A bacterium was isolated from the blood culture of a patient with infective endocarditis. The cells were facultative anaerobic, nonsporulating, gram-positive cocci arranged in chains. The bacterium grows on sheep blood agar as alpha-hemolytic, gray colonies of 0.5 to 1 mm in diameter after 24 h of incubation at 37 degrees C in ambient air. Growth also occurs in 10 or 40% bile and on bile esculin agar but not in 6% NaCl. No enhancement of growth is observed in 5% CO(2). It is nongroupable with Lancefield groups A, B, C, D, F, or G antisera and is resistant to optochin and bacitracin. The organism is aflagellated and is nonmotile at both 25 and 37 degrees C. It is Voges-Proskauer test positive. It produces leucine arylamidase and beta-glucosidase but not catalase, urease, lysine decarboxylase, or ornithine decarboxylase. It hydrolyzes esculin and arginine. It utilizes glucose, lactose, salicin, sucrose, pullulan, trehalose, cellobiose, hemicellulase, mannose, maltose, and starch. 16S rRNA gene sequencing showed that there were 3.6, 3.7, 4.3, 4.7, and 5.9% differences between the 16S rRNA gene sequence of the bacterium and those of Streptococcus gordonii, Streptococcus intermedius, Streptococcus constellatus, Streptococcus sanguis, and Streptococcus anginosus, respectively. The G+C content of it (mean plus minus standard deviation) was 53.0% plus minus 2.9%. Based on phylogenetic affiliation, it belongs to the mitis or anginosus group of Streptococcus. For these reasons a new species, Streptococcus sinensis sp. nov., is proposed, for which HKU4 is the type strain. Further studies should be performed to ascertain the potential of this bacterium to become an emerging cause of infective endocarditis.

Adult↗
PubMed2002

Relatively alcohol-resistant mycobacteria are emerging pathogens in patients receiving acupuncture treatment.

Acupuncture has been gaining popularity as a form of alternative medicine. In the past, only blood-borne viruses and anecdotal reports of bacterial infections have been associated with acupuncture. We report on four patients with mycobacterial infections complicating acupuncture who were encountered in a 2-year period. All had clinical and/or radiological lesions at acupuncture point- and meridian-specific locations. There was no other history of trauma or other clinical foci of infections, and the chest radiographs were normal. Histological studies of biopsy specimens of all four patients showed changes compatible with chronic inflammation, with granulomatous inflammation present in three patients and acid-fast bacilli present in two. Conventional biochemical tests and whole-cell fatty acid analysis for identification were inconclusive for all four nonpigmented mycobacteria recovered from tissue biopsies. 16S rRNA gene sequencing showed that the strains from two patients were Mycobacterium chelonae and that those from the other two were Mycobacterium nonchromogenicum. Alcohol resistance assay using the quantitative suspension test revealed that all four strains showed prolonged survival in 75% alcohol compared to other skin flora. Mycobacterial infections transmitted by acupuncture are an emerging problem. A high index of suspicion is essential to recognize this clinical syndrome, and strict implementation of proper infection control guidelines for acupuncture is mandatory.

2-Propanol↗
PubMed2002

Detection of antibodies specific to an antigenic cell wall galactomannoprotein for serodiagnosis of Aspergillus fumigatus aspergillosis.

Aspergilloma and invasive aspergillosis are important opportunistic infections caused by Aspergillus species, among which Aspergillus fumigatus is the most common species associated with human disease. We developed an enzyme-linked immunosorbent assay (ELISA)-based antibody assay with Afmp1p, a purified recombinant antigenic cell wall galactomannoprotein of A. fumigatus. Evaluation of the test with guinea pig sera against A. fumigatus and other pathogenic fungi indicated that this assay was specific for A. fumigatus. Clinical evaluation revealed that the assay was 100% sensitive for patients with aspergilloma and 33.3% sensitive for patients with invasive aspergillosis. No false-positive results were found for serum samples from 80 healthy blood donors, 6 patients with typhoid fever, 4 patients with melioidosis, 20 patients with penicilliosis marneffei, 5 patients with candidiasis, and 4 patients with cryptococcosis, indicating a high specificity of the test. Thus, this ELISA-based test for the detection of anti-Afmp1p antibody can be of significant value as a diagnostic for aspergillosis.

Animals↗
PubMed2002

Catheter-related Microbacterium bacteremia identified by 16S rRNA gene sequencing.

We describe the application of 16S rRNA gene sequencing in defining two cases of catheter-related Microbacterium bacteremia. In the first case, a gram-positive bacillus was isolated from both the blood culture and central catheter tip of a 39-year-old woman with chronic myeloid leukemia. The API Coryne system identified the isolate as 98.9% Aureobacterium or Corynebacterium aquaticum. In the second case, a gram-positive bacillus was recovered from five sets of blood cultures from both central catheter and percutaneous venipuncture of a 5-year-old girl with acute myeloid leukemia. The isolate was identified by the API Coryne system as 99.7% Cellulomonas or Microbacterium species. Further phenotypic tests failed to identify the two isolates. 16S rRNA gene sequencing showed 99.4% similarity between the first isolate and Microbacterium oxydans and 98.7% similarity between the second isolate and Microbacterium trichotecenolyticum, indicating that both isolates were Microbacterium species. Microbacterium infections are rarely reported in the literature. Although the central venous catheter was previously proposed to be a source of bacteremia, the first case in this report represents the first culture-documented case of catheter-related Microbacterium bacteremia.

Actinomycetales↗
PubMed2001

Cloning and characterisation of malE in Burkholderia pseudomallei.

No recombinant protein is available for serodiagnosis or skin test in the diagnosis of melioidosis. This report describes the cloning of the malE gene, which encodes an immunogenic protein of Burkholderia pseudomallei. Bi-directional DNA sequencing of malE revealed that the gene contained a single open reading frame encoding 416 amino acid residues with a predicted molecular mass of 44.4 kDa. BLAST analysis showed that the putative protein encoded by malE is homologous to the maltose-binding protein (MBP) of other bacteria. It has 48% and 63% amino acid identity and similarity with the MBP of Brucella abortus, and malE complementation assay showed that it partially complemented the function of the MBP of Escherichia coli. Several highly conserved regions among the MBP of B. pseudomallei, Br. abortus, Salmonella enterica serotype Typhimurium, E. coli and Enterobacter aerogenes were observed. These regions represent signatures A, B, C, D and F identified in the MBP of E. coli. Further sequence analysis revealed that the first 24 amino acid residues of the MBP of B. pseudomallei probably represent the N-terminal signal peptide of the protein. Similar to the signal peptide of the MBP of E. coli, Ent. aerogenes and S. Typhimurium, the MBP of B. pseudomallei contains two basic residues in the first eight amino acids, followed by a hydrophobic core, with the last three amino acids in the signal peptide being Ala-Gln-Ala, conforming to the consensus sequence Ala-X-Ala at positions -3 to -1 relative to the site of proteolytic cleavage for recognition by signal peptidase I. Further studies on serodiagnosis of melioidosis with recombinant MBP should be performed.

ATP-Binding Cassette Transporters↗