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K Y Yuen

Publications and source records attributed to K Y Yuen.

At least 73 records · Page 4Linked to original sources
PubMed2003

Coronavirus as a possible cause of severe acute respiratory syndrome.

BACKGROUND: An outbreak of severe acute respiratory syndrome (SARS) has been reported in Hong Kong. We investigated the viral cause and clinical presentation among 50 patients. METHODS: We analysed case notes and microbiological findings for 50 patients with SARS, representing more than five separate epidemiologically linked transmission clusters. We defined the clinical presentation and risk factors associated with severe disease and investigated the causal agents by chest radiography and laboratory testing of nasopharyngeal aspirates and sera samples. We compared the laboratory findings with those submitted for microbiological investigation of other diseases from patients whose identity was masked. FINDINGS: Patients' age ranged from 23 to 74 years. Fever, chills, myalgia, and cough were the most frequent complaints. When compared with chest radiographic changes, respiratory symptoms and auscultatory findings were disproportionally mild. Patients who were household contacts of other infected people and had older age, lymphopenia, and liver dysfunction were associated with severe disease. A virus belonging to the family Coronaviridae was isolated from two patients. By use of serological and reverse-transcriptase PCR specific for this virus, 45 of 50 patients with SARS, but no controls, had evidence of infection with this virus. INTERPRETATION: A coronavirus was isolated from patients with SARS that might be the primary agent associated with this disease. Serological and molecular tests specific for the virus permitted a definitive laboratory diagnosis to be made and allowed further investigation to define whether other cofactors play a part in disease progression.

Adult↗
PubMed2003

Facilitation of horizontal transfer of antimicrobial resistance by transformation of antibiotic-induced cell-wall-deficient bacteria.

It is universally accepted that the use of antibiotics will lead to antimicrobial resistance. Traditionally, the explanation to this phenomenon was random mutation and horizontal gene transfer and amplification by selective pressure. Subsequently, a second mechanism of antibiotic-induced antimicrobial resistance acquisition was proposed, when Davies et al. discovered that genes encoding antimicrobial resistance are present in bacteria that produce antibiotics, and during the process of antibiotic purification from these antibiotic-producing organisms, remnants of the organisms' DNA that contain antibiotic resistance genes are also co-extracted, and can be recovered in antibiotic preparations. In addition to selective pressure and antimicrobial resistance genes in antibiotic preparations, we hypothesize the third mechanism by which administration of antibiotics leads to antimicrobial resistance. beta-Lactams and glycopeptides damage bacteria by inhibiting cell wall murein synthesis. During the process, cell-wall-deficient forms are generated before the bacteria die. These cell-wall-deficient forms have an increased ability to uptake DNA by transformation. It has been demonstrated that plasmids encoding antimicrobial resistance of Staphylococcus aureus can be transformed to Bacillus subtilis after the B. subtilis was treated with penicillin or lysostaphin, a chemical that damage the cell walls of some Gram-positive bacteria; and that short treatment of Escherichia coli with antibiotics disturbing bacterial cell wall synthesis rendered the cells capable of absorbing foreign DNA. Since bacteria occupying the same ecological niche, such as the lower gastrointestinal tract, is common, bacteria are often incubated with foreign DNA encoding resistance coming from the administration of antibiotics or other bacteria that undergone lysis unrelated to antibiotic-induced killing. As few as a single antibiotic resistant gene is taken up by the cell-wall-deficient form, it will develop into a resistant clone, despite most of the other bacteria are killed by the antibiotic. If the hypothesis is correct, one should reduce the use of antibiotics that perturb bacterial cell wall synthesis, such as beta-lactams, which is the largest group being manufactured, in both humans and animals, in order to reduce the acquisition of antibiotic resistance through this mechanism. In contrast to the old theory that antibiotics only provide selective pressures for the development of antimicrobial resistance, antibiotics by themselves are able to generate the whole chain of events towards the development of antimicrobial resistance. Antibiotics provide a source of antimicrobial resistance genes, facilitate the horizontal transfer of antimicrobial resistance genes through facilitating transformation, and provide selective pressures for amplification of the antimicrobial resistance genes. That is perhaps an important reason why antimicrobial resistance is so difficult to control. Further experiments should be performed to delineate which particular type of beta-lactam antibiotics are associated with increase in transformation efficiencies more than the others, so that we can select those less resistance generating beta-lactam for routine usage.

Anti-Bacterial Agents↗
PubMed2003

Nontuberculous mycobacterial infections in Chinese hematopoietic stem cell transplantation recipients.

Between 1995 and 2002, nine cases of nontuberculous mycobacterium (NTM) were isolated from 462 allogeneic stem cell transplant (SCT) recipients (1.9%), and none from 139 autologous cases. They included three cases each of Mycobacterium fortuitum and M. chelonae, and single cases of M. scrofalaceum, M. gordonnae and M. avium complex. Seven cases were respiratory, including five cases requiring treatment, and two involved infected catheters and vascular conduits. Compared with nine cases of mycobacterium tuberculosis (MTB) isolated in the same period, NTM isolation occurred later after HSCT and involved more unrelated donors. Important risk factors for NTM infection included significant aGVHD (P=0.043), leukemia relapse (P=0.022), MUD and mismatch SCT (P<0.001) and existence of BO (P<0.001). Coinfection with aspergillus was common. Invasive NTM disease required prolonged antimicrobial treatment in five cases due to M. fortuitum and M. chelonae. With better MTB prophylaxis, intensive immunosuppression and better awareness, NTM has become an emerging threat in oriental allogeneic HSCT recipients. The cutoff between colonization and infection, and the threshold for starting treatment is unclear. NTM isolation is a marker for severe immunosuppression and poor prognosis. When there is doubt over species identity or extent of infection, broad-spectrum cover may be prudent.

Adult↗
PubMed2003

Evaluation of reverse transcription-PCR assays for rapid diagnosis of severe acute respiratory syndrome associated with a novel coronavirus.

The reverse transcription (RT)-PCR protocols of two World Health Organization (WHO) severe acute respiratory syndrome (SARS) network laboratories (WHO SARS network laboratories at The University of Hong Kong [WHO-HKU] and at the Bernhard-Nocht Institute in Hamburg, Germany [WHO-Hamburg]) were evaluated for rapid diagnosis of a novel coronavirus (CoV) associated with SARS in Hong Kong. A total of 303 clinical specimens were collected from 163 patients suspected to have SARS. The end point of both WHO-HKU and WHO-Hamburg RT-PCR assays was determined to be 0.1 50% tissue culture infective dose. Using seroconversion to CoV as the "gold standard" for SARS CoV diagnosis, WHO-HKU and WHO-Hamburg RT-PCR assays exhibited diagnostic sensitivities of 61 and 68% (nasopharyngeal aspirate specimens), 65 and 72% (throat swab specimens), 50 and 54% (urine specimens), and 58 and 63% (stool specimens), respectively, with an overall specificity of 100%. For patients confirmed to have SARS CoV and from whom two or more respiratory specimens were collected, testing the second specimen increased the sensitivity from 64 and 71% to 75 and 79% for the WHO-HKU and WHO-Hamburg RT-PCR assays, respectively. Testing more than one respiratory specimen will maximize the sensitivity of PCR assays for SARS CoV.

Humans↗
PubMed2003

Characterization of H9 subtype influenza viruses from the ducks of southern China: a candidate for the next influenza pandemic in humans?

A current view of the emergence of pandemic influenza viruses envisages a gene flow from the aquatic avian reservoir to humans via reassortment in pigs, the hypothetical "mixing vessel." Understanding arising from recent H5N1 influenza outbreaks in Hong Kong since 1997 and the isolation of avian H9N2 virus from humans raises alternative options for the emergence of a new pandemic virus. Here we report that H9N2 influenza viruses established in terrestrial poultry in southern China are transmitted back to domestic ducks, in which the viruses generate multiple reassortants. These novel H9N2 viruses are double or even triple reassortants that have amino acid signatures in their hemagglutinin, indicating their potential to directly infect humans. Some of them contain gene segments that are closely related to those of A/Hong Kong/156/97 (H5N1/97, H5N1) or A/Quail/Hong Kong/G1/97 (G1-like, H9N2). More importantly, some of their internal genes are closely related to those of novel H5N1 viruses isolated during the outbreak in Hong Kong in 2001. This study reveals a two-way transmission of influenza virus between terrestrial and aquatic birds that facilitates the generation of novel reassortant H9N2 influenza viruses. Such reassortants may directly or indirectly play a role in the emergence of the next pandemic virus.

Animals↗
PubMed2003

Gemella bacteraemia characterised by 16S ribosomal RNA gene sequencing.

AIMS: To define epidemiology, clinical disease, and outcome of gemella bacteraemia by 16S rRNA gene sequencing. To examine the usefulness of the Vitek, API, and ATB systems in identifying two gemella species. METHODS: All alpha haemolytic streptococci other than Streptococcus pneumoniae isolated from blood cultures during a six year period were identified by conventional biochemical methods, the Vitek system, and the API system. 16S rRNA gene sequencing was performed on all isolates identified by both kits as gemella with >or= 95% confidence or by either kit as any bacterial species with < 95% confidence. The ATB expression system was used to identify the two isolates that were defined as gemella species by 16S rRNA gene sequencing. RESULTS: Of the 302 alpha haemolytic streptococci other than S pneumoniae isolated, one was identified as Gemella morbillorum, and another as Gemella haemolysans by 16S rRNA gene sequencing. The patient with monomicrobial G morbillorum bacteraemia was a 66 year old man with community acquired infective endocarditis with septic thromboemboli. The patient with G haemolysans bacteraemia was a 41 year old woman with hospital acquired polymicrobial bacteraemia during the neutropenic period of an autologous bone marrow transplant for non-Hodgkin's lymphoma, the first case of its kind in the English literature. The API and ATB expression systems only identified the second strain as G haemolysans at 94% and 99% confidence, respectively, whereas the Vitek system identified none of the two strains correctly at > 70% confidence. CONCLUSIONS: Gemella bacteraemia is uncommon. 16S rRNA gene sequencing is the method of choice for identification of gemella and gemella-like isolates.

Adult↗
PubMed2003

Pseudobacteraemia in a patient with neutropenic fever caused by a novel paenibacillus species: Paenibacillus hongkongensis sp. nov.

AIMS: To characterise a strain of Gram negative aerobic straight or slightly curved rods (HKU3) isolated from the blood culture of a 9 year old Chinese boy with neutropenic fever and pseudobacteraemia. METHODS: The isolate was phenotypically investigated by standard biochemical methods using conventional biochemical tests, scanning electron microscopy, and transmission electron microscopy. Genotypically, the 16S rRNA gene of the bacterium was amplified by the polymerase chain reaction (PCR) and sequenced. The sequence of the PCR product was compared with known 16S rRNA gene sequences in the Genbank by multiple sequence alignment. The G + C content was determined by thermal denaturation. A phylogenetic tree was constructed by the PileUp method. RESULTS: The cells of the bacterial strain were aerobic, sporulating, Gram negative straight or slight curved rods. The bacterium grew on horse blood agar as non-haemolytic, grey colonies of 1 mm in diameter after 24 hours of incubation at 37 degrees C in ambient air. No enhancement of growth was seen in 5% CO(2). It grew at 50 degrees C as pinpoint colonies after 72 hours of incubation, but did not grow at 65 degrees C or on MacConkey agar. It was non-motile. It produced catalase (weakly positive) and cytochrome oxidase. It reduced nitrate, produced beta galactosidase, hydrolysed esculin, and utilised sodium acetate. A scanning electron micrograph of the bacterium showed straight or slightly curved rods. A transmission electron micrograph of the cell wall of the bacterium revealed multiple electron dense layers, including the outer membrane, middle murein layer, and inner cytoplasmic membrane, compatible with its Gram smear appearance. 16S rRNA gene sequencing showed that there were 7.7%, 8.0%, 8.2%, and 8.6% differences between the 16S rRNA gene sequence of the bacterium and those of Paenibacillus macerans, Paenibacillus borealis, Bacillus ehimensis, and Paenibacillus amylolyticus, respectively. The mean (SD) G + C content of the bacterium was 47.6 (2.1) mol%. Phylogenetically, it belongs to the genus paenibacillus (previously called group 3 bacillus). CONCLUSIONS: A bacterium that exhibited phenotypic and genotypic characteristics that are very different from closely related members of paenibacillus was the cause of pseudobacteraemia in a patient with neutropenic fever. A new species, Paenibacillus hongkongensis sp. nov. is proposed, for which HKU3 is the type strain.

Bacillaceae↗
PubMed2003

The complete genome sequence of severe acute respiratory syndrome coronavirus strain HKU-39849 (HK-39).

The complete genomic nucleotide sequence (29.7kb) of a Hong Kong severe acute respiratory syndrome (SARS) coronavirus (SARS-CoV) strain HK-39 is determined. Phylogenetic analysis of the genomic sequence reveals it to be a distinct member of the Coronaviridae family. 5' RACE assay confirms the presence of at least six subgenomic transcripts all containing the predicted intergenic sequences. Five open reading frames (ORFs), namely ORF1a, 1b, S, M, and N, are found to be homologues to other CoV members, and three more unknown ORFs (X1, X2, and X3) are unparalleled in all other known CoV species. Optimal alignment and computer analysis of the homologous ORFs has predicted the characteristic structural and functional domains on the putative genes. The overall nucleotides conservation of the homologous ORFs is low (<5%) compared with other known CoVs, implying that HK-39 is a newly emergent SARS-CoV phylogenetically distant from other known members. SimPlot analysis supports this finding, and also suggests that this novel virus is not a product of a recent recombinant from any of the known characterized CoVs. Together, these results confirm that HK-39 is a novel and distinct member of the Coronaviridae family, with unknown origin. The completion of the genomic sequence of the virus will assist in tracing its origin.

3' Untranslated Regions↗
PubMed2003

Staphylococcus aureus subcutaneous abscess complicating acupuncture: need for implementation of proper infection control guidelines.

We report a case of Staphylococcus aureus subcutaneous abscess centered over the Jizhong acupuncture point (DU 6) which lies along the Du (Back midline) meridian after acupuncture at the corresponding acupuncture point for low back pain. The patient recovered after surgical debridement and drainage and 5 weeks of cloxacillin therapy. Among the 16 anecdotal case reports of pyogenic bacterial infections complicating acupuncture described in the English literature (MEDLINE Search 1996-2002), S. aureus was documented to be the causative agent in 9 (56%). Three patients had septic arthritis, 2 had chronic osteomyelitis, 2 had abscess formation, 1 had chondritis, and 1 had infective endocarditis. Five patients had S. aureus bacteremia. All patients who recovered required prolonged antibiotic treatment of 5-6 weeks, and 6 required drainage and/or debridement. Overall, 3 patients (30%) died. S. aureus causes significant morbidity and mortality in patients who receive acupuncture treatment. More resources should be spent on implementation of proper infection control guidelines, as the money lost due to prolonged hospitalization and medication would far exceed that used for implementation.

Abscess↗
PubMed2003

Treatment of severe acute respiratory syndrome with lopinavir/ritonavir: a multicentre retrospective matched cohort study.

OBJECTIVES: To investigate the possible benefits and adverse effects of the addition of lopinavir/ritonavir to a standard treatment protocol for the treatment of severe acute respiratory syndrome. DESIGN: Retrospective matched cohort study. SETTING: Four acute regional hospitals in Hong Kong. PATIENTS AND METHODS: Seventy-five patients with severe acute respiratory syndrome treated with lopinavir/ritonavir in addition to a standard treatment protocol adopted by the Hospital Authority were matched with controls retrieved from the Hospital Authority severe acute respiratory syndrome central database. Matching was done with respect to age, sex, the presence of co-morbidities, lactate dehydrogenase level and the use of pulse steroid therapy. The 75 patients treated with lopinavir/ritonavir were divided into two subgroups for analysis: lopinavir/ritonavir as initial treatment, and lopinavir/ritonavir as rescue therapy. These groups were compared with matched cohorts of 634 and 343 patients, respectively. Outcomes including overall death rate, oxygen desaturation, intubation rate, and use of pulse methylprednisolone were reviewed. RESULTS: The addition of lopinavir/ritonavir as initial treatment was associated with a reduction in the overall death rate (2.3%) and intubation rate (0%), when compared with a matched cohort who received standard treatment (15.6% and 11.0% respectively, P<0.05) and a lower rate of use of methylprednisolone at a lower mean dose. The subgroup who had received lopinavir/ritonavir as rescue therapy, showed no difference in overall death rate and rates of oxygen desaturation and intubation compared with the matched cohort, and received a higher mean dose of methylprednisolone. CONCLUSION: The addition of lopinavir/ritonavir to a standard treatment protocol as an initial treatment for severe acute respiratory syndrome appeared to be associated with improved clinical outcome. A randomised double-blind placebo-controlled trial is recommended during future epidemics to further evaluate this treatment.

Adolescent↗
PubMed2002

Clinical spectrum of paradoxical deterioration during antituberculosis therapy in non-HIV-infected patients.

Paradoxical deterioration during antituberculosis therapy, defined as the clinical or radiological worsening of pre-existing tuberculous lesions or the development of new lesions in a patient who initially improves, remains a diagnostic dilemma. Although different clinical presentations of paradoxical response have been described, a systematic analysis of the entity in non-HIV-infected patients is lacking. Reported here are two cases of paradoxical deterioration in which sequential changes in lymphocyte counts and tuberculin skin test results are emphasized. In addition, 120 episodes of paradoxical response after antituberculosis treatment were reviewed. Of the total 122 episodes, 101 (82.8%) were associated with extrapulmonary tuberculosis. The median time from commencement of treatment to paradoxical deterioration was 60 days. The median time to onset of central nervous system manifestations (63 days) was longer than the time to onset of manifestations at other sites (56 days) ( P=0.02). Development of new lesions in anatomical sites other than those observed at initial presentation was observed in 31 (25.4%) episodes. A surge in the lymphocyte count, accompanied by an exaggerated tuberculin skin reaction, was observed in our patients during the paradoxical deterioration, analogous to the findings in HIV-positive patients. Treatment of the paradoxical response included surgical intervention (60.7%) and administration of steroids (39.3%). The use of steroids appeared to be safe in this series, as 95% of the Mycobacterium tuberculosis isolates were susceptible to first-line antituberculosis therapy.

Abscess↗
PubMed2002

Tuberculosis in blood and marrow transplant recipients.

Although one third of the world's population is infected with tuberculosis (TB), TB in blood and marrow transplant (BMT) recipients is relatively less well studied, as the incidence of TB is relatively low in developed countries with BMT units. Since the report of the first two cases in 1983, 52 cases of TB complicating BMT have been reported in the English literature from BMT centers in ten different countries. Not unexpectedly, the two largest series were reported from areas with a high incidence of TB in the general population, with about 45 cases per 10(5) inhabitants per year in Spain and about 100 cases per 10(5) inhabitants per year in Hong Kong respectively. The overall frequency of occurrence of TB in BMT recipients was 0.4% (52 cases among 13 881 BMT recipients), with a male:female ratio of 11:9 and median age of 33 (range 7-57). The incidence of TB in the general population is a major predictor of a higher frequency of occurrence in BMT recipients. Moreover, allogeneic transplantation, graft-versus-host disease, and total body irradiation were found to be risk factors associated with TB. Among the 48 cases in whom the time of manifestation were reported, only one case manifested during the neutropenic period (day 11). On the other hand, 11 cases (23%) manifest after engraftment but before day 100, and 36 (75%) manifest after day 100. The most important aspect towards making the diagnosis is a high index of suspicion, as TB occurred in relatively low frequencies especially in developed countries, and the clinical patterns usually mimic other more common infectious and non-infectious complications after BMT. As the incidence of drug resistant TB is increasing, we prefer to treat our patients for at least one year (as compared with six months in immunocompetent hosts) with four drugs in the first six months and two or three drugs for another six months. In those patients who could not tolerate oral medication, we used an intravenous regimen of rifampicin, ciprofloxacin, and amikacin until oral therapy could be instituted. The absence of relapse after termination of treatment in our patients suggested that secondary prophylaxis would not be necessary as long as immune function has been restored. With the rising incidence of TB in countries that previously enjoyed a very low prevalence of TB, attributed to the growing population of HIV-infected subjects with TB, and the changing patterns of population migration, it is important to bear a high index of suspicion of Mycobacterium tuberculosis as a pathogen in BMT recipients.

Adult↗
PubMed2002

Emergence of cotrimoxazole- and quinolone-resistant Campylobacter infections in bone marrow transplant recipients.

Clinical and microbiological data were collected prospectively from 704 patients who underwent bone marrow transplantation (BMT) during an 11-year period (1991-2001), and the first two cases of Campylobacter infection occurring in BMT recipients in the pre-engraftment period were identified. The two cases occurred on days 2 and 3 post-BMT, respectively. Both patients had Campylobacter jejuni enteritis, and one case was complicated by bacteraemia. In both cases the presenting symptoms were indistinguishable from hospital-acquired pre-engraftment diarrhoea, which is commonly caused by Clostridium difficile. Both of the Campylobacter jejuni isolates were resistant to cotrimoxazole and ciprofloxacin. Both patients responded to intravenous meropenem and subsequently had uneventful marrow engraftment.

Adolescent↗
PubMed2002

Clinicopathological features and risk factors of clinically overt haemorrhagic cystitis complicating bone marrow transplantation.

Haemorrhagic cystitis (HC) is an important complication after bone marrow transplantation (BMT). Overt HC (grade > or =2, gross haematuria, clot retention and impairment of renal function), clinically more important than mild and occult HC (grade 1, microscopic haematuria), leads to substantial morbidity and occasional mortality. We retrospectively analyzed 32 cases of clinically overt HC from a series of 236 BMT patients. Significant risk factors included the use of busulphan during conditioning, allogeneic BMT and acute GVHD. Logistic regression showed GVHD to be the most important risk factor. According to the time of engraftment, HC could be divided into pre- and post-engraftment subtypes. Pre-engraftment HC was brief, not more severe than grade 2, and subsided with supportive treatment. In contrast, post-engraftment HC was protracted, often of grade > or =3, associated with severe GVHD, and required surgical intervention in many cases. Polyoma BK viruria, but not adenoviruria, could be demonstrated in both types of HC. The increased severity and association with GVHD of post-engraftment HC suggested that attack of urothelium by immunocompetent cells, possibly directed against BK viral antigens, might play a pathogenetic role.

Adenoviridae↗
PubMed2002

Candida tropicalis fungaemia in adult patients with haematological malignancies: clinical features and risk factors.

Candida tropicalis fungaemia is a serious opportunistic infection. Eighteen consecutive patients with C. tropicalis fungaemia diagnosed within a five-year period were studied retrospectively. All patients had haematological malignancies treated by chemotherapy or bone marrow transplantation (BMT). Antifungal prophylaxis included nystatin (20 mg daily) for patients receiving chemotherapy, and fluconazole (200 mg daily) for patients undergoing BMT. Sixteen patients had refractory and advanced haematological malignancies. All patients were neutropenic, had central venous catheters, and were receiving treatment with broad-spectrum antibiotics at the time of fungaemia. Septic shock with skin emboli were the most common presenting features. In seven cases, fungaemia was preceded by a positive culture of C. tropicalis in the urine. Concomitant bacteraemia was found in 11 cases, of which six cases were due to Staphylococcus aureus. The overall mortality rate was 56%. The predominance of chemotherapy-treated patients developing fungaemia in this series might be attributable to the omission of fluconazole prophylaxis. The clinicopathologic features and risk factors identified in this study may help design better treatment strategies for this often-lethal complication.

Adolescent↗