Pak-Leung Ho

Queen Mary Hospital, Hong Kong, Hong Kong

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Publications (82)296.79 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: In Escherichia coli, fosfomycin resistance is uncommon and is mainly caused by mutations in the chromosomally encoded drug transporters (1).…
    Antimicrobial Agents and Chemotherapy 06/2014; · 4.57 Impact Factor
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    ABSTRACT: The study describes a proactive infection control approach to prevent nosocomial transmission of vancomycin-resistant enterococci (VRE) and tests if this approach is effective for controlling multiple-drug resistant organisms in a nonendemic setting. In response to the increasing prevalence of VRE in Hong Kong since 2011, we adopted a multifaceted assertive approach in our health care network. This included active surveillance culture, extensive contact tracing, directly observed hand hygiene in conscious patients prior to receiving meals and medications, stringent hand hygiene and environmental cleanliness, and an immediate feedback antimicrobial stewardship program. We report the occurrence of VRE outbreaks in our hospital after institution of these measures and compared with the concurrent occurrence in other public hospitals in Hong Kong. Between July 1, 2011 and November 13, 2013, VRE was identified in 0.32% (50/15,851) of admission episodes by active surveillance culture. The risk of VRE carriage was three times higher in patients with a history of hospitalization outside our hospital networks in the past 3 months (0.56% vs. 0.17%; p = 0.001) compared with those who were not. Extensive contact tracing involving 3277 patient episodes was performed in the investigation for the 25 VRE index patients upon whom implementation of contact precautions was delayed (more than 48 hours of hospitalization). One episode of VRE outbreak was identified in our hospital network, compared with the 77 VRE outbreaks reported in the other hospital networks (controls) without these proactive infection control measures. Our multifaceted assertive proactive infection control approach can minimize the nosocomial transmission and outbreak of VRE in a nonendemic area.
    Journal of the Formosan Medical Association 05/2014; · 1.00 Impact Factor
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    ABSTRACT: We compared a novel selective medium (SSL) with routine method (blood and chocolate agars) for detection of Staphylococcus lugdunensis in 990 clinical specimens (tissue, pus or wound swabs). Significantly more S. lugdunensis were detected on SSL (34/990) than on routine media (7/990. McNemar test P=0.001).
    Journal of clinical microbiology 04/2014; · 4.16 Impact Factor
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    ABSTRACT: Few studies have described how an expanding elderly population influences the burden of antimicrobial resistance in micro-organisms. This study aimed to investigate trends in aged-stratified extended-spectrum β-lactamases (ESBL)-positive Escherichia coli metrics in relation to an aging population. The antimicrobial resistance database of E. coli from a healthcare region in Hong Kong from 2003-2012 was retrospectively reviewed. Future trends in aged-stratified ESBL metrics were predicted up to 2022. Susceptibility results of clinical E. coli isolates from patients aged 0-74 years (n=17853) and aged ≥75 years (n=17047) were analyzed. For the period 2003-2012, 23.7% of the hospital admissions were of patients aged ≥75 years. However, approximately half of the annual ESBL-positive E. coli isolates were recovered from patients aged ≥75 years, being 55.0% (233/424) in 2003 and 56.0% (639/1142) in 2012. During this period of time, the annual prevalence and cumulative incidence of ESBL-positive E. coli in patients aged ≥75 years were significantly higher than in patients aged 0-74 years. From 2012 to 2022, it is predicted that ESBL-positive E. coli prevalence among patients aged 0-74 years and ≥75 years would increase from 25.4% to 50.2% and from 30.8% to 70.0% respectively. In 2022, the predicted ESBL-positive E. coli cumulative incidence would be 63.7 per 10,000 admissions and 178.7 per 10,000 admissions among patients aged 0-74 years and ≥75 years, respectively. In conclusion, a rapidly expanding elderly population would substantially add to the burden of ESBL.
    Journal of Medical Microbiology 04/2014; · 2.30 Impact Factor
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    ABSTRACT: To the Editor:In March 2013, a novel influenza A H7N9 virus of avian origin was reported to cause severe pneumonia in mainland China (1-3). While the great majority of patients were treated with oral oseltamivir, impaired gastrointestinal absorption in critically ill patients, the lack of virological response among patients requiring extracorporeal membrane oxygenation (ECMO) and detection of an amino acid change (arginine to lysine at residue 292 in N2) in the viral neuraminidase associated with drug resistance in two H7N9 strains are major concerns (1, 4). Here, we report a case of severe pneumonia due to avian influenza A H7N9 requiring ECMO support; there was rapid clinical and virological response following intravenous zanamivir therapy.On November 21, 2013, in Hong Kong, China, a 36-year-old Indonesian female began to have fever, malaise and cough. She had been previously healthy except for a history of vitiligo. She sought medical advice from two clinics and was given symptomatic treatment. She attended the accident and emergency department of a regional hospital in Hong Kong on November 27 when the symptoms deteriorated. Her temperature was 40.0°C, blood pressure.
    European Respiratory Journal 04/2014; · 6.36 Impact Factor
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    ABSTRACT: Besides seasonal and pandemic influenza (1), avian influenza viruses jumping from poultries to humans can also cause significant morbidity and mortality (2).…
    Journal of clinical microbiology 03/2014; · 4.16 Impact Factor
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    ABSTRACT: This study investigated the prevalence of IncX plasmid subtypes in commensal and pathogenic Escherichia coli isolates and the biological features of the IncX4 subtype. Two hundred twenty-five E. coli isolates from multiple sources (47 chicken, 41 pigs, 30 cattle and 107 humans), 2006-2012 were tested for presence of IncX1 to IncX5. Overall, the prevalence of IncX plasmids in chicken, pig, cattle and human isolates were 21.2% (10/47), 19.5% (8/41), 3.3% (1/30) and 4.8% (5/107) respectively. IncX4 was the most common subtype, followed by IncX1 and IncX3 while no IncX2 and IncX5 were found. Seven out of 16 (43.8%) IncX4 plasmids were found to carry blaCTX-M genes and six of them originating from different host sources (four chickens, one pig and one human) had identical or highly similar RFLP patterns. Three IncX4 carrying blaCTX-M plasmids from different host sources were investigated further. It was found that the IncX4 plasmids had little effect on bacterial host growth parameters after their introduction to J53 recipients. Conjugation experiments demonstrated that the IncX4 plasmids could be efficiently transferred at 30 -42oC at rates which were generally 102 to 105 folds higher than those for the epidemic IncFII plasmid carrying blaCTX-M (pHK01). In conclusion, the IncX plasmids are more common than previously recognized. The efficient transfer of IncX4 plasmid at different temperatures and lack of fitness burden on bacterial hosts highlight the ability of this plasmid replicon to be an important vehicle for dissemination of antimicrobial resistance.
    Journal of Medical Microbiology 03/2014; · 2.30 Impact Factor
  • Journal of microbiology, immunology, and infection = Wei mian yu gan ran za zhi 02/2014; · 1.63 Impact Factor
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    ABSTRACT: Background/Purpose The study describes a proactive infection control approach to prevent nosocomial transmission of vancomycin-resistant enterococci (VRE) and tests if this approach is effective for controlling multiple-drug resistant organisms in a nonendemic setting. Methods In response to the increasing prevalence of VRE in Hong Kong since 2011, we adopted a multifaceted assertive approach in our health care network. This included active surveillance culture, extensive contact tracing, directly observed hand hygiene in conscious patients prior to receiving meals and medications, stringent hand hygiene and environmental cleanliness, and an immediate feedback antimicrobial stewardship program. We report the occurrence of VRE outbreaks in our hospital after institution of these measures and compared with the concurrent occurrence in other public hospitals in Hong Kong. Results Between July 1, 2011 and November 13, 2013, VRE was identified in 0.32% (50/15,851) of admission episodes by active surveillance culture. The risk of VRE carriage was three times higher in patients with a history of hospitalization outside our hospital networks in the past 3 months (0.56% vs. 0.17%; p = 0.001) compared with those who were not. Extensive contact tracing involving 3277 patient episodes was performed in the investigation for the 25 VRE index patients upon whom implementation of contact precautions was delayed (more than 48 hours of hospitalization). One episode of VRE outbreak was identified in our hospital network, compared with the 77 VRE outbreaks reported in the other hospital networks (controls) without these proactive infection control measures. Conclusion Our multifaceted assertive proactive infection control approach can minimize the nosocomial transmission and outbreak of VRE in a nonendemic area.
    Journal of the Formosan Medical Association. 01/2014;
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    ABSTRACT: Yeast and mycobacteria can cause infections in immunocompromised patients and normal hosts. The rapid identification of these organisms can significantly improve patient care. There has been an increasing number of studies on using matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) for rapid yeast and mycobacterial identifications. However, studies on direct comparisons between the Bruker Biotyper and bioMérieux Vitek MS systems for the identification of yeast and mycobacteria have been limited. This study compared the performance of the two systems in their identification of 98 yeast and 102 mycobacteria isolates. Among the 98 yeast isolates, both systems generated species-level identifications in >70% of the specimens, of which Candida albicans was the most commonly cultured species. At a genus-level identification, the Biotyper system identified more isolates than the Vitek MS system for Candida (75/78 [96.2%]versus 68/78 [87.2%], respectively; P = 0.0426) and non-Candida yeasts (18/20 [90.0%]versus 7/20 [35.0%], respectively; P = 0.0008). For mycobacterial identification, the Biotyper system generated reliable identifications for 89 (87.3%) and 64 (62.8%) clinical isolates at the genus and species levels, respectively, from solid culture media, whereas the Vitek MS system did not generate any reliable identification. The MS method differentiated 12/21 clinical species, despite the fact that no differentiation between Mycobacterium abscessus and Mycobacterium chelonae was found by using 16S rRNA gene sequencing. In summary, the MALDI-TOF MS method provides short turnaround times and a standardized working protocol for the identification of yeast and mycobacteria. Our study demonstrates that MALDI-TOF MS is suitable as a first-line test for the identification of yeast and mycobacteria in clinical laboratories.
    Journal of Clinical Microbiology. 12/2013; 51(12).
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    ABSTRACT: Identification of hospitalized carbapenem-resistant Enterobacteriaceae (CRE)-positive patient is important in preventing nosocomial transmission. The objective of this study was to illustrate the implementation of proactive infection control measures in preventing nosocomial transmission of CRE in a healthcare region of over 3200 beds in Hong Kong between October 1, 2010 and December 31, 2011. The program included active surveillance culture in patients with history of medical tourism with hospitalization and surgical operation outside Hong Kong within 12 months before admission, and "added test" as an opportunistic CRE screening in all fecal specimens submitted to the laboratory. Outbreak investigation and contact tracing were conducted for CRE-positive patients. Serial quantitative culture was performed on CRE-positive patients and the duration of fecal carriage of CRE was analyzed. During the study period, a total of 6533 patients were screened for CRE, of which 76 patients were positive (10 from active surveillance culture, 65 from "added test", and 1 secondary case from contact tracing of 223 patients with no nosocomial outbreak), resulting in an overall rate of CRE fecal carriage of 1.2%. The median time of fecal carriage of CRE was 43 days (range, 13-119 days). Beta-lactam-beta-lactamase-inhibitors, cephalosporins, and fluoroquinolones were associated significantly with high fecal bacterial load when used 90 days before CRE detection, while use of cephalosporins, carbapenems, and fluoroquinolones after CRE detection are significantly associated with longer duration of carriage. The duration of fecal carriage of CRE also correlates significantly with the initial fecal bacterial load (Pearson correlation: 0.53; P = 0.02). Proactive infection control measures by enhanced surveillance program identify CRE-positive patients and data obtained are useful for the planning of and resource allocation for CRE control.
    Chinese medical journal 12/2013; 126(23):4504-9. · 0.90 Impact Factor
  • Journal of microbiology, immunology, and infection = Wei mian yu gan ran za zhi 10/2013; · 1.63 Impact Factor
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    ABSTRACT: The IncA/C plasmids are broad host-range vehicles which have been associated with wide dissemination of CMY-2 among Enterobacteriaceae of human and animal origins. Acquired metallo-β-lactamases (MBLs) such as the IMP-type enzymes are increasingly reported in multidrug-resistant Gram-negative bacteria worldwide, particularly in Enterobacteriaceae. We described the complete sequence of the first IMP-4-encoding IncA/C2 plasmid, pIMP-PH114 (151,885 bp), from a sequence type 1 Klebsiella pneumoniae strain that was recovered from a patient who was hospitalized in the Philippines. pIMP-PH114 consists of a backbone from the IncA/C2 plasmids, with the insertion of a novel Tn21-like class 1 integron composite structure (containing the cassette array bla IMP-4-qacG-aacA4-catB3, followed by a class C β-lactamase bla DHA-1 and the mercury resistance operon, merRTPCADE) and a sul2-floR encoding region. Phylogenetic analysis of the IncA/C repA sequences showed that pIMP-PH114 formed a subgroup with other IncA/C plasmids involved in the international spread of CMY-2, TEM-24 and NDM-1. Identical bla IMP-4 arrays have been described among different Enterobacteriaceae and Acinetobacter spp. in China, Singapore and Australia but the genetic context is different. The broad host range of IncA/C plasmids may have facilitated dissemination of the bla IMP-4 arrays among different diverse groups of bacteria.
    Current Microbiology 10/2013; · 1.52 Impact Factor
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    ABSTRACT: Yeast and mycobacteria can cause infections to both immunocompromised patients normal hosts. Rapid identification of these organisms could significantly improve patient care. There was increasing number of studies on using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) for rapid yeast and mycobacteria identifications. However, studies on direct comparison between the Bruker Biotyper and bioMérieux VITEK-MS system on identification of yeast and mycobacteria identification were limited.This study compared the identification performance of the two systems on 98 yeast and 102 mycobacteria isolates. Among the 98 yeast isolates, both systems could generate species level identifications in <70% specimens, of which Candida albicans was the most commonly cultured species. At genus level identification, the Biotyper system could identify more isolates than the VITEK-MS system for both Candida (75/78, 96.2% vs. 68/78, 87.2%, respectively, p=0.0426) and non-candida yeasts [18/20, 90.0% vs. 7/20, 35.0%, respectively, p=0.0008]. For mycobacteria identification, the Biotyper system could generate reliable identifications for 89 (87.3%) and 64 (62.8%) clinical isolates at genus and species level respectively from solid culture media, whereas the VITEK-MS system could not generate any reliable identification. The MS method could differentiate 12/21 clinical species, despite no differentiation between Mycobacterium abscessus and Mycobacterium chelonae could be found by using 16S rRNA gene sequencing.In summary, the MALDI-TOF MS method provides short turn-a-round time and standardized working protocol for both yeast and mycobacteria identification. Our study demonstrated that it is suitable to act as a first-line yeast and mycobacteria identification test in clinical laboratories.
    Journal of clinical microbiology 09/2013; · 4.16 Impact Factor
  • Journal of Antimicrobial Chemotherapy 07/2013; · 5.34 Impact Factor
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    ABSTRACT: The IncX family of plasmids has recently been expanded to include at least four subtypes, IncX1-IncX4. The revised classification provides an opportunity for improving our understanding of the sequence diversity of the IncX plasmids and the resistance genes they carried. We described the complete nucleotide sequence of a novel IncX3 plasmid, pKPC-NY79 (42,447 bp) from a sequence-type 258 Klebsiella pneumoniae strain that was isolated from a patient who was hospitalized in New York, United States. In pKPC-NY79, the plasmid scaffold and genetic load region were highly similar to homologous regions in pIncX-SHV (IncX3, JN247852) and the bla KPC carrying pKpQIL (IncFIIk, GU595196), respectively, indicating that it has possibly arisen through recombination of plasmids. The bla KPC-2 gene, as part of a transposon Tn4401a, was found within the genetic load region. The backbone of pKPC-NY79 differs from pIncX-SHV by a deletion involving the gene tandem hns-topB (encoding H-NS protein and topoisomerase III, respectively) and a putative ATPase gene. Unexpectedly, the impact of the hns-topB deletion on host fitness and plasmid stability was found to be small. In conclusion, the findings contribute to a better understanding of the plasmid platforms carrying bla KPC and of variations in the backbone of the IncX3 plasmids.
    Current Microbiology 06/2013; · 1.52 Impact Factor
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    ABSTRACT: Macrolide-resistant Mycoplasma pneumoniae (MRMP) is emerging worldwide, and has been associated with treatment failure. In this study, we use pyrosequencing to detect low frequency macrolide-resistant Mycoplasma pneumoniae (MRMP) quasispecies in respiratory specimens and compared the findings with Sanger sequencing and SimpleProbe PCR coupled to melting curve analysis (SimpleProbe PCR). Sanger sequencing, SimpleProbe PCR and pyrosequencing were successfully performed for 96.7% (88/91), 96.7% (88/91) and 93.4% (85/91) of the M. pneumoniae (MP)-positive specimens, respectively. A2063G transition was the only mutation identified. Pyrosequencing identified A2063G MRMP quasispecies populations in 78.8% (67/88) of the specimens. Only 38.8% (26/67) of these specimens with A2063G quasispecies detected by pyrosequencing were found to be A2063G by Sanger sequencing or SimpleProbe PCR. The specimens that could be detected by SimpleProbe PCR and Sanger sequencing had higher frequencies of MRMP quasispecies (51%-100%) than those that could not be detected by the two methods (1%-44%). SimpleProbe PCR correctly categorized all specimens identified as wild type or mutant by Sanger sequencing. The clinical characteristics of the patients were not significantly different when they were grouped by presence or absence of MRMP quasispecies while patients with MRMP identified by Sanger sequencing more often required switch from macrolide to alternative MP therapy. The clinical significance of mutant quasispecies should be investigated further with larger patient populations with specimens obtained before and after macrolide therapy.
    Journal of clinical microbiology 05/2013; · 4.16 Impact Factor
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    ABSTRACT: BACKGROUND: The relative contribution of long term care facilities (LTCFs) and hospitals in the transmission of methicillin-resistant Staphylococcus aureus (MRSA) is unknown. METHODS: Concurrent MRSA screening and spa type analysis was performed in LTCFs and their network hospitals to estimate the rate of MRSA acquisition among residents during their stay in LTCFs and hospitals, by colonization pressure and MRSA transmission calculations. RESULTS: In 40 LTCFs, 436 (21.6%) of 2020 residents were identified as 'MRSA-positive'. The incidence of MRSA transmission per 1000-colonization-days among the residents during their stay in LTCFs and hospitals were 309 and 113 respectively, while the colonization pressure in LTCFs and hospitals were 210 and 185 per 1000-patient-days respectively. MRSA spa type t1081 was the most commonly isolated linage in both LTCF residents (76/121, 82.8%) and hospitalized patients (51/87, 58.6%), while type t4677 was significantly associated with LTCF residents (24/121, 19.8%) compared with hospitalized patients (3/87, 3.4%) (p < 0.001). This suggested continuous transmission of MRSA t4677 among LTCF residents. Also, an inverse linear relationship between MRSA prevalence in LTCFs and the average living area per LTCF resident was observed (Pearson correlation -0.443, p = 0.004), with the odds of patients acquiring MRSA reduced by a factor of 0.90 for each 10 square feet increase in living area. CONCLUSIONS: Our data suggest that MRSA transmission was more serious in LTCFs than in hospitals. Infection control should be focused on LTCFs in order to reduce the burden of MRSA carriers in healthcare settings.
    BMC Infectious Diseases 05/2013; 13(1):205. · 3.03 Impact Factor
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    ABSTRACT: The matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) has been recently introduced in microbiology laboratories for bacterial and fungal identification. This technology could greatly improve the clinical management and guidance for chemotherapy.In this study, we evaluated the performance of two commercial MALDI-TOF MS systems, VITEK MS IVD (bioMerieux) and Microflex LT Biotyper (Bruker Daltonics) on direct bacterial identification on positive blood cultures with the use of the commercial MALDI Sepsityper extraction method. Among the 181 mono-microbial cultures, both systems could generate genus to species level identifications among >90% of specimens [Biotyper (177/181, 97.8%); VITEK MS IVD (167/181; 92.3%)]. Overall, the Biotyper system could generate significantly more accurate identifications than the VITEK MS IVD system (p=0.016 177 vs 167 out of 181 specimens). The Biotyper system was able to identify the minority species among polymicrobial blood cultures.An in-house extraction method was also evaluated towards the Sepsityper on both MALDI-TOF MS systems. The in-house method could generate more correct genus level identifications than the Sepsityper (96.7% vs 93.5%) on the Biotyper system, whereas they exhibited the same performance (88.0% vs 88.0%) on the VITEK MS IVD system.Our study confirmed the practical advantages of MALDI-TOF MS and our in-house extraction method could reduce the reagent cost to US$1 per specimen with shorter turn around-time of 3 hours, which is highly cost-effective for diagnostic microbiology service.
    Journal of clinical microbiology 03/2013; · 4.16 Impact Factor
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    ABSTRACT: The global epidemiology of multidrug-resistant Acinetobacter baumannii is dominated by a limited number of clones. Here, we announce the draft genome sequences of two multidrug-resistant A. baumannii strains, 1H8 and 4A3, representing the major epidemic clones, sequence type 92 (ST92) and ST96, respectively.
    Genome announcements. 01/2013; 1(3).

Publication Stats

1k Citations
296.79 Total Impact Points

Institutions

  • 2003–2014
    • Queen Mary Hospital
      Hong Kong, Hong Kong
  • 2011–2013
    • Lands Department of The Government of the Hong Kong Special Administrative Region
      Hong Kong, Hong Kong
  • 2003–2013
    • The University of Hong Kong
      • Department of Microbiology
      Hong Kong, Hong Kong
  • 2012
    • Princess Margaret Hospital, Hong Kong
      Hong Kong, Hong Kong
  • 2010
    • Tuen Mun Hospital
      • Department of Clinical Pathology
      Hong Kong, Hong Kong
  • 2003–2007
    • The Hong Kong University of Science and Technology
      • Department of Chemistry
      Kowloon, Hong Kong