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ABSTRACT We report the use of gold nanoparticles (Au NPs) for direct colourimetric polymerase chain reaction (PCR) detection of methicillin-resistant Staphylococcus aureus (MRSA) in clinical specimens. The colourimetric assay comprised of... more
ABSTRACT We report the use of gold nanoparticles (Au NPs) for direct colourimetric polymerase chain reaction (PCR) detection of methicillin-resistant Staphylococcus aureus (MRSA) in clinical specimens. The colourimetric assay comprised of 2 Au NP probes functionalized with Staphylococcus aureus 23S rRNA- and mecA-specific oligonucleotides. In this study, 72 clinical samples were tested, which included positive blood culture (n=23), urine (n=8), respiratory samples (n=23), as well as wound swabs, pus and body fluid (n=18). Results were recorded qualitatively by direct visual examination and quantitatively by UV-vis spectrophotometry. Using conventional bacterial culture as the gold standard, the sensitivity, specificity, positive predictive value and negative predictive value of this colourimetric assay were 97.14%, 91.89%, 91.89% and 97.14%, respectively, which were comparable to that of commercial real-time PCR assays with a lower cost per reaction. Our assay also showed good agreement with bacterial culture (κ=0.889). The overall detection limit was 500ng target amplicon, which was comparable to or better than other similar Au NP biosensors. Interestingly, our data revealed the possible relationship between Au NP probe-target hybridization site and assay performance, which might provide hints for design of the Au NP biosensors for nucleic acid detection. To conclude, our study was the first report on the use of Au NP colourimetric assay for direct detection of MRSA in various types of clinical specimens. Further evaluation of the assay is needed in large-scale trials which can also allow for some modifications to streamline the procedures for routine use.
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2009-2010 > Academic research: refereed > Refereed conference pape
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2004-2005 > Academic research: refereed > Refereed conference pape
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2004-2005 > Academic research: refereed > Refereed conference pape
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SummaryThis study describes the isolation and characterization of methicillin‐resistant Staphylococcus aureus (MRSA) from slaughtered pigs sampled from local markets in Hong Kong. The nares of 400 slaughtered pigs were cultured and MRSA... more
SummaryThis study describes the isolation and characterization of methicillin‐resistant Staphylococcus aureus (MRSA) from slaughtered pigs sampled from local markets in Hong Kong. The nares of 400 slaughtered pigs were cultured and MRSA isolates characterized for the presence of antibiotic‐resistance determinants, toxins and SCCmec and spa types using PCR. Clonality was investigated using PFGE and MLST. The prevalence of MRSA colonization of slaughter pigs was 39.3%, the majority (92%) harbouring SCCmec type IVb. Of the 157 samples yielding MRSA, 13 had two distinct MRSA strains present. Spa type t899 was predominant, with only 5/170 isolates displaying closely related types (t4474, t1939, t2922 and t5390). PFGE with sma1 and MLST confirmed the strains as ST9. Most isolates were multidrug resistant. Tetracycline resistance (97%) was mainly attributable to tet(K) with only 3% of isolates additionally harbouring tet(M). Resistance to erythromycin (89%) and chloramphenicol (71%) was associated with the presence of erm(C), and fex(A), respectively. No strains carried cfr and there was no resistance to linezolid, although minimum inhibitory concentration (MICs) were close to the resistance break point. Resistance to clindamycin (99%), ciprofloxacin(78%), quinopristin–dalfopristin (44%) and cotrimoxazole (32%) was common, but remained low for fusidic acid (4%) and rifampicin (2%). All strains were negative for PVL, exfoliative, and enterotoxins. This survey confirmed the uniformity of MRSA isolates in pigs from several regions of China, in contrast to more diversified characteristics reported in European studies. Colonization rates were higher than previously reported. Isolates were resistant to a wide range of antibiotics, but resistance was not detected to linezolid, nitrofurantoin, vancomycin or tigecycline. Although the clinical importance of ST9 in humans is uncertain, continued surveillance, in particular of those occupationally‐exposed, is recommended.
Research Interests: Microbiology, Biology, Hong Kong, Medicine, Biological Sciences, and 10 morePhenotyping, Staphylococcus aureus, Genotyping, Fusidic Acid, Linezolid, Clindamycin, Veterinary Public Health ZOONOSES, Methicillin Resistant Staphylococcus Aureus, Multilocus sequence typing, and Medical and Health Sciences
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2003-2004 > Academic research: refereed > Refereed conference pape
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2006-2007 > Academic research: refereed > Refereed conference pape
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Awarded a prize by ANSORP for best poster of conference2000-2001 > Academic research: refereed > Refereed conference pape
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2005-2006 > Academic research: refereed > Refereed conference pape
Research Interests: Medicine and Contact Lens
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2008-2009 > Academic research: refereed > Refereed conference pape
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2004-2005 > Academic research: refereed > Refereed conference pape
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15th European Congress of Clinical Microbiology and Infectious Diseases, Copenhagen, Denmark, 2-5 April 20052004-2005 > Academic research: refereed > Refereed conference pape
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Proper drying of hands after washing is an integral part of hand hygiene. An experimental study on 30 subjects using multiple comparisons of six hand drying methods including 1) drying on own clothes, 2) drying with one paper towel, 3)... more
Proper drying of hands after washing is an integral part of hand hygiene. An experimental study on 30 subjects using multiple comparisons of six hand drying methods including 1) drying on own clothes, 2) drying with one paper towel, 3) drying with two paper towels, 4) drying with a warm air dryer while holding hands stationary for 20 s, 5) drying with a warm air dryer while hand rubbing for 20 s, and 6) drying with a jet air dryer until complete dryness was achieved. It aimed to determine the effectiveness of different hand drying methods for removing bacteria from washed hands, so as to identify the optimum method using minimum resources. Our study demonstrated that the use of jet air dryers is the best method to eliminate bacteria on hands, whereas drying hands on one’s own clothes is the least effective. Drying hands in a stationary position could remove more bacteria than rubbing hands when using a warm air dryer for 20 s, which mimics people’s usual hand-drying practice. No sig...
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2011-2012 > Academic research: refereed > Refereed conference pape
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2007-2008 > Academic research: not refereed > Invited conference pape
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2003-2004 > Academic research: refereed > Refereed conference pape
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2005-2006 > Academic research: refereed > Refereed conference pape
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2003-2004 > Academic research: refereed > Refereed conference pape
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2008-2009 > Academic research: not refereed > Invited conference pape
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PURPOSE To evaluate the risk factors associated with contamination of lens cases in a group of orthokeratology (ortho-k) lens wearers. METHOD Ortho-k patients attending the Contact Lens Clinic of the Hospital were required to complete a... more
PURPOSE To evaluate the risk factors associated with contamination of lens cases in a group of orthokeratology (ortho-k) lens wearers. METHOD Ortho-k patients attending the Contact Lens Clinic of the Hospital were required to complete a checklist about their routine daily care and handling of lens cases. Their cases were then collected for analysis. Contamination was evaluated by determining the optical density (OD) of crystal violet stained biofilm present in the cases. OD values were divided into three groups, lower, middle, and upper tertiles, and associations between risk factors were determined by multivariate analysis. RESULTS A total of 194 subjects were recruited. Twenty-five subjects used cylindrical lens cases (CC), 98 flat cases with ridges (FCR), and 71 flat cases without ridges (FC). FCRs were the most heavily contaminated and CC showed least contamination (FCR > FC, OR 2.16, CI 1.11-4.18, p = 0.023; FCR > CC, OR 8.86, CI 2.97-26.44, p <0.001; FC > CC, OR 2.33, CI 1.35-12.45, p = 0.013). Replacing lens cases monthly significantly reduced the risk of high contamination (OR 0.013, CI 0.06-0.30, p < 0.001), compared to those used for three months. Cases that were not rinsed (OR 3.44, CI 1.50-7.86, p = 0.003) or rinsed by other methods (OR 4.07, CI 1.67-9.92, p = 0.002) had significantly more contamination, compared to those rinsed with multipurpose solution. Lens cases, which were not dried (OR 11.36, CI 2.06-62.93, p = 0.005) or air-dried (OR 8.71, CI 1.16-65.56, p = 0.036), showed more contamination compared to those wiped with tissue daily. CONCLUSION Case design (cylindrical), monthly replacement, daily rinsing with MPS, and wiping with tissue daily can effectively reduce biofilm formation in contact lens cases.
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The purpose of this study was to investigate the prevalence of antiseptic-resistance (QAC) genes in staphylococci colonizing periorbital tissues and accessories of orthokeratology (ortho-k) lens wearers over a 6-month period and determine... more
The purpose of this study was to investigate the prevalence of antiseptic-resistance (QAC) genes in staphylococci colonizing periorbital tissues and accessories of orthokeratology (ortho-k) lens wearers over a 6-month period and determine the effect of their presence on minimum inhibitory (MIC) and bactericidal concentrations (MBC) of disinfectants and log reduction of multipurpose contact lens solutions (MPS). Staphylococci were isolated from periorbital tissues and accessories of patients before commencing ortho-k therapy and at two subsequent visits. Presence of QAC genes in 116 S. aureus and 67 CNS isolates was determined by PCR and association with period of ortho-k use determined. MICs and MBCs of staphylococci gene-positive were compared with gene-negative strains and the effectiveness of four MPS for rigid contact lenses investigated. S. aureus carriage rates in the conjunctiva decreased significantly from 41.2 % (baseline) to 11.8 % (3-months), and 13.3 % (6-months) (p trend 0.03), while CNS increased from 58.8 %(baseline) to 94.1 % (3-months), and 93.3 % (6-months) (p trend 0.02). Prevalence of qacA/B increased considerably over time (S. aureus: 4.4 % to 15.4 %, CNS: 6.7 % to 25 %), but frequency of smr was relatively stable. Only five CNS isolates harboured qacH. MICs and MBCs of gene-positive isolates were significantly increased and three MPS did not achieve a 3-log reduction of many QAC-positive strains. Ortho-k lens wear contributed to changes of staphylococcal carriage rates in the conjunctival sac. Use of MPS containing quaternary ammonium compounds may select for the carriage of organisms harbouring QAC genes, as the low concentration of disinfecting agents is not adequate for killing gene-positive strains.
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To investigate normal flora of children with and without orthokeratology (ortho-k) treatment, and the associations between carriage of Staphylococcus aureus and Gram-negative rods with contamination of contact lenses and lens cases in... more
To investigate normal flora of children with and without orthokeratology (ortho-k) treatment, and the associations between carriage of Staphylococcus aureus and Gram-negative rods with contamination of contact lenses and lens cases in ortho-k subjects and with spectacles of control subjects. Twenty-three ortho-k subjects (treatment >12 months) and 20 control myopic subjects aged 7-14 years were recruited. Samples were collected from four sites surrounding the left eye (lower conjunctiva, upper and lower eyelids, and eyelashes) for all subjects, spectacles for control subjects and contact lens accessories for ortho-k subjects. Samples were cultured, total numbers enumerated, and isolates identified using chromogenic agars. Ortho-k subjects had significantly less total isolates in the conjunctiva than controls (p = 0.009). Otherwise, carriage rates in normal flora levels of the peri-orbital tissues were not significantly different between the two groups (p > 0.19). The total iso...
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Many herbs are used in traditional Chinese medicine TCM) for treatment of infections but their properties, in particular, their effects on normal cells have received little attention. This study investigated the cytotoxic properties of... more
Many herbs are used in traditional Chinese medicine TCM) for treatment of infections but their properties, in particular, their effects on normal cells have received little attention. This study investigated the cytotoxic properties of three TCM herbs with potential use in prevention and treatment of ocular infections, including Acanthamoeba keratitis. The study investigated cytotoxic effects of the herbal extracts of Rhizoma coptidis, Radix scutellariae, and Cortex phellodendri on human corneal epithelial cells using trypan blue staining, MTT production, and flow cytometry. Differences between herbs were determined using repeated measures one-way analysis of variance, followed by paired t-tests where appropriate. These three herbs appeared to lack cytotoxicity when tested with trypan blue and MTT, but flow cytometry revealed that R. coptidis led to cell membrane damage. Lack of cytotoxicity of R. scutellariae and C. phellodendri extracts suggest that these are potentially suitable for use in ocular preparations. Only flow cytometry was able to accurately predict cytotoxic effects of extracts of TCM herbs on HCEC, demonstrating the importance of using a sensitive method of detection of cytotoxicity.
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... farmers Page 28. Co-authors and team members Mike Male, Abby Harper, Jennifer Kroeger (MS students) Erin Moritz-Korolev (PhD student) Loreen Herwaldt MD, Dan Diekema MD (UIHC) http://www.public-health.uiowa.edu/CEID/... more
... farmers Page 28. Co-authors and team members Mike Male, Abby Harper, Jennifer Kroeger (MS students) Erin Moritz-Korolev (PhD student) Loreen Herwaldt MD, Dan Diekema MD (UIHC) http://www.public-health.uiowa.edu/CEID/ tara-smith@uiowa.edu