PY Woh | The Hong Kong Polytechnic University (original) (raw)

Publications by PY Woh

The quantitative buffy coat (QBC) technique and conventional Giemsa thin blood smear was compared... more The quantitative buffy coat (QBC) technique and conventional Giemsa thin blood smear was compared to determine the sensitivity and specificity of the technique in detecting blood parasitic infection of the rodent populations from four urban cities in Peninsular Malaysia. A total of 432 blood samples from four rat species (Rattus norvegicus, Rattus rattus diardii, Rattus exulans and Rattus argentiventer) were screened using both techniques and successfully detected two blood protozoan species (Trypanosoma lewisi and Plasmodium sp.) with Trypanosoma lewisi predominantly infecting the population. Results showed that Giemsa-stained thin film (GTF) was the better detection method on blood parasitemia (46.7%) compared to Quantitative Buffy Coat method (38.9%) with overall detection technique sensitivity and specificity at 83.2% and 74.8% respectively. The sensitivity in detection of Trypanosoma lewisi was 84.4% with value slightly lower for Plasmodium sp. infections at 76.6%. Statistical ...

Microbiol Spectr, 2021

Nontyphoidal Salmonella (NTS) gastroenteritis in children remains a significant burden on health... more Nontyphoidal Salmonella (NTS) gastroenteritis in children remains a significant burden on health care and constitutes a majority of all admissions for Salmonella infections in public hospitals in Hong Kong. In this prospective study, 41% of 241 children hospitalized with gastroenteritis from three public hospitals during 2019 were culture confirmed to have NTS infection. These Salmonella isolates were whole-genome sequenced and in silico predicted for their serovars/serotypes using the Salmonella In Silico Typing Resource (SISTR) and SeqSero1, and the antimicrobial resistance (AMR) genes were determined. Phylogenetic analysis revealed three major clades belonging to Salmonella enterica serovar Enteritidis sequence type 11 (ST11) (43%), multidrug-resistant (MDR) S. Typhimurium ST19 (12%) and its monophasic variant ST34 (25%), and mostly singletons of 15 other serovars. MDR S. Typhimurium and its variant were more common in infants ,24 months of age and possessed genotypic resistance to five antimicrobial agents, including ampicillin (A), chloramphenicol (C), aminoglycosides (Am), sulfonamides (Su), and tetracyclines (T). Older children were more often infected with S. Enteritidis, which possessed distinct genotypic resistance to AAmSu and fluoroquinolones. In addition, 3% of the isolates possessed extended-spectrum beta-lactamase (ESBL) CTX-M genes, while one isolate (1%) harboring the carbapenemase gene blaNDM-1 was identified. Our findings provide a more complete genomic epidemiological insight into NTS causing gastroenteritis and identify a wider spectrum of determinants of resistance to third-generation beta-lactams and carbapenems, which are often not readily recognized. With high rates of multidrug-resistant NTS from studies in the Asia-Pacific region, the rapid and reliable determination of serovars and resistance determinants using whole-genome sequencing (WGS) is invaluable for enhancing public health interventions for infection prevention and control.

BMJ Paediatrics Open, 2021

Objective: To explore risk factors associated with nontyphoidal Salmonella gastroenteritis in you... more Objective: To explore risk factors associated with nontyphoidal Salmonella gastroenteritis in young children in Hong Kong.
Design: A case–control study.
Setting: Paediatrics wards at three public hospitals in Hong Kong.
Participants: Cases were children aged above 30 days to below 5 years hospitalised for gastroenteritis at three public hospitals in Hong Kong with culture confirmed nontyphoidal Salmonella infection. Controls were age-matched (±2 months) children admitted for a reason other than gastroenteritis.
Main outcomes measures: A face-to-face interview by using standardised questionnaire on exposures 3 days prior to illness. Adjusted OR (aORs) and 95% CIs were calculated using multivariable logistic regression.
Results: A total of 102 cases and 204 age-matched controls were included in the analysis. Multivariable logistic regression revealed that having food purchased from places other than a supermarket, that is, from wet market/restaurant/farm (aOR, 2.64; 95% CI, 1.03 to 6.77; p=0.044) was a significant risk factor for non-typhoidal Salmonella infection. Having a household member with gastroenteritis symptoms (aOR, 2.03; 95%CI, 0.94 to 4.39; p=0.072) was of borderline significance and playing at a children’s indoor playroom was a protective factor (aOR, 0.28; 95%CI, 0.09 to 0.85; p=0.024).
Conclusions: Consumption of food purchased from places other than a supermarket was the identified determinant factor for non-typhoidal Salmonella gastroenteritis in Hong Kong. Parents/caregivers should be alerted to this risk when choosing foods for their young children. The protective effect of playing in an indoor playroom could be confounded by socioeconomic factors and further investigation is required to better understand its potential implication. There was some support for person-to-person transmission and good family hygiene needs to be emphasised.

This study used microbial indicators to assess the hygiene status of 383 migrant food handlers fr... more This study used microbial indicators to assess the hygiene status of 383 migrant food handlers from 3 urban cities in Peninsular Malaysia. Microbiological analysis revealed that all the hand swabs tested 99.5% positive for aerobic plate counts (mean [M] ± standard deviation [SD] = 3.57 ± 0.83 log 10 CFU [colony forming unit]), 20.8% positive for total coliform/Escherichia coli (M ± SD = 0.30 ± 0.67 log 10 CFU), and 63.4% positive for Staphylococcus aureus (M ± SD = 1.38 ± 1.26 log 10 CFU). In addition, aerobic plate counts and Staphylococcus aureus counts exceeded the acceptable standard levels. Bacterial counts were found to be significantly associated with subjects' country of origin (P = .019) and working responsibilities (P = .001). Our findings indicate high probability of transmission of pathogenic bacteria from the food handlers' hands to customers during meal preparation and serving. This calls for improvements in personal hygiene and sanitation standards by the relevant health authorities among migrant food handlers.

Asymptomatic Salmonella carriers who work as food handlers pose food safety and public health ris... more Asymptomatic Salmonella carriers who work as food handlers pose food safety and public health risks, particularly during food preparation, and this has serious implications for the disease burden in society. Therefore, we conducted a study to determine the number of Salmonella carriers in a migrant cohort in several food establishments in three major cities in Peninsular Malaysia. Sociodemographic data and stool samples were collected and analyzed using standard methods of detection and isolation. Antimicrobial susceptibility tests of the positive samples were also performed. A total of 317 migrant food handlers, originating from South and Southeast Asian countries, were recruited voluntarily. Nine (2.8%) stool samples were confirmed to be Salmonella positive. PCR serotyping and pulsed-field gel electrophoresis identified four serotypes as Typhimurium (n ¼ 3), Corvallis (n ¼ 2), Hadar (n ¼ 1), Agona (n ¼ 1) and two unknown serovars. Antimicrobial susceptibility tests revealed that all nine isolates were susceptible to amoxicillin–clavulanic acid, cefotaxime, ceftazidime, ceftriaxone, and gentamycin. However, seven isolates were found to be multidrug resistant to ampicillin, chloramphenicol, trimethoprim-sulfamethoxazole, sulfonamides, streptomycin, and tetracycline. This study highlights that carriers of nontyphoidal Salmonella exist among migrant food handlers, which poses a health risk to consumers through food contamination. Our results indicate a need for authorities to enhance food safety awareness in the migrant workers and to reevaluate current health screening methods to include preventive measure such as mandatory stool screening as part of the preemployment and routine health examinations.

Blastocystis infection is widely reported in wildlife, livestocks and in non-human primates howev... more Blastocystis infection is widely reported in wildlife, livestocks and in non-human primates however, occurrence in Malaysian wildlife is scarce. A wildlife survey on Tioman Island captured six water monitor lizard (Varanus salvator), four mouse-deer (Tragulus sp.) and one Malayan porcupine (Hystrix brachyura) based on convenience sampling. Intestinal contents from each animal were subjected to in vitro cultivation method using Jones medium supplemented with 10% horse serum. Low prevalence of infections was detected with only 1/6 (16.7%) water monitor lizard and 1/4 (25%) mouse-deer infected. The vacuolated form was the most common cell form found in both cultures with similar morphology to B. hominis. However, the monitor lizard isolate propagated well in the laboratory for several months using Jones medium while mouse-deer isolate could not be maintained for more than a week. The reptilian isolates grew optimally at a lower temperature of 24ºC compared to 37ºC for the mouse-deer isolate. Using the DNA barcoding method, both isolates were confirmed to be Blastocystis sp. Sequence obtained from a monitor lizard isolate has 94% sequence identity to B. lapemi, an isolate recovered from a reptile sea-snake whereas a mouse-deer isolate has 99% sequence identitical to B. hominis HJ01-7. The phylogenetic tree revealed that the monitor lizard isolate were positioned within the herptiles clade (clade VIII) while the mouse deer isolate located at the homoithermal clade (clade IV). The present paper is the first report on the presence as well as genetic characteristics of Blastocystis in wildlife captured from Tioman Island, Pahang.

This study was aimed to measure the basic knowledge on food safety and food handling practices am... more This study was aimed to measure the basic knowledge on food safety and food handling practices among
migrant food handlers as these information is scarce in Malaysia. A cross-sectional study was conducted
face-to-face amongst 383 migrant food handlers from three major cities in Peninsular Malaysia through
questionnaire. Socio-demographic information of all respondents was collected. Questions on food safety
knowledge (i.e. food cleanliness and hygiene, symptom of foodborne illnesses and foodborne pathogens)
and food handling practices were assessed. The compiled data were analyzed by using the Statistical
Packages for Social Science (SPSS) 16.0. Overall, migrant food handlers had poor level of knowledge on
food safety with an average food handling practice. Significant effects were observed between respondents’
food safety knowledge and socio-demography (country of origin and educational level) and
two factors namely; respondents’ nationality and attendance at food training programs showed significant
associations with their food handling practices. Multiple logistic regression analyses revealed that
attendance at food training programs was a significant and independent predictor of the respondent’s
food handling practice. The study’s findings highlighted issues with regards to the extent of knowledge
acquisition on food safety and hygiene by migrant food handlers. Therefore, this warrants improvements
not only in the better delivery methods of training modules but also tight enforcement of attendance at
the programs by the respective authorities.

This study was aimed to measure the basic knowledge on food safety and food handling practices am... more This study was aimed to measure the basic knowledge on food safety and food handling practices among migrant food handlers as these information is scarce in Malaysia. A cross-sectional study was conducted face-to-face amongst 383 migrant food handlers from three major cities in Peninsular Malaysia through questionnaire. Socio-demographic information of all respondents was collected. Questions on food safety knowledge (i.e. food cleanliness and hygiene, symptom of foodborne illnesses and foodborne pathogens) and food handling practices were assessed. The compiled data were analyzed by using the Statistical Packages for Social Science (SPSS) 16.0. Overall, migrant food handlers had poor level of knowledge on food safety with an average food handling practice. Significant effects were observed between re-spondents' food safety knowledge and socio-demography (country of origin and educational level) and two factors namely; respondents' nationality and attendance at food training programs showed significant associations with their food handling practices. Multiple logistic regression analyses revealed that attendance at food training programs was a significant and independent predictor of the respondent's food handling practice. The study's findings highlighted issues with regards to the extent of knowledge acquisition on food safety and hygiene by migrant food handlers. Therefore, this warrants improvements not only in the better delivery methods of training modules but also tight enforcement of attendance at the programs by the respective authorities.

The quantitative buffy coat (QBC) technique and conventional Giemsa thin blood smear was compared... more The quantitative buffy coat (QBC) technique and conventional Giemsa thin blood
smear was compared to determine the sensitivity and specificity of the technique in detecting
blood parasitic infection of the rodent populations from four urban cities in Peninsular Malaysia.
A total of 432 blood samples from four rat species (Rattus norvegicus, Rattus rattus diardii,
Rattus exulans and Rattus argentiventer) were screened using both techniques and
successfully detected two blood protozoan species (Trypanosoma lewisi and Plasmodium
sp.) with Trypanosoma lewisi predominantly infecting the population. Results showed that
Giemsa-stained thin film (GTF) was the better detection method on blood parasitemia (46.7%)
compared to Quantitative Buffy Coat method (38.9%) with overall detection technique
sensitivity and specificity at 83.2% and 74.8% respectively. The sensitivity in detection of
Trypanosoma lewisi was 84.4% with value slightly lower for Plasmodium sp. infections at
76.6%. Statistical analysis proved that GTF technique was significantly more sensitive in the
detection of blood protozoan infections in the rodent population compared to QBC (p<0.05).

Leptospira species were studied in water and soils from selected urban sites in Malaysia. A total... more Leptospira species were studied in water and soils from selected urban sites in Malaysia. A total of 151 water (n=121) and soil (n=30) samples were collected from 12 recreational lakes and wet markets. All samples were filtered and inoculated into semi-solid Ellinghausen and McCullough modified by Johnson and Harris (EMJH) media supplemented with additional 5-fluorouracil. The cultures were then incubated at 30°C and observed under a dark field microscope with intervals of 10 days. A PCR assay targeting the rrs gene was used to confirm the genus Leptospira among the isolates. Subsequently, the pathogenic status of the isolates was determined using primer sets G1/G2 and Sapro1/Sapro2, which target the secY and rrs genes, respectively. The isolates were identified at serogroup level using the microscopic agglutination test (MAT) while their genetic diversity was assessed by pulsed field gel electrophoresis (PFGE). Based on dark field microscopy, 23.1% (28/121) water and 23.3% (7/30) soil cultures were positive for Leptospira spp. Of the 35 positive cultures, only 8 were pure and confirmed as Leptospira genus by PCR assay. Two out of 8 isolates were confirmed as pathogenic, 5 were saprophytic and one was intermediate. These 8 isolates were negative for the 25 reference hyperimmune rabbit sera tested in the MAT. PFGE showed that all 8 of these environmental Leptospira spp. were genetically diverse. In conclusion, the presence of pathogenic Leptospira spp. in the urban Malaysian environment may indicate and highlight the importance of water screening, especially in recreational lakes, in order to minimize any chance of Leptospira infection.

The quantitative buffy coat (QBC) technique and conventional Giemsa thin blood smear was compare... more The quantitative buffy coat (QBC) technique and conventional Giemsa thin blood
smear was compared to determine the sensitivity and specificity of the technique in detecting
blood parasitic infection of the rodent populations from four urban cities in Peninsular Malaysia.
A total of 432 blood samples from four rat species (Rattus norvegicus, Rattus rattus diardii,
Rattus exulans and Rattus argentiventer) were screened using both techniques and
successfully detected two blood protozoan species (Trypanosoma lewisi and Plasmodium
sp.) with Trypanosoma lewisi predominantly infecting the population. Results showed that
Giemsa-stained thin film (GTF) was the better detection method on blood parasitemia (46.7%)
compared to Quantitative Buffy Coat method (38.9%) with overall detection technique
sensitivity and specificity at 83.2% and 74.8% respectively. The sensitivity in detection of
Trypanosoma lewisi was 84.4% with value slightly lower for Plasmodium sp. infections at
76.6%. Statistical analysis proved that GTF technique was significantly more sensitive in the
detection of blood protozoan infections in the rodent population compared to QBC (p<0.05).

Leptospira species were studied in water and soils from selected urban sites in Malaysia. A total... more Leptospira species were studied in water and soils from selected urban sites in Malaysia. A total of 151 water
(n=121) and soil (n=30) samples were collected from 12 recreational lakes and wet markets. All samples were filtered
and inoculated into semi-solid Ellinghausen and McCullough modified by Johnson and Harris (EMJH) media
supplemented with additional 5-fluorouracil. The cultures were then incubated at 30°C and observed under a dark field
microscope with intervals of 10 days. A PCR assay targeting the rrs gene was used to confirm the genus Leptospira
among the isolates. Subsequently, the pathogenic status of the isolates was determined using primer sets G1/G2 and
Sapro1/Sapro2, which target the secY and rrs genes, respectively. The isolates were identified at serogroup level using
the microscopic agglutination test (MAT) while their genetic diversity was assessed by pulsed field gel electrophoresis
(PFGE). Based on dark field microscopy, 23.1% (28/121) water and 23.3% (7/30) soil cultures were positive for
Leptospira spp. Of the 35 positive cultures, only 8 were pure and confirmed as Leptospira genus by PCR assay. Two
out of 8 isolates were confirmed as pathogenic, 5 were saprophytic and one was intermediate. These 8 isolates were
negative for the 25 reference hyperimmune rabbit sera tested in the MAT. PFGE showed that all 8 of these environmental
Leptospira spp. were genetically diverse. In conclusion, the presence of pathogenic Leptospira spp. in the urban
Malaysian environment may indicate and highlight the importance of water screening, especially in recreational lakes,
in order to minimize any chance of Leptospira infection.

Microbiol Spectr, 2021

BMJ Paediatrics Open, 2021

This study was aimed to measure the basic knowledge on food safety and food handling practices am... more This study was aimed to measure the basic knowledge on food safety and food handling practices among migrant food handlers as these information is scarce in Malaysia. A cross-sectional study was conducted face-to-face amongst 383 migrant food handlers from three major cities in Peninsular Malaysia through questionnaire. Socio-demographic information of all respondents was collected. Questions on food safety knowledge (i.e. food cleanliness and hygiene, symptom of foodborne illnesses and foodborne pathogens) and food handling practices were assessed. The compiled data were analyzed by using the Statistical Packages for Social Science (SPSS) 16.0. Overall, migrant food handlers had poor level of knowledge on food safety with an average food handling practice. Significant effects were observed between re-spondents' food safety knowledge and socio-demography (country of origin and educational level) and two factors namely; respondents' nationality and attendance at food training programs showed significant associations with their food handling practices. Multiple logistic regression analyses revealed that attendance at food training programs was a significant and independent predictor of the respondent's food handling practice. The study's findings highlighted issues with regards to the extent of knowledge acquisition on food safety and hygiene by migrant food handlers. Therefore, this warrants improvements not only in the better delivery methods of training modules but also tight enforcement of attendance at the programs by the respective authorities.

The quantitative buffy coat (QBC) technique and conventional Giemsa thin blood smear was compared... more The quantitative buffy coat (QBC) technique and conventional Giemsa thin blood
smear was compared to determine the sensitivity and specificity of the technique in detecting
blood parasitic infection of the rodent populations from four urban cities in Peninsular Malaysia.
A total of 432 blood samples from four rat species (Rattus norvegicus, Rattus rattus diardii,
Rattus exulans and Rattus argentiventer) were screened using both techniques and
successfully detected two blood protozoan species (Trypanosoma lewisi and Plasmodium
sp.) with Trypanosoma lewisi predominantly infecting the population. Results showed that
Giemsa-stained thin film (GTF) was the better detection method on blood parasitemia (46.7%)
compared to Quantitative Buffy Coat method (38.9%) with overall detection technique
sensitivity and specificity at 83.2% and 74.8% respectively. The sensitivity in detection of
Trypanosoma lewisi was 84.4% with value slightly lower for Plasmodium sp. infections at
76.6%. Statistical analysis proved that GTF technique was significantly more sensitive in the
detection of blood protozoan infections in the rodent population compared to QBC (p<0.05).

Leptospira species were studied in water and soils from selected urban sites in Malaysia. A total... more Leptospira species were studied in water and soils from selected urban sites in Malaysia. A total of 151 water
(n=121) and soil (n=30) samples were collected from 12 recreational lakes and wet markets. All samples were filtered
and inoculated into semi-solid Ellinghausen and McCullough modified by Johnson and Harris (EMJH) media
supplemented with additional 5-fluorouracil. The cultures were then incubated at 30°C and observed under a dark field
microscope with intervals of 10 days. A PCR assay targeting the rrs gene was used to confirm the genus Leptospira
among the isolates. Subsequently, the pathogenic status of the isolates was determined using primer sets G1/G2 and
Sapro1/Sapro2, which target the secY and rrs genes, respectively. The isolates were identified at serogroup level using
the microscopic agglutination test (MAT) while their genetic diversity was assessed by pulsed field gel electrophoresis
(PFGE). Based on dark field microscopy, 23.1% (28/121) water and 23.3% (7/30) soil cultures were positive for
Leptospira spp. Of the 35 positive cultures, only 8 were pure and confirmed as Leptospira genus by PCR assay. Two
out of 8 isolates were confirmed as pathogenic, 5 were saprophytic and one was intermediate. These 8 isolates were
negative for the 25 reference hyperimmune rabbit sera tested in the MAT. PFGE showed that all 8 of these environmental
Leptospira spp. were genetically diverse. In conclusion, the presence of pathogenic Leptospira spp. in the urban
Malaysian environment may indicate and highlight the importance of water screening, especially in recreational lakes,
in order to minimize any chance of Leptospira infection.