Findings from the first public COVID-19 temporary test centre in Hong Kong.

INTRODUCTION: The Hospital Authority of Hong Kong Special Administrative Region established a coronavirus disease 2019 (COVID-19) temporary test centre at the AsiaWorld-Expo from March 2020 to April 2020, which allowed high-risk individuals to undergo early assessment of potential severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. This study reviewed the characteristics and outcomes of individuals who attended the centre for COVID-19 testing. METHODS: This retrospective cross-sectional study collected epidemiological and clinical data. The primary outcome was a positive or negative SARS-CoV-2 test result, according to reverse transcription polymerase chain reaction analyses of pooled nasopharyngeal and throat swabs collected at the centre. The relationships of clinical characteristics with SARS-CoV-2 positive test results were assessed by multivariable binary logistic regression. RESULTS: Of 1258 attendees included in the analysis, 86 individuals tested positive for SARS-CoV-2 infection (positivity rate=6.84%; 95% confidence interval [CI]=5.57%-8.37%). Of these 86 individuals, 40 (46.5%) were aged 15 to 24 years and 81 (94.2%) had a history of recent travel. Symptoms were reported by 86.0% and 96.3% of individuals with positive and negative test results, respectively. The clinical characteristics most strongly associated with a positive test result were anosmia (adjusted odds ratio [ORadj]=8.30; 95% CI=1.12-127.09) and fever ORadj=1.32; 95% CI=1.02-3.28). CONCLUSION: The temporary test centre successfully helped identify individuals with COVID-19 who exhibited mild disease symptoms. Healthcare providers should carefully consider the epidemiological and clinical characteristics of COVID-19 to arrange early testing to reduce community spread.

How are family doctors serving the Hong Kong community during the COVID-19 outbreak? A survey of HKCFP members.

INTRODUCTION: This study evaluated the preparedness of family doctors during the early phase of the coronavirus disease 2019 (COVID-19) outbreak in Hong Kong. METHODS: All members of the Hong Kong College of Family Physicians were invited to participate in a cross-sectional online survey using a 20-item questionnaire to collect information on practice preparedness for the COVID-19 outbreak through an email followed by a reminder SMS message between 31 January 2020 and 3 February 2020. RESULTS: Of 1589 family doctors invited, 491 (31%) participated in the survey, including 242 (49%) from private sector. In all, 98% surveyed doctors continued to provide clinical services during the survey period, but reduced clinic service demands were observed in 45% private practices and 24% public clinics. Almost all wore masks during consultation and washed hands between or before patient contact. Significantly more private than public doctors (80% vs 26%, P<0.001) experienced difficulties in stocking personal protective equipment (PPE); more public doctors used guidelines to manage suspected patients. The main concern of the respondents was PPE shortage. Respondents appealed for effective public health interventions including border control, quarantine measures, designated clinic setup, and public education. CONCLUSION: Family doctors from public and private sectors demonstrated preparedness to serve the community from the early phase of the COVID-19 outbreak with heightened infection control measures and use of guidelines. However, there is a need for support from local health authorities to secure PPE supply and institute public health interventions.

Use of the INNO-LIA syphilis score assay in the resolution of discordant positive screening enzyme immunoassay results for the serological diagnosis of syphilis.

We studied the use of the INNO-LIA syphilis score assay in the resolution of discordant positive screening results of the Murex ICE Syphilis enzyme immunoassay (EIA) with the confirmatory results of both the Serodia Treponema pallidum particle agglutination (TPPA) and the fluorescent treponemal antibody-absorption (FTA-Abs) assays, for the serological diagnosis of syphilis. This was an observational study on the serum samples received by the Syphilis Laboratory, Hong Kong, during the period from January 2006 to December 2012. A total of 801 serum samples with discordant positive screening EIA results were used. Consensus results of such serum samples were derived from results of the EIA, TPPA and FTA-abs assays. The age range of the individuals was 14 to 104 years (median of 52). There were 369 males and 432 females. Of 378 serum samples, 139 showed agreement among positive results, 23 of 310 showed agreement among indeterminate results and 277 of 465 showed agreement among negative results. The proportions of agreement among positive, indeterminate and negative results were 0.37 (95% CI 0.32-0.42), 0.07 (95% CI 0.05-0.11) and 0.60 (95% CI 0.55-0.64), respectively; kappa 0.55 (95% CI 0.49-0.60). There were 60 serum samples with positive consensus results but negative INNO-LIA syphilis score results and 10 with negative consensus results but positive INNO-LIA syphilis score results. Although the INNO-LIA syphilis score assay can be considered a valid alternative confirmatory test for the serological diagnosis of syphilis, the present study showed that its use in the resolution of discordant positive screening EIA results was moderate. A more extensive characterization of serum samples with discordant reactive screening treponemal test results is necessary.

Comparative evaluation of the INNO-LIA syphilis score and the MarDx Treponema pallidum immunoglobulin G Marblot test assays for the serological diagnosis of syphilis.

We evaluated the performance of two immunoblot assays: the INNO-LIA Syphilis Score (LIA) and the MarDx T. pallidum IgG Marblot Test (TWB), as compared with that of the Murex ICE Syphilis enzyme immunoassay (EIA), the Serodia Treponema pallidum particle agglutination (TPPA) assay and the fluorescent treponemal antibody-absorption (FTA-abs) assay, for the serological diagnosis of syphilis using serum samples of 135 attendees of the social hygiene clinics of the Department of Health in Hong Kong newly diagnosed with syphilis and provided with clinical stages (39 in primary, 20 in secondary, 18 in early latent and 58 in latent of unknown duration) and of 43 normal healthy subjects between October and December 2004. The differences in the overall sensitivities of the LIA assay and the EIA/TPPA/FTA-abs assays were not statistically significant (P > 0.05) whereas the overall sensitivity of the TWB assay was significantly lower (P < 0.05) than the overall sensitivities of the EIA, the TPPA and the FTA-abs assays. The LIA assay had an overall sensitivity of 94.1% (95% CI 88.7-97.0%) whereas the TWB assay 65.2% (95% CI 56.8-72.7%). Both the LIA and the TWB assays have a specificity of 100%. When consensus results were derived from the most predominant results of the EIA, the TPPA and the FTA-abs assays, the LIA assay had a positive agreement with the consensus results of 98.5% (95% CI 94.5-99.6%) whereas the TWB assay 68.2% (95% CI 59.8-75.6%). Therefore, the LIA assay performed significantly better (P < 0.05) than the TWB assay. The LIA assay can be considered to be a valid alternative confirmatory test for the serological diagnosis of syphilis.

Maturational changes in peripheral lymphocyte subsets pertinent to monitoring human immunodeficiency virus-infected Chinese pediatric patients.

On the basis of results of testing of 212 peripheral blood samples from ethnic Chinese individuals in five age groups, ranging from birth to adulthood, by standardized flow cytometry techniques, we studied the maturational processes that are pertinent to monitoring the human immunodeficiency virus (HIV)-infected Chinese pediatric population. While the numbers of peripheral total white cells and percent lymphocytes declined from birth to adulthood, the percent CD3+ T lymphocytes was steady among all age groups studied. The numbers of CD3+ CD4+ (T-helper) cells decreased markedly after the first year of life, followed by a slower decline afterward and then a slight increase before adulthood. The trend for CD3+ CD8+(T-suppressor) cells, however, was an increase among individuals of all age ranges. The numbers of CD19+ CD3- (B cells) increased only during the first year of life and then declined steadily, while natural killer (NK) cells showed the opposite pattern. Comparison of the results with those of studies done with a Caucasian population showed that both peripheral T-helper and T-suppressor cell numbers were low after the first year of life in the Chinese pediatric population in comparison with those in a Caucasian pediatric population. Lower B-cell counts and higher NK-cell counts were seen after the first year of life in the Chinese population than in the Caucasian population. It is important that for each HIV-infected population normative ranges of the lymphocyte subset be established to monitor HIV-infected pediatric patients.

Proposed CD4(+) T-cell criteria for staging human immunodeficiency virus-infected Chinese adults.

The present treatment, prophylaxis, and prognostic staging of human immunodeficiency virus (HIV) disease rely heavily on peripheral CD4(+) T lymphocyte (CD4) changes. We correlated the clinical course of events and CD4 changes among consecutive HIV-infected ethnic Chinese adults in Hong Kong. Using death as end point, the estimated proportion survival and death incidences were used to compare CDC and proposed staging criteria based on stratified baseline CD4. A separate set of baseline CD4 per microliter (/microl) (percentage lymphocytes) stratification criteria of 1, >220/microl (>12%); 2, 100-220/microl (6-12%); and 3, <100/microl, (<6%) is proposed which can be used for staging HIV-infected Chinese adults. For our study population, our proposed criteria for stratifying baseline CD4 gave better discrimination and more predictive power than the CDC criteria. We assessed the potential impact of these new proposed criteria on anti-retroviral treatment and prophylaxis against opportunistic infections in our adult HIV-infected population.

Lymphocyte subpopulation reference ranges for monitoring human immunodeficiency virus-infected Chinese adults.

Two hundred eight healthy human immunodeficiency virus (HIV) type 1- and HIV type 2-seronegative Chinese adults (78 males and 130 females; mean age, 32 years; age range, 18 to 71 years) were analyzed for lymphocyte subsets by a standardized and quality-controlled flow cytometric immunophenotyping technique. While the leukocyte differential values were comparable to those found in studies of Caucasians, the means, medians, and 95% reference ranges of lymphocyte subsets were very different. The 95% reference ranges in absolute counts per microliter of whole blood (percentage of lymphocytes) for CD3+, CD3+ CD4+, CD3+ CD8+, CD3- CD19+ (B), and CD3- with CD16+ and/or CD56+ (NK) cells were 672 to 2,368 (54.8 to 83.0%), 292 to 1,366 (23.1 to 51.0%), 240 to 1,028 (17.9 to 47.5%), 82 to 560 (5.1 to 20.8%), and 130 to 938 (7.1 to 38.0%), respectively. CD3+ CD4+ cells showed significant sex difference (for males, mean of 702 [34.8%] and standard deviation of 258 [7.5%]; for females, mean of 728 [37.3%] and standard deviation of 254 [7.4%]) as well as an increase with age of 42 (1.6%) per decade. Investigations of the NK cell population did not show similar findings. Classification of HIV disease, treatment, and prophylactic regimens based on studies which relied heavily on estimations of lymphocyte subsets alone should be used with special caution for Chinese patients. Provided that adequate quality control measures are taken to ensure comparability of data, we recommend that these ranges be used on a day-to-day basis in laboratories that have not yet established their own reference ranges.

Streptococcus mutans dextransucrase: effect of cerulenin on lipid synthesis and enzyme production.

The effect of the fatty acid synthesis inhibitor cerulenin on growth and dextransucrase (EC 2.4.1.5) production by Streptococcus mutans 6715 was analyzed. Growth was markedly inhibited by less than 1 microgram of the antibiotic per ml. Under conditions where cerulenin did not inhibit amino acid incorporation into protein but did block acetate metabolism into lipid, the production of extracellular dextransucrase was suppressed. Inhibition was not due to a direct effect of the antibiotic on the enzyme or the lack of release of enzyme from the bacterial cell surface. Gel column chromatography demonstrated that enzyme produced in the presence of cerulenin was highly aggregated, similar to the control enzyme. Although the addition of ysophosphatidylcholine to enzyme which had been synthesized in the presence of cerulenin stimulated glucan formation from sucrose, the increase was not greater than that produced with the control enzyme. The differential inhibition of dextransucrase production by cerulenin indicates that enzyme secretion requires the production of lipid and may reflect the mechanism by whch this enzyme is transported from the bacterial cell.

Mannose-contaminating agglutinin for Actinomyces viscosus and Actinomyces naeslundii.

Rapid agglutination of Actinomyces viscosus and Actinomyces naeslundii cells by D-mannose solutions was observed during studies of their attachment to mammalian cells in vitro. The specificity of the agglutination reaction was studied by slide agglutination tests and by measuring the rate of decrease in optical density of bacterial phosphate buffer suspensions caused by the setting of bacterial aggregates. Actinomyces cells were agglutinated by protein-containing mannose solutions of several chemical suppliers. Solutions of sugars other than D-mannose and solutions of mannitol and mannan all failed to agglutinate A. viscsus and A. naeslundii. "Mannose-enhanced" agglutination was impaired by boiling or autoclaving the mannose but was not affected by heating the bacteria, the presence of chloramphenicol, running the assay in the cold, or incorporating any of several commercially purchased sugars in the reaction mixture. During these hapten inhibition experiments, only 6-deoxy-L-talcose-containing extracts of an A. viscosus strain retarded the rate of mannose-enhanced agglutination. Protein-containing fractions of D-mannose mother liquors also agglutinated cells of A. viscosus and A. naeslundii. Other species of oral gram-positive rods were not agglutinated by mannose solutions. Together the data indicate that plant seed-derived D-mannose contains a protein-associated agglutinin for A. viscosus and A. naeslundii which may function via a "lectin-like" selective affinity for the unique cell wall sugar 6-deoxy-L-talose.

Streptococcus mutans dextransucrase: functioning of primer dextran and endogenous dextranase in water-soluble and water-insoluble glucan synthesis.

The extracellular enzyme activities of Streptococcus mutans 6715 that synthesize glucans from sucrose were concentrated and partially purified by ammonium sulfate precipitation and gel permeation column chromatography. Polyacrylamide gel analysis demonstrated that all of the major proteins precipitated by ammonium sulfate were quantitatively recovered in the high-molecular-weight, enzyme-containing aggregates found in the void volume of the gel column. Anion-exchange column chromatography was used to fractionate the aggregates into preparations, alpha and beta, which produced water-insoluble and water-soluble glucans, respectively. Polyacrylamide gel analysis showed that alpha and beta contained unique proteins and dextransucrase (EC 2.4.1.5) activities. Studies on the time course of glucan synthesis by alpha demonstrated that this enzyme preparation contained dextranase activity, which partially degraded nascent alcohol-insoluble glucan into alcohol-soluble products that were subsequently reincorporated into insoluble product. The beta enzyme preparation contained no detectable dextranase activity. Mixing experiments in the absence of primer dextran demonstrated that the dextranase activity present in alpha could modify glucan production by beta. CsCl density gradient analysis of product glucans demonstrated that exogenous primer dextrans were used as acceptor molecules by both the alpha and beta enzyme preparations, and that water-soluble glucans synthesized by beta could be converted into water-insoluble glucans by alpha. It is proposed that the structural heterogeneity of the native glucans produced from sucrose by S. mutans is a result of the concerted action of glucan-forming dextransucrases and endohydrolytic dextranase activity.

Effect of sugar analogues on growth, sugar utilization, and acid production by Streptococcus mutans.

Studies on the effect of various structural analogues of glucose of phosphoenolpyruvate (PEP)-dependent sugar transport in Streptococcus mutans showed that sugars with alterations at carbon 2 were markedly inhibitory. Low concentrations of the nonfermentable analogue D-2-deoxyglucose (2-deoxyg) blocked the growth of S mutans in broth media containing various fermentable sugars. Acid production by S mutans from both exogenous glucose and intracellular storage polysaccharide was inhibited by 2-deoxyG. The analogue is bacteriostatic, and large quantities of intracellular 2-deoxyG-6-PO4 accumulate during exposure of S mutans to the sugar.