Molecular characterization of Staphylococcus aureus ST6 and ST7 isolates from food-borne illness outbreaks / 中华预防医学杂志

Objective: To analyze the Staphylococcal enterotoxins, Staphylococcal enterotoxin genes, drug resistance and molecular typing of 41 Staphylococcus aureus isolates from 2 food-borne illness outbreaks on 21 August and 27 September 2020 in Guangzhou. Methods: A total of 41 Staphylococcus aureus isolates from 2 outbreaks were analyzed by multilocus sequence typing (MLST) and spa typing. The Staphylococcal enterotoxins typing and the Staphylococcal enterotoxin genes of the isolates were analyzed by ELISA and PCR, respectively. The antimicrobial susceptibility of the isolates was performed by disc diffusion. 21 Staphylococcus aureus isolates were characterized using whole genome sequencing (WGS). Based on the whole genome single nucleotide polymorphism (SNP), the phylogenetic tree was constructed by Snippy. Results: 41 Staphylococcus aureus isolates were divided into 2 types by MLST and spa typing: ST6-t701 and ST7-t091. 2 ST7-t091 isolates were identified as methicillin-resistant Staphylococcus aureus (MRSA). 25 ST7-t091 isolates and 14 ST6-t701 isolates were methicillin-sensitive Staphylococcus aureus (MSSA), and were resistant to 7 and 6 antibiotics, respectively. All isolates were positive for sea by PCR. WGS revealed all 21 isolates carried scn, sak, sea, hla, hld, hlgA, hlgB, hlgC, lukD virulence genes. The results showed the isolates contained an immune evasion cluster type D which located in bacteriophage ϕSa3. The SNP phylogenetic tree showed 2 MRSA ST7-t091 were constituted a separate clade from the 12 MSSA ST7-t091 isolates and 7 ST6-t701 isolates showed high similarity to each other. Conclusion: Base on the results of phylogenetic analysis, the 2 food-borne illness outbreaks occurred on 21 August and 27 September 2020 are caused by the combination of the MRSA ST7-t091 strain and the MSSA ST7-t091 strain, and the MSSA ST6-t701 strain, respectively. All isolates have high level of antibiotic resistance and carry high virulent genes.

The molecular epidemiology characteristics of norovirus in environment and clinical samples in Guangzhou from 2009 to 2011 / 中华预防医学杂志

<p><b>OBJECTIVE</b>To investigate the molecular epidemiological characteristics of norovirus in Guangzhou from 2009 to 2011.</p><p><b>METHODS</b>A total of 183 water samples, 1162 seafood samples and 1066 diarrhea stool specimens were collected from January 2010 to May 2011, June 2009 to June 2011 and July 2009 to December 2010 respectively in Guangzhou. Norovirus was detected by real time reverse transcript-PCR (qRT-PCR). The partial polymerase gene was amplified from norovirus positive samples, then sequenced and compared with the sequences of norovirus in GenBank. The phylogenetic tree was created.</p><p><b>RESULTS</b>The positive rate was 19.67% (36/183), 8.26% (96/1162) and 37.05% (395/1066) in water samples, seafood and diarrhea patients respectively. Noroviruses from positive samples could be divided into 10 representative strains, in which 7 representative strains of genotype of 208 samples was type G2-4. The sequences from water, seafood and stool specimens were highly homologous with the similarity of 94% - 100%.</p><p><b>CONCLUSION</b>In Guangzhou, the predominant Norovirus genotype was G2-4 and the positive rate of samples was high.</p>

Study on the inhibitory effect of RNA interference on replication of dengue virus / 病毒学报

To investigate the inhibitory effect of RNA interference (RNAi) on dengue virus I (DENV-1) replication. Small interfering RNA (siRNA) against the PreM gene of dengue virus was synthesized and transfected into C6/36 cells with liposome, which was then attacked by DENV-1 virus. The antiviral effect of siRNA was evaluated by cytopathic effect (CPE), the cell survival rate measured by MTT, and virus RNA quantified by real-time RT-PCR. The results showed that after 7 days post infection of dengue virus, the transfected C6/36 cells showed less CPE. The cell survival rate of the transfected C6/36 cells increased by 2.26 fold, and the amount of virus RNA in the transfected cells was reduced by about 97.54% as well. These findings indicated that the siRNA could effectively inhibit dengue virus RNA replication, and protect C6/36 cells from viral attack, indicating its potential role in prevention and treatment of dengue fever.

Epidemiological characteristic of first case of locally identified A/H1N1 secondary cases caused by imported source of infection in China / 中华流行病学杂志

Objective To study the first locally identifcd A/HINI secondary cases outbreak in China. Methods Interview and field investigation were integrated to describe the whole process of transmission on each case and to illustrate the relationships between the onset of the disease and the retated factors. Results Two contact persons appearanced fever and whose throat swabs were tested positive to H1N1 viral nucleic acid. The two had a history of contact in a short distance with the initial imported case without any protective measure in the poor air ventilation. The patients clinical situation was slight. The incubation was between 37 hours and 57 hours. No other new case was found after intervention as isolation and antisepsis were taken. Conclusion This event was proved to be an outbreak of local A/H1N1 secondary cases caused by the imported case. The main mode of transmission was personal contact in a short distance without protection, through air and droplet. The locus with poor air ventilation was high risk place. Contact persons should be observed seven days and tested continuously.Infectivity and pathogenicity of the A/H1N1 virus were limited and appeared weakened by generations. Patient's condition was related with persistence and frequency of contact with the infection sources. Enhancing management of contact persons, health education, early diagnose, early treatment and early insulation were effective measures of controling and prenventing the spread A/H1N1.

Relation between clinical detection rates of the novel influenza virus A/H1N1 RNA in confirmed patients in Guangzhou and the disease course / 南方医科大学学报

<p><b>OBJECTIVE</b>To study the relation of the detection rates of the novel influenza virus A/H1N1 RNA in clinically confirmed patients in the 2009 pandemic with the age distribution of the patients and the disease course.</p><p><b>METHODS</b>A total of 151 clinical patients with H1N1 infection were enrolled in this study, from whom 833 dynamic throat swab samples were obtained for detecting the H1N1 RNA using real-time PCR. A statistical analysis of the age distribution was performed among the patients with different disease courses. Chi-square for trend test was used to study the correlation between the detection rates of H1N1 RNA and the time of disease onset.</p><p><b>RESULTS</b>The majority of patients were young with their ages ranging from 10 to 20 years (57.26%) and 20 to 30 years (22.18%). Chi-square for trend test revealed that the positivity rates of the throat swabs in the patients decreased with the prolongation of the disease course (chi(2)=9.784, P=0.002).</p><p><b>CONCLUSION</b>Most of the H1N1 patients are young within the age range of 10-30 years, and the longest disease course can exceed 10 days. The positivity rates of throat swabs from the H1N1 patients decreases with the prolongation of the disease course.</p>

An analysis on genetic characteristics of hemagglutinin and neuraminidase of type B influenza viruses in Guangzhou in 2006 / 病毒学报

To understand the genetic characteristics of hemagglutinin (HA) and neuraminidase (NA) of type B influenza viruses in Guangzhou in 2006, three virus strains from etiology surveillance and seven strains from outbreaks were investigated. Genome RNAs of type B influenza viruses were extracted and reverse-transcripted into cDNAs using random primers. The whole-length DNA of HA and NA were amplified by polymerase chain reaction (PCR), cloned into T-A plasmid and sequenced, and analyzed phylogenetically by DNAstar software. The results showed that the HA of type B influenza viruses were similar and the homology were more than 99%. The type B influenza viruses belong to Victoria lineage. The NA of the type B influenza viruses were similar and the homology were more than 98%. Phylogenetic trees of HA and NA showed that the isolates from etiology surveillance formed a cluster, and the isolates from outbreaks were separated from the cluster. The homology of the type B influenza viruses with B/Shanghai/361/2002, which is the WHO recommended influenza vaccine strain in 2005-2006, were 88.9%-89.7%. It suggested the protective effect of influenza vaccine against type B influenza viruses used in 2005-2006 in Guangzhou may not be afforded.

Study on human case of avian influenza in Guangzhou 2006 without causing human-to-human transmission among close contacts / 中华流行病学杂志

<p><b>UNLABELLED</b>Study on human case of avian influenza in Guangzhou 2006 without causing human-to-human transmission</p><p><b>OBJECTIVE</b>To explore the possibility of transmission from a human case of avian influenza to his close contacts.</p><p><b>METHODS</b>Close contacts of the human case of avian influenza in Guangzhou 2006 were found out according to the definition and methods publicized by the Ministry of Health, People's Republic of China. Epidemiological investigation and medical observation were carried out. Serum antibodies were tested in some of the close contacts.</p><p><b>RESULTS</b>The avian influenza patient had never left Guangzhou in the month prior to disease onset. No contact history with dead or diseased poultry was found. A total of 56 close contacts, including his girl friend, relatives, friends and medical staff who had taken care of him, were brought under medical observation for 7 days but none of them showed signs of infection.</p><p><b>CONCLUSION</b>Unlike SARS, direct contact with patient contracted with avian influenza at the end of incubation period and in the stage of illness through flying droplets, saliva, mucous membrane and skin injuries will not lead to human-to-human transmission, indicating the virus' ability to pass from human to human is limited.</p>

The effects of 4 laboratory test kits in early detecting of severe acute respiratory syndrome coronavirus / 中华流行病学杂志

<p><b>OBJECTIVE</b>To compare the 4 test kits on severe acute respiratory syndrome coronavirus (SARS-CoV) gene, antigen and antibody for early diagnose of SARS patients.</p><p><b>METHODS</b>Three enzyme linked immunosorbent assay (ELISA) kits were used to detect SARS-CoV IgG, IgM and N protein and fluorescent polymerase chain reaction (F-PCR) kit was used to detect SARS-CoV RNA.</p><p><b>RESULTS</b>In 162 serum samples, 90.2% (55/61) became N protein positive in 1 - 5 days and 92.8% (13/14) became positive IgM and IgG in 15 - 18 days after the onset of disease, respectively. On 82 gorgling samples, the positive rates of F-PCR were 56.3% (14/24) in 1 - 5 days and 71.4% (10/14) in 6 - 9 days after the onset.</p><p><b>CONCLUSION</b>Other than F-PCR, N protein had good effect in the early detection on dubious patients which could lead to effective prevention and control of the epidemic.</p>

Study on the epidemiology and measures for control on severe acute respiratory syndrome in Guangzhou city / 中华流行病学杂志

<p><b>OBJECTIVE</b>To analyze the epidemiological characteristics, related risk factors, measures for its control of severe acute respiratory syndrome (SARS).</p><p><b>METHODS</b>Data on epidemiological features, pathogens and measures for control were collected and analyzed.</p><p><b>RESULTS</b>Since Jan 2003, infectious atypical pneumonia (AP) has become epidemic in Guangzhou city. The first autochthonous case was identified on Jan 2nd. Number of cases started to increase since February and reached peak in the early 10 days of February. Hereafter the epidemic tended to decline in March and since early April, the average number of new cases began to decrease, less than 10 per day. Epidemiological studies revealed that the number of cases aged between 20 and 50 was higher than that below the age of 20. Of the total 966 cases, 429 were males versus 537 females. Geographically, the epidemics covered all 13 districts of Guangzhou, but 95% of the cases concentrated in 7 urban districts. As for professional distribution, health care workers accounted for 28.67% of the total cases. There were 36 deaths, aged from 5 to 89, with half of them older than 60. Out of the victims, 38.9% of them had complications as hypertension, diabetes, heart diseases and COPD etc. Data regarding the clustering features of cases showed that there were 42 families having 2 or more cases in one family, while 277 health workers suffered from SARS were concentrated in 28 hospitals. Only one outbreak took place in a public setting but no outbreak was reported in schools. Relevant research also indicated that SARS could be classified as an air-borne infectious disease, transmitted through aerosol and droplets, but close contact also played an important role in the mode of transmission. The disease was highly infectious, suggesting that people who had close contact with patients in the place with poor ventilation was in greater risk of getting infection. The incubation period ranged from 1 to 11 days (mainly from 3 to 8 days), with an average of 5 days. According to our observation, the following measures might be effective such as: early diagnosis, isolation and treatment provided to the patients, and suspected cases under medical observation should also be put in separate places. Improving ventilation and regular disinfection over air and stuff in hospital wards were also recommended. In order to prevent iatrogenic infection, sense on self-protection among health care workers must be strengthened. Patients were not allowed to be visited by any one other than hospital staff.</p><p><b>CONCLUSION</b>SARS is a preventable disease and can be under control. It is of great importance to prevent clustered SARS cases and the prevention of iatrogenic infection is essential.</p>