Population structure of food-borne Staphylococcus aureus in China / 中华流行病学杂志

Objective: To understand the population structure of food-borne Staphylococcus (S.) aureus in China. Methods: Whole genome sequencing was used to analyze 763 food-borne S. aureus strains from 16 provinces in China from 2006 to 2020. Multilocus sequence typing (MLST), staphylococcal protein A gene (spa) typing, and staphylococcal chromosome cassettemec (SCCmec) typing were conducted, and minimum spanning tree based on ST types (STs) was constructed by BioNumerics 7.5 software. Thirty-one S. aureus strains isolated from imported food products were also included in constructing the genome phylogenetic tree. Results: A total of 90 STs (20 novel types) and 160 spa types were detected in the 763 S. aureus isolates. The 72 STs (72/90, 80.0%) were related to 22 clone complexes. The predominant clone complexes were CC7, CC1, CC5, CC398, CC188, CC59, CC6, CC88, CC15, and CC25, accounting for 82.44% (629/763) of the total. The STs and spa types in the predominant clone complexes changed over the years. The methicillin-resistant S. aureus (MRSA) detection rate was 7.60%, and 7 SCCmec types were identified. The ST59-t437-Ⅳa (17.24%, 10/58), ST239-t030-Ⅲ (12.07%, 7/58), ST59-t437-Ⅴb (8.62%, 5/58), ST338-t437-Ⅴb (6.90%, 4/58) and ST338-t441-Ⅴb (6.90%, 4/58) were the main types in MRSA strains. The genome phylogenetic tree had two clades, and the strains with the same CC, ST, and spa types clustered together. All CC7 methicillin sensitive S. aureus strains were included in Clade1, while 21 clone complexes and all MRSA strains were in Clade2. The MRSA strains clustered according to the SCCmec and STs. The strains from imported food products in CC398, CC7, CC30, CC12, and CC188 had far distances from Chinese strains in the tree. Conclusions: In this study, the predominant clone complexes of food-borne strains were CC7, CC1, CC5, CC398, CC188, CC59, CC6, CC88, CC15, and CC25, which overlapped with the previously reported clone complexes of hospital and community-associated strains in China, suggesting that close attention needs to be paid to food, a vehicle of pathogen transmission in community and food poisoning.

Study of the urban-impact on microbial communities and their virulence factors and antibiotic resistance genomes in the Nandu River, Haikou / 中华流行病学杂志

Objective: To explore the changes in bacterial community structure, antibiotic resistance genome, and pathogen virulence genome in river water before and after the river flowing through Haikou City and their transmission and dispersal patterns and to reveal anthropogenic disturbance's effects on microorganisms and resistance genes in the aquatic environment. Methods: The Nandu River was divided into three study areas: the front, middle and rear sections from the upstream before it flowed through Haikou City to the estuary. Three sampling sites were selected in each area, and six copies of the sample were collected in parallel at each site and mixed for 3 L per sample. Microbial community structure, antibiotic resistance, virulence factors, and mobile genetic elements were analyzed through bioinformatic data obtained by metagenomic sequencing and full-length sequencing of 16S rRNA genes. Variations in the distribution of bacterial communities between samples and correlation of transmission patterns were analyzed by principal co-ordinates analysis, procrustes analysis, and Mantel test. Results: As the river flowed through Haikou City, microbes' alpha diversity gradually decreased. Among them, Proteobacteria dominates in the bacterial community in the front, middle, and rear sections, and the relative abundance of Proteobacteria in the middle and rear sections was higher than that in the front segment. The diversity and abundance of antibiotic resistance genes, virulence factors, and mobile genetic elements were all at low levels in the front section and all increased significantly after flow through Haikou City. At the same time, horizontal transmission mediated by mobile genetic elements played a more significant role in the spread of antibiotic-resistance genes and virulence factors. Conclusions: Urbanization significantly impacts river bacteria and the resistance genes, virulence factors, and mobile genetic elements they carry. The Nandu River in Haikou flows through the city, receiving antibiotic-resistant and pathogen-associated bacteria excreted by the population. In contrast, antibiotic-resistant genes and virulence factors are enriched in bacteria, which indicates a threat to environmental health and public health. Comparison of river microbiomes and antibiotic resistance genomes before and after flow through cities is a valuable early warning indicator for monitoring the spread of antibiotic resistance.

Drug resistance and genomic characteristics of a strain of O139 Vibrio cholerae isolated from human bloodstream infection / 中华预防医学杂志

Objective: To analyze the drug resistance and genomic characteristics of a strain of serogroup O139 Vibrio cholerae producing cholera toxin isolated from the bloodstream of a person with bacteremia. Methods: The broth dilution method and automatic drug sensitivity analyzer were used to determine the antibiotic sensitivity of the strain. The complete genome sequence of the strain was obtained by using second-generation gene sequencing and nanopore sequencing. BLAST software was used for comparison and analysis with CARD, Resfinder, ISfinder, VFDB, and other databases. The drug-resistant genes, insertion sequences and virulence genes carried by the strain were identified. MEGA 5.1 software was used to construct a genetic phylogenetic tree based on the core genomic single nucleotide polymorphisms. Results: V. cholerae SH400, as the toxigenic strain, carried multiple virulence-related genes and four virulence islands. The strain was resistant to streptomycin, tetracycline and cotrimoxazole, carrying corresponding drug-resistant genes. The strain also carried IncA/C plasmid with the size of 172914 bp and contained 10 drug-resistant genes. Combined with the genomic evolutionary relationship, this study found that the drug-resistant genes and drug-resistant plasmids carried among strains showed certain aggregation. The traditional ST type of strain SH400 was ST69, and the cgMLST type was a new type highly similar to cgST-252. Conclusion: This strain of serogroup O139 V. cholerae carries the ctxAB gene, multiple drug-resistant genes and IncA/C plasmid, and there are multiple drug-resistant islands.

Establishment and evaluation of a method for phages enrichment by ferric trichloride-polyvinylidene fluoride membrane filter / 中华预防医学杂志

Objective: To establish and evaluate a method of enriching bacteriophages in natural water based on ferric trichloride-polyvinylidene fluoride (FeCl3-PVDF)membrane filter. Methods: Based on the principle of flocculation concentration, the method of recovering bacteriophage from water sample was established by using iron ion flocculation combined with membrane filter. The titer of phage was determined by Agar double layer method. The recovery efficiency of phage was detected by phage fluorescence staining and real-time fluorescence PCR reaction. Water samples from different sources were collected for simulation experiment to evaluate the enrichment effect. At the same time, the sewage discharged from hospitals was taken as the actual water sample, and the common clinical drug-resistant bacteria were used as the host indicator bacteria to further analyze the enrichment effect of FeCl3-PVDF membrane filter rapid enrichment method on the bacteriophage in natural water samples. Results: The method of enrichment of bacteriophages in natural water by iron ion concentration 50 mg/L and PVDF membrane filter was established. The recovery rate of this method for bacteriophage was 93%-100%. Under the multi-functional microscope, it was found that the bacteriophage of the enriched water sample increased significantly and the fluorescence value of the enriched water sample determined by the enzyme labeling instrument was about 13 times as high as that before enrichment. After concentration of the actual water samples from the hospital drainage, the positive rate of bacteriophage isolation in the concentrated group and the non-concentrated group was 23% and 4%, and the fluorescence value in the concentrated group was 2-24 times as high as that of the non-concentrated group. Conclusion: The method of FeCl3-PVDF membrane filter is a simple, efficient and rapid method for enriching bacteriophages in different water samples.

Early identification of a clustered epidemic of typhoid fever through pathogen molecular subtyping monitoring / 中华预防医学杂志

Objective: To identify a suspected clustered Typhoid fever by whole genome sequencing(WGS) and pulsed field gel electrophoresis (PFGE) subtyping. Methods: The nature of the epidemic was determined by combination of subtyping results of isolates and epidemiological information. Results: Five S. typhimurium isolates showed identical PFGE patterns and almost the same whole genome sequence. Epidemiological survey showed that five cases had dined in the same restaurant on the same day. Conclusion: Combined with the longest incubation period of typhoid fever, molecular subtyping of pathogenic bacteria and the field epidemiological survey, it can be preliminarily determined that the five cases have common infection sources.

Advance on research and application of laboratory pathogen monitoring and early warning technology of bacterial infectious diseases / 中华预防医学杂志

Human beings are still facing the public health challenges from bacterial infectious diseases. Carrying out systematic infectious disease monitoring and early warning is the most direct solution to prevent and control infectious diseases. Etiology is an important part of infectious disease monitoring and early warning. Effective pathogen monitoring can identify pathogens, outbreaks and sources at the first time. In this study, we have reviewed the research and application of etiology monitoring and early warning technology of bacterial infectious diseases and summarized the importance and application scenarios of etiology in infectious disease monitoring and early warning, as well as the research progress of etiology monitoring and early warning technology. Based on the work of existing laboratory monitoring networks, such as Chinese Pathogen Identification Network, the development trend and prospect of infectious disease laboratory network monitoring are put forward to provide a reference for establishing and perfecting the infectious disease monitoring and early warning system.

Combined application of field epidemiology and laboratory etiology analysis in the investigation of a foodborne disease outbreak in Xinjiang uygur Autonomous Region, 2016 / 中华预防医学杂志

Objectives: To analyze the causes of a foodborne outbreak in rural areas of Xinjiang between April 2 and April 5 in 2016. Methods: Cases and the relevant background information were obtained by consulting outpatient records of local health centers and regional people's hospitals and interviewing doctors and residents. All samples were collected by the laboratory test through epidemiological and food hygiene investigations. The χ2 test (Fisher's exact probability method) was used to compare differences in incidence rates. Molecular typing, virulence genes and single nucleotide polymorphisms (SNPS) were analyzed by using Pulsed Field Gel Electrophoresis (PFGE) and Whole Genome Sequencing (WGS). Results: A total of 142 cases were found in this study, with incidence rate at 5.7‰ (142/24 979). Among all cases, the main symptoms were nausea (94%), vomiting (92%) and abdominal pain (67%), and the incubation period was about 2 h (1-7.5 h). There were 16 Staphylococcus aureus isolates identified and all of them could produce A+C+E mixed enterotoxin. PFGE showed 100% homology. WGS further revealed that there were 9 and 1 strains contained by Sequence Type 1 (ST1) and ST5405, respectively. All ST1 strains were in the same clade on the genome tree. Among these, 7 strains shared close proximity (74 SNPs) and 2 strains shared close relationships as well (127 SNPs). The S. aureus isolates that caused the outbreak were introduced by a mutant isolate from the milk supply station. Conclusions: This foodborne outbreak was mainly caused by Staphylococcus aureus contamination.

Application and reflection of laboratory-based monitoring in early warning of infectious diseases / 中华预防医学杂志

Despite the fact that our cognition towards infectious disease prevention, the advanced technology and the economic status of the whole society has made a great progress in the last decade, the outbreak of COVID-19 pneumonia has again enabled the public to acquire more about super-challenges of infectious diseases, epidemics and the relevant preventive measurements. In order to identify the epidemic signals in early stage or even before the onset of epidemic, the data research and utilization of a series of factors related to the occurrence and transmission of infectious diseases have played a significant role in research of prevention and control during the whole period of surveillance and early warning. Laboratory-based monitoring for the etiology has always been an important part of infectious disease warning system due to pathogens as the direct cause of such diseases. China has initially established a laboratory-based monitoring and early warning system for bacterial infectious diseases based on the Chinese Pathogen Identification Network with an aim to identify pathogens, outbreaks and sources. This network has played an essential role in early detection, tracking and precise prevention and control of bacterial infectious diseases, such as plague, cholera, and epidemic cerebrospinal meningitis. This issue focuses on the function of laboratory-based monitoring during the period of early warning, prevention, and control of bacterial infectious diseases, and conducted a wide range of researches based on the analysis of the epidemic and outbreak isolates, together with field epidemiological studies and normal monitoring systems. All of these could illustrate the effect of laboratory surveillance in the infectious disease risk assessment and epidemic investigation. At the same time, we have put forward our review and expectation of scenarios about laboratory-based monitoring and early warning technologies to provide innovative thoughts for promoting a leapfrog development of infectious disease monitoring and early warning system in China.

Comparative Study of the Genetic Diversity, Antimicrobial Resistance, and Pathogenicity of / 生物医学与环境科学（英文）

Objective@#This study was performed to compare the genetic diversity, virulence, and antimicrobial resistance of @*Methods@#A total of 38 clinical strains and 19 strains from healthy individuals were isolated from the samples collected in Ma'anshan City, Anhui Province. Their taxonomy was investigated using concatenated @*Results@#The 57 @*Conclusions@#The taxonomy, virulence properties, and antibiotic resistance of

An Investigation on the Molecular Characteristics and Intracellular Growth Ability among Environmental and Clinical Isolates of Legionella pneumophila in Sichuan Province, China / 生物医学与环境科学（英文）

OBJECTIVE@#To investigate the molecular characteristics and intracellular growth ability of Legionella pneumophila (L. pneumophila) strains from 1989 to 2016 in Sichuan Province, China.@*METHODS@#Seventy-nine isolates of L. pneumophila were collected from environmental and clinical sources, including cooling towers, hot springs, bath water, fountains, and patients, and identified with 16S rRNA gene analysis and serum agglutination assay. The isolates were then typed by Sequence-Based Typing (SBT), and Genotyping of forty-two LP1 strains were analyzed by means of multiple-locus VNTR analysis with 8 loci (MLVA-8). All strains were further analyzed for two virulence genes: Legionella vir homologue (lvh) and repeats in structural toxin (rtxA). The intracellular growth ability of 33 selected isolates was determined by examining their interaction with J774 cells.@*RESULTS@#All isolates were identified to L. pneumophila including 11 serogroups, among which the main serogroup were LP1, accounting for 54.43%. Thirty-three different sequence types (STs) from five main clonal groups and five singletons were identified, along with 8 different MLVA patterns. Both the lvh and rtxA loci were found in all 79 strains. Thirty isolates showed high intracellular growth ability in J774 cells.@*CONCLUSION@#L. pneumophila is a potential threat to public health, and effective control and prevention strategies are urgently needed.

Simultaneous Detection of 13 Key Bacterial Respiratory Pathogens by Combination of Multiplex PCR and Capillary Electrophoresis / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>Lower respiratory tract infections continue to pose a significant threat to human health. It is important to accurately and rapidly detect respiratory bacteria. To compensate for the limits of current respiratory bacteria detection methods, we developed a combination of multiplex polymerase chain reaction (PCR) and capillary electrophoresis (MPCE) assay to detect thirteen bacterial pathogens responsible for lower respiratory tract infections, including Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, Staphylococcus aureus, Mycoplasma pneumoniae, Legionella spp., Bordetella pertussis, Mycobacterium tuberculosis complex, Corynebacterium diphtheriae, and Streptococcus pyogenes.</p><p><b>METHODS</b>Three multiplex PCR reactions were built, and the products were analyzed by capillary electrophoresis using the high-throughput DNA analyzer. The specificity of the MPCE assay was examined and the detection limit was evaluated using DNA samples from each bacterial strain and the simulative samples of each strain. This assay was further evaluated using 152 clinical specimens and compared with real-time PCR reactions. For this assay, three nested-multiplex-PCRs were used to detect these clinical specimens.</p><p><b>RESULTS</b>The detection limits of the MPCE assay for the 13 pathogens were very low and ranged from 10-7 to 10-2 ng/μL. Furthermore, analysis of the 152 clinical specimens yielded a specificity ranging from 96.5%-100.0%, and a sensitivity of 100.0% for the 13 pathogens.</p><p><b>CONCLUSION</b>This study revealed that the MPCE assay is a rapid, reliable, and high-throughput method with high specificity and sensitivity. This assay has great potential in the molecular epidemiological survey of respiratory pathogens.</p>

Legionella dumoffii Tex-KL Mutated in an Operon Homologous to traC-traD is Defective in Epithelial Cell Invasion / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>To understand the mechanism of invasion by Legionella dumoffii.</p><p><b>METHODS</b>The L. dumoffii strain Tex-KL was mutated using the Tn903 derivative, Tn903dIIlacZ. After screening 799 transposon insertion mutants, we isolated one defective mutant. We then constructed the gene-disrupted mutant, KL16, and studied its invasion of and intracellular growth in HeLa and A549 cells, and in A/J mice survival experiments. The structure of traC-traD operon was analyzed by RT-PCR.</p><p><b>RESULTS</b>The transposon insertion was in a gene homologous to Salmonella typhi traC, which is required for the assembly of F pilin into the mature F pilus structure and for conjugal DNA transmission. Results from RT-PCR suggested that the traC-traD region formed an operon. We found that when the traC gene was disrupted, invasion and intracellular growth of L. dumoffii Tex-KL were impaired in human epithelial cells. When mice were infected by intranasal inoculation with a traC deficient mutant, their survival significantly increased when compared to mice infected with the wild-type strain..</p><p><b>CONCLUSION</b>Our results indicated that the traC-traD operon is required for the invasion and intracellular growth abilities of L. dumoffii Tex-KL in epithelial cells.</p>

Three quantitative methods to continuously monitor Legionella in spring water / 中华预防医学杂志

<p><b>OBJECTIVE</b>To compare the detection effect of Legionella pollution in spring water by three methods, namely traditional plating method, fluorescent quantitation PCR method and ethidium monoazide (EMA) fluorescent quantitation PCR method.</p><p><b>METHODS</b>Every month (except May), we collected 11 water samples from the 5 selected hot spring pools in one hot spring resort in Beijing in 2011. A total of 121 water samples were collected, and then were detected by the above three methods qualitatively and quantitatively.</p><p><b>RESULTS</b>In our study, the Legionella pollution rate was separately 74.4% (90/121), 100.0% (121/121) and 100.0% (121/121) by the above three methods. The quantitative value of Legionella in the 121 water samples detected by the three methods were around 0.10-216.00 colony-forming units (CFU)/ml, 1.47-1557.75 gene units (GU)/ml and 0.20-301.69 GU/ml, respectively. The median (25th and 75th percentiles) was 75.30 (32.51-192.10) GU/ml, 36.46 (16.08-91.21) GU/ml and 5.30 (0.00-33.70) CFU/ml, respectively. The difference in the quantitative value of Legionella detected by the three methods showed statistical significance (χ(2) = 187.900, P < 0.01). The quantitative value of Legionella detected by fluorescent quantitation PCR method was the highest, followed by the value Legionella detected by EMA-fluorescent quantitation PCR method and traditional plating method.</p><p><b>CONCLUSION</b>The sensitivity of the PCR methods was higher than traditional plating method, in detecting Legionella pollution in spring water, especially the EMA- fluorescent quantitation PCR method, which was more suitable for detecting Legionella in water.</p>

Analysis of molecular subtypes and microflora structure of Neisseria meningitidis strains isolated in Jiangxi province / 中华预防医学杂志

<p><b>OBJECTIVE</b>To study the molecular subtypes and microflora structure of Neisseria meningitidis (Nm) strains isolated in Jiangxi province.</p><p><b>METHODS</b>A total of 123 Nm strains separately isolated from patients, close contacts and health people in 1976-1987 and 2005-2008 were investigated by multilocus sequence typing (MLST) and PorA subtyping, to test the characteristics of gene Nm and sequence porA. Minimum spanning tree was constructed by using BioNumerics software based on data of MLST; and the microflora structure was then analyzed.</p><p><b>RESULTS</b>The serogroups of 67 Nm strains isolated in 1976-1987 included group A (43 strains), group B (18 strains), group C (1 strains) and group W135 (5 strains); while the serogroups of 56 Nm strains isolated in 2005-2008 included group A (3 strains), group B (7 strains), group C (45 strains) and 1 ungrouped strain. The total 123 Nm strains could be divided into 40 MLST types; while the 46 strains in group A could be divided into 14 MLST types, 29 out of which belonged to ST-3 type, accounting for 63.0% (29/46) as the dominant type. All of the 29 strains were isolated between 1976 and 1987, while 14 strains were isolated from patients, 9 were from close contacts and 6 were from health people. The 46 strains in group C could be divided into 5 MLST types, 41 out of which belonged to ST-4821 type, accounting for 89.1% (41/46). All of the strains were isolated between 2005 and 2008, 6 strains were isolated from patients, 6 were from close contacts and 29 were from health people. The porA gene of the total 123 Nm strains were classified to 32 different types, including 24 different VR1 types and 22 different VR2 types. The dominant PorA type of the prevalent strain (ST-3 type, group A) between 1976 and 1987 was P1.7-1, 10, accounting for 39.1% (18/46) of the strains in group A; while the 18 strains were isolated from 11 patients, 4 close contacts and 3 health people. The dominant PorA type of the prevalent strain (ST-4821 type, group C) between 2005 and 2008 was P1.20, 9, accounting for 46.3% (19/41) of the ST-4821 strains in group C; while the 19 strains were isolated from 1 close contacts and 18 health people. P1.7-2, 14 dominated since 2006, including 22 strains, accounting for 53.7% (22/41) of the ST-4821 strains in group C, isolated from 6 patients, 5 close contacts and 11 health people. There were no dominant PorA type found in group B and all the 5 strains in group W135 belonged to ST-174 and the PorA type was P1.21, 16, isolating from 3 close contacts and 2 health people between 1979 and 1980.</p><p><b>CONCLUSION</b>Nm isolated in Jiangxi province showed significant gene polymorphism, as well as predominant lineages existing. In different periods, the prevalent lineages varied a lot, as translating from serogroup A: ST-3:P1.7-1, 10 to serogroup C: ST-4821:P1.7-2, 14 nowadays.</p>

Application of PulseNet China Database in tracking and warning 4 cholerae outbreaks in Anhui province, in 2012 / 中华流行病学杂志

<p><b>OBJECTIVE</b>To track the source of infection regarding 4 Cholerae outbreaks in Anhui province in 2012 through the application of PulseNet China Database (PNCD).</p><p><b>METHODS</b>Cholerae virulence genes were amplified by PCR and typed by pulse field gel electrophoresis(PFGE). Results from electrophoresis were cluster-analyzed by BioNumericsV4.0 software and compared with PNCD.</p><p><b>RESULTS</b>Virulence gene CT and TCP of the tested vibrio cholera showed both positive. Homology of the strains from four cholera outbreaks was more than 98%, based on the homologous and cluster analysis through enzyme digested PFGE electrophoresis. Those strains were highly homologous with the cholera epidemic strains identified in Hunan, Sichuan,Zhejiang, Shanghai and Hubei by PNCD, with the homology as 100% .</p><p><b>CONCLUSION</b>Four cholera outbreaks in Anhui province, 2012 were highly correlated with the outbreaks occurring in Hunan and Sichuan during the same time period, indicating that PNCD could effectively and quickly tracking down the source of infection on the cholera outbreaks and providing early warning of the situation.</p>

Molecular characteristics of Neisseria meningitidis isolated during an outbreak in a jail: association with the spread and distribution of ST-4821 complex serogroup C clone in China / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>To characterize the meningococcal strains isolated from cases and close contacts with meningococcal disease associated with an outbreak in a jail in May 2010 by investigating the national distribution of hyperinvasive ST-4821 serogroup C clone associated with this outbreak.</p><p><b>METHODS</b>The cases were described based on the clinical symptoms and laboratory results. Pharyngeal swabs were cultured for N. meningitidis from men in the jail. Meningococcal isolates were identified by serogrouping, pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST), respectively. Four hundred and sixteen serogroup C N. meningitidis strains were collected from 27 provinces between 2003 and 2010 for a nationwide survey and analyzed by PFGE and MLST.</p><p><b>RESULTS</b>Three persons in a jail system were infected with invasive N. meningitidis serogroup C. All isolates tested had matching PFGE patterns and belonged to the multilocus sequence type (ST) 4821 clonal complex. All 47 N. meningitidis strains were identified from the pharyngeal swabs of 166 peoples in the jail, and 26 of them belonged to ST-4821 serogroup C clone, and 90.14% (375/416) serogroup C strains identified in the nationwide survey belonged to the ST-4821 complex. The ST-4821 serogroup C clone was spread nationwide, distributed in 24 provinces, especially in eastern provinces between 2003 and 2010.</p><p><b>CONCLUSION</b>Endemic transmission and carriage rate of ST-4821 serogroup C clone are high in this jail system. The ST-4821 serogroup C clone is spreading in China and nationwide distributed despite the existence of some effective vaccines.</p>

Optimization of pulse-field gel electrophoresis for Borrelia burgdorferi subtyping / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>To optimize the performance of Pulsed-Field Gel Electrophoresis (PFGE) for the comparison of inter-laboratory results and information exchange of Borrelia burgdorferi subtyping.</p><p><b>METHODS</b>A panel of 34 strains of B. burgdorferi were used to optimize PFGE for subtyping. In order to optimize the electrophoretic parameters (EPs), all 34 strains of B. burgdorferi were analyzed using four EPs, yielding different Simpson diversity index (D) values and the epidemiological concordance was also evaluated.</p><p><b>RESULTS</b>The EP of a switch time of 1 s to 25 s for 13 h and 1 s to 10 s for 6 h produced the highest D value and was declared to be optimal for MluI and SmaI PFGE of B. burgdorferi. MluI and SmaI were selected as the first and second restriction enzymes for PFGE subtyping of B. burgdorferi according to discrimination and consistency with epidemiological data.</p><p><b>CONCLUSION</b>PFGE can be used as a valuable test for routine genospecies identification of B. burgdorferi.</p>

Comparison on the levels of human serum antibody against Neisseria meningitidis serogroup C measured using serum bactericidal assav and ELISA / 中华流行病学杂志

Objective To analyze the levels of human serum antibody against Neisseria meningitidis serogroup C measured by serum bactericidal assay (SBA) and ELISA.Methods SBA and a modified ELISA were applied to measure the serum bactericidal titer and the specific concentration of immunoglobulin G (IgG) against meningoeoccal serogroup C in sera samples.Seventy-five sera were from healthy adults without undertaking vaccination while another 429 and 388pre- and post- vaccinated sera were from 143 infants and 194 young children immunized with conjugate vaccine or polysaccharide vaccine,respectively.Correlation between serum bactericidal titer and the concentration of specific IgG against meningococcal serogroup C was analyzed.Results The concentration of meningococcal serogroup C specific IgG in healthy adults showed a strong correlation (r=0.814 33,P＜0.001 ) with serum bactericidal titer through linear regression analysis.Weak correlation was observed between SBA titers and IgG concentration in pre vaccinated sera of infants and children ( conjugate/polysaccharide vaccine ) ( infants:r =0.140 64,P ＞ 0.100/r =0.2899,P＜0.05; children:r=0.540 40,P＜0.05/r=0.194 36,P＜0.05).After immunization with 2-dose conjugate vaccine in infants and 1-dose in children,a strong correlation between the two panels of results was observed (r=0.809 38,P＜0.001 and r=0.837 23,P＜0.001 respectively).However after immunization with polysaccharide vaccine,the correlation between serum bactericidal titer and concentration of specific IgG was weak (r＜0.500 00).Conclusion Among healthy adults and post vaccinated infants or young children immunized with conjugate vaccine,the concentration of specific IgG was comparable to the serum bactericidal titer against meningococcal serogroup C.However,it was not unfavorable to use ELISA as the principal means of measuring serum antibody responses to polysaccharide vaccine for infants under 1 year old.

Molecular analysis on non-O1 and non-O139 Vibrio cholerae isolates / 中华流行病学杂志

Objective According to results from the two-month consecutive surveillance program in Maanshan,six suspected cases of non-O1 non-O139 Vibrio (V.) cholerae infection,were found that called for identification of pathogens as well as molecular-epidemiological analysis to determine the aggregation of the epidemic situation.Methods Biochemical and serotype identification,hemolysis test,and drug sensitive test were used to detect the drug resistance spectrum.Real-time PCR and conventional PCR were used to detect the presence of V.cholerae specific genes,virulent genes and its related genes,including ompW,ctx,tcpA,toxR,hlyA,zot,ace,rstR and g ⅢCTX.Pulsed-field gel electrophoresis (PFGE) was used to analyze the molecular type of strains.Results All the six isolates of non-O 1 non-O 139 V.cholerae were identified by biochemical and serologic tests,and appeared to be β hemolytic.Twelve out of the 14 kinds of drugs showed 100％ sensitive.All isolates were positive of ompW gene by real-time PCR,but negative for ctx,tcpA,zot,ace,rstR and gⅢ CTK.Five of the six isolates were positive for toxR and hlyA,except for strain 1001434446.All strains had different PFGE types,but two strains had similar types.All strains had a low similarity compared to the toxigenic V.cholerae.Conclusion Six cases ofnon-O1 and non-O139 nontoxigenic V.cholerae infection appeared in the same period.Along with epide(m)iological information,we noticed that these cases had a sporadic nature,but frequently appeared in the same area.We got the impression that public health measurements should be strengthened,with special attention paid to those diarrhea outbreaks caused by non-O 1 /non-O 139 strains since V.cholerae had appeared in low incidence.

Molecular typing of Legionella pneumophila isolates from China with pulsed field gel electrophoresis / 中华流行病学杂志

Objective To analyze the molecular types of Legionella (L.) pneumophila strains isolated in China,and to develop the PulseNet-China Database of L.pneumophila.Methods Pulsed field gel electrophoresis (PFGE) was used to analyze 262 L.pneumophila strains collected from 11 provinces between 2004 and 2009 in China.Different kinds of genomic DNA in different L.pneumophila strains were isolated and separated after digesting with Asc Ⅰ.BioNumerics software was used to analysis the PFGE fingerprints.Results L.pneumophila strains isolated in China were quite different regarding their PFGE patterns.There were 108 PFGE types among the 262 strains tested in this study.The similarity value of these strains was in the range of 16%-100% and the same types were discovered in different provinces and years.Conclusion L.pneumophila strains isolated in China were with high genetic variations.There might be different clones existed in China.The development of PulseNet China Database was thus of great significance in monitoring the L.pneumophila strains in the future.