Strains In Guangzhou Research Articles

Transcriptome Analysis of Response to Zika Virus Infection in Two Aedes albopictus Strains with Different Vector Competence

Zika virus (ZIKV), which is mainly transmitted by Aedes albopictus in temperate zones, can causes serious neurological disorders. However, the molecular mechanisms that influence the vector competence of Ae. albopictus for ZIKV are poorly understood. In this study, the vector competence of Ae. albopictus mosquitoes from Jinghong (JH) and Guangzhou (GZ) Cities of China were evaluated, and transcripts in the midgut and salivary gland tissues were sequenced on 10 days post-infection. The results showed that both Ae. albopictus JH and GZ strains were susceptible to ZIKV, but the GZ strain was more competent. The categories and functions of differentially expressed genes (DEGs) in response to ZIKV infection were quite different between tissues and strains. Through a bioinformatics analysis, a total of 59 DEGs that may affect vector competence were screened-among which, cytochrome P450 304a1 (CYP304a1) was the only gene significantly downregulated in both tissues of two strains. However, CYP304a1 did not influence ZIKV infection and replication in Ae. albopictus under the conditions set in this study. Our results demonstrated that the different vector competence of Ae. albopictus for ZIKV may be determined by the transcripts in the midgut and salivary gland, which will contribute to understanding ZIKV-mosquito interactions and develop arbovirus disease prevention strategies.

Genetic characterization of two G8P[8] rotavirus strains isolated in Guangzhou, China, in 2020/21: evidence of genome reassortment

BackgroundThe G8 rotavirus genotype has been detected frequently in children in many countries and even became the predominant strain in sub-Saharan African countries, while there are currently no reports from China. In this study we described the genetic characteristics and evolutionary relationship between rotavirus strains from Guangzhou in China and the epidemic rotavirus strains derived from GenBank, 2020–2021.MethodsVirus isolation and subsequent next-generation sequencing were performed for confirmed G8P[8] specimens. The genetic characteristics and evolutionary relationship were analyzed in comparison with epidemic rotavirus sequences obtained from GenBank.ResultsThe two Guangzhou G8 strains were DS-1-like with the closest genetic distance to strains circulating in Southeast Asia. The VP7 genes of the two strains were derived from a human, not an animal G8 rotavirus. Large genetic distances in several genes suggested that the Guangzhou strains may not have been transmitted directly from Southeast Asian countries, but have emerged following reassortment events.ConclusionsWe report the whole genome sequence information of G8P[8] rotaviruses recently detected in China; their clinical and epidemiological significance remains to be explored further.

The Potential Vector Competence and Overwintering of West Nile Virus in Vector Aedes Albopictus in China.

West Nile virus (WNV) is an arbovirus, which causes widespread zoonotic disease globally. In China, it was first isolated in Jiashi County, Kashgar Region, Xinjiang in 2011. Determining the vector competence of WNV infection has important implications for the control of disease outbreaks. Four geographical strains of Aedes Albopictus (Ae. Albopictus) in China were allowed to feed on artificial infectious blood meal with WNV to determine the infection and transmission rate. The results indicated that four strains of Ae. Albopictus mosquitoes could infect and transmit WNV to 1- to 3-day-old Leghorn chickens. The infection rates of different strains were ranged from 16.7 to 60.0% and were statistically different (χ2 = 12.81, p < 0.05). The highest infection rate was obtained from the Shanghai strain (60.0%). The transmission rates of Ae. Albopictus Shanghai, Guangzhou, Beijing, and Chengdu strains were 28.6, 15.2, 13.3, and 6.7%, respectively. Furtherly, the results reveal that Ae. Albopictus Beijing strain infected orally can transmit WNV transovarially even the eggs are induced diapausing. The study confirmed that WNV could survive in the diapause eggs of Ae. Albopictus and could be transmitted to progeny after diapause termination. This is of great significance for clarifying that the WNV maintains its natural circulation in harsh environments through inter-epidemic seasons.

Molecular detection and genetic characterization of Wenzhou virus in rodents in Guangzhou, China

BackgroundWenzhou virus (WENV), a newly discovered mammarenavirus in rodents, is associated with fever and respiratory symptoms in humans. This study was aimed to detect and characterize the emerging virus in rodents in Guangzhou, China.ResultsA total of 100 small mammals, including 70 Rattus norvegicus, 22 Suncus murinus, 4 Bandicota indica, 3 Rattus flavipectus, and 1 Rattus losea, were captured in Guangzhou, and their brain tissues were collected and pooled for metagenomic analysis, which generated several contigs targeting the genome of WENV. Two R. norvegicus (2.9%) were further confirmed to be infected with WENV by RT-PCR. The complete genome (RnGZ37-2018 and RnGZ40-2018) shared 85.1–88.9% nt and 83.2–96.3% aa sequence identities to the Cambodian strains that have been shown to be associated with human disease. Phylogenetic analysis showed that all identified WENV could be grouped into four different lineages, and the two Guangzhou strains formed an independent clade. We also analyzed the potential recombinant events occurring in WENV strains.ConclusionsOur study showed a high genetic diversity of WENV strains in China, emphasizing the relevance of surveillance of this emerging mammarenavirus in both natural reservoirs and humans.

Prevalence of GII.4 Sydney Norovirus Strains and Associated Factors of Acute Gastroenteritis in Children: 2019/2020 Season in Guangzhou, China

Norovirus, the leading cause of non-bacterial acute gastroenteritis (AGE) worldwide, is constantly mutating. Continuous monitoring of the evolution of epidemic genotypes and emergence of novel genotypes is, therefore, necessary. This study determined the prevalence and clinical characteristics of norovirus strains in AGE in Guangzhou, China in 2019/2020 season. This study included children aged 2–60 months diagnosed with AGE in Guangzhou Women and Children Hospital, from August 2019 to January 2020. Norovirus was detected by real-time polymerase chain reaction and clinical data were obtained. Genotyping and phylogenetic analyses were performed with partial gene sequence fragments located within the open reading frames 1 and 2. During the study period, 168 children (61.3% males) were confirmed as norovirus infectious AGE. The main symptoms were diarrhoea and vomiting and 38 patients (22.6%) had seizures. Norovirus was mainly prevalent in October and November, and GII.4 Sydney[P31] was the major genotype circulating in Guangzhou. The phylogenetic tree showed that the Guangzhou strains had high homology with the strains circulating in 2017–2019 worldwide. GII.4 Sydney was the main prevalent norovirus genotype in Guangzhou from August 2019 to January 2020, which had more severe diarrhoea than those of other genotypes. These findings provide a valuable reference for the prevention, control, and treatment of norovirus in the future.

Genomic characterization of Wenzhou mammarenavirus detected in wild rodents in Guangzhou City, China

Wenzhou mammarenavirus (WENV) is a zoonotic pathogen newly discovered in east and southeast Asia. WENV has been found in wild rodent animals around the world while its standing is barely understood in Guangzhou city, where is known as a region of outbreak hotspot for zoonotic emerging infectious diseases. To investigate the prevalence and genomic characteristics of mammarenavirus in Guangzhou City, lung tissue samples from wild rodent species were collected from five districts of Guangzhou City in the year 2015 and 2016. The viral RNA was extracted and then subjected to mammarenavirus-specific PCR. The result revealed approximately 1.0% (3/306) nucleic acid positivity for lung tissue samples obtained from three rodent species: Mus musculus, Rattus flavipectus, and Rattus norvegicus. Viral metagenomic sequencing of three samples was then carried out and two full segment L and three full segment S sequences were obtained. Phylogenetics analysis indicated the sequences of the new mammarenavirus strain have 76.2% - 94.4% similarity to known WENV encoded genes, with the highest similarity to the WENV 9–24 strain. Population structure analysis grouped all known WENV into seven lineages, and this WENV Guangzhou strain was grouped with WENV 9–24 as well. Though the seroprevalence result was not available, our data provides the first nucleic acid evidence of circulating WENV in Guangzhou city, and it suggested WENV had a broader host tropism than previously known.

Representative Genotyping, Recombination and Evolutionary Dynamics Analysis of TSA56 Gene Segment of Orientia tsutsugamushi.

Scrub typhus is a zoonotic disease caused by Orientia tsutsugamushi (O. tsutsugamushi). Orientia tsutsugamushi has various genotypes and more new strains with difference in sequences increasingly appeared. Whether the accurateness of one special nested PCR method which amplifies segment instead of entire open reading frame (ORF) sequence meets the current work of identifying new strains and classifying genotypes remains to be confirmed. And the origins and evolution of this organism have not been thoroughly elucidated. Accordingly, in this study, segments and the entire ORF of the 56-kDa type-specific antigen (TSA56) gene of O. tsutsugamushi were collected, including 209 clinically isolated strains in Guangzhou, China from 2012 to 2016 and 139 reference strains worldwide. By performing phylogenetic analysis, we proved that the accurateness of the particular PCR method which almost met detection need. This re-grouping result showed that segments perfectly represented and identified strains of Karp, Boryong, Gilliam, TA763, Kawasaki and part of Kato genotype, and this accuracy is not restricted by region and time. Sequence diversification of Shimokoshi and some Kato strains made their genotyping need to consider entire ORF sequences, but their weak recognition might not be due to recombination. The frequent genetic recombination and high point mutations contributed to genetic diversification of the TSA56 gene. Major overlapping regions of most recombination events occurred between strains of the same genotype, especially Karp and Kato genotype. And cross-genotype overlapping events occurred between Karp and Boryong/Gilliam/TA763/Kato, Kato and Kawasaki/Gilliam/TA686, Boryong and TA686, and Gilliam and Kawasaki. But Segment has quite low recombination frequency and stable mutation trend from 1943 to 2016. So segment is a relatively conserved part of the TSA56 ORF as for its stable trend of genetic diversity, and it may anchor and represent the entire TSA56 ORF gene. And genetic diversity is rejected as one potential reason for the increased incidence of scrub typhus. But an occasional recombination event created an unrecognized genotype which might be due to the breakage of VD II and AD II. Additionally, strains in Guangzhou were homologous and Karp genotype was detected as a dominant.

Vector Competence and Vertical Transmission of Zika Virus in Aedes albopictus (Diptera: Culicidae).

Zika virus (ZIKV) is an emerging mosquito-borne pathogen belonging to the genus Flavivirus of the family Flaviviridae. Aedes albopictus is widely distributed in China. However, little is known about the vector competence of Ae. albopictus in China. The present study presents the oral susceptibility and vector competence of Ae. albopictus Guangzhou strain to ZIKV. Additionally, vertical transmission of ZIKV is described. The results demonstrated the susceptibility of local Ae. albopictus mosquitoes to ZIKV with an extrinsic incubation period of 6 days. Disseminated infection was observed in Ae. albopictus starting on day 2 postinfection (PI). Starting on day 6 PI, the saliva of Ae. albopictus exhibited ZIKV infection, and the transmission rate was 36.4%. Vertical transmission was observed during the first gonotrophic cycle. The minimum infection rate was observed in third-to-fourth instar larvae.

Genome characteristics and molecular evolution of the human sapovirus variant GII.8

Human sapovirus is regarded as an important viral agent for acute diarrhea worldwide. GII.8, a recently reported genotype, has been detected in a few countries and regions. In this study, we obtained the first genome sequence of a sapovirus GII.8 strain isolated in mainland China, and comprehensively analyzed the genetic diversity and evolutionary process of this genotype. The viral genome of the new GII.8 Guangzhou strain GZ2014-L231 comprised 7433 nucleotides, including two ORFs. Pairwise alignments of the new genome with representative sequences of different genotypes showed inconsistent homology between different protein-encoding regions, of which NS1 and VP2 were found as the variable proteins, and NS3, NS5, and NS6/7 were found as the conserved ones. Compared with other reported GII.8 genomes, the Guangzhou strain introduced 34 new nucleotide changes and one new amino acid change. Phylogenetic analysis based on full-length VP1 sequences demonstrated that 11 GII.8 strains could be divided into 4 clusters A-D, with 88 SNP and 10 SAP spots occurred during their evolutionary process. The Guangzhou strain has higher homology with seven GII.8 strain detected after 2014, especially the US and Peruvian strains of 2015/2016, which have the identical VP1 amino acid sequences. Using a Bayesian coalescent method based on VP1 sequences, GII.8 was predicted to emerge in 2001 with the evolution rate of 1.45 × 10−3 nucleotide substitutions/site/year (strict clock). In summary, the data in this study not only provided reference data from mainland China for sapovirus researches in future, but also firstly described the evolutionary process of the GII.8 genotype.

Antibiotic resistant mechanism and epidemiological characteristics of azithromycin-resistant Neisseria gonorrhoeae strains in Shenzhen

Objective To investigate the prevalence, molecular mechanism and genetic characteristics of azithromycin-resistant Neisseria gonorrhoeae (N.gonorrhoeae) strains isolated in Shenzhen. Methods N. gonorrhoeae strains were collected in Shenzhen from 2011 to 2015. Agar dilution method and E-test were used to detect the minimum inhibitory concentrations (MIC) of these strains to azithromycin. All azithromycin-resistant (AZM-R) strains (MIC≥2 μg/ml) and some azithromycin-sensitive strains (MIC≤0.25 μg/ml) which were randomly selected as the control group were screened for mutations in 23S rRNA, mtrR and erm genes and genotyped by using N. gonorrhoeae multi-antigen sequence typing (NG-MAST). Results A total of 788 N. gonorrhoeae strains were collected, 148 (18.8%) of which were AZM-R strains (MIC≥1 μg/ml). Eighteen out of 21 high-level AZM-R (AZM-HLR) strains had A2143G mutations in the four copies of the 23S rRNA gene. Twelve out of 29 middle-level AZM-R (AZ-MLR) strains had missense mutations, among which C2611T mutations in the four copies of the 23S rRNA were detected in 10 strains. Incidence of G45D/Y105H mutation in AZM-HLR strains was higher than that in AZM-MLR (χ2=12.702, P=0.000) or AZ-S (χ2=4.462, P=0.035) strains according to the analysis of the promoter and coding region of mtrR gene. PCR analysis revealed that only one strain carried ermB gene (MIC=2 μg/ml). The 788 N. gonorrhoeae strains were typed into 81 sequence types (STs) by NG-MAST, most of which were represented by one strain only. STs of ST3356 and ST1866 that were identified in the AZ-R strains in the current study had been noted in a previous report of emerging AZM-R N. gonorrhoeae strains in Nanjing, Chongqing and Guangzhou. Neighbor-joining (NJ) phylogenetic tree showed that the resistant strains did not form a separate cluster. Conclusion Currently, it is not suitable to use azithromycin as a monotherapy for gonorrhea in Shenzhen. Mutations of A2059G and C2611T in 23S rRNA of N. gonorrhoeae were respectively responsible for high-level and middle-level resistance to azithromycin. Repeated emergence of ST1866 and ST3356 will help us monitor and analyze the epidemiological characteristics of N. gonorrhoeae strains resistant to azithromycin in Shenzhen. Key words: Neisseria gonorrhoeae; Azithromycin; Resistance gene; NG-MAST

Phylogenetic analysis of envelope gene of dengue virus serotype 2 in Guangzhou, 2001-2015

Objective: To investigate the molecular characteristics of dengue virus serotype 2 (DENV2) in Guangzhou during 2001-2015, and analyze the E gene of the strains isolated, the phylogenetic tree and molecular clock were constructed to know about the evolution of the strains. Methods: The serum samples of the patients were detected by real time PCR, and positive samples were used to isolate dengue virus by using C6/36 cells. The E gene of the isolated strains were sequenced. The phylogenetic tree was constructed by using software Mega 4.0, and the molecular clock was drawn by using software BEASTv1.8.2. Results: Twenty-six dengue virus strains were isolated between 2001 and 2015. They were all clustered into 2 genotypes, i.e. cosmopolitan genotype and Asian genotype Ⅰ. The strains isolated in Guangzhou shared high homology with Southeast Asian strains. The cosmopolitan genotype was divided into 2 sub-genotype at about 46 and 35 years ago. The substitution rate of dengue virus serotype 2 in Guangzhou was 7.1 × 10(-4) per year per site. Conclusions: There were close relationship between the Guangzhou strains and Southeast Asian strains. Guangzhou was at high risk of imported dengue fever, outbreak of dengue hemorrhagic fever and dengue shock syndrome. There might be two ways of introduction of cosmopolitan genotype. The substitution rate of the strains in Guangzhou was similar to that in the neighbor countries.

Laboratory and Molecular Characterization of Dengue Viruses in a 2014 Outbreak in Guangfo Region, Southern China.

Non-specific symptoms and low viremia levels make early diagnosis of dengue virus (DENV) infection challenging. This study aimed to i) identify laboratory markers that can be used to predict a DENV-positive diagnosis and ii) perform a molecular characterization of DENVs from the 2014 Guangdong epidemic. This retrospective study analyzed 1,044 patients from the Guangdong epidemic who were clinically suspected cases of dengue. Viral RNA was detected by real-time RT-PCR, and viral-specific NS1 antigen was detected using enzyme-linked immuno sorbent assay. A molecular phylogenetic analysis was performed for the with the DENV C-prM gene junction. Patients with dengue infection had leukopenia (2.8 × 109/L), thrombocytopenia (109.0 × 109/L), elevated aspartate aminotransferase (56.0 IU/L) and alanine aminotransferase (43.5 IU/L), and prolonged activated partial thromboplastin time (APTT, 33.5 s) (all P ＜ 0.001) compared to patients without dengue. The positive predictive value of leukopenia and thrombocytopenia for DENV infection were 96.9% and 93.0%, respectively. Leukopenia, thrombocytopenia, elevated aminotransferases, and prolonged APTT were useful predictive markers for an early diagnosis of DENV infection. Phylogenetic analysis indicated that the DENVs from the 2014 epidemic were closely related to a 2010 New Delhi strain and a 2013 Guangzhou strain. The 2014 epidemic consisted of co-circulating DENV-1 genotypes I and V from multiple origins. Efficient dengue surveillance can facilitate rapid response to future outbreaks.

Molecular characterization and genotype shift of dengue virus strains between 2001 and 2014 in Guangzhou.

We studied the evolution, genotypes, and the molecular clock of dengue virus serotype 1 (DENV-1), between 2001 and 2014 in Guangzhou, China. The analysis of the envelope (E) gene sequences of 67 DENV-1 strains isolated in Guangzhou, together with 58 representative sequences downloaded from NCBI, have shown shifts in viral genotypes. The genotype changed several times, from genotype I to IV in 2002, from IV to I in 2005, and from I to V in 2014. These genotype shifts may be the cause of DENV outbreaks. The diversity of genotypes and clades demonstrates a high risk of future outbreaks in Guangzhou. The mean rate of virus nucleotide substitution in Guangzhou was determined to be 7·77 × 10-4 per site per year, which represents a medium substitution rate compared to two other countries. Our research can point to different ancestors of the isolated strains, which may further reveal the different origins and transmission of DENV-1 strains in Guangzhou.

Assess the Possibility of Screening and Supervising Influenza A (H7N9) Virus-Infected Patients via Rapid Point-of-Care-Test Kit with Upper or Lower Respiratory Specimens

The purpose of this study was to assess the possibility of screening and supervising influenza A (H7N9) virus infected patients via rapid point-of-care-test kit with upper or lower respiratory specimens. Here, we demonstrate that the POCT kits can detect H7N9 virus (Guangzhou strain) in different type of samples, which obtained from upper and lower respiratory tract, via the simulated experiment. The detection limit ranged from 4 to 6 log10TCID50/mL and 2.78 × 107 to 1.05 × 108 copies/mL in PBS and nasopharyngeal swab solution (NSS) solutions respectively. Furthermore, the detection ranges were enhanced by 0.5 or 1 log10TCID50/mL in BALF or sputum solution (SS) diluents for some parts of the POCT kits. Furthermore, we observed that there were higher replication and longer screening of H7N9 virus in lower respiratory tract (LRT) samples, such as endotracheal aspirate (ETA) and sputum, from the H7N9 virus-infected patients, although the detection results of POCT kits were negative for these clinical samples. So that, we think that POCT kits can be used to screen and supervise H7N9 virus-infected patients if in the accurate timing. And the LRT samples, special ETA and sputum, seem a good sample option for detecting H7N9 virus via POCT kits, so we need pay more attention to the LRT samples when the new POCT kits were developed.

Status of insecticide resistance and selection for imidacloprid resistance in the ladybird beetle Propylaea japonica (Thunberg)

Field populations or strains of Propylaea japonica collected from four places in southern China (Guangzhou, Nanning, Guilin, and Yuxi) were tested for susceptibility to four insecticides (abamectin, imidacloprid, beta-cypermethrin, and chlorpyrifos) by the Petri-dish Potter tower method and compared with an insecticide-susceptible strain. Concentrations that proved lethal for 50% of the tested individuals (LC50) were estimated by probit analysis, and resistance factors (RF) were calculated at the LC50 level, which ranged from 1.6 to 10.1, depending on the insecticide. In addition, the Guangzhou strain formed the original population for imidacloprid resistance selection. After selection for 20 generations, the resistance had increased 39.3-fold. Fitness analysis in terms of such traits as fecundity, days to maturity, and survival showed that although both resistant and susceptible populations developed at comparable rates, the resistant strain was less fecund (it laid fewer eggs and a smaller proportion of those eggs hatched and resulted in adults), attaining a fitness score of only 0.56 relative to the susceptible strain. These observations suggest that it is possible to detect strains of P. japonica highly resistant to insecticides under laboratory conditions, and that resistance to imidacloprid carries considerable fitness costs to P. japonica. The study served to expand our understanding of the impact of imidacloprid resistance on biological parameters of P. japonica in more detail and to facilitate the deployment of natural enemies resistant to insecticides in integrated pest management.

A survey of the 2014 dengue fever epidemic in Guangzhou, China

In 2014, a serious dengue outbreak in Guangzhou occurred, consisting of 37 354 laboratory confirmed cases of infection. In this study, the clinical picture of dengue fever due to dengue virus (DENV) type 1 in Guangzhou was described. Clinical and laboratory data collected by studying 726 sera of suspected clinical cases from hospitals and 328 sera of healthy persons from two residence communities were analyzed during the outbreak, and 484 patients were diagnosed with an acute dengue infection. Fever, headache, congestion of the throat, and myalgia were the most typical symptoms in DENV-infected patients. Thrombocytopenia, leukopenia, and an increase in liver enzymes were significantly more common in the infected patients than in the healthy controls. Fourteen cases of silent infection were discovered among the 328 healthy persons, suggesting a DENV inapparent infection rate of 4.27% among healthy individuals. The data obtained by analyzing 212 positive sera with three methods indicated different results with different detection methods. DENV RNA should be used for early diagnoses during days 1–6 after symptom onset, immunoglobulin M (IgM) can be easily recognized after four days have passed since symptom onset and DENV isolation has a peak positive rate during days 1–3 after the onset of symptoms. A phylogenetic analysis of viral NS1 gene sequences from this outbreak indicated that the predominant isolates could be categorized as DENV-1 genotype III and had the highest homology with the India genotypes from 2009 to 2011. However, this analysis also revealed a co-epidemic of the 2013 Zhongshan and 2003 Singapore genotypes, both belonging to DENV-1 genotype I, which suggested multiple geographic origins for the 2014 epidemic of dengue 1 strains in Guangzhou.

Molecular epidemiology of Staphylococcus aureus in 10 main cities of China from 2010 to 2011

Objective To investigate the molecular epidemiology of Staphylococcus aureus through analyzing the antibiotic resistance and genotypes of the isolates collected from 10 main cities of China from 2010 to 2011.Methods A total of 507 consecutive and non-duplicate S.aureus isolates were collected from 12 hospitals of 10 cities in China.Antibiotic susceptibility test for 20 antibiotics and spa typing were carried out on all isolates.Results The prevalence of methicillin-resistant S.aureus (MRSA) was 52.9％ (268/507).97.4％ (261/268) of those isolates were multidrug resistance.Among all methicillin-sensitive S.aureus (MSSA) isolates,multidrug resistant rate was 26.8％ (64/239),in which spa-t796 phenotype accounted for 23.4％ (15/64).Thirty-four spa types were identified among MRSA,of which the major clones were spa-t030,spa-t037,spa-t002,spa-t570,spa-t437 and spa-t311.Fifty-eight spa types were detected among MSSA,of which spa-t701,spa-t189,spa-t796,spa-t091 and spa-t571 were the major strains.The geographical distribution of these strains varied significantly.The strains with spa-t030 phenotype was more commonly distributed in Beijing,Xi'an,Wuhan,Tianjin and Chongqing.The spa-037 and spa-t002 were the dominant strains in Shanghai,while spa-t037,spa-t311 and spa-t570 were prevalent strains in Guangzhou,Hangzhou and Shenyang respectively.Notably,the strains with vancomycin MIC greater than or equal to 1 mg/L were largely detected in spa-t037,spa-t570 and spa-t701 (P＜0.05).However,rifampicin resistance was overwhelmingly associated with spa-t030 (P＜0.001).The oxacillin MICs were relatively low in the strains of spa-t437 as compared with other clones (P＜0.001).Conclusion The spa types possessed a feature of distinctive geographical distribution.The major spa types were associated with specific antimicrobial resistance,suggesting more attention should be paid to the phenotypes of bacterial strains for the treatment purpose in clinic. Key words: Staphylococcus aureus ; spa typing; Multidrug resistance; Vancomycin

The N-Terminal Domain of EspF Induces Host Cell Apoptosis after Infection with Enterohaemorrhagic Escherichia coli O157:H7

Enterohemorrhagic Escherichia coli (EHEC) employs a type III secretion system (TTSS) to export the translocator and effector proteins required for mucosal colonization. As an important bacterial effector protein in locus of enterocyte effacement four, the EspF protein causes F-actin filament aggregations to form attaching and effacing (A/E) lesions, and induces the destruction of brush-border microvilli and cytoskeletal rearrangements to form pedestals. However, the molecular pathogenesis of A/E lesions due to EHEC O157:H7 infection is unclear. In this study, we constructed an espF-deficient mutant (ΔespF) with a 162-bp deletion in the N-terminal domain by using overlap extension PCR. The results showed that EHEC EspF translocated into intestinal epithelial cells, targeted mitochondria and induced apoptosis. The ΔespF mutant, compared to EHEC prototype Guangzhou strain, had lower cell attachment and effacement abilities, lower caspase-9/3 and lactate dehydrogenase levels, lower bacterial adhesion, weaker mitochondria apoptosis, and a higher mouse survival rate. Our results demonstrate the probable function of the EspF N-terminal domain, which targets mitochondria and binds mitochondria heat shock protein 70 to induce cell apoptosis via A/E lesions. These findings may be invaluable in clarifying the molecular pathogenesis of EspF of EHEC O157:H7.

Molecular epidemiological and virological study of dengue virus infections in Guangzhou, China, during 2001–2010

BackgroundDengue virus (DENV) infection is the most prevalent arthropod-borne viral infection in tropical and subtropical regions worldwide. Guangzhou has the ideal environment for DENV transmission and DENV epidemics have been reported in this region for more than 30 years.MethodsInformation for DENV infection cases in Guangzhou from 2001 to 2010 were collected and analyzed. The DENV strains were cultured and isolated from patients’ sera. Viral RNA was extracted from cell culture supernatants. cDNA was synthesized by reverse transcription PCR. Phylogenetic trees of four DENV serotypes were constructed respectively.ResultsIn total, 2478 DENV infection cases were reported; 2143 of these (86.43%) occurred during 3 months of the year: August, September and October. Of these, 2398 were local cases (96.77%) and 80 were imported cases (3.23%). Among the imported cases, 69 (86.25%) were from Southeast Asian countries. From the 90 isolated strains, 66.67%, 3.33%, 14.44%, and 15.56% belonged to DENV serotypes 1, 2, 3, and 4, respectively. DENV-1 was predominant in most of the years, including during 2 outbreaks in 2002 and 2006; however, none of the strains or genotypes identified in this study were found to be predominant. Interestingly, DENV strains from different years had different origins. Moreover, the strains from each year belonged to different serotypes and/or genotypes.ConclusionsSoutheast Asia countries were found to be the possible source of DENV in Guangzhou. These findings suggest that there is increasing diversity in DENV strains in Guangzhou, which could increase the risk of DENV outbreaks in the near future.

Analysis of the changes in bacterial types and drug sensitivity profiles of mycobacterial strains in Guangzhou over the last twelve years

To improve evidence-based care in the management of tuberculosis, we retrospectively analyzed the bacterial types and drug sensitivity test results of mycobacteria in Guangzhou over the past twelve years (from July 1998 to March 2010). Over these twelve years, a total of 14 095 mycobacterial strains isolated from different samples were subjected to type identification and drug sensitivity tests according to the Standard Protocols of Laboratory Diagnostics for Tuberculosis by the Chinese Antituberculosis Association. Chi-square test was performed for statistical analyses for comparisons between groups. Of 14 095 strains of mycobacteria isolated, 10 844 strains (76.84%) were MTB, and 3251 strains (23.16%) were non-tuberculosis mycobacteria (NTM). Compared with the result of the fourth national survey of tuberculosis epidemiology, which showed 11.1% of NTM, the one of our study was significantly different (χ(2) = 69.79, P < 0.001). Drug sensitivity tests of MTB showed tolerance rates of 28.99% (2729/9413), 21.75% (2047/9413), 17.45% (1643/9413) and 11.53% (1085/9413) against isoniazid, rifampin, streptomycin and ethambutol, respectively. An increasing trend was observed in MTB drug tolerance against streptomycin, rifampin and isoniazid, whereas more and more NTM strains were isolated in recent years. These findings are worthy of note for clinicians.