Establishment and Modification of Ninety-seven Pneumococcal Serotyping Assays Based on Quantitative Real-time Polymerase Chain Reaction.

Objective: To establish and modify quantitative real-time polymerase chain reaction (qPCR)-based serotyping assays to distinguish 97 pneumococcal serotypes. Methods: A database of capsular polysaccharide ( cps) loci sequences was generated, covering 97 pneumococcal serotypes. Bioinformatics analyses were performed to identify the cps loci structure and target genes related to different pneumococcal serotypes with specific SNPs. A total of 27 novel qPCR serotyping assay primers and probes were established based on qPCR, while 27 recombinant plasmids containing serotype-specific DNA sequence fragments were constructed as reference target sequences to examine the specificity and sensitivity of the qPCR assay. A panel of pneumococcal reference strains was employed to evaluate the capability of pneumococcal serotyping. Results: A total of 97 pneumococcal serotyping assays based on qPCR were established and modified, which included 64 serotypes previously reported as well as an additional 33 serotypes. Twenty-seven novel qPCR serotyping target sequences were implemented in the pneumococcal qPCR serotyping system. A total of 97 pneumococcal serotypes, which included 52 individual serotypes and 45 serotypes belonging to 20 serogroups, could not be identified as individual serotypes. The sensitivity of qPCR assays based on 27 target sequences was 1-100 copies/µL. The specificity of the qPCR assays was 100%, which were tested by a panel of 90 serotypes of the pneumococcal reference strains. Conclusion: A total of 27 novel qPCR assays were established and modified to analyze 97 pneumococcal serotypes.

A Campylobacteriosis Outbreak Caused by One Asymptomatic Food Handler Carrier.

In August 2021, three students with diarrhea from the same school visited a local hospital in the S district of Beijing. An epidemic investigation showed that there were more students with diarrhea in the same school and they had one meal together. Campylobacter jejuni was isolated from both patients with diarrhea and asymptomatic food handlers; however, the latter also carried Campylobacter coli. Phylogenomic analysis showed that there was a campylobacteriosis outbreak among the students, and the asymptomatic food handler may have been the source of the infection. Routine inspection and surveillance for Campylobacter is needed for the food producing staff, particularly those cooking in the cafeteria in schools or other public food services.

Genetic and Phenotypic Variation of Campylobacter jejuni NCTC11168 Caused by flhA Mutation during Laboratory Passage.

Objective: Campylobacter jejuni NCTC11168 is commonly used as a standard strain for flagellar biosynthesis research. In this report, two distinguished phenotypic isolates (CJ1Z, flhA mutant strain, lawn; CJ2S, flhA complemented strain, normal colony) appeared during laboratory passages for NCTC11168. Methods: Phenotypic assessments, including motility plates, transmission electron microscopy, biofilm formation assay, autoagglutination assay, and genome re-sequencing for these two isolates (CJ1Z, flhA mutant strain; CJ2S, flhA complemented strain) were carried out in this study. Results: Transmission electron microscopy revealed that the flagellum was lost in CJ1Z. Phenotypic assessments and genome sequencing of the two isolates were performed in this study. The capacity for biofilm formation, colony auto-agglutination, and isolate motility was reduced in the mutant CJ1Z. Comparative genomic analysis indicated a unique native nucleotide insertion in flhA (nt, 2154) that caused the I719Y and I720Y mutations and early truncation in flhA. Conclusion: FlhA has been found to influence the expression of flagella in C. jejuni. To the best of our knowledge, this is the first study to describe the function of the C-terminal of this protein.

Genetic Characteristics of Lipooligosaccharide and Capsular Polysaccharide of Campylobacter jejuni from Different Sources in China.

Objective: To determine the distribution of two important virulence factors [lipooligosaccharide (LOS) and capsular polysaccharide (CPS)] in Campylobacter jejuni ( C. jejuni) isolated from different sources in China and to develop a rapid screening method for Guillain-Barré syndrome (GBS)-associated strains. Methods: Whole-genome sequencing was carried out for 494 C. jejuni strains. The OrthoMCL software was used to define the LOS/CPS gene clusters. CPS genotyping was performed with serotype-specific sequence alignment using the BLAST software. Real-time Polymerase chain reaction (PCR) was developed with the unique sequences of specific CPS types. Results: Nine novel and 29 previously confirmed LOS classes were identified. LOS classes A, B, and C were the most common (48.2%, 238/494) among the 494 strains. Twenty-six capsular types were identified in 448 strains. HS2, HS4c, HS5/31, HS19, and HS8/17 were the most frequent CPS genotypes (58.7%, 263/448). Strains of 17 CPS genotypes (strain number > 5) had one or two prevalent LOS classes ( P < 0.05). Multiplex real-time PCR for rapid identification of HS2, HS19, and HS41 was developed and validated with strains of known serotypes. Conclusion: Our results describe the genetic characteristics of the important virulence factors in C. jejuni strains in China. The multiplex real-time PCR developed in this study will facilitate enhanced surveillance of GBS-associated strains in China.

Genetic Characteristics and Antimicrobial Susceptibility of Arcobacter butzleri Isolates from Raw Chicken Meat and Patients with Diarrhea in China.

Arcobacter is an emerging foodborne pathogen worldwide. In this study, the prevalence, antimicrobial susceptibility and genetic characteristics of Arcobacter from different sources were investigated. Eighteen A. butzleri isolates were obtained from 60 raw chicken meat samples (16/60, 27%) and 150 patients with diarrhea (2/150, 1.3%). The resistance ratios to nalidixic acid, ciprofloxacin, clindamycin, chloramphenicol, and florfenicol were 83.33% (15/18), 38.89% (7/18), 38.89% (7/18), 33.33% (6/18) and 33.33% (6/18), respectively. We performed whole genome sequencing of the 18 isolates, and we predicted antibiotic resistance genes and virulence factors by using assembled genomes through blastx analysis. Two resistance genes, bla OXA-464 and tet(H), and the C254T mutation in gyrA, were identified in the genomes of some resistant isolates. Furthermore, virulence genes, such as flgG, flhA, flhB, fliI, fliP, motA, cadF, cjl349, ciaB, mviN, pldA and tlyA, were found in all strains, whereas hecA, hecB and iroE were found in only some strains. Phylogenetic tree analysis of A. butzleri isolates on the basis of the core-genome single nucleotide polymorphisms showed that two isolates from patients with diarrhea clustered together, separately from the isolates from raw chicken and the chicken strains. This study is the first comprehensive analysis of Arcobacter isolated in Beijing.

Comparison of the Pathogenicity of Neisseria meningitidis Isolates of Hyperinvasive Sequence Type 7 Belonging to Serogroups A, B, C, and X.

OBJECTIVE: To compare the pathogenicity of isolates of sequence type 7 (ST-7) Neisseria meningitidis( N. meningitidis) belonging to four different serogroups (A, B, C, and X). METHODS: Four ST-7 N. meningitidis isolates serogrouped as A, B, C, and X and characterized by different capsule structures, were examined for their adhesion and invasion properties, and their ability to induce cytokine release and apoptosis in the host cell (the A549 cell line). RESULTS: Among the four ST-7 N. meningitidis isolates, the serogroup A isolate possessed the strongest adhesion and invasion ability. This isolate also induced the release of the highest levels of the pro-inflammatory mediators interleukin-6, interleukin-1ß, and interferon, and the highest apoptosis rate in the host cells. However, there was no significant difference in interleukin-8 and tumor necrosis factor-α secretion between the four isolates. Based on the findings, the serogroup X N. meningitidis isolate had the weakest pathogenicity, whereas there was almost no difference in the pathogenicity of the isolates from serogroups B and C. CONCLUSIONS: The differences in the capsular structure of the four isolates of ST-7 N. meningitidis affected their pathogenic capacities. The findings also imply that the hyperinvasive ST-7 N. meningitidis lineage may include hypoinvasive isolates.

Genetic and Antibiotic Resistance Characteristics of Campylobacter jejuni Isolated from Diarrheal Patients, Poultry and Cattle in Shenzhen.

OBJECTIVE: To investigate genetic and antibiotic resistance characteristics of Campylobacter jejuni (C. jejuni) isolated from Shenzhen. METHODS: Multilocs sequence typing and agar dilution methods were used to define the genotype and antibiotic resistance of C. jejuni, respectively. RESULTS: In total, 126 C. jejuni strains were isolated. The prevalence of C. jejuni was 5.3% in diarrheal patients. The prevalence in poultry meat (36.5%) was higher than that in cattle meat (1.1%). However, the prevalence in poultry cloacal swabs (27.0%) was lower than that in cattle stool (57.3%). Sixty-two sequence types were obtained, among which 27 of the STs and 10 alleles were previously unreported. The most frequently observed clonal complexes were ST 21 (11.9%), ST-22 (10.3%), and ST-403 (7.1%). ST-21, ST-45, ST-354, ST-403, and ST-443 complexes overlapped between isolates from patients and cattle, whereas ST-45 and ST-574 complexes overlapped between isolates from patients and poultry. All C. jejuni were resistant to at least one antibiotic. The highest resistance rate was toward ciprofloxacin (89.7%), followed by tetracycline (74.6%), and nalidixic acid (69.0%). CONCLUSION: This is the first report of the genotypes and antibiotic resistance of C. jejuni in Shenzhen. Overlapping clonal complexes were found between isolates from patients and cattle, and between patients and poultry.

Effect of Lactobacillus rhamnosus GG supernatant on serotonin transporter expression in rats with post-infectious irritable bowel syndrome.

AIM: To evaluate the effect of Lactobacillus rhamnosus GG supernatant (LGG-s) on the expression of serotonin transporter (SERT) in rats with post-infectious irritable bowel syndrome (PI-IBS). METHODS: Campylobacter jejuni 81-176 (1010 CFU/mL) was used to induce intestinal infection to develop a PI-IBS model. After evaluation of the post-infectious phase by biochemical tests, DNA agarose gel electrophoresis, abdominal withdrawal reflex (AWR) test, and the intestinal motility test, four PI-IBS groups received different concentrations of LGG-s for 4 wk. The treatments were maintained for 1.0, 2.0, 3.0 or 4.0 wk during the experiment, and the colons and brains were removed for later use each week. SERT mRNA and protein levels were detected by real-time PCR and Western blot, respectively. RESULTS: The levels of SERT mRNA and protein in intestinal tissue were higher in rats treated with LGG-s than in control rats and PI-IBS rats gavaged with PBS during the whole study. Undiluted LGG-s up-regulated SERT mRNA level by 2.67 times compared with the control group by week 2, and SERT mRNA expression kept increasing later. Double-diluted LGG-s was similar to undiluted-LGG-s, resulting in high levels of SERT mRNA. Triple-diluted LGG-s up-regulated SERT mRNA expression level by 6.9-times compared with the control group, but SERT mRNA expression decreased rapidly at the end of the second week. At the first week, SERT protein levels were basically comparable in rats treated with undiluted LGG-s, double-diluted LGG-s, and triple-diluted LGG-s, which were higher than those in the control group and PBS-treated PI-IBS group. SERT protein levels in the intestine were also comparable in rats treated with undiluted LGG-s, double-diluted LGG-s, and triple-diluted LGG-s by the second and third weeks. SERT mRNA and protein levels in the brain had no statistical difference in the groups during the experiment. CONCLUSION: LGG-s can up-regulate SERT mRNA and protein levels in intestinal tissue but has no influence in brain tissue in rats with PI-IBS.

Development and application of a real-time polymerase chain reaction method for Campylobacter jejuni detection.

AIM: To develop a real-time polymerase chain reaction (PCR) method to detect and quantify Campylobacter jejuni (C. jejuni) from stool specimens. METHODS: Primers and a probe for real-time PCR were designed based on the specific DNA sequence of the hipO gene in C. jejuni. The specificity of the primers and probe were tested against a set of Campylobacter spp. and other enteric pathogens. The optimal PCR conditions were determined by testing a series of conditions with standard a C. jejuni template. The detection limits were obtained using purified DNA from bacterial culture and extracted DNA from the stool specimen. Two hundred and forty-two specimens were analyzed for the presence of C. jejuni by direct bacterial culture and real-time PCR. RESULTS: The optimal PCR system was determined using reference DNA templates, 1 × uracil-DNA glycosylase, 3.5 mmol/L MgCl2, 1.25 U platinum Taq polymerase, 0.4 mmol/L PCR nucleotide mix, 0.48 µmol/L of each primer, 0.2 µmol/L of probe and 2 µL of DNA template in a final volume of 25 µL. The PCR reaction was carried as follows: 95 °C for 4 min, followed by 45 cycles of 10 s at 95 °C and 30 s at 59 °C. The detection limit was 4.3 CFU/mL using purified DNA from bacterial culture and 10(3) CFU/g using DNA from stool specimens. Twenty (8.3%, 20/242) C. jejuni strains were isolated from bacterial culture, while 41 (16.9%, 41/242) samples were found to be positive by real-time PCR. DNA sequencing of the PCR product indicated the presence of C. jejuni in the specimen. One mixed infection of C. jejuni and Salmonella was detected in one specimen and the PCR test for this specimen was positive. CONCLUSION: The sensitivity of detection of C. jejuni from stool specimens was much higher using this PCR assay than using the direct culture method.

In vitro protein expression profile of Campylobacter jejuni strain NCTC11168 by two-dimensional gel electrophoresis and mass spectrometry.

OBJECTIVE: To investigate the protein expression profiles of the major food-borne pathogen Campylobacter jejuni NCTC11168. METHODS: Membrane and soluble cellular proteins were extracted from the genome-sequenced C. jejuni strain NCTC11168. Protein expression profiles were determined using two-dimensional gel electrophoresis (2-DE). All the detected spots on the 2-DE map were subjected to matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/TOF) analysis. RESULTS: A total of 537 and 333 spots were detected from the whole cell and membrane-associated proteins of C. jejuni NCTC11168 cultured on Columbia agar medium at 42 °C by 2-DE and Coomassie Brilliant Blue staining, respectively. Analyses of whole cell and membrane-associated proteins included 399 and 133 spots, respectively, which included 182 and 53 functional proteins identified by MALDI-TOF/TOF analysis. CONCLUSION: The comprehensive expression protein profiles of C. jeuni NCTC11168 obtained in this study will be useful for elucidating the roles of these proteins in further pathogenesis investigation.

Comparative genomic analysis of gene variations of two Chinese Yersinia pestis isolates from vaccine strain EV76.

OBJECTIVE: To investigate genomic variations of two Chinese Yersinia pestis isolates that were isolated from different plague foci obtained from vaccine strain EV76 from the Yunnan province of China. METHODS: A microarray containing 12 000 probes covering the entire genome of seven Yersinia pestis and two Yersinia pseudotuberculosis strains, was used. PCR assays were performed to confirm microarray results. RESULTS: The gene variations detected included the absence of five genes related to the synthesis of betaine in both EV76 and another sequenced attenuated strain, KIM D27. Several genes related to phage-related membrane proteins were found to be absent in the Antiqua biovar Yunnan strain, 485, which was isolated from a rodent plague foci. CONCLUSION: These findings provide initial insight into the distinct strains isolated from natural foci, within their genomic context, including Yunnan Y. pestis strains. This information will be used therefore to establish subsequent comparisons of these sequences with published complete genomes of other strains.

[Polymorphism of Helicobacter pylori vacA, isolated in China].

OBJECTIVE: To understand the polymorphism of Helicobacter pylori (H. pylori) vacA alleles in China. METHODS: A total of 119 H. pylori strains were isolated from different gastro-duodenal diseases in 7 different geographic regions in China. vacA and its alleles were identified according to the length of PCR products with DNA electrophoresis. The distributions of vacA alleles were statistically analyzed. The core fragment of vacA was sequentially analyzed by software MEGA4.0. RESULTS: The alleles in vacA dominantly belonged to s1a, m2 and i1 in the tested strains. The distribution appeared to be 97.5% (116/119), 68.9% (82/119) and 91.6% (109/119), respectively. The m1b allele appeared to be 26.1% (31/119). s1b and m1a were not found. The major vacA recombination was between s1a/m2/i1 and 62.2%, followed by s1a/m1b/i1 (25.2%, 30/119). No association was found between the distribution of s1a allele and the clinical outcome, as well as the geographical regions (P > 0.05). However, the distribution of m alleles showed significant difference both among the types of disease and the geographic regions (P < 0.01). The present of i alleles did not show significant differences among disease patterns, but had significant differences between different geographic groups (P < 0.01). Three clusters were identified among these 119 isolates according to the DNA sequence of vacA. CONCLUSION: s1a/m2/i1 appeared to be the main allele in H. pylori vacA isolates from China in this study. The distribution of m alleles in vacA was correlated both to the regions and the disease patterns. The presence of i allele was associated to the regions but not the disease patterns.

Characteristics of lipo-oligosaccharide loci of Campylobacter jejuni isolates associated with Guillain-Barré Syndrome from Hebei, China.

Ganglioside mimicry by C.jejuni lipo-oligosaccharides (LOS) could induce the production of autoantibodies against gangliosides and the development of Guillain-Barré syndrome (GBS). The LOS biosynthesis region exhibits significant variation with different strains. Using PCR amplifications of genes from published LOS loci and sequencing the LOS biosynthesis loci, the eight GBS-associated C. jejuni strains from HeBei could be classified into four classes. The expression of sialylated LOS structures (class A) or non-sialylated LOS structures(class F, H and P) in the C. jejuni LOS is considered to be two different factors for the induction of GBS.

Time-series gene expression profiles in AGS cells stimulated with Helicobacter pylori.

AIM: To extend the knowledge of the dynamic interaction between Helicobacter pylori (H. pylori) and host mucosa. METHODS: A time-series cDNA microarray was performed in order to detect the temporal gene expression profiles of human gastric epithelial adenocarcinoma cells infected with H. pylori. Six time points were selected to observe the changes in the model. A differential expression profile at each time point was obtained by comparing the microarray signal value with that of 0 h. Real-time polymerase chain reaction was subsequently performed to evaluate the data quality. RESULTS: We found a diversity of gene expression patterns at different time points and identified a group of genes whose expression levels were significantly correlated with several important immune response and tumor related pathways. CONCLUSION: Early infection may trigger some important pathways and may impact the outcome of the infection.

Comparative proteomic analysis of Campylobacter jejuni cultured at 37C and 42C.

Campylobacter jejuni has the potential to thrive at 37C (e.g., in the human intestinal tract) and 42C (e.g., in the poultry intestinal tract). We aimed to determine the protein expression profiles of C. jejuni cultured at 37C and 42C in vitro by two-dimensional electrophoresis (2DE). The differentially expressed spots/proteins between C. jejuni cultured at 37C and 42C were defined when their expression differed by twofold. The differently expressed spots detected from C. jejuni cultured both on agar and in broth at 37C and 42C were subjected to protein identification by MALDI-TOF/TOF. Overall, 15 and 20 differentially expressed proteins were defined for C. jejuni cultured at the two temperatures on agar and in broth, respectively. All of the identified differentially expressed proteins could be clustered as proteins involving the metabolism, regulator system, periplasmic proteins and the major antigens of C. jejuni. In conclusion, there are subsets of proteins that are optimally expressed at 37C, which may contribute to the host adaptation and/or the pathogenicity in the human intestinal tract.

Comparative proteomic analysis of passaged Helicobacter pylori.

In order to identify the proteins associated with Helicobacter pylori colonization in mice, we used 2-dimensional gel electrophoresis (2-DE) to analyze the membrane- and soluble-cellular proteins extracted from H. pylori strain 26695 and the mouse-passaged homolog 88-3887. We defined 2- and 3-fold changes in protein expression as the threshold values for differential expression in the membrane-protein and whole-cell-protein fractions, respectively. The differentially expressed proteins were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/TOF). A total of 29 proteins, including 16 membrane- or membrane-associated proteins (13 upregulated, 3 downregulated) and 13 cellular proteins (10 upregulated, 3 downregulated) were differentially expressed between the strains 26695 and 88-3887. Among the upregulated proteins, 10 proteins had been previously shown to be associated with the mouse colonization, and 13 upregulated proteins were shown to be associated with the adaptation of H. pylori in murine hosts for the first time in this study. The identified proteins were classified as proteins related to metabolism, stress response, virulence, or adhesion. The data presented in this report indicated that there were subsets of upregulated proteins in mouse-adapted H. pylori. In particular, the adhesins, virulence factors, and stress-response proteins are likely to contribute to colonization in mice.

Genetic analysis of group A streptococcus isolates recovered during acute glomerulonephritis outbreaks in Guizhou Province of China.

In this study, 68 group A streptococcus (GAS) isolates associated with two outbreaks of acute glomerulonephritis (AGN) in China were analyzed by emm typing. A total of 11 different emm types were identified. Analysis of emm type distribution suggested that AGN outbreaks in two counties were caused by emm60.1- and emm63.0-type GAS. These two types were further characterized by pulsed-field gel electrophoresis, multilocus sequence typing, sof sequence typing, and PCR-based identification of streptococcal pyrogenic exotoxin A, B, and C (speA, speB, and speC) genes. In antimicrobial susceptibility tests, all outbreak strains were resistant to erythromycin and tetracycline, and the rates of resistance of nonoutbreak strains to the two antibiotics were 63.6% and 90.9%. This study is also the first to report a nephritogenic M63 GAS strain.

[Multi-PCR identification and virulence genes detection of Campylobacter jejuni isolated from China].

OBJECTIVE: This study was to simultaneously identify Campylobacter jejuni and Campylobacter coli isolates in China by Multi-PCR assay and to study the prevalence of six virulence and toxin genes on them. METHODS: A multi-PCR method with three sets of primers specifically designed for application of a 16S rRNA as a universal control, mapA, ceuE based on the specific sequence of C. jejuni and C. coli, was applied to detect 65 Campylobacter isolates from China. Another two separately PCR Primers were directed towards the hippuricase gene (hipO) characteristic of C.jejuni and glyA gene characteristic of C. coli were performed for further confirmation. The presence of the cadF, virB11, flaA, cdtA, cdtB, cdtC genes among these 65 strains were investigated by PCR. RESULTS: From multi-PCR detection, 42 isolates belonged to C. jejuni, other 23 isolates belong to C. coli. Data showing the identification were 100% in concordance with the separated PCR for hipO and glyA amplification. The efficiency (100%) of identification by these three primers multi-PCR method was higher than the biochemical test (83.1%). The cadF and flaA genes were detected from 100% (65/65) of the isolates and the PCR product of each gene were identical with each isolate. Only 10.8% (7/65) of the isolates were positive for virB11. The cdtA gene was found in 92% (60/65) of the isolates. 97.6% (41/42) of C. jejuni had cdtB gene, whereas no PCR product with this primers for all the C. coli isolates. cdtC was presented in all the isolates but the lengths of PCR products were different. For C. jejuni, it was 555 bp, for C. coli, it was about 465 bp. CONCLUSION: This three primers simultaneous multi-PCR method seemed to be useful for the identification of C. jejuni and C. coli isolates from China since cadF and flaA genes were widely spread in Campylobacter isolates in this country. The present report on virB11 was similar to previous reports from other countries, but the distribution of cdt gene cluster in Campylobacter species isolated from China might be different.

Cross-reactivity of anti-H pylori antibodies with membrane antigens of human erythrocytes.

AIM: To investigate whether anti-H pylori antibodies have cross-reaction with antigens of erythrocyte membrane. METHODS: Blood samples were collected from 14 volunteers (8 positive and 6 negative for H pylori detected by (13)C-urea breath test) of the general population. Erythrocyte membrane proteins of the subjects were examined by Western blot using anti-H pylori serum. The proteins related to the positive bands were identified by mass spectrum analysis. RESULTS: Anti-H pylori antibodies had cross-reaction with the proteins of about 50 kDa of erythrocyte membranes in all samples independent of H pylori infection. One protein in the positive band was identified as Chain S, the crystal structure of the cytoplasmic domain of human erythrocyte Band-3 protein. CONCLUSION: Anti-H pylori antibodies cross-react with some antigens of human erythrocyte membrane, which may provide a clue for the relationship between H pylori infection and vascular disorders.