25 October 2022, Volume 17 Issue 5

    

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  Functional study on the genome maintenance of Mycolicibacterium smegmatis MSMEG_4259

  JOURNAL OF MICROBES AND INFECTIONS. 2022, 17(5): 273-281.

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  MSMEG_4259 and its homologs are widely present in Mycobacterium, and protein sequence analysis revealed that MSMEG_4259 contains a DEDDh 3'-5' exonuclease domain as well as a GIY-YIG domain of nucleotide excision repair endonucleases UvrC, suggesting its possible involvement in DNA replication or repair. To investigate the physiological function of MSMEG_4259, MSMEG_4259 knockout strain were generated in Mycolicibacterium smegmatis using a homologous recombination method. We measured the growth curves of the wild type and the knockout strains and found no difference, suggesting that MSMEG_4259 is not an essential gene for growth of Mycolicibacterium smegmatis in eutrophic culture conditions. We measured the mutation frequencies of rifamycin-resistant mutation in these strains during the logarithmic growth phase as well as after H2O2 treatment by using a fluctuation test. The results showed that, during the logarithmic growth period, the mutation frequencies in the MSMEG_4259 knockout strains were increased 1.9-fold (P<0.05) compared to that of the wild type. The mutator phenotype of knockout strain was able to be complemented by expression of the wild-type MSMEG_4259. After H2O2 treatment, the mutation frequencies of the wild type and ΔMSMEG_4259 were elevated 3.7- and 2-fold (P<0.001) compared to untreated. These results showed that MSMEG_4259 is involved in the maintenance of genome stability. The results of real-time fluorescence quantitative PCR (qRT-PCR) showed that the transcription of MSMEG_4259 was upregulated 7-fold in wild type upon H2O2 treatment, suggesting that MSMEG_4259 may be involved in the response to DNA oxidative damage. We measured the survival of wild strain and ΔMSMEG_4259 under treatment with ofloxacin, tert-butyl hydrogen peroxide and UV and found that MSMEG_4259 was not involved in the tolerance of Mycolicibacterium smegmatis to these DNA damaging agents. This study reveals the physiological functions of MSMEG_4259 in Mycolicibacterium smegmatis and lays the foundation for further studies on the role of its homolog in the pathogenesis and drug resistance of Mycobacterium tuberculosis.
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  Fusobacterium nucleatum promotes the development of colorectal carcinoma by targeting lncRNA NEAT1

  JOURNAL OF MICROBES AND INFECTIONS. 2022, 17(5): 282-289.

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  The aim of this study was to investigate the effects of Fusobacterium nucleatum (F. nucleatum) on proliferation and apoptosis of human colorectal cancer (CRC) cells as well as its mechanism. Human CRC cells HCT116 at logarithmic growth stage were divided into control group, F. nucleatum group (infected with F. nucleatum), si-NEAT1 group (transfected with si-NEAT1) and F. nucleatum+si-NEAT1 group (infected with F. nucleatum after transfection with si-NEAT1). qRT-PCR was used to measure the level of RNA in cells. CCK-8 assay was performed to detect the proliferation of cells, while flow cytometry was used to calculate the apoptosis rate of cells. The expression levels of apoptosis related proteins caspase-3, Bcl-2 and Bax were determined by western blot. The proliferation of cells was enhanced, and the apoptosis rate of cells was downregulated. The expressions of caspase-3 and Bax were decreased, while the level of Bcl-2 was lifted. In addition, the expression of NEAT1 in CRC cells increased after infection with F. nucleatum. After transfection with si-NEAT1, the proliferation ability of CRC cells was decreased, the apoptosis rate was increased, and the expressions of caspase-3 and Bax protein were added, while the expression of Bcl-2 was reduced. Knockdown NEAT1 expression reversed the effect of F. nucleatum on proliferation and apoptosis of CRC cells. These results suggested that F. nucleatum could promote the proliferation and inhibit the apoptosis of CRC cells by up-regulating of NEAT1.
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  Study on the correlation between exoU gene expression in Pseudomonas aeruginosa and lasI gene deletion and drug resistance

  zhang jieli

  JOURNAL OF MICROBES AND INFECTIONS. 2022, 17(5): 290-296.

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  Abstract: Objective: To investigate the correlation between exoU gene expression in Pseudomonas aeruginosa and lasI gene deletion and drug resistance. Methods: 640 strains of Pseudomonas aeruginosa (PA) were collected and isolated in our hospital from January 2020 to December 2020, and PCR was used to detect the distribution of exoU virulence genes from different sources of strains, and fluorescence quantitative PCR technology was used to observe the expression of transcriptional regulation related gene exoU and the expression of lasI gene and downstream virulence genes in the strain; The agar dilution method was used to detect the sensitivity of antimicrobial drugs; And Pearson correlation was used to analyze the relationship between the relative expression of each gene. Results: The distribution of 640 PA specimens was mainly sputum (51.56%), blood (22.19%) and pus (14.69%). The exoS+/exoU- gene combination has the highest detection rate in PA samples from all sources, and its detection rates in sputum, blood and pus are 56.97% (188/330), 71.83% (102/142) and 67.01, respectively %(65/97); drug sensitivity results show that 640 strains of PA are resistant to 8 kinds of antibacterial drugs to varying degrees, and the sputum-derived PA strain is more resistant to imipenem than blood, pus and other sources Strain (P<0.001). PA carrying exoU gene has a higher resistance rate to imipenem, aminoglycosides, fluoroquinolones, and macrolide antibacterials (P<0.001); PA carrying exoS gene has a higher resistance to aztreonam Resistance (P<0.05); The resistance of PA with lasI gene deletion to various antibacterial drugs was significantly reduced (P<0.001), and there was a significant negative correlation between the relative expression of the transcriptional regulation-related gene ptrA of the PA strain carrying the exoU gene and exsA and the effector gene exoU (r=-0.645, P<0.001; r=-0.587, P<0.001); There was also a significant negative correlation between the relative expression of the transcriptional regulation-related gene ptrA of the PA strain carrying exoS gene and exsA and the effector gene exoS (r=-0.618, P<0.001; r=-0.532, P<0.001). After lasI gene deletion, the expression levels of downstream virulence genes lasA and aprX decreased significantly (P <0.001), and there was a significant positive correlation between the expression levels of lasA and aprX and the relative expression of lasI gene (r=0.489, P < 0.001; r=0.512, P <0.001). Conclusion: There is a significant correlation between the expression of exoU gene and the drug resistance of Pseudomonas aeruginosa. The expression of virulence genes such as exoU and drug resistance may be related to the negative regulatory gene ptrA; The deletion of the lasI gene will significantly inhibit the expression of virulence genes in the QS system of Pseudomonas aeruginosa and the drug resistance of the bacteria.
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  Effect of SopE on stability of advanced Salmonella-containing vacuole (SCV)

  Yiwei Weng

  JOURNAL OF MICROBES AND INFECTIONS. 2022, 17(5): 297-304.

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  To study the effect of SopE, a type III secretory system effector encoded by Salmonella enterica serovar Typhi, on SCV induced by S. Typhi after invasion of macrophages. S.Typhi GIFU1007was used as the wild type (WT) strain to construct the sopE mutant (ΔsopE) by homologous recombination using the suicide plasmid pGMB151. The ΔsopE complementary strain (C-ΔsopE) was constructed with the plasmid complementary method by using pBAD33.The recombinant plasmid pET28-SFGFP was introduced into the WT, ΔsopE and C-ΔsopE , respectively, to yield WT/pBAD33::pET28-SFGFP, ΔsopE/pBAD33::pET28-SFGFP and C-ΔsopE/pET28-SFGFP. The effect of SopE on the intracellular viability of S. Typhi was studied by THP-1 intracellular viability assay of macrophages. The effect of SopE on the stability of late SCV was investigated by immunofluorescence and real-time quantitative PCR (qRT-PCR). The relationship between SopE and autophagy was further investigated by qRT-PCR and Western blot. The intracellular viability of THP-1 macrophages with ΔsopE/pBAD33::PET28-SFGFP was significantly lower than that of WT/pBAD33::PET28-SFGFP and C-ΔsopE/PET28-SFGFP. The immunofluorescence assay and qRT-PCR results showed that deletion of sopE decreased the stability of late SCV. The qRT-PCR and Western blot results showed that SopE inhibited the expression of autophagy related genes. The data presented here showed that SopE regulated the stability of late SCV by affecting autophagy.
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  Epidemiological analysis, molecular typing and virulence gene analysis of Salmonella in Ningde area

  Yun-Juan PENG

  JOURNAL OF MICROBES AND INFECTIONS. 2022, 17(5): 305-311.

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  Abstract Objective To analyze the epidemiological characteristics, molecular typing and virulence genes of Salmonella in Ningde area. Methods 364 Salmonella strains were isolated in Ningde area from 2015 to 2020. The epidemiological data was given statistical analysis, and we isolate and identify the strains after culture, use pulse field gel electrophoresis (PFGE) for molecular typing analysis, and use routine PCR to detect virulence genes. Results The results of epidemiological analysis showed that the infection rate of Salmonella in men was significantly higher than that in women (P<0.05), and the infection rate in the 0~10 age group was significantly higher than that in other age groups (P<0.05). A total of 22 serotypes were isolated. Among them, Salmonella typhimurium,Salmonella enteritidis,Salmonella Stanley were the top three serotypes, accounting for 57.42%,16.21%,6.87%, respectively, which were the main serotypes.The results of PFGE typing showed that 364 strains of Salmonella had 212 bands, the similarity of bands was 44.52%~100.00%, and the dominant bands were B53 with 23 strains.The results of virulence gene test showed that the carrying rate of avrA、ssaQ、sodC1、mgtC、gipA was 100.00%, and that of ssiD、spoE、spoB was 90.66%,94.23% and 92.03%, and that of spvC was 63.74%, respectively. Conclusion Salmonella infection in Ningde area is mostly concentrated in children under 10 years of age, and men have high incidence, have certain genetic diversity, and the carrying rate of virulence genes is high. Attention should be paid to this.
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  Bacteremia caused by Lactobacillus salivarius in a gastric cancer patient with liver metastasis

  LiJun NI guo jian

  JOURNAL OF MICROBES AND INFECTIONS. 2022, 17(5): 312-316.

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  Objective To report a rare case of bacteremia caused by Lactobacillus salivarius in gastric cancer patient with liver metastasis, and to discuss the risk of opportunistic infection caused by Lactobacillus salivarius. Methods The diagnosis and treatment of bloodstream infection in this patient were retrospectively analyzed. VITEK 2 compact automatic bacterial analyzer and Antu autof ms1000 automatic microbial mass spectrometry detection system were compared, and 16S rRNA sequencing was also used to identify the strains. TDR ANA-AST was used for drug sensitivity test to provide clinical medication guidance. Results Three bottles of blood culture were positive in 2-3 days after operation. Gram positive bacilli were detected by direct smear and colonoscopy. The strains was identified as Lactobacillus acidophilus by VITEK 2 compact. Antu biological Autof ms1000 automatic microbial mass spectrometry detection system and 16S rRNA sequencing were all identified the strains as Lactobacillus salivarius. After using imipenem for anti infection treatment, the blood culture was negative. Conclusion Lactobacillus salivarius was isolated from the blood culture of a gastric cancer patient with liver metastasis in Shanghai East Hospital. The drug sensitivity test provides guidance for clinical drug use.
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  Research on antifungal activity of natural products

  JOURNAL OF MICROBES AND INFECTIONS. 2022, 17(5): 317-326.

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  The incidence of invasive fungal infections has increased year by year. However, the current antifungal drugs are scarce and the development of new drugs is relatively slow. Therefore, it is urgent to develop new antifungal drugs. Natural products have the characteristics of wide sources and low side effects. They are one of the sources of antifungal drugs. A large number of studies have proved that many compounds isolated from plants and traditional Chinese medicine have antifungal activities, and the antifungal mechanisms are different. This review discusses the latest progress in development of natural products antifungal drugs, investigates the natural products with potential antifungal activity, and puts forward the prospect of the development of new antifungal candidate drugs.
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  Interaction between oral microbiota and gut microbiota

  Qiao-Yun LIAO Qi-Feng Gui

  JOURNAL OF MICROBES AND INFECTIONS. 2022, 17(5): 327-332.

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  Oral and gut microbiota are important components of microbiota system, there is a close relationship between them. In recent years, the interaction between them has become a research hotspot. Combined with the recent research progress, this paper systematically introduces the interaction between them in the state of health and the interaction changes in the state of disease, so as to provide new enlightenment for diagnosis and treatment.
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  Results and influencing factors of inter-university learning in Medical Microbiology in the era of Internet

  JOURNAL OF MICROBES AND INFECTIONS. 2022, 17(5): 333-336.

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  Abstract： Dalian Medical University, as the course organizer, recorded the course of Medical Microbiology and published it on the Internet platform. Dalian University, as the user, cooperates with Dalian Medical University for inter-university learning. Up to now, a total of 345 students from the five years of Medical Examination majors have registered for use. In order to summarize the influencing factors and rectify shortcomings, we designed corresponding questionnaires. A total of 227 questionnaires were distributed in the classes of 2016-18, and 226 valid ones were collected, with an effective rate of 99.6%. According to the results of the questionnaire, the overall satisfaction degree of inter-university learning was 82.2%. Students also set higher demands on our teaching, such as timely communication, strengthening interaction and so on. Through the investigation, we summarized the experience and found the deficiency. With continuous improvement, the students' satisfaction has increased year by year. Inter-university learning through Internet can share the high-quality teaching resources and teachers, as well as be beneficial to students' independent study, which may be the direction of future development.