ABSTRACT
Objective:To study the molecular phylogeny and virulence gene profile of Francisella salimarina. Methods:Phylogenetic analysis of Francisella salimarina was performed based on the global genome data of related Francisella species on GenBank database. The consistency in phylogenetic analysis based on single marker genes (such as 16S rRNA gene, rpoB gene and mdh gene) and the core genome as compared. Virulence genes and antibiotic resistance genes were annotated using the virulence factor database (VFDB) and the Comprehensive Antibiotic Resistance Database (CARD), respectively. The virulence of Francisella salimarina was analyzed with a Galleria mellonella (greater wax moth) infection model using Francisella philomiragia ATCC 25015 T as reference strain. Results:The phylogenetic analysis revealed that Francisella salimarina was closely related to Francisella philomiragia. The phylogenetic tree based on mdh gene was highly similar to that based on the core genome. Francisella salimarina could be differentiated from other related species by 16S rRNA gene or mdh gene, with the latter being more accurate. Eight Francisella salimarina strains carried multiple virulence genes, mainly involved in secretion, adhesion, immune regulation, motility and stress survival. Moreover, beta-lactam resistance gene blaFPH was identified in all eight strains. Francisella salimarina showed high lethality in the Galleria mellonella infection model, which was similar to Francisella philomiragia ATCC 25015 T. Conclusions:Francisella salimarina was a rare pathogen with similar pathogenicity to Francisella philomiragia. The mdh gene could be used as a molecular target for rapid identification of Francisella salimarina.
ABSTRACT
ObjectiveTo observe the ultrastructural changes of Chlamydia trachomatis after treatment with azithromycin.Methods The Chlamydia trachomatis laboratory strain (D/UW-3/Cx) was cultured in McCoy cells with or without the presence of azithromycin of 0.0667,0.1340,0.1900,0.2680 and 0.3330 mg/L for 48 hours.The ultrastructural changes of host cells andChlamydia trachomatis were observed by transmission electron microscopy.ResultsAfter 48-hour culture,vesicles increased in number both inside and outside of the inclusion bodies with the rise in azithromycin concentration; there were abnormally large reticulate bodies,some of which experienced abnormal division and even necrosis or breakdown; the number of elementary bodies was decreased,while their size was enlarged,with a more wrinkled outer membrane.No inclusionbodieswereseenwhentheconcentrationofazithromycinwas0.333mg/L. Conclusions Azithromycin can induce an increment in the outer membrane of Chlamydia trachomatis,formation of vesicles,abnormal enlargement or breakdown of reticulate bodies,and a decrease in elementary bodies.