Background: Selective serotonin reuptaker inhibitors, including fluoxetine, are widely studied and prescribed antidepressants, while their exact molecular and cellular mechanism are yet to be defined. We investigated the involvement of HDAC1 and eEF2 in the antidepressant mechanisms of fluoxetine using a lipopolysaccharide (LPS)-induced depression-like behavior model. Methods: For in vivo analysis, mice were treated with LPS (2 mg/kg BW), fluoxetine (20 mg/kg BW), HDAC1 activator (Exifone: 54 mg/kg BW) and NH125 (1 mg/kg BW). Depressive-like behaviors were confirmed via behavior tests including OFT, FST, SPT, and TST. Cytokines were measured by ELISA while Iba-1 and GFAP expression were determined by immunofluorescence. Further, the desired gene expression was measured by immunoblotting. For in vitro analysis, BV2 cell lines were cultured; treated with LPS, exifone, and fluoxetine; collected; and analyzed. Results: Mice treated with LPS displayed depression-like behaviors, pronounced neuroinflammation, increased HDAC1 expression, and reduced eEF2 activity, as accompanied by altered synaptogenic factors including BDNF, SNAP25, and PSD95. Fluoxetine treatment exhibited antidepressant effects and ameliorated the molecular changes induced by LPS. Exifone, a selective HDAC1 activator, reversed the antidepressant and anti-inflammatory effects of fluoxetine both in vivo and in vitro, supporting a causing role of HDAC1 in neuroinflammation allied depression. Further molecular mechanisms underlying HDAC1 were explored with NH125, an eEF2K inhibitor, whose treatment reduced immobility time, altered pro-inflammatory cytokines, and NLRP3 expression. Moreover, NH125 treatment enhanced eEF2 and GSK3β activities, BDNF, SNAP25, and PSD95 expression, but had no effects on HDAC1. Conclusions: Our results showed that the antidepressant effects of fluoxetine may involve HDAC1-eEF2 related neuroinflammation and synaptogenesis.

This study investigated the characteristics and mechanisms of eravacycline resistance and heteroresistance in clinical Klebsiella pneumoniae isolates. A total of 393 clinical K. pneumoniae isolates...

Enterococcus faecalis biofilm traits and distribution characteristics in China have not been clarified. This study aimed to determine the prevalence and characteristics of E. faecalis biofilm formation in a sample of clinical isolates and to explore the virulence factors associated with biofilm formation in those isolates. A total of 265 E. faecalis isolates were collected from patients in Shenzhen, China. Virulence genes were detected within the genomes of the microbes by polymerase chain reaction (PCR). The isolates were subjected to multilocus sequence typing (MLST) based on housekeeping genes. Biofilms were detected by crystal violet staining. The expression levels of the clinical E. faecalis isolates’ genes were determined by quantitative real-time polymerase chain reaction. The prevalence of biofilm formation among E. faecalis clinical isolates was 47.2%. MLST yielded 44 different sequence types (STs). The main STs were ST16 and ST179; the ST16 isolates were more likely to form strong or medium biofilm than the ST179 isolates (p < 0.001). Strong or medium biofilm formation was more common in linezolid-resistant isolates than in linezolid-sensitive isolates (p = 0.001). Biofilm formation was more frequently detected in enterococcal surface protein (esp+), surface aggregating protein (asa1+), cytolysin A (cylA+), or aggregation substance (agg+) positive isolates than in isolates that were negative (−) for these virulence factors. Multivariate regression analysis indicated that cylA [odds ratio (OR) 4.083, p < 0.001] was a risk factor for weak biofilm formation, and that esp (OR 8.207, p < 0.001) was a risk factor for strong or medium biofilm formation. The expression of cylA was raised (4.02 to 6.00-fold) in weak biofilm isolates compared to the biofilm-negative isolates, and the expression of esp was greatly elevated (11.39 to 134.08-fold) in strong biofilm isolates compared to biofilm-negative isolates. In conclusion, the ST16 classification and linezolid resistance were positively associated with strong/medium biofilm formation in clinical E. faecalis isolates. cylA was associated with weak biofilm formation, and esp was only associated with strong or medium biofilm formation of the clinical E. faecalis isolates.

Purpose. This study explored the prevalence and characteristics of Enterococcus faecalis biofilm formation by urinary tract infection (UTI) isolates in order to identify virulence factors associated with biofilm formation. Methodology. A total of 113 E. faecalis isolates were collected from UTI patients in Shenzhen, China. The isolates were subjected to multilocus sequence typing based on housekeeping genes. Biofilms were detected by crystal violet staining and the expression levels of the E. faecalis genes were detected by quantitative real-time PCR. Results/Key findings. The main sequence types (STs) were ST16 and ST179 with the ST16 isolates more likely to form strong biofilms than the ST179 isolates (P=0.008). Strong biofilm formation was more frequently detected in aggregation substance (agg)-positive (+) isolates than in negative (−) isolates (P=0.033). Biofilm formation was also more common in isolates containing enterococcal surface protein (esp), or cytolysin A (cylA)-positive (+) isolates than in isolates negative (−) for these virulence factors. Multivariate regression analysis indicated that cylA [odds ratio (OR), 7.143, P=0.012] was associated with weak biofilm formation, and that agg (OR, 4.471, P=0.004) was associated with strong biofilm formation. The expression of cylA was increased (8.75- to 23.05-fold) in weak biofilm, and the expression of agg was greatly elevated (11.99- to 439.10-fold) in strong biofilm isolates when compared to biofilm-negative isolates. Conclusion. ST16 classification was positively associated with strong biofilm formation in E. faecalis as was agg, while cylA was associated with weak biofilm formation.

Multidrug-resistant hypervirulent Klebsiella pneumoniae (MDR-hvKP) has been increasingly reported and is now recognized as a significant threat to public health; however, characterization of MDR-hvKP has not been systematically investigated. In the present study, 124 of 428 (28.92%) K. pneumoniae clinical isolates collected from January 2010 to December 2016 were identified with aerobactin and defined as hvKP; these included 79 (48.77%) non-MDR-KP, 35 (15.63%) extended spectrum β-lactamase-producing K. pneumoniae (ESBL-KP), and 10 (23.81%) carbapenem-resistant K. pneumoniae (CR-KP) isolates. The remaining 304 isolates that were not hypervirulent phenotypes were defined as classic K. pneumoniae (cKP). The antimicrobial resistance rate of cKP was significantly higher than that of the hvKP isolates in the non-MDR-KP group, but showed no significant differences in the ESBL-KP and CR-KP groups. The detection frequencies of K1 serotype, hypermucoviscosity, sequence type 23 (ST23), and two virulence genes—mucoviscosity-associated gene A (magA) and regulator of mucoid phenotype A (rmpA)—were significantly high in the hvKP than cKP isolates in all three groups (P < 0.05). Most of the hypervirulent ESBL-KP and CR-KP isolates were K non-typeable (28/45) and harbored at least one gene for virulence (36/45). The hypervirulent ESBL-KP isolates primarily carried blaSHV (25/35, 71.42%) genes, and the hypervirulent CR-KP isolates mainly carried blaNDM-1 (8/10, 80%) genes. Moreover, four hypervirulent ESBL-KP and two hypervirulent CR-KP isolates showed resistance to tigecycline. The transcriptional levels of rmpA in cKP were much lower than that in hvKP isolates in all three groups. Furthermore, overexpression of rmpA could partly restore the hypervirulent phenotype of the rmpA-low-expression cKP isolates. In conclusion, our data suggest that the K1 serotype, rmpA, magA, hypermucoviscosity, and ST23 were strongly associated with hvKP in non-MDR-KP, ESBL-KP, and CR-KP groups, and low rmpA expression levels contributed to the absence of hypervirulent phenotype.