Differential expression of urease genes and ureolytic activity of uropathogenic Escherichia coli and Pseudomonas aeruginosa isolates in different nutritional conditions

Urological metabolic conditions alter regulation of quorum-sensing system and virulence genes expression in uropathogenic Pseudomonasaeruginosa

Pseudomonas aeruginosa (P. aeruginosa) is responsible for complicated urinary tract infections (UTI) acquired from different transmission routes. Quorum sensing (QS) plays an important role in the regulation of virulence factors in P. aeruginosa and is dependent on the nutritional conditions. Under pathological conditions, urine contains elevated levels of metabolites such as glucose, creatinine, albumin and haem that may alter the QS behavior in P. aeruginosa. Hence, we investigated the role of the QS system in P. aeruginosa on growth and the expression of virulence genes under altered urinary metabolic compositions. We used P. aeruginosa strains isolated from UTI patients, along with PAO1 as a reference strain and grown under simulated metabolic conditions in the synthetic urine. Growth, biofilm formation, motility, siderophore production, rhamnolipid secretion, pyocyanin production, elastase and urease activity were quantified using standard laboratory methods. The expression levels of QS genes, such as lasI/R, rhlI/R, and pqsA/R, alginate synthesis genes (algD/R), the motility-regulating gene (pilA), and urease gene (ureC), were estimated using qRT-PCR for comparison between the growth conditions. The results showed significant differences in growth, biofilm formation and virulence factors between the metabolic conditions and were significantly higher (p<0.001) in simulated glycosuria, haematuria, and creatininuria conditions compared to the control. Under albuminuria, significantly reduced growth and virulence factor production were observed. Compared to control, higher expression levels of lasI/R, rhlI/R, pqsA/R, algD/R, pilA and ureC genes were observed in all conditions except albuminuria. The results highlighted the overexpression of QS-regulating genes and virulence in strains from similar metabolic environments in patients, suggesting possible niche adaptation. Such adaptation may pose considerable challenge in the management of chronic P. aeruginosa infections in urinary tract.

The roles of bacteria on urolithiasis progression and associated compounds

As a common urological disease, the formation of urinary tract stones involves multiple factors, including genetics, the environment, dietary habits, and bacterial species (e.g., Proteus mirabilis and Escherichia coli). Previous studies have demonstrated that P. mirabilis primarily contributes to infectious urinary calculus formation by producing urease, an enzyme that breaks down urea into ammonia and carbon dioxide, thereby altering the urinary pH and promoting crystal formation and growth. In contrast, calcium oxalate (CaOx) stones are the main type of kidney stones, and the most common bacteria in CaOx stones are E. coli. Intriguingly, E. coli can also facilitate stone formation via flagellin and other virulence factors, which induce renal epithelial cell injury and increase crystal adhesion and aggregation. These bacteria play complex and multidimensional roles in the formation of urinary tract stones, necessitating further research to elucidate their underlying mechanisms. Here, we summarise the roles of common urinary tract bacteria, particularly P. mirabilis and E. coli, in forming urinary tract stones, aiming to enhance our understanding of urolithiasis exploration in the future.

Four new species of Pichia (Pichiales, Pichiaceae) isolated from China

The genus Pichia belonging to the family Pichiaceae is widely distributed worldwide and has garnered significant attention due to its importance in various industries and its potential role in human infections. During our investigation of yeast diversity in China, several strains representing undescribed taxa were isolated from forests in Hainan province, Hubei province, Beijing city and a mudflat in Guangdong province. Based on phylogenetic analyses of the internal transcribed spacer (ITS) region and the D1/D2 domain of the large subunit (LSU) rRNA, these strains were identified as four new species: Pichiakregeriana sp. nov. (holotype strain CGMCC 2.7383T), P.phaffii sp. nov. (holotype strain CGMCC 2.8239T), P.ureolytica sp. nov. (holotype strain CGMCC 2.6825T) and P.wuzhishanensis f.a. sp. nov. (holotype strain CGMCC 2.7381T). The six strains of P.ureolytica were identified as positive for urease production. This phenomenon is extremely rare in the genus Pichia, as only P.bovicola is reported to exhibit weak urease activity.

Multidrug resistance in Pseudomonas aeruginosa: genetic control mechanisms and therapeutic advances

Pseudomonas aeruginosa is a significant opportunistic pathogen, and its complex mechanisms of antibiotic resistance pose a challenge to modern medicine. This literature review explores the advancements made from 1979 to 2024 in understanding the regulatory networks of antibiotic resistance genes in Pseudomonas aeruginosa, with a particular focus on the molecular underpinnings of these resistance mechanisms. The review highlights four main pathways involved in drug resistance: reducing outer membrane permeability, enhancing active efflux systems, producing antibiotic-inactivating enzymes, and forming biofilms. These pathways are intricately regulated by a combination of genetic regulation, transcriptional regulators, two-component signal transduction, DNA methylation, and small RNA molecules. Through an in-depth analysis and synthesis of existing literature, we identify key regulatory elements mexT, ampR, and argR as potential targets for novel antimicrobial strategies. A profound understanding of the core control nodes of drug resistance offers a new perspective for therapeutic intervention, suggesting that modulating these elements could potentially reverse resistance and restore bacterial susceptibility to antibiotics. The review looks forward to future research directions, proposing the use of gene editing and systems biology to further understand resistance mechanisms and to develop effective antimicrobial strategies against Pseudomonas aeruginosa. This review is expected to provide innovative solutions to the problem of drug resistance in infectious diseases.