The small RNA PrrH aggravates Pseudomonas aeruginosa-induced acute lung injury by regulating the type III secretion system activator ExsA.

Pseudomonas aeruginosa is an opportunistic pathogen that causes acute and chronic infections in immunocompromised individuals. Small regulatory RNAs (sRNAs) regulate multiple bacterial adaptations to environmental changes, especially virulence. Our previous study showed that sRNA PrrH negatively regulates the expression of a number of virulence factors, such as pyocyanin, rhamnolipid, biofilm, and elastase in the P. aeruginosa strain PAO1. However, previous studies have shown that the prrH-deficient mutant attenuates virulence in an acute murine lung infection model. All ΔprrH-infected mice survived the entire 28-day course of the experiment, whereas all mice inoculated with the wild-type or the complemented mutant succumbed to lung infection within 4 days of injection, but the specific mechanism is unclear. Herein, we explored how PrrH mediates severe lung injury by regulating the expression of virulence factors. In vivo mouse and in vitro cellular assays demonstrated that PrrH enhanced the pathogenicity of PAO1, causing severe lung injury. Mechanistically, PrrH binds to the coding sequence region of the mRNA of exsA, which encodes the type III secretion system master regulatory protein. We further demonstrated that PrrH mediates a severe inflammatory response and exacerbates the apoptosis of A549 cells. Overall, our results revealed that PrrH positively regulates ExsA, enhances the pathogenicity of P. aeruginosa, and causes severe lung injury. IMPORTANCE: Pseudomonas aeruginosa is a Gram-negative bacterium and the leading cause of nosocomial pneumonia. The pathogenicity of P. aeruginosa is due to the secretion of many virulence factors. Small regulatory RNAs (sRNAs) regulate various bacterial adaptations, especially virulence. Therefore, understanding the mechanism by which sRNAs regulate virulence is necessary for understanding the pathogenicity of P. aeruginosa and the treatment of the related disease. In this study, we demonstrated that PrrH enhances the pathogenicity of P. aeruginosa by binding to the coding sequence regions of the ExsA, the master regulatory protein of type III secretion system, causing severe lung injury and exacerbating the inflammatory response and apoptosis. These findings revealed that PrrH is a crucial molecule that positively regulates ExsA. Type III-positive strains are often associated with a high mortality rate in P. aeruginosa infections in clinical practice. Therefore, this discovery may provide a new target for treating P. aeruginosa infections, especially type III-positive strains.

The effects of LL-37 on virulence factors related to the quorum sensing system of Pseudomonas aeruginosa.

Background: Antimicrobial peptides (AMPs) have shown promise in the treatment of multi-resistant pathogens. It was therefore of interest to analyze the effects of the AMP LL-37 on the regulation of several virulence factors related to the quorum sensing (QS) system of Pseudomonas aeruginosa (P. aeruginosa) in vitro. Methods: The minimum inhibitory concentration (MIC) was evaluated by the micro broth dilution method. The expression of QS-related and QS-regulated virulence factor genes was also evaluated. Exotoxin A activity was measured with the nicotinamide adenine dinucleotide (NAD) (Coenzyme I) method; Elastase activity was detected with the elastin-Congo red (ECR) method; Pyocyanin detection was performed using the chloroform extraction method. The effects of LL-37 were assessed by measuring the expression changes of the virulence protein-encoding genes of the strains with quantitative polymerase chain reaction (PCR). Results: The MIC of LL-37 against both P. aeruginosa reference strain (ATCC 15692 PAO1) and PA-ΔlasI/rhII was therefore determined to be 256 µg/mL. LL-37 at sub-minimum inhibitory concentrations (sub-MICs) had no significant effects on P. aeruginosa bacterial growth (P>0.05), but significantly downregulated the expression of all 3 virulence factors. Conclusions: Interestingly, this effect appeared to be dose-related. These findings suggest that LL-37 could be a potential candidate for QS inhibition against bacterial infection and may have significant clinical potential in the treatment of P. aeruginosa biofilms.

Evaluation of humoral pattern detection performance of Mindray BC-6000PLUS blood analyzer based on WS/T 662-2020.

BACKGROUND: Manual microscopic examination is the gold standard of humoral cell count test. However, it has some limitations and cannot fully meet clinical needs. Compared with the manual method, the automatic blood cell analyzer has the advantages of a high degree of automation, minimal error, high speed, high precision, and easy standardization. This study intends to verify the detection performance of the body fluid model of the Mindray BC-6000PLUS automatic hematology analyzer. METHODS: This study was performed in accordance with the International Committee for Standardization in Haematology (ICSH) Hematology Analyzer Evaluation Guide (version 2014) and the requirements of WS/T662-2020 "Clinical humoral examination technique". The humoral white blood cell-body fluid (WBC-BF), humoral red blood cell-body fluid (RBC-BF), monocyte (MN), polymorphonuclear (PMN) were measured to verify the performance indicators of the instrument, including background counting, intra-batch precision, accuracy, carrying contamination rate, and linear range. Referring to the WS/T514-2017 (Establishment and verification of detection capability for clinical laboratory measurement procedures), the limit of blank (LoB) and limit of detection (LoD) values of WBC-BF and RBC-BF in the humoral mode of the instrument were established. RESULTS: The blank count of WBC-BF and RBC-BF, and contamination of Mindray BC-6000PLUS analyzer were zero; the coefficient of variation (CV) of intra-batch precision at different levels of each item was less than 10%. There was a high correlation between instrument test results and manual microscopic examination results (r>0.95). The linear range of the instrument was wide, and the linear verification parameters was good (R2>0.999). The LoB value and LoD value of WBC-BF established by the instrument were 0×109/L and 0.004×109/L, respectively. The LoB value and LoD value of the RBC-BF established by the instrument were 0×1012/L and 0.004×1012/L, respectively. The lower detection limits of WBC-BF and RBC-BF were set as 0.004×109/L and 0.004×1012/L, respectively. CONCLUSIONS: All performance indicators of the Mindray BC-6000PLUS automatic blood analyzer met the requirements of the manufacturer's criteria. This instrument can fulfill the requirement of body fluid sample routine test in clinical practice.

Identification of a novel RhlI/R-PrrH-LasI/Phzc/PhzD signalling cascade and its implication in P. aeruginosa virulence.

Small regulatory RNAs (sRNAs) act as key regulators in many bacterial signalling cascades. However, in P. aeruginosa, the sRNAs involved in quorum sensing (QS) regulation and their function are still largely unknown. Here, we explored how the prrH locus sRNA influences P. aeruginosa virulence in the context of the QS regulatory network. First, gain- and loss-of-function studies showed that PrrH affects pyocyanin, elastase and rhamnolipid production; biofilm formation; and swimming and swarming motility and impaired the viability of P. aeruginosa in human whole blood. Next, our investigation disclosed that LasI and PhzC/D were directly repressed by PrrH. In addition, RhlI, the key member of the rhl QS system, diminished the expression of PrrH and enhanced the expression of downstream genes. Bioinformatics analysis found two binding sites of RhlR, the transcription factor of the rhl system, on the promoter region of prrH. Further ß-galactosidase reporter and qPCR assays confirmed that PrrH was transcriptionally repressed by RhlR. Collectively, our data identified a novel RhlI/R-PrrH-LasI/PhzC/PhzD regulatory circuitry that may contribute to P. aeruginosa pathogenesis. Our findings indicate that PrrH is a quorum regulatory RNA (Qrr) in P. aeruginosa and provide new insight into PrrH's function.

The standardization of the report for urine cell counting-A converting factor for Sysmex UF-1000i.

BACKGROUND: Multicenter laboratory may apply both automated flow cytometer and microscopy for urinalysis. Automated flow cytometer such as Sysmex UF-1000i evaluates particles with native urine without centrifugation and reports as "counts per µL." Microscopic examination recommended as the reference method for urine sediment analysis reports results as "counts per HPF (or µL)." Moreover, some results from flow cytometer are needed to be checked visually under microscopy. Therefore, it is worth to establish the consistency of the results from these two methods. METHODS: Urine specimens from 412 patients were examined with Sysmex UF-1000i and manual microscopy using FAST-READ disposable counting chambers. White blood cell (WBC) and red blood cell (RBC) counting results from UF-1000i after transferred with the converting factor (0.297) we estimated were compared with that from microscopic examination. Method comparison was performed using Passing-Bablok analysis. RESULTS: After transferred with the converting factor (0.297), cell counting results from UF-1000i showed a good correlation with that derived by the reference method (R2 was 0.868 for RBCs (P < 0.001), 0.882 for WBCs (P < 0.001)). Passing-Bablok analysis showed no systematic difference (intercept estimate, -1 [95%CI, -7 to 3] and slightly proportional (slope estimate, 1.2 [95%CI, 1.0 to 1.7]) bias between concentrations of cells measured by manual microscopy and Sysmex UF-1000i using the converting factor. CONCLUSION: The converting factor (0.297) helps to transfer "counts per µL (non-centrifugal urine)" to "counts per µL (equal to centrifugal urine)," and to keep the urine particle analysis results of Sysmex UF-1000i consistent with the results from the reference method.