Real-time PCR Platform Research Articles

Evaluating HPV Viral Load and Multiple Infections for Enhanced Cervical Cancer Risk-Based Assessment

Human papillomavirus (HPV) is a major cause of cervical cancer, a significant health concern worldwide. Despite advances in screening methods, including the Pap test and the HPV DNA test, limitations remain in accurately predicting which HPV infections will progress to cervical intraepithelial neoplasia (CIN) and, eventually, invasive cancer. This study evaluates the usefulness in real life of assessing HPV viral load and the presence of multiple HPV genotypes in enhancing the diagnostic accuracy of triage in cervical cancer screening. A retrospective analysis was performed on 55 formalin-fixed paraffin-embedded cervical samples collected from women who underwent colposcopy with a biopsy or conization at San Martino Hospital, Genova, Italy, between January and June 2021. Histological diagnoses were compared with molecular analyses (HPV genotyping, viral load quantification and co-infection) using a multiplex real-time PCR platform. Of the samples analyzed, 56.4% were HPV DNA positive, while 40% tested negative. The molecular analysis identified more HPV-negative cases than the histological analysis (p < 0.05). Higher viral loads and HPV co-infections were more frequent in high-grade CIN lesions. These markers may help identify patients at an elevated risk for persistent infections and cancer progression. These findings support the potential of integrating HPV viral load and genotype co-infection assessments into routine cervical cancer screening protocols to improve early detection and reduce overtreatment and unnecessary interventions.

A new quantitative real-time PCR method to measure human miRNAs using the PROMER technology

MicroRNAs (miRNAs) are small, non-coding RNA molecules that play a crucial role in regulating gene expression. Dysregulation of miRNAs is associated with various human diseases, including cancer. Accurate quantification of miRNAs in bodily fluids or tissue biopsy samples is essential for their use as biomarkers in tumor diagnosis, yet current methods remain suboptimal. In this study, we introduce a novel quantitative real-time PCR platform based on PROMER technology, which relies on RNA:DNA perfect matching in the primer-template interaction, followed by RNAse H2 cleavage to generate a 3'-hydroxyl group for new DNA synthesis. We selected 16 miRNAs implicated in lung cancer and evaluated the specificity and performance of the platform using synthesized miRNA mimics. Each miRNA could be measured with high specificity and accuracy, even at copy numbers as low as 1-10, while non-template controls exhibited minimal amplification. Additionally, key miRNAs involved in tumor progression, such as miR-210, miR-331, and miR-505, were accurately quantified using minimal amounts of plasma. In summary, we present a new quantitative real-time PCR method for miRNA detection using PROMER technology. This platform successfully measured miRNA mimics and was further applied to quantify miRNA species in plasma samples from cancer patients. Our findings support the potential clinical application of this method for early cancer diagnosis using liquid biopsy samples.

Development of a new tool to detect Melampsora medusae f.sp. tremuloidae causing rust disease on Populus tremuloides.

Melampsora medusae f. sp. tremuloidae is a quarantine organism for the EU. In North America, this fungus causes rust disease on Populus tremuloides. In Europe, Populus tremula, an aspen closely related to P. tremuloides, is widespread and plays an important ecological role. Introduction of M. medusae f. sp. tremuloidae into Europe could be a major risk if this forma specialis could evolve and become virulent on P. tremula. To date no PCR-based assay exists to specifically detect M. medusae f. sp. tremuloidae. In this study, a sensitive and specific real-time PCR assay has been developed based on the 28S rDNA. The assay proved to be reliable using many real-time PCR kits and platforms. It can be used to monitor the introduction and the spread of M. medusae f. sp. tremuloidae in the context of phytosanitary regulations.

A multiplexed real‐time PCR assay for simultaneous quantification of human immunodeficiency virus and Hepatitis B virus for low‐and‐middle‐ income countries

Due to shared routes of transmission, including sexual contact and vertical transmission, HIV-HBV co-infection is common, particularly in sub-Saharan Africa. Measurement of viral load (VL), for both HIV and HBV, plays a critical role for determining their infectious phase and monitoring response to antiviral therapy. Implementation of viral load testing in clinical settings is a significant challenge in resource-limited countries, notably because of cost and availability issues. We designed HIV and HBV primers for conserved regions of the HIV and HBV genomes that were specifically adapted to viral strains circulating in West Africa that are HIV-1 subtype CRF02AG and HBV genotype E. We first validated two monoplex qPCR assays for individual quantification and, then developed a multiplex qPCR for simultaneous quantification of both viruses. HIV RNA and HBV DNA amplification was performed in a single tube using a one-step reverse transcription-PCR reaction with primers and probes targeting both viruses. Performance characteristics such as the quantification range, sensitivity, and specificity of this multiplex qPCR assay were compared to reference qPCR tests for both HIV and HBV viral load quantification. The multiplex assay was validated using clinical samples from co- or mono-infected patients and gave comparable viral load quantification to the HIV and HBV reference test respectively. The multiplex qPCR demonstrated an overall sensitivity of 71.25 % [68.16-74.3] for HBV and 82 % [78.09-85.90] for HIV and an overall specificity of 100 % [94.95-100] for both viruses. Although the overall sensitivities of the HIV and HBV assays were lower than the commercial comparator assays, the sensitivity in the clinical decision range of >1000 copies/mL for HIV was 80 % [71.26-88.73] and >1000 IU/mL for HBV was 100 % [95.51-100] which indicates the test results can be used to guide treatment decisions. This in-house developed multiplex qPCR assay represents a useful diagnostic tool as it can be performed on affordable "open" real-time PCR platforms currently used for HIV or SARS-Cov-2 infection surveillance in Mali.

Cytology Smears can be Effectively Used on Two Different Fully Automated Real-Time PCR Platforms That Have Been Validated for Use Only with FFPE Tissue

Cytology Smears can be Effectively Used on Two Different Fully Automated Real-Time PCR Platforms That Have Been Validated for Use Only with FFPE Tissue

Development of an event-specific PCR method to quantify genetically modified soybean DBN8002 on both real-time and digital PCR platforms

Development of an event-specific PCR method to quantify genetically modified soybean DBN8002 on both real-time and digital PCR platforms

Comparison of microbiological and molecular diagnosis for identification of respiratory secondary infections in COVID-19 patients and their antimicrobial resistance patterns

We report the use of a new multiplex Real-Time PCR platform to simultaneously identify 24 pathogens and 3 antimicrobial-resistance genes directly from respiratory samples of COVID-19 patients. Results were compared to culture-based diagnosis. Secondary infections were detected in 60% of COVID-19 patients by molecular analysis and 73% by microbiological assays, with no significant differences in accuracy, indicating Gram-negative bacteria as the predominant species. Among fungal superinfections, Aspergillus spp. were detected by both methods in more than 7% of COVID-19 patients. Oxacillin-resistant S. aureus and carbapenem-resistant K. pneumoniae were highlighted by both methods. Secondary microbial infections in SARS-CoV-2 patients are associated with poor outcomes and an increased risk of death. Since PCR-based tests significantly reduce the turnaround time to 4 hours and 30 minutes (compared to 48 hours for microbial culture), we strongly support the routine use of molecular techniques, in conjunction with microbiological analysis, to identify co/secondary infections.

Advancing public health preparedness: Establishment of Nipah virus molecular diagnostic test at the National Reference Laboratory, Sri Lanka

Objective: To establish Nipah virus diagnostic capabilities at the National Reference Laboratory in Sri Lanka using the NIV Pune real-time PCR kit. Methods: Strict safety precautions were adhered during testing due to the high pathogenicity of the Nipah virus, with all diagnostics conducted in a BSL2+ laboratory at the Medical Research Institute in Sri Lanka. RNA extraction was performed using the QIAamp Viral RNA Mini kit. The NIV Pune in-house real-time PCR kit was employed, following established primer/probe sequences and controls. The assay was validated using the Rotor-Gene Q Series Real-time PCR platform. Results: The validation run of the Nipah virus real-time PCR test demonstrated robust performance, with positive controls consistently detecting Nipah RNA at a Ct value of 21.50±0.01. Negative controls confirmed assay specificity with an external negative control which was also used as an extraction control and showed no interference. The internal control exhibited stable behavior, enhancing confidence in PCR results. The qPCR analysis graph illustrated the successful detection of internal and positive controls, validating the reliability of the assay. Conclusions: Establishing Nipah virus diagnostic capabilities in Sri Lanka signifies a proactive and collaborative response to the persistent global health threat.

A novel molecular assay conducted on the BD Max system to facilitate reflex testing for vanA and vanB in clinical isolates of enterococci

Infections caused by vancomycin-resistant enterococci (VRE) are common. Real-time PCR assays targeting vanA and vanB facilitate screening of patients in healthcare settings to limit the risk of dissemination, especially amongst those at high-risk of infection or with limited treatment options. Such assays are commonly performed as reflex testing procedures where they augment phenotypic techniques and shorten turnaround time to benefit timely clinical management. 'Random access' and 'sample-to-result' real-time PCR platforms are suited for this application as they are of low complexity and less technically demanding. Modelled on these attributes, we configured a real-time PCR assay (VRE BD) for detection of vanA/B in clinical isolates of enterococci, adapted for the BD Max System (Becton Dickinson). We applied an unconventional approach by testing suspensions of microorganisms in water to circumvent the traditional pre-analytical genomic extraction process. Our objective of this study was to assess the performance of this assay for detection of VRE in cultures by validating against a traditional real-time PCR assay based on the LightCycler 2.0 platform (Roche, VRE RO). A high level of analytical sensitivity and specificity (≥99.0%) for both genes was obtained when testing suspensions derived from blood agar. Results for suspensions obtained from chromID VRE (Edwards Group) showed a similar level of performance for vanA detection (100%), but not for the vanB target (≥90.9%) where a lesser number of isolates were available for testing. However, our results for VRE detection in isolates from these media were repeatable and reproducible, and equated to positive and negative predictive values of ≥95.2% and ≥97.8%, respectively. Furthermore, the VRE BD assay was also able to accurately detect VRE in clinical and spiked BacT/ALERT (bioMérieux) blood cultures. Thus, the technical simplicity, short turnaround time and robustness of this high performing assay for VRE is suitable for reflex testing. In addition, the format developed for the BD Max platform has potential application for reflex testing other molecular targets of clinical importance.

RHC genotyping in Chinese Han population

BackgroundThe Rh blood group system is characterized by its complexity and polymorphism, encompassing 56 different antigens. Accurately predicting the presence of the C antigen using genotyping methods has been challenging. The objective of this study was to evaluate the accuracy of various genotyping methods for predicting the Rh C and to identify a suitable method for the Chinese Han population.MethodsIn total, 317 donors, consisting 223 D+ (including 20 with the Del phenotype) and 94 D− were randomly selected. For RHC genotyping, 48C and 109bp insertion were detected on the Real-time PCR platform and −292 substitution was analyzed via restriction fragment length polymorphism (RFLP). Moreover, the promoter region of the RHCE gene was sequenced to search for other nucleotide substitutions between RHC and RHc. Agreement between prediction methods was evaluated using the Kappa statistic, and comparisons between methods were conducted via the χ2 test.ResultsThe analysis revealed that the 48C allele, 109bp insertion, a specific pattern observed in RFLP results, and wild-type alleles of seven single nucleotide polymorphisms (SNPs) were in strong agreement with the Rh C, with Kappa coefficients exceeding 0.8. However, there were instances of false positives or false negatives (0.6% false negative rate for 109bp insertion and 5.4-8.2% false positive rates for other methods). The 109bp insertion method exhibited the highest accuracy in predicting the Rh C, at 99.4%, compared to other methods (P values≤0.001). Although no statistical differences were found among other methods for predicting Rh C (P values>0.05), the accuracies in descending order were 48C (94.6%) > rs586178 (92.7%) > rs4649082, rs2375313, rs2281179, rs2072933, rs2072932, and RFLP (92.4%) > rs2072931 (91.8%).ConclusionsNone of the methods examined can independently and accurately predict the Rh C. However, the 109bp insertion test demonstrated the highest accuracy for predicting the Rh C in the Chinese Han population. Utilizing the 109bp insertion test in combination with other methods may enhance the accuracy of Rh C prediction.

Real-time PCR primers and probes for the detection of Shiga toxin genes, including novel subtypes

Shiga toxin-producing Escherichia coli (STEC) are foodborne enteric pathogens. STEC are differentiated from other E. coli by detection of Shiga toxin (Stx) or its gene (stx). The established nomenclature of Stx identifies ten subtypes (Stx1a, Stx1c, Stxd, Stx2a to Stx2g). An additional nine subtypes have been reported and described (Stx1e, Stx2h to Stx2o). Many PCR protocols only detect a subset of Stx subtypes which limits their inclusivity. Here we describe a real-time PCR assay inclusive of the DNA sequences of representatives of all currently described Stx subtypes. A multiplex real-time PCR assay for detection of stx was developed using nine primers and four probes. Since the identification of STEC does not require differentiation of stx subtypes, the probes use the same fluorescent reporter to enable detection of multiple possible targets in a single reaction. The PCR mixture includes an internal positive control to detect inhibition of the reaction. Thus, the protocol can be performed on a two-channel real-time PCR platform. To reduce the biosafety risk inherent in the use of STEC cultures as process controls, the protocol also includes the option of a non-pathogenic E. coli transformant carrying a plasmid encoding the targeted fragment of the stx2a sequence. The inclusivity of the PCR was assessed against colonies of 137 STEC strains and one strain of Shigella dysenteriae, including strains carrying single copies of stx representing fourteen subtypes (stx1 a, c, d; stx2 a-j and o). Five additional subtypes (stx1e, 2k, 2l, 2m and 2n) were represented by E. coli transformed with plasmids encoding toxoid (enzymatically inactive A subunit) sequences. The exclusivity panel consisted of 70 bacteria, including 21 stx-negative E. coli. Suitability for food analysis was assessed with artificially inoculated ground beef, spinach, cheese, and apple cider. The real-time PCR generated positive results for all 19 stx subtypes, represented by colonies of STEC, S. dysenteriae and E. coli transformants carrying stx toxoid plasmids. Tests of exclusivity panel colonies were all negative. The real-time PCR detected the presence of stx in all inoculated food enrichments tested, and the presence of STEC was confirmed by isolation.

Microfluidics-based EGFR mutation detection and its implication in the resource-limited clinical setting.

Management of lung cancer today obligates a mutational analysis of the epidermal growth factor receptor (EGFR) gene particularly when Tyrosine Kinase Inhibitor (TKI) therapy is being considered as part of prognostic stratification. This study evaluates the performance of automated microfluidics-based EGFR mutation detection and its significance in clinical diagnostic settings. Formalin-fixed, paraffin-embedded (FFPE) samples from NSCLC patients (n = 174) were included in a two-phase study. Phase I: Validation of the platform by comparing the results with conventional real-time PCR and next-generation sequencing (NGS) platform. Phase II: EGFR mutation detection on microfluidics-based platform as part of routine diagnostics workup. The microfluidics-based platform demonstrates 96.5% and 89.2% concordance with conventional real-time PCR and NGS, respectively. The system efficiently detects mutations across the EGFR gene with 88.23% sensitivity and 100% specificity. Out of 144 samples analysed in phase II, the platform generated valid results in 94% with mutation detected in 41% of samples. This microfluidics-based platform can detect as low as 5% mutant allele fractions from the FFPE samples. Therefore the microfluidics-based platform is a rapid, complete walkaway, with minimum tissue requirement (two sections of 5 μ thickness) and technical skill requirement. The method can detect clinically actionable EGFR mutations efficiently and can be considered a reliable diagnostic platform in resource-limited settings. From receiving samples to reporting the results this platform provides accurate data without much manual intervention. The study helped to devise an algorithm that emphasizes effective screening of the NSCLC cases for EGFR mutations with varying tumour content. Thus it helps in triaging the cases judiciously before proceeding with multigene testing.

Real-time PCR detection of PI*S and PI*Z alleles of SERPINA1 gene using SYBR green

Alpha-1 antitrypsin deficiency is an underdiagnosed genetic condition that predisposes to pulmonary complications and is mainly caused by rs28929474 (PI*Z allele) and rs17580 (PI*S allele) mutations in the SERPINA1 gene. Development of a homogeneous genotyping test for detection of PI*S and PI*Z alleles based on the principles of allele-specific PCR and amplicon melting analysis with a fluorescent dye. Sixty individuals, which included all possible genotypes that result from combinations of rs28929474 and rs17580 single nucleotide variants, were assayed with tailed allele-specific primers and SYBR Green dye in a real-time PCR machine. A clear discrimination of mutant and wild-type variants was achieved in the genetic loci that define PI*S and PI*Z alleles. Specific amplicons showed a difference of 2.0°C in melting temperature for non-S and S variants and of 2.9°C for non-Z and Z variants. The developed genotyping method is robust, fast, and easily scalable on a standard real-time PCR platform. While it overcomes the handicaps of non-homogeneous approaches, it greatly reduces genotyping costs compared with other homogeneous approaches.

Development of an ultrafast PCR to detect clinically relevant acquired vancomycin-resistance genes from cultured enterococci.

VRE are increasingly described worldwide. Screening of hospitalized patients at risk for VRE carriage is mandatory to control their dissemination. Here, we have developed the Bfast [VRE Panel] PCR kit, a rapid and reliable quantitative PCR assay for detection of vanA, vanB, vanD and vanM genes, from solid and liquid cultures adaptable to classical and ultrafast real-time PCR platforms. Validation was carried out on 133 well characterized bacterial strains, including 108 enterococci of which 64 were VRE. Analytical performances were determined on the CFX96 Touch (Bio-Rad) and Chronos Dx (BforCure), an ultrafast qPCR machine. Widely used culture plates and broths for enterococci selection/growth were tested. All targeted van alleles (A, B, D and M) were correctly detected without cross-reactivity with other van genes (C, E, G, L and N) and no interference with the different routinely used culture media. A specificity and sensitivity of 100% and 99.7%, respectively, were determined, with limits of detection ranging from 21 to 238 cfu/reaction depending on the targets. The Bfast [VRE Panel] PCR kit worked equally well on the CFX and Chronos Dx platforms, with differences in multiplexing capacities (five and four optical channels, respectively) and in turnaround time (45 and 16 minutes, respectively). The Bfast [VRE Panel] PCR kit is robust, easy to use, rapid and easily implementable in clinical microbiology laboratories for ultra-rapid confirmation of the four main acquired van genes. Its features, especially on Chronos Dx, seem to be unmatched compared to other tools for screening of VRE.

Validation of a new extraction-free real-time PCR test to detect MPOX virus

The monkeypox (Mpox) virus has raised significant concerns given its recent spread with an increasing number of confirmed cases worldwide. In this study, we evaluated the performance of a laboratory developed test (LDT) using BioGX Xfree hMPXV/OPXV reagents for the qualitative detection of non-variola Orthopoxviruses and Mpox virus DNA, in swabs from human pustular or vesicular rash specimens. Analytical and clinical testing analysis were carried out on two different platforms: the BD MAX™ System (BD Diagnostics) and the new pixl.16 Real-Time PCR Platform (BioGX), using a synthetic Mpox virus DNA (ATCC VR-3270SD) and residual clinical samples previously identified with an EUA approved Mpox real-time PCR assay. In the end, the Xfree hMPXV/OPXV LDT proved to be a sensitive, specific, and reproducible test for the detection of Mpox on both platforms evaluated with the pixl.16 having an advantage of a small footprint and providing faster TAT facilitated by an extraction-free workflow.

High-throughput screening of transient receptor potential (TRP) channels in pterygium.

Pterygium is a hyaline degenerative disease of the conjunctiva characterized by the progression of fibrovascular connective tissue from the bulbar conjunctiva to the cornea. The mechanism of pterygium formation is still not fully understood. Transient receptor potential (TRP) channels are a group of ion channels with distinct characteristics. Recent indications suggest TRP channels may play a significant regulatory role in pterygium development, but previous studies have mainly focused on in silico analysis. Accordingly, in the present study, we aimed to decipher the expression signatures and role of TRP channels in pterygium development. The study encompassed a cohort of 45 patients matched for age and gender distribution, comprising 30 individuals with primary pterygium (PP) and 15 individuals with recurrent pterygium(RP). The control group consisted of unaffected conjunctival tissue obtained from the same set of patients. High-throughput screening of differentially expressed TRP channels in pterygium tissues was achieved with the help of Fluidigm 96.96 Dynamic Array Expression Chip and reactions were held in BioMark™ HD System Real-Time PCR platform. Statistically significant increases were found in the expression of 21 genes, mainly TRPA1 (p = 0.021), TRPC2 (p = 0.001), and TRPM8 (p = 0.003), in patients with PP, and in TRPC5 (p = 0.05), TRPM2 (p = 0.029), TRPM4 (p = 0.03), TRPM6 (p = 0.045), TRPM8 (p = 0.038), TRPV1 (p = 0.01) and TRPV4 (p = 0.025) genes in RP tissues. Collectively, TRP channel proteins appear to play pivotal roles in both the development and progression of pterygium, making them promising candidates for future therapeutic interventions in patients afflicted by this condition.

Investigation of Polymorphisms in Global Genome Repair Genes in Patients With Ovarian Cancer in the Turkish Population.

Ovarian cancer (OC) poses significant challenges due to its high mortality rate, particularly in advanced stages where symptoms may not be evident. DNA repair mechanisms, including nucleotide excision repair (NER), are crucial in maintaining genomic stability and preventing cancer. This study focuses on exploring the role of two NER-related genes, Xeroderma Pigmentosum Complementation Group C (XPC) and DNA Damage Binding Protein 2 (DDB2), in OC susceptibility. This study aims to investigate the association between variations in two NER-related genes, XPC rs2228001 and DDB2 rs830083, among a cohort of Turkish individuals with OC and control subjects. Genotyping of XPC rs2228001 and DDB2 rs830083 was performed on 103 OC patients and 104 control subjects from the Turkish population using the Fast Real-Time 7500 PCR platform from Applied Biosystems. Individuals with the homozygous AA genotype of XPC rs2228001 exhibited a reduced likelihood of developing OC (OR 0.511; 95% CI 0.261 - 1.003; P-value 0.049), whereas those with the CC variant faced an elevated risk (OR = 2.32, 95% CI = 1.75-3.08; P-value 0.035). The presence of the A allele was associated with decreased OC occurrence (P-value = 0.035). Similarly, for DDB2 rs830083, individuals with the homozygous CG genotype had a diminished risk of OC (P-value 0.036), compared to those with the GG polymorphism (OR 1.895; 95% CI 1.033 - 3.476; P-value 0.038). Furthermore, the presence of the C allele was associated with a 1.89-fold decrease in the likelihood of OC. These findings shed light on the genetic factors influencing OC susceptibility, emphasizing the importance of DNA repair systems in disease. Further research in larger and more diverse populations is warranted to validate these findings, facilitating precise risk assessment, and potentially guiding tailored treatment strategies for OC patients.

Improving the efficiency of Y-chromosome detection and the quality of STR typing in forensic casework with an in-house made qPCR and HRM system based on SYTO™ 9 chemistry

To evaluate the correlation between the quantification results obtained with the previously developed Amel-Y system, and its ability to detect Y-chromosome DNA by HRM, with the resulting STR profiles, and to ultimately show that Amel-Y can be routinely used in forensic casework to improve STR and Y-STR results. Biological samples derived from forensic casework (85 reference and 391 evidence samples) were quantified by the Amel-Y system (a duplex qPCR/HRM based on SYTO™ 9 chemistry) using Rotor-Gene 6000. STRs were amplified and analyzed with GeneAmp™ PCR System 9700 or Veriti™ Thermal Cyclers and ABI 3500 Genetic Analyzer, respectively. After DNA normalization, a total of 386 STR profiles were obtained (305 full and 81 partial). Sex typing by HRM was 100% successful in reference samples. Male DNA was detected by HRM in 210 evidence samples. 80/201 were mixed with an excess of female DNA. In addition, Amel-Y was able to detect Y-chromosome DNA in mixed samples that did not amplify the Y-variant of Amelogenin marker with commercial STR kits. The reproducibility and precision of the Amel-Y system were demonstrated (CVCt% ≤ 9.55) within the dynamic range analyzed (0.016-50ng/µL; 41 independent runs). Amel-Y also proved to be compatible with other real-time PCR platforms. We demonstrated that Amel-Y is a robust quantification system that can be routinely used in forensic casework to obtain reliable autosomal STR profiles and can be suitable as a predictor for Y-STR typing success when male DNA is detected. HRM can be used as a rapid screening tool for male DNA detection in mixed samples. Alternative designs like Amel-Y offer independence from commercial quantification kits in forensic labs.

Perturbation of Quorum Sensing after the Acquisition of Bacteriophage Resistance Could Contribute to Novel Traits in Vibrio alginolyticus.

Bacteria employ a wide range of molecular mechanisms to confer resistance to bacteriophages, and these mechanisms are continuously being discovered and characterized. However, there are instances where certain bacterial species, despite lacking these known mechanisms, can still develop bacteriophage resistance through intricate metabolic adaptation strategies, potentially involving mutations in transcriptional regulators or phage receptors. Vibrio species have been particularly useful for studying the orchestrated metabolic responses of Gram-negative marine bacteria in various challenges. In a previous study, we demonstrated that Vibrio alginolyticus downregulates the expression of specific receptors and transporters in its membrane, which may enable the bacterium to evade infection by lytic bacteriophages. In our current study, our objective was to explore how the development of bacteriophage resistance in Vibrio species disrupts the quorum-sensing cascade, subsequently affecting bacterial physiology and metabolic capacity. Using a real-time quantitative PCR (rt-QPCR) platform, we examined the expression pattern of quorum-sensing genes, auto-inducer biosynthesis genes, and cell density regulatory proteins in phage-resistant strains. Our results revealed that bacteriophage-resistant bacteria downregulate the expression of quorum-sensing regulatory proteins, such as LuxM, LuxN, and LuxP. This downregulation attenuates the normal perception of quorum-sensing peptides and subsequently diminishes the expression of cell density regulatory proteins, including LuxU, aphA, and LuxR. These findings align with the diverse phenotypic traits observed in the phage-resistant strains, such as altered biofilm formation, reduced planktonic growth, and reduced virulence. Moreover, the transcriptional depletion of aphA, the master regulator associated with low cell density, was linked to the downregulation of genes related to virulence. This phenomenon appears to be phage-specific, suggesting a finely tuned metabolic adaptation driven by phage-host interaction. These findings contribute to our understanding of the role of Vibrio species in microbial marine ecology and highlight the complex interplay between phage resistance, quorum sensing, and bacterial physiology.

Development of a Real-Time PCR Assay for the Detection and Identification of Rubus Stunt Phytoplasma in Rubus spp.

Rubus stunt, caused by 'Candidatus Phytoplasma rubi' (Rubus stunt phytoplasma; RSP), is an economically important disease of Rubus. This disease occurs in wild and cultivated Rubus spp. in Europe but has not been reported from North America; however, its major leafhopper vector is well established in western Canada and the U.S.A. RSP has the potential to impact the cane-fruit industry by significantly compromising yields and impacting export potential for Rubus propagation material. To mitigate the risk of this disease entering or establishing, import and export testing of propagation material is a phytosanitary requirement in Canada, the U.S.A., and other countries regulating RSP. In the absence of a specific test for RSP, the current testing scheme involves the use of a generic test to screen for phytoplasmas followed by additional time-consuming procedures to confirm the phytoplasma species. In this study, a real-time PCR assay, targeting a 154-bp region of tuf gene, was developed for sensitive and specific detection of RSP in Rubus spp. The developed assay detected a minimum of five target copies, and no cross-reactivity was observed even with the 'Ca. P. rubi'-related strain associated with blackberry witches' broom, which differs from RSP only by a single nucleotide polymorphism in the target region. Repeatability of the developed assay was checked on two real-time PCR platforms with acceptable results. In conclusion, this real-time PCR assay provides a sensitive and specific detection of RSP for mitigating the introduction and spread of Rubus stunt disease in Rubus spp.