The rapid and accurate identification of parasites is crucial for prompt therapeutic intervention in parasitosis and effective epidemiological surveillance. For accurate and effective clinical diagnosis, it is imperative to develop a nucleic-acid-based diagnostic tool that combines the sensitivity and specificity of nucleic acid amplification tests (NAATs) with the speed, cost-effectiveness, and convenience of isothermal amplification methods. A new nucleic acid detection method, utilizing the clustered regularly interspaced short palindromic repeats (CRISPR)-associated (Cas) nuclease, holds promise in point-of-care testing (POCT). CRISPR/Cas12a is presently employed for the detection of Plasmodium falciparum, Toxoplasma gondii, Schistosoma haematobium, and other parasites in blood, urine, or feces. Compared to traditional assays, the CRISPR assay has demonstrated notable advantages, including comparable sensitivity and specificity, simple observation of reaction results, easy and stable transportation conditions, and low equipment dependence. However, a common issue arises as both amplification and cis-cleavage compete in one-pot assays, leading to an extended reaction time. The use of suboptimal crRNA, light-activated crRNA, and spatial separation can potentially weaken or entirely eliminate the competition between amplification and cis-cleavage. This could lead to enhanced sensitivity and reduced reaction times in one-pot assays. Nevertheless, higher costs and complex pre-test genome extraction have hindered the popularization of CRISPR/Cas12a in POCT.

Eurytrema coelomaticum, a pancreatic fluke, is recognized as a causative agent of substantial economic losses in ruminants. This infection, commonly referred to as eurytrematosis, is a significant concern due to its detrimental impact on livestock production. However, there is a paucity of knowledge regarding the mitochondrial genome of E. coelomaticum. In this study, we performed the initial sequencing of the complete mitochondrial genome of E. coelomaticum. Our findings unveiled that the mitochondrial genome of E. coelomaticum spans a length of 15,831 bp and consists of 12 protein-coding genes, 22 tRNA genes, two rRNA genes, and two noncoding regions. The A+T content constituted 62.49% of the genome. Moreover, all 12 protein-coding genes of E. coelomaticum exhibit the same arrangement as those of E. pancreaticum and other published species belonging to the family Dicrocoeliidae. The presence of a short string of additional amino acids (approximately 20~23 aa) at the N-terminal of the cox1 protein in both E. coelomaticum and E. pancreaticum mitochondrial genomes has contributed to the elongation of the cox1 gene in genus Eurytrema, surpassing that of all previously sequenced Dicrocoeliidae. The phylogenetic analysis displayed a close relationship between E. coelomaticum and E. pancreaticum, along with a genus-level association between Eurytrema and Lyperosomum. These findings underscore the importance of mitochondrial genomic data for comparative studies of Dicrocoeliidae and even Digenea, offering valuable DNA markers for future investigations in the systematic, epidemiological, and population genetic studies of this parasite and other digenean trematodes.

Proliferation of the emerging zoonotic pathogen Streptococcus equi subsp. zooepidemicus in the meninges is linked to mortality in pigs and morbidity in humans. The mechanisms underlying the remarkable capacity of hypervirulent S. zooepidemicus to proliferate in cerebrospinal fluid (CSF) are largely undefined. Here, using genetically barcoded S. zooepidemicus , we found that following systemic infection of mice, only ~1–10 S. zooepidemicus clones invade the meninges where they subsequently replicate ~10 ⁷ -fold. Subsequent transposon insertion sequencing experiments, plus validation work with bacterial mannose phosphotransferase system (PTS _man )-defective strains, identified the PTS _man , which imports glucose, as essential for S. zooepidemicus proliferation in CSF. The S. zooepidemicus PTS _man promoter confers species-specific constitutive transcription of PTS _man , enabling glucose acquisition at low glucose concentrations and limiting activation of the stringent response, leading to pathogen replication in CSF. Our findings reveal how the rewiring of PTS _man in the control of S. zooepidemicus metabolism enables this pathogen to adapt to and replicate in CSF during meningitis.

The rapid and accurate detection of parasites is crucial for timely curative intervention in parasitosis and for epidemiological surveillance. To meet the needs of clinical diagnosis, it is imperative to develop a diagnostic tool based on nucleic acid that combines the sensitivity and specificity of established nucleic acid amplifica-tion tests with the speed, cost-effectiveness, and convenience of isothermal amplification methods. A new nu-cleic acid detection method, utilizing the clustered regularly interspaced short palindromic repeats (CRISPR)-associated (Cas) nuclease, holds promise for point-of-care testing. Specifically, the CRISPR-Cas12a system has demonstrated numerous advantages for detecting parasites, with hopeful outcomes for identify-ing malaria, toxoplasmosis, and other parasitic ailments. This review provides an overview of how CRISPR-Cas12a can be utilized for parasite detection, evaluates its advantages and disadvantages, and sug-gests ways to improve the efficiency and sensitivity of CRISPR-Cas12a-based assays.

The strict requirement for a canonical TTTV protospacer adjacent motif (PAM) restricts target-site selection in clustered regularly interspaced short palindromic repeats/CRISPR-associated protein 12a (CRISPR/Cas12a)-based diagnostics and limits the flexibility of assay design. Whether suboptimal PAMs can be effectively incorporated into one-pot detection systems for Clostridium perfringens has not been systematically examined. Here, we developed two one-pot recombinase polymerase amplification (RPA)–CRISPR/Cas12a assays targeting the plc and cpe toxin genes of C. perfringens and systematically evaluated 28 crRNAs spanning canonical (TTTV) and suboptimal (VTTV, TCTV) PAMs in both trans-cleavage and one-pot formats. Several suboptimal-PAM crRNAs, including crRNA 4 for plc (PAM: GTTG) and crRNA 7 for cpe (PAM: CTTA), maintained efficient detection in the one-pot system, whereas crRNA performance between the two formats was not predictable, underscoring the need for direct one-pot screening. The optimized assays achieved limits of detection of 50 copies (plc) and 10 copies (cpe), showed no cross-reactivity against four non-target bacterial species. The plc assay was successfully validated in pork, chicken, and beef samples spiked with C. perfringens, with results readable within 40 min using a simple isothermal device and naked-eye readout. The cpe assay was confirmed as a proof-of-concept at the genomic DNA level. These results demonstrate that suboptimal PAMs can serve as a deliberate design strategy to expand target accessibility in one-pot CRISPR/Cas12a diagnostics.