Simultaneous detection of Clavibacter michiganensis subsp. nebraskensis and Pantoea stewartii subsp. stewartii based on microsphere immunoreaction

Clavibacter nebraskensis causing Goss's wilt of maize: Five decades of detaining the enemy in the New World

Goss's bacterial wilt and leaf blight of maize (Zea mays) caused by the gram-positive coryneform bacterium Clavibacter nebraskensis is an economically important disease in North America. C. nebraskensis is included within the high-risk list of quarantine pathogens by several plant protection organizations (EPPO code: CORBMI), hence it is under strict quarantine control around the world. The causal agent was reported for the first time on maize in Nebraska (USA) in 1969. After an outbreak during the 1970s, prevalence of the disease decreased in the 1980s to the early 2000s, before the disease resurged causing a serious threat to maize production in North America. The re-emergence of Goss's wilt in the corn belt of the United States led to several novel achievements in understanding the pathogen biology and disease control. In this review, we provide an updated overview of the pathogen taxonomy, biology, and epidemiology as well as management strategies of Goss's wilt disease. First, a taxonomic history of the pathogen is provided followed by symptomology and host range, genetic diversity, and pathogenicity mechanisms of the bacterium. Then, utility of high-throughput molecular approaches in the precise detection and identification of the pathogen and the management strategies of the disease are explained. Finally, we highlight the role of integrated pest management strategies to combat the risk of Goss's wilt in the 21st century maize industry.

DISEASE SYMPTOMS

Large (2-15 cm) tan to grey elongated oval lesions with wavy, irregular water-soaked margins on the leaves. The lesions often start at the leaf tip or are associated with wounding caused by hail or wind damage. Small (1 mm in diameter), dark, discontinuous water-soaked spots, known as "freckles", can be observed in the periphery of lesions. When backlit, the freckles appear translucent. Early infection (prior to growth stage V6) may become systemic and cause seedlings to wilt, wither, and die. Coalescence of lesions results in leaf blighting.

HOST RANGE

Maize (Zea mays) is the only economic host of the pathogen. A number of Poaceae species are reported to act as secondary hosts for C. nebraskensis.

TAXONOMIC STATUS OF THE PATHOGEN

Class: Actinobacteria; Order: Micrococcales; Family: Microbacteriaceae; Genus: Clavibacter; Species: Clavibacter nebraskensis.

SYNONYMS

Corynebacterium nebraskense (Schuster, 1970) Vidaver & Mandel 1974; Corynebacterium michiganense pv. nebraskense (Vidaver & Mandel 1974) Dye & Kemp 1977; Corynebacterium michiganense subsp. nebraskense (Vidaver & Mandel 1974) Carlson & Vidaver 1982; Clavibacter michiganense subsp. nebraskense (Vidaver & Mandel 1974) Davis et al. 1984; Clavibacter michiganensis subsp. nebraskensis (Vidaver & Mandel 1974) Davis et al. 1984.

TYPE MATERIALS

ATCC 27794^T ; CFBP 2405^T ; ICMP 3298^T ; LMG 3700^T ; NCPPB 2581^T .

MICROBIOLOGICAL PROPERTIES

Cells are gram-positive, orange-pigmented, pleomorphic club- or rod-shaped, nonspore-forming, nonmotile, and without flagella, approximately 0.5 × 1-2.0 μm.

DISTRIBUTION

The pathogen is restricted to Canada and the United States.

PHYTOSANITARY CATEGORIZATION

EPPO code CORBNE.

Rapid quantitative detection of Klebsiella pneumoniae in infants with severe infection disease by point-of-care immunochromatographic technique based on nanofluorescent microspheres

Background: Klebsiella pneumoniae (KP, K. pneumoniae) is one of the most important nosocomial pathogens that cause severe respiratory infections. As evolutionary high-toxic strains with drug resistance genes increase year by year, the infections caused by it are often accompanied by high mortality, which may be fatal to infants and can cause invasive infections in healthy adults. At present, the traditional clinical methods for detecting K. pneumoniae are cumbersome and time-consuming, and the accuracy and sensitivity are not high. In this study, nanofluorescent microsphere (nFM)-based immunochromatographic test strip (ICTS) quantitative testing platform were developed for point-of-care testing (POCT) method of K. pneumoniae. Methods: 19 clinical samples of infants were collected, the genus-specific gene of mdh was screened from K. pneumoniae. Polymerase chain reaction (PCR) combined with nFM-ICTS based on magnetic purification assay (PCR-ICTS) and strand exchange amplification (SEA) combined with nFM-ICTS based on magnetic purification assay (SEA-ICTS) were developed for the quantitative detection of K. pneumoniae. The sensitivity and specificity of SEA-ICTS and PCR-ICTS were demonstrated by the existing used classical microbiological methods, the real-time fluorescent quantitative PCR (RTFQ-PCR) and PCR assay based on agarose gel electrophoresis (PCR-GE). Results: Under optimum working conditions, the detection limits of PCR-GE, RTFQ-PCR, PCR-ICTS and SEA-ICTS are 7.7 × 10^-3, 2.5 × 10^-6, 7.7 × 10^-6, 2.82 × 10^-7 ng/μL, respectively. The SEA-ICTS and PCR-ICTS assays can quickly identify K. pneumoniae, and could specifically distinguish K. pneumoniae samples from non-K. pneumoniae samples. Experiments have shown a diagnostic agreement of 100% between immunochromatographic test strip methods and the traditional clinical methods on the detection of clinical samples. During the purification process, the Silicon coated magnetic nanoparticles (Si-MNPs) were used to removed false positive results effectively from the products, which showed of great screening ability. The SEA-ICTS method was developed based on PCR-ICTS, which is a more rapid (20 min), low-costed method compared with PCR-ICTS assay for the detection of K. pneumoniae in infants. Only need a cheap thermostatic water bath and takes a short detection time, this new method can potentially serve as an efficient point-of-care testing method for on-site detection of pathogens and disease outbreaks without fluorescent polymerase chain reaction instruments and professional technicians operation.

Rapid and sensitive detection of Shigella flexneri using fluorescent microspheres as label for immunochromatographic test strip

Background

Bacillary dysentery caused by Shigella genus is a major cause of morbidity and mortality worldwide. In China, the popular strain was mainly Shigella flexneri (S. flexneri). Therefore, fluorescent microspheres (FMs)-based immunochromatographic test strip (ICTS), as a novel, reliable, sensitive and uncomplicated method, was evaluated to detect S. flexneri.

Methods

Sixty-three clinical samples of S. flexneri were collected in this paper. Polymerase chain reaction (PCR) combined with FMs-ICTS based on magnetic purification assay was developed for the quantitative detection of Shigella. And the genus-specific gene of ipaH and drug resistant gene of CTX-M-9 from Shigella were selected to investigate the potential of this new method. The sensitivity and specificity of this method were demonstrated by classical microbiological methods (API Coryne System), PCR assay based on agarose gel electrophoresis (PCR-GE) and the real-time fluorescent quantitative PCR (RTFQ-PCR) method.

Results

Under optimized conditions, the lower detection limits of PCR-ICTS, PCR-GE and RTFQ-PCR were 2.5×10^-7, 2.5×10^-5 and the 3.2×10^-7 ng/µL, respectively. Experiments demonstrated the PCR-ICTS has a diagnostic agreement of 100% with conventional PCR and RTFQ-PCR on detection of clinical samples and could correctly recognize Shigella and non-Shigella from different microbial samples. After the purification of PCR products with Silicon coated magnetic nanoparticles (Si-MNPs), the false positive results were removed because of the strong screening ability of the purification process. Our results showed that FM-based ICTS was promising for measurable and sensitive detection of S. flexneri within 3 h.

Conclusions

The results from immunochromatographic test were agreement with those from API Coryne system and RTFQ-PCR. Hence, this developed method might be useful for screening and monitoring clinical sample of S. flexneri, due to its speed, non-poisonous, simplicity and low-cost and helpful for promoting the prevention and control of communicable diseases caused by enteric pathogens such as S. flexneri.

R-Phycoerythrin Induces SGC-7901 Apoptosis by Arresting Cell Cycle at S Phase

R-Phycoerythrin (R-PE), one of the chemical constituents of red algae, could produce singlet oxygen upon excitation with the appropriate radiation and possibly be used in photodynamic therapy (PDT) for cancer. Documents reported that R-PE could inhibit cell proliferation in HepG2 and A549 cells, which was significative for cancer therapy. This is due to the fact that R-PE could kill cancer cells directly as well as by PDT. However, little is known about the cytotoxicity of R-PE to the SGC-7901 cell. In this study, it has been found that R-PE could inhibit SGC-7901 proliferation and induce cell apoptosis, which was achieved by arresting the SGC-7901 cell at S phase. CyclinA, CDK2 and CDC25A are proteins associated with the S phase, and it was found that R-PE could increase the expression of cyclin A protein and decrease the expression of CDK2 and CDC25A proteins. Thus, it was concluded that R-PE reduced the CDK2 protein activated through decreasing the CDC25A factor, which reduced the formation of Cyclin-CDK complex. The reduction of Cyclin-CDK complex made the SGC-7901 cells arrest at the S phase. Therefore, R-PE induced apoptosis by arresting the SGC-7901 cell at S phase was successful, which was achieved by the expression of the CDC25A protein, which reduced the CDK2 protein actived and the formation of Cyclin-CDK complex.

Development of an immunochromatographic strip for rapid detection of Pantoea stewartii subsp. stewartii

A rapid, simple, sensitive, and specific immunochromatographic test strip was developed for the detection of Pantoea stewartii subsp. stewartii (Pss) in corn seed which was soaked overnight and then centrifuged for precipitate re-dissolved as samples. A pair of sensitive monoclonal antibodies for the immunochromatographic test strip was generated by mice immunization and cell fusion. Under optimized conditions, the lower detection limit of the strips for Pss was 1 × 10(5) cfu/mL both in 0.01 M phosphate buffer solution and corn seed samples, with no cross-reactivity with other common plant pathogens. The developed strip is useful and rapid for the detection of Pss in corn seed samples.

Dual amplified electrochemical immunosensor for highly sensitive detection of Pantoea stewartii sbusp. stewartii

Accurate and highly sensitive detection of Pantoea stewartii sbusp. stewartii-NCPPB 449 (PSS) is urgently required for international shipments due to tremendous agricultural economic losses. Herein, a dual amplified electrochemical sandwich immunosensor for PSS detection was developed, utilizing the good specificity and low cost of electrochemical immunoassay, the favorable conductivity and large specific surface area of gold nanoparticles (Au NPs), and the excellent catalytic ability of and horseradish peroxidase (HRP). A linear curve between current response and PSS concentration was established, and the limit of detection (LOD) was 7.8 × 10(3) cfu/mL, which is 20 times lower than that for conventional enzyme-linked immunosorbent assay (ELISA). This strategy is a useful approach for the highly sensitive detection of plant pathogenic bacterium.