Development and evaluation of an IS711-based loop mediated isothermal amplification method (LAMP) for detection of Brucella spp. on clinical samples

Optimization and comparative analysis of LAMP and PCR techniques for the detection of leptospiral DNA in Golden Syrian hamsters

Leptospirosis is a zoonotic disease with significant public health and economic impact worldwide. Rapid and accurate diagnosis is essential for effective prevention and treatment. This study optimized a loop-mediated isothermal amplification (LAMP) assay using BFo isothermal DNA polymerase with different colorimetric indicators. LAMP was able to detect DNA from pathogenic and intermediate leptospires, while non-pathogenic leptospires and other non-leptospiral microorganisms were negative. LAMP assay combined with calcein showed a tenfold higher limit of detection (1 ng of leptospiral DNA per reaction) than LAMP combined with hydroxynaphthol blue or end-point PCR lipL32 (10 ng of DNA per reaction). Animal samples were collected from infected and non-infected Golden Syrian hamsters (Mesocricetus auratus) to evaluate and compare the performance of LAMP and PCR. These techniques showed a substantial agreement according to Cohen's kappa statistic, being both useful techniques for detecting leptospiral DNA in clinical samples. Overall, this study demonstrates that the LAMP assay is a sensitive, specific, rapid, and simple tool for the detection of leptospiral DNA. It has the potential to facilitate the diagnosis of leptospirosis, particularly in low-income regions with limited diagnosis resources.

A recombinase polymerase amplification-SYBR Green I assay for the rapid and visual detection of Brucella

Brucellosis is a zoonosis caused by Brucella, which poses a great threat to human health and animal husbandry. Pathogen surveillance is an important measure to prevent brucellosis, but the traditional method is time-consuming and not suitable for field applications. In this study, a recombinase polymerase amplification-SYBR Green I (RPAS) assay was developed for the rapid and visualized detection of Brucella in the field by targeting BCSP31 gene, a conserved marker. The method was highly specific without any cross-reactivity with other common bacteria and its detection limit was 2.14 × 104 CFU/mL or g of Brucella at 40 °C for 20 min. It obviates the need for costly instrumentation and exhibits robustness towards background interference in serum, meat, and milk samples. In summary, the RPAS assay is a rapid, visually intuitive, and user-friendly detection that is highly suitable for use in resource-limited settings. Its simplicity and ease of use enable swift on-site detection of Brucella, thereby facilitating timely implementation of preventive measures.

Development of a novel visual isothermal amplification assay for rapid detection of Brucella spp

Brucellosis is an economically important livestock disease worldwide besides having a noteworthy impact on human health. In this study, a rapid, simple, and ultra-sensitive nuclei-acid diagnostic technique was developed for the detection of brucellosis harnessing saltatory rolling circle amplification (SRCA). The diagnostic method was developed using World Organization for Animal Health (WOAH) approved primers targeting the bcsp31 gene of the Brucella genome. The assay can be accomplished within 90 min at a temperature of 65 °C without the requirement of sophisticated instrumentation. The result interpretation can be done with the naked eye with the aid of SYBR green dye. The developed technique displayed 100% specificity by amplifying only 10 reference and field strains of Brucella spp. and there was no cross-reactivity with the other tested pathogens. The lower limit of detections of SRCA and end-point PCR assays were 9.7 fg/μL (2.7 genome copies of Brucella) and 970 fg/μL, respectively. Thus, the developed SRCA assay was found to be 100× more sensitive than the end-point PCR assay. To the best of our knowledge, our study is the first one to develop an SRCA-based assay for the detection of brucellosis and it can be a diagnostic tool for resource-constrained laboratories and veterinary hospitals.

Brucella melitensis Wzm/Wzt System: Changes in the Bacterial Envelope Lead to Improved Rev1Δwzm Vaccine Properties

The lipopolysaccharide (LPS) O-polysaccharide (O-PS) is the main virulence factor in Brucella. After synthesis in the cytoplasmic membrane, O-PS is exported to the periplasm by the Wzm/Wzt system, where it is assembled into a LPS. This translocation also engages a bactoprenol carrier required for further biosynthesis pathways, such as cell wall biogenesis. Targeting O-PS export by blockage holds great potential for vaccine development, but little is known about the biological implications of each Wzm/Wzt moiety. To improve this knowledge and to elucidate its potential application as a vaccine, we constructed and studied wzm/wzt single- and double-deletion mutants, using the attenuated strain Brucella melitensis Rev1 as the parental strain. This allowed us to describe the composition of Brucella peptidoglycan for the first time. We observed that these mutants lack external O-PS yet trigger changes in genetic transcription and in phenotypic properties associated with the outer membrane and cell wall. The three mutants are highly attenuated; unexpectedly, Rev1Δwzm also excels as an immunogenic and effective vaccine against B. melitensis and Brucella ovis in mice, revealing that low persistence is not at odds with efficacy. Rev1Δwzm is attenuated in BeWo trophoblasts, does not infect mouse placentas, and is safe in pregnant ewes. Overall, these attributes and the minimal serological interference induced in sheep make Rev1Δwzm a highly promising vaccine candidate.

Detection of Haemophilus influenzae by loop-mediated isothermal amplification coupled with nanoparticle-based lateral flow biosensor assay

Background

Haemophilus influenzae was the most aggressive pathogen and formed a major cause of bacterial meningitis and pneumonia in young children and infants, which need medical emergency requiring immediate diagnosis and treatment. However, From isolation to identification of H. influenzae, the traditional diagnose strategy was time-consuming and expensive. Therefore, the establishment of a convenient, highly sensitive, and stable detection system is urgent and critical.

Results

In this study, we used a combined method to detect H. influenzae. Six specific primers were designed on the basis of outer membrane protein P6 gene sequence of H. influenzae. The reaction condition such as the optimum temperature was 65℃, and the optimum reaction time was 30 min, respectively. Through the loop-mediated isothermal amplification (LAMP) in combination with nanoparticle-based lateral flow biosensor (LFB), the sensitivity of LAMP-LFB showed 100 fg was the lowest genomic DNA templates concentration in the pure cultures. Meanwhile, the specificity of H. influenzae-LAMP-LFB assay showed the exclusive positive results, which were detected in H. influenzae templates. In 55 clinical sputum samples, 22 samples were positive with LAMP-LFB method, which was in accordance with the traditional culture and Polymerase Chain Reaction (PCR) method. The accuracy in diagnosing H. influenzae with LAMP-LFB could reach 100%, compared to culture and PCR method, indicating the LAMP-LFB had more advantages in target pathogen detection.

Conclusions

Taken together, LAMP-LFB could be used as an effective diagnostic approach for H. influenzae in the conditions of basic and clinical labs, which would allow clinicians to make better informed decisions regarding patient treatment without delay.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-022-02547-5.

Circulating Brucella species in wild animals of the Serengeti ecosystem, Tanzania

BACKGROUND

Brucellosis is a bacterial zoonosis of public health and economic importance worldwide. It affects a number of domestic animals, wild animals and humans. Human brucellosis originates from either livestock or wildlife. The species of Brucella circulating in wild animals in Tanzania is largely unknown due to insufficient surveillance. This study was carried out to identify Brucella species found in selected wildlife hosts in the Serengeti ecosystem.

METHODOLOGY

The study used a total of 189 archived samples that were obtained from cross-sectional studies previously conducted between 2000 and 2017 in the Serengeti ecosystem in Tanzania. Whole blood, serum and amniotic fluid collected from buffalos, lions, wildebeest, impala, zebra and hyena were available for DNA extraction. Multiplex polymerase chain reaction for B. abortus, B. melitensis, B. ovis and B. suis (AMOS PCR) and quantitative real-time PCR (qPCR) targeting the bcsp31 and IS711 genes for Brucella genus detection and the IS711 targets alkB for B. abortus and BMEI1162 for B. melitensis were used to detect Brucella strains.

RESULTS

Out of the 189 samples tested, 12 (6.35 %) and 22 (11.6 %) were positive to AMOS-PCR and qPCR, respectively. Most of the positive samples were from lions (52.6 %) and buffaloes (19.6 %). Other animals that were positive included: wildebeest (13.6 %), impala (13.6 %), zebra (4.5 %) and hyena (4.5 %). Out of 22 positive samples, 16 (66.7 %) were identified as B. abortus and the other six samples did not amplify for neither B. abortus nor B. melitensis.

CONCLUSIONS

The detection of Brucella DNA in archived wild animal samples shows testing potential of samples collected from this population. The zoonotic species B. abortus and B. melitensis detected in wild animals have previously been reported in livestock and humans in the region. The findings suggest that, due to the contact network, some of the identified wild animal hosts in this study could be reservoirs for infections in domestic animals and humans within the Serengeti ecosystem while others are likely dead-end hosts. One Health control strategies and continuous surveillance programs in other wildlife reserved areas should be implemented to help predicting transmission in livestock and humans in the region.

Prevalence and Spatial Distribution of Animal Brucellosis in Central Punjab, Pakistan

Brucellosis is an important zoonotic disease of animals and humans caused by bacteria of the genus Brucella. Brucellae are Gram-negative intracellular bacteria which infect a wide variety of animals including goats, sheep, buffaloes, cows, pigs, and wildlife. The objectives of this study were to determine the seroprevalence and spatial distribution of brucellosis in Central Punjab, Pakistan. A total of 1083 blood samples of goats, sheep, buffaloes, and cows were collected from 38 villages of four districts (Kasur, Faisalabad, Lahore, and Okara) of Punjab, Pakistan, and screened for brucellosis by Rose Bengal Plate test (RBPT) and PCR confirmed. Epidemiological, demographic data and GPS coordinates for every sample were collected. By using interpolation of the Aeronautical Reconnaissance Coverage Geographic Information System (Arc GIS), a surface plot was generated applying inverse distance weight (IDW). It was found that 35 (3.23%) serum samples were positive for brucellosis. In eight (61.5%), six (75%), seven (87.5%), and eight (89%) villages, positive goats, sheep, buffaloes, and cattle were detected, respectively. In general, older animals are more often positive for brucellosis. In goats bucks were more often RBPT positive than females while in sheep, buffaloes, and cattle more females were positive. The spatial distribution of brucellosis shows that it is widely distributed in the western region of the study area in goats and in the South-West region in sheep. Similarly, for buffaloes it is restricted to the south-east and north-west regions, and in cattle brucellosis is present in western region of study area only. Reflected by this study, brucellosis poses a risk for livestock in developing countries due to lack of awareness by officials, owners, and consumers, and control measures are missing. A risk map of brucellosis was generated to develop effective strategies for awareness rising and to improve the quality of control programs in Pakistan.

Nanoparticles-Based Biosensor Coupled with Multiplex Loop-Mediated Isothermal Amplification for Detection of Staphylococcus aureus and Identification of Methicillin-Resistant S. aureus

Introduction

Staphylococcus aureus (S. aureus), including methicillin-resistant S. aureus (MRSA), is a common human pathogen, which can cause a variety of infections from mild to severe. In this article, a new diagnostic method called multiplex loop-mediated isothermal amplification combined with nanoparticles-based lateral flow biosensor (mLAMP-LFB) has been developed, which was proved to be fast, reliable, and simple for detecting S. aureus, and differentiate MRSA from methicillin-susceptible S. aureus (MSSA).

Materials and Methods

We designed a set of six primers targeting the nuc gene of S. aureus, and a set of five primers targeting the mecA gene of MRSA. The lateral flow biosensor visually reported the S. aureus-LAMP results within 2 mins. S. aureus species and non-S. aureus species were used to identify the specificity and sensitivity of the assay.

Results

The best conditions for LAMP were 50 mins at 63°C, and the sensitivity was 100 fg. No cross-reactivity was shown and the specificity of this assay is 100%. This assay requires 20 mins for DNA preparation, 50 mins for isothermal amplification and 2 mins for biosensor detection. The total time is within 75 mins. Among 96 sputum samples, LAMP-LFB and traditional culture method showed the same results, 8 (8.33%) samples were MRSA-positive, and 9 (9.38%) samples were MSSA-positive. Seven (7.29%) samples were MRSA-positive and 7 (7.29%) were MSSA-positive by PCR method. Compared with the culture method, diagnostic accuracy of m-LAMP-LFB assay was 100%. The results showed that the m-LAMP-LFB method has better detection ability than the PCR method.

Discussion

In short, this m-LAMP-LFB assay is a specific and sensitive method that can quickly identify S. aureus stains, and distinguish MRSA from MSSA, and can be used as a new molecular method for detection of S. aureus in laboratories.

Screening and identification of a human domain antibody against Brucella abortus VirB5

Brucellosis is caused by the genus Brucella. Brucella is widely distributed in cattle, swine, sheep, goat and other mammals including human. Animal brucellosis causes severe economic losses and affects related international transportation and trade. Human brucellosis causes both acute and chronic symptoms of multi-organ dysfunction. Brucella type IV secretion system (T4SS) VirB5 was required for macrophages infection and essential for virulence in mice. VirB5 is located on the cell surface and serves as a specific adhesin targeting host cell receptors. The aim of this study was to isolate and characterize a specific human domain antibody against Brucella abortus (B. abortus) VirB5 from human single domain antibody (sdAb or VHH) phage display library. Following five rounds of screening, an sdAb named as BaV5VH4 showed the highest affinity by enzyme-linked immunosorbent assay (ELISA). Its interaction with B. abortus VirB5 was verified by binding assay, dot blot and molecular docking. These findings in this paper could greatly help elucidate the molecular mechanisms of Brucella infection, and accelerate the development of sdAbs-based vaccines and neutralizing therapeutics of brucellosis.

Lateral flow biosensor combined with loop-mediated isothermal amplification for simple, rapid, sensitive, and reliable detection of Brucella spp

Brucella species is responsible for brucellosis in human and animals, which is still of public health, veterinarian, and economic concern in many regions of the world. Here, a novel molecular diagnosis assay, termed loop-mediated isothermal amplification coupled with nanoparticles-based lateral flow biosensor (LAMP-LFB), was developed and validated for simply, rapidly, and reliably detecting all Brucella spp. strains. A set of six primers was designed based on the Brucella-specific gene Bscp31. The Brucella-LAMP results were visually reported by biosensor within 2 mins. A variety of bacterial strains representing several Brucella species, as well as several Gram-negative and Gram-positive bacterial species were used to determine the analytical sensitivity and specificity of the assay. Optimal LAMP conditions were 63°C for 40 mins, and the assay’s sensitivity was found to be 100 fg of genomic DNA in the pure cultures. No cross-reactions to non-Brucella strains were obtained; thus, analytical specificity of LAMP-LFB assay is of 100%. Using the protocol, 20 mins for rapid DNA preparation followed by isothermal amplification (40 mins) combined with biosensor detection (2 mins) resulted in a total assay time of approximately 65 mins. In the case of 117 whole blood samples, 13 (11.11%) samples were Brucella-positive by LAMP-LFB, and the diagnostic accuracy was 100% when compared to the culture-biotechnical method. In conclusion, Brucella-LAMP-LFB technique developed in this study is a sensitive and specific method to rapidly identify all Brucella spp. strains, and can be applied as a potential diagnostic tool for brucellosis in basic, clinical, and field laboratories.

Detecting Biothreat Agents: From Current Diagnostics to Developing Sensor Technologies

Although a fundamental understanding of the pathogenicity of most biothreat agents has been elucidated and available treatments have increased substantially over the past decades, they still represent a significant public health threat in this age of (bio)terrorism, indiscriminate warfare, pollution, climate change, unchecked population growth, and globalization. The key step to almost all prevention, protection, prophylaxis, post-exposure treatment, and mitigation of any bioagent is early detection. Here, we review available methods for detecting bioagents including pathogenic bacteria and viruses along with their toxins. An introduction placing this subject in the historical context of previous naturally occurring outbreaks and efforts to weaponize selected agents is first provided along with definitions and relevant considerations. An overview of the detection technologies that find use in this endeavor along with how they provide data or transduce signal within a sensing configuration follows. Current "gold" standards for biothreat detection/diagnostics along with a listing of relevant FDA approved in vitro diagnostic devices is then discussed to provide an overview of the current state of the art. Given the 2014 outbreak of Ebola virus in Western Africa and the recent 2016 spread of Zika virus in the Americas, discussion of what constitutes a public health emergency and how new in vitro diagnostic devices are authorized for emergency use in the U.S. are also included. The majority of the Review is then subdivided around the sensing of bacterial, viral, and toxin biothreats with each including an overview of the major agents in that class, a detailed cross-section of different sensing methods in development based on assay format or analytical technique, and some discussion of related microfluidic lab-on-a-chip/point-of-care devices. Finally, an outlook is given on how this field will develop from the perspective of the biosensing technology itself and the new emerging threats they may face.

Rapid visual isothermal nucleic acid-based detection assay of Brucella species by polymerase spiral reaction

AIM

The aim of this study was to develop polymerase spiral reaction (PSR) for rapid, sensitive and specific detection of Brucella sp.

METHODS AND RESULTS

Polymerase spiral reaction assay was developed using specifically designed primers targeting the conserved multicopy IS711 gene of Brucella sp. The assay could be performed within 60 min at an isothermal temperature of 64°C. The lower limit of detection of PSR was 11·8 fg and conventional PCR was 1·18 pg of Brucella abortus genomic DNA. Thus, PSR was found to be 100-fold more sensitive than conventional PCR and was comparable to real-time PCR. The specificity of PSR was tested with other non-Brucella bacteria and also with some bacterial and viral pathogens causing abortions. The assay was found to be specific as it did not detect any putative pathogens other than Brucella sp. Fifty-six clinical samples suspected for brucellosis (aborted fetal stomach content) were screened with PSR to validate the applicability of the test to detect Brucella DNA. The same samples were also screened with conventional PCR and real-time PCR. Of 56 samples, 25 samples were found to be positive with both PSR as well as real-time PCR, whereas only 20 samples were found positive with conventional PCR.

CONCLUSIONS

The results of this study indicated that the PSR assay is a simple, rapid, sensitive and specific method for the detection of Brucella sp. that may improve diagnostic potential in clinical laboratories or can be used at diagnostic laboratories with minimal infrastructure.

SIGNIFICANCE AND IMPACT OF THE STUDY

The PSR assay, because of its simplicity and low cost, can be preferred to other molecular methods in the diagnosis of infectious diseases.

Evaluation of Different Primers for Detection of Brucella by Using PCR Method

INTRODUCTION

Brucellosis is a worldwide zoonosis and a significant cause of loss of health in humans and animals. Traditionally, classic diagnosis is carried out by isolation of Brucella, which is time-consuming, technically challenging and potentially dangerous. The aim of this study was to expand a molecular test that would be used for the develop detection of Brucella in a single reaction with high sensitivity and specificity, by targeting IS711element.

METHODS

This study was carried out from 2015 to 2016 at the Ayatolla Rohani hospital in Babol, Iran. The present study was designed to develop PCR assay, based on IS711 gene for rapid diagnosis of Brucella spp. and immediate detection of Brucella, with high sensitivity and specificity. Four pairs of oligo-nucleotide primers with sizes of 547, 403, 291 and 127bp respectively, were planned to exclusively amplify the targeted genes of Brucella species.

RESULTS

Our results show that, five PCR primers set up, would be helpful in amplifying the DNAs from the genus Brucella with high specificity and sensitivity so it can be 12 fg, for Brucella species to provide a valuable tool for diagnosis.

CONCLUSION

This method can be more useful than serological and biochemical tests and in addition, this reduces the number of required tests more rapidly and economically.

Visual Detection of Brucella spp. in Spiked Bovine Semen Using Loop-Mediated Isothermal Amplification (LAMP) Assay

Several pathogens including Brucella spp. are shed in semen of infected bulls and can be transmitted to cows through contaminated semen during artificial insemination. The present study reports omp2a and bcsp31 gene based loop-mediated isothermal amplification (LAMP) assays for detection of Brucella genomic DNA in semen from infected bulls. The positive results could be interpreted visually by change in colour of reaction mixture containing hydroxyl naphthol blue (HNB) dye from violet to sky blue. LAMP assays based on omp2a and bcsp31 could detect as little as 10 and 100 fg of B. abortus S19 genomic DNA, respectively. Sensitivity of omp2a and bcsp31 LAMP assays for direct detection of organisms in bovine semen was 2.28 × 10(1) CFU and 2.28 × 10(2) CFU of B. abortus S19 in spiked bovine semen, respectively. The omp2a LAMP assay was found equally sensitive to TaqMan probe based real-time PCR and 100 times more sensitive than conventional PCR in identifying Brucella in spiked semen. The diagnostic applicability of the omp2a LAMP assay was evaluated with seventy-nine bovine semen samples and results were re-evaluated through TaqMan probe based real-time PCR and conventional PCR. Taken together, the omp2a LAMP assay is easy to perform, rapid and sensitive in diagnosis of Brucella spp. in bovine semen.

Development of a rapid recombinase polymerase amplification assay for detection of Brucella in blood samples

A rapid and sensitive recombinase polymerase amplification (RPA) assay, Bruce-RPA, was developed for detection of Brucella. The assay could detect as few as 3 copies of Brucella per reaction within 20 min. Bruce-RPA represents a candidate point-of-care diagnosis assay for human brucellosis.

Rapid and specific identification of Brucella abortus using the loop-mediated isothermal amplification (LAMP) assay

A rapid and accurate diagnosis of brucellosis is required to reduce and prevent the spread of disease among animals and the risk of transfer to humans. In this study, a Brucella abortus-specific (Ba) LAMP assay was developed, that had six primers designed from the BruAb2_0168 region of chromosome I. The specificity of this LAMP assay was confirmed with Brucella reference strains, B. abortus vaccine strains, B. abortus isolates and phylogenetically or serologically related strains. The detection limit of target DNA was up to 20 fg/μl within 60 min. The sensitivity of the new LAMP assay was equal to or slightly higher than other PCR based assays. Moreover, this Ba-LAMP assay could specifically amplify all B. abortus biovars compared to previous PCR assays. To our knowledge, this is the first report of specific detection of B. abortus using a LAMP assay. The Ba-LAMP assay can offer a rapid, sensitive and accurate diagnosis of bovine brucellosis in the field.

Overview and challenges of molecular technologies in the veterinary microbiology laboratory

Terrestrial, aquatic, and aerial animals, either domestic or wild, humans, and plants all face similar health threats caused by infectious agents. Multifaceted anthropic pressure caused by an increasingly growing and resource-demanding human population has affected biodiversity at all scales, from the DNA molecule to the pathogen, to the ecosystem level, leading to species declines and extinctions and, also, to host-pathogen coevolution processes. Technological developments over the last century have also led to quantic jumps in laboratorial testing that have highly impacted animal health and welfare, ameliorated animal management and animal trade, safeguarded public health, and ultimately helped to "secure" biodiversity. In particular, the field of molecular diagnostics experienced tremendous technical progresses over the last two decades that significantly have contributed to our ability to study microbial pathogens in the clinical and research laboratories. This chapter highlights the strengths, weaknesses, opportunities, and threats (or challenges) of molecular technologies in the framework of a veterinary microbiology laboratory, in view of the latest advances.

Loop-mediated isothermal amplification (LAMP) test for specific and rapid detection of Brucella abortus in cattle

BACKGROUND

Brucella abortus, the major causative agent of abortion in cattle and a zoonotic pathogen, needs to be diagnosed at an early stage. Loop-mediated isothermal amplification (LAMP) test is easy to perform and also promising to be adapted at field level.

OBJECTIVE

To develop a LAMP assay for specific and rapid detection of B. abortus from clinical samples of cattle.

METHODS

LAMP primers were designed targeting BruAb2_0168 region using specific software tool and LAMP was optimized. The developed LAMP was tested for its specificity with 3 Brucella spp. and 11 other non-Brucella spp. Sensitivity of the developed LAMP was also carried out with known quantity of DNA. Cattle whole blood samples and aborted fetal stomach contents were collected and used for testing with developed LAMP assay and results were compared with polymerase chain reaction (PCR).

RESULTS

The developed LAMP assay works at 61 °C for 60 min and the detection limit was observed to be 100-fold more than the conventional PCR that is commonly used for diagnosis of B. abortus. Clinical sensitivity and specificity of the developed LAMP assay was 100% when compared with Rose Bengal plate test and standard tube agglutination test. SYB® green dye I was used to visualize the result with naked eye.

CONCLUSION

The novelty of the developed LAMP assay for specifically detecting B. abortus infection in cattle along with its inherent rapidness and high sensitivity can be employed for detecting this economically important pathogen of cattle at field level as well be exploited for screening of human infections.