Polymerase chain reaction (PCR) for detection of Brucella melitensis in goat milk

Prevalence of Brucella spp. in milk from aborted and non-aborted animals in Dhamar governorate, Yemen

Brucella infection in animals is considered a great problem in most countries of the world. Our study designed to determine the prevalence of brucella in field animal's milk in Dhamar governorate, Yemen. Total of 808 raw milk samples from non-aborted field animals, 120 milk samples from aborted animals, and 30 pasteurized milk samples were teste by Milk-Ring Test (MRT), milk-ELISA test, isolation and identification of brucella species, and antibiotic susceptibility. The prevalence of brucella in milk samples from field animals was 0.8%, 2.6%, and 2% in cows, sheep, and goat milk samples respectively with MRT, and 0.8%, 1.3% and 1.6% in cows, sheep and goat milk samples respectively with the milk- ELISA test. The prevalence rate in milk samples from aborted animals was 33%, 64% and 41.2% with the MRT and 39%, 49%, and 41.2% in cows, sheep and goats respectively with the milk-ELISA test. All pasteurized milk samples were negative for the milk-ELISA test. The result of isolation showed 0.1% of Brucella in milk samples from field animals while 9.2% from aborted animals. All isolates of Brucella species were sensitivities to rifampicin, doxycycline, kanamycin, gentamicin, streptomycin, tetracycline, and ciprofloxacin, while resistant to ampicillin, erythromycin, and novobiocin. In conclusion, the high prevalence of milk brucella especially in aborted animals needs focusing and build controlling strategies plans to decrease the losses to the economy and avoid transferred to humans with unpasteurized milk consumption.

Brucella spp. Contamination in Artisanal Unpasteurized Dairy Products: An Emerging Foodborne Threat in Tunisia

Brucellosis is a worldwide zoonotic disease transmitted to humans, predominantly by the consumption of contaminated raw milk and dairy products. This study aimed to investigate the occurrence of Brucella spp. in 200 raw milk, ricotta, and artisan fresh cheese samples, collected from individual marketing points in four districts in Tunisia. Samples were analyzed for the presence of Brucella spp. by IS711-based real-time PCR assay. Positive samples were further analyzed by qPCR for B. melitensis and B. abortus species differentiation. The DNA of Brucella spp. was detected in 75% of the samples, B. abortus was detected in 31.3%, and B. melitensis was detected in 5.3% of positive samples. A percentage of 49.3% of samples co-harbored both species, while 14% of the Brucella spp. positive samples were not identified either as B. abortus or B. melitensis. High contamination rates were found in ricotta (86.2%), cheese (69.6%), and raw milk (72.5%) samples. The study is the first in Tunisia to assess the occurrence of Brucella spp. contamination in artisanal unpasteurized dairy products and showed high contamination rates. The detection of both B. abortus and B. melitensis highlights that zoonotic high-pathogen agent control remains a challenge for food safety and consumer health protection and could represent a serious emerging foodborne disease in Tunisia.

Prevalence of Brucella spp. in raw milk and artisanal cheese tested via real-time qPCR and culture assay

Brucellosis is one of the most prevalent zoonotic diseases with worldwide distribution. Although the incidence of brucellosis varies widely in different regions, it is a major concern for public health around the world. This study aimed to determine the prevalence and quantity of Brucella spp. in sheep and goat raw milk, as well as artisanal cheeses produced in the North-west of Iran. To evaluate the intrinsic parameters that may affect the survival of Brucella spp., some of the cheese properties (e.g., pH, salt, moisture, and storage time before selling) were also assessed. A total of 572 samples consisting in 214 sheep raw milk, 92 goat raw milk, and 266 local artisanal cheese samples were collected. The artisanal cheeses were manufactured from a mixture of raw sheep and goat milk. According to the results, using quantitative real-time PCR (qPCR), 17.29%, 15.22%, and 22.93% of the sheep raw milk, goat raw milk, and artisanal cheese samples were found positive for Brucella spp., respectively. In comparison with culture assay, qPCR was 3.5 to 5 times (p < 0.05) more sensitive in the detection of Brucella spp. The results also revealed that the mean values of Brucella spp. load in sheep and goat raw milk and artisanal cheeses were 1.22, 1.55, and 1.43 log cell/ml or g, respectively. A positive correlation was found between Brucella load and successful detection of Brucella spp. by culture assay. Data also suggested a correlation (p < 0.01) between the load of Brucella spp. estimated by qPCR and pH value, salt content, and storage period of the cheese samples. However, Brucella spp. load did not correlate significantly with the moisture content. Based on the results, in any of the cheese samples with a pH value less than 4.5 and a storage period more than five months, no contamination with Brucella spp. was detected.

Use of touch-down polymerase chain reaction to enhance the sensitivity of Brucella melitensis detection in raw milk

Brucellosis is a highly contagious bacterial zoonotic infectious disease severely affecting the public health and economic features of endemic and non-endemic countries. The present study assessed the potentials of using the touch-down polymerase chain reaction (TD-PCR) compared to the conventional PCR and culture methods in order to detect Brucella melitensis in raw milk samples of 55 sheep and 45 goats through deriving the primers from the omp31 element of the Brucella genome. In addition, nine isolates of B. melitensis were identified using the culture method. No positive cases were found in sediment samples, while the fatty tap layer test by conventional PCR and TD-PCR revealed 6 and 16 positive samples, respectively. Based on the survey of the limits of detection by TD-PCR and conventional PCR, TD protocol had a detection threshold of three logs higher than the conventional protocol under the experimental condition. The developed protocol of this study was highly sensitive and extremely fast. Therefore, this TD-PCR protocol could detect even a very low number of bacteria in milk samples. To our best knowledge, this is the first report on the use of the TD-PCR method to identify B. melitensis in milk.

Contamination of milk and dairy products by Brucella species: A global systematic review and meta-analysis

Brucellosis is known as an influential zoonosis in different regions worldwide, with significant effects on the reproductive performance of livestock. Considering the high incidence of brucellosis in dairy products and further negative impacts on food safety, the present study was aimed to systematically investigate prevalence worldwide among published data regarding the identification of Brucella spp. in dairy products. In this regard, some databases, i.e., Scopus, PubMed, Embase, and Web of Science have been searched to retrieve all related articles regarding the incidence of Brucella contaminations in dairy products from 1 January 1983 to 1 April 2019. The prevalence of Brucella spp. in unpasteurized dairy products based on countries, WHO regions, and dairy product subgroups were evaluated and statistically compared. Based on the findings, the prevalence of Brucella spp. in dairy products increased while the GDP (C = 0.17, P-value < 0.001) and HDI (C = 0.19, P-value < 0.001) ranking decreased. Also, the highest prevalence of Brucella contamination in dairy products was noted in buffalo (25.91%) and goat (17.90%), respectively. The lowest and highest prevalence of Brucella spp. were observed in the Western Pacific (15.32%) and the Southeast Asia region (25.55%), respectively. Also, the rank order of WHO regions based on odds ratio (OR) was Southeast Asia region (2.84) > Eastern Mediterranean (2.41) > Region of America (1.65) > European Region (1.54) > Africa region (1.46) > Western Pacific (reference). The results of this study showed that decreasing poverty and an increase in the level of education in societies could reduce the prevalence of Brucella spp. in dairy products. The outcome of the current investigation can be used for the implementation of sustainable intervention and prevention strategies in affected regions.

Seroepidemiology and the Molecular Detection of Animal Brucellosis in Punjab, Pakistan

Brucellosis is an infectious disease caused by bacteria of the genus Brucella (B.), affecting both animals and humans, causing severe economic loses and severe illness, respectively. The objective of the present study was to determine the seroprevalence and the risk factors associated with caprine, ovine, and bovine brucellosis in selected districts of Punjab, Pakistan. A total of 1083 blood samples were randomly collected from animals (goats = 440, sheep = 203, cows = 206, and buffaloes = 234). Questionnaires were used to collect data on risk factors associated with brucellosis on the sampling day. All samples were initially screened for anti-Brucella antibodies using the rose bengal plate test (RBPT). The seropositive serum samples were confirmed by a quantitative real-time polymerase chain reaction (PCR) assay for the detection of the Brucella genus- and Brucella species-specific DNA (B. abortus and B. melitensis). Univariant and binary logistic regression were used to identify important risk factors of brucellosis. Anti-Brucella antibodies and DNA were detected in 35 (3.23%) serum samples. Thirty-four (97.1%) DNA samples were confirmed as B. melitensis by qRT-PCR. Abortion history and natural mating were found to be potential risk factors. Brucella melitensis was identified as the causative agent of caprine, ovine, and bovine brucellosis in the selected districts of Punjab, Pakistan. Diseased animals may act as a source of infection for other animals. The elimination of positive seroreactors, development of control strategies for brucellosis, and education programs regarding the control of zoonotic disease are highly needed in developing countries like Pakistan.

Prevalence of Caprine brucellosis in Anhui province, China

Background and Aim

Brucellosis is one of the most widespread zoonotic diseases globally. Studies indicated the existence of Brucella infection in goats in some province of China. Thus this study aimed to estimate the prevalence of brucellosis in goats of Anhui Province, China.

Materials and Methods

Serum and milk samples obtained from goats in different regions of Anhui province were studied through rose Bengal plate test (RBPT), serum agglutination test (SAT), milk ring test (MRT), and polymerase chain reaction (PCR).

Results

The investigation frequency of brucellosis using RBPT, SAT, MRT, and PCR methods was 3.9% (n=7), 4.45% (n=8), 11.67% (n=7), and 86.67% (n=156), respectively. The prevalence recorded for brucellosis in sex-wise animals as in females 5.55%, 6.67%, 11.67%, and 78.8% through above methods, while in males, it was 2.23% and 2.23% by RBPT and SAT. However, in age-wise animals, the results 6.36%, 7.27%, 11.67%, and 74.5% were perceived positive by RBPT, SAT, MRT, and PCR in adult females, respectively, but young males and females (up to 9 months) were considered free from brucellosis.

Conclusion

These results show that prevalence of brucellosis was relatively higher in females than male's goats and SAT was relatively specific and accurate as compared to RBPT and MRT, but for diagnosis of brucellosis, molecular method (PCR) is recommended.

Human brucellosis caused by raw dairy products: A review on the occurrence, major risk factors and prevention

Despite considerable efforts made to address the issue of brucellosis worldwide, its prevalence in dairy products remains difficult to estimate and represents an important public health issue in many areas of the globe today. This is partly explained by the increasing tendency for consumption of raw dairy products, making the prevention and control of this zoonosis even more critical. This review summarizes reports published since the early 2000s on human brucellosis caused by contaminated dairy products and the systems of evaluation and assessment which are used to improve the diagnosis, surveillance, control and prevention of the disease. For this purpose, five comprehensive electronic databases were investigated and relevant studies were identified for systematic review. The design and quality of the studies revealed notable variation, especially in the methods used for the detection and characterization of Brucella spp. This report provides helpful information about the health risk associated with the consumption of raw milk and relevant preventive strategies.

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.

Molecular prevalence of Toxoplasma gondii DNA in goats' milk and seroprevalence in Northwest Tunisia

Toxoplasmosis is a worldwide zoonosis with high impact on human and animal health. Consumption of unpasteurized milk is a risk factor of human toxoplasmosis. The aim of this study was to estimate the seroprevalence and molecular prevalence of T. gondii in goats’ milk in Northwest of Tunisia (Jendouba Governorate). A total number of 77 blood samples were collected from six herds were screened with a commercial ELISA kit for T. gondii antibodies. For the same goats’ samples, a nested PCR was performed to detect T. gondii DNA in milk. The seroprevalence of T. gondii infection was 31.2% (±0.05) while the molecular prevalence of this parasite in milk was estimated to 7.8% (±0.03). A very low value of kappa showed that there is not agreement between seroprevalence and parasite prevalence in milk. These results suggest that the consumption of raw milk from naturally infected goats is a potential source of human infection. An extension programme should be implemented to decrease related to goats’ raw milk consumption.

16S rRNA and omp31 gene based molecular characterization of field strains of B. melitensis from aborted foetus of goats in India

Brucellosis is a reemerging infectious zoonotic disease of worldwide importance. In human, it is mainly caused by Brucella melitensis, a natural pathogen for goats. In India, a large number of goats are reared in semi-intensive to intensive system within the close vicinity of human being. At present, there is no vaccination and control strategy for caprine brucellosis in the country. Thus, to formulate an effective control strategy, the status of etiological agent is essential. To cope up with these, the present study was conducted to isolate and identify the prevalent Brucella species in caprine brucellosis in India. The 30 samples (fetal membrane, fetal stomach content and vaginal swabs) collected throughout India from the aborted fetus of goats revealed the isolation of 05 isolates all belonging to Brucella melitensis biovars 3. All the isolates produced amplification products of 1412 and 720 bp in polymerase chain reaction with genus and species specific 16S rRNA and omp31 gene based primers, respectively. Moreover, the amplification of omp31 gene in all the isolates confirmed the presence of immuno dominant outer membrane protein (31 kDa omp) in all the field isolates of B. melitensis in aborted foetus of goats in India. These findings can support the development of omp31 based specific serodiagnostic test as well as vaccine for the control of caprine brucellosis in India.

Loop-mediated isothermal amplification assay targeting the omp25 gene for rapid detection of Brucella spp

A novel loop-mediated isothermal amplification (LAMP) assay was established to detect Brucella species DNA in milk and blood samples of animals and humans. This LAMP assay based on the sequence of highly repetitive omp25 gene was able to detect 9fg/μl Brucella spp. DNA with high sensitivity, which was 10 times higher than the nested PCR. The LAMP was evaluated for its specificity using 19 strains of six Brucella species and 28 related non-Brucella micro-organism strains as controls. The target 19 Brucella strains were all amplified, and no cross-reaction was found with all the non-Brucella micro-organism strains. Both nested PCR and LAMP assays were then used to detect Brucella spp. DNA in 78 milk samples and 113 blood samples from animals and 11 blood samples from humans, and the established LAMP assay yielded 99.0% concordance rate with the nested PCR. The LAMP assay should be a potential tool with high convenience, rapidity, sensitivity and specificity for the diagnosis of Brucellosis.

Detection of Brucella abortus in Bovine Milk by Polymerase Chain Reaction

This study compares milk ring test and three different polymerase chain reaction techniques (direct DNA extraction by column purification system, alkaline DNA extraction, and filtrated milk), in order to identifyBrucella abortusinfection in bovine milk. Milk ring test sensitivity and specificity were 72% and 80%, respectively. While specificity of the three polymerase chain reaction techniques was 100%; sensitivity was 92%, 88% and 100%, respectively, for the three polymerase chain reaction procedures. We conclude that the filtered animal’s milk polymerase chain reaction is the best procedure to make the diagnosis ofB. abortusinfections.

Monitoring of Brucella reactor does following milk examination using different techniques

Milk samples from 129 does were collected and monitored for Brucella antibodies using immunological tests such as Milk Ring Test (MRT), Whey Agglutination Test (WAT), Whey Antiglobulin Coombs Test (WCT) and milk ELISA (m ELISA) using Brucella Periplasmic protein antigen. Results obtained from these tests were compared to PCR and bacterial isolation. The highest incidence of positive reactors was given by Whey Antiglobulin and Whey Agglutination Test (9.3%) while the lowest incidence was given by bacterial isolation (Br. melitensis biovars 3, 3.8%). PCR showed the highest agreement with the bacterial isolation, while WAT and WCT showed the lowest one. PCR showed a high sensitivity of 1 x 10 B. melitensis CFU mL(-1) of milk. The results of mELISA here suggests its efficiency to be used as a screening test and/or confirmatory test, while the modified MRT still need more investigations to diagnosis caprine brucellosis.