Use of <i>Brucella abortus</i> species specific polymerase chain reaction assay for the diagnosis of bovine brucellosis

Evaluation of a Real-time PCR in Combination with a Cultivation Method for the Detection of Brucella Abortus in Organs of Infected Cattle in Southern Italy

Introduction

Brucellosis is a widespread zoonosis of great economic importance for livestock farming in many areas of the world. It is a highly infectious disease which is diagnosed using conventional serological and microbiological methods. The aim of this study was to assess the efficiency of a specific real-time PCR in combination with broth cultivation in detecting Brucella spp. in organs of infected cattle, in order to compare the sensitivity of the two approaches and the time needed in them until a correct diagnosis is made.

Material and Methods

We examined 67 organs collected from 10 cattle slaughtered following a brucellosis outbreak which occurred in February 2016 in southern Italy. The research was carried out by enrichment broth cultivations in combination with a real-time PCR every week for six weeks.

Results

Brucella strains were isolated by cultivation from 44 enrichment broths of organs. All isolates were later identified as Brucella abortus by real-time PCR. Using this method in combination with cultivation made it possible to identify the same percentage of infected animals faster than by cultivation alone. Moreover, the same diagnostic results were obtained, on average two weeks before they would have been using only cultivation. In almost all cases, Brucella was detected by real-time PCR after the first week of cultivation in pre-enrichment Brucella broth, while the bacterial growth was evident usually after 2 or 3 weeks.

Conclusion

Real-time PCR has allowed results to be obtained faster than in the classical microbiological method, reducing the response times to identify positive animals by half.

Characterisation of Brucella species and biovars in South Africa between 2008 and 2018 using laboratory diagnostic data

BACKGROUND

Brucellosis is an infectious zoonotic bacterial disease of humans and other animals. In the Republic of South Africa (RSA), animal brucellosis is widespread and the current available data on the prevalence of this disease rely solely on serological testing. The primary limitation of brucellosis serology is the lack of discriminatory powers to differentiate between Brucella species and biovars as well as the cross-reactivity observed with other Gram-negative bacteria.

AIM

The aim of this study was to conduct a retrospective laboratory-based survey on Brucella species and biovars isolated from various animal species in SA between 2008 and 2018.

MATERIAL AND METHODS

The isolation of Brucella species and biovar typing was performed using conventional microbiological techniques.

RESULTS AND DISCUSSION

A total of 963 strains of Brucella species were included in this study with a frequency of detection for B. abortus (n = 883; 91.6%) followed by B. melitensis (n = 42; 4.4%), B. ovis (n = 29; 3.0%) and B. canis (n = 9; 0.9%). Of the 883 strains of B. abortus, 90.1% were typed as B. abortus biovar-1 while 5.7% as B. abortus biovar-2, and 3.3% and 0.5% were B. abortus S19 and B. abortus RB51 vaccine strains, respectively. Among the 42 B. melitensis strains, 71.4% were reported as B. melitensis biovar-1 and 26.2% as B. melitensis biovar-3 while 2.4% was B. melitensis biovar-2.

CONCLUSION

A retrospective study, such as this one, provides useful information that can be critical in formulating policies and strategies for the control and eradication of brucellosis in animal populations in RSA.

Chimeric Protein Designed by Genome-Scale Immunoinformatics Enhances Serodiagnosis of Bovine Neosporosis

Neosporosis has become a concern since it is associated with abortion in cattle. Currently, in situ diagnosis is determined through anamnesis, evaluation of the history, and perception of the clinical signs of the herd. There is no practical and noninvasive test adapted to a large number of samples, which represents a gap for the use of new approaches that provide information about infections and the risks of herds. Here, we performed a search in the Neospora caninum genome by linear B-cell epitopes using immunoinformatic tools aiming to develop a chimeric protein with high potential to bind specifically to antibodies from infected cattle samples. An enzyme-linked immunosorbent assay with the new chimeric antigen was developed and tested with sera from natural field N. caninum-infected bovines. The cross-reactivity of the new antigen was also evaluated using sera from bovines infected by other abortive pathogens, including Trypanosoma vivax, Leptospira sp., Mycobacterium bovis, and Brucella abortus, and enzootic bovine leucosis caused by bovine leukemia virus, as well as with samples of animals infected with Toxoplasma gondii The assay using the chimeric protein showed 96.6% ± 3.4% of sensitivity in comparison to healthy animal sera. Meanwhile, in relation to false-positive results provided by cross-reactivity with others pathogens, the specificity value was 97.0% ± 2.9%. In conclusion, immunoinformatic tools provide an efficient platform to build an accurate protein to diagnose bovine neosporosis based on serum samples.