Comparison of LCD array and IS6110-PCR with conventional techniques for detection of Mycobacterium bovis isolated from Egyptian cattle and Buffaloes

Diagnosis of bacteria from the CMNR group in farm animals

The CMNR group comprises bacteria of the genera Corynebacterium, Mycobacterium, Nocardia, and Rhodococcus and share cell wall and DNA content characteristics. Many pathogenic CMNR bacteria cause diseases such as mastitis, lymphadenitis, and pneumonia in farmed animals, which cause economic losses for breeders and represent a threat to public health. Traditional diagnosis in CMNR involves isolating target bacteria on general or selective media and conducting metabolic analyses with the assistance of laboratory biochemical identification systems. Advanced mass spectrometry may also support diagnosing these bacteria in the clinic's daily routine despite some challenges, such as the need for isolated bacteria. In difficult identification among some CMNR members, molecular methods using polymerase chain reaction (PCR) emerge as reliable options for correct specification that is sometimes achieved directly from clinical samples such as tracheobronchial aspirates and feces. On the other hand, immunological diagnostics such as the skin test or Enzyme-Linked Immunosorbent Assay (ELISA) for Mycobacterium tuberculosis yield promising results in subclinical infections with no bacterial growth involved. In this review, we present the methods most commonly used to diagnose pathogenic CMNR bacteria and discuss their advantages and limitations, as well as challenges and perspectives on adopting new technologies in diagnostics.

Accuracy of molecular diagnostic assays for detection of Mycobacterium bovis: A systematic review and meta-analysis

Bovine tuberculosis (bovine TB) is a chronic wasting disease of cattle caused primarily by Mycobacterium bovis. Controlling bovine TB requires highly sensitive, specific, quick, and reliable diagnostic methods. This systematic review and meta-analysis evaluated molecular diagnostic tests for M. bovis detection to inform the selection of the most viable assay. On a per-test basis, loop-mediated isothermal amplification (LAMP) showed the highest overall sensitivity of 99.0% [95% CI: 86.2%-99.9%] and specificity of 99.8% [95% CI: 96.2%-100.00%]. Quantitative real-time polymerase chain reaction (qPCR) outperformed conventional PCR and nested PCR (nPCR) with a diagnostic specificity of 96.6% [95% CI: 88.9%-99.0%], while the diagnostic sensitivity of 70.8% [95% CI: 58.6-80.5%] was comparable to that of nPCR at 71.4% [95% CI: 60.7-80.2%]. Test sensitivity was higher with the input of milk samples (90.9% [95% CI: 56.0%-98.7%]), while specificity improved with tests based on major M. bovis antigens (97.8% [95% CI: 92.3%-99.4%]), the IS6110 insertion sequence (95.4% [95% CI: 87.6%-98.4%]), and the RD4 gene (90.7% [95% CI: 52.2%-98.9%]). The design of the currently available molecular diagnostic assays, while mostly based on nonspecific gene targets, prevents them from being accurate enough to diagnose M. bovis infections in cattle, despite their promise. Future assay development should focus on the RD4 region since it is the only target identified by genome sequence data as being distinctive for detecting M. bovis. The availability of a sufficiently accurate diagnostic test combined with the routine screening of milk samples can decrease the risk of zoonotic transmissions of M. bovis.

Zoonotic Tuberculosis: A Neglected Disease in the Middle East and North Africa (MENA) Region

Mycobacterium bovis is the etiologic agent of bovine tuberculosis (BTB), a serious infectious disease in both humans and animals. BTB is a zoonotic disease primarily affecting cattle and occasionally humans infected through close contact with infected hosts or the consumption of unpasteurized dairy products. Zoonotic tuberculosis is strongly associated with poverty and poor hygiene, and low- and middle-income countries bear the brunt of the disease. BTB has been increasingly recognized as a growing public health threat in developing countries. However, the lack of effective surveillance programs in many of these countries poses a barrier to accurately determining the true burden of this disease. Additionally, the control of BTB is threatened by the emergence of drug-resistant strains that affect the effectiveness of current treatment regimens. Here, we analyzed current trends in the epidemiology of the disease as well as the antimicrobial susceptibility patterns of M. bovis in the Middle East and North Africa (MENA) region, a region that includes several developing countries. Following PRISMA guidelines, a total of 90 studies conducted in the MENA region were selected. Our findings revealed that the prevalence of BTB among humans and cattle varied significantly according to the population size and country in the MENA region. Most of the available studies were based on culture and/or PCR strategies and were published without including data on antimicrobial resistance and molecular typing. Our findings highlighted the paramount need for the use of appropriate diagnostic tools and the implementation of sustainable control measures, especially at the human/animal interface, in the MENA region.

Differential gene expression in Mycobacterium bovis challenged monocyte-derived macrophages of cattle

A functional genomics approach was used to examine the immune response for transcriptional profiling of PBMC M. bovis infected cattle and healthy control cattle to stimulation with bovine tuberculin (purified protein derivative PPD-b). Total cellular RNA was extracted from non-challenged control and M. bovis challenged MDM for all animals at intervals of 6 h post-challenge, in response to in-vitro challenge with M. bovis (multiplicity of infection 2:1) and prepared for global gene expression analysis using the Agilent Bovine (V2) Gene Expression Microarray, 8 × 60 K. The pattern of expression of these genes in PPD bovine stimulated PBMC provides the first description of an M. bovis specific signature of infection that may provide insights into the molecular basis of the host response to infection. Analysis of these mapped reads showed 2450 genes (1291 up regulated and 1158 down regulated) 462 putative natural antisense transcripts (354 up-regulated and 108 down regulated) that were differentially expressed based on sense and antisense strand data, respectively (adjusted P-value ≤ 0.05). The results provided enrichment for genes involved top ten up regulated and down regulated panel of genes, including transcription factors proliferation of T and B lymphocytes. The highest differentially-expressed genes were associated to immune and inflammatory responses, immunity, differentiation, cell growth, apoptosis, cellular trafficking and regulation of lipolysis and thermogenesis. Microarray results were confirmed in infected cattle by RT qPCR to identify potential biomarkers TLR2, CD80, NFKB1, IL8, CXCL6 and ADORA3 of bovine tuberculosis.