Development and Evaluation of a Novel Taqman Real-Time PCR Assay for Rapid Detection of Mycoplasma bovis: Comparison of Assay Performance with a Conventional PCR Assay and Another Taqman Real-Time PCR Assay

Point-of-care potentials of lateral flow-based field screening for Mycoplasma bovis infections: a literature review

Point-of-care (POC) field screening for tools for Mycoplasma bovis (M. bovis) is still lacking due to the requirement for a simple, robust field-applicable test that does not entail specialized laboratory equipment. In accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines, this review identifies the methodologies that were retrieved based on our search strategy that have been reported for the diagnosis of m. bovis infection between 2014 and diagnostics. A search criterion was generated to curate 103 articles, which were reduced in number (to 46), following the screening guidelines of PRISMA. The 43 articles included in the study present 25 different assay methods. The assay methods were grouped as microbiological culture, serological assay, PCR-based assay, LAMP-based assay, NGS-based assay, or lateral flow assay. We, however, focus our discussion on the three lateral flow-based assays relative to others, highlighting the advantages they present above the other techniques and their potential applicability as a POC diagnostic test for M. bovis infections. We therefore call for further research on developing a lateral flow-based screening tool that could revolutionize the diagnosis of M. bovis infection.

Mycoplasma glycine cleavage system key subunit GcvH is an apoptosis inhibitor targeting host endoplasmic reticulum

Mycoplasmas are minimal but notorious bacteria that infect humans and animals. These genome-reduced organisms have evolved strategies to overcome host apoptotic defense and establish persistent infection. Here, using Mycoplasma bovis as a model, we demonstrate that mycoplasma glycine cleavage system (GCS) H protein (GcvH) targets the endoplasmic reticulum (ER) to hijack host apoptosis facilitating bacterial infection. Mechanically, GcvH interacts with the ER-resident kinase Brsk2 and stabilizes it by blocking its autophagic degradation. Brsk2 subsequently disturbs unfolded protein response (UPR) signaling, thereby inhibiting the key apoptotic molecule CHOP expression and ER-mediated intrinsic apoptotic pathway. CHOP mediates a cross-talk between ER- and mitochondria-mediated intrinsic apoptosis. The GcvH N-terminal amino acid 31-35 region is necessary for GcvH interaction with Brsk2, as well as for GcvH to exert anti-apoptotic and potentially pro-infective functions. Notably, targeting Brsk2 to dampen apoptosis may be a conserved strategy for GCS-containing mycoplasmas. Our study reveals a novel role for the conserved metabolic route protein GcvH in Mycoplasma species. It also sheds light on how genome-reduced bacteria exploit a limited number of genomic proteins to resist host cell apoptosis thereby facilitating pathogenesis.

Development of a multiplex qPCR assay for the simultaneous detection of Mycoplasma bovis, Mycoplasma species, and Acholeplasma laidlawii in milk

Contagious bovine mastitis caused by Mycoplasma bovis and other Mycoplasma species including Mycoplasma californicum, Mycoplasma bovigenitalium, Mycoplasma alkalescens, Mycoplasma arginini, and Mycoplasma canadense is an economical obstacle affecting many dairy herds throughout California and elsewhere. Routine bacteriological culture-based assays for the pathogens are slow and subject to false-positive results due to the presence of the related, non-pathogenic species Acholeplasma laidlawii. To address the need for rapid and accurate detection methods, a new TaqMan multiplex, quantitative real-time PCR (qPCR) assay was developed that targets the 16S rRNA gene of Mycoplasma, rpoB gene of M. bovis, and the 16S to 23S rRNA intergenic transcribed spacer (ITS) region of A. laidlawii. qPCR amplification efficiency and range of detection were similar for individual assays in multiplex as when performed separately. The multiplex assay was able to distinguish between M. bovis and A. laidlawii as well as detect Mycoplasma spp. collectively, including Mycoplasma californicum, Mycoplasma bovigenitalium, Mycoplasma canadense, Mycoplasma arginini and Mycoplasma alkalescens. In milk, the lower limit of detection of M. bovis, M. californicum, and A. laidlawii with the multiplex assay was between 120 to 250 colony forming units (CFU) per mL. The assay was also able to simultaneously detect both M. bovis and A. laidlawii in milk when present in moderate (103 to 104 CFU/mL) to high (106 to 107 CFU/mL) quantities. Compared to laboratory culture-based methods, the multiplex qPCR diagnostic specificity (Sp) was 100% (95% CI [86.8-100]; n = 26) and diagnostic sensitivity (Se) was 92.3% (95% CI [74.9-99.1]; n = 26) for Mycoplasma species in milk samples collected from California dairy farms. Similarly, the Sp was 100% (95% CI [90.5-100]; n = 37) and Se was 93.3% (95% CI [68.1-99.8]; n = 15) for M. bovis. Our assay can detect and distinguish among M. bovis, other prevalent Mycoplasma spp., and non-pathogenic Acholeplasma laidlawii for effective identification and control of mycoplasma mastitis, ultimately supporting dairy cattle health and high-quality dairy products in California.

Mycoplasma bovis Infections in Free-Ranging Pronghorn, Wyoming, USA

Mycoplasma bovis is 1 of several bacterial pathogens associated with pneumonia in cattle. Its role in pneumonia of free-ranging ungulates has not been established. Over a 3-month period in early 2019, »60 free-ranging pronghorn with signs of respiratory disease died in northeast Wyoming, USA. A consistent finding in submitted carcasses was severe fibrinosuppurative pleuropneumonia and detection of M. bovis by PCR and immunohistochemical analysis. Multilocus sequence typing of isolates from 4 animals revealed that all have a deletion in 1 of the target genes, adh-1. A retrospective survey by PCR and immunohistochemical analysis of paraffin-embedded lung from 20 pronghorn that died with and without pneumonia during 2007–2018 yielded negative results. These findings indicate that a distinct strain of M. bovis was associated with fatal pneumonia in this group of pronghorn.

Isolation, identification and biological characteristics of Mycoplasma bovis in yaks

Mycoplasma bovis (M. bovis) is one of the important pathogens which may cause bovine respiratory disease syndrome (BRDS), and results in huge economic losses for yaks (Bos gaurus) breeding industry. However, there is limited information about M. bovis in yaks. In our study, 145 nasal mucus samples from yaks with pneumonia were collected to clarify. Bacteriological determination was carried out through biochemical identification and Polymerase Chain Reaction (PCR) detection. And ten strains of Mycoplasma bovis (M. bovis) were found from collected samples. Then, the growth curve of isolated strains was determined by the change of optical density (OD₆₃₀), pH value and Color Change Cnit (CCU). K-B disk method was also used for antimicrobial susceptibility testing. Results of colony morphology and biochemical testing were consistent with the biological characters of M. bovis. The nucleotide sequences of uvrC specific gene and 16S rRNA gene among the 10 strains were highly homologous. The growth curve assay showed that the isolates cultured in PPLO medium were in lag phase for 24 h, entered stable period in 42 h, and entered decline phase after 78 h. The isolates were found resistant to macrolides, aminoglycosides and lincomycin at various degrees, but they were sensitive or moderately sensitive to doxycycline and kanamycin under antimicrobial susceptibility analysis. In conclusion, the results provided certain reference for the follow-up research and guiding for the treatment of M. bovis in yaks.

A direct qPCR screening approach to improve the efficiency of Mycoplasma bovis isolation in the frame of a broad surveillance study

Culturing Mycoplasma bovis is laborious and unpredictable with most laboratories relying on molecular methods for its detection and identification. However, bacterial culture is still necessary to relate phenotypic characteristics to genotypic traits within and between individual strains. Thus, the main objective of this study was to develop a procedure that saved time and consumables during the culturing of M. bovis within the scope of a broad antimicrobial resistance surveillance project. Deep nasopharyngeal swabs (DNPS) collected from feedlot cattle upon arrival at 10 Southern Alberta feedlots were enriched in broth and an aliquot of the culture was directly used in a M. bovis-specific quantitative PCR (qPCR) assay. Only qPCR-positive cultures were plated onto agar media for the isolation of M. bovis. The detection of M. bovis from broth culture by direct-culture-qPCR proved to be more sensitive (1.61 × 10² CFU/mL) than using a commercial kit (1.61 × 10³ CFU/mL) to extract DNA from pure cultures of M. bovis. When isolation of M. bovis from broth-enriched DNPS (n = 208 samples) was used as the gold standard for diagnostics, the qPCR screening approach showed 100% sensitivity, 87.27% specificity, and a kappa index = 0.87 (strong agreement). In contrast, qPCR of DNPS samples (n = 58) exhibited 100% sensitivity, 42.86% specificity, and a kappa index = 0.49 (weak agreement). The qPCR protocol described here together with a high throughput direct-culture-qPCR approach for sample testing made it possible to reduce the labor and cost of M. bovis isolation by eliminating the need to process 97.3% of M. bovis-negative samples. This was possible through the use of qPCR Ct values as a predictive tool of the likelihood of M. bovis isolation. This new procedure could be evaluated for its use in antimicrobial resistance surveillance programs that focus on Mycoplasma species.

Development of a recombinase polymerase amplification combined with a lateral flow dipstick assay for rapid detection of the Mycoplasma bovis

BACKGROUND

Mycoplasma bovis (M. bovis) is a major etiological agent of bovine mycoplasmosis around the world. Point-of-care testing in the field is lacking owing to the requirement for a simple, robust field applicable test that does not require professional laboratory equipment. The recombinase polymerase amplification (RPA) technique has become a promising isothermal DNA amplify assay for use in rapid and low-resource diagnostics.

RESULTS

Here, a method for specific detection of M. bovis DNA was established, which was RPA combined with lateral flow dipstick (LFD). First, the analytical specificity and sensitivity of the RPA primer and LF-probe sets were evaluated. The assay successfully detected M. bovis DNA in 30 min at 39 °C, with detection limit of 20 copies per reaction, which it was compared the real-time quantitative PCR (qPCR) assay. This method was specific because it did not detect a selection of other bacterial pathogens in cattle. Both qPCR and RPA-LFD assays were used to detect M. bovis 442 field samples from 42 different dairy farms in Shandong Province of China, also the established RPA-LFD assay obtained 99.00% sensitivity, 95.61% specificity, and 0.902 kappa coefficient compared with the qPCR.

CONCLUSIONS

To the author's knowledge, this is the first report using an RPA-FLD assay to visualise and detect M. bovis. Comparative analysis with qPCR indicates the potential of this assay for rapid diagnosis of bovine mycoplasmosis in resource limited settings.

Mistaken identity of an open reading frame proposed for PCR-based identification of Mycoplasma bovis and the effect of polymorphisms and insertions on assay performance

Mycoplasma bovis is an important cause of disease in cattle and bison. Because the bacterium requires specialized growth conditions, many diagnostic laboratories routinely use PCR to replace or complement conventional isolation and identification methods. A frequently used target of such assays is the uvrC gene, which has been shown to be highly conserved among isolates. We discovered that a previously described PCR putatively targeting the uvrC gene amplifies a fragment from an adjacent gene predicted to encode a lipoprotein. Comparison of the lipoprotein gene sequence from 211 isolates revealed several single nucleotide polymorphisms, 1 of which falls within a primer-binding sequence. Additionally, 3 isolates from this group were found to have a 1,658-bp transposase gene insertion within the amplified region that leads to a false-negative result. The insertion was not detected in a further 164 isolates. We found no evidence that the nucleotide substitution within the primer-binding region affects the assay sensitivity, performance, or limit of detection. Nonetheless, laboratories utilizing this method for identification of M. bovis should be aware that the region amplified may be prone to nucleotide substitutions and/or insertions relative to the sequence used for its design and that occasional false-negative results may be obtained.

Development of real-time PCR assay for the detection of Mycoplasma bovis

Mycoplasma bovis is one of the important bovine mycoplasma involved in economically important clinical conditions like respiratory diseases, otitis media, and mastitis. The present study was undertaken with the objective of developing a SYBR Green dye-based real-time PCR assay targeting uvrC gene for the diagnosis of M. bovis. The analytical sensitivity and specificity of the assay were evaluated. The test showed 10³-fold more sensitivity than conventional PCR and detected down to 100 fg level of DNA. It was found to be specific, as no cross reactivity was shown with other related bacteria and Mycoplasma species. The developed assay was able to detect down to 40 copies of uvrC gene from spiked bovine milk samples. At present, this developed assay may be used as a valuable diagnostic tool for the detection of Mycoplasma bovis.