Detection and identification of Mycoplasma from bovine mastitis infections using a nested polymerase chain reaction

Mycoplasma bovis mastitis in dairy cattle

Mycoplasma bovis has recently been identified increasingly in dairy cows causing huge economic losses to the dairy industry. M. bovis is a causative agent for mastitis, pneumonia, endometritis, endocarditis, arthritis, otitis media, and many other clinical symptoms in cattle. However, some infected cows are asymptomatic or may not shed the pathogen for weeks to years. This characteristic of M. bovis, along with the lack of adequate testing and identification methods in many parts of the world until recently, has allowed the M. bovis to be largely undetected despite its increased prevalence in dairy farms. Due to growing levels of antimicrobial resistance among wild-type M. bovis isolates and lack of cell walls in mycoplasmas that enable them to be intrinsically resistant to beta-lactam antibiotics that are widely used in dairy farms, there is no effective treatment for M. bovis mastitis. Similarly, there is no commercially available effective vaccine for M. bovis mastitis. The major constraint to developing effective intervention tools is limited knowledge of the virulence factors and mechanisms of the pathogenesis of M. bovis mastitis. There is lack of quick and reliable diagnostic methods with high specificity and sensitivity for M. bovis. This review is a summary of the current state of knowledge of the virulence factors, pathogenesis, clinical manifestations, diagnosis, and control of M. bovis mastitis in dairy cows.

Detection by multiplex PCR of Mycoplasma species associated with dairy cattle in Argentina

There is scarce information about the frequency and epidemiological and clinical features associated with the presence of Mycoplasma spp. in Argentine dairy herds. The objectives of this study were to develop a multiplex PCR for identifying M.bovis and M.canadense and to describe the frequency of Mycoplasma spp. isolated from clinical samples submitted to a diagnostic laboratory. Of a total of 1548 samples from intramammary infections, bulk tank milk and biological fluids, 38 Mycoplasma isolates were obtained. M. bovis, M. canadense, M.californicum and M.leachii were detected by using two multiplex PCRs, confirming their presence in clinical conditions in dairy cattle. The techniques used in the present study can be useful to broaden the knowledge about Mycoplasma infections in cattle, since the search for these organisms is not usually included in routine diagnoses.

Molecular genetic techniques and oligonucleotides for mycoplasma identification – a review

Control of distribution of mycoplasmal infections in cattle herds is essential in the majority of countries world-wide. Various PCR procedures are available to detect mycoplasmas in cell cultures and bovine mycoplasma in different types of samples. We reviewed some common PCR techniques and specific primers targeted to different bacterial genetic regions of mycoplasma. Several researchers used the same PCR approach and Mycoplasma spp. as a target but their results could not be compared because different primer pairs were used. These methods and primers were first developed to identify mycoplasma species that contaminate animal cell cultures, and then were used by other researchers to differentiate mycoplasmas as a cow infecting agent. Our analysis of the specificity of these primer pairs to nucleotide sequences of five Mycoplasma spp. showed that oligonucleotides have less specificity to them. Numerous commercially available PCR kits are applicable to find mycoplasma contamination in cell cultures and fewer of them can be used in veterinary diagnostics. Although serological and culture techniques are still used, it is necessary to develop a new multiplex PCR technique with a more specific primer set especially in agrarian countries.

Technological interventions and advances in the diagnosis of intramammary infections in animals with emphasis on bovine population-a review

Mastitis, an inflammation of the udder, is a challenging problem in dairy animals accounting for high economic losses. Disease complexity, degree of economic losses and increasing importance of the dairy industries along with public health concerns envisages devising appropriate diagnostics of mastitis, which can offer rapid, accurate and confirmatory diagnosis. The various diagnostic tests of mastitis have been divided into general or phenotypic and specific or genotypic tests. General or phenotypic tests are those that identify general alterations, which are not specific to any pathogen. Genotypic tests are specific, hence confirmatory for diagnosis of mastitis and include specific culture, polymerase chain reaction (PCR) and its various versions (e.g. qRT-PCR), loop-mediated isothermal amplification, lateral flow assays, nucleotide sequencing, matrix-assisted laser desorption ionization time-of-flight mass spectrometry, and other molecular diagnostic methods. However, for highly specific and confirmatory diagnosis, pure cultures still provide raw materials for more sophisticated diagnostic technological interventions like PCR and nucleotide sequencing. Diagnostic ability of like infra-red thermography (IRT) has been shown to be similar to California mastitis test and also differentiates clinical mastitis from subclinical mastitis cases. As such, IRT can become a convenient and portable diagnostic tool. Of note, magnetic nanoparticles-based colorimetric biosensor assay was developed by using for instance proteolytic activity of plasmin or anti-S. aureus antibody. Last but not least, microRNAs have been suggested to be potential biomarkers for diagnosing bovine mastitis. This review summarizes the various diagnostic tests available for detection of mastitis including diagnosis through general and specific technological interventions and advances.

Causes, types, etiological agents, prevalence, diagnosis, treatment, prevention, effects on human health and future aspects of bovine mastitis

Mastitis is among the most common and challenging diseases of dairy animals. It is an inflammation of udder tissues due to physical damage, chemical irritation, or infection caused by certain pathogens. Bovine mastitis has been known for ages, but its complex etiology and multi-factorial nature make it difficult to control. Mastitis may have a negative impact on human health by inducing antibiotic-resistant pathogens that may spread, which is threatening. Researchers are continuously struggling to devise suitable methods for mastitis control. Management strategies are mainly focused on disease prevention by farm management which includes proper hygiene, trained staff to monitor minor changes in the udder or milk, and better diagnostic and treatment methods. New technologies which have the potential to unravel this complicated disease include improved diagnostic tools, based on advanced genomics or proteomics, prevention, based on vaccines and immune modulators, and metabolic products of probiotics such as bacteriocins and gene therapy.

Microbiological and molecular detection of Mycoplasma bovis in milk samples from bovine clinical mastitis

ABSTRACT: The genus Mycoplasma includes more than 200 bacterial species that cause disease in animals. It is responsible for causing mastitis in bovines and may be related to other manifestations, such as arthritis and pneumonia in calves and heifers. The present study aimed to detect Mycoplasma bovis isolated from milk samples of bovine clinical mastitis, and to compare the isolation rates in two culture media: Hayflick and SP4. An initial screening was performed in order to detect the presence of the class Mollicutes in 1166 milk samples from clinical mastitis by the conventional Polymerase Chain Reaction (PCR) technique. According to the 1166 milk samples evaluated, 8.6% (100/1166) were positive to class Mollicutes. Regarding molecular analyses, 1.1% (13/1166) of conventional PCR for positive M. bovis was obtained and 0.9% (11/1166) in real-time PCR. The results of the microbiological culture of the 100 samples previously screened demonstrated that 6% (6/100) of colony growth have been developed when using the Hayflick medium, and 11% (11/100) when using the SP4 medium (including the positive on Hayflick medium). Concerning the 11 isolates obtained in the microbiological culture, conventional PCR confirmed M. bovis in nine of them, and two cultures were negative. In the phylogenetic analysis of the isolates, all of them were grouped in M. bovis and M. agalactiae clusters. The results confirmed the importance of the presence of M. bovis in the etiology of bovine clinical mastitis and reinforced the need for further studies to elucidate other Mycoplasma species that may be involved in bovine clinical mastitis in Brazil.

Characterization of minimal lesions related to the presence of visna/maedi virus in the mammary gland and milk of dairy sheep

Background

In order to characterize the complete range of lesions, especially minimal, affecting mammary gland and viral antigen distribution and target cells using immunohistochemistry in naturally Visna/maedi (VM) 84 infected sheep were studied, forty-four from flocks with clinical cases (A) and 35 randomly sampled from two abattoirs (B) together with five negative controls (C). An immunocytochemistry technique was developed and further milk samples (n = 39) were used to study viral excretion, carrier cells and the role of milk and colostrum in the transmission of the disease.

Results

All sheep from group C and three sheep from group B were negative to VM in tissue sections by histopathology, immunohistochemistry and PCR, and also in serum using ELISA. Several degrees of CD3 + lymphocytic interstitial mastitis were observed in groups A and B: minimal (+) n = 26 sheep; moderate (++), n = 32 and severe (+++), n = 12. No differences in lesion distribution were observed between groups A and B. Viral presence was confirmed by immunohistochemistry using two different antibodies and/or PCR in every tissue with lesions while serology was negative in six sheep with lesions. Two milk samples taken from milk tanks from two flocks from group A and fourteen milk samples from 29 infected sheep from group B were positive to VM (most of them from animals with moderate and severe lesions). Positivity was only found in macrophages, even in focal and minimal lesions, while no positivity was observed in epithelial or any other cells in either tissue and milk samples.

Conclusions

This new observation of the minimal lesions described in this work increased the prevalence of VM lesions in mammary gland up to 90.9% and VM should be considered as a differential diagnosis when minimal interstitial lesions are detected. A high prevalence of VM was observed in intensive milk-producing sheep, ELISA serology did not detect as positivity all infected animals, while histology, IHC or PCR showed higher sensitivity. The cytological technique developed was very useful in milk-cell studies using hematoxylin and eosin and immunocytochemistry. Viral detection in milk samples (16/39) confirms a potential but limited role of milk/colostrum in viral transmission.

Electronic supplementary material

The online version of this article (10.1186/s12917-019-1855-3) contains supplementary material, which is available to authorized users.

Identification of subclinical mastitis caused by Mycoplasma spp. from screenings of bulk tanks

ABSTRACT Mastitis caused by Mycoplasma spp., regardless of species, are considered highly contagious pathogens and, usually was not responsive to antimicrobial therapy. Five dairy herds, comprising 489 animals and 1,956 mammary glands, were used in this study. Milk samples were obtained from bulk tanks and subjected to polymerase chain reaction (PCR) for the identification of Mollicutes, Mycoplasma spp., and Mycoplasma bovis. Moreover, individual samples from cases of clinical and subclinical mastitis in quarters of the dairy herds’ animals that yielded a positive PCR upon bulk tank analysis were subjected to molecular analysis. Only one bulk tank was positive for class Mollicutes by PCR. All positive samples classified as mastitis teats had their DNA extracted and tested by PCR for both class Mollicutes and M. bovis. Of these, two (2.08%) were positive for Mycoplasma genus, although none was positive for M. bovis. This result suggests that the PCR of bulk tanks is a viable tool in monitoring and preventing mastitis infections caused by Mycoplasma spp.

Validation of a mycoplasma molecular diagnostic test and distribution of mycoplasma species in bovine milk among New York State dairy farms

Mycoplasma mastitis is a contagious and costly disease of dairy cattle that significantly affects animal health and milk productivity. Mycoplasma bovis is the most prevalent and invasive agent of mycoplasma mastitis in dairy cattle, and early detection is critical. Other mycoplasma have been isolated from milk; however, the role and prevalence of these species as mastitis pathogens are poorly understood. Routine screening of milk for mycoplasma by bacteriological culture is an important component of a farm control strategy to minimize a herd mycoplasma outbreak, but phenotypic methods have limited ability to speciate mycoplasma, affecting how farms and practitioners can understand the role and effect of species other than M. bovis in herd health. Fastidious mycoplasma culture can be lengthy and inconclusive, resulting in delayed or false negative reports. We developed and validated a multitarget PCR assay that can in the same day confirm or reject a presumptive positive mycoplasma culture found upon bacteriological testing of clinical specimens, further discriminate between Acholeplasma and Mycoplasma, and identify M. bovis. Coupled with sequence analysis isolates can be further identified as bovine mycoplasma Mycoplasma arginini, Mycoplasma alkalescens, Mycoplasma canadense, Mycoplasma bovirhinis, Mycoplasma bovigenitalium, Mycoplasma californicum, Acholeplasma laidlawii, and Acholeplasma oculi. Assay validation included analysis of 845 mycoplasma representing these species and 30 additional bacterial species obtained from routine milk submissions to the Quality Milk Production Services from New York State farms and veterinary clinics between January 2012 and December 2015. Among 95 herds, we found 8 different Mycoplasma species and 3 different Acholeplasma species, with an overall prevalence of M. bovirhinis of 1%, A. oculi of 2%, M. arginini of 2%, M. californicum of 3%, M. canadense of 10%, M. bovigenitalium of 10%, A. laidlawii of 11%, M. alkalescens of 17%, and M. bovis of 78%. More than one mycoplasma was found in 14% of the herds tested, and both M. bovis and Acholeplasma were found in 6% of the farms. Incorporation of the validated molecular diagnostic assay into routine bacteriological screening as a supportive confirmation and identification tool will lead to an improved assessment of Mycoplasma and Acholeplasma prevalence data, which will facilitate increased knowledge about the role of these mycoplasma in mastitis.

6th International Conference on Emerging Zoonoses

The 6th International Conference on Emerging Zoonoses, held at Cancun, Mexico, 24-27 February 2011, offered 84 participants from 18 countries, a snapshot of current research in numerous zoonoses caused by viruses, bacteria or prions. Co-chaired by Professors Heinz Feldmann and Jürgen Richt, the conference explored 10 topics: (i) The ecology of emerging zoonotic diseases; (ii) The role of wildlife in emerging zoonoses; (iii) Cross-species transmission of zoonotic pathogens; (iv) Emerging and neglected influenza viruses; (v) Haemorrhagic fever viruses; (vi) Emerging bacterial diseases; (vii) Outbreak responses to zoonotic diseases; (viii) Food-borne zoonotic diseases; (ix) Prion diseases; and (x) Modelling and prediction of emergence of zoonoses. Human medicine, veterinary medicine and environmental challenges are viewed as a unity, which must be considered under the umbrella of 'One Health'. Several presentations attempted to integrate the insights gained from field data with mathematical models in the search for effective control measures of specific zoonoses. The overriding objective of the research presentations was to create, improve and use the tools essential to address the risk of contagions in a globalized society. In seeking to fulfil this objective, a three-step approach has often been applied: (i) use cultured cells, model and natural animal hosts and human clinical models to study infection; (ii) combine traditional histopathological and biochemical approaches with functional genomics, proteomics and computational biology; and (iii) obtain signatures of virulence and insights into mechanisms of host defense response, immune evasion and pathogenesis. This meeting review summarizes 39 of the conference presentations and mentions briefly the 16 articles in this Special Supplement, most of which were presented at the conference in earlier versions. The full affiliations of all presenters and many colleagues have been included to facilitate further inquiries from readers.

Molecular epidemiology of mastitis pathogens of dairy cattle and comparative relevance to humans

Mastitis, inflammation of the mammary gland, can be caused by a wide range of organisms, including gram-negative and gram-positive bacteria, mycoplasmas and algae. Many microbial species that are common causes of bovine mastitis, such as Escherichia coli, Klebsiella pneumoniae, Streptococcus agalactiae and Staphylococcus aureus also occur as commensals or pathogens of humans whereas other causative species, such as Streptococcus uberis, Streptococcus dysgalactiae subsp. dysgalactiae or Staphylococcus chromogenes, are almost exclusively found in animals. A wide range of molecular typing methods have been used in the past two decades to investigate the epidemiology of bovine mastitis at the subspecies level. These include comparative typing methods that are based on electrophoretic banding patterns, library typing methods that are based on the sequence of selected genes, virulence gene arrays and whole genome sequencing projects. The strain distribution of mastitis pathogens has been investigated within individual animals and across animals, herds, countries and host species, with consideration of the mammary gland, other animal or human body sites, and environmental sources. Molecular epidemiological studies have contributed considerably to our understanding of sources, transmission routes, and prognosis for many bovine mastitis pathogens and to our understanding of mechanisms of host-adaptation and disease causation. In this review, we summarize knowledge gleaned from two decades of molecular epidemiological studies of mastitis pathogens in dairy cattle and discuss aspects of comparative relevance to human medicine.

Detection of multiple Mycoplasma species in bulk tank milk samples using real-time PCR and conventional culture and comparison of test sensitivities

The objective of this study was to further validate a SYBR PCR protocol for Mycoplasma spp. by comparing it with standard microbial culture in the detection of Mycoplasma spp. in bulk tank milk samples. Additionally, we identified Mycoplasma spp. present by analysis of PCR-generated amplicons [dissociation (melt) temperature (T(m)), length, and DNA sequence]. The research presented herein tests the hypothesis that the SYBR PCR protocol is as sensitive as conventional culture for the detection of Mycoplasma spp. in bulk tank milk samples. Mycoplasmas cause several important disease syndromes in cattle, including mastitis in dairy cows. The standard diagnostic method at the herd level has been microbial isolation of mycoplasmas on 1 of several specialized media and speciation through biochemical or immunological techniques; repeated sampling schemes are recommended. The development of a real-time SYBR PCR protocol offers advantages in decrease of time to detection, cost, and complexity. The T(m) of the double-stranded DNA generated from the PCR reaction was used to detect the presence of and tentatively identify the species of mycoplasmas other than Mycoplasma bovis. In the SYBR PCR protocol, the presence of multiple species of mycoplasmas is indicated by an atypical dissociation curve. Gel electrophoresis and sequencing of the amplicons was used to confirm the mycoplasma species present when a non-M. bovis organism was detected (T(m) not equal to M. bovis) and used to identify all the mycoplasma species present for the samples with atypical dissociation curves. Mycoplasma bovis was identified in 83% of SYBR PCR mycoplasma-positive bulk tank samples. Another mycoplasma was identified either alone or in addition to M. bovis in 25% of SYBR PCR mycoplasma-positive bulk tank milk samples. Four species of mycoplasma other than M. bovis (Mycoplasma alkalescens, Mycoplasma arginini, Mycoplasma bovigenitalium, and Mycoplasma gateae) were identified in bulk tank milk samples tested with this method. Five farms had 2 mycoplasma species occurring at different times in their bulk tanks. Two mycoplasma species were identified in the same bulk tank sample in 7 instances on 2 farms. The finding of multiple Mycoplasma spp. coexisting on a farm and even in the same bulk tank milk sample indicates that the clinical significance of multiple mycoplasma species in the pathology of intramammary infections should be investigated further. In comparison with conventional culture, the SYBR PCR protocol was slightly (but not statistically significantly) more sensitive in the detection of mycoplasmas in bulk tank milk.

A simplified PCR assay for fast and easy mycoplasma mastitis screening in dairy cattle

A simplified polymerase chain reaction (PCR) assay was developed for fast and easy screening of mycoplasma mastitis in dairy cattle. Species of major mycoplasma strains [Mycoplasma (M.) bovis, M. arginini, M. bovigenitalium, M. californicum, M. bovirhinis, M. alkalescens and M. canadense] in cultured milk samples were detected by this simplified PCR-based method as well as a standard PCR technique. The minimum concentration limit for detecting mycoplasma by the simplified PCR was estimated to be about 2.5 × 10³ cfu/mL and was similar to that of the standard PCR. We compared the specificity and sensitivity of the simplified PCR to those of a culture method. Out of 1,685 milk samples cultured in mycoplasma broth, the simplified PCR detected Mycoplasma DNA in 152 that were also positive according to the culture assay. The sensitivity and specificity of the simplified PCR were 98.7% and 99.7%, respectively, for detecting mycoplasma in those cultures. The results obtained by the simplified PCR were consistent with ones from standard PCR. This newly developed simplified PCR, which does not require DNA purification, can analyze about 300 cultured samples within 3 h. The results from our study suggest that the simplified PCR can be used for mycoplasma mastitis screening in large-scale dairy farms.

Risk of Mycoplasma bovis transmission from contaminated sand bedding to naive dairy calves

The objective of this study was to evaluate the possible transmission of Mycoplasma bovis from positive sand bedding to naïve dairy calves. Twelve preweaned Holstein bull calves were blocked in pairs and randomly assigned as unexposed controls (n = 6) bedded with control sand, or exposed calves (n = 6) bedded with sand previously positive for M. bovis at a dairy farm. Bedding sand was cultured weekly. Nasal and ear swabs and sera were collected weekly, tracheal swabs were collected monthly, and by the end of the 105-d study, all calves were euthanized (n = 10) or died (n = 2). Sera were tested for M. bovis-specific antibody. Mycoplasma spp. culture was performed on nasal and ear swabs; culture and a PCR differentiating multiple Mycoplasma spp. were performed on postmortem samples of lung, retropharyngeal lymph node, and trachea from each calf. A complete necropsy also was performed. During 6 wk, mycoplasma concentration in exposed group sand was between 200 and 32,000 cfu/g. All 166 tracheal swabs, nasal and ear swabs, and postmortem tests from all calves were negative for mycoplasma. All 94 sera were negative for M. bovis-specific antibody. No gross pathology suggestive of mycoplasma disease was detected. The probability of mycoplasma detection, if an exposed calf had become infected 4 wk after exposure, ranged between 97 and 99% depending on time of exposure for individual calves. There was no evidence that sand bedding contaminated with M. bovis might serve as a source of transmission to naïve dairy calves.

Mycoplasma bovis real-time polymerase chain reaction assay validation and diagnostic performance

Mycoplasma bovis is an important bacterial pathogen in cattle, producing a variety of clinical diseases. The organism, which requires specialized culture conditions and extended incubation times to isolate and identify, is frequently associated with concurrent infection with other pathogens which can potentially be more easily identified. Real-time polymerase chain reaction (real-time PCR) is a valuable diagnostic technique that can rapidly identify infectious agents in clinical specimens. A real-time PCR assay was designed based on the uvrC gene to identify M. bovis in diagnostic samples. Using culture as the gold standard test, the assay performed well in a variety of diagnostic matrices. Initial validation testing was conducted on 122 milk samples (sensitivity: 88.9% [95% confidence interval (CI): 68.4-100%], specificity: 100%); 154 lung tissues (sensitivity: 89.0% [95% CI: 83.1-94.9%], specificity: 97.8% [95% CI: 93.5-100%]); 70 joint tissue/fluid specimens (sensitivity: 92.3% [95% CI: 82.1-100%], specificity: 95.5% [95% CI: 89.3-100%]); and 26 nasal swabs (sensitivity: 75.0% [95% CI: 45.0-100%], specificity: 83.3% [95% CI: 66.1-100%]). Low numbers of other sample matrices showed good agreement between results of culture and PCR. A review of clinical cases from 2009 revealed that, in general, PCR was used much more frequently than culture and provided useful diagnostic information in conjunction with clinical signs, signalment, and gross and histopathologic lesions. Diagnostic performance of the real-time PCR assay developed as a testing method indicates that it is a rapid, accurate assay that is adaptable to a variety of PCR platforms and can provide reliable results on an array of clinical samples.

Detection of bacterial and viral organisms from the conjunctiva of cats with conjunctivitis and upper respiratory tract disease

A variety of pathogens are involved in conjunctivitis in cats. In this study, the prevalence of feline herpesvirus (FHV), Chlamydophila felis, mycoplasmas, and aerobic bacteria on the conjunctival surface of cats with conjunctivitis and upper respiratory tract disease was investigated by polymerase chain reaction (PCR), immunofluorescent assay (IFA), and aerobic bacterial culture of ocular swabs. Forty-one cats were included of which 37 were found to be infected with an ocular organism. Single and multiple infections were present in 15 and 22 cats, respectively. FHV, mycoplasmas, and C felis were detected by PCR in 11 (27%), 20 (49%), and 23 (56%) cats, respectively. IFA detected 10 cats as positive for C felis. Mycoplasma felis, Mycoplasma canadense, Mycoplasma cynos, Mycoplasma gateae, Mycoplasma lipophilum, and Mycoplasma hyopharyngis were identified by genetic sequencing. The most common aerobic bacteria cultured included Staphylococcus species, Streptococcus species and Micrococcus species. The prevalence of mycoplasmas in cats with conjunctivitis was higher than previously reported, and four of the Mycoplasma species have not been described in cats so far.

Survey of bulk tank milk in New Zealand for Mycoplasma bovis , using species-specific nested PCR and culture

AIM

To survey the dairy cattle population in New Zealand for the presence or absence of Mycoplasma bovis.

METHODS

A random cross-sectional survey of bulk tank milk from dairy herds in New Zealand based on regionally proportioned sampling, weighted towards herds with a high bulk tank milk somatic cell count (SCC) was used to detect M. bovis at a between-herd prevalence of 2%, with 99% confidence. Bulk tank milk samples collected on-farm were tested using a nested M. bovis PCR, and bacteriological culture employing enrichment in mycoplasma broth and direct plating onto mycoplasma agar.

RESULTS

Mycoplasma bovis was not detected in any of the 244 bulk tank milk samples by either PCR or culture.

CONCLUSIONS

This survey provides further evidence that M. bovis is not present in the dairy cattle population in New Zealand.

Mastitis diagnostics and performance monitoring: a practical approach

In this paper a review is given of frequently used mastitis diagnostic methods in modern dairy practice. Methods used at the quarter, cow, herd and regional or national level are discussed, including their usability for performance monitoring in udder health. Future developments, such as systems in which milk-derived parameters are combined with modern analytical techniques, are discussed. It is concluded that, although much knowledge is available and science is still developing and much knowledge is available, it is not always fully exploited in practice.

Biological enrichment of Mycoplasma agents by cocultivation with permissive cell cultures

In this study, we describe our results on the evaluation of the ability of different permissive mammalian cell lines to support the biological enrichment of mycoplasma species known to be bacterial contaminants of cell substrates. The study showed that this approach is able to significantly improve the efficiency of mycoplasma detection based on nucleic acid testing or biochemical technologies (e.g., MycoAlert mycoplasma detection). Of 10 different cell lines (Vero, MDBK, HEK-293, Hep-G2, CV-1, EBTr, WI-38, R9ab, MDCK, and High Five) used in the study, only MDCK cell culture was found to support the efficient growth of all the tested mycoplasmas (Mycoplasma arginini, M. bovis, M. fermentans, M. gallinaceum, M. gallisepticum, M. synoviae, M. hominis, M. hyorhinis, M. orale, M. salivarium, and Acholeplasma laidlawii) known to be most frequently associated with contamination of cell substrates and cell lines in research laboratories or manufacturing facilities. The infection of MDCK cells with serial dilutions of each mycoplasma species demonstrated that these common cell line contaminants can be detected reliably after 7-day enrichment in MDCK cell culture at contamination levels of 0.05 to 0.25 CFU/ml. The High Five insect cell line was also found to be able to support the efficient growth of most mycoplasma species tested, except for M. hyorhinis strain DBS1050. However, mycoplasma growth in insect cell culture was demonstrated to be temperature dependent, and the most efficient growth was observed when the incubation temperature was increased from 28 degrees C to between 35 and 37 degrees C. We believe that this type of mycoplasma enrichment is one of the most promising approaches for improving the purity and safety testing of cell substrates and other cell-derived biologics and pharmaceuticals.

Prevalence of selected infectious organisms and comparison of two anatomic sampling sites in shelter cats with upper respiratory tract disease

In order to describe the isolation rates of potential pathogens and to compare anatomic sampling site suitability, nasal and pharyngeal swabs were taken from cats with acute clinical upper respiratory disease in a humane society. DNA of feline herpesvirus-1 was amplified from 51 of 52 cats sampled, Mycoplasma species were cultured or detected by PCR in samples from 34 of 42 cats sampled for both culture and PCR, and Bordetella bronchiseptica was isolated from three of 59 cats sampled for aerobic culture. A single swab was positive for calicivirus and no swabs were positive for Chlamydophila felis. Mycoplasma, Pasteurella and Moraxella species were all isolated from at least one cat in which no primary pathogen was identified. With the exception of B. bronchiseptica, which was detected in nasal swabs only, recovery rates for all suspect primary pathogens were comparable between sampling sites.

Prevalence of feline herpesvirus 1, Chlamydophila felis, and Mycoplasma spp DNA in conjunctival cells collected from cats with and without conjunctivitis

OBJECTIVE

To use PCR assays to determine the prevalence of feline herpesvirus 1 (FHV-1), Chlamydophila felis, and Mycoplasma spp DNA in conjunctival cells collected from cats with and without conjunctivitis; to compare results of conventional and real-time fluorogenic PCR assays for amplification of FHV-1 DNA; and to determine whether copy numbers of FHV-1 DNA are correlated with conjunctivitis.

ANIMALS

55 cats with active conjunctivitis, 39 healthy cats that never had conjunctivitis, and 32 cats with a history of conjunctivitis that had been resolved for at least 3 months.

PROCEDURES

Samples were obtained by rolling cotton-tipped applicators on the ventral conjunctiva of awake cats treated topically with proparacaine. The DNA was extracted from the swab specimens and assessed in PCR assays to detect DNA of FHV-1 (fluorogenic PCR assay and conventional PCR assay), Mycoplasma spp (conventional PCR assay), and C felis (conventional PCR assay).

RESULTS

Overall prevalence rates of FHV-1, C felis, and Mycoplasma spp as assessed by the conventional PCR assays were 6.7%, 3.2%, and 9.6%, respectively. Percentage concordance between conventional PCR and fluorogenic PCR assays for FHV-1 was 92.5%. There were no significant differences among the 3 groups of cats for the mean copy number of FHV-1 divided by the copy number of glyceraldehyde-3-phosphate dehydrogenase.

CONCLUSIONS AND CLINICAL RELEVANCE

Mycoplasma spp were the most prevalent organism detected and was associated with conjunctivitis. This study could not confirm that there are increased copy numbers of FHV-1 DNA in cats with conjunctivitis, compared with the copy numbers for cats without conjunctivitis.

Unusual history and initial clinical signs ofMycoplasma bovismastitis and arthritis in first-lactation cows in a closed commercial dairy herd

CASE DESCRIPTION

9 first-lactation dairy cows in a closed dairy herd had swelling in the forelimbs and forelimb lameness. Mycoplasmal arthritis and mastitis were diagnosed.

CLINICAL FINDINGS

Swelling of the carpal joint, diffuse subcutaneous edema from the carpal to metacarpophalangeal joints, and forelimb lameness were evident in 9 first-lactation cows 7 to 21 days after parturition. Diagnostic testing revealed that 3 of 3 bulk-tank milk samples, 3 milk samples from cows with clinical mastitis, 2 fluid samples obtained from arthritic joints, and samples from the lungs and spleen of a cow that had died yielded positive results for Mycoplasma spp. Nucleic acid sequence analysis performed by use of a PCR assay on the joint fluid and lung tissues confirmed infection with Mycoplasma bovis.

TREATMENT AND OUTCOME

Affected cows were treated by IM administration of flunixin meglumine and dexamethasone for 3 days. All cows were nonresponsive to treatment (3 cows died, and the other 6 were culled). Follow-up culture for Mycoplasma spp of milk samples from the bulk tank and from all lactating cows was recommended to screen for chronic subclinical carriers.

CLINICAL RELEVANCE

Mycoplasmal infections may cause unusual initial clinical signs or an atypical history. When dairy cattle, including those residing in closed herds, have lameness, swelling of the carpal or metacarpophalangeal joints, edema of the distal portions of the forelimbs, or polyarthritis, infection with Mycoplasma spp should be investigated. Delay in diagnosis of mycoplasmal infections in dairy herds can result in substantial financial loss and the establishment of chronic subclinical carriers.

Mycoplasma Mastitis: A Review of Transmission and Control

The Mycoplasma sp. that cause mastitis are simple, cell wall-less, bacteria that can colonize and cause diseases in other extramammary sites in the bovine. Prevalence of mycoplasma mastitis appears to be increasing in many locations throughout the world. The best method to identify this group of pathogens is through direct culture on mycoplasma agar media. However, limitations with this culture procedure are the duration of culture, 10 days, special conditions required and thus added expense, and the lack of primary specificity to distinguish between true pathogens and commensal organisms. Thus culture of bulk tank milk samples has been advocated as a primary screening method to determine the mycoplasma status of a herd. This monitoring system is reasonably successful but the sensitivity of detection of Mycoplasma sp. in bulk tank milk is affected by a significant minority of cows that might shed the organism at levels below the threshold of detection. Contagious mastitis control procedures have been effective in controlling outbreaks of mycoplasma mastitis. Yet new methods of control might be warranted, methods that may prevent the outbreak. Current data suggests that a significant number of new outbreaks may occur via internal or animal-to-animal transmission of mycoplasma mastitis pathogens from asymptomatic carriers.

Development of a semi-nested PCR for the improved detection of Mycoplasma bovis from bovine milk and mucosal samples

A new forward primer, Mb-F, was designed to improve the sensitivity and reproducibility of the Mycoplasma bovis-specific PCR developed by Ghadersohi et al. [Vet. Microbiol. 56 (1997) 87] for testing clinical samples. A semi-nested (SN) PCR configuration was developed and this provided enhanced sensitivity and reproducibility. The detection limit of the SN PCR was in the range of 10-100cfu/ml and the correct amplicon was amplified from 9.15pg/microliter of total extracted DNA (mixture of M. bovis and bovine cellular DNA). A dot blot assay was also developed and compared with the SN PCR on a number of randomly selected milk and mucosal samples. The dot blot had the same level of detection as the SN PCR. The specificity of the SN configuration was confirmed by Southern blot analysis and automated sequencing of the PCR product. The results from the tests on the samples from cattle, together with those from sheep, provided evidence that M. bovis is host-specific and that most cattle are colonised. The assay was shown to be specific, sensitive and reproducible and could be used successfully to detect M. bovis directly from clinical material without pre-enrichment.

Detection of Mycoplasma bovis in preservative-treated field milk samples

Control of mycoplasmal mastitis requires individual cow milk sampling for culture and identification of Mycoplasma bovis. This sampling is time-consuming and expensive. Currently, some herds sample cows monthly with the dairy herd improvement (DHI) program, but a preservative is added to this milk that kills M. bovis. In this paper, a nested polymerase chain reaction (PCR) procedure that allows for rapid testing of preservative-treated milk is validated. The specificity of the nested PCR assay was confirmed by testing isolated nucleic acids of other organisms phylogenetically related to M. bovis or common to milk. A comparison against blind-passage culture on 53 field milk samples determined its sensitivity. Exposure of seeded milk samples to the procedure resulted in a sensitivity of 5.1 cfu equivalents per milliliter. Analysis of these results proved that the nested PCR assay was as sensitive as traditional culture and can be used on preservative-treated milk.