Characterization of a mycoplasma isolated from infectious bovine keratoconjunctivitis: M. bovoculi sp. nov

An Update on Novel Taxa and Revised Taxonomic Status of Bacteria Isolated from Domestic Animals Described in 2018 to 2021

Novel bacterial taxonomy and nomenclature revisions can have significant impacts on clinical practice, disease epidemiology, and veterinary microbiology laboratory operations. Expansion of research on the microbiota of humans, animals, and insects has significant potential impacts on the taxonomy of organisms of clinical interest. Implications of taxonomic changes may be especially important when considering zoonotic diseases. Here, we address novel taxonomy and nomenclature revisions of veterinary significance. Noteworthy discussion centers around descriptions of novel mastitis pathogens in Streptococcaceae, Staphylococcaceae, and Actinomycetaceae; bovine reproductive tract pathogens in Corynebacteriaceae; novel members of Mannheimia spp., Leptospira spp., and Mycobacterium spp.; the transfer of Ochrobactrum spp. to Brucella spp.; and revisions to the genus Mycoplasma.

Component Causes of Infectious Bovine Keratoconjunctivitis-Non-Moraxella Organisms in the Epidemiology of Infectious Bovine Keratoconjunctivitis

Infectious bovine keratoconjunctivitis (IBK) is a multifactorial disease complex caused by opportunistic pathogens, classically those members of the genus Moraxella. However, IBK in some situations is associated with other potentially pathogenic agents, which include Mycoplasma bovoculi, Mycoplasma bovis, Ureaplasma diversum, bovine herpesviruses, and Chlamydia sp. Ocular infections that may resemble IBK are also caused by Listeria monocytogenes. These agents and their association with IBK are reviewed in this article.

Mycoplasma bovis and other Mollicutes in replacement dairy heifers from Mycoplasma bovis-infected and uninfected herds: A 2-year longitudinal study

Replacement dairy heifers exposed to Mycoplasma bovis as calves may be at risk of future clinical disease and pathogen transmission, both within and between herds; however, little information is available about these risks. We conducted a 2-yr longitudinal (panel) study starting with 450 heifer calves reared to weaning in 8 herds (7 M. bovis infected with clinical disease, 1 uninfected) under the same ownership. After weaning, heifers were commingled and managed with non-study heifers at a single heifer rearing facility. Nose, conjunctival, and vaginal swabs were collected along with a blood sample at weaning, prebreeding, precalving, and approximately 1 mo postcalving. Additionally, a colostrum sample was collected upon calving and a composite milk sample was collected 1 mo postcalving. The swabs, colostrum, and milk samples were cultured for Mycoplasma spp., and serum from the blood was evaluated for serological evidence of exposure to M. bovis using an ELISA. Despite a high M. bovis ELISA seroprevalence at weaning in the heifers from the 7 M. bovis-infected herds with clinical disease [72% (289/400); range by herd: 28-98%], M. bovis was isolated from only 4% (16/400) of the same heifers at the same time. In heifers from the uninfected herd at weaning, M. bovis seroprevalence was 2% (1/50) and M. bovis was not detected by culture. Mycoplasma bovis was isolated from 0.5% (2/414) of heifers at prebreeding, 0% (0/374) of heifers at precalving, and 0.3% (1/356) of heifers 1 mo postcalving. The nose was the predominant anatomical site of M. bovis colonization (74%; 14/19 culture positives). A single heifer (from an M. bovis-infected herd with clinical disease) was repeatedly detected with M. bovis in its nose at weaning, prebreeding, and postcalving samplings. This demonstrates the possibility, albeit rare, of a long-term M. bovis carrier state in replacement heifers exposed to M. bovis as calves, up to at least 1 mo after entry into the milking herd. No M. bovis clinical disease was detected in any heifer from weaning through to the end of the study (approximately 1 mo after calving). Acholeplasma spp. were commonly isolated throughout the study. Mycoplasma bovigenitalium, Mycoplasma bovoculi, and Mycoplasma bovirhinis were isolated infrequently. Mycoplasma bovis seroprevalences at prebreeding, precalving, and postcalving samplings were 27% (112/414), 12% (46/374), and 18% (65/356), respectively. Overall, the results show that replacement heifers from groups exposed to M. bovis preweaning can become colonized with M. bovis and that colonization can, uncommonly, be present after their first calving. For groups of 50 or more heifers exposed to M. bovis preweaning, there is at least a nontrivial probability that the group will contain at least 1 shedding heifer postcalving.

Swine conjunctivitis outbreaks associated with Mycoplasma hyorhinis

Conjunctivitis is an uncommon finding in commercial swine herds, and the etiology of the disease is rarely studied. We investigated cases of conjunctivitis in 3 wean-to-finish swine farms. Eye swabs and tissues were obtained from clinically affected pigs (8-22 wk of age), from unaffected pigs in contact with affected pen-mates, and from age-matched pigs from an unaffected herd. Real-time PCR (rtPCR) testing for Mycoplasma hyorhinis demonstrated consistent detection and high bacterial load in samples from affected herds (clinically affected animals and non-clinical pen-mates). Ct values in affected pigs were 18.9-25.3; values were 36.4-38.6 in unaffected pigs from unaffected herds. Additionally, M. hyorhinis was identified within inflamed palpebral conjunctivae by in situ hybridization. The association of rtPCR and in situ detection of M. hyorhinis, along with the lack of detection of other potential pathogens and noninfectious causes, suggests the involvement of M. hyorhinis in the etiology and pathogenesis of the reported swine conjunctivitis.

Phylogenetic framework for the phylum Tenericutes based on genome sequence data: proposal for the creation of a new order Mycoplasmoidales ord. nov., containing two new families Mycoplasmoidaceae fam. nov. and Metamycoplasmataceae fam. nov. harbouring Eperythrozoon, Ureaplasma and five novel genera

The genus Mycoplasma, including species earlier classified in the genera Eperythrozoon and Haemobartonella, contains ~ 120 species and constitutes an extensively polyphyletic assemblage of bacteria within the phylum Tenericutes. Due to their small genome sizes and lack of unique characteristics, the relationships among the mycoplasmas/Tenericutes are not reliably discerned. Using genome sequences for 140 Tenericutes, their evolutionary relationships were examined using multiple independent approaches. Phylogenomic trees were constructed for 63 conserved proteins, 45 ribosomal proteins, three main subunits of RNA polymerase and 16S rRNA gene sequences. In all of these trees, Tenericutes species reliably grouped into four main clades designated as the "Acholeplasma", "Spiroplasma", "Pneumoniae" and "Hominis" clusters. These clades are also distinguished based on a similarity matrix constructed based on 16S rRNA gene sequences. Mycoplasma species were dispersed across 3 of these 4 clades highlighting their extensive polyphyly. In parallel, our comparative genomic analyses have identified > 100 conserved signature indels (CSIs) and 14 conserved signature proteins (CSPs), which are uniquely shared by the members of four identified clades, strongly supporting their monophyly and identifying them in molecular terms. Mycoplasma mycoides, the type species of the genus Mycoplasma, and a small number of other Mycoplasma species, formed a strongly supported clade within the "Spiroplasma" cluster. Nine CSIs and 14 CSPs reliably distinguish this clade from all other Mycoplasmatales species. The remainder of the Mycoplasmatales species are part of the "Pneumoniae" and "Hominis" clusters, which group together in phylogenetic trees. Here we are proposing that the order Mycoplasmatales should be emended to encompass only the Mycoplasma species within the "Spiroplasma" cluster and that a new order, Mycoplasmoidales ord. nov., should be created to encompass the other Mycoplasma species. The "Pneumoniae" and the "Hominis" clusters are proposed as two new families, Mycoplasmoidaceae fam. nov., which includes the genera Eperythrozoon, Ureaplasma, and the newly proposed genera Malacoplasma and Mycoplasmoides, and Metamycoplasmataceae fam. nov. to contain the newly proposed genera Metamycoplasma, Mycoplasmopsis, and Mesomycoplasma. The results presented here allow reliable discernment, both in phylogenetic and molecular terms, of the members of the two proposed families as well as different described genera within these families including members of the genus Eperythrozoon, which is comprised of uncultivable organisms. The taxonomic reclassifications proposed here, which more accurately portray the genetic diversity among the Tenericutes/Mycoplasma species, provide a new framework for understanding the biological and clinical aspects of these important microbes.

Molecular and Antigenic Characterization of a Mycoplasma Bovis Strain Causing an Outbreak of Infectious Keratoconjunctivitis

An unusually high incidence of infectious keratoconjunctivitis followed by pneumonia and arthritis was observed in beef calves of a managed herd. No Moraxella spp. or bacteria other than Mycoplasma spp. were obtained from conjunctival and nasal swabs. A strategy was designed for characterization of bovine mycoplasmas at species and strain level on the basis of a combination of molecular tools and the immunoblotting method. The strategy made it possible to rapidly assign the bacterium responsible for this outbreak to one of the phylogenetic clusters of bovine mycoplasmas delineated in this study and then to identify it as Mycoplasma bovis. The strain, designated Sar 1, showed a 100% 16S rDNA sequence identity with two European strains (120/81 and MC3386) isolated in Germany and Ireland, respectively, and hosts a vsp gene analog to the vspA, vsp422-4, and vsp422-8 genes of the M. bovis reference strain PG45T and of the field strain 422. The use of a cross-reactive rabbit serum developed against the Mycoplasma agalactiae immunodominant antigen P48 confirmed the molecular findings. The immunological response of calves against M. bovis was also investigated. This is the first report on the occurrence of M. bovis on the Island of Sardinia (Italy).

Point prevalence of infection with Mycoplasma bovoculi and Moraxella spp. in cattle at different stages of infectious bovine keratoconjunctivitis

Infectious bovine keratoconjunctivitis (IBK) has significant economic consequences and a detrimental impact on animal welfare. Although Moraxella (Mor.) bovis is the primary causative agent, the role of other bacteria, such as Mor. ovis, Mor. bovoculi and Mycoplasma (Myc.) bovoculi, is not well understood. To assess the prevalence of infection with these organisms, and to correlate this with outbreaks of IBK, conjunctival samples from four herds of cattle in Germany of differing IBK status were examined. Herds were selected to represent a hypothetical course of IBK ranging from the pre-outbreak stage (herd 1), to the acute disease stage (herd 2), to a stage where treatment had ceased (herd 3). Unaffected animals were also included (herd 4). To facilitate effective, sensitive sample analysis, a new real-time PCR for Myc. bovoculi was developed and used in concert with established real-time PCR protocols for Myc. bovis and Moraxella spp. Herds 1 and 2 showed similarly high rates of detection for Myc. bovoculi (92.5% and 84.0%, respectively), whereas herds 3 and 4 had a lower prevalence (35.5% and 26.2%, respectively). Mor. bovis and Mor. ovis were more prevalent in herd 1 (32.5% and 87.5%, respectively) and herd 2 (38% and 58%, respectively) than herd 3 (10.4% and 1.3%, respectively) and herd 4 (9.8% and 31.1%, respectively). Mor. bovoculi was the only pathogen that correlated with clinical signs of IBK; at 20% prevalence, it was almost exclusively detected in herd 2. The results indicate that herds with high Myc. bovoculi prevalence are more predisposed to outbreaks of IBK, possibly due to a synergistic interaction with Moraxella spp.

Complete Genome Sequence of Mycoplasma bovoculi Strain M165/69T (ATCC 29104)

Bovine ocular infections compromise animal health and result in significant economic losses. Mycoplasma bovoculi is an etiological agent of conjunctivitis. Presented here is the 760,240-bp complete genome sequence of the M. bovoculi type strain M165/69(T). An analysis of the deduced proteome provides insights into the adherence and antigenic variation mechanisms of the strain.

Identification and localization of a 94 kDa membrane protein found in Mycoplasma bovoculi strains

Six isolates of Mycoplasma bovoculi obtained from cattle herds with bovine keratoconjunctivitis were analyzed by gel electrophoresis and immunoblotting techniques. All six strains showed similarity in their protein profiles although no two patterns were identical. Antigenic differences between strains were detected in immunoblots reacted with post-exposure calf serum. A common 94 kDa protein band designated p94 was detected in all six strains reacted with monoclonal antibody MA25.5 developed to one of the strains. The p94 was also recognized in these strains by the calf serum. Trypsin treatment of intact mycoplasma cells resulted in the removal of p94 from immunoblots reacted with MA or hyperimmune rabbit serum. Other trypsin-resistant antigens shared between strains or being strain-specific in nature were identified when trypsin-treated mycoplasma cells were reacted with hyperimmune rabbit serum. The p94 antigen was shown to be of mycoplasmal origin by radio-immunoprecipitation using the MA or hyperimmune rabbit serum. These studies identify the presence of a surface antigen (p94) on M. bovoculi membrane in all strains examined that is trypsin sensitive by the use of monoclonal antibody, calf serum and hyperimmune rabbit serum.

Antibody response in calves experimentally or naturally exposed to Mycoplasma bovoculi

An antiglobulin-ELISA has been developed to detect antibody activity to Mycoplasma bovoculi in sera, nasal fluids and lacrimal fluids of field and experimentally exposed calves. Low IgG activity with no IgM or IgA was detected in sera of experimental calves. In nasal and lacrimal fluids, IgA appeared as early as the first week following exposure to M. bovoculi and predominated in both of these fluids throughout the 9 wk observation period. Sera from field-exposed animals showed high IgG and IgM activities. The metabolic-inhibition (MI) test was applied to detect growth inhibition of M. bovoculi in those fluids. This property was found only in sera of exposed animals and thus could be used to test for M. bovoculi infection. The ELISA test and the MI test were considered reliable tests for the detection of antibodies to M. bovoculi infection. The implications of finding no growth-inhibiting activity in nasal and lacrimal fluids concurrent with a high IgA activity are discussed.

Epidemic caprine keratoconjunctivitis: recovery of Mycoplasma conjunctivae and its possible role in pathogenesis

Clinical, microbiological, serological, histological, and therapeutic aspects of two separate outbreaks of caprine keratoconjunctivitis are described. The disease was characterized by a high rate of contagion, rapid onset, intense lacrimation, conjunctival hyperemia, and corneal opacity with neovascularization. In addition, many of the animals developed respiratory illness during the second epidemic. The only organism consistentlyisolated was Mycoplasma conjunctivae. A total of 23 strains were isolated from 18 inflamed conjunctivae, one normal conjunctiva, and the nasal secretions of four goats with concomitant respiratory illness. The convalescent sera of goats in the first outbreak had neutralizing antibody titers to M. conjunctivae that ranged from 1:32 to 1:256. In the milder second outbreak the antibody titers ranged from 1:4 to 1:32 in animals with only ocular disease and from 1:4 to 1:64 in animals with only respiratory disease. Whereas little change was noted in antibody titers of goats with only localized eye disease, 43% of the goats with respiratory disease showed significant fourfold rises. The histological picture was consistent with acute corneal infection. Animals requiring antibiotic treatment appeared to respond favorably to a combination of oxytetracycline and polymyxin B, but not to penicillin. These findings suggest that M. conjunctivae is one cause of epidemic caprine keratoconjunctivitis.

Rapid detection of bovine mycoplasma antigens by counterimmunoelectrophoresis

Twelve reference strains of mycoplasma and acholeplasma previously reported to have been recovered from cattle were tested against hyperimmune rabbit serum by counterimmunoelectrophoresis. This technique detected antigen by the formation of precipitin lines with antibody within 1 h and promises to be a useful technique for detecting and identifying mycoplasma isolates in either pure or mixed cultures.