In vitro antimicrobial susceptibility of Mycoplasma bovis isolated in Israel from local and imported cattle

Use of recombinant proteins for the diagnosis and prevention of Mycoplasma bovis: a systematic review

Introduction

Mycoplasma bovis is a highly contagious pathogen that causes various diseases in herd animals, negatively impacting reproduction, production, and milk yield. Effective diagnostic methods and vaccine development are critical for controlling M. bovis outbreaks. This systematic review aimed to evaluate diagnostic alternatives and vaccine compounds based on recombinant proteins.

Methods

Following the PRISMA protocol, a systematic search was conducted in the SciELO, PubMed, and CAPES Periodicals Portal databases. Inclusion criteria included studies published between 2008 and 2023 that involved (1) the use of recombinant proteins for M. bovis identification or vaccine production, (2) biological samples, (3) availability in the selected databases, (4) in vitro or in vivo experimental designs, and (5) English-language publications.

Results

Ten of the initial 53 studies screened met the inclusion criteria. Of these, four studies focused on diagnostic approaches and six on vaccine development. Diagnostic studies predominantly used an indirect enzyme-linked immunosorbent assay (ELISA) with recombinant proteins, achieving over 90% sensitivity and specificity in detecting M. bovis infections. In contrast, the development of recombinant vaccines has shown limited success, with challenges in identifying effective adjuvants and optimizing conditions for protective immunity.

Discussion

While recombinant protein-based diagnostics have proven effective, developing a successful vaccine against M. bovis remains elusive. Further research is necessary to refine vaccine formulations, including selecting suitable adjuvants and challenge models to enhance protective efficacy against M. bovis infections.

Toward a Method for Harmonized Susceptibility Testing of Mycoplasma bovis by Broth Microdilution

Mycoplasma bovis is a fastidious pathogen of cattle causing massive economic losses in the calf and dairy industries worldwide. Since there is no approved standard method for antimicrobial susceptibility testing (AST) of M. bovis, the Clinical and Laboratory Standards Institute has requested the development of a suitable method. Therefore, this study aimed at developing a method for harmonized broth microdilution AST of M. bovis. For this, 131 M. bovis field isolates and M. bovis strain DSM 22781T were collected and macrorestriction analysis was performed to select 15 epidemiologically unrelated M. bovis strains for method validation steps. To select a suitable broth for AST of M. bovis, growth determinations were performed using five media and growth curves were compiled. Then, susceptibility testing was performed considering the exact (precondition of five identical MICs) and essential (MIC mode, accepting a deviation of ±1 dilution step) MIC agreements to evaluate the reproducibility of MIC values using a panel of 16 antimicrobial agents. Subsequently, the remaining field isolates were tested and the suitability of quality control (QC) strains was assessed. Growth experiments showed that SP4 broth was the only one of the five media that yielded sufficient growth of M. bovis. Therefore, it was selected as the test medium for AST and homogeneous MIC values were obtained (exact and essential agreements of 36 to 100% and 92 to 100%, respectively). For all other isolates tested, easy-to-read MIC endpoints were determined with this medium. High overall MIC50 and/or MIC90 values were observed for aminoglycosides and macrolides, and some isolates showed elevated MICs of fluoroquinolones, gentamicin, and/or tiamulin. Since the MICs of four commonly used QC strains were partially not within their ranges, a 20-fold MIC testing of M. bovis DSM 22781T was performed and met the criteria for a new QC strain. For harmonized AST of M. bovis, SP4 broth seems to be suitable with an incubation time of 72 ± 2 h and further validation of M. bovis DSM 22781T as a future QC strain is recommended.

Prevalence and Antimicrobial Susceptibility of Bovine Mycoplasma Species in Egypt

Simple Summary

Bovine Mycoplasma species, particularly antimicrobial resistant Mycoplasma bovis are important causes of bovine respiratory disease (BRD) in cattle, which causes major economic losses worldwide. Thus, the current study aimed to determine the prevalence and antimicrobial resistance profiles of bovine Mycoplasma spp. isolated from cattle’s respiratory tracts, in addition to evaluating the fluoroquinolone resistance in the recovered isolates using broth microdilution and conventional PCR techniques in Egypt. Our result showed that M. bovis was the most common spp. (61%), followed by M. bovirhinis (15%). In total, mycoplasma isolates were more prevalent among all examined lung tissues (38%), followed by nasal swabs (35%), tracheal tissues (28%), and tracheal swabs (27%). All the examined mycoplasma isolates (n = 76) were 100% susceptible to spectinomycin, tulathromycin, spiramycin, and tylosin, but high doxycycline and enrofloxacin minimum inhibitory concentrations (MICs) values were observed among 43.4% and 60.5% of the tested isolates, respectively. Three and two mycoplasma isolates with high enrofloxacin MICs were confirmed to be M. bovis and M. bovirhinis, respectively, by PCR assays. All molecularly confirmed mycoplasma isolates (n = 5) were positive for the gyrA gene (100%), meanwhile, three isolates (60%) were positive for the parC gene. In conclusion, understanding antimicrobial resistance mechanisms is a significant tool for the future development of genetic-based diagnostic techniques for the rapid detection of resistant mycoplasma strains.

Abstract

Among many bovine Mycoplasma species (spp.), Mycoplasma bovis is recognized as a significant causative agent of respiratory diseases in cattle. In recent years, resistant M. bovis isolates, especially to fluoroquinolones, have been reported globally as a result of the extensive usage of antimicrobials in the treatment of bovine pneumonia. Therefore, the aim of this study is to investigate the prevalence and antimicrobial susceptibility patterns of bovine Mycoplasma spp. isolated from the respiratory tracts of cattle in Egypt and to assess the fluoroquinolones resistance in the recovered mycoplasma isolates via broth microdilution and conventional PCR techniques. Conventional phenotypic methods identified 128 mycoplasma isolates (32%) from 400 different samples, with M. bovis being the predominant spp. (61%), followed by M. bovirhinis (15%). Of note, mycoplasma isolates were rarely isolated from total healthy lung tissues (7/55, 12.7%), but they were frequently isolated from pneumonic lungs (31/45, 68.9%). All the examined mycoplasma isolates (n = 76) were sensitive to tilmicosin, tylosin, tulathromycin, spiramycin, and spectinomycin (100% each), while 60.5% and 43.4% of the examined isolates had high minimum inhibitory concentration (MIC) values to enrofloxacin and doxycycline, respectively. Three and two mycoplasma isolates with high enrofloxacin MICs were confirmed to be M. bovis and M. bovirhinis, respectively, by PCR assays. All molecularly confirmed mycoplasma isolates (n = 5) were positive for the gyrA gene (100%); meanwhile, three isolates (60%) were positive for the parC gene. In conclusion, our findings revealed alarming resistance to enrofloxacin and doxycycline antibiotics; thus, antimicrobial usage must be restricted and molecular techniques can help in the rapid detection of the resistant strains.

Genome-Wide Association Study of Nucleotide Variants Associated with Resistance to Nine Antimicrobials in Mycoplasma bovis

Antimicrobial resistance (AMR) studies of Mycoplasma bovis have generally focused on specific loci versus using a genome-wide association study (GWAS) approach. A GWAS approach, using two different models, was applied to 194 Mycoplasma bovis genomes. Both a fixed effects linear model (FEM) and a linear mixed model (LMM) identified associations between nucleotide variants (NVs) and antimicrobial susceptibility testing (AST) phenotypes. The AMR phenotypes represented fluoroquinolones, tetracyclines, phenicols, and macrolides. Both models identified known and novel NVs associated (Bonferroni adjusted p < 0.05) with AMR. Fluoroquinolone resistance was associated with multiple NVs, including previously identified mutations in gyrA and parC. NVs in the 30S ribosomal protein 16S were associated with tetracycline resistance, whereas NVs in 5S rRNA, 23S rRNA, and 50S ribosomal proteins were associated with phenicol and macrolide resistance. For all antimicrobial classes, resistance was associated with NVs in genes coding for ABC transporters and other membrane proteins, tRNA-ligases, peptidases, and transposases, suggesting a NV-based multifactorial model of AMR in M. bovis. This study was the largest collection of North American M. bovis isolates used with a GWAS for the sole purpose of identifying novel and non-antimicrobial-target NVs associated with AMR.

Integrating the Human and Animal Sides of Mycoplasmas Resistance to Antimicrobials

Mycoplasma infections are frequent in humans, as well as in a broad range of animals. However, antimicrobial treatment options are limited, partly due to the lack of a cell wall in these peculiar bacteria. Both veterinary and human medicines are facing increasing resistance prevalence for the most commonly used drugs, despite different usage practices. To date, very few reviews have integrated knowledge on resistance to antimicrobials in humans and animals, the latest dating back to 2014. To fill this gap, we examined, in parallel, antimicrobial usage, resistance mechanisms and either phenotype or genotype-based methods for antimicrobial susceptibility testing, as well as epidemiology of resistance of the most clinically relevant human and animal mycoplasma species. This review unveiled common features and differences that need to be taken into consideration in a "One Health" perspective. Lastly, two examples of critical cases of multiple drug resistance are highlighted, namely, the human M. genitalium and the animal M. bovis species, both of which can lead to the threat of untreatable infections.

Antimicrobial Susceptibility of Mycoplasma bovis Isolates from Veal, Dairy and Beef Herds

Mycoplasma bovis is an important pathogen causing mostly pneumonia in calves and mastitis in dairy cattle. In the absence of an effective vaccine, antimicrobial therapy remains the main control measure. Antimicrobial use in veal calves is substantially higher than in conventional herds, but whether veal calves also harbor more resistant M. bovis strains is currently unknown. Therefore, we compared antimicrobial susceptibility test results of M. bovis isolates from different cattle sectors and genomic clusters. The minimum inhibitory concentration of nine antimicrobials was determined for 141 Belgian M. bovis isolates (29 dairy, 69 beef, 12 mixed, 31 veal farms), and was used to estimate the epidemiological cut-off. Acquired resistance was frequently observed for the macrolides, while no acquired resistance to oxytetracycline and doxycycline, minimal acquired resistance to florfenicol and tiamulin, and a limited acquired resistance to enrofloxacin was seen. M. bovis isolates from beef cattle or genomic cluster III had higher odds of being gamithromycin-resistant than those from dairy cattle or genomic clusters IV and V. In this study, no cattle industry could be identified as source of resistant M. bovis strains. A single guideline for antimicrobial use for M. bovis infections, with a small remark for gamithromycin, is likely sufficient.

Molecular characteristics and antibiotic susceptibility profiles of Mycoplasma bovis associated with mastitis on dairy farms in China

Mycoplasma bovis (M. bovis) is regarded as the most prevalent mycoplasma species causing bovine mastitis worldwide. This study was conducted with the objectives to: (1) estimate M. bovis prevalence in samples from clinical mastitis and bulk tank milk; (2) assess genetic diversity and population structure of isolates; and (3) determine antibiotic susceptibility of isolates to nine antimicrobials. Milk samples (n = 476), including 450 clinical mastitis and 26 bulk tank milk samples from 23 farms (each with >1000 lactating cows) in 10 provinces of China were collected between May 2018 and September 2019. M. bovis cultured from milk samples were analyzed by multi-locus sequence typing. Minimum inhibitory concentrations of all isolates to nine antimicrobials were determined. Differences in minimum inhibitory concentration values were assessed by Kruskal-Wallis test with Bonferroni correction. The positive proportions of M. bovis in clinical mastitis samples and bulk tank milk samples were 39/450 (8.7%) and 11/26 (42.3%), respectively. Based on multi-locus sequence typing, the 50 isolates were identified as three sequence types, including sequence type 10 and two novel sequence types (newly registered as sequence type 172 and sequence type 173). The most prevalent type, sequence type 172 (31/50, 62.0%), had allelic profile 4, 3, 2, 3, 5, 7, 4. In addition, sequence type 10 with allelic profile 4, 3, 2, 3, 5, 3, 4 had a mid-range prevalence (11/50, 22.0%), whereas sequence type 173 with allelic profile 10, 3, 6, 13, 21, 6, 10 was the least prevalent (8/50, 16.0%). Both sequence type 10 and sequence type 172 were clustered in Clonal Complex 3, with isolates from the USA. M. bovis isolates in this study uniformly had low level minimum inhibitory concentrations to enrofloxacin and tiamulin. Overall variances among isolates were significant (Kruskal-Wallis test) for clindamycin (P = 0.006), erythromycin (P = 0.012) and tylosin (P =0.004). Relative to the sequence type 10 group, there were higher minimum inhibitory concentrations levels for the sequence type 173 group (H = -19.795, P = 0.003, for clindamycin; H = -19.574, P = 0.003, for erythromycin; and H = -18.881, P = 0.003, for tylosin) by post-hoc comparisons using pairwise comparisons of mean ranks following Kruskal-Wallis test with Bonferroni correction. Hence, increasing antimicrobial resistance may have contributed to emergence of novel sequence types. These data provided a baseline for elucidating genetic diversity and antibiotic susceptibility profiles of M. bovis in the main dairy-farming provinces in China.

Investigation of Macrolide Resistance Genotypes in Mycoplasma bovis Isolates from Canadian Feedlot Cattle

Mycoplasma bovis is associated with bovine respiratory disease (BRD) and chronic pneumonia and polyarthritis syndrome (CPPS) in feedlot cattle. No efficacious vaccines for M. bovis exist; hence, macrolides are commonly used to control mycoplasmosis. Whole genome sequences of 126 M. bovis isolates, derived from 96 feedlot cattle over 12 production years, were determined. Antimicrobial susceptibility testing (AST) of five macrolides (gamithromycin, tildipirosin, tilmicosin, tulathromycin, tylosin) was conducted using a microbroth dilution method. The AST phenotypes were compared to the genotypes generated for 23S rRNA and the L4 and L22 ribosomal proteins. Mutations in domains II (nucleotide 748; E. coli numbering) and V (nucleotide 2059 and 2060) of the 23S rRNA (rrl) gene alleles were associated with resistance. All isolates with a single mutation at Δ748 were susceptible to tulathromycin, but resistant to tilmicosin and tildipirosin. Isolates with mutations in both domain II and V (Δ748Δ2059 or Δ748Δ2060) were resistant to all five macrolides. However, >99% of isolates were resistant to tildipirosin and tilmicosin, regardless of the number and positions of the mutations. Isolates with a Δ748 mutation in the 23S rRNA gene and mutations in L4 and L22 were resistant to all macrolides except for tulathromycin.

Mycoplasma bovis in Spanish Cattle Herds: Two Groups of Multiresistant Isolates Predominate, with One Remaining Susceptible to Fluoroquinolones

Mycoplasma bovis is an important bovine pathogen causing pneumonia, mastitis, and arthritis and is responsible for major economic losses worldwide. In the absence of an efficient vaccine, control of M. bovis infections mainly relies on antimicrobial treatments, but resistance is reported in an increasing number of countries. To address the situation in Spain, M. bovis was searched in 436 samples collected from beef and dairy cattle (2016–2019) and 28% were positive. Single-locus typing using polC sequences further revealed that two subtypes ST2 and ST3, circulate in Spain both in beef and dairy cattle, regardless of the regions or the clinical signs. Monitoring of ST2 and ST3 isolates minimum inhibitory concentration (MIC) to a panel of antimicrobials revealed one major difference when using fluoroquinolones (FQL): ST2 is more susceptible than ST3. Accordingly, whole-genome sequencing (WGS) further identified mutations in the gyrA and parC regions, encoding quinolone resistance-determining regions (QRDR) only in ST3 isolates. This situation shows the capacity of ST3 to accumulate mutations in QRDR and might reflect the selective pressure imposed by the extensive use of these antimicrobials. MIC values and detection of mutations by WGS also showed that most Spanish isolates are resistant to macrolides, lincosamides, and tetracyclines. Valnemulin was the only one effective, at least in vitro, against both STs.

Antimicrobial Sensitivity Testing of Mycoplasma bovis Isolates Derived from Western Canadian Feedlot Cattle

Mycoplasma bovis is particularly adept at evading the immune system, resulting in chronic infections of the lungs and joints of feedlot cattle. The chronicity of the lesions results in prolonged antimicrobial therapy, possibly exacerbating antimicrobial resistance. This cross-sectional study generated in vitro antimicrobial susceptibility testing (AST) data on 211 M. bovis isolates recovered from 159 healthy, diseased, and dead cattle, spanning the period of 2006-2018. Nine antimicrobials commonly administered to western Canadian feedlot cattle were assessed. The data were analyzed with non-parametric statistical tests with a level of significance of p < 0.05 (two-tailed). Minimum inhibitory concentration (MIC) values tended to increase between the isolates from healthy versus dead cattle and over time (2006-2018). Isolates from dead versus healthy cattle were more likely to be resistant to tulathromycin, gamithromycin, tylosin and enrofloxacin. There was no difference in the distributions of the MICs generated from the isolates recovered from the lungs and joints (p ≥ 0.124) and the lungs and deep nasal passages (p ≥ 0.157) of the same animals.

Relationship between Antimicrobial Susceptibility and Multilocus Sequence Type of Mycoplasma bovis Isolates and Development of a Method for Rapid Detection of Point Mutations Involved in Decreased Susceptibility to Macrolides, Lincosamides, Tetracyclines, and Spectinomycin

Mycoplasma bovis isolates belonging to the sequence type 5 (ST5) group, the dominant group in Japan since 1999, were low susceptible to 16-membered macrolides and tetracyclines and were confirmed to have a guanine-to-adenine transition mutation at position 748 in the 23S rRNA gene (rrl) and adenine-to-thymine transversion mutations at positions 965 and 967 in the 16S rRNA gene (rrs) (Escherichia coli numbering). Moreover, isolates of ST93 and ST155, members of the ST5 group, were low susceptible to lincosamides and azithromycin and showed an adenine-to-guanine transition mutation at position 2059 of rrl Isolates of ST93 were additionally low susceptible to spectinomycin and showed a cytosine-to-adenine transversion mutation at position 1192 of rrs Strains of the ST5 group seem to spread to Japan and Europe from North America with imported cows, while strains of ST93 and ST155 originated in Japan. Melting curve analysis using hybridization probes revealed the existence of point mutations involved in decreased susceptibility to macrolides, lincosamides, and spectinomycin, as demonstrated by changes in the melting curve shape and/or decreases in the melting peak temperature, so the susceptibility to these antimicrobials can be assessed on the same day. For decreased susceptibility to fluoroquinolones to exist, nonsynonymous mutations in the DNA gyrase gene (gyrA) and topoisomerase IV gene (parC) had to coexist. The combination of amino acid substitutions of serine at position 83 in gyrA and serine at position 80 in parC resulted in particularly low susceptibility to fluoroquinolones.IMPORTANCE Mycoplasma bovis is the main causal species of bovine mycoplasmal disease and leads to significant economic losses because of its severe symptoms, strong infectivity, and refractoriness. As for mastitis, culling cows with intramammary infections is a general countermeasure to prevent spreading. The conventional antimicrobial susceptibility test for mycoplasma is time-consuming and troublesome, but no quick and easy method for grasping the antimicrobial susceptibility of the causal strain exists at present. Treatment without antimicrobial susceptibility information may be one reason why M. bovis infection is refractory. Detecting a mutation involved in decreased susceptibility to antimicrobial agents of the causal strain makes it possible to easily select suitable antimicrobials for treatment, and this technique will help improve the cure rate and prevent the overuse of ineffective antimicrobial agents. In this study, we developed a technique to quickly and easily assess antimicrobial susceptibility based on the genetic characteristics of M. bovis strains in Japan.

Antimicrobial Resistance in Mycoplasma spp

Mycoplasmas are intrinsically resistant to antimicrobials targeting the cell wall (fosfomycin, glycopeptides, or β-lactam antibiotics) and to sulfonamides, first-generation quinolones, trimethoprim, polymixins, and rifampicin. The antibiotics most frequently used to control mycoplasmal infections in animals are macrolides and tetracyclines. Lincosamides, fluoroquinolones, pleuromutilins, phenicols, and aminoglycosides can also be active. Standardization of methods used for determination of susceptibility levels is difficult since no quality control strains are available and because of species-specific growth requirements. Reduced susceptibility levels or resistances to several families of antimicrobials have been reported in field isolates of pathogenic Mycoplasma species of major veterinary interest: M. gallisepticum and M. synoviae in poultry; M. hyopneumoniae, M. hyorhinis, and M. hyosynoviae in swine; M. bovis in cattle; and M. agalactiae in small ruminants. The highest resistances are observed for macrolides, followed by tetracyclines. Most strains remain susceptible to fluoroquinolones. Pleuromutilins are the most effective antibiotics in vitro. Resistance frequencies vary according to the Mycoplasma species but also according to the countries or groups of animals from which the samples were taken. Point mutations in the target genes of different antimicrobials have been identified in resistant field isolates, in vitro-selected mutants, or strains reisolated after an experimental infection followed by one or several treatments: DNA-gyrase and topoisomerase IV for fluoroquinolones; 23S rRNA for macrolides, lincosamides, pleuromutilins, and amphenicols; 16S rRNAs for tetracyclines and aminoglycosides. Further work should be carried out to determine and harmonize specific breakpoints for animal mycoplasmas so that in vitro information can be used to provide advice on selection of in vivo treatments.

Mycoplasma bovis isolates from dairy calves in Japan have less susceptibility than a reference strain to all approved macrolides associated with a point mutation (G748A) combined with multiple species-specific nucleotide alterations in 23S rRNA

Erythromycin, tylosin and tilmicosin are approved for use in cattle in Japan, the latter two being used to treat Mycoplasma bovis infection. In this study, 58 M. bovis isolates obtained from Japanese dairy calves all exhibited reduced susceptibility to these macrolides, this widespread reduced susceptibility being attributable to a few dominant lineages. All 58 isolates contained the G748A variant in both the rrl3 and rrl4 alleles of 23S rRNA, whereas a reference strain (PG45) did not. G748 localizes in the central loop of domain II (from C744 to A753) of 23S rRNA, which participates in binding to mycinose, a sugar residue present in both tylosin and tilmicosin. A number of in vitro-selected mutants derived from M. bovis PG45 showed reduced susceptibility to tylosin and tilmicosin and contained a nucleotide insertion within the central loop of domain II of rrl3 (U747-G748Ins_CU/GU or A743-U744Ins_UA), suggesting that mutations around G748 confer this reduced susceptibility phenotype. However, other Mycoplasma species containing G748A were susceptible to tylosin and tilmicosin. Sequence comparison with Escherichia coli revealed that M. bovis PG45 and isolates harbored five nucleotide alterations (U744C, G745A, U746C, A752C and A753G) in the central loop of domain II of 23S rRNA, whereas other Mycoplasma species lacked at least two of these five nucleotide alterations. It was therefore concluded that G748 mutations in combination with species-specific nucleotide alterations in the central loop of domain II of 23S rRNA are likely sufficient to reduce susceptibility of M. bovis to tylosin and tilmicosin.

Antimicrobial susceptibility and multilocus sequence typing of Mycoplasma capricolum subsp. capricolum

Mycoplasma capricolum subsp. capricolum is one of the causative agents of contagious agalactia (CA). Nevertheless, there is still a lack of information about its antimicrobial susceptibility and genetic characteristics. Therefore, the aim of this work was to study the antimicrobial and genetic variability of different Mycoplasma capricolum subsp. capricolum field isolates. For this purpose, the growth inhibition effect of 18 antimicrobials and a multilocus sequence typing (MLST) scheme based on five housekeeping genes (fusA, glpQ, gyrB, lepA and rpoB) were performed on 32 selected field isolates from Italy and Spain.The results showed a wide range of growth inhibitory effects for almost all the antimicrobials studied. Macrolides presented lower efficacy inhibiting Mcc growth than in previous works performed on other CA-causative mycoplasmas. Erythromycin was not able to inhibit the growth of any of the studied strains, contrary to doxycycline, which inhibited the growth of all of them from low concentrations. On the other hand, the study of the concatenated genes revealed a high genetic variability among the different Mcc isolates. Hence, these genetic variations were greater than the ones reported in prior works on other mycoplasma species.

Immunoproteomic identification of MbovP579, a promising diagnostic biomarker for serological detection of Mycoplasma bovis infection

A lack of knowledge regarding the antigenic properties of Mycoplasma bovis proteins prevents the effective control of bovine infections using immunological approaches. In this study, we detected and characterized a specific and sensitive M. bovis diagnostic biomarker. After M. bovis total proteins and membrane fractions were separated with two dimensional gel electrophoresis, proteins reacting with antiserawere detected using MALDI-TOF MS. Thirty-nine proteins were identified, 32 of which were previously unreported. Among them, immunoinformatics predicted eight antigens, encoded by Mbov_0106, 0116, 0126, 0212, 0275, 0579, 0739, and 0789, to have high immunological value. These genes were expressed in E. coli after mutagenesis of UGA to UGG using overlap extension PCR. A lipoprotein, MbovP579, encoded by a functionally unknown gene, was a sensitive and specific antigen for detection of antibodies in sera from both M. bovis-infected and vaccinated cattle. The specificity of MbovP579 was confirmed by its lack of cross-reactivity with other mycoplasmas, including Mycoplasma agalactiae. An iELISA based on rMbovP579 detected seroconversion 7 days post-infection (dpi). The ELISA had sensitivity of 90.2% (95% CI: 83.7%, 94.3%) and a specificity of 97.8% (95% CI: 88.7%, 99.6%) with clinical samples. Additional comparative studies showed that both diagnostic and analytic sensitivities of the ELISA were higher than those of a commercially available kit (p<0.01). We have thus detected and characterized the novel antigen, MbovP579, and established an rMbovP579-based ELISA as a highly sensitive and specific method for the early diagnosis of M. bovis infection.

Mycoplasma bovis: Mechanisms of Resistance and Trends in Antimicrobial Susceptibility

Mycoplasma bovis is a cell-wall-less bacterium and belongs to the class Mollicutes. It is the most important etiological agent of bovine mycoplasmoses in North America and Europe, causing respiratory disease, mastitis, otitis media, arthritis, and reproductive disease. Clinical disease associated with M. bovis is often chronic, debilitating, and poorly responsive to antimicrobial therapy, resulting in significant economic loss, the full extent of which is difficult to estimate. Until M. bovis vaccines are universally available, sanitary control measures and antimicrobial treatment are the only approaches that can be used in attempts to control M. bovis infections. However, in vitro studies show that many of the current M. bovis isolates circulating in Europe have high minimum inhibitory concentrations (MIC) for many of the commercially available antimicrobials. In this review we summarize the current MIC trends indicating the development of antimicrobial resistance in M. bovis as well as the known molecular mechanisms by which resistance is acquired.

Antimicrobial susceptibility of Mycoplasma bovis isolates from veal calves and dairy cattle in the Netherlands

Control of Mycoplasma bovis infections depends on good husbandry practices and antibiotic treatment. To allow more prudent use of antimicrobial drugs, there is a need for information on the susceptibility profile of this pathogen. The objective of the present study was to analyse the in vitro antimicrobial susceptibility of clinical M. bovis isolates in the Netherlands. The collection comprised 95 bovine isolates, originating from lungs (n=56), mastitis milk (n=27), and synovial fluid (n=12), collected between 2008 and 2014. Minimal inhibitory concentrations (MICs) were assessed by broth microdilution, both by using in-house prepared MIC plates and by using commercially available MIC plates. For each antimicrobial agent, the range of MIC results, the MIC50, and MIC90 values were calculated. M. bovis strains recently isolated in the Netherlands appeared to be characterized by relatively high MIC values for antimicrobial agents that, until now, have been recommended by the Dutch Association of Veterinarians for treating pneumonia caused by Mycoplasma species. Fluoroquinolones appeared to be the most efficacious in inhibiting M. bovis growth, followed by tulathromycin and oxytetracycline. The highest MIC values were obtained for erythromycin, tilmicosin, and tylosin. Future studies should be done on determining M. bovis specific clinical breakpoints, standardization of methods to determine MIC values as well as molecular studies on detection of antimicrobial resistance mechanisms of M. bovis isolates to develop PCR assays for determining resistance.

In vitro antimicrobial susceptibility of Mycoplasma bovis clinical isolates recovered from bison (Bison bison)

Mycoplasma bovis is a pathogen globally affecting cattle and bison herds, causing pneumonia, arthritis, mastitis, abortions, and other symptoms, leading to huge economic losses. Many studies have been done regarding the antimicrobial susceptibility of M. bovis isolated from cattle, but no such study is available for isolates recovered from bison. For the first time, in vitro susceptibilities of 40 M. bovis clinical isolates collected from bison herds in Canada are reported here. Minimal inhibitory concentration (MIC) values were determined using Sensititre® plates. The most effective MIC50 and MIC90 were for spectinomycin (1 and >64 μg/mL), tiamulin (1 and >32 μg/mL), and tulathromycin (16 and 64 μg/mL), whereas tetracyclines, fluoroquinolones, and florfenicol failed to inhibit growth of M. bovis bison isolates. Isolates were nonsusceptible to tetracyclines (100%), fluoroquinolones (97.5%), and tilmicosin (100%), whereas the highest susceptibility of bison clinical isolates was seen with spectinomycin (95%) and tulathromycin (67.5%). Two lung isolates (Mb283 and 348) were found resistant to both spectinomycin and tulathromycin. These results show a marked difference in antimicrobial susceptibility of bison isolates as compared with previously reported and laboratory reference cattle isolates, emphasizing the necessity of testing antimicrobial susceptibility of M. bovis bison isolates and to generate better therapeutic regime for improved recovery chances for infected bison herds across North America.

Antimicrobial susceptibility and molecular characterization of macrolide resistance of Mycoplasma bovis isolates from multiple provinces in China

Mycoplasma bovis has spread widely throughout the world via animal movement and has become an important pathogen of bovine respiratory disease. However, the minimum inhibitory concentrations of antimicrobials for Mycoplasma bovis have not been studied in China. The objective of this study was to determine the prevalence and antibiotic resistance of Mycoplasma bovis isolated from young cattle with respiratory infection in China. Mycoplasma bovis was detected in 32/45 bovine respiratory infection outbreaks at beef farms in 8 provinces in China. The isolates were susceptible or had medium sensitivity to ciprofloxacin, enrofloxacin and doxycycline, but were frequently resistant to macrolides (13/32, 41%). An A2058G (Escherichia coli Numbering) mutation located in the rrnA operon in domain V of 23S rRNA was observed in strains that were resistant to macrolides. This single mutations at the rrnA operon in domain V of 23S rRNA may play an important role in the resistance of Mycoplasma bovis strains to macrolides.

16S rRNA gene mutations associated with decreased susceptibility to tetracycline in Mycoplasma bovis

Mycoplasma bovis isolates with decreased susceptibilities to tetracyclines are increasingly reported worldwide. The acquired molecular mechanisms associated with this phenomenon were investigated in 70 clinical isolates of M. bovis. Sequence analysis of the two 16S rRNA-encoding genes (rrs3 and rrs4 alleles) containing the primary binding pocket for tetracycline (Tet-1 site) was performed on isolates with tetracycline hydrochloride MICs of 0.125 to 16 μg/ml. Mutations at positions A965T, A967T/C (Escherichia coli numbering) of helix 31, U1199C of helix 34, and G1058A/C were identified. Decreased susceptibilities to tetracycline (MICs, ≥2 μg/ml) were associated with mutations present at two (A965 and A967) or three positions (A965, A967, and G1058) of the two rrs alleles. No tet(M), tet(O), or tet(L) determinants were found in the genome of any of the 70 M. bovis isolates. The data presented correlate (P<0.0001) the mutations identified in the Tet-1 site of clinical isolates of M. bovis with decreased susceptibility to tetracycline.

Antibiotic susceptibility profiles of Mycoplasma bovis strains isolated from cattle in Hungary, Central Europe

Background

Mycoplasma bovis is a worldwide pathogen, causative agent of pneumonia, mastitis, arthritis, and a variety of other symptoms in cattle. The economic losses due to mycoplasma pneumonia could be reduced by antibiotic treatment. The aim of the present study was to determine the in vitro susceptibility of M. bovis strains isolated from cattle in Hungary to eleven antibiotics.

Results

Minimal inhibitory concentration (MIC) values of 35 M. bovis strains collected from different parts of Hungary between 2010 and 2013 were determined by the microbroth dilution method. Strains with high MIC values were found in the case of all applied antibiotics. The most effective antibiotics tested in vitro were fluoroquinolones (MIC₉₀ danofloxacin 0.312 μg/ml, enrofloxacin 0.312 μg/ml, marbofloxacin 0.625 μg/ml). Our results confirm the observations of increasing MIC values to antibiotics commonly used in the therapy of mycoplasma infections, primarily to tetracyclines; tetracycline (MIC₉₀ 16 μg/ml) and oxytetracycline (MIC₉₀ ≥ 64 μg/ml) and macrolides; tylosin (MIC₉₀ ≥ 128 μg/ml) and tilmicosin (MIC₉₀ ≥ 128 μg/ml). The growth of many M. bovis strains was not inhibited by gentamicin (MIC₉₀ 8 μg/ml), spectinomycin (MIC₉₀ ≥ 256 μg/ml), florfenicol (MIC₉₀ 8 μg/ml) or lincomycin (MIC₉₀ ≥ 64 μg/ml).

Conclusions

Our results emphasize the necessity of periodic testing for antibiotic susceptibility in this geographic region. Based on our in vitro examinations, fluoroquinolones could be the most effective drugs for the therapy of M. bovis infections in Hungary. However, current antimicrobial use policies have to be taken into account to avoid further antibiotic resistance development and to reserve fluoroquinolones for the treatment of severe infections which have responded poorly to other classes of antimicrobials.

Macrolides and lincosamides in cattle and pigs: use and development of antimicrobial resistance

Macrolides and lincosamides are important antibacterials for the treatment of many common infections in cattle and pigs. Products for in-feed medication with these compounds in combination with other antimicrobials are commonly used in Europe. Most recently approved injectable macrolides have very long elimination half-lives in both pigs and cattle, which allows once-only dosing regimens. Both in-feed medication and use of long-acting injections result in low concentrations of the active substance for prolonged periods, which causes concerns related to development of antimicrobial resistance. Acquired resistance to macrolides and lincosamides among food animal pathogens, including some zoonotic bacteria, has now emerged. A comparison of studies on the prevalence of resistance is difficult, since for many micro-organisms no agreed standards for susceptibility testing are available. With animal pathogens, the most dramatic increase in resistance has been seen in the genus Brachyspira. Resistance towards macrolides and lincosamides has also been detected in staphylococci isolated from pigs and streptococci from cattle. This article reviews the use of macrolides and lincosamides in cattle and pigs, as well as the development of resistance in target and some zoonotic pathogens. The focus of the review is on European conditions.

Overall decrease in the susceptibility of Mycoplasma bovis to antimicrobials over the past 30 years in France

Mycoplasma (M.) bovis is frequently implicated in respiratory diseases of young cattle worldwide. Today, to combat M. bovis in Europe, only antimicrobial therapy is available, but often fails, leading to important economical losses. The antimicrobial susceptibility of M. bovis is not covered by antimicrobial resistance surveillance networks. The objectives of this study were to identify resistances that were acquired over the last 30 years in France and to determine their prevalence within contemporary strains. The minimum inhibition concentration (MIC) values of 12 antimicrobials, considered active on M. bovis, were compared, using an agar dilution method, between 27 and 46 M. bovis isolates respectively obtained in 1978-1979 and in 2010-2012 from 73 distinct respiratory disease outbreaks in young cattle all over France. For eight antimicrobials, resistances were proven to be acquired over the period and expressed by all contemporary strains. The increase of the MIC value that inhibited 50% of the isolates (MIC50) was: i) substantial for tylosin, tilmicosin, tulathromycin and spectinomycin, from 2 to >64, 2 to >128, 16 to 128 and 4 to >64 µg/mL, respectively, ii) moderate for enrofloxacin, danofloxacin, marbofloxacin and oxytetracycline, from 0.25 to 0.5, 0.25 to 0.5, 0.5 to 1, 32 to >32 µg/mL, respectively. No differences were observed for gamithromycin, tildipirosin, florfenicol and valnemulin with MIC50 of 128, 128, 8, <0.03 µg/mL, respectively. If referring to breakpoint MIC values published for respiratory bovine pathogens, all contemporary isolates would be intermediate in vivo for fluoroquinolones and resistant to macrolides, oxytetracycline, spectinomycin and florfenicol.

Antimicrobial susceptibilities of Mycoplasma isolated from bovine mastitis in Japan

Mycoplasma spp. are highly contagious pathogens and intramammary Mycoplasma infection is a serious issue for the dairy industry. As there is no effective vaccine for Mycoplasma infection, control depends on good husbandry and chemo-antibiotic therapy. In this study, antimicrobial susceptibility of Mycoplasma strains recently isolated from cases of bovine mastitis in Japan was evaluated by minimum inhibitory concentration (MIC). All Mycoplasma bovis strains were sensitive to pirlimycin, danofloxacin and enrofloxacin, but not kanamycin, oxytetracycline, tilmicosin or tylosin. M. californicum and M. bovigenitalium strains were sensitive to pirlimycin, danofloxacin, enrofloxacin, oxytetracycline, tilmicosin and tylosin, but not to kanamycin. This is the first report to describe the MIC of major antimicrobial agents for Mycoplasma species isolated from bovine mastitis in Japan.

In vitro antimicrobial inhibition of Mycoplasma bovis isolates submitted to the Pennsylvania Animal Diagnostic Laboratory using flow cytometry and a broth microdilution method

Mycoplasma bovis is an important pathogen of cattle, causing mastitis, pneumonia, conjunctivitis, otitis, and arthritis. Currently there are only a few reports of sensitivity levels for M. bovis isolates from the United States. Mycoplasma bovis isolates submitted to the Pennsylvania Animal Diagnostic Laboratory between December 2007 and December 2008 (n = 192) were tested for antimicrobial susceptibility to enrofloxacin, erythromycin, florfenicol, spectinomycin, ceftiofur, tetracycline, and oxytetracycline using a broth microdilution method. The most effective antimicrobials against M. bovis determined by using the broth microdilution method were florfenicol, enrofloxacin, and tetracycline with minimum inhibitory concentration (MIC) ranges of 2-32 µg/ml, 0.1-3.2 µg/ml, and 0.05 to >12.8 µg/ml, respectively. Spectinomycin, oxytetracycline, and tetracycline showed a wide-ranging level of efficacy in isolate inhibition with broth microdilution with MIC ranges of 4 to >256 µg/ml, 0.05 to >12.8 µg/ml, and 0.05 to >12.8 µg/ml, respectively. A significant difference in the susceptibility levels between quarter milk and lung isolates was found for spectinomycin. When MIC values of a subset of the M. bovis isolates (n=12) were tested using a flow cytometric technique, the MIC ranges of enrofloxacin, spectinomycin, ceftiofur, erythromycin, tetracycline, oxytetracycline, and florfenicol ranges were 0.1-0.4 µg/ml, 4 to >256 µg/ml, >125 µg/ml, >3.2 µg/ml, <0.025 to >6.4 µg/ml, 0.8 to >12.8 µg/ml, and <2-4 µg/ml, respectively. Flow cytometry offers potential in clinical applications due to high-throughput capability, quick turnaround time, and the objective nature of interpreting results.

Characterization of in vivo-acquired resistance to macrolides of Mycoplasma gallisepticum strains isolated from poultry

The macrolide class of antibiotics, including tylosin and tilmicosin, is widely used in the veterinary field for prophylaxis and treatment of mycoplasmosis. In vitro susceptibility testing of 50 strains of M. gallisepticum isolated in Israel during the period 1997-2010 revealed that acquired resistance to tylosin as well as to tilmicosin was present in 50% of them. Moreover, 72% (13/18) of the strains isolated from clinical samples since 2006 showed acquired resistance to enrofloxacin, tylosin and tilmicosin. Molecular typing of the field isolates, performed by gene-target sequencing (GTS), detected 13 molecular types (I-XIII). Type II was the predominant type prior to 2006 whereas type X, first detected in 2008, is currently prevalent. All ten type X strains were resistant to both fluoroquinolones and macrolides, suggesting selective pressure leading to clonal dissemination of resistance. However, this was not a unique event since resistant strains with other GTS molecular types were also found. Concurrently, the molecular basis for macrolide resistance in M. gallisepticum was identified. Our results revealed a clear-cut correlation between single point mutations A2058G or A2059G in domain V of the gene encoding 23S rRNA (rrnA, MGA_01) and acquired macrolide resistance in M. gallisepticum. Indeed, all isolates with MIC ≥ 0.63 μg/mL to tylosin and with MIC ≥ 1.25 μg/mL to tilmicosin possess one of these mutations, suggesting an essential role in decreased susceptibility of M. gallisepticum to 16-membered macrolides.

Bovine mycoplasmosis: silent and deadly

The first international conference on bovine mycoplasmosis, held in Saskatoon, Canada, in 2009, marked an official recognition of the importance of mycoplasmas in bovine respiratory disease, mastitis, arthritis and other disorders. Furthermore, bovine mycoplasmosis has been identified as a major emerging infectious disease by the European Community 7th Framework Programme under the EMIDA ERA-NET, which is funding a three-year study into the development of improved diagnosis and control of bovine mycoplasmosis involving the UK, Germany, Italy and Israel. These developments coincide with the publication of the complete sequence of the Mycoplasma bovis genome, which offers fresh insight into the properties of this tiny wall-less bacterium. With this in mind, it is an appropriate time to review our knowledge of cattle diseases caused by mycoplasmas.

Associations between the prevalence of Mollicutes and Mycoplasma bovis and health and performance in stocker calves

A longitudinal cross-sectional time-series study was carried out to determine the prevalence of nasal mycoplasma carriage, serostatus and seroconversion, and to evaluate the associations between these parameters and health and performance in weaned beef calves during a 42-day feeding period. Nasal swabs and serum were collected on days 0 (arrival), 10, 42 and at the first incidence of bovine respiratory disease complex. The samples were evaluated for Mollicutes (by culture), Mycoplasma bovis (by PCR) and serum antibody to M. bovis. On day 0, 90.4 per cent of the calves were Mollicutes nasal culture-positive. The seroprevalence of M. bovis was 26.6 per cent on day 0 and 98.2 per cent by day 42 (P<0.05). Seroconversion to M. bovis between days 0 and 42 was significantly associated (P=0.04) with lower weight gain. Weight gain was greater in calves that were PCR-negative for M. bovis on day 10 (P=0.01). The percentage of calves seropositive to M. bovis increased throughout the study, indicating exposure and an immunological response to the organism. Although associations with health outcomes were not identified, seroconversion to M. bovis was associated with a decreased rate of weight gain during the study period.

Development and evaluation of a novel single-nucleotide-polymorphism real-time PCR assay for rapid detection of fluoroquinolone-resistant Mycoplasma bovis

Monitoring of the susceptibility of Mycoplasma bovis field isolates to antibiotics is important for the appropriate choice of treatment. However, in vitro susceptibility testing of mycoplasmas is technically demanding and time-consuming, especially for clinical isolates, and is rarely performed in mycoplasma diagnostic laboratories. Thus, the development of methods allowing rapid real-time detection of resistant strains of M. bovis in clinical samples is a high priority for successful treatment. In this study, a novel TaqMan single-nucleotide-polymorphism (SNP) real-time PCR assay, which enables the rapid identification of M. bovis strains with different susceptibilities to fluoroquinolones, was developed and evaluated. The TaqMan SNP real-time PCR assay is based on the amplification of a 97-bp fragment of the parC quinolone resistance-determining region (QRDR) and allows the specific detection of four possible genotypes: GAC or GAT (susceptible to fluoroquinolones) and AAC or AAT (resistant to fluoroquinolones). Four TaqMan minor groove binder (MGB) probes identifying 1-base mismatches were designed and applied in a dual-probe assay with two reaction tubes. The TaqMan SNP real-time PCRs developed are highly specific for M. bovis, with a detection limit of 5 fg/microl (about 5 M. bovis genomes). In addition, all four SNP real-time PCR tests have almost the same efficiency (97.7% [GAC], 94% [AAC], 99.99% [GAT], and 98% [AAT]). Taken together, the data suggest that this SNP real-time PCR assay has potential as a routine diagnostic test for the detection of decreased susceptibility of M. bovis to fluoroquinolones.

Rapid detection of a point mutation in the parC gene associated with decreased susceptibility to fluoroquinolones in Mycoplasma bovis

Comparison of the quinolone resistance-determining regions (QRDRs) in 42 Mycoplasma bovis clinical isolates revealed amino acid substitutions at both GyrA (position 83) and ParC (position 84) in 10/11 enrofloxacin-resistant strains. The mutation present in the parC QRDR was discriminative for enrofloxacin resistance by parC PCR-restriction fragment length polymorphism. Comparison of molecular profiles by insertion sequence typing suggests that the currently prevalent enrofloxacin-resistant M. bovis strain evolved by selection under field conditions from one of the susceptible strains.