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

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.

Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): contagious bovine pleuropneumonia

Contagious bovine pleuropneumonia has been assessed according to the criteria of the Animal Health Law (AHL), in particular criteria of Article 7 on disease profile and impacts, Article 5 on the eligibility of contagious bovine pleuropneumonia to be listed, Article 9 for the categorisation of contagious bovine pleuropneumonia according to disease prevention and control rules as in Annex IV and Article 8 on the list of animal species related to contagious bovine pleuropneumonia. The assessment has been performed following a methodology composed of information collection and compilation, expert judgement on each criterion at individual and, if no consensus was reached before, also at collective level. The output is composed of the categorical answer, and for the questions where no consensus was reached, the different supporting views are reported. Details on the methodology used for this assessment are explained in a separate opinion. According to the assessment performed, contagious bovine pleuropneumonia can be considered eligible to be listed for Union intervention as laid down in Article 5(3) of the AHL. The disease would comply with the criteria as in Sections 4 and 5 of Annex IV of the AHL, for the application of the disease prevention and control rules referred to in points (d) and (e) of Article 9(1). The animal species to be listed for contagious bovine pleuropneumonia according to Article 8(3) criteria are species of the family Bovidae as susceptible.

Resistance mechanisms against quinolones in Mycoplasma capricolum subsp. capricolum

Quinolones interact with bacterial DNA gyrase and topoisomerase IV, the subunits of which are encoded by gyrA/gyrB and parC/parE, respectively. The aim of this study was to evaluate the relationship between changes in these genes and quinolone susceptibility of Mycoplasma capricolum subsp. capricolum (Mcc). Using in vitro selected resistant mutants and field isolates from goats, predicted amino acid changes in gyrA, gyrB and parC were associated with higher minimum inhibitory concentration values for quinolones. Alterations in parC predicted amino acid sequences were most frequently associated with quinolone resistance in Mcc.

A randomised clinical trial of a metaphylactic treatment with tildipirosin for bovine respiratory disease in veal calves

BACKGROUND

Bovine respiratory disease (BRD) is a major problem in veal calf rearing units. The objective of this randomised clinical trial was to assess the effectiveness of tildipirosin as a metaphylactic treatment in veal calves on the number of BRD treatments, lung consolidation on thoracic ultrasonography (TUS) and average daily gain (ADG). A total of 209 veal calves from a pre-weaning fattening unit were randomly allocated to receive one of two treatments (tildipirosin 4 mg/kg, subcutaneously, n = 109; placebo 0.9% saline, subcutaneously, n = 100) at day 12 after entry in the pre-weaned unit. The calves were followed for a 70-day period. Occurrence of mortality and BRD treatments were recorded during the pre-weaning period. At days 1, 12 and 30, TUS and clinical scores were performed and ADG was measured during the first and second months of feeding.

RESULTS

The use of a metaphylactic treatment of tildipirosin 12 days after arrival of the veal calves was not associated with the number of BRD treatments performed by the producer, ultrasonographic lung consolidation or weight gain (P < 0,05). In this cohort of calves, the proportion of calves treated for BRD by the producer was low at 14% (29/209). However, 13% (26/209) of calves included in the study already had ultrasonographic lung consolidation lesions 12 days after their arrival, which was before treatment time, and 27% (56/209) had lung consolidation at day 30.

CONCLUSION

In this study population with a low BRD prevalence, we were not able to detect any benefit of tildipirosin as a metaphylactic treatment of BRD at day 12 after arrival based on BRD treatments, TUS, and ADG.

Mutations in the quinolone resistance determining region conferring resistance to fluoroquinolones in Mycoplasma agalactiae

M. agalactiae is the main causative agent of contagious agalactia, against which antimicrobial treatment is the main applied control measure. Quinolones are an effective group of antimicrobials inhibiting the growth of M. agalactiae, but in the last years, various reports have demonstrated an increase of resistance in field isolates due to its massive use. Nevertheless, the molecular mechanisms involved in the acquisition of fluoroquinolones resistance in M. agalactiae have not been elucidated yet. Therefore, the aim of this work was to analyze the presence of DNA variations that could be related to changes in fluoroquinolone susceptibility. For this purpose, three M. agalactiae strains were selected to obtain in vitro resistant mutants against enrofloxacin, marbofloxacin and moxifloxacin and afterwards, partial sequences of their gyrA, gyrB, parC and parE genes were analyzed. In addition, a set of field isolates with different MIC values were also studied. Changes related to variations in fluoroquinolones susceptibility were found in gyrB, parC and parE. Specifically, gyrB genes were affected at the predicted amino acid position 424, four amino acid changes were detected in parC (positions 78, 79, 80 and 84) and two substitutions were reported in parE (amino acid positions 429 and 459). Mutations at predicted positions 424 of gyrB and 429 of parE are novel DNA changes which had not been previously described and, on the whole, parC was the first gene showing alterations when changes in susceptibility to fluoroquinolones occurred. Thus, this gene is the most suitable target for a rapid study of fluoroquinolone resistance in field isolates of M. agalactiae.

Mutations Associated with Decreased Susceptibility to Seven Antimicrobial Families in Field and Laboratory-Derived Mycoplasma bovis Strains

The molecular mechanisms of resistance to fluoroquinolones, tetracyclines, an aminocyclitol, macrolides, a lincosamide, a phenicol, and pleuromutilins were investigated in Mycoplasma bovis For the identification of mutations responsible for the high MICs of certain antibiotics, whole-genome sequencing of 35 M. bovis field isolates and 36 laboratory-derived antibiotic-resistant mutants was performed. In vitro resistant mutants were selected by serial passages of M. bovis in broth medium containing subinhibitory concentrations of the antibiotics. Mutations associated with high fluoroquinolones MICs were found at positions 244 to 260 and at positions 232 to 250 (according to Escherichia coli numbering) of the quinolone resistance-determining regions of the gyrA and parC genes, respectively. Alterations related to elevated tetracycline MICs were described at positions 962 to 967, 1058, 1195, 1196, and 1199 of genes encoding the 16S rRNA and forming the primary tetracycline binding site. Single transversion at position 1192 of the rrs1 gene resulted in a spectinomycin MIC of 256 μg/ml. Mutations responsible for high macrolide, lincomycin, florfenicol, and pleuromutilin antibiotic MICs were identified in genes encoding 23S rRNA. Understanding antibiotic resistance mechanisms is an important tool for future developments of genetic-based diagnostic assays for the rapid detection of resistant M. bovis strains.

EFFICACY AND SAFETY OF BAN HUANG ORAL LIQUID FOR TREATING BOVINE RESPIRATORY DISEASES

BACKGROUND

Ban Huang oral liquid was developed as a veterinary compound preparation by the Lanzhou Institute of Husbandry and Pharmaceutical Sciences of the Chinese Academy of Agricultural Sciences (CAAS). The purpose of this study was to determine whether the oral liquid preparation of traditional Chinese medicine, Ban Huang, is safe and effective for treating respiratory diseases in cattle.

MATERIALS AND METHODS

Acute oral toxicity experiments were conducted in Wistar rats and Kunming mice via oral administration. The minimum inhibitory concentration of the drug against Mycoplasma bovis in vitro with the double dilution method was 500 mg/mL, indicating good sensitivity. The results of laboratory pathogen testing, analysis of clinical symptoms, and analysis of pathological anatomy were combined to diagnose bovine respiratory diseases in 147 Simmental cattle caused by mixed infections of M. bovis, bovine respiratory syncytial virus, bovine parainfluenza virus type 3, and Mannheimia haemolytica. These cattle were randomly divided into three groups: drug treatment group 1 (treated via Tilmicosin injection), drug treatment group 2 (treated with Shuang Huang Lian oral liquid combined with Tilmicosin injection), and drug treatment group 3 (treated with Ban Huang oral liquid combined with Tilmicosin injection). Treatment effects were observed within 7 days.

RESULTS

The results showed no toxicity and a maximum tolerated dose greater than 20 g/kg BW. For the 87 cattle in drug-treatment group, the cure rate was 90.80%, whereas the response rate was 94.25%. The cure rate of drug treatment group was increased by 14.13% in comparison with that of drug control group 1 and by 7.47% in comparison with that of drug control group 2 (both P < 0.05).

CONCLUSION

This study demonstrates that Ban Huang oral liquid is a safe and effective treatment for bovine respiratory diseases, especially for mixed infection caused by M. bovis, bacteria, and viruses.

Mycoplasma mastitis in cattle: To cull or not to cull

Bovine mastitis caused by mycoplasmas, in particular Mycoplasma bovis, is a major problem for milk production and animal welfare in large dairy herds in the USA and a serious, although sporadic, disease in Europe and the Middle East. It causes severe damage to the udder of cattle and is largely untreatable by chemotherapy. Mycoplasma mastitis has a distinct epidemiology and a unique set of risk factors, the most important of which is large herd size. The disease is often self-limiting, disappearing within months of outbreaks, sometimes without deliberate intervention. Improved molecular diagnostic tests are leading to more rapid detection of mycoplasmas. Typing tests, such as multi-locus sequence typing, can help trace the source of outbreaks. An approach to successful control is proposed, which involves regular monitoring and rapid segregation or culling of infected cows. Serious consideration should be given by owners of healthy dairy herds to the purchase of M. bovis-free replacements. Increased cases of disease could occur in Europe and Israel if the trend for larger dairy herds continues.

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.

Comparative efficacy of tulathromycin and tildipirosin for the treatment of experimental Mycoplasma bovis infection in calves

The objective of this negative controlled, blinded, randomised, parallel group study was to compare the efficacy of two injectable macrolide antimicrobials, tulathromycin and tildipirosin, administered by single subcutaneous injection at dose rates of 2.5 and 4.0 mg kg⁻¹ bodyweight, respectively, in the treatment of an experimentally induced Mycoplasma bovis infection in calves. A total of 238 M. bovis‐negative calves were challenged on three consecutive days with M. bovis by endobronchial deposition. Post‐challenge, a total of 126 animals fulfilled the inclusion criteria and were randomly allocated to three treatment groups: tulathromycin, tildipirosin and saline. Clinical observations for signs of respiratory disease and injection site assessments were conducted daily for 14 days post‐treatment. The animals were then killed, the lungs were examined for evidence of lesions, and samples collected for bacterial isolation. Calves treated with tulathromycin had a lower percentage of lung with lesions (P = 0.0079), lower mortality (P = 0.0477), fewer days with depressed demeanour (P = 0.0486) and higher body weight (P = 0.0112) than calves administered tildipirosin.

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.

Mycoplasmas and Their Antibiotic Resistance: The Problems and Prospects in Controlling Infections

The present review discusses the problem of controlling mycoplasmas (class Mollicutes), the smallest of self-replicating prokaryotes, parasites of higher eukaryotes, and main contaminants of cell cultures and vaccines. Possible mechanisms for the rapid development of resistance to antimicrobial drugs in mycoplasmas have been analyzed. Omics technologies provide new opportunities for investigating the molecular basis of bacterial adaptation to stress factors and identifying resistomes, the total of all genes and their products contributing to antibiotic resistance in microbes. The data obtained using an integrated approach with post-genomics methods show that antibiotic resistance may be caused by more complex processes than has been believed heretofore. The development of antibiotic resistance in mycoplasmas is associated with essential changes in the genome, proteome, and secretome profiles, which involve many genes and proteins related to fundamental cellular processes and virulence.

Diversity and variation in antimicrobial susceptibility patterns over time in Mycoplasma agalactiae isolates collected from sheep and goats in France

AIMS

Mycoplasma agalactiae is responsible for Contagious Agalactia, a severe syndrome affecting small ruminants worldwide and resulting in significant economic losses in countries with an important dairy industry. The aim of this study was to examine the antimicrobial susceptibility patterns of M. agalactiae isolates in France, their evolution over the last 25 years and their relationships with the genetic diversity of isolates and their origin (geographical and animal host).

METHODS AND RESULTS

Susceptibility patterns were determined by measuring minimal inhibitory concentrations (MICs) of several antimicrobials used against mycoplasmas. Caprine M. agalactiae strains showed increased MICs over time for most of the antimicrobials tested, except fluoroquinolones. This susceptibility loss was homogeneous despite the considerable genetic and geographical heterogeneity of the isolates. In contrast, all the ovine isolates originating from a single clone and the same region showed increased MICs only to some macrolides.

CONCLUSIONS

MICs have evolved differently depending on the origin of the isolates but the overall loss in susceptibility has remained far more moderate than that of Mycoplasma bovis, a cattle pathogen closely related to M. agalactiae.

SIGNIFICANCE AND IMPACT OF THE STUDY

Several hypotheses are proposed to explain the differences in susceptibility patterns, such as local, specific, nonmycoplasma-targeting antibiotic treatments and the genetic background of isolates in connection with their animal host.

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.

A new predilection site of Mycoplasma bovis: Postsurgical seromas in beef cattle

Mycoplasma bovis is a highly contagious bacterium, which predominantly causes chronic pneumonia, otitis and arthritis in calves and mastitis in adult cattle. In humans, Mycoplasma species have been associated with post-surgical infections. The present study aimed to identify the bacteria associated with three outbreaks of infected seromas after caesarian section in Belgian Blue beef cattle. A total of 10 cases occurred in three herds which were in close proximity of each other and shared the same veterinary practice. M. bovis could be cultured from seroma fluid in five of the six referred animals, mostly in pure culture and was isolated from multiple chronic sites of infection (arthritis and mastitis) as well. DNA fingerprinting of the isolates targeting two insertion sequence elements suggested spread of M. bovis from chronic sites of infection (udder and joints) to the postsurgical seromas. Identical genetic profiles were demonstrated in two animals from two separate farms, suggesting spread between farms. Mortality rate in the referred animals positive for M. bovis in a seroma was 80% (4/5), despite intensive treatment. A massive increase in antimicrobial use was observed in every affected farm. These observations demonstrate involvement of mycoplasmas in outbreaks of postsurgical seromas in cattle.

Alterations in the Quinolone Resistance-Determining Regions and Fluoroquinolone Resistance in Clinical Isolates and Laboratory-Derived Mutants of Mycoplasma bovis: Not All Genotypes May Be Equal

Mycoplasma bovis is considered a major contributor to respiratory diseases in young cattle. Resistant M. bovis isolates have increasingly been reported worldwide due to extensive use of antimicrobials to treat bovine pneumonia. The frequency of isolates resistant to fluoroquinolones varies considerably from one country to another. The MICs of isolates collected in France have only increased from "very low" to "low." The present study was conducted to investigate whether alterations in the quinolone resistance-determining regions (QRDRs) could account for this slight modification in susceptibility. No correlation between QRDR alterations and increased MICs was evidenced in clinical isolates. In addition, all clinical isolates were subtyped, and the tendencies of the different sequence types to develop resistance through mutations in QRDRs under selective pressure in vitro were examined. In vitro, 3 hot spots for mutations in QRDRs (position 83 in GyrA and positions 80 and 84 in ParC) were associated with a high level of resistance when cumulated. We showed that the point mutations in the QRDRs observed in vitro were different (in location and selection rapidity) between the different subtypes. Our in vitro observations were corroborated by the recent detection of a clinical isolate highly resistant to fluoroquinolones (MIC ≥ 16 μg/ml) and belonging to the subtype which easily accumulates QRDR alterations in vitro. The current increased prevalence of this subtype in clinical isolates highlights the urgent need to control fluoroquinolone usage in veterinary medicine.

Severe Mycoplasma bovis outbreak in an Austrian dairy herd

A conventional dairy farm, housing 19 Austrian Simmental cows, experienced a spontaneous outbreak of a Mycoplasma bovis infection, showing severe clinical signs of respiratory tract disease, clinical mastitis, and tremendous drop in milk production. Despite intensive therapy, 5 cows died within 2 weeks or were euthanized. From the remaining cows, bacteriological culture and polymerase chain reaction revealed M. bovis in 10 of 14 milk samples. Mycoplasma bovis was found in 1 of 5 randomly collected nasal swabs. Autopsy of 1 cow revealed infection of the lungs and the udder with M. bovis. The 13 M. bovis isolates from milk samples, nasal swabs, lungs, and udder were genotyped by multilocus variable number of tandem-repeat analysis, and indicated that described infections were caused by a single M. bovis strain. The virulent M. bovis strain resulted in dramatic economic loss to the farmer. To control the disease, culling of all animals, including heifers and calves, was recommended, and strict hygienic measures were implemented before introducing new animals to the farm.

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.

Loss of diversity within Mycoplasma bovis isolates collected in France from bovines with respiratory diseases over the last 35 years

Mycoplasma (M.) bovis has recently emerged as a major, worldwide etiological agent of bovine respiratory diseases leading to huge economic losses mainly due to high morbidity and mortality as well as poor growth rates. The spread of M. bovis infections between different animals, herds, regions or countries has been often reported to be connected to the movement of animals. However, despite recent considerable efforts, no universal subtyping method is yet available to trace M. bovis isolates circulation at an international scale. Moreover in France, the overall population diversity of M. bovis isolates has not been assessed since the early 1990s. This study was conducted to fill in these gaps. The genotypic diversity between sixty isolates collected in France over the last 35 years was assessed using two molecular subtyping methods that addressed either the long-term epidemiological relationships (Multi Locus Sequence Typing, MLST) or the genetic microvariations (Multiple Locus VNTR Analysis, MLVA) between isolates. Phenotypic diversity was also analyzed by using Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry (MALDI-TOF MS) to compare the main protein patterns of isolates. All proposed subtyping approaches were optimized and led to the same pattern in the French M. bovis population that consisted of two clusters, the first one comprising isolates collected before 2000 and the second, those collected after 2000. Recent strains were further shown to be more homogeneous than older ones, which is consistent with the spread of a single clone throughout the country. Because this spread was concomitant with the emergence of multiresistant M. bovis isolates, several hypotheses are discussed to explain the homogeneity of M. bovis isolates in France, even though the M. bovis species is fully equipped to generate diversity.

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.