Suspected aerosol transmission of swine pathogens: A field case.

A swine production system had 3 sections located a few kilometers apart. Sections A and C contained several thousand sows and nursery and finishing pigs. Section B, located between the other 2 sections, was the smallest and had 6 finishing sites and 2 sow sites. The entire system was infected with porcine reproductive and respiratory syndrome virus, Mycoplasma hyopneumoniae, and Actinobacillus pleuropneumoniae. Section B was depopulated, cleaned, disinfected, and repopulated with negative gilts. Despite extreme measures, recontamination occurred for each pathogen, with aerosol considered the most plausible contamination source.

Transmission suspectée d'agents pathogènes porcins par aérosol : un cas de terrainUn système de production porcine comportait 3 sections situées à quelques kilomètres l'une de l'autre. Les sections A et C contenaient plusieurs milliers de truies et de porcs en maternité et en finition. La section B, située entre les 2 autres sections, était la plus petite et comptait 6 sites de finition et 2 sites de truies. L'ensemble du système était infecté par le virus du syndrome reproducteur et respiratoire porcin, Mycoplasma hyopneumoniae et Actinobacillus pleuropneumoniae. La section B a été dépeuplée, nettoyée, désinfectée et repeuplée de cochettes négatives. Malgré des mesures extrêmes, une recontamination s'est produite pour chaque agent pathogène, les aérosols étant considérés comme la source de contamination la plus plausible.(Traduit par Dr Serge Messier).

Genotype diversity of Mycoplasma Hyopneumoniae in Chinese swine herds based on multilocus sequence typing.

BACKGROUND: Between 2018 and 2020, 989 clinical specimens from pigs showing clinical signs of a variety of swine diseases in 27 provinces in China were sampled and submitted for further testing. Nested PCR targeting the 16S rRNA gene of Mycoplasma hyopneumoniae and subsequent sequencing were used to analyse these specimens. Mycoplasma hyopneumoniae-positive samples were assayed by multilocus sequence typing (MLST). The aim of the study was to reveal the distribution of M. hyopneumoniae and determine the genotypes of M. hyopneumoniae in pig herds in China based on MLST. RESULTS: Among these 989 samples, 199 samples were M. hyopneumoniae-positive. The M. hyopneumoniae positivity rate was 7.2% (35/494) in 2018, 18.4% (38/207) in 2019, and 43.8% (126/288) in 2020. In total, 47 samples were successfully assayed by MLST. Sixteen new M. hyopneumoniae sequence types from 9 provinces were recorded in the present study. CONCLUSIONS: This is the first report on sample positivity rates and molecular typing results for M. hyopneumoniae in swine herds in China. MLST has revealed high genotype diversity among M. hyopneumoniae from different provinces of China.

Antibody responses to porcine reproductive and respiratory syndrome virus, influenza A virus, and Mycoplasma hyopneumoniae from weaning to the end of the finisher stage in fourteen groups of pigs in Ontario, Canada.

BACKGROUND: Respiratory diseases are among the most important factors affecting swine farm productivity in Canada. The objectives of this study were to investigate antibody responses to porcine reproductive and respiratory syndrome virus (PRRSV), influenza A virus (IAV), and Mycoplasma hyopneumoniae (M. hyopneumoniae) from weaning to the end of the finisher stage on a subset of commercial swine farms in Ontario, Canada, and to examine the association between nursery diet and antibody responses. RESULTS: Overall, older pigs were more likely to test seropositive for PRRSV and less likely to test seropositive for M. hyopneumoniae (p <  0.001). Pigs were more likely to test seropositive for IAV at weaning and the end of the grower and finisher stages compared to the end of nursery (p <  0.001). Pigs that were seropositive for IAV were more likely to test seropositive for both PRRSV and M. hyopneumoniae (p <  0.001). Two, 9, and 4 groups that had more than 20% of pigs seropositive to PRRSV, IAV, and M. hyopneumoniae, respectively, from the end of nursery to the end of finisher were classified as seropositive. Pigs fed a plant-based (low complexity) diet during nursery were more likely to be seropositive for PRRSV (p <  0.001) but there were no significant differences in seropositivity to IAV or M. hyopneumoniae due to nursery diet complexity. CONCLUSIONS: This study provides information regarding changes in serum antibody in pigs across different stages of production and highlights periods of vulnerability. Additionally, these findings may encourage further research into the effects of nursery diet complexity on disease susceptibility and immune response.

The first assessment to detect Mycoplasma hyopneumoniae by sampling laryngeal swabs to investigate sow stability in South Korea.

BACKGROUND: Mycoplasma hyopneumoniae (M. hyopneumoniae), a representative pathogen causing swine enzootic pneumonia, generally infects piglets vertically. However, it is difficult to ascertain the M. hyopneumoniae infection state of sows due to limited detection methods. This report investigated sow herd stability by applying nested PCR to laryngeal swabs of suckling pigs, which is reportedly the most sensitive method. RESULTS: M. hyopneumoniae was detected in 14 farms (63.6%) and 127 piglets (6.5%). The prevalence of sows likely to transmit M. hyopneumoniae in herds (11.1%) was calculated. In addition, there was a significant difference in detection rates among farms depending on herd size, gilt replacement rate, acclimation method, and antibiotic usage, suggesting various parameters that influence sow stability. CONCLUSIONS: The results demonstrated that laryngeal swabs from suckling pigs have provided useful information regarding vertical transmission from sows in South Korean farm conditions. This result demonstrated that farms with larger herd sizes, higher gilt replacement rates, and a practice of naturally exposing gilts for acclimation had higher detection rates in weaning piglets, indicating an unstable sow infection state.

Serum metabolite markers of early Mycoplasma hyopneumoniae infection in pigs.

Mycoplasma hyopneumoniae, the primary pathogenic bacterium causing enzootic pneumonia, significantly affects worldwide swine production. The infection is usually persistent and bacterial identification and isolation of M. hyopneumoniae in clinical samples are challenging due to the fastidious requirements for its growth. Hence, new practical surveillance tools that improve or complement existing diagnostics on M. hyopneumoniae are desirable, especially in early infection. The objective of this study was to identify potential metabolite markers of early M. hyopneumoniae infection in pigs through metabolomics analysis. Samples obtained from pigs in a previous M. hyopneumoniae experimental infection were used in this study. Briefly, two pigs served as mock inoculated controls and ten pigs were intra-tracheally inoculated with M. hyopneumoniae. Sera, laryngeal swabs (LS), and tracheo-bronchial lavage fluid (TBLF) were collected from all pigs at 0, 2, 5, 9, 14, 21 and 28 days post-inoculation (dpi). Bronchial swabs (BS) were collected post-mortem at 28 dpi. Mycoplasma hyopneumoniae infection was confirmed by PCR in LS, TBLF and BS. Serum metabolites were profiled using high-resolution liquid chromatography-mass spectrometry (LC-MS) analysis. Metabolite markers were identified by structural analysis following multivariate analysis of LC-MS data. The results showed that M. hyopneumoniae infection time-dependently altered the serum levels of selective amino acids and fatty acids. α-Aminobutyric acid and long-chain fatty acids were markedly increased at 14 and 21 dpi in inoculated pigs (p < 0.05). These results indicated that M. hyopneumoniae infection caused systemic changes in host metabolism, warranting further studies to determine underlying biochemical and physiological mechanisms responsible for the observed changes.

Genetic diversity of Mycoplasma hyopneumoniae in Mendoza province.

In Argentina, enzootic pneumonia (EP) is highly prevalent and different genetic types of Mycoplasma hyopneumoniae have been identified. However, there is a lack of information about prevalence and other epidemiological aspects of EP in Mendoza province. A multiple Locus variable-number tandem repeat analysis (MLVA) targeting P97 R1, P97 R1A and P146 R3 loci was used to assess the genetic diversity of M. hyopneumoniae from clinical specimens recovered from pigs from five herds located in different districts of Mendoza province. M. hyopneumoniae could be typed from 27 bronchoalveolar lavages (BAL) specimens, and eight different MLVA types were identified. This is the first report about diversity of M. hyopneumoniae in Mendoza. Results obtained in this work allow drawing a better picture of the genetic diversity of this pathogen in Argentina.

Persistence of the same genetic type of Mycoplasma hyopneumoniae in a closed herd for at least two years.

Two cross-sectional studies were carried out in 2013 and 2015 monitoring for Mycoplasma hyopneumoniae presence in a swine farm. In these studies, the genetic diversity of M. hyopneumoniae was assessed in clinical specimens using a Multiple Locus Variable-number tandem repeat Analysis (MLVA) targeting P97 R1, P146 R3 and H4 loci. The samples from August 2015 showed the MLVA profile prevalent in June 2013, therefore it can be concluded that a same genetic type of M. hyopneumoniae can persist for at least two years in a closed herd. In addition, the nested PCR reactions implemented in this study showed to be useful for MLVA typing in non-invasive clinical samples.

Efficacy of one dose vaccination against experimental infection with two Mycoplasma hyopneumoniae strains.

BACKGROUND: Mycoplasma hyopneumoniae (M. hyopneumoniae) is the primary agent of enzootic pneumonia in pigs. Pigs are often infected with different M. hyopneumoniae strains. This study assessed the efficacy of vaccination against experimental infection with two genetically different M. hyopneumoniae strains in weaned piglets. At 33 days of age (D0), 45 M. hyopneumoniae-free piglets were randomly assigned to three different groups: 1) negative control group (NCG; n = 5): not vaccinated, not infected, 2) positive control group (PCG; n = 20): not vaccinated, infected, and 3) vaccination group (VG; n = 20): single vaccination with an inactivated whole-cell M. hyopneumoniae vaccine (Hyogen®, Ceva) (D1), infected. The PCG and VG were endotracheally inoculated with 7 × 107 CCU in 7 ml of the highly virulent M. hyopneumoniae strain F7.2C (D24) and 7 × 107 CCU in 7 ml low virulent strain F1.12A (D25). A respiratory disease score (RDS) was assessed from D24 until D53. At D53 (euthanasia), macroscopic lung lesions (MLL) were scored, log copies of M. hyopneumoniae DNA (qPCR) and IL-1 and IL-6-concentrations (ELISA) on bronchoalveolar lavage fluid were determined. RESULTS: The RDS and MLL at euthanasia were respectively 0, 1.20 and 0.55 (P < 0.001) and 0, 7.56 and 0.68 (P < 0.001) for NCG, PCG and VG, respectively. The qPCR results for PCG and VG were 3.99 and 1.78 log copies (P < 0.001), respectively, with a significant difference between PCG and VG. The IL-1 and IL-6 results at euthanasia for NCG, PCG and VG were 17.61, 1283.39 and 53.04 pg/ml (P < 0.001) and 148.10, 493.35 and 259.80 pg/ml (P = 0.004), respectively with a significant difference between PCG and VG. CONCLUSIONS: Vaccination with Hyogen® in pigs was efficacious against an experimental challenge with both a low and highly virulent M. hyopneumoniae strain as the vaccinated pigs coughed significantly less, and showed significantly less lung lesions compared to the non-vaccinated challenged pigs: the vaccinated animals showed a 52.9% lower RDS and 91.0% lower MLL compared to the PCG. In the bronchoalveolar lavage fluid collected at the necropsy of the vaccinated pigs, a significantly lower amount of M. hyopneumoniae-DNA and a significantly lower IL-1 and IL-6 concentration was found compared to the pigs of the PCG.

Detection and phylogenetic analysis of Mycoplasma hyopneumoniae from Tibetan pigs in western China.

Enzootic pneumonia (EP), often caused by Mycoplasma hyopneumoniae, occurs in Tibetan pigs between October and December in Western China. The aim of this study was to determine the prevalence of M. hyopneumoniae in Tibetan pig herds and also the prevalence of infection. M. hyopneumoniae was detected using enzyme-linked immunosorbent assay, polymerase chain reaction (PCR), and 16S rRNA sequencing. Twenty-nine inflammatory gross-lesions were observed in 155 lungs of slaughtered pigs. Invasion of focal lymphocytes was confirmed by paraffin sectioning and hematoxylin-eosin staining of lung sections. Bronchoalveolar lavage fluid (BALF) from slaughtered Tibetan pigs and nasal swabs from others were assayed using PCR. The prevalence of M. hyopneumoniae in Tibetan pig herds (via ELISA) was 20.48% (93/454) in 3 provinces (Sichuan, Tibet autonomous region, and Qinghai) between October and December of 2014. The difference in prevalence among animals in six different growing stages was statistically significant (P < 0.05). Anti-M. hyopneumoniae antibody was detected in breeding sows (45.83%; 22/48) and piglets (50%; 3/6). PCR and gel electrophoresis of BALF showed that 6.45% (10/155) of pigs were positive for M. hyopneumoniae. The presence of M. hyopneumoniae in serum was higher in piglets and breeding sows than in any other group. In conclusion, the results of this study showed that M. hyopneumoniae is prevalent among Tibetan pigs between October and December in Western China. To the authors' knowledge, this is the first investigation of M. hyopneumoniae prevalence in Tibetan pigs of Western China using serological tests, PCR, and 16S rRNA sequencing.

A comparative pathological finding in pigs exposed to fumonisin B1 and/or Mycoplasma hyopneumoniae.

A more complicated pathology was observed in female pigs infected with Mycoplasma hyopneumoniae, when the same were exposed to 20 ppm dietary levels of fumonisin B1 (FB1) starting 14 days before infection for a period of 42 days as was assessed by gross pathology and pathomorphological examinations or computed tomography, and also manifested by the strong deterioration of the pneumonic process in two pigs and the subsequent euthanizing of one pig. Typical damages in FB1-fed pigs were a strong oedema in the lung and slight oedema in the other internal organs and mild degenerative changes in the kidneys, whereas the typical pathomorphological changes in M. hyopneumoniae-infected pigs corresponded to the morphologic pattern of a catarrhal bronchointerstitial pneumonia more pronounced in the cranial and middle lobes or in the cranial third of the caudal lobe of the lung. The pigs treated by both pathogens (toxic and infectious) revealed strong oedematous changes in the interstitium of lung in addition to deteriorated and extended bronchointerstitial pneumonic process.

A rapid and sensitive loop-mediated isothermal amplification procedure (LAMP) for Mycoplasma hyopneumoniae detection based on the p36 gene.

The aim of this study was to establish a method for sensitive and rapid diagnosis of Mycoplasma hyopneumoniae in clinical specimens. To this effect, we employed three sets of primers specifically designed for amplification of nucleic acids under isothermal conditions. After optimization of reaction conditions, M. hyopneumoniae could be successfully detected at 63°C in 45 min through use of the loop-mediated isothermal amplification (LAMP) assay. A positive reaction was identified visually as white precipitate and confirmed by gel electrophoresis. The detection limit for this assay was 10 copies/µL, as observed by electrophoretic analysis. The accuracy of the LAMP reaction was confirmed by restriction endonuclease digestion as well as by direct sequencing of the amplified product. This method can specifically detect M. hyopneumoniae; other species with high homology and other bacterial and virus strains gave negative results. To test the utility of this procedure, the LAMP assay was applied to 40 clinical samples collected from swine lung tissues experimentally challenged with M. hyopneumoniae isolates, and compared to the results from a real-time polymerase chain reaction (PCR) assay. A concordance of 100% was observed between the two assays. In conclusion, the results from our study demonstrated that the LAMP assay provided a rapid reaction and was inexpensive to perform, with no need of complex instruments or systems such as Geneamp PCR. The LAMP assay may therefore be applied in routine diagnosis in the clinical laboratory and for in-field detection of M. hyopneumoniae infection.

Effect of pooled tracheal sample testing on the probability of Mycoplasma hyopneumoniae detection.

Tracheal pooling for Mycoplasma hyopneumoniae (M. hyopneumoniae) DNA detection allows for decreased diagnostic cost, one of the main constraints in surveillance programs. The objectives of this study were to estimate the sensitivity of pooled-sample testing for the detection of M. hyopneumoniae in tracheal samples and to develop probability of M. hyopneumoniae detection estimates for tracheal samples pooled by 3, 5, and 10. A total of 48 M. hyopneumoniae PCR-positive field samples were pooled 3-, 5-, and 10-times using field M. hyopneumoniae DNA-negative samples and tested in triplicate. The sensitivity was estimated at 0.96 (95% credible interval [Cred. Int.]: 0.93, 0.98) for pools of 3, 0.95 (95% Cred. Int: 0.92, 0.98) for pools of 5, and 0.93 (95% Cred. Int.: 0.89, 0.96) for pools of 10. All pool sizes resulted in PCR-positive if the individual tracheal sample Ct value was < 33. Additionally, there was no significant decrease in the probability of detecting at least one M. hyopneumoniae-infected pig given any pool size (3, 5, or 10) of tracheal swabs. Furthermore, this manuscript applies the probability of detection estimates to various real-life diagnostic testing scenarios. Combining increased total animals sampled with pooling can be a cost-effective tool to maximize the performance of M. hyopneumoniae surveillance programs.

Use of computed tomography and histopathologic review for lung lesions produced by the interaction between Mycoplasma hyopneumoniae and fumonisin mycotoxins in pigs.

Mycoplasma hyopneumoniae has a primary role in the porcine respiratory disease complex (PRDC). The objective of this study was to determine whether fumonisin mycotoxins influence the character and/or the severity of pathological processes induced in the lungs of pigs by Mycoplasma hyopneumoniae. Four groups of pigs (n = 7/group) were used, one fed 20 ppm fumonisin B1 (FB1) from 16 days of age (group F), one only infected with M. hyopneumoniae on study day 30 (group M), and a group fed FB1 and infected with M. hyopneumoniae (group MF), along with an untreated control group (group C). Computed tomography (CT) scans of infected pigs (M and MF) on study day 44 demonstrated lesions extending to the cranial and middle or in the cranial third of the caudal lobe of the lungs. The CT images obtained on study day 58 showed similar but milder lesions in 5 animals from group M, whereas lungs from 2 pigs in group MF appeared progressively worse. The evolution of average pulmonary density calculated from combined pixel frequency values, as measured by quantitative CT, was significantly influenced by the treatment and the age of the animals. The most characteristic histopathologic lesion in FB1-treated pigs was pulmonary edema, whereas the pathomorphological changes in Mycoplasma-infected pigs were consistent with catarrhal bronchointerstitial pneumonia. FB1 aggravated the progression of infection, as demonstrated by severe illness requiring euthanasia observed in 1 pig and evidence of progressive pathology in 2 pigs (group MF) between study days 44 and 58.

Loop-mediated isothermal amplification for rapid and convenient detection of Mycoplasma hyopneumoniae.

Loop-mediated isothermal amplification (LAMP), a novel method of gene amplification, was employed in this study for detecting Mycoplasma hyopneumoniae in the respiratory tract or lungs of swine. The pathogen can be detected in LAMP reactions containing as few as 10 fg purified target DNA (10 copies of M. hyopneumoniae genome) within 30 min, which was comparable to real-time PCR. After 30-min reaction at 63 °C, the addition of a certain amount of dye (SYBR Green I and hydroxyl naphthol blue at a proper ratio) into the LAMP reaction system makes the results easily determined as positive or negative by visual inspection. In addition, the LAMP was able to distinguish between M. hyopneumoniae and other closely-related mycoplasma strains, indicating a high degree of specificity. The LAMP assay was more simple and cheap, since the reaction could be completed under isothermal conditions and less laboratorial infrastructure are required. And, it was proven reliable for M. hyopneumoniae diagnosis of nasal swab and lung samples from the field.

Duration of Mycoplasma hyopneumoniae detection in pigs following purposeful aerosol exposure.

Swine disease elimination programs for Mycoplasma hyopneumoniae are commonly applied in the North American swine industry and may include the aerosolization of medium containing lung tissue to achieve population exposure prior to start. Field data has indicated M. hyopneumoniae PCR detection in pigs beyond 240 days post-herd closure (dphc; planned end of an elimination program) and is thought to contribute to disease elimination programs' failure. Here, the duration of M. hyopneumoniae detection in sows and replacement gilts following aerosolized lung homogenate exposure, as part of a dual disease elimination program, was determined. A subset of sows and gilts from a commercial sow herd and off-site gilt development unit were longitudinally sampled to collect deep tracheal catheter secretions at various times post-exposure. Samples were tested for M. hyopneumoniae using a species-specific real-time PCR. A proportion of 58, 51, 52, 19, and 2% females were detected positive at 30, 60, 120, 180 and 240 dphc, respectively. Noteworthy, a greater proportion of gilts exposed at the off-site GDU were detected PCR positive for M. hyopneumoniae at each sampling event, compared to sows. In this study, assaying for genetic material in live female pigs showed extended detection of M. hyopneumoniae until at least 240 dphc. This data suggests persistence of M. hyopneumoniae longer than previously reported and highlights the importance of performing diagnostic testing to confirm negativity to the bacterium, prior to opening sow herds, especially late in the herd closure timeline.

Complete genome sequence of Mycoplasma hyopneumoniae strain 168.

Mycoplasma hyopneumoniae strain 168, a pathogenic strain prevalent in China, was isolated in 1974. Although this strain has been widespread for a long time, the genome sequence had not been determined. Here, we announce the complete genome sequence of M. hyopneumoniae strain 168.

Multiple-locus variable-number tandem-repeat analysis is a suitable tool for differentiation of Mycoplasma hyopneumoniae strains without cultivation.

An assay based on multiple-locus variable-number tandem-repeat analysis allowed differentiating and studying diversity and persistence of Mycoplasma hyopneumoniae strains in pig herds without prior cultivation. The test had a discriminatory index of >0.99 and was applied reliably to porcine bronchoalveolar lavage fluid and tracheal swabs.

Seroprevalence of Mycoplasma hyopneumoniae in pigs in subtropical southern China.

Enzootic pneumonia caused by Mycoplasma hyopneumoniae is a severe disease of pigs, causing significant economic losses to the pig industry worldwide, including the tropical and subtropical regions. In order to obtain the baseline prevalence of M. hyopneumoniae in pigs from intensive farms in southern China, double-sandwich enzyme-linked immunosorbent assay (ELISA) was used to detect M. hyoneumoniae antibodies in 460 pig serum samples collected from 12 administrative cities in China's southern Guangdong province. According to the proportions of the infected animals, among the 12 intensive farms, only two of them showed no infection of M. hyoneumoniae and the seroprevalence ranged from 0% to 90%, with an averaged prevalence of 45.7%. The highest prevalence was found in breeding boars (68.8%), followed by sows (54.5%). These data showed that the infection of pigs with M. hyopneumoniae is severe, and boars might be more important carriers and transfers of M. hyoneumoniae than sows. Integrated strategies and measures should be taken to control the infection of pigs with M. hyopneumoniae in southern China.

Pooled-sample testing for detection of Mycoplasma hyopneumoniae during late experimental infection as a diagnostic tool for a herd eradication program.

Early and accurate detection of Mycoplasma hyopneumoniae infection in live pigs is a critical component to measure the success of disease eradication strategies. However, the imperfect sensitivity of in vivo diagnostic tools, change in sensitivity over the course of infection, and expected low prevalence level at the end of an eradication program create a challenging diagnostic scenario. Here, the individual and pool sensitivities for detection of M. hyopneumoniae during the chronic phase of infection was determined using deep tracheal catheter samples, the in vivo sample type with the highest reported diagnostic sensitivity. Fifty samples from known infected pigs collected at 113 days post-M. hyopneumoniae intra-tracheal inoculation, were diluted in known negative samples to form pools of 1:3 and 1:5. Samples were tested for M. hyopneumoniae by a species-specific PCR. Ninety-eight percent (49/50) of individual samples, 84 % (42/50) of pools of 1:3, and 82 % (41/50) of 1:5 were detected positive for M. hyopneumoniae. To apply the sensitivity estimates for detection of M. hyopneumoniae in a low prevalence scenario, sample sizes with associated sample collection costs were calculated for individual and pooled testing using algorithms within the program EpiTools One-Stage Freedom Analyses. Assumptions included a ≥95 % population sensitivity, infinite population size, prevalence levels of ≥0.5 %, ≥1 %, ≥2 %, ≥3 %, ≥4 %, or ≥5 %, 100 % specificity, along with the mean and lower confidence limit of the individual or pool sensitivity for each pool size, when appropriate. For instance, following completion of a herd eradication program, if a low risk approach is targeted, sample size estimates for ≥2 % prevalence using the lower limit of the diagnostic or pool sensitivity 95 %CI may be followed. If samples were to be tested individually, 167 individuals would be sampled at a cost of 6,012 USD. If pooled by 3, 213 would be sampled (testing cost 3,266 USD), and for pools of 5, 220 individuals would be sampled (testing cost 2,464 USD). Population sensitivity was also calculated for a range of testing scenarios. Our study indicated that pooling samples by 3 or 5 was a cost-effective method for M. hyopneumoniae detection in low prevalence scenarios. Cost-effective detection was evidenced despite the increased sample collection costs associated with large sample sizes in order to offset decreased testing sensitivity attributable to pooling. The post-eradication sample collection scheme, combined with pooling, suggested lower cost options than individual sampling for testing to be applied at the end of an eradication program, without significantly compromising the likelihood of detection.

Antimicrobial susceptibility monitoring of Mycoplasma hyopneumoniae isolated from seven European countries during 2015-2016.

Mycoplasma hyopneumoniae is the causative agent of porcine enzootic pneumonia, a chronic respiratory disease, causing significant economic losses. Results from the 2015-2016 MycoPath pan-European antimicrobial susceptibility monitoring survey of M. hyopneumoniae are presented. In total, 147 M. hyopneumoniae porcine isolates from Belgium, France, Germany, Great Britain, Hungary, Italy, and Spain were tested. One isolate per farm was retained from pigs that had not been recently treated with antimicrobial agents. The minimal inhibitory concentration (MIC) of 13 antimicrobial agents was determined in a central laboratory using a broth microdilution method, with Friis Medium, incubated at 35 ± 1 °C for 5-12 days. M. hyopneumoniae NCTC 10110 was used as Quality Control. MIC50/MIC90 (mg/L) values were: enrofloxacin 0.06/1; marbofloxacin 0.06/2; spiramycin 0.06/0.25; tulathromycin ≤0.001/0.004; gamithromycin 0.06/0.5; tylosin 0.016/0.06; tilmicosin 0.06/0.5; florfenicol 0.5/1; doxycycline 0.25/1; oxytetracycline 0.25/2; lincomycin 0.06/0.25; tiamulin 0.016/0.06 and valnemulin ≤0.001/0.004. Compared with the data from 2010 to 2012 MycoPath study (50 isolates), MIC50/90 results were similar and the majority were within ± two dilution steps, except for the MIC50 of oxytetracycline which is more than two dilution steps higher in the present study. Between-country comparisons show some differences in the MIC values for the fluoroquinolones, tulathromycin and tylosin, but the limited sample size per country precludes performing meaningful country comparisons for several countries. Standardized laboratory methods and interpretive criteria for MIC testing of veterinary mycoplasmas are clearly needed; there are currently no clinical breakpoints available to facilitate data interpretation and correlation of MICs with in vivo efficacy.