Evaluating the dynamics and efficacy of a live, attenuated Mycoplasma anserisalpingitidis vaccine candidate under farm conditions.

The aim of the present study was to monitor the dynamics and to measure the safety and efficacy of a live, attenuated, thermosensitive Mycoplasma anserisalpingitidis vaccine candidate, namely MA271, in geese breeder flocks under field conditions. Two rearing flocks were vaccinated with MA271 at 4 weeks of age and boosted at 24 weeks of age by cloaca inoculation (1 ml) and eye-dropping (60 µl). The geese then were transported to multi-aged breeding farms. Two breeding flocks served as controls. Colonization of the cloaca by MA271 showed 75% maximum prevalence between 4 and 6 weeks after the first vaccination. Then the prevalence decreased to 25% until the cooler, humid fall months which coincided with the booster vaccination. Boosting raised cloacal colonization to 100%. No clinical signs were observed in the vaccinated birds. After transportation to five multi-aged breeding farms, the wild-type strain appeared as well as MA271 in three flocks. In one flock, the wild-type strain completely displaced MA271, while in one flock only MA271 was detected. Only wild-type strains were detected in the control flocks; however, due to an HPAI outbreak, both flocks were exterminated before the end of the study. Based on the available data, the median percentage of infertile eggs was 3.7-5.1% in the MA271 vaccinated flocks, and 7.7% in the non-vaccinated flock. In conclusion, MA271 can colonize the cloaca of geese under field conditions. MA271 proved to be safe and presumably protects against M. anserisalpingitidis-induced reproduction losses.

In vitro susceptibility of Mycoplasma iowae isolates to antimicrobial agents.

ABSTRACTMycoplasma iowae, a potential re-emerging avian pathogen mainly affecting turkeys, has been reported from many parts of the world. Poor hatchability, embryonic death, joint and skeletal abnormalities, poor ossification, runting-stunting, poor feathering and airsacculitis may be observed in infected flocks. The reduction of the severity of clinical signs and short-term control of M. iowae are performed by antibiotic treatment. However, M. iowae develops resistance more rapidly and is considered to be more resistant to antimicrobials than other avian pathogenic mycoplasmas. The aim of the present study was to determine the in vitro susceptibility of 101 M. iowae isolates and strains to ten clinically important antimicrobial agents, and to analyse and compare the susceptibility patterns of isolates of various origins and from a wide time-period. The examined reference strains showed high susceptibility to all antimicrobials except for spectinomycin. Low concentrations of tiamulin, florfenicol and oxytetracycline inhibited the growth of the clinical isolates. Nevertheless, slow tendency of increasing minimum inhibitory concentration (MIC) values was observed over time in the case of the above mentioned agents, while MIC values of enrofloxacin showed relatively rapid changes. Spiramycin, erythromycin, tilmicosin, tylosin, lincomycin and spectinomycin did not inhibit the bacterial growth in most of the cases. Isolates originating from captive game birds showed similar susceptibility profiles to isolates from industrial turkey hosts. The widely detected low susceptibility of M. iowae isolates to macrolides, lincomycin and spectinomycin, and the increase of MIC values of frequently used antimicrobials against this pathogen, emphasize the importance of targeted antibiotic therapy.RESEARCH HIGHLIGHTSAntimicrobial susceptibilities of 101 Mycoplasma iowae isolates were determined.Minimum inhibitory concentrations were determined by broth micro-dilution method.Tiamulin, oxytetracycline and florfenicol showed low MIC values.Isolates rapidly adapted to antimicrobial pressure.

Development and evaluation of temperature-sensitive Mycoplasma anserisalpingitidis clones as vaccine candidates.

Mycoplasma anserisalpingitidis is economically the most important pathogenic Mycoplasma species of waterfowl in Europe and Asia. The lack of commercially available vaccines against M. anserisalpingitidis had prompted this study with the aim to produce temperature-sensitive (ts+) clones as candidates for an attenuated live vaccine. The production of ts+ clones was performed by N-methyl-N'-nitro-N-nitrosoguanidine (NTG)-induced mutagenesis of Hungarian M. anserisalpingitidis field isolates. The clones were administered via eye-drop and intracloacally to 33-day-old geese. Colonization ability was examined by PCR and isolation from the trachea and cloaca, while the serological response of the birds was tested by ELISA. Pathological and histopathological examinations were performed in the eighth week after inoculation. Whole-genome sequence (WGS) analysis of the selected clone and its parent strain was also performed. NTG-treatment provided three ts+ mutants (MA177/1/11, MA177/1/12, MA271). MA271 was detected at the highest rate from cloacal (86.25%) and tracheal (30%) samples, while MA177/1/12 and MA271 elicited remarkable serological responses with 90% of the birds showing seroconversion. Re-isolates of MA271 remained ts+ throughout the experiment. Based on these properties, clone MA271 was found to be the most promising vaccine candidate. WGS analysis revealed 59 mutations in the genome of MA271 when compared to its parent strain, affecting both polypeptides involved in different cellular processes and proteins previously linked to bacterial fitness and virulence. Although further studies are needed to prove that MA271 is in all aspects a suitable vaccine strain, it is expected that this ts+ clone will contribute to the control of M. anserisalpingitidis infection.RESEARCH HIGHLIGHTS Three M. anserisalpingitidis ts+ vaccine candidates were produced by NTG-mutagenesis.Clone MA271 was able to colonize geese and induce a serological response.MA271 re-isolates remained ts+ during the 8-week-long experiment.WGS analysis revealed 59 mutations in the genome of MA271.