The first record of mcr-1 gene for colistin resistance in pigs from Serbia: should we be worried?

Colistin is being used as a last-resort drug to treat infections caused by multidrug-resistant (MDR) bacteria in humans. In veterinary medicine, colistin has been used for the treatment and prevention of infectious diseases. In the first study of mcr genes by multiplex PCR in healthy pigs from Serbia, we discovered mcr-1 in 4.85% out of 350 fecal samples. The presence of mcr-1 gene was detected on three farms located less than 100 km apart from each other, predominantly in piglet samples. The results point to the necessity of monitoring of colistin resistance and the mcr genes in food producing animals as well as restricting colistin usage on farms.

Subtyping Blastocystis in pigs and humans revealed unusual avian-specific subtype ST6 in humans in Serbia

Blastocystis is a common protist colonizing the gastrointestinal tract of humans and various animals. The first subtyping of Blastocystis isolates in pigs and humans in Serbia revealed unusual avian-specific subtype ST6 in humans. In total, 48 pig faecal specimens collected on seven pig farms and 50 human faecal specimens positive to Blastocystis by microscopic examination were selected for the study. Eleven randomly selected PCR-positive pig samples and 10 samples from human patients (with gastrointestinal complaints) were subjected to SSU rDNA sequencing. Three subtypes were identified (ST3, ST5 and ST6) by phylogenetic analysis. ST5 was found in all pig samples; while in human samples, we detected ST3 and ST6. The latter subtype is relatively uncommon in Europe and highly adapted to avian hosts; therefore, the possibility of sporadic zoonotic transmission to human patients should not be ignored.

Vaccination of broilers against Newcastle disease in the presence of maternally derived antibodies

Objective: The aim of this study was to evaluate the efficacy of a live attenuated vaccine against Newcastle disease in broilers with different levels of maternally derived antibodies (MDA). While vaccination remains the single most important means for controlling Newcastle disease, presence of MDA may interfere with the vaccination of young birds and decrease the efficacy of the vaccine. Materials and methods: Day-old chicks with variable levels of MDA (negative, low and high) were vaccinated with a live attenuated vaccine against Newcastle disease. Three most commonly used inoculation routes were compared; oculonasal, spray and oral (drinking water). Onset and duration of immunity were measured by serology and challenge with virulent virus. Results: Immune response in vaccinated MDA-positive birds was delayed in comparison with SPF controls. Protection was well established already at 14 days post vaccination in SPF birds while in MDA-positive birds it was 1–2 weeks delayed and was lower throughout the study. Non-vaccinated MDA-positive birds lost passive protection completely at 3–4 weeks of age and were significantly more susceptible to challenge than vaccinated hatch mates at all test points. The protection rate increased in vaccinated birds towards the end of the experiment and reached 70–100 % at the last test points (35–42 days of age). Correlation of haemagglutination inhibition (HI) titre vs. protection rate revealed the importance of cellular and local immunity as most of the vaccinated birds with low HI titre were protected, contrary to their unvaccinated hatch mates with the same HI titre. Oculonasal route seems to provide slightly better protection than the other two routes. Conclusions and clinical relevance: Although immune protection in vaccinated MDA-positive birds may be decreased or delayed, vaccination still provides high protection against ND challenge in comparison with the unvaccinated hatch mates. The degree of interference seems to be proportional to the level of MDA. Vaccination schedules therefore need to be designed according to the immune status of the flock.