Birds that roam freely, particularly those that migrate, have the potential to carry a range of diseases that can be passed on to humans. The vast movement of these birds across diverse environments and urban areas can contribute to the spread of bacteria over long distances, impacting both human and animal populations. Stress, overcrowding, and human interaction can also play a role in the transmission of infectious diseases among birds and humans. Therefore, it is crucial to comprehend the intricate connections between birds, vectors, zoonotic pathogens, and the environment, especially given the increasing urbanization and emergence of zoonotic illnesses. This review aims to provide a systematic overview of the significance of avian species in transmitting bacterial pathogens that pose a risk to public health.

During the recent years, an immense increase in the number of food poisoning cases in people caused by Campylobacter (C.) species has occurred. Raw milk, next to poultry meat, is considered the most frequent cause of food poisoning in people caused by the subject bacteria, although it is not always possible to isolate Campylobacter cells from the incriminated milk. Most probably this difficulty is caused by low concentration of the pathogen in milk at the level of 2/3 cells/ml although even such low concentration represents risk to human health. The present study was aimed at determining the occurence of Campylobacter bacteria in milk originating from selected regions of Poland. The isolation method applied in this work was effective in recovering as few as 0.1 cell of Campylobacter per g of food. Among 150 bulk milk samples tested, Campylobacter spp. was isolated from 7 (4.6%) ones. The biochemical identification of the isolated strains conducted by means of conventional biochemical tests as well as by applying the API - Campy tests revealed that all the isolates belonged to the C. jejuni species. Determination of resistance to antibiotics was performed by means of the diffusion disks method for the following antibiotics: gentamicin, ciprofloxacin, ampicillin, chloramphenicol, erythromycin, doxycyclin and tetracycline. Among 7 isolates tested, all were susceptible to ampicillin, chloramphenicol, erythromycin and gentamicin, 28.5% to doxycyclin and 14.2% to tetracycline and ciprofloxacin.

The aim of this study was to determine the pathogenic markers associated with Campylobacter infection in humans. A total of 104 Campylobacter isolates obtained from poultry and humans were examined for the presence of nine virulence genes and their ability to adhere to, invade and produce cytotoxin were defined using HeLa cells. The diversity of the Campylobacter spp. isolates was studied based on sequencing of the SVR-region of flaA gene. Altogether 45 flaA-SVR alleles were identified among 104 Campylobacter isolates of poultry and human origin. All Campylobacter isolates possessed flaA, cadF and racR genes involved in adherence. Accordingly, all poultry and human isolates exhibited adherence towards HeLa cells at mean levels of 0.95% and 0.82% of starting viable inoculum, respectively. The genes involved in invasion (iam and pldA) and cytotoxin production (cdtA, cdtB and cdtC) were also widely distributed among the human and poultry Campylobacter isolates. Significantly higher invasiveness was observed for poultry isolates (mean level of 0.002% of starting bacterial inoculum) compared to human isolates (0.0005%). Interestingly the iam gene, associated with invasion, was more common in human (100%) than poultry (84%) isolates, and the poultry isolates lacking the iam gene showed a marked reduction in their ability to invade HeLa cells. Moreover, virB11 was present in 22% of the poultry and 70.4% of the human isolates. Strains lacking virB11 showed a slight reduction in invasion, however in the absence of iam even the poultry isolates containing virB11 were unable to invade HeLa cells. The mean cytotoxicity of Campylobacter isolates from poultry and human was 26.7% and 38.7%, respectively. Strains missing both the cdtB and cdtC genes were non-cytotoxic compared to strains containing all three cdtABC genes, which were the most cytotoxic among the C. jejuni and C. coli isolates from both sources. No cytotoxic effect was observed in only 4% of poultry and 5.6% of human isolates.

A total of 240 samples were evaluated for the presence of Campylobacter spp. Campylobacter was found in 83.3% of the cecum contents samples and 52.5% of the neck skin samples from carcasses. The prevailing species was C. jejuni, accounting for 87.7% of all Campylobacter isolates, and the remaining 12.3% of isolates were C. coli. All Campylobacter isolates, independent of the sample origin and species, were positive for 6 out of 15 tested genes (flaA, flhA, cadF, racR, ciaB, and cdtA genes). The prevalence of dnaJ, docA, pldA, cdtB, cdtC, and iam genes was also very common (ranging from 86.5% to 98.8%). The lowest prevalence was noted for virB11 and wlaN genes, both in Campylobacter isolates from cecum (12% and 19%) and carcasses (11.1% and 17.5%). None of the isolates tested, regardless of the sample origin, carried the cgtB gene. The highest resistance rates were observed for quinolones (90.8%) and tetracyclines (79.8%). Simultaneously, only single Campylobacter isolate was resistant to macrolides (0.6%) and none of the isolates showed resistance to aminoglycosides and amphenicols. The common presence of Campylobacter on geese carcasses as well as the detection of multidrug-resistant isolates indicate that consuming goose meat might cause a potential risk, therefore leading to human campylobacteriosis.

Background: The aim of the study was to determine whether free-living birds belonging to game species whose meat is used for human consumption can constitute a reservoir of pathogenic Campylobacter strains, spreading these bacteria to other hosts or directly contributing to human infection. Methods: A total of 91 cloacal swabs were taken from different species of wildlife waterfowl to estimate the Campylobacter prevalence, the genetic diversity of the isolates, and the presence of virulence genes and to evaluate the antimicrobial resistance. Results: The presence of Campylobacter spp. was confirmed in 32.9% of samples. Based on flaA-SVR sequencing, a total of 19 different alleles among the tested Campylobacter isolates were revealed. The virulence genes involved in adhesion were detected at high frequencies among Campylobacter isolates regardless of the host species. The highest resistance was observed for ciprofloxacin. The resistance rates to erythromycin and tetracycline were observed at the same level. Conclusions: These results suggest that wildlife waterfowl belonging to game species may constitute a reservoir of Campylobacter, spreading these bacteria to other hosts or directly contributing to human disease. The high distribution of virulence-associated genes among wildlife waterfowl Campylobacter isolates make them potentially able to induce infection in humans.