Actinobacillus pleuropneumoniae is a prevalent respiratory pathogen causing substantial economic losses in swine production worldwide. The bacterium's ability to rapidly develop antimicrobial resistance (AMR) poses a significant challenge to effective treatment and control. In Poland, limited data on A. pleuropneumoniae serotype distribution and AMR patterns hinder evidence-based treatment strategies. This study examined the serotype diversity and AMR patterns of A. pleuropneumoniae isolates from porcine pleuropneumonia outbreaks in northeastern Poland between 2019 and 2024, providing crucial information for regional veterinary practices and antimicrobial stewardship efforts. Analysis of 119 isolates from 67 farms demonstrated the predominance of serotype 2 (65.5%), followed by serogroups 3, 6, 8 (18.5%) and 1, 9, 11 (15.1%). This distribution differs from recent trends in other European countries, suggesting regional epidemiological variations. High resistance rates were observed for tylosin (55.5%), gentamicin (36.1%), doxycycline (32.8%), and sulfamethoxazole/trimethoprim (26.1%). Multidrug resistance fluctuated between 14.3% and 21.9% over the study period, with no clear linear trend. From 2022 onwards, strains exhibiting resistance to seven or more antimicrobials, including cephalosporins, emerged, marking a significant shift in resistance profiles. Temporal analysis revealed diverse resistance patterns, with significant increases in some antimicrobials (e.g., sulfamethoxazole/trimethoprim, p = 0.001) and stability in others (e.g., tetracycline, p = 0.890). Notably, several antimicrobials, including florfenicol and colistin, maintained 100% efficacy against all isolates throughout the study period. The findings highlight the dynamic nature of AMR development in A. pleuropneumoniae and underscore the need for ongoing surveillance in the region. The emergence of highly resistant strains, particularly those resistant to cephalosporins, raises concerns about future treatment options. These results can guide evidence-based treatment strategies and enhance antimicrobial stewardship efforts in regional swine production. Furthermore, the study emphasizes the importance of local AMR data in guiding antimicrobial use policies and the need for a coordinated approach to combat AMR in veterinary medicine.

Listeria spp. contamination in food, particularly antimicrobial-resistant strains, poses an escalating concern for public health. This study investigated the prevalence and antimicrobial resistance profiles of Listeria spp. isolated from raw fish collected from diverse sources in Northern Poland. A total of 750 raw fish samples were collected from standing freshwater tanks, flowing freshwater reservoirs, and a saltwater reservoir. Isolation was performed following the standard protocol, which describes the horizontal method for detecting Listeria spp., including Listeria monocytogenes. The antimicrobial resistance profiles of isolated strains were performed using the disk diffusion method. Antimicrobial resistance genes were identified using PCR, targeting 11 genes associated with resistance to β-lactams, macrolides, glycopeptides, and sulfonamides. Statistical analyses included Phi correlation coefficients, hierarchical clustering, and logistic regression to examine associations between phenotypic resistance patterns and antimicrobial resistance genes. Listeria spp. was isolated from 13.9% of samples (104 positive samples), comprising L. seeligeri (34.6%), L. welshimeri (28.8%), L. monocytogenes (23.1%), and L. innocua (13.5%). Phenotypic antimicrobial susceptibility testing revealed universal resistance to oxacillin (100%) across all Listeria spp. isolates. High resistance levels were also observed for cefotaxime (97.1%), cefoxitin (92.3%), rifampicin (92.3%), clindamycin (96.2%), and trimethoprim-sulfamethoxazole (91.3%). Alarmingly, 98.1% of all Listeria spp. isolates exhibited multidrug resistance (MDR), reaching 100% MDR among L. monocytogenes isolates. Specifically, L. monocytogenes isolates exhibited complete resistance to meropenem, cefoxitin, cefotaxime, rifampicin, and trimethoprim-sulfamethoxazole, and significant resistance to ciprofloxacin (91.7%), clindamycin (83.3%), tetracycline (75.0%), erythromycin (75.0%), benzylpenicillin (70.8%), and nitrofurantoin (70.8%). Molecular analysis identified blaTEM (100%), ampC (37.5%), and ereB (37.5%) as the most prevalent antimicrobial resistance genes in L. monocytogenes. The exceptionally high prevalence of multidrug-resistant Listeria spp., particularly L. monocytogenes, in raw fish underscores a critical public health risk, suggesting the urgent need for ongoing surveillance and robust risk mitigation strategies in aquaculture and seafood processing. The elevated antimicrobial resistance levels may also indicate aquatic environmental contamination, warranting further investigation into the sources and broader ecological implications of antimicrobial resistance in these ecosystems.

Porcine respiratory disease complex (PRDC) significantly impacts the swine industry worldwide, leading to economic losses due to poor growth performance, reduced feed efficiency, higher medication costs, and adversely affecting pig welfare by causing clinical symptoms such as fever, cough, loss of appetite, lethargy, and dyspnea. Cranio-ventral pulmonary consolidation (CVPC) and pleuritis are the most frequent macroscopic lung lesions observed in PRDC and are indicators of decreased animal welfare. This study aimed to quantify the effects of CVPC and pleurisy on carcass weight, meatiness, and average daily carcass weight gain (ADCWG) in fattening pigs, thereby assessing their impact on both production and welfare. A total of 679 slaughtered pigs from seven batches (farms) were evaluated for lung lesions at slaughter. We employed a mixed-model analysis to assess the correlation between lung lesions and production parameters across the farms. The mean prevalence of lesions was 23.86% for CVPC and 15.46% for pleurisy, indicating a significant presence of respiratory disease affecting animal welfare. Pigs with severe lung lesions (≥ 15.1%) exhibited significantly lower ADCWG compared to pigs without lesions (0.951 kg/day vs. 0.997 kg/day, p = 0.024), reflecting reduced growth performance and welfare. The mixed-effects model revealed that lesions in the right apical lobe and dorso-caudal pleurisy were associated with significant reductions in carcass weight (− 2.77 kg and − 2.29 kg, respectively) and carcass meat (− 1.76 kg and − 1.43 kg, respectively). An economic analysis under average market price conditions demonstrated that severe lung lesions could lead to financial losses of up to 11.53 EUR per 100 kg of meat, emphasizing the economic impact of compromised welfare due to respiratory diseases. This study provides quantitative evidence of the negative impact of CVPC and pleurisy on carcass weight and meatiness in fattening pigs. The findings underscore the importance of effective respiratory disease management in swine production, highlighting potential areas for targeted interventions to improve animal health and economic outcomes.

Although the prevalence of respiratory diseases in slaughter pigs ranges from 19% to 74% and continues to be an important concern for swine herds worldwide, only a few studies have investigated the relationship between respiratory disease and pork quality. The general aim of this study was to investigate associations between the prevalence and severity of enzootic pneumonia-like lesions in Polish slaughter pigs on different carcass and meat-quality characteristics at the animal and herd levels. The average prevalence of bronchopneumonic lungs with different degrees of lesions was 94.57%. The majority of lesions indicated the acute stage of enzootic pneumonia. Our results indicate a statistically significant interaction between the mean weight of carcasses depending on the extent of the lesions (p = 0.04) at the animal level. The correlation between meatiness and severity of lung lesions was r = −0.25 (p = 0.00). The correlation between the extent of lung lesions and pH₄₅ value was r = −0.17 (p = 0.005) on the animal level and r = −0.63 (p = 0.017) at the herd level. This implies that lung lesions in slaughter pigs negatively influence not only animal health and welfare, but also carcass quality.

The presence of Listeria spp. in raw fish poses a significant food safety risk, primarily due to the pathogenic potential of Listeria monocytogenes. Howeve