Search Results (111)

The widespread use of antimicrobial drugs (AMDs) in livestock production contributes to antimicrobial resistance (AMR), a global One Health concern affecting humans, animals, and the environment. This study analyzed AMD residues and the AMR profiles in Escherichia coli and Enterococcus spp./Streptococcus spp. (ES) isolated from lagoon water samples collected from nine California dairies. Antimicrobial susceptibility testing was performed using the microbroth dilution method, and enzyme-linked immunosorbent assay (ELISA) kits were used to detect AMD residues in lagoon water. Overall, residues of florfenicol and tilmicosin were detected in more than 90% of the samples, while tetracycline was detected in 74.2 ± 4.6% of the samples. In contrast, penicillin and sulfamethazone residues were low, observed in only 3.4 ± 1.9% and 32.3 ± 5.0% of samples, respectively. The very low prevalence of penicillin was likely due to limited use in dairy cattle, given its prolonged withdrawal period. Prevalence estimates for AMR in the lagoon samples showed 100% resistance of E. coli to tiamulin, tilmicosin or tylosin and high prevalence against florfenicol (96.0% ± 2.0) or gamithromycin (92.0% ± 1.9). However, low AMR estimates (less than 10%) were observed against other AMDs tested. Similarly, the prevalence estimates for AMR of ES isolates in the studied lagoon were high against florfenicol (95.1% ± 2.0), tildipirosin (97.6% ± 1.7), or tilmicosin (98.8% ± 1.2), but low against ampicillin (4.9% ± 1.9) and penicillin (8.5% ± 2.4). Despite numerical differences in AMR prevalence by season, region, and sampling point, these variations were not statistically significant. Logistic regression models were applied to explore associations between AMD residues and AMR phenotypes where appropriate. Tilmicosin residues were significantly associated with reduced resistance to danofloxacin, enrofloxacin, and tildipirosin in E. coli isolates, while sulfamethoxazole residues were linked to increased tetracycline resistance in Enterococcus spp. The presence of florfenicol residues, potentially originating from treated calves and heifers, helps explain the high prevalence of resistance to this drug in both bacterial species. However, not all AMD residues were associated with AMR, underscoring the complex ecological and genetic factors involved in the development and maintenance of resistance in dairy environments. These findings underscore the importance of integrating AMR surveillance and prudent AMD use practices across all segments of dairy production systems. Full article

Antibiotic residues in poultry pose health and resistance risks, necessitating breed-specific WDTs. In this study, the residue elimination patterns of seven antibiotics in Taihang chicken tissues under free-range conditions were studied and the appropriate WDT was formulated. A total of 240 healthy Taihang chickens aged 100 days were randomly divided into 8 groups, each comprising 30 chickens. Chickens in groups 1 to 7 were administered oxytetracycline, chlortetracycline, erythromycin, tylosin, tylvalosin, lincomycin, and tiamulin, respectively. Regarding the administration method, we adopted the highest dose and maximum course of treatment recommended by the Veterinary Pharmacopoeia of the People’s Republic of China. Group 8 served as the control group. Muscle, sebum, liver, and kidney samples were collected at 4 h, 1 d, 2 d, 3 d, 5 d, 7 d, 10 d, 13 d, and 16 d after drug withdrawal. Our results demonstrated that the drug residues after drug withdrawal gradually decreased with the increase in drug withdrawal days, and the elimination rate in the early stage of drug withdrawal was significantly faster than that in the later stage. At 4 h after drug withdrawal, the drug residues in various tissues reached their highest values. In most cases, the drug concentrations in the kidney and liver were higher than those in the muscles and sebum; however, some drugs also exhibited concentration peaks in the sebum. On the first day of drug withdrawal, the amount of residues in various tissues decreased rapidly. In general, the elimination rate of various drugs in the muscles, liver, and kidneys is faster but slower in the sebum. Based on the WDT calculation software WT1.4, the recommended WDTs for oxytetracycline, chlortetracycline, erythromycin, tylosin, tylvalosin, lincomycin, and tiamulin chickens are 4 d, 5 d, 11 d, 8 d, 13 d, 13 d, and 7 d, respectively. These findings support food safety and industry development. Full article

Background: Antimicrobial resistance (AMR) is an escalating concern in both human and veterinary medicine, particularly in the poultry sector, where antibiotic usage is substantial. Streptococcus spp. and Staphylococcus aureus are important pathogens in waterfowl, causing systemic infections. However, there is a significant lack of data regarding their antimicrobial susceptibility patterns in waterfowl populations. This study aims to address this gap by determining the minimum inhibitory concentrations (MICs) of isolates from Hungarian waterfowl farms and evaluating resistance patterns in clinical isolates. Methods: A total of eight S. aureus and 19 Streptococcus isolates were collected from ducks and geese between 2022 and 2023. Antimicrobial susceptibility testing was performed for 15 antimicrobials using the broth microdilution method. Potential associations between MIC values were analyzed using Spearman’s rank correlation test. Results: High MIC values were observed for tetracyclines, phenicols, and fluoroquinolones, in the case of Streptococcus, with 89.5% of isolates exhibiting resistance to doxycycline, 63.2% to florfenicol, and in the case of S. aureus, 25.0% to enrofloxacin. In the case of Streptococcus, a strong positive correlation was identified between tylosin and tiamulin (0.88, p < 0.001), as well as between tylosin and lincomycin (0.75, p < 0.001). A moderate correlation was observed between doxycycline and spectinomycin (0.72, p = 0.03), suggesting potential co-selection mechanisms. Conclusions: Our findings emphasize the necessity of continuous AMR surveillance in the waterfowl industry, particularly for multidrug-resistant strains. Understanding cross-resistance patterns is crucial for developing targeted control measures, and future studies should incorporate whole-genome sequencing to elucidate resistance determinants and co-selection mechanisms. This study highlights the potential public health and veterinary risks associated with AMR in waterfowl and reinforces the importance of responsible antibiotic use and the development of alternative therapeutic strategies in veterinary practice. Full article

Introduction: Tylosin, a veterinary antimicrobial belonging to the macrolide family, is commonly used in the poultry industry. Residues generated from its use can be present in the litter and droppings of treated birds. Due to the diverse uses of poultry byproducts, such as fertilizing agricultural soils or incorporation into the diets of other animal species, there is a risk to public health, as the presence of antimicrobial residues favors the development of antimicrobial resistance, which is a global problem. Objective: This study aimed to evaluate the dissemination of tylosin residues from the litter and droppings of treated birds and untreated birds in a controlled broiler environment. Methods: Bird droppings and litter samples were collected and analyzed using HPLC-MS/MS to detect and quantify tylosin residues. Results: The residue concentrations detected in the dropping matrix only exceeded the Limits of Quantification (LOQ = 4 µg kg⁻¹) in the treated group. The litter matrix had statistically significant differences between the study groups. The persistence of tylosin residues in the litter of birds at day 42 was 290.16 µg kg⁻¹ in the treated group (A) and 9.35 µg kg⁻¹ in the adjacent untreated group (B.1). Conclusions: The results indicate that exposure distance influences tylosin residue dissemination. Full article

This study evaluates the effects of a proprietary tannin blend (BX), supplemented with or without sodium monensin (MON), on beef cattle performance, carcass traits, and health. Steers (n = 2986; initial shrunk body weight (SBW) 254 ± 9.2 kg) were allocated into 48 pens (61–62 steers/pen; 12 pens/treatment) fed for 230 d. Treatments included: (1) no feed additives (CTL); (2) BX (7.95 g/animal daily); (3) MON + Tylosin phosphate (TYL; 437.52 mg MON/animal daily + 80 mg TYL/animal daily); or (4) MON + BX (437.52 mg MON/animal daily + 7.95 g BX/animal daily). Data were analyzed in R 4.2.1 using a randomized block design with pen as the experimental unit. Dry matter intake was lower (p < 0.001) in MON + TYL and MON + BX than in CTL. Steers fed MON + BX had greater carcass-adjusted final SBW (p = 0.002), average daily gain (p = 0.002), fat thickness (p = 0.035), and marbling score (p = 0.046) than BX. Feed conversion improved in MON + TYL and MON + BX (p < 0.001). CLT and BX had higher (p < 0.001) liver abscess prevalence compared to MON + BX and MON + TYL. The addition of BX did not improve the parameters measured. Steers fed MON + BX showed reduced liver abscesses and similar feed efficiency compared to MON + TYL. Full article

Bacteriological examination of uterine secretions provides essential information for the prevalence of bovine uterine pathogens and their influence on fertility. The objective of the present study was to determine the uterine pathogens in cases of clinical endometritis in two Holstein-Friesian dairy farms between 21 and 27 days after calving and the minimum inhibitory concentration (MIC) of 14 antimicrobials for Trueperella pyogenes (T. pyogenes). Overall, the prevalence of T. pyogenes (Farms A and B) was 46.3% and 22% (p < 0.01), respectively. In contrast, Farm B had significantly more cases (p < 0.001) of Escherichia coli, but the distribution of uterine pathogens was similar. Regarding the prevalence of any bacteria, Farm B also had significantly more bacteria (p < 0.001) than Farm A. T. pyogenes isolates were highly susceptible to amoxicillin, amoxicillin/clavulanic acid, tylosin, and cephalosporins, such as ceftiofur, cefquinome, and cephalexin with MIC₉₀ of ≤2 μg/mL. At the same time, MIC₉₀ of tulathromycin, lincomycin, and florfenicol were between 4 and 8 μg/mL and of doxycycline, enrofloxacin, oxytetracycline, and gentamicin, were between 16 and 32 μg/mL, respectively. Meanwhile, sulfamethoxazole/trimethoprim showed the highest MIC₉₀ (>32 μg/mL). In summary, T. pyogenes with high MIC₉₀ against oxytetracycline, gentamicin, and sulfamethoxazole/trimethoprim were found, which calls attention to the prudent use of antibiotics. Full article

Background/Objectives: Since 28 January 2022, veterinary medicinal products (VMPs) must be used in accordance with the conditions of the marketing authorisation (Regulation (EU) 2019/6, Article 106). This entails further restrictions on therapeutic freedom, for example, with regard to dose deviations. Off-label use is any use of a product that deviates from the Summary of Product Characteristics (SPCs). To date, there are no data available on the type and extent of off-label use on the basis of which the feasibility of the new regulation in Germany can be assessed. Methods: Therefore, a Germany-wide anonymous online survey was conducted as a quantitative cross-sectional study comprising 196 questions according to off-label use in dogs and cats. Results: In quantitative terms, the survey was representative of 358 participants but limited due to the demographic characteristics of the participants. A total of 91.3% (326/357) veterinarians stated that they had used antibiotics off-label. Fusidic acid, chloramphenicol, tylosin, and florfenicol were most frequently reclassified with regard to animal species. Authorised drugs for cats and dogs such as amoxicillin/clavulanic acid, doxycycline, metronidazole, and fluoroquinolones, like enrofloxacin and marbofloxacin, were also used off-label, often with regard to indication and treatment duration. Conclusions: Although there are comparatively many antibacterial preparations available for cats and dogs, off-label use is common practice. In many cases, special circumstances of the individual case justify the off-label use of authorised preparations for cats and dogs. The survey results indicate that some dose revisions are recommended. Guidance for specific indications in cats and dogs could contribute to greater legal certainty in small animal practice with regard to the justification of off-label use. Full article

Enterococcus species are used as One Health indicators of antimicrobial resistance (AMR) in humans, animals, and the environment. A surveillance study in beef cows and calves isolated Enterococcus casseliflavus along with E. faecium, E. faecalis, and E. hirae. Given the high prevalence of E. casseliflavus, we elected to characterize this species to better understand its role in the antimicrobial resistance of enterococci in cows and calves. Almost 12% of E. casseliflavus isolates exhibited multidrug resistance with the majority being resistant to lincomycin (99%), followed by quinupristin–dalfopristin (34%), ciprofloxacin (9.6%), tylosin (4.5%), erythromycin (2.7%), tetracycline (1.8%), tigecycline (1.5%), daptomycin (0.6%), streptomycin (0.3%), and kanamycin (0.3%). All E. casseliflavus were susceptible to chloramphenicol, penicillin, streptomycin, nitrofurantoin, gentamicin, and linezolid. Whole genome antimicrobial resistance gene profiling identified vanC-type intrinsic vancomycin resistance genes in all E. casseliflavus, with the vanC4XYT gene cluster being dominant (67%) followed by vanC2XYT (31%) and vanC3XYT (1.5%). Resistance genes for erythromycin (ermB) and tetracycline (tetM) were rarely identified (2.1% and 1.2%, respectively) within E. casseliflavus genomes. No resistance genes were identified to explain either the quinupristin–dalfopristin or ciprofloxacin resistance in these isolates. A core genome phylogenetic tree revealed two clades that exhibited no distinct association with the age of the host, time of sample collection, or the farm sampled. The open nature of the E. casseliflavus pan-genome highlighted its intraspecies diversity. These findings suggest that E. casseliflavus is likely a low-risk species in terms of contributing to antimicrobial resistance in the cow–calf sector. Full article

The objective of this study was to determine the frequency of Salmonella in pig samples analyzed at the Veterinary Diagnostic Unit of the Faculty of Agricultural Sciences of the University of Antioquia, Colombia, between 2022 and 2023. Out of 5820 serum samples analyzed using indirect enzyme-linked immunosorbent assay, 63.76% were positive. Additionally, Salmonella was isolated and identified in a separate group of 848 samples (feces, tissues, etc.) with a positivity rate of 23.47%. Eight serotypes were identified, with the most common being Salmonella enterica subsp. enterica serotype Typhimurium (49.2%), followed by its monophasic variant I 4,[5],12:i:- (23%), and serotype Choleraesuis (18%). Antimicrobial susceptibility profiles of 105 isolates were evaluated using the Kirby–Bauer method, which demonstrated higher resistance (100%) to ampicillin, tiamulin, penicillin, tylosin, and erythromycin (these were the least tested), followed by florfenicol (44/54), doxycycline (4/5), spectinomycin (18/25), amoxicillin (32/46), chloramphenicol (2/3), tetracycline (2/3), and enrofloxacin (34/64), with lower resistance observed for fosfomycin (2/38) and ceftiofur (5/35). Multi-drug resistance was observed in 59% (62/105) of the isolates. The high proportion of Salmonella and the levels of resistance to various drugs raise significant concerns, indicating potential deficiencies in responsible antimicrobial use and management practices on pig farms in the region. Full article

Background: Antimicrobial resistance (AMR) has become a serious global challenge in the 21st century. Poultry, including turkeys, are a vital source of animal-derived protein worldwide. Commensal bacterial strains in poultry can act as reservoirs for AMR, making monitoring them crucial for both veterinary and public health. Enterococcus species are emerging pathogens, particularly in severe nosocomial infections. Methods: This study aimed to assess the resistance profiles of commensal Enterococcus strains isolated (n = 470) from large-scale turkey flocks in Hungary. From each animal, two swab samples were collected: one from the oropharyngeal region near the tracheal entrance and one from the cloaca. The samples were subsequently processed, and the minimum inhibitory concentration (MIC) was determined following the Clinical and Laboratory Standards Institute (CLSI) guidelines. The tested antibiotics included amoxicillin, amoxicillin–clavulanic acid, imipenem, neomycin, doxycycline, florfenicol, tylosin, enrofloxacin, potentiated sulfonamide, vancomycin, ceftriaxone, spectinomycin, tiamulin, lincomycin, and colistin. The dilution range for MIC determination was set between 512 and 0.001 µg/mL. Results: Resistance to amoxicillin, a first-line treatment for Enterococcus infections, was low (11.1%). However, high resistance levels were observed for tylosin (62.6%), florfenicol (51.1%), doxycycline (48.7%), and enrofloxacin (45.5%). Notably, vancomycin resistance reached 15.5%, a finding consistent with global trends. Compared to human-derived Enterococcus data, resistance to aminopenicillins was significantly lower in turkey isolates, while neomycin resistance levels were comparable to those observed in human E. faecalis strains. Conclusions: The findings underscore the necessity of continuous surveillance of AMR trends in poultry production. While amoxicillin remains an effective treatment, the presence of multidrug-resistant strains and vancomycin-resistant isolates raises concerns regarding the potential dissemination of resistance genes. Future studies should incorporate next-generation sequencing to elucidate the genetic mechanisms underlying resistance. Additionally, integrating antibiotic usage data from farms may provide further insights into resistance dynamics. Strengthening antibiotic stewardship programs and fostering collaboration between veterinary and human medicine are crucial steps in addressing AMR under the One Health framework. Full article

Typical investigations into the biological consequences of suspected xenobiotics or nutrients introduced in watersheds include analytical chemistry screens of environmental samples—such as periphyton responses or studies of fish condition—which are all costly in terms of equipment, reagents, time, and human resources. An alternative is to assess pollutant effects on waterborne bacteria. A flow cytometric method was developed to yield rapid, same-day results that could be used to proactively screen for suspected chemical inputs into watersheds using water sampling methods that are identical to those in standard use. The analytical methods are microbe cultivation-independent, for use with waterborne bacteria that are typically viable but not culturable. The procedure is quick and inexpensive, generating measures of bacterial esterase that reflect metabolic activity and are sensitive and statistically robust. After phosphate-EDTA incubation to increase cell wall permeability, staining was performed with 5(6) carboxyfluorescein diacetate (enzyme activity) and propidium iodide (cell viability) with three bacterial species in exponential phase growth having been incubated with organic wastewater compounds (atrazine, pharmaceuticals [17α-ethynylestradiol and trenbolone], and antimicrobials [tylosin and butylparaben]). This method successfully detected metabolic changes in all bacterial species, with atrazine inducing the greatest change. Additional fluorescent stains can target specific microbial structures or functions of interest in a particular watershed. This biotechnology can inform analytical chemistry and study of biota at sites of interest and has the potential to be automated. Full article

Fusobacterium necrophorum subspecies necrophorum, a resident of the rumen, is the causative agent of bovine liver abscesses. Currently, tylosin, a macrolide, is used in the feed to reduce liver abscesses. Because macrolides are medically important antibiotics, their use in food animal production is of public health concern. There is significant interest in finding antimicrobial alternatives. Bacteriophages that lyse subsp. necrophorum have the potential to replace tylosin. Our objective was to isolate bacteriophages lytic to subsp. necrophorum. Pooled ruminal fluid from slaughtered cattle and pooled sewage samples were collected and incubated overnight with lysine, and subsp. necrophorum strains and filtrates were spotted on F. necrophorum lawns. Phage plaques were harvested and purified. Bacteriophage isolation frequencies were compared between sample types, sampling dates, and necrophorum strains. Overall relative frequency of isolated bacteriophages lytic to subsp. necrophorum was 17.1%. The frequency of bacteriophage isolation ranged from 0 to 25.4% for ruminal fluid, and from 13.7 to 32.0% for sewage. Isolation frequency was significantly higher in sewage than in ruminal fluid samples (p < 0.01). Isolation rates varied significantly between necrophorum strains. Sewage was a rich source of bacteriophages lytic to necrophorum, which have the potential to be used to prevent liver abscesses. Full article

The rise in antimicrobial resistance (AMR) in Mycoplasma bovis underscores the urgent need for alternative treatments. This study evaluated the minimal inhibitory concentrations (MICs) of four metal ions (cobalt, copper, silver, and zinc) and colloidal silver against 15 clinical M. bovis isolates, alongside conventional antimicrobials (florfenicol, tetracycline, tulathromycin, and tylosin). Colloidal silver demonstrated the most effective antimicrobial activity, inhibiting 81.25% of isolates at 1.5 mg/L, while silver inhibited 93.7% of isolates at concentrations above 1.5 mg/L. Copper exhibited notable efficacy, inhibiting 37.5% of isolates at 1.5 mg/L, with a small proportion responding at 0.1 mg/L. Cobalt and zinc displayed variable activity, with MIC values ranging from 0.7 to 12.5 mg/L. In contrast, conventional antimicrobials showed limited effectiveness: tetracycline inhibited 31.25% of isolates at ≥16 mg/L, tylosin inhibited 25% at 16 mg/L, and tulathromycin MICs ranged from 0.5 to 8 mg/L. Time–kill assays revealed a reduction in M. bovis viability after eight hours of exposure to silver and colloidal silver, though higher concentrations (4×–8× MIC) were required for complete eradication. These findings highlight the significant potential of colloidal silver and copper as alternatives for treating M. bovis infections and combating AMR. Further research is essential to explore their standalone and synergistic applications for therapeutic use. Full article

Glaesserella parasuis is the etiological agent of Glässer’s disease, which causes high morbidity and mortality in pigs worldwide. Macrolide resistance poses an urgent threat to their treatment, as macrolides are widely used for preventing and treating G. parasuis infections. Here, we determined the susceptibilities to five macrolides and characterized the genetic markers of macrolide resistance. The antimicrobial susceptibility of 117 G. parasuis isolates to erythromycin, tulathromycin, gamithromycin, tylosin, and tilmicosin was evaluated using broth microdilution method. Erythromycin-resistant isolates were sequenced using whole-genome sequencing. Further analysis of these sequences revealed the genetic basis of macrolide resistance in G. parasuis. Our results show that most G. parasuis isolates remained susceptible to the macrolide drugs. For commonly used agents (e.g., tylosin and tilmicosin), elevated minimum inhibitory concentrations (MICs) were observed, whereas for the newer macrolides (e.g., tulathromycin and gamithromycin), the MICs remained almost unchanged. The macrolide resistance gene erm(T) and the A2059G mutation in 23S rRNA were detected in the current study. To the best of our knowledge, integrative and conjugative element (ICE)-borne erm(T) in G. parasuis is reported for the first time in this study. Taken together, these results provide insights into the susceptibility of G. parasuis to macrolides. The presence of erm(T) on ICEs may facilitate its transfer, reducing the effectiveness of macrolide treatment. Full article

The objective of this study was to examine the residue elimination patterns of seven antibiotics in the eggs of Taihang chickens under free-range conditions and develop suitable withdrawal times (WDTs). A total of 240 healthy Taihang chickens, aged 180 days, were randomly divided into eight groups of 30 birds each. The first seven groups were administered oxytetracycline, chlortetracycline, erythromycin, tylosin, tylvalosin, lincomycin, and tiamulin, respectively, in accordance with the maximum dosages and longest durations of treatment recommended by the Veterinary Pharmacopoeia of the People’s Republic of China. Group 8 served as the control group, and the test period continued until no drug residue could be detected. The results demonstrate that the residues of oxytetracycline, chlortetracycline, tylosin, tylvalosin, and tiamulin throughout the test period were below the maximum residue limits (MRLs) outlined in GB 31650-2019, “National food safety standard-Maximum residue limits for veterinary drugs in foods”. The egg yolk was identified as the target tissue for estimating the withdrawal time periods (WDTs) of these seven drugs. It was thus concluded that the recommended withdrawal time for tiamulin should be 0 days. However, the WDTs of oxytetracycline, chlortetracycline, tylosin, tylvalosin, were 2.8, 0.3, 2.4, and 7.4, respectively, when the upper limit of the 95% confidence interval was found to be lower than the MRLs. It was thus determined that the recommended WDTs for oxytetracycline, chlortetracycline, tylosin, and tylvalosin should be 3, 1, 3, and 8 days, respectively. In contrast, erythromycin and lincomycin exhibited concentrations below the permitted MRLs on days 7 and 8, respectively. However, the upper limits of the 95% confidence intervals for erythromycin and lincomycin were found to be below the MRLs when the WDTs were 11 and 8.9, respectively. This suggests that the recommended WDTs for these two antibiotics should be 11 days and 9 days. Full article