Oxytetracycline (OTC) is administered in the poultry industry for the treatment of digestive and respiratory diseases. The use of OTC may contribute to the selection of resistant bacteria in the gastrointestinal tract of birds or in the environment. To determine the effect of OTC on the selection of resistant Escherichia coli strains post-treatment, bacteria were isolated from droppings and litter sampled from untreated and treated birds. Bacterial susceptibility to tetracyclines was determined by the Kirby–Bauer test. A total of 187 resistant isolates were analyzed for the presence of tet(A), (B), (C), (D), (E), and (M) genes by PCR. Fifty-four strains were analyzed by PFGE for subtyping. The proportion of tetracycline-resistant E. coli strains isolated was 42.88%. The susceptibility of the strains was treatment-dependent. A high clonal diversity was observed, with the tet(A) gene being the most prevalent, followed by tet(C). Even at therapeutic doses, there is selection pressure on resistant E. coli strains. The most prevalent resistance genes were tet(A) and tet(C), which could suggest that one of the main mechanisms of resistance of E. coli to tetracyclines is through active efflux pumps.

Objective: We set out to evaluate the persistence of sulfachloropyridazine, oxytetracycline, and enrofloxacin in broiler chicken litter following therapeutic oral treatment and its association with the isolation of Escherichia coli resistant to these antimicrobials. Methods: Forty broiler chickens were raised under controlled conditions and divided into three experimental groups, each treated with a different antimicrobial, in addition to an untreated/control group. Litter samples were collected post treatment, analyzed by UPLC-MS/MS, and processed for the isolation of E. coli. The antimicrobial susceptibility of E. coli was assessed using the Kirby–Bauer disk diffusion method. Results: Chemical analysis detected concentrations of antimicrobials throughout post treatment, reaching maxima of 42,910.14 μg kg⁻¹, 92,712 μg kg⁻¹, and 9567 μg kg⁻¹ for sulfachloropyridazine, oxytetracycline plus 4-epi-oxytetracycline, and enrofloxacin plus ciprofloxacin, respectively. It was estimated that the concentrations of sulfachloropyridazine, oxytetracycline, and enrofloxacin would persist in broiler litter for 61, 244, and 514 days, respectively. A very strong association was observed between the presence of antimicrobial residues and the antimicrobial resistance of E. coli (p-value < 0.0001, and Cramer’s coefficient of 0.47), and an independence between the level of residue concentration and susceptibility (p-value 0.5262). Conclusions: The persistence of antimicrobial residues contributes to the selection of resistant bacteria, regardless of persistent antimicrobial concentrations. These findings highlight the need for stricter regulations on poultry litter management, including residue thresholds and resistance monitoring, to minimize environmental and public health risks. Proper treatment of poultry litter is essential to ensure its sustainable and safe re-use in agricultural systems.

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.

The objective of this study was to evaluate the persistence and environmental dissemination of enrofloxacin (EFX) and its metabolite ciprofloxacin (CFX) residues in poultry systems, as well as their effect on antimicrobial resistance in Escherichia coli. The experimental design included three groups: one treated group (A) and two untreated groups (B.1 and B.2), located in pens adjacent to or within 30 cm of group A to assess residue transfer. Birds in group A received EFX orally (10 mg·kg⁻¹ every 24 h for 5 days) via orogastric tube. EFX and CFX residues persisted in litter and excreta for up to 18 days post-treatment, reaching initial concentrations of 20,968 µg·kg⁻¹ in litter and 884.8 µg·kg⁻¹ in droppings in group A. Significant differences were detected between groups (Kruskal–Wallis, p < 0.05), confirming greater accumulation in the treated group and environmental dissemination. E. coli isolates obtained from litter and droppings from group A showed 73% resistance after treatment and correlated positively with residue concentration (ρ = 0.53). While the untreated groups B.1 and B.2 showed resistance rates of 24% and 13%, respectively, the control group exhibited a resistance rate of 3.3%. This study shows the detection of low levels of EXF and CFX residues in the litter of untreated groups, indicating limited dispersion. These findings highlight the importance of proper byproduct management and targeted environmental monitoring within the One Health framework, as continuous environmental exposure over time, combined with the persistence of this compound, may contribute to the selection of resistant bacteria.

Introduction: Lennox-Gastaut syndrome is a form of childhood epilepsy that has a dramatic negative impact on the physical and developmental health of the patient. Being an age-related disorder, it is characterized by seizures, characteristic electroencephalogram, psychomotor retardation and behavioral disturbances. It is more common in males and usually begins before the age of eight years and peaks between the ages of three and five years. Case presentation: This was a 5-year-old patient who was born prematurely product of which presented sequelae of hypoxia, who around 4 months was diagnosed with epilepsy, for which he received double antiepileptic therapy based on levetiracetam and valproic acid with partial control of his seizures until before the age of 5 years, At this time it was necessary to include a third drug to the usual therapy called clobazam, for which with the adjustment of doses until the age of 8 years he achieved a better control, however the sequelae of infantile cerebral palsy are marked.Conclusion: It is one of the most difficult syndromes to treat and is often resistant to commonly used antiepileptic drugs. The long-term prognosis is poor; although epilepsy usually improves, complete absence of seizures is rare and, instead, psychological and psychiatric disorders worsen over time