RESUMEN

Yersiniosis, caused by Yersinia ruckeri, has become the most common disease in farmed rainbow trout Oncorhynchus mykiss in Peru, affecting Puno and Junín Regions, important aquaculture areas in the country. Florfenicol (FLO) and oxytetracycline (OXY) are the antimicrobials most frequently used to mitigate losses attributed to this pathogen. This study presents an analysis of the susceptibility patterns of 60 Y. ruckeri isolates (30 isolates each from Puno and Junín), including the type strain CECT 4319T and the strains CECT 955 and CECT 956, against FLO and OXY. Minimum inhibitory concentrations (MICs) were determined following the guideline for standard broth dilution method published by the Clinical and Laboratory Standards Institute. MIC results ranged from 4.0 to 8.0 µg ml-1 for FLO and 0.5 to 4.0 µg ml-1 for OXY. Normalized resistance interpretation (NRI) analysis identified epidemiological cut-off values of ≤16.0 µg ml-1 for FLO and ≤4.0 µg ml-1 for OXY. All Peruvian isolates, including the collection strains, were categorized as wild-type for both antimicrobials. Even though the number of Y. ruckeri isolates with MIC values of 8 µg ml-1 for FLO is more than double in Puno than in Junín (15 vs. 7 isolates), the NRI analysis showed the same epidemiological cutoff of 16 µg ml-1; while for OXY, it was 4.0 µg ml-1 for Puno and 2.0 µg ml-1 for Junín. This study establishes the basis for monitoring susceptibility to FLO and OXY in new Y. ruckeri isolates in Peruvian rainbow trout farming.

Asunto(s)

Antibacterianos , Enfermedades de los Peces , Pruebas de Sensibilidad Microbiana , Oxitetraciclina , Tianfenicol , Yersinia ruckeri , Antibacterianos/farmacología , Tianfenicol/análogos & derivados , Tianfenicol/farmacología , Yersinia ruckeri/efectos de los fármacos , Perú/epidemiología , Oxitetraciclina/farmacología , Animales , Enfermedades de los Peces/microbiología , Farmacorresistencia Bacteriana , Yersiniosis/veterinaria , Yersiniosis/microbiología , Oncorhynchus mykiss

RESUMEN

Control measures are being introduced globally to reduce the prevalence of antibiotic resistance (ABR) in bacteria on farms. However, little is known about the current prevalence and molecular ecology of ABR in bacterial species with the potential to be key opportunistic human pathogens, such as Escherichia coli, on South American farms. Working with 30 dairy cattle farms and 40 pig farms across two provinces in central-eastern Argentina, we report a comprehensive genomic analysis of third-generation cephalosporin-resistant (3GC-R) E. coli, which were recovered from 34.8% (cattle) and 47.8% (pigs) of samples from fecally contaminated sites. Phylogenetic analysis revealed substantial diversity suggestive of long-term horizontal and vertical transmission of 3GC-R mechanisms. CTX-M-15 and CTX-M-2 were more often produced by isolates from dairy farms, while CTX-M-8 and CMY-2 and co-carriage of amoxicillin/clavulanate resistance and florfenicol resistance were more common in isolates from pig farms. This suggests different selective pressures for antibiotic use in these two animal types. We identified the ß-lactamase gene blaROB, which has previously only been reported in the family Pasteurellaceae, in 3GC-R E. coli. blaROB was found alongside a novel florfenicol resistance gene, ydhC, also mobilized from a pig pathogen as part of a new composite transposon. As the first comprehensive genomic survey of 3GC-R E. coli in Argentina, these data set a baseline from which to measure the effects of interventions aimed at reducing on-farm ABR and provide an opportunity to investigate the zoonotic transmission of resistant bacteria in this region. IMPORTANCE: Little is known about the ecology of critically important antibiotic resistance among bacteria with the potential to be opportunistic human pathogens (e.g., Escherichia coli) on South American farms. By studying 70 pig and dairy cattle farms in central-eastern Argentina, we identified that third-generation cephalosporin resistance (3GC-R) in E. coli was mediated by mechanisms seen more often in certain species and that 3GC-R pig E. coli were more likely to be co-resistant to florfenicol and amoxicillin/clavulanate. This suggests that on-farm antibiotic usage is key to selecting the types of E. coli present on these farms. 3GC-R E. coli and 3GC-R plasmids were diverse, suggestive of long-term circulation in this region. We identified the de novo mobilization of the resistance gene blaROB from pig pathogens into E. coli on a novel mobile genetic element, which shows the importance of surveying poorly studied regions for antibiotic resistance that might impact human health.

Asunto(s)

Infecciones por Escherichia coli , Escherichia coli , Tianfenicol/análogos & derivados , Animales , Humanos , Porcinos , Bovinos , Escherichia coli/metabolismo , Granjas , Cefalosporinas/farmacología , Infecciones por Escherichia coli/epidemiología , Infecciones por Escherichia coli/veterinaria , Infecciones por Escherichia coli/microbiología , Filogenia , Antibacterianos/farmacología , Antibacterianos/metabolismo , beta-Lactamasas/genética , beta-Lactamasas/metabolismo , Genómica , Amoxicilina , Ácido Clavulánico

RESUMEN

Natural products with antimicrobial activity and their association with synthetic antimicrobials are a sustainable option in fish farming. The objective of this study was to determine antimicrobial activity, antibiofilm potential and synergism of five essential oils (EOs) with florfenicol against motile Aeromonas isolated from Amazonian Colossoma macropomum. As their major constituent, the EOs of the species of Aloysia triphylla, Croton cajucara (red and white morphotype), Cymbopongo citratus and Lippia gracilis present ß-pinene (22.1%), germacrene D (11.5%), linalool (23%), geranial (45.7%) and carvacrol (42.2%), respectively. The EOs of L. gracilis and C. citratus showed the best antimicrobial activities against the Aeromonas strains (5 mg mL-1). All EOs interfered with biofilm formation and consolidated biofilm. The EOs of A. triphylla, C. citratus and L. gracilis showed a synergistic effect with florfenicol, reducing the amount of the chemical into the water systems while treatment.

Asunto(s)

Aeromonas , Antiinfecciosos , Aceites Volátiles , Tianfenicol , Animales , Aceites Volátiles/farmacología , Tianfenicol/análogos & derivados , Tianfenicol/farmacología

RESUMEN

The water-sediment partitioning of flumequine and florfenicol, two antibiotics used in salmon aquaculture is a critical driver of their fate and environmental impact. Batch experiments, were carried out using pure water or seawater, with or without sediment, and at summer and winter temperatures of Chilean fjords. Log Kd (partition between water and sediment) of florfenicol in seawater varied from 0.62 ± 0.69 to 0.67 ± 0.13, and Log KOC (partition between water and organic fraction of sediment) from 2.15± 0.29 to 2.19 ± 0.13. Difference between KOC and the octanol-water partition constant (KOW) showed that for florfenicol, adsorption onto the surface of particles was more significant than the absorption driven by hydrophobicity whilst hydrophobic absorption was a major driver of flumequine sorption. Flumequine Log Kd (0.92 ± 0.25 to 1.36 ± 0.10) and Log KOC (from 2.44 ± 0.25 to 2.89 ± 0.10) demonstrated its greater affinity than florfenicol to particles and potential accumulation into marine sediments.

Asunto(s)

Salmón , Agua , Animales , Antibacterianos , Acuicultura , Chile , Fluoroquinolonas , Sedimentos Geológicos/química , Tianfenicol/análogos & derivados , Agua/química

RESUMEN

Chilean aquaculture mainly produces salmonids and molluscs. Salmonid production has been questioned by its excessive use of antimicrobials. This study aimed to investigate the bacterial microbiota composition of Mytilus spp. cultivated near salmonid farms and to determine the minimum inhibitory concentration (MIC) to florfenicol and oxytetracycline of its culturable bacteria. Seven Mytilus farming sites classified according to their proximity to salmon farms as close (CSF) or distant (DSF) were sampled in two years. We analyzed Mytilus microbiota composition through culture-independent methods, and isolated culturable bacteria, and identified those isolates with MIC values ≥ 64 µg mL-1 to florfenicol or oxytetracycline. Results revealed that the alpha diversity was affected by sampling year but not by Mytilus farming site location or its interaction. Nevertheless, in 2018, we observed a significant negative correlation between the alpha diversity of Mytilus microbiota in each farm sites and the tonnes of florfenicol reported for each phytosanitary management area. We detected significant differences in beta diversity and relative abundance of specific bacterial taxa in Mytilus microbiota depending on the proximity to salmon farms and years. A higher proportion of isolates with MIC values ≥ 64 µg mL-1 to both antibiotics was detected in 2019 compared to 2018, but not significant differences were detected according to Mytilus farming site location. However, in 2019, isolates from CSF sites showed higher MIC values for both antibiotics than those from DSF. Bacterial genera corresponding to isolates with MIC values ≥ 64 µg mL-1 represented a low proportion of Mytilus microbiota identified with the culture-independent approach, reflecting the need to implement new methodologies in the study of antimicrobial resistance. These results suggest that the proximity to salmonid farms and sampling year influence the Mytilus microbiota and MIC values of their bacterial isolates; however, other environmental variables should be considered in further studies.

Asunto(s)

Microbiota , Mytilus , Oxitetraciclina , Animales , Antibacterianos/farmacología , Acuicultura , Pruebas de Sensibilidad Microbiana , Salmón , Tianfenicol/análogos & derivados

RESUMEN

AIMS: Aeromonas hydrophila is an opportunistic bacterium, with a high capacity for biofilm production, which can cause severe damage in aquaculture. The objective of this study was to identify the chemical compounds of the essential oils of Lippia sidoides (EOLS) and Cymbopogon citratus (EOCC), and to evaluate the biocidal, antibiofilm and synergistic action with the antimicrobial florfenicol of these essential oils (EOs) against A. hydrophila. METHODS AND RESULTS: The antibacterial activity of EOLS and EOCC was verified by the minimum bactericidal concentration and by the action of these EOs against both forming and consolidated biofilms. The synergistic activity of EOs with florfenicol was performed using the checkerboard technique. The main component of EOLS and EOCC was carvacrol (44.50%) and α-citral (73.56%), respectively. Both EOs showed weak inhibitory activity (≥3125.00 µg ml-1 ). Two bacterial isolates were able to produce biofilm, and EOLS and EOCC acted upon the bacterial isolates to prevent biofilm formation. A bactericidal effect was verified for EOLS in the previously consolidated biofilm for both isolates and for EOCC in only one of the isolates. In general, EOLS had a synergistic effect with florfenicol, while EOCF had an additive effect. CONCLUSIONS: Both EOs were able to interfere with biofilm formation and did not have an antagonistic effect in combination with florfenicol. The best results were found for EOLS, which showed a synergistic effect with florfenicol and the ability to interfere in the formation of consolidated biofilm. SIGNIFICANCE AND IMPACT OF THE STUDY: This study highlights the potential of EOLS and EOCC to interfere in biofilm and act in synergy with florfenicol to reduce the occurrence of A. hydrophila. Development of these compounds may contribute to the development of herbal medicines in aquaculture.

Asunto(s)

Cymbopogon , Lippia , Aceites Volátiles , Aeromonas hydrophila , Antibacterianos/química , Antibacterianos/farmacología , Biopelículas , Lippia/química , Pruebas de Sensibilidad Microbiana , Aceites Volátiles/química , Aceites Volátiles/farmacología , Tianfenicol/análogos & derivados

RESUMEN

Chile is a major global producer of farmed salmon in the fjords of Patagonia, and therefore a major consumer of antibiotics. We tested whether the antibiotics florfenicol and flumequine persisted in the large Puyuhuapi Fjord after the six months following mandatory concerted treatment by all salmon farms present in the fjord. Antibiotics were detected in 26% of analyzed samples, but only within the particulate phase, with concentrations of florfenicol of up to 23.1 ng L-1, where detected. Flumequine was present in one sample at trace concentration, and neither antibiotic was detected in the dissolved phase nor in surface sediments. A fugacity-based model predicted that flumequine should theoretically remain in surface sediments at the sub-Minimal Inhibiting Concentrations (sub-MIC) previously shown to promote selection for antibiotic resistance in bacteria. Our observations suggest that surface sediments might act as a reservoir for antibiotic resistomes of bacteria, and that bacteria bearing antibiotic resistance genes could eventually become a risk for human health through the consumption of marine products.

Asunto(s)

Antibacterianos , Estuarios , Animales , Chile , Fluoroquinolonas , Sedimentos Geológicos , Humanos , Tianfenicol/análogos & derivados , Agua

Asunto(s)

Antibacterianos/uso terapéutico , Enfermedades de los Peces/microbiología , Infecciones por Flavobacteriaceae/tratamiento farmacológico , Salmonidae , Tenacibaculum/efectos de los fármacos , Animales , Antibacterianos/farmacología , Chile , Enfermedades de los Peces/tratamiento farmacológico , Explotaciones Pesqueras , Oxitetraciclina/farmacología , Oxitetraciclina/uso terapéutico , Tianfenicol/análogos & derivados , Tianfenicol/farmacología , Tianfenicol/uso terapéutico

RESUMEN

O objetivo deste trabalho foi avaliar a eficácia do florfenicol na dose usualmente empregada em equinos de 22 mg/kg pelas vias intravenosa, intramuscular e oral para o tratamento de adenite equina por Streptococcus equi. subsp. equi, usando a modelagem farmacocinética/farmacodinâmica (PK/PD – Pharmacokinetic/Pharmacodynamic) e a simulação de Monte Carlo. Foi realizada uma simulação de Monte Carlo a partir dos parâmetros PK, logo depois, efetuou-se a modelagem PK/PD para determinar as taxas de eficácia do antimicrobiano para o tratamento dessa infecção bacteriana, de acordo com o valor da concentração inibitória mínima (CIM), em um intervalo de CIM de 0,125 – 4 μg/mL. Pela via intravenosa, a probabilidade de erradicação bacteriana foi de 100% para CIM até 0,5 μg/mL e efeito bacteriostático com probabilidades de 99% e 80% para CIMs de 2 e 4 μg/mL, respectivamente. Já pelas vias intramuscular e oral a probabilidade de se atingir o índice de erradicação bacteriológica foi de 100% para CIM de até 0,5 μg/mL, contudo, atinge valores de 80% e 81%, respectivamente, para CIM de 1 μg/mL considerando o efeito bactericida (p<0,01). Portanto, através desse estudo é evidenciado a eficácia do florfenicol até a CIM de 0,5 μg/mL para as três vias de administração citadas, entretanto, para CIMs superiores a esse valor, é imprescindível o ajuste da dose farmacológica, evitando falhas na terapêutica e possível resistência microbiana.

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The objective of this study was to evaluate the efficacy of florfenicol at the dose usually used in horses of 22 mg/kg by intravenous, intramuscular and oral routes for the treatment of equine adenitis caused by Streptococcus equi. subsp. equi, using Pharmacokinetic/Pharmacodynamic (PK/PD) modeling and Monte Carlo simulation. A Monte Carlo simulation was performed from the PK parameters, then PK/PD modeling was performed to determine the antimicrobial efficacy rates for the treatment of this bacterial infection, according to the minimum inhibitory concentration (MIC) value, in a MIC range of 0.125 - 4 μg/mL. Intravenously, the probability of bacterial eradication was 100% for MICs up to 0.5 μg/mL, and the bacteriostatic effect was 99% and 80% for MICs of 2 and 4 μg/mL, respectively. However, for the intramuscular and oral routes, the probability of reaching the bacteriologic eradication index was 100% for MICs of up to 0.5 μg/mL, however, it reaches values of 80% and 81%, respectively, for MICs of 1 μg/mL considering the bactericidal effect (p<0.01). Therefore, through this study the efficacy of florfenicol is evidenced up to the MIC of 0.5 μg/mL for the three routes of administration cited, however, for MICs higher than this value, it is essential to adjust the pharmacological dose, avoiding failures in therapy and possible microbial resistance.

Asunto(s)

Animales , Caballos/fisiología , Caballos/lesiones , Farmacocinética , Linfadenitis/terapia , Linfadenitis/veterinaria , Tianfenicol/análogos & derivados , Tianfenicol/farmacocinética , Tianfenicol/farmacología , Streptococcus equi

RESUMEN

The demand for healthier foods with high nutritional value has resulted in intensive fish farming. In this production system, high-frequency infections occur, and antibiotics are administrated for control. Only two antibiotics are allowed for use in Brazilian aquaculture, one of which is florfenicol. In this work, a bioconcentration assay was performed to assess the accumulation of florfenicol in the muscle of Nile tilapia (Oreochromis niloticus). Tilapia was evaluated as it is the most produced fish species in Brazil. The fish were exposed to florfenicol at a nominal concentration of 10 mg/L, through the water. Muscle and water were collected at 0, 1.5, 3, 6, 24, and 48 h during the exposure phase and at 1.5, 3, 6, 24, 48, and 120 h during the depuration phase. Quantification was performed using an LC-MS/MS. The results showed rapid absorption and elimination of the antibiotic (half-life, t1/2 = 5 h), with low potential for accumulation of florfenicol in tilapia muscles. The study was performed to determine the bioconcentration factor (BCF) and withdrawal period of florfenicol, being 0.05 mL/µg and 1.8 h, respectively. The results contribute to set protocols for the safe use of florfenicol in tilapia transport, avoiding residues in fish that may pose risks to human health.

Asunto(s)

Cíclidos , Tilapia , Animales , Antibacterianos , Bioacumulación , Brasil , Cromatografía Liquida , Humanos , Espectrometría de Masas en Tándem , Tianfenicol/análogos & derivados , Agua

RESUMEN

Drug controlled release technologies (DCRTs) represent an opportunity for designing new therapies. Main objectives are dose number optimization and secondary effects reduction to improve the level of patient/client acceptance. The present work studies DCRTs based in blended polymeric implants for single dose and long-term therapies of florfenicol (FF), a broad spectrum antibiotic. Polymers used were PLGA and Eudragit E100/S100 types. Eudragit/PLGA and FF/PLGA ratios were the main studied factors in terms of encapsulation efficiencies (EEs) and drug release profiles. In addition, morphological and physicochemical characterization were carried out. EEs were of 50-100% depending on formulation composition, and the FF releasing rate was increased or diminished when E100 or S100 were added, respectively. PLGA hydrolytic cleavage products possibly affect Eudragit solubility and matrix stability. Different mathematical models were used for better understanding and simulating release processes. Implants maintained the antimicrobial activity against Pseudomonas aeruginosa up to 12 days on agar plates. The developed DCRTs represents a suitable alternative for florfenicol long-term therapies.

Asunto(s)

Ácidos Polimetacrílicos , Tianfenicol , Preparaciones de Acción Retardada , Humanos , Solubilidad , Tianfenicol/análogos & derivados

RESUMEN

O objetivo deste trabalho foi avaliar a eficácia do florfenicol na dose usualmente empregada em equinos de 22 mg/kg pelas vias intravenosa, intramuscular e oral para o tratamento de adenite equina por Streptococcus equi. subsp. equi, usando a modelagem farmacocinética/farmacodinâmica (PK/PD Pharmacokinetic/Pharmacodynamic) e a simulação de Monte Carlo. Foi realizada uma simulação de Monte Carlo a partir dos parâmetros PK, logo depois, efetuou-se a modelagem PK/PD para determinar as taxas de eficácia do antimicrobiano para o tratamento dessa infecção bacteriana, de acordo com o valor da concentração inibitória mínima (CIM), em um intervalo de CIM de 0,125 4 μg/mL. Pela via intravenosa, a probabilidade de erradicação bacteriana foi de 100% para CIM até 0,5 μg/mL e efeito bacteriostático com probabilidades de 99% e 80% para CIMs de 2 e 4 μg/mL, respectivamente. Já pelas vias intramuscular e oral a probabilidade de se atingir o índice de erradicação bacteriológica foi de 100% para CIM de até 0,5 μg/mL, contudo, atinge valores de 80% e 81%, respectivamente, para CIM de 1 μg/mL considerando o efeito bactericida (p<0,01). Portanto, através desse estudo é evidenciado a eficácia do florfenicol até a CIM de 0,5 μg/mL para as três vias de administração citadas, entretanto, para CIMs superiores a esse valor, é imprescindível o ajuste da dose farmacológica, evitando falhas na terapêutica e possível resistência microbiana.(AU)

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The objective of this study was to evaluate the efficacy of florfenicol at the dose usually used in horses of 22 mg/kg by intravenous, intramuscular and oral routes for the treatment of equine adenitis caused by Streptococcus equi. subsp. equi, using Pharmacokinetic/Pharmacodynamic (PK/PD) modeling and Monte Carlo simulation. A Monte Carlo simulation was performed from the PK parameters, then PK/PD modeling was performed to determine the antimicrobial efficacy rates for the treatment of this bacterial infection, according to the minimum inhibitory concentration (MIC) value, in a MIC range of 0.125 - 4 μg/mL. Intravenously, the probability of bacterial eradication was 100% for MICs up to 0.5 μg/mL, and the bacteriostatic effect was 99% and 80% for MICs of 2 and 4 μg/mL, respectively. However, for the intramuscular and oral routes, the probability of reaching the bacteriologic eradication index was 100% for MICs of up to 0.5 μg/mL, however, it reaches values of 80% and 81%, respectively, for MICs of 1 μg/mL considering the bactericidal effect (p<0.01). Therefore, through this study the efficacy of florfenicol is evidenced up to the MIC of 0.5 μg/mL for the three routes of administration cited, however, for MICs higher than this value, it is essential to adjust the pharmacological dose, avoiding failures in therapy and possible microbial resistance.(AU)

Asunto(s)

Animales , Caballos/fisiología , Farmacocinética , Tianfenicol/análogos & derivados , Tianfenicol/farmacología , Tianfenicol/farmacocinética , Linfadenitis/terapia , Linfadenitis/veterinaria , Caballos/lesiones , Streptococcus equi

RESUMEN

The aim of this study was to determine the median lethal concentration (LC50-96h), effective concentration (EC50-96h), risk assessment, and development of Nile tilapia Oreochromis niloticus larvae submitted to florfenicol (FF) exposure. Fish (n = 147; 8.6 ± 0.6 mg; 7 fish/aquarium) were randomly distributed in 21 aquaria (1 L) and exposed to five concentrations of FF 58.73; 131.31; 198.96; 241.88 and 381.81 mg L-1 plus one control and a control with solvent, totalizing seven treatments and three replicates. The estimated median LC50-96h of FF for Nile tilapia larvae was 349.94 mg L-1. The EC50-96h of FF was 500 mg L-1 for weight reduction and was 1040 mg L-1 for length reduction. After the exposure period, final weight and length differed (p < 0.05) among treatments, showing the lowest biometric values ​​with the highest concentrations of FF. The pH and dissolved oxygen were altered (p < 0.05) during the experimental period. The FF high doses used to determine the LC 50 after 96 h negatively affected the development of the larvae. On the other hand, through risk assessment analysis this antibiotic can be classified as low toxicity to Nile tilapia larvae and show low environmental risk.

Asunto(s)

Cíclidos/crecimiento & desarrollo , Larva/efectos de los fármacos , Tianfenicol/análogos & derivados , Contaminantes Químicos del Agua/toxicidad , Animales , Relación Dosis-Respuesta a Droga , Desarrollo Embrionario/efectos de los fármacos , Larva/crecimiento & desarrollo , Dosificación Letal Mediana , Distribución Aleatoria , Medición de Riesgo , Tianfenicol/toxicidad , Pruebas de Toxicidad Aguda

RESUMEN

This study aimed to evaluate the effect of the commercial probiotic (Saccharomyces cerevisiae), antibiotic (florfenicol), and its combination for Nile tilapia culture. The experiment was arranged in a completely randomized design with five replications, and five treatments diets: Control: water and diet without additives; YD: yeast in the diet (1 g Kg-1); AW: antibiotic in the water (0.002 g L-1); AWYD: antibiotic in the water, and yeast in the diet (0.002 g L-1 and 1 g Kg-1); and AD: antibiotic in the diet (0.01 g kg-1). The growth parameters as total and standard length, weight, weight gain, biomass, Fulton's condition factor, specific growth rate and plasma cortisol of tilapia did not show the difference between the treatments. The survival rates and food conversion rate of fish were greater in treatment with florfenicol included in the diet. The commercial probiotic did not improve growth or survival. The administration of the antibiotic florfenicol in the water needs more studies. The inclusion of the antibiotic in the diet promotes growth and survival in Nile tilapia juvenile.

Asunto(s)

Alimentación Animal , Antibacterianos/administración & dosificación , Cíclidos/crecimiento & desarrollo , Probióticos/administración & dosificación , Saccharomyces cerevisiae/química , Tianfenicol/análogos & derivados , Animales , Acuicultura , Tianfenicol/administración & dosificación

RESUMEN

The aetiological agent of Piscirickettsiosis is Piscirickettsia salmonis, a Gram-negative intracellular pathogen, and high doses of antibiotics have regularly been employed to treat this infection. Seven florfenicol and/or oxytetracycline resistance genes (tet pump, tetE, Tclor/flor, Tbcr, TfloR, ompF and mdtN) were identified in strains by in silico genome analyses. Later, the number of single nucleotide polymorphisms (SNPs) and its relationship with the resistance to these antibiotics were identified and analysed, using the original LF-89 strain as reference. Trials to determine and compare the minimum inhibitory concentration (MIC) of oxytetracycline and florfenicol in each strain, as well as to quantify the gPCR transcripts levels in the selected genes, were performed. Therefore, variations in the resistance to both antibiotics were observed, where the strain with fewer SNPs showed the highest susceptibility. Consistently, the in silico 3D analyses of proteins encoded by the selected genes revealed structural changes, evident in the sequences with the highest number of SNPs. These results showed that the bacterial resistance to oxytetracycline was mainly linked to the presence of SNPs in relevant sites, antibiotic resistance genes and an OmpF porin, leading to important changes in the protein structure.

Asunto(s)

Farmacorresistencia Microbiana/genética , Genes Bacterianos , Piscirickettsia/genética , Polimorfismo de Nucleótido Simple , Animales , Enfermedades de los Peces/microbiología , Pruebas de Sensibilidad Microbiana , Oxitetraciclina , Piscirickettsia/efectos de los fármacos , Infecciones por Piscirickettsiaceae/microbiología , Infecciones por Piscirickettsiaceae/veterinaria , Tianfenicol/análogos & derivados

RESUMEN

Florfenicol (FLO) is a broad-spectrum fluorinated antibiotic used for the treatment of bacterial diseases such as bovine respiratory disease (BRD) in cattle. FLO is a poorly soluble drug in aqueous solution, and its encapsulation in various nanovehicles has been reported to be less than 30%. In this context, the use of bovine serum albumin (BSA) as a nanocarrier for FLO is an interesting approach. BSA is a biocompatible, biodegradable, nontoxic, and nonimmunogenic natural protein, allowing the vehiculization of hydrophilic and hydrophobic drugs with a well-tolerated administration. The present work focuses on the fabrication and characterization of florfenicol-loaded BSA (FLO-BSA NPs), incorporation efficiency, and in vitro release pattern. FLO-BSA NPs nanoparticles were successfully obtained by a simple, low-cost and in a few steps method. The physicochemical properties of the obtained nanoparticles such as size (~ 120 nm), polydispersity index (0.04), and zeta potential (approximately - 40 mV) suggest a high colloidal stability and suitable characteristics for drug delivery. The drug loading reveals a high incorporation of florfenicol in the nanoparticles, in which 33.6 molecules of FLO are encapsulated per each molecule of BSA. The in vitro release profile exhibits an initial stage characterized by the burst effect and then a prolonged release of FLO from the albumin matrix, which is compatible with the Higuchi model and which follows a Fickian diffusion. The results together suggest a suitable tool for future investigations in drug delivery field in order to use this nanomaterial in food, pharmaceutical, and veterinary industry.

Asunto(s)

Antibacterianos/farmacocinética , Sistemas de Liberación de Medicamentos/métodos , Nanopartículas/metabolismo , Albúmina Sérica Bovina/farmacocinética , Tianfenicol/análogos & derivados , Animales , Antibacterianos/administración & dosificación , Antibacterianos/síntesis química , Bovinos , Preparaciones de Acción Retardada/administración & dosificación , Preparaciones de Acción Retardada/síntesis química , Preparaciones de Acción Retardada/farmacocinética , Portadores de Fármacos/administración & dosificación , Portadores de Fármacos/síntesis química , Portadores de Fármacos/farmacocinética , Sistemas de Liberación de Medicamentos/tendencias , Interacciones Hidrofóbicas e Hidrofílicas , Nanopartículas/administración & dosificación , Nanopartículas/química , Tamaño de la Partícula , Albúmina Sérica Bovina/administración & dosificación , Albúmina Sérica Bovina/síntesis química , Tianfenicol/administración & dosificación , Tianfenicol/síntesis química , Tianfenicol/farmacocinética

RESUMEN

Salmonid Rickettsial Septicemia (SRS) is the disease of greatest economic importance in the Chilean salmon farming industry, causing high mortality in fish during the final stage of their productive cycle at sea. Since current, commercially available vaccines have not demonstrated the expected efficacy levels, antimicrobials, most commonly florfenicol, are still the main resource for the treatment and control of this pathogen. The aim of this study was to determine the most appropriate single dose of florfenicol, administered through medicated feed, for the treatment of Piscirickettsia salmonis (P. salmonis), using pharmacokinetic/pharmacodynamic (PK/PD) models. Previously, Minimum Inhibitory Concentrations (MICs) of florfenicol were determined for 87 P. salmonis isolates in order to define the epidemiological cut-off point (COWT). The most commonly observed MIC was 0.125 µg mL-1 (83.7%). The COWT value was 0.25 µg mL-1 with a standard deviation of 0.47 log2 µg mL-1 and 0.36 log2 µg mL-1, for Normalized resistance interpretation (NRI) method and ECOFFinder method, respectively. A MIC of 1 µg mL-1 was considered the pharmacodynamic value (PD) to define PK/PD indices. Three doses of florfenicol were evaluated in fish farmed under controlled conditions. For each dose, 150 fish were used and blood plasma samples were collected at different time points (0-48 hours). PK parameters were obtained from curves representing plasma concentrations as a function of time. The results of Monte Carlo simulation indicate that at a dose of 20 mg/Kg l.w. of florfenicol, administered orally as medicated feed, there is 100% probability (PTA) of achieving the desired efficacy (AUC0-24h/MIC>125). According to these results, we suggest that at the indicated dose, the PK/PD cut-off point for florfenicol versus P. salmonis could be 2 µg mL-1 (PTA = 99%). In order to assess the indicated dose in Atlantic salmon, fish were inoculated with P. salmonis LF-89 strain and then treated with the optimized dose of florfenicol, 20 mg/Kg bw for 15 days.

Asunto(s)

Antibacterianos/uso terapéutico , Enfermedades de los Peces/tratamiento farmacológico , Infecciones por Piscirickettsiaceae/tratamiento farmacológico , Tianfenicol/análogos & derivados , Administración Oral , Animales , Antibacterianos/farmacocinética , Antibacterianos/farmacología , Área Bajo la Curva , Farmacorresistencia Bacteriana , Enfermedades de los Peces/microbiología , Explotaciones Pesqueras , Semivida , Pruebas de Sensibilidad Microbiana , Método de Montecarlo , Piscirickettsia/efectos de los fármacos , Piscirickettsia/aislamiento & purificación , Infecciones por Piscirickettsiaceae/microbiología , Curva ROC , Salmo salar , Tianfenicol/farmacocinética , Tianfenicol/farmacología , Tianfenicol/uso terapéutico

RESUMEN

The high use of antibiotics for the treatment of bacterial diseases is one of the main problems in the mass production of animal protein. Salmon farming in Chile is a clear example of the above statement, where more than 5,500 tonnes of antibiotics have been used over the last 10 years. This has caused a great impact both at the production level and on the environment; however, there are still few works in relation to it. In order to demonstrate the impact of the high use of antibiotics on fish gut microbiota, we have selected four salmon farms presenting a similar amount of fish of the Atlantic salmon species (Salmo salar), ranging from 4,500 to 6,000 tonnes. All of these farms used treatments with high doses of antibiotics. Thus, 15 healthy fish were selected and euthanised in order to isolate the bacteria resistant to the antibiotics oxytetracycline and florfenicol from the gut microbiota. In total, 47 bacterial isolates resistant to florfenicol and 44 resistant to oxytetracycline were isolated, among which isolates with Minimum Inhibitory Concentrations (MIC) exceeding 2048 µg/mL for florfenicol and 1024 µg/mL for oxytetracycline were found. In addition, another six different antibiotics were tested in order to demonstrate the multiresistance phenomenon. In this regard, six isolates of 91 showed elevated resistance values for the eight tested antibiotics, including florfenicol and oxytetracycline, were found. These bacteria were called "super-resistant" bacteria. This phenotypic resistance was verified at a genotypic level since most isolates showed antibiotic resistance genes (ARGs) to florfenicol and oxytetracycline. Specifically, 77% of antibiotic resistant bacteria showed at least one gene resistant to florfenicol and 89% showed at least one gene resistant to oxytetracycline. In the present study, it was demonstrated that the high use of the antibiotics florfenicol and oxytetracycline has, as a consequence, the selection of multiresistant bacteria in the gut microbiota of farmed fish of the Salmo salar species at the seawater stage. Also, the phenotypic resistance of these bacteria can be correlated with the presence of antibiotic resistance genes.

Asunto(s)

Antibacterianos/farmacología , Bacterias/efectos de los fármacos , Farmacorresistencia Bacteriana Múltiple/efectos de los fármacos , Intestinos/microbiología , Animales , Acuicultura , Bacterias/genética , Bacterias/aislamiento & purificación , Farmacorresistencia Bacteriana Múltiple/genética , Microbioma Gastrointestinal/efectos de los fármacos , Pruebas de Sensibilidad Microbiana , Oxitetraciclina/farmacología , ARN Ribosómico 16S/química , ARN Ribosómico 16S/genética , ARN Ribosómico 16S/metabolismo , Salmo salar , Tianfenicol/análogos & derivados , Tianfenicol/farmacología

RESUMEN

Antimicrobial residues might persist in products and by-products destined for human or animal consumption. Studies exploring the depletion behavior of florfenicol residues in broiler chicken claws are scarce, even though claws can enter the food chain directly or indirectly. Hence, this study intended to assess the concentrations of florfenicol (FF) and florfenicol amine (FFA)-its active metabolite-in chicken claws from birds that were treated with a therapeutic dose of florfenicol. Furthermore, concentrations of these analytes in this matrix were compared with their concentrations in edible tissues at each sampling point. A group of 70 broiler chickens were raised under controlled conditions and used to assess residue depletion. Sampling points were on days 5, 10, 20, 25, 30, 35, and 40 after ceasing treatment, thus extending beyond the withdrawal period established for muscle tissue (30 days). Analytes were extracted using HPLC-grade water and acetone, and dichloromethane was used for the clean-up stage. Liquid chromatography coupled to mass spectroscopy detection (LC⁻MS/MS) was used to detect and quantify the analytes. The analytical methodology developed in this study was validated in-house and based on the recommendations described in the Commission Decision 2002/657/EC from the European Union. Analyte concentrations were calculated by linear regression analysis of calibration curves that were fortified using an internal standard of chloramphenicol-d5 (CAF-d5). The depletion time of FF and FFA was set at 74 days in claws, based on a 95% confidence level and using the limit of detection (LOD) as the cut-off point. Our findings show that FF and FFA can be found in chicken claws at higher concentrations than in muscle and liver samples at each sampling point.

Asunto(s)

Pollos/anatomía & histología , Pollos/metabolismo , Especificidad de Órganos , Espectrometría de Masas en Tándem/métodos , Tianfenicol/análogos & derivados , Animales , Cromatografía Liquida , Carne , Estándares de Referencia , Reproducibilidad de los Resultados , Tianfenicol/análisis

RESUMEN

A quantitative method for analysis of amphenicols (chloramphenicol - CAP, thiamphenicol - TAP and florfenicol - FF) in Nile tilapia using LC-MS/MS is described. A simple sample preparation procedure was optimized using a Plackett-Burman design. The method was validated in accordance with Decision 2002/657/EC. Repeatability and reproducibility were less than 10.7% and 16%, respectively, for all compounds. Recoveries varied from 79.8% to 92.0%. CCα was 0.019, 54.81 and 54.93 µg.kg-1 for CAP, FF and TAP, respectively. CCß was 0.068, 64.88 and 58.91 µg.kg-1 for CAP, FF and TAP, respectively. Limits of quantification (LOQ) were 12.5 µg.kg-1 for FF and TAP and 0.15 µg.kg-1 for CAP. Nile tilapia fillets (n = 32) analyzed did not contain chloramphenicol. Thiamphenicol was detected in one sample (3.1%) and florfenicol was detected in every sample, all of them at concentrations below the maximum residue limit.

Asunto(s)

Cloranfenicol/análisis , Cromatografía Liquida/métodos , Cíclidos , Productos Pesqueros/análisis , Espectrometría de Masas en Tándem/métodos , Tianfenicol/análogos & derivados , Tianfenicol/análisis , Animales , Antibacterianos/análisis , Límite de Detección , Reproducibilidad de los Resultados