Pseudomonas aeruginosa en la otitis externa canina: situación actual

Otitis externa is a frequent disease in veterinary small animal practice. Understanding its pathophysiology is important for prevention, diagnosis, and treatment. The diagnostic protocol must be strict, where bacterial culture and antibiogram play an essential role. Pseudomonas aeruginosa is an opportunistic and invasive microorganism, which by itself constitutes a perpetuating factor for chronic otitis. In addition to its virulence factors and intrinsic resistance to multiple drugs, it forms protective biofilms on colonized tissues, and has a great capacity to acquire genes that determine chromosomal and extra chromosomal resistance during the antibiotic treatment. Management of chronic or recurrent cases of otitis by P. aeruginosa is a constant challenge for veterinarians. Since the outer ear is a scarcely irrigated tissue, the use of systemic antimicrobials does not reach adequate local concentrations, leaving topical therapy as the first choice of treatment. Treatment success should consider application of pharmacokinetic/pharmacodynamic guidelines not only from a purely empirical conception, but also from a quantitative conception, which allows description and simulation of the effect of an antibiotic on a bacterial population as function of time through mathematical modelling of the experimental data, in order to maximize the effectiveness and minimize resistance selection.La otitis externa es una enfermedad de presentación frecuente en la práctica diaria. La comprensión de su fisiopatología es importante para su prevención, diagnóstico y tratamiento. El protocolo diagnóstico debe ser estricto, siendo fundamental el rol que cumplen en estos casos el cultivo bacteriano y el antibiograma. Pseudomonas aeruginosaes un microorganismo oportunista e invasor, que constituye en sí mismo un factor perpetuante para las otitis crónicas. Además de sus factores de virulencia y la resistencia intrínseca a múltiples fármacos, forma biopelículas de protección sobre tejidos colonizados y posee gran capacidad para adquirir genes determinantes de resistencia cromosómica y extra cromosómica durante el tratamiento. Los casos crónicos o recurrentes con aislamientos de P. aeruginosa resultan un desafío constante para el veterinario. El oído externo tiene escasa irrigación, por lo cual los antimicrobianos sistémicos no alcanzan concentraciones adecuadas, siendo la terapia tópica la primera elección. El éxito terapéutico evoluciona hacia la aplicación de pautas farmacocinéticas/farmacodinámicas, desde una concepción netamente empírica hasta una concepción cuantitativa, permitiendo describir y simular el efecto de un antibiótico sobre una población bacteriana en función del tiempo, mediante la modelización matemática de los datos experimentales, con objeto de maximizar la eficacia y minimizar fenómenos de resistencia

Enrofloxacin and ciprofloxacin residues in broiler chicken feathers after enrofloxacin oral administration

Antibiotics in animal feed are a public health concern. Drug residues could eventually be detected in animal food products intended for human consumption. Our aim was to study the residue depletion of enrofloxacin and its metabolite ciprofloxacin in broiler chicken feathers. A validated HPLC-fluorescence method was used to quantify both compounds in feather samples. Broiler chickens were treated through drinking water with 10 mg Kg-1 d of enrofloxacin for 5 consecutive days. Feather samples were taken from 10 random birds per day until 9 days. Extraction was performed by a liquid/liquid technique. Both fluoroquinolones concentrations were determined by liquid chromatography with fluorescence detection. High levels of enrofloxacin and ciprofloxacin were found in feathers after oral administration and these compounds were detected for 9 days. Feather meal is a potential source of drug residues that can pass through the food chain when contaminated meal is fed to food-producing animals. In the present study enrofloxacin and ciprofloxacin concentrations were 0.20 to 5.46 µg g-1 between 1 to 9 days after final treatment, which means that withdrawal time fit for edible tissues is not adequate to reduce antimicrobial residues in chicken feathers. Further studies to establish a withdrawal time may be useful to avoid that drug residues could result in adverse health consequences like increase in antibiotic resistance.Fil: Marchetti, Maria Laura. Universidad Nacional de la Plata. Facultad de Cs.veterinarias. Laboratorio de Estudios Farmacológicos y Toxicológicos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Buchamer, Andrea Veronica. Universidad Nacional de la Plata. Facultad de Cs.veterinarias. Laboratorio de Estudios Farmacológicos y Toxicológicos; ArgentinaFil: Buldain, Daniel Cornelio. Universidad Nacional de la Plata. Facultad de Cs.veterinarias. Laboratorio de Estudios Farmacológicos y Toxicológicos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Mestorino, Olga Nora. Universidad Nacional de la Plata. Facultad de Cs.veterinarias. Laboratorio de Estudios Farmacológicos y Toxicológicos; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentin

Tissue depletion profile of ivermectin in rabbits

Avermectins are largely used in different animal species. Ivermectin, the most popular avermectin, is used against a wide spectrum of endo and ectoparasites. Some mange mites are particularly sensitive to ivermectin. Notoedres cati var. cuniculi, the agent of rabbit mange, is particularly sensitive to ivermectin. Pharmacokinetic and residual studies of ivermectin in rabbits, however, are scarce. The objective of the present paper was to study the tissue residue profile of ivermectin (IVM) after subcutaneous (s.c.) administration of a 1% w/w solution. Sixteen young healthy male rabbits received 200 μg/kg of a 1% w/w ivermectin formulation subcutaneously. Groups of four treated animals were sacrificed at 10, 20, 30 and 40 days after injection. Samples of liver, fat, kidney and muscle tissue were obtained. IVM concentrations were determined by liquid chromatography with fluorescence detection after automatic solid phase extraction with SPE C18 cartridges. Ivermectin was detected after subcutaneous administration until 40 days. Muscle samples showed the lowest IVM concentrations throughout the study. The highest IVM concentrations at all sampling times were measured in liver and fat tissues. Nevertheless, IVM concentrations in all the tissues analyzed were below the accepted maximum residue limits recommended by the European Union at 20 days posttreatment.Fil: Marchetti, Maria Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de la Plata. Facultad de Cs.veterinarias. Laboratorio de Estudios Farmacologicos y Toxicologicos.; ArgentinaFil: Buldain, Daniel Cornelio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de la Plata. Facultad de Cs.veterinarias. Laboratorio de Estudios Farmacologicos y Toxicologicos.; ArgentinaFil: Buchamer, Andrea Veronica. Universidad Nacional de la Plata. Facultad de Cs.veterinarias. Laboratorio de Estudios Farmacologicos y Toxicologicos.; ArgentinaFil: Zeinsteger, Pedro Adolfo. Universidad Nacional de la Plata. Facultad de Cs.veterinarias. Laboratorio de Estudios Farmacologicos y Toxicologicos.; ArgentinaFil: Mestorino, Olga Nora. Universidad Nacional de la Plata. Facultad de Cs.veterinarias. Laboratorio de Estudios Farmacologicos y Toxicologicos.; Argentin

Tissue depletion of doxycycline after its oral administration in food producing chicken for fattening

Doxycycline (DOX), tetracycline of second generation, is mainly active against Gram–positive and Gram–negative bacteria, aerobic and anaerobic. Although there are few pharmacokinetic studies in chickens, it is frequently used for the colibacillosis treatment, salmonellosis, staphylococcal infections, avian mycoplasmosis and chlamydia. The objective of this study was to evaluate the withdrawal time (WT) of DOX formulation at 25 % in edible tissues, after its oral (PO) use in broilers. Forty healthy chicks (30–35 days of age) were used. DOX was administered with drinking water for 5 days at 10 mg kg–1 (N = 36); four untreated animals were reserved (control). Six animals per group were euthanized by cervical dislocation after desensitization by passage of an electric current through the head, after 24 hours until 9 d post treatment and control animals also. Muscle, liver, kidney and skin/fat samples were obtained. DOX was determined by HPLC with UV detection. DOX concentrations were determined in all tissues examined; generally falling below the MRL at 7 d after administration is terminated. It was estimated 6.58, 8.18, 8.69 and 6.96 d of WT for muscle, liver, kidney and skin/fat, respectively. After DOX administration at a rate of 10 mg kg–1 for 5 days in drinking water, a WT of 9 d is suggested in poultry destined for human consumption.Facultad de Ciencias VeterinariasConsejo Nacional de Investigaciones Científicas y Técnica

In vitro synergistic interaction between Melaleuca armillaris essential oil and erythromycin against Staphylococcus aureus isolated from dairy cows

Staphylococcus aureus frequently causes subclinical mastitis around the world with a high impact on the milk industry and public health. Essential oils (EO) are recognized antimicrobials that can be synergistic with antibiotics. The main objective of this study was to evaluate the essential oil (EO) of Melaleuca armillaris as an adjuvant of erythromycin (ERY) for the alternative treatment of bovine mastitis caused by S. aureus. The Minimum Inhibitory and Bactericidal Concentrations (MIC and MBC) of EO, ERY, and its combinations were established against S. aureus at different pHs (7.4, 6.5 and 5.0), emulating extra and intracellular conditions. Sensitive (N = 3) and resistant (N = 3) strains to ERY and S. aureus ATCC 29213 as control were used. Math models were applied to describe the antibacterial activity of EO and combinations EO-ERY. The EO was bactericidal against all the strains independently of the pH with a slight improvement in acid conditions. The synergism between EO and ERY was estimated by the Fractional Inhibitory Concentration Index (FIC) and by mathematical modeling of the bacterial killing data. Synergism was observed with ERY, where combinations had bactericidal activity also even with pH modification. M. armillaris EO is an interesting adjuvant for ERY, being a promissory option for further analysis of intracellular efficacy against S. aureus.Fil: Buldain, Daniel Cornelio. Universidad Nacional de la Plata. Facultad de Cs.veterinarias. Laboratorio de Estudios Farmacologicos y Toxicologicos.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Gortari Castillo, Lihuel. Universidad Nacional de la Plata. Facultad de Cs.veterinarias. Laboratorio de Estudios Farmacologicos y Toxicologicos.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Buchamer, Andrea Veronica. Universidad Nacional de la Plata. Facultad de Cs.veterinarias. Laboratorio de Estudios Farmacologicos y Toxicologicos.; ArgentinaFil: Bandoni, Arnaldo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Metabolismo del Fármaco. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Metabolismo del Fármaco; ArgentinaFil: Marchetti, Maria Laura. Universidad Nacional de la Plata. Facultad de Cs.veterinarias. Laboratorio de Estudios Farmacologicos y Toxicologicos.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: Mestorino, Nora. Universidad Nacional de la Plata. Facultad de Cs.veterinarias. Laboratorio de Estudios Farmacologicos y Toxicologicos.; Argentin

Tissue depletion of doxycycline after its oral administration in food producing chicken for fattening

Doxycycline (DOX), tetracycline of second generation, is mainly active against Gram–positive and Gram–negative bacteria, aerobic and anaerobic. Although there are few pharmacokinetic studies in chickens, it is frequently used for the colibacillosis treatment, salmonellosis, staphylococcal infections, avian mycoplasmosis and chlamydia. The objective of this study was to evaluate the withdrawal time (WT) of DOX formulation at 25 % in edible tissues, after its oral (PO) use in broilers. Forty healthy chicks (30–35 days of age) were used. DOX was administered with drinking water for 5 days at 10 mg kg–1 (N = 36); four untreated animals were reserved (control). Six animals per group were euthanized by cervical dislocation after desensitization by passage of an electric current through the head, after 24 hours until 9 d post treatment and control animals also. Muscle, liver, kidney and skin/fat samples were obtained. DOX was determined by HPLC with UV detection. DOX concentrations were determined in all tissues examined; generally falling below the MRL at 7 d after administration is terminated. It was estimated 6.58, 8.18, 8.69 and 6.96 d of WT for muscle, liver, kidney and skin/fat, respectively. After DOX administration at a rate of 10 mg kg–1 for 5 days in drinking water, a WT of 9 d is suggested in poultry destined for human consumption.Fil: Mestorino, Olga Nora. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Zeinsteger, Pedro Adolfo. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Buchamer, Andrea Veronica. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Buldain, Daniel Cornelio. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Aliverti, Florencia. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Marchetti, Maria Laura. Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Residue depletion of ivermectin in broiler poultry

Helminth infections are widespread in the poultry industry. There is evidence of extra-label use of some drugs, such as ivermectin (IVM), in broiler poultry. Pharmacokinetic and residual studies of IVM in poultry, however, are rather scarce. Our aim was to determine time restrictions for broiler chickens fed with balanced feed mixed with IVM for 21 days, and thus achieve acceptable residual levels for consumption as established by the European Union. Sixty 1-day-old chicks were fed with food supplemented with IVM at 5 mg kg–1 feed for 21 days. Groups of six treated animals were sacrificed at 0, 1, 2, 4, 8, 10, 15, 20 and 28 days after treatment. Liver, skin/fat, kidney and muscle samples were obtained. IVM were determined by liquid chromatography with fluorescence detection after automatic solid-phase extraction with SPE C18 cartridges. The highest concentrations were measured in the liver, which is logical given that IVM is a drug that undergoes extensive hepatic metabolism. The optimal withdrawal time for edible tissues of these animals to stay within the permitted residual levels were: 12 days for liver, 8 days for skin/fat, 0 days for muscle and 10 days for kidney.Facultad de Ciencias Veterinaria

Combination of cloxacillin and essential oil of <i>Melaleuca armillaris</i> as an alternative against <i>Staphylococcus aureus</i>

The emergence of resistance to antibiotics has been favored by abuse in the application of antimicrobials in human and animal medicine. Essential oils are a great resource to deal with this crisis. Melaleuca armillaris belongs to the family of Myrtaceae, rich in species with essential oils. Plant extracts has shown antimicrobial activity in many investigations. Cloxacillin (CLOX) is an antibiotic widely used in veterinary medicine against Staphylococcus aureus. Our aim was to assess pharmacodynamic interaction established by combining essential oil of M. armillaris (EO) with CLOX in search of a synergistic effect that maximizes the antibacterial activity against S. aureus. The EO was obtained by steam distillation and its composition was analyzed by a GC-FID-MS. The most abundant components in the EO were 1.8 cineole (72.3%), limonene (7.8%). and a-pinene (6%). We worked with wild type S. aureus strains (n = 3) isolated from Holstein cows, and S. aureus ATCC 29213 as the reference strain. The Minimum Inhibitory Concentration (MIC) of CLOX, EO and the combination was determined by microdilution in broth at pH 7.4; 6.5 and 5.0. The checkerboard method was applied to evaluate the interaction between CLOX and EO. The Fractional Inhibitory Concentration index (FIC) was established. From those combinations that yielded the lowest FIC values, we evaluated the index of antibacterial activity (E), established as the difference between the Log10 values of the number of viable bacteria at the initial (nt0) and at the end of the test (nt24). So, time-killing curves with CLOX and EO/CLOX combination at 0.5, 1, 2, 4, and 8 fold the MIC in broth at pH 7.4; 6.5 and 5.0 were prepared. We considered Bacteriostatic effect (E = 0) Bactericidal effect (E = -3) and Effect of virtual eradication of bacteria (E = -4). A clear synergic activity between the EO and the CLOX was demonstrated, which allows reducing the MIC of β-lactam against S. aureus. This interaction was favored by acidification of the medium, where lower concentrations of CLOX achieved a bactericidal effect, close to virtual eradication, in the presence of small amounts of EO.Facultad de Ciencias Veterinaria

Enrofloxacin and Ciprofloxacin Residues in Broiler Chicken Feathers after Enrofloxacin Oral Administration

Antibiotics in animal feed are a public health concern. Drug residues could eventually be detected in animal food products intended for human consumption. Our aim was to study the residue depletion of enrofloxacin and its metabolite ciprofloxacin in broiler chicken feathers. A validated HPLC-fluorescence method was used to quantify both compounds in feather samples. Broiler chickens were treated through drinking water with 10 mg Kg-1 d of enrofloxacin for 5 consecutive days. Feather samples were taken from 10 random birds per day until 9 days. Extraction was performed by a liquid/liquid technique. Both fluoroquinolones concentrations were determined by liquid chromatography with fluorescence detection. High levels of enrofloxacin and ciprofloxacin were found in feathers after oral administration and these compounds were detected for 9 days. Feather meal is a potential source of drug residues that can pass through the food chain when contaminated meal is fed to food-producing animals. In the present study enrofloxacin and ciprofloxacin concentrations were 0.20 to 5.46 μg g-1 between 1 to 9 days after final treatment, which means that withdrawal time fit for edible tissues is not adequate to reduce antimicrobial residues in chicken feathers. Further studies to establish a withdrawal time may be useful to avoid that drug residues could result in adverse health consequences like increase in antibiotic resistance.Facultad de Ciencias Veterinaria

Pseudomonas aeruginosa in canine otitis externa: current situation

La otitis externa es una enfermedad de presentación frecuente en la práctica diaria. La comprensión de su fisiopatología es importante para su prevención, diagnóstico y tratamiento. El protocolo diagnóstico debe ser estricto, siendo fundamental el rol que cumplen en estos casos el cultivo bacteriano y el antibiograma. Pseudomonas aeruginosa es un microorganismo oportunista e invasor, que constituye en sí mismo un factor perpetuante para las otitis crónicas. Además de sus factores de virulencia y la resistencia intrínseca a múltiples fármacos, forma biopelículas de protección sobre tejidos colonizados y posee gran capacidad para adquirir genes determinantes de resistencia cromosómica y extra cromosómica durante el tratamiento. Los casos crónicos o recurrentes con aislamientos de P. aeruginosa resultan un desafío constante para el veterinario. El oído externo tiene escasa irrigación, por lo cual los antimicrobianos sistémicos no alcanzan concentraciones adecuadas, siendo la terapia tópica la primera elección. El éxito terapéutico evoluciona hacia la aplicación de pautas farmacocinéticas/farmacodinámicas, desde una concepción netamente empírica hasta una concepción cuantitativa, permitiendo describir y simular el efecto de un antibiótico sobre una población bacteriana en función del tiempo, mediante la modelización matemática de los datos experimentales, con objeto de maximizar la eficacia y minimizar fenómenos de resistencia.Otitis externa is a frequent disease in veterinary small animal practice. Understanding its pathophysiology is important for prevention, diagnosis, and treatment. The diagnostic protocol must be strict, where bacterial culture and antibiogram play an essential role. Pseudomonas aeruginosa is an opportunistic and invasive microorganism, which by itself constitutes a perpetuating factor for chronic otitis. In addition to its virulence factors and intrinsic resistance to multiple drugs, it forms protective biofilms on colonized tissues, and has a great capacity to acquire genes that determine chromosomal and extra chromosomal resistance during the antibiotic treatment. Management of chronic or recurrent cases of otitis by P. aeruginosa is a constant challenge for veterinarians. Since the outer ear is a scarcely irrigated tissue, the use of systemic antimicrobials does not reach adequate local concentrations, leaving topical therapy as the first choice of treatment. Treatment success should consider application of pharmacokinetic/pharmacodynamic guidelines not only from a purely empirical conception, but also from a quantitative conception, which allows description and simulation ofthe effect of an antibiotic on a bacterial population as function of time through mathematicalmodelling of the experimental data, in order to maximize the effectiveness and minimize resistance selection.Facultad de Ciencias Veterinaria