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The increasing worldwide usages of Veterinary Antibiotics (VAs) for therapeutic and nontherapeutic are becoming serious issue due to its adverse effects on all living organisms. Release of VAs into the aquatic and terrestrial environments results in antibiotic resistance in bacteria and toxicity to humans, animals, and plants. This review covers the present scenario on VA usage, occurrence, toxicity, and removal techniques.

Interest in biological control of plant pathogens has been stimulated in recent years by trends in agriculture towards greater sustainability and public concern about the use of hazardous pesticides. There is now unequivocal evidence that antibiotics play a key role in the suppression of various soilborne plant pathogens by antagonistic microorganisms. The significance of antibiotics in biocontrol, and more generally in microbial interactions, often has been questioned because of the indirect nature of the supporting evidence and the perceived constraints to antibiotic production in rhizosphere environments. Reporter gene systems and bio-analytical techniques have clearly demonstrated that antibiotics are produced in the spermosphere and rhizosphere of a variety of host plants. Several abiotic factors such as oxygen, temperature, specific carbon and nitrogen sources, and microelements have been identified to influence antibiotic production by bacteria biocontrol agents. Among the biotic factors that may play a determinative role in antibiotic production are the plant host, the pathogen, the indigenous microflora, and the cell density of the producing strain. This review presents recent advances in our understanding of antibiotic production by bacterial biocontrol agents and their role in microbial interactions.

The weaning time is a crucial period in the management of piglets. The risk of development of post-weaning diarrhoea (PWD) in piglets is high. PWD is the cause of serious economic losses in pig herds. Since 2006, the use of antibiotic growth promoters for prevention of diarrhoeal diseases in piglets has been banned. This measure also led to the investigation of alternative suitable feed supplements that would be reasonably efficient in protecting and sustaining animal health and performance. Various natural materials such as probiotics, prebiotics, organic acids, zinc and plant extracts have been tested as effective alternatives to antibiotics. Recently, owing to their high adsorption capacity, research efforts have been conducted on the application of natural clays and clay-based feed supplements. The purpose of this review is to summarize the effect of different alternative components as growth promoters on the health and performance of weaned and growing piglets.

This study was carried out to detect the distribution of antibiotic-resistant genes in Escherichia coli isolates from slaughtered commercial chickens in Iran by PCR. The investigated genes included aadA1, tet(A), tet(B), dfrA1, qnrA, aac(3)-IV, sul1, blaSHV, blaCMY, ere(A), catA1 and cmlA. According to biochemical experiments, 57 isolates from 360 chicken meat samples were recognized as E. coli. The distribution of antibiotic-resistance genes in the E. coli isolates included tet(A) and tet(B) (52.63%), dfrA1, qnrA, catA1 and cmlA (36.84%) and sul1 and ere(A) (47.36%), respectively. Nine strains (15.78%) were resistant to a single antimicrobial agent and 11 strains (19.29%) showed resistance to two antimicrobial agents. Multi-resistance which was defined as resistance to three or more tested agents was found in 64.91% of E. coli strains. The results indicate that all isolates harbour one or more of antibiotic resistance genes and that the PCR technique is a fast, practical and appropriate method for determining the presence of antibiotic-resistance genes.

Background: Coccidiosis is the infectious disease with the greatest economic impact in poultry production. Additionally, chemotherapeutic growth promoters are being substituted for safer alternative strategies. Objective: To evaluate the effect of feeding oleoresins from chili pepper (Capsicum annuum) and turmeric (Curcuma longa L.) on the performance, survival rate, and the Productive Efficiency Index of broilers from 1 to 21d challenged by Eimeria sp. Methods: A total of 700 male 1-dayold chicks (Cobb 500) challenged with Eimeria sp, were assigned to a completely randomized design with four treatments: (1) negative control diet, without anticoccidial agent or growth promoters; (2) control diet+0.05% salinomycin; (3) negative control diet+100g/ton; and (4) negative control diet +140g/ton of test product (Curcuma longa L. plus Capsicum annuum oleoresins). Results: Body weight, weight gain, feed conversion and Productive Efficiency Index did not differ between broilers fed anticoccidial chemotherapeutics and oleoresins. In addition, there was no difference in feed intake and survival rate between dietary treatments. Conclusion: Broilers supplemented with chili pepper and turmeric oleoresins from 1 to 21d present similar body weight, weight gain, feed conversion, and Productive Efficiency Index compared to broilers supplemented with chemotherapeutic anticoccidials without affecting feed intake or survival rate.

Background: Antibiotic resistance is a global public health problem. To date, there are limited studies focused on Escherichia coli isolated from pig herds in Colombia. Objective: This study aimed to evaluate antibiotic resistance in non-pathogenic strains of E. coli isolated from pig farms located in Valle del Cauca, Colombia. Methods: The hemolytic capacity and the presence of heat-labile (LT) and heat-stable (STa and STb) toxins were evaluated. Subsequently, Antibiotic resistance was assessed in γ-hemolytic strains against 11 commonly used antibiotics. Results: A total of six E. coli strains were isolated. The strains exhibited a high level of antibiotic resistance. The highest resistance prevalence was observed against amikacin (20%), ceftiofur (20%), fosfomycin (20%), ciprofloxacin (40%), gentamicin (40%), florfenicol (80%), enrofloxacin (80%), norfloxacin (80%), apramycin (100%), ampicillin (100%), and doxycycline (100%). Conclusions:Commensal E. coli strains from piglets pose a high epidemiological risk as reservoirs and disseminators of resistance genes within the pig production chain. Additionally, these strains may represent a potential risk to the food chain. Antecedentes:A resistência aos antibióticos é um problema de saúde pública global. Até o momento, existem poucos estudos focados em Escherichia coli isolada de rebanhos suínos na Colômbia. Objetivo: Este estudo teve como objetivo avaliar a resistência a antibióticos de cepas não patogênicas de E. coli isoladas de granjas de suínos. Métodos: Foram utilizadas seis cepas de E. coli não patogênicas isoladas de estudos anteriores. Avaliou-se a capacidade hemolítica e a presença de toxinas termo-lábeis (LT) e termo-estáveis (STa e STb) por meio de amplificação genética, com tamanhos esperados de STa: 163 bp, STb: 368 bp e LT: 275 bp. Por fim, avaliou-se a resistência a 11 antibióticos de uso comum em cepas γ-hemolíticas. Resultados: As cepas apresentaram multirresistência a antibióticos. A maior prevalência de resistência foi observada contra amicacina (20%), ceftiofur (20%), fosfomicina (20%), ciprofloxacina (40%), gentamicina (40%), florfenicol (80%), enrofloxacina (80%), norfloxacina (80%), apramicina (100%), ampicilina (100%) e doxiciclina (100%). Conclusões: Cepas comensais de E. coli isoladas de leitões representam um alto risco de disseminação de genes de resistência na cadeia produtiva suína e podem ingressar na cadeia alimentar, contribuindo para a transferência de resistência antimicrobiana a humanos. Esses achados são de grande relevância para a implementação de estratégias de controle e prevenção da resistência antimicrobiana na indústria suína e para a proteção da saúde pública. Antecedentes: La resistencia a los antibióticos es un problema de salud pública mundial. A la fecha, existen pocos estudios centrados en Escherichia coli aislada de hatos porcinos en Colombia. Objetivo: Este estudio tuvo como objetivo evaluar la resistencia a antibióticos de cepas no patógenas de E. coli aisladas de granjas porcinas del Valle del Cauca, Colombia. Métodos: Se usaron seis cepas de E. coli no patógenas aisladas de estudios previos. Se evaluó la capacidad hemolítica de las cepas y la presencia de toxinas termolábiles (LT) y termoestables (STa y STb) mediante amplificación genética, con tamaños esperados de STa: 163 bp, STb: 368 bp, y LT: 275 bp. Finalmente, se evaluó la resistencia a 11 antibióticos de uso común en cepas γ-hemolíticas. Resultados: Las cepas presentaron multirresistencia a antibióticos. La mayor prevalencia de resistencia se observó contra amikacina (20%), ceftiofur (20%), fosfomicina (20%), ciprofloxacina (40%), gentamicina (40%), florfenicol (80%), enrofloxacina (80%), norfloxacina (80%), apramicina (100%), ampicilina (100%) y doxiciclina (100%). Conclusiones: Las cepas comensales de E. coli aisladas de lechones representan un alto riesgo de diseminación de genes de resistencia en la cadena productiva porcina y pueden ingresar a la cadena alimentaria, contribuyendo a la transferencia de resistencia antimicrobiana a humanos. Estos hallazgos son de gran importancia para la implementación de estrategias de control y prevención de la resistencia antimicrobiana en la industria porcina y la protección de la salud pública.

A total of 669 individual cow milk samples originating from asymptomatic cows from 16 dairy farms were examined for the presence of microorganisms with the potential to cause mastitis. Coagulase-negative staphylococci clearly predominated (53.5% positive samples) followed by streptococci and enterococci (both occurring in 16.1% samples). Among streptococci, so-called mastitis streptococci (S. uberis, S. dysgalactiae and S. agalactiae) prevailed (11.7% positive samples). Enterobacteriaceae were found in 10.0% samples, most of which (6.6% samples) were positive for Escherichia coli. Yeasts (mainly Candida spp.) were found in 8.2% samples. One of the major mastitis pathogens, Staphylococcus aureus subsp. aureus, was isolated from 9.0% of samples. S. aureus isolates were further characterised in terms of their capability to form biofilm, antimicrobial susceptibility and clonality (PFGE). All S. aureus isolates were capable of biofilm formation and were generally susceptible to the majority of tested antibiotics. The exception was ampicillin, resistance to which was observed in 27.7% isolates. Therefore, the relatively frequent occurrence of S. aureus could be attributed to persistent intramammary infections due to biofilm formation rather than low efficacy of particular antibiotics. PFGE analysis revealed clonal spread of certain S. aureus isolates within and between farms indicating that certain lineages of S. aureus mastitis strains are particularly successful.

Background: Antimicrobial resistance (AMR) and the increase in multi-drug-resistant bacteria are among the most important threats to human and veterinary medicine, according to the World Health Organization. Objective: To compare the antimicrobial susceptibility patterns in bacterial isolates from dogs over two consecutive four-year periods. Methods:The Animal Microbiology Laboratory database of the Agrarian Sciences Faculty at the University of Antioquia (Medellín, Colombia) was searched for routine canine submissions in which culture and antibiograms were performed. Results: A total of 1,146 samples were submitted between 2020 and August 2023 for culture and susceptibility testing, from which 805 (70.2%) isolates were recovered. Of these 805 isolates, susceptibility testing was performed on 799 samples. A significant decrease in susceptibility between 2016-2019 and 2020-August 2023 was noted in dog isolates for some antimicrobials: Escherichia coli to amoxicillin-clavulanate (66.7-53.1%; p<0.01) and ampicillin (67.7-58%; p<0.05), Enterobacteriaceae to amikacin (100-94.3%; p<0.01), ampicillin (61.8-45.7%; p<0.01), and trimethoprim-sulfadiazine (83.9-75.6%; p<0.05), Staphylococcus pseudointermedius to gentamicin (63.9-52.5%; p<0.01), trimethoprim-sulfadiazine (57-50%; p<0.05), and doxycycline (60.9-43.4%; p<0.01). Significantly increased susceptibilities were also noted in E. coli to enrofloxacin (69.2-78.7%; p<0.05) and doxycycline (68.7-76.2%; p=0.0745) and in Enterobacteriaceae to enrofloxacin (64.4-79.3%; p<0.01), and doxycycline (38.7-47.7%; p=0.06). For all bacterial isolates, an increasing resistance trend was observed for amoxicillin-clavulanate. All Staphylococcus species showed low resistance to amikacin (<10%); moderate resistance (10-20%) to amoxicillin-clavulanate, cephalexin, cefovecin, and enrofloxacin; high resistance (20-50%) to ampicillin, gentamicin, trimethoprim-sulfadiazine, and clindamycin; and very high resistance (50-70%) to doxycycline. For other bacterial families, the number of antimicrobials with high (20-50%) or very high (50-70%) resistance rates was: Enterobacteriaceae (7/9), Enterococcus spp. (4/7), E. coli (10/12), and Streptococcus spp. (4/6). For urinary tract infections caused by E. coli or Enterobacteriaceae (Klebsiella spp., Proteus spp.), amikacin and gentamicin were the only drugs that demonstrated low (<10%) in vitro resistance. Multidrug resistance slightly increased from 2016-2019 (18.7%; 247/1,316) to 2020-August 2023 (19.7%; 150/761). decrease in susceptibility rather than an increase in resistance (28 vs. 20). Conclusion: High resistance rates highlight the need for continued surveillance and reinforce the importance of antibiograms to guide clinical decisions. Antecedentes: A resistência antimicrobiana (RAM) e o aumento de bactérias multirresistentes estão entre as ameaças mais importantes à medicina humana e veterinária, de acordo com a Organização Mundial da Saúde. Objetivo: Comparar os padrões de suscetibilidade antimicrobiana em isolados de cães em 2 períodos consecutivos de 4 anos. Métodos: Pesquisamos no banco de dados do Laboratorio de Microbiología Animal da Faculdade de Ciências Agrárias da Universidad de Antioquia (Medellín, Colombia) os envios dos isolados de cães de rotina para os quais foram realizados cultura e antibiogramas. Resultados: Foram enviadas 1.146 amostras entre 2020 e agosto de 2023 para cultura e determinação de sensibilidade, das quais 805 (70,2%) isolados puderam ser recuperados. Destes 805 isolados, a sensibilidade foi determinada em 799 amostras. Foi observada uma diminuição significativa entre 2016-2019 e 2020-agosto 2023 na suscetibilidade de isolados de cães aos alguns antimicrobianos: Escherichia coli à amoxicilina-clavulanato (66,7-53,1%; p<0,01) e ampicilina (67,7-58%; p<0,05), Enterobacteriaceae para amicacina (100-94,3%; p<0,01), ampicilina (61,8-45,7%; p<0,01) e trimetoprim-sulfadiazina (83,9-75,6; p<0,05), Staphylococcus pseudointermedius à gentamicina (63,9-52,5%, p<0,01), trimetoprim-sulfadiazina (57-50%; p<0,05) e doxiciclina (60,9-43,4%; p<0,01). Suscetibilidades significativamente aumentadas também foram observadas como segue: E. coli à enrofloxacina (69,2-78,7%; p<0,05), doxiciclina (68,7-76,2%; p=0,0745), Enterobacteriaceae à enrofloxacina (64,4-79,3%; p<0,01) e doxiciclina (38,7-47,7%; p=0,06). Para todos os tipos de bactérias houve um aumento do padrão de resistência contra amoxicilina-clavulanato. Todas as espécies de Staphylococcus apresentaram baixa resistência à amicacina (<10%); resistência moderada (10-20%) à amoxicilina-clavulanato, cefalexina, cefovecina e enrofloxacina; alta resistência (20-50%) à ampicilina, gentamicina, trimetoprim-sulfadiazina e clindamicina; e resistência muito elevada (50-70%) à doxiciclina. Para outras famílias de bactérias, o número de antimicrobianos para os quais a resistência foi alta (20-50%) ou muito alta (50-70%) foi: Enterobacteriaceae(7/9), Enterococcus spp. (4/7), E. coli (10/12) e Streptococcus spp. (4/6). Para infecções do trato urinário causadas por E. coli ou Enterobacteriaceae (Klebsiella spp., Proteus spp.), a amicacina e a gentamicina foram os únicos medicamentos que demonstraram baixa (<10%) resistência in vitro. O grau de multirresistência aumentou ligeiramente no período de 2020-agosto 2023 (19,7%; 150/761 isolados) em comparação com o período de 2016-2019 (18,7%; 247/1.316). Isto foi atribuído a uma redução significativa da suscetibilidade, e não a aumentos de suscetibilidade (28 vs. 20). Conclusões: Altas taxas de resistência indicam vigilância contínua e o uso de antibiogramas é necessário para orientar as decisões clínicas. Antecedentes: La resistencia a los antimicrobianos (RAM) y el aumento de bacterias multirresistentes se encuentran entre las amenazas más importantes para la medicina humana y veterinaria según la Organización Mundial de la Salud. Objetivo: Comparar los patrones de susceptibilidad a los antimicrobianos en aislamientos de perros en dos períodos consecutivos de 4 años. Métodos:Pesquisamos no banco de dados do Laboratorio de Microbiología Animal de la Facultad de Ciencias Agrarias de la Universidad de Antioquia (Medellín, Colombia) en busca de envíos rutinarios de muestras clínicas de perros para las cuales se realizaron cultivos y antibiogramas. Resultados: Un total de 1.146 muestras fueron enviadas entre 2020 y agosto de 2023 para cultivo y determinación de sensibilidad, de las cuales se pudieron recuperar 805 (70,2%) aislamientos. De esos 805 aislamientos se determinó sensibilidad en 799 muestras. Se observó una disminución significativa entre 2016-2019 y 2020-agosto 2023 en la susceptibilidad de las cepas bacterianas aisladas de perros a algunos antimicrobianos: Escherichia coli a amoxicilina-clavulanato (66,7-53,1%; p<0,01) y ampicilina (67,7-58%; p<0,05), Enterobacterias a amikacina (100-94,3%; p<0,01), ampicilina (61,8-45,7%; p<0,01) y trimetoprim-sulfadiazina (83,9-75,6%; p<0,05), Staphylococcus pseudointermedius a gentamicina (63,9-52,5%; p<0,01), trimetoprim-sulfadiazina (57-50%; p<0,05) y doxiciclina (60,9-43,4%; p<0,01). También se observaron aumentos significativos en la susceptibilidad de E. coli a enrofloxacina (69,2-78,7%; p<0,05), doxiciclina (68,7-76,2%; p=0,0745), Enterobacteriaceae a enrofloxacina (64,4- 79,3%; p<0,01) y doxiciclina (38,7-47,7%; p=0,06). Para todos los tipos de bacterias hubo un incremento de la resistencia contra la amoxicilina-clavulanato. Todas las especies de Staphylococcus mostraron baja resistencia a la amikacina (<10%); resistencia moderada (10-20%) a amoxicilina-clavulanato, cefalexina, cefovecina y enrofloxacina; alta resistencia (20-50%) a ampicilina, gentamicina, trimetoprim-sulfadiazina y clindamicina; y resistencia muy alta (50-70%) a la doxiciclina. Para otras familias de bacterias, el número de antimicrobianos con resistencia alta (20-50%) o muy alta (50-70%) fue: Enterobacteriaceae (7/9), Enterococcus spp. (4/7), E. coli (10/12) y Streptococcus spp. (4/6). Para las infecciones del tracto urinario causadas por E. coli o Enterobacteriaceae (Klebsiella spp., Proteusspp.), la amikacina y la gentamicina fueron los únicos fármacos que demostraron baja resistencia in vitro(<10%). El grado de multirresistencia aumentó ligeramente para el período 2020-agosto 2023 (19,7%; 150/761 aislamientos) en comparación con el período 2016-2019 (18,7%; 247/1.316). Esto se atribuyó a una reducción significativa de la susceptibilidad en lugar de a un aumento de la susceptibilidad (28 vs. 20). Conclusión: Las altas tasas de resistencia indican que se necesita vigilancia continua y el uso de antibiogramas para guiar las decisiones clínicas.

Multidrug resistance is the phenomenon by which, after exposure to a single chemotherapeutic agent, cancer cells evade the agent's cytotoxic effects as well as become resistant to several classes of diverse drugs. ATP-binding cassette (ABC) transporters are a family of transporter proteins that contribute to drug resistance via a n ATP-dependent drug efflux pump. P-glycoprotein (P-gp) is a prominent ABC superfamily protein encoded by the mdr gene which has the ability to mediate the cellular extrusion of xenobiotics and anticancer drugs from tumor cells. Exclusively expressed P-gp cells from the human colon cancer HCT15/DOX line showed resistance to doxorubicin while parental HCT15 cells treated with doxorubicin displayed typical signs of apoptosis. In order to verify the hypothesis that expression of MDR is controlled in part, by protein kinase C (PKC), expression patterns of different PKC isoforms were examined in both cell lines. Of the PKC isoforms evaluated, the membrane translocation and expression levels of PKCα were strikingly increased in HCT15/DOX cells. PKCα reversed doxorubicin-induced apoptosis through the scavenging of ROS as well as inhibition of PARP cleavage. In addition, inhibition of PKCα with Go6976, a specific inhibitor of classical PKC, led to reduced MDR expression and increased doxorubicin-induced apoptosis. Knockdown of PKCα by siRNA diminished the protective effects of PKCα for doxorubicin-induced apoptosis. These results suggested that over-expression and activity of PKCα is closely associated with the regulation of the MDR phenotype in human colon cancer HCT15 cells and provided insight into a new strategy for inhibiting doxorubicin resistance in human cancers.

Background: Commensal microflora such as Escherichia coli and Enterococcus spp. are representative indicators of antimicrobial resistance (AMR) as they are part of the normal intestinal microflora and can acquire and disseminate AMR to pathogenic or zoonotic bacteria like Salmonella spp. Objective: To investigate the state of AMR among E. coli and Salmonella spp., potential pathogens in humans, isolated from cecal contents of pigs submitted to a veterinary diagnostic laboratory in Colombia from 2016 to 2019. Methods: Susceptibility testing was conducted using the Kirby-Bauer disk diffusion method according to the Clinical and Laboratory Standards Institute guidelines for antimicrobial zone diameter breakpoints. An E. coli strain (ATCC 25922) was used as the quality control organism. Isolates showing resistance to three or more antimicrobial classes were classified as multidrug-resistant (MDR) as defined by a joint group of the European Centre for Disease prevention and Control and the Center for Disease Control and Prevention of the USA. Results: A total of 112 E. coli and 192 Salmonella spp. colonies were isolated from 557 samples received between 2016 and 2019. In order of decreasing frequency, E. coli was resistant to tetracycline (100%), sulfamethoxazol-trimethoprim (97.5%), amoxicillin (86.4%), enrofloxacin (82.6%), tylosin (82.1%), doxycycline (59%), neomycin (50%), ciprofloxacin (45.5%), ceftiofur (35%), gentamicin (30%), tilmicosin (29%), and fosfomycin (12.5%). When compared with E. coli, Salmonella spp. was generally resistant to the same agents with slightly less resistance (between 10-30%) to eight of the antimicrobials tested. Salmonella spp. showed <20% resistance to three antimicrobials, as follows: neomycin (17%), gentamicin (16%), and fosfomycin (14%). Multi-resistance occurred in 68.7% (77/112) of E. coli and 70.3% (135/192) of Salmonella spp. isolates. Resistance of Salmonella spp. was alarming to all the critically important antimicrobials tested: fluoroquinolones (enrofloxacin, ciprofloxacin), ceftiofur (thirdgeneration cephalosporin), and macrolides (tylosin). Conclusions: According to our results, there is a high level of multidrug resistance (MDR) in E. coli and Salmonella spp. It is necessary to implement a nationwide antimicrobial resistance monitoring program in Colombia, together with proper antimicrobial prescribing guidelines for pigs. The indiscriminate use of antimicrobial growth promoters by the swine industry is generating widespread bacterial resistance and should be discontinued.