Susceptibilidad a antibióticos y desinfectantes en bacterias de sedimento marino provenientes de centros de cultivo de salmón en la Región de Los Lagos, Chile.
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Date
2025
Journal Title
Journal ISSN
Volume Title
Publisher
Universidad de Concepción
Abstract
En Chile, la industria salmonera ha experimentado un rápido desarrollo, posicionándose como segundo líder mundial en la producción de salmón en cultivo a gran escala. Sin embargo, esta actividad ha generado impactos ambientales significativos. Unos de los principales problemas es la propagación de enfermedades bacterianas, facilitadas por el hacinamiento y estrés de los peces. En este contexto, el uso de agentes antimicrobianos es una de las principales herramientas para el combate de enfermades infecciosas de origen bacteriano. Por otro lado, el uso de biocidas, especialmente desinfectantes, es fundamental para mantener la inocuidad y así evitar la propagación de infecciones. En consideración de lo anterior, el estudio de sedimentos marinos en áreas bajo distintos regímenes de uso de antibióticos representa una fuente interesante para estudiar la resistencia a antibióticos y desinfectantes.
Se aislaron bacterias 43 bacterias desde sedimentos marinos provenientes de centros clasificados según su nivel de exposición a antibióticos (alto, bajo y prístino). Las muestras se sembraron agar TSA + NaCl 1,5% y se incubaron a 15°C por 48 h. Se seleccionaron morfotipos y se determinó la susceptibilidad a siete antibióticos usados en la industria del salmón mediante antibiogramas, a partir de donde se calculó el índice MAR (multiple antibiotic resistance) y el índice de resistencia a antibióticos (IRA). Además, para tres desinfectantes (hipoclorito de sodio, peróxido de hidrógeno y amonio cuaternario) se determinó la concentración mínima inhibitoria (CMI) mediante dilución seriada en caldo. De los aislados totales, 37 correspondieron a bacilos Gram negativos, principalmente no fermentadores. En los tres sitios analizados, un 28% de los aislados presentaron halos de inhibición ≤14 mm, lo que sugiere la presencia de mecanismos de resistencia a antibióticos. Con los índices MAR e IRA se determinó que no hubo diferencias significativas entre los sitios con diferentes regímenes de uso de antibióticos. Respecto a los desinfectantes, se determinó que todos los aislados fueron categorizados como susceptibles de acuerdo con los valores de CMI obtenidos. Finalmente, los análisis de correlación entre antibióticos y desinfectantes no evidenciaron una relación directa entre la resistencia directa entre ambos grupos de compuestos antimicrobianos.
In Chile, the salmon industry has experienced rapid development, positioning itself as the second world leader in large-scale farmed salmon production. However, this activity has generated significant environmental impacts. One of the main problems is the spread of bacterial diseases, facilitated by overcrowding and stress of the fish. In this context, the use of antimicrobial agents is one of the main tools for combating infectious diseases of bacterial origin. On the other hand, the use of biocides, especially disinfectants, is essential to maintain safety in the soil and thus prevent the spread of infections. In consideration of the above, the study of marine sediments in areas under different antibiotic use regimens represents an interesting source to study resistance to antibiotics and disinfectants. 43 bacteria were isolated from marine sediments from centers classified according to their level of exposure to antibiotics (high, low and pristine). The samples were seeded TSA agar + 1.5% NaCl and incubated at 15°C for 48 h. Morphotypes were selected and susceptibility to seven antibiotics used in the salmon industry was determined by means of antimicrobial susceptibility tests, from which the MAR index (multiple antibiotic resistance) and the antibiotic resistance index (ARI) were calculated. In addition, for three disinfectants (sodium hypochlorite, hydrogen peroxide and quaternary ammonium) the minimum inhibitory concentration (MIC) was determined by serial dilution in broth. Of the total isolates, 37 corresponded to Gram-negative bacilli, mainly non-fermenters. In the three sites analyzed, 28% of the isolates had inhibition halos ≤ 14 mm, suggesting the presence of antibiotic resistance mechanisms. With the MAR and IRA indices, it was determined that there were no significant differences between sites with different antibiotic use regimens. Regarding disinfectants, it was determined that all isolates were categorized as susceptible according to the MIC values obtained. Finally, the correlation analyses between antibiotics and disinfectants did not show a direct relationship between the two groups of antimicrobial compounds.
In Chile, the salmon industry has experienced rapid development, positioning itself as the second world leader in large-scale farmed salmon production. However, this activity has generated significant environmental impacts. One of the main problems is the spread of bacterial diseases, facilitated by overcrowding and stress of the fish. In this context, the use of antimicrobial agents is one of the main tools for combating infectious diseases of bacterial origin. On the other hand, the use of biocides, especially disinfectants, is essential to maintain safety in the soil and thus prevent the spread of infections. In consideration of the above, the study of marine sediments in areas under different antibiotic use regimens represents an interesting source to study resistance to antibiotics and disinfectants. 43 bacteria were isolated from marine sediments from centers classified according to their level of exposure to antibiotics (high, low and pristine). The samples were seeded TSA agar + 1.5% NaCl and incubated at 15°C for 48 h. Morphotypes were selected and susceptibility to seven antibiotics used in the salmon industry was determined by means of antimicrobial susceptibility tests, from which the MAR index (multiple antibiotic resistance) and the antibiotic resistance index (ARI) were calculated. In addition, for three disinfectants (sodium hypochlorite, hydrogen peroxide and quaternary ammonium) the minimum inhibitory concentration (MIC) was determined by serial dilution in broth. Of the total isolates, 37 corresponded to Gram-negative bacilli, mainly non-fermenters. In the three sites analyzed, 28% of the isolates had inhibition halos ≤ 14 mm, suggesting the presence of antibiotic resistance mechanisms. With the MAR and IRA indices, it was determined that there were no significant differences between sites with different antibiotic use regimens. Regarding disinfectants, it was determined that all isolates were categorized as susceptible according to the MIC values obtained. Finally, the correlation analyses between antibiotics and disinfectants did not show a direct relationship between the two groups of antimicrobial compounds.
Description
Tesis presentada para optar al título de Ingeniero/a en Biotecnología Marina y Acuicultura.
Keywords
Industria del salmón, Farmacorresistencia microbiana, Ecología marina