Staphylococcus haemolyticus and Providencia vermicola Infections Occurring in Farmed Tilapia: Two Potentially Emerging Pathogens.

This work aimed to determine the presence of bacterial pathogens in fish with a clinical picture suggestive of infectious disease in Nile tilapia reared in Chiapas, Mexico. Blood and viscera samples were taken from healthy and diseased animals from commercial farms. Clinical and pathological examinations of each individual were performed and samples were collected for bacteriological studies. The bacterial isolates were identified and characterized by culture, biochemical tests, antibiogram, challenge tests and 16S rRNA sequencing. Staphylococcus haemolyticus and Providencia vermicola were isolated from various diseased organisms. The clinical picture caused by Staphylococcus haemolyticus was characterized by appetite disorders, neurological signs, nodulation or ulceration in different areas and congestion or enlargement of internal organs. Providenciosis in juvenile specimens caused a characteristic picture of hemorrhagic septicemia. Challenge tests performed in healthy organisms revealed that both infections caused higher mortality rates in fish (p < 0.05) compared with non-infected specimens, with 100% survival. There was 100% mortality for animals infected with P. vermicola after three days post infection and 45% for those infected with S. haemolyticus. The isolation and identification of two pathogens involved in an infection process were achieved and cataloged as potential causal agents of disease outbreaks in tilapia farming in Mexico. This is the first report of possible bacterial infection caused by S. haemolyticus and P. vermicola in tilapia farms, which are two uncommon but potentially emerging pathogens for the species.

Granulomatous bacterial diseases in fish: An overview of the host's immune response.

Bacterial diseases represent the main impediment to the development of fish aquaculture. Granulomatous diseases caused by bacteria lead to fish culture losses by high mortality rates and slow growth. Bacteria belonging to genera Streptococcus spp., Mycobacterium sp., Nocardia sp., Francisella sp., and Staphylococcus sp. have been implicated in the development of granulomatous processes. The granuloma formation and the fish's immune response continue to be the subject of scientific research. In fish, the first defense line is constituted by non-specific humoral factors through growth-inhibiting substances such as transferrin and antiproteases, or lytic effectors as lysozyme and antimicrobial peptides, and linking with non-specific phagocyte responses. If the first line is breached, fish produce antibody constituents for a specific humoral defense inhibiting bacterial adherence, as well as the mobilization of non-phagocytic host cells and counteracting toxins from bacteria. However, bacteria causing granulomatous diseases can be persistent microorganisms, difficult to eliminate that can cause chronic diseases, even using some immune system components to survive. Understanding the infectious process leading to granulomatosis and how the host's immune system responds against granulomatous diseases is crucial to know more about fish immunology and develop strategies to overcome granulomatous diseases.

Evaluación de un antígeno de Brucella abortus para aglutinación en placa como prueba tamiz en el diagnóstico de la brucelosis bovina / Evaluation of a Brucella abortus antigen for plaque agglutination as screening test in the diagnosis of bovine brucellosis

Este trabajo tuvo como objetivo obtener y validar un antígeno buferado de Brucella abortus para la prueba de aglutinación en placa como prueba diagnóstica de base de la brucelosis bovina. Se formularon tres lotes de antígeno a partir de la multiplicación de la cepa 99 de Brucella abortus. Se realizaron los controles de calidad correspondientes (determinación de pH, volumen celular, esterilidad, capacidad buferante) y las pruebas serológicas para la evaluación del desempeño. Se emplearon 1070 muestras de suero bovino (350 positivas y 720 negativas) previamente controladas con las pruebas de diagnóstico establecidas. Se determinó la sensibilidad y especificidad diagnóstica y relativa, los valores predictivos positivos y negativos, la eficacia y la concordancia. En los tres lotes todas las características evaluadas resultaron estar dentro de los parámetros establecidos para este tipo de producto. La especificidad y sensibilidad diagnósticas fueron de 99,5 por ciento y 100 por ciento respectivamente. El valor predictivo positivo fue de 99,1 por ciento, el valor predictivo negativo fue de 100 por ciento y la eficacia de un 99,7 por ciento. El antígeno mostró una sensibilidad y especificidad relativas de un 100 por ciento y la concordancia resultó ser clasificada como muy buena. La evaluación del desempeño arrojó resultados satisfactorios, demostrando que el método de producción empleado es factible para la obtención de un producto con adecuada eficacia(AU)

The objective of this work was to obtain and validate a buffered Brucella abortus antigen for plaque agglutination test as the basic diagnostic test for bovine brucellosis. Three batches of antigen were formulated from the multiplication of strain 99 of Brucella abortus. Quality controls (determination of pH, cell volume, sterility, buffering capacity) and serological tests for performance evaluation were performed. 1070 bovine serum samples (350 positive and 720 negative) previously tested with the established diagnostic tests were used. Diagnostic and relative sensitivity and specificity, positive predictive values and negative predictive values, efficacy and concordance were determined. In all lots the evaluated characteristics proved to be within the parameters established for this type of product. Diagnostic specificity and sensitivity were 99.5 percent and 100 percent, respectively. The positive predictive values was 99.1 percent, the negative predictive values was 100 percent and the efficacy was 99.7 percent. The antigen showed a relative sensitivity and specificity of 100 percent and the concordance was classified as very good. The performance evaluation showed satisfactory results, demonstrating that the production method used is feasible to obtain a product with adequate efficiency(AU)

Evaluación de un antígeno de Brucella abortus para aglutinación en placa como prueba tamiz en el diagnóstico de la brucelosis bovina / Evaluation of a Brucella abortus antigen for plaque agglutination as screening test in the diagnosis of bovine brucellosis

Este trabajo tuvo como objetivo obtener y validar un antígeno buferado de Brucella abortus para la prueba de aglutinación en placa como prueba diagnóstica de base de la brucelosis bovina. Se formularon tres lotes de antígeno a partir de la multiplicación de la cepa 99 de Brucella abortus. Se realizaron los controles de calidad correspondientes (determinación de pH, volumen celular, esterilidad, capacidad buferante) y las pruebas serológicas para la evaluación del desempeño. Se emplearon 1070 muestras de suero bovino (350 positivas y 720 negativas) previamente controladas con las pruebas de diagnóstico establecidas. Se determinó la sensibilidad y especificidad diagnóstica y relativa, los valores predictivos positivos y negativos, la eficacia y la concordancia. En los tres lotes todas las características evaluadas resultaron estar dentro de los parámetros establecidos para este tipo de producto. La especificidad y sensibilidad diagnósticas fueron de 99,5 por ciento y 100 por ciento respectivamente. El valor predictivo positivo fue de 99,1 por ciento, el valor predictivo negativo fue de 100 por ciento y la eficacia de un 99,7 por ciento. El antígeno mostró una sensibilidad y especificidad relativas de un 100 por ciento y la concordancia resultó ser clasificada como muy buena. La evaluación del desempeño arrojó resultados satisfactorios, demostrando que el método de producción empleado es factible para la obtención de un producto con adecuada eficacia(AU)

The objective of this work was to obtain and validate a buffered Brucella abortus antigen for plaque agglutination test as the basic diagnostic test for bovine brucellosis. Three batches of antigen were formulated from the multiplication of strain 99 of Brucella abortus. Quality controls (determination of pH, cell volume, sterility, buffering capacity) and serological tests for performance evaluation were performed. 1070 bovine serum samples (350 positive and 720 negative) previously tested with the established diagnostic tests were used. Diagnostic and relative sensitivity and specificity, positive predictive values and negative predictive values, efficacy and concordance were determined. In all lots the evaluated characteristics proved to be within the parameters established for this type of product. Diagnostic specificity and sensitivity were 99.5 percent and 100 percent, respectively. The positive predictive values was 99.1 percent, the negative predictive values was 100 percent and the efficacy was 99.7 percent. The antigen showed a relative sensitivity and specificity of 100 percent and the concordance was classified as very good. The performance evaluation showed satisfactory results, demonstrating that the production method used is feasible to obtain a product with adequate efficiency(AU)