Caracterización genotípica y biofilms de E. coli shigatoxigénica aisladas de casos clínicos humanos / Genotypic characterization and biofilms of shigatoxigenic E. coli isolated from human clinical cases

Resumen Escherichia coli shigatoxigénica (STEC) está involucrada en el desarrollo del síndrome urémico hemolítico, entre otras enfermedades que son de gran importancia para la salud pública e inocuidad alimentaria a nivel mundial. La capacidad de STEC de formar biofilms en los alimentos y en diferentes superficies podría conducir a la contaminación cruzada por el desprendimiento de las células bacterianas. El objetivo del presente trabajo fue detectar la presencia de genes que codifican factores de adherencia mediante la técnica de PCR y determinar la capacidad de formación de biofilms por medio de cultivo en microplacas de poliestireno de 96 pocillos y la técnica de cristal violeta, en cepas de STEC aisladas de muestras clínicas humanas en la ciudad de Mar del Plata, Argentina. El perfil de genes de adherencia más frecuente fue efa1, iha, fimCD, ehaA, lpfA1-3, lpfA2-2, cah (43,9%). Todas las cepas de STEC formaron biofilms con valores de densidad óptica entre 0,209 y 3,251 y el 54,4% (31/57) de las mismas fueron clasificadas como fuertes formadoras de biofilms. La capacidad de formación de biofilms de STEC constituye un riesgo evidente en la transmisión de este patógeno al ser humano a tener en cuenta para su vigilancia y control.

Abstract Shigatoxigenic Escherichia coli (STEC) is involved in the development of hemolytic uremic syndrome, among other diseases that are relevant to public health and food safety worldwide. The ability of STEC to form biofilms in food and on different surfaces could lead to cross-contamination by shedding bacterial cells. The aim of this work was to detect the presence of genes encoding adherence factors by the PCR technique and to determine the biofilm formation ability by culture in 96-well polystyrene microplates and the crystal violet technique, in STEC strains isolated from human clinical samples in Mar del Plata city, Argentina. The most frequent adherence gene profile was efa1, iha, fimCD, ehaA, lpfA1-3, lpfA2-2, cah (43.9%). All STEC strains formed biofilms with optical density values between 0.209 and 3.251. Also, the 54.4% (31/57) of STEC strains were classified as strong biofilm formers. The ability of STEC to form biofilms constitutes an evident risk in the transmission of this pathogen to humans, which must be taken into account for its surveillance and control.

Resumo A Escherichia coli shigatoxigênica (STEC) está envolvida no desenvolvimento da síndrome hemolítica urêmica, entre outras doenças relevantes para a saúde pública e segurança alimentar em todo o mundo. A capacidade do STEC de formar biofilmes nos alimentos e em diferentes superfícies poderia levar à contaminação cruzada através do desprendimento de células bacterianas. O objetivo do presente trabalho foi detectar a presença de genes que codificam fatores de aderência através da técnica PCR e determinar a capacidade de formação de biofilme por cultura em microplacas de poliestireno de 96 poços e da técnica de cristal violeta, em cepas STEC isoladas de amostras clínicas humanas na cidade de Mar del Plata, Argentina. O perfil de genes de aderência mais frequente foi efa1, iha, fimCD, ehaA, lpfA1-3, lpfA2-2, cah (43,9%). Todas as cepas de STEC formaram biofilmes com valores de densidade ótica entre 0,209 e 3,251. Também, os 54,4% (31/57) das estirpes STEC foram classificados como fortes formadores de biofilmes. A habilidade de formação de biofilmes de STEC constitui um risco evidente na transmissão deste patógeno ao humano, que deve ser levado em consideração para sua vigilância e controle.

Growth conditions affect biofilms of Staphylococcus aureus producing mastitis: Contribution of MALDI-TOF-MS to strain characterization.

Bovine mastitis is a disease of dairy cattle prevalent throughout the world that causes alterations in the quality and composition of milk, compromising technological performance. Staphylococcus aureus is one of the most important pathogens that produce clinical, subclinical, and chronic mastitis. Biofilms are considered a virulence factor necessary for the survival of S. aureus in the mammary gland. Its zoonotic potential is important not only for the dairy industry sector but also for public health. This study aimed to evaluate the effect of different growing culture conditions on the biofilm formation of S. aureus isolated from mastitis and to test the MALDI-TOF-MS's ability to discriminate among different biofilm formation levels. Fluids commonly found in the dairy environment were incorporated to approach the pathogen's behavior in natural surroundings. PIA production was also evaluated. All strains were able to form high biofilms in TSB, TSBg, and milk. Milk changed the behavior of some strains which formed more biofilms in this medium than in TSBg. The free iron medium CTSBg and milk whey inhibited the biofilm formation of the most strains. MALDI-TOF-MS performance was an excellent tool to discriminate between high, moderate, and low biofilm producers strains of S. aureus in each media, confirming the results of crystal violet assay. PIA production was variable among the strains and showed a media-dependent behavior. Our data highlights the importance of considering the growing conditions that mimic the natural ones to the study of biofilm formation in vitro.