Phenotypic characters of urinary isolates of Pseudomonas aeruginosa & their association with mouse renal colonization.

BACKGROUND & OBJECTIVE: Very few studies regarding production of virulence factors in different predominant serotypes of uropathogenic Pseudomonas aeruginosa are available and they have not been correlated to in vivo pathogenicity in the urinary tract. This study was carriedout with the objective to analyze the phenotypic characters of uroisolates of P. aeruginosa in vitro and to study the association of these virulence traits with their ability to cause nephropathogenicity in mouse model of ascending urinary tract infection (UTI). METHODS: Protease, elastase, alginate, haemolysin, pyochelin, pyoverdin and phopholipase C were measured using standard protocols in 18 uroisolates of P. aeruginosa isolated from patients suffering from complicated UTIs. An ascending model of pyelonephritis was established in Swiss Webster (LACA) female mice with these isolates. Quantitative bacterial count and histopathological evaluation of mouse renal tissue was done which were then assessed for a possible association with elaboration of virulence factors. RESULTS: All isolates of P. aeruginosa were able to colonize renal tissue of mice. However, renal counts varied amongst different isolates producing different virulence factors. Isolates producing high levels of haemolysin along with other virulence factors were able to colonize and multiply more in mouse renal tissue as compared to those producing low levels of haemolysin. INTERPRETATION & CONCLUSION: The findings of this study indicated an association between haemolysin production and renal colonization. High level of haemolysin production in vitro could be used as surrogate information for assessing pyelonephritic potential of P. aeruginosa.

Detection of extracellular proteases from microorganisms on agar plates

We present herein an improved assay for detecting the presence of extracellular proteases from microorganisms on agar plates. Using different substrates (gelatin, BSA, hemoglobin) incorporated into the agar and varying the culture medium composition, we were able to detect proteolytic activities from Pseudomonas aeruginosa, Micrococcus luteus and Serratia marcescens as well as the influence that components displayed in the expression of these enzymes. For all microorganisms tested we found that in agar-BHI or yeast extract medium containing gelatin the sensitivity od proteinase detection was considerably greater than in BSA-agar or hemoglobin-agar. However, when BSA or hemoglobin were added to the culture medium, there was an increase in growth along with a marked reduction in the amount of proteinase production. In the case of M. luteus the incorporation of glycerol in BHI or yeast extract gelatin-agar induced proyease liberation. Our results that the technique described here is of value for detecting extracellular proteases directly in the culture medium, by means of a qualitative assay, simple, inexpensive, straight forward method to assess the presence of the proteolytic activity of a given microorganism colony with great freedom in substrate selection.

La fibronectina y la adherencia de microorganismos patógenos / Fibronectin and the adherence of pathogenic microorganisms

La fibronectina (Fn) es uno de los principales componentes de la superficie celular, las matrices extracelulares y el plasma. La constituyen un dímero con dos cadenas polipeptícas de 250 kDa. Su estructura primaria está formada con base en unidades de repetición, originando los dominios de unión a diversas moléculas. La integrina Ó ß participa como el principal receptor celular de Fn. La fibronictina participa en procesos inmunológicos de fagocitosis, inflamación y opsonización, favoreciendo la depuración de bacterias y retos celulares. Juega un papel relevante en la cicatrización durante la hemostásis. En la superficie celular puede unirse a diferentes microorganismos, favoreciendo su colonización, siendo la primera etapa en la epatogénesis de diversas enfermedades infecciosas. En Staphylococcus aureus la proteína FnBp une al fragmento de 29 kDa de amino terminal de la Fn, sitio comparativo por Streptococcus pyogenes donde la proteína Sfb parece ser el ligando de la bacteria y no el ácido lipoteicóico (ALT). La Fn favorece la adherencia de bacterias gram positivas, su ausencia en la otofaringe favorece la colonización de bacterias gram negativas. Especies bacterianas de la cavidad orofaringea provocan la proteólisis de Fn y pueden participar indirectamente en la regulación de la flora cuando afectan los niveles de Fn en las superficies celulares. Treponema pallidum se une al sitio de reconocimiento celular de la Fn mediante una proteína semejante a la integrina (B 1) Entamoeba histolytica y schistosoma provocan una degradación de la Fn para poder invadir los tejidos epiteliales. Los parásitos intracelulares como Leishmania y Trypanosoma cruzi se adhieren a la Fn, utilizándola para facilitar su entrada a las células que infectan. La Fn puede unir virus y partículas virales favoreciendo la acción depuradora en este tipo de infecciones. Su amplia distribución en el organismo y su multifunsionalidad la hacen ser una proteína determinante en los procesos homeostásicos y de gran interés como un determinante en colonización e infección