Influência da disponibilidade de ferro em mecanismos de sobrevivência, resistência a agentes antimicrobianos e formação de biofilme de Corynebacterium striatum

Abstract

Corynebacterium striatum has been associated with an increasing number of healthcare- related infections. Virulence attributes such as multi-resistance, ability to adhere to surfaces and build biofilm, can be associated and contribute to bacterial pathogenicity. The bioavailability of micronutrients, such as transition metals, can influence the course of infections through the inhibition/derepression of key metabolic pathways for bacterial persistence. The objective of this work was to evaluate the ability of biofilm formation and the influence of different iron concentrations on sessile and planktonic cells of C. striatum using isolated samples during (August/2009 to April/2010) and after the nosocomial outbreak, at the Hospital University student Pedro Ernesto. Initially, samples BR1987/I, BR2369/II, BR2130/V, BR2237/VI, BR2296/VII, BR2103/VIII and 2425/IX showed a multi-resistance profile while BR1961/III, BR1954/IV and BR2376/X were considered multi sensitive. Under both iron limitation and supplementation, some samples became sensitive to moxifloxacin; others became sensitive to rifampicin; and the BR2376/X sample acquired a multiresistant profile. All tested samples were able to adhere to the polyurethane and glass surface with greater cell viability for BR1987/I; the others did not differ in terms of viable cell count. When submited to iron limitation, some samples suffered total inhibition of adherence to glass, except for BR1961/III, which was reduced, BR1954/IV, which increased its biofilm production, and BR2376/X, which did not change its adhesion profile. Iron supplementation did not change the glass adhesion profile to BR1987/I, BR2130/V, BR2103/VIII and BR2376/X, while BR2369/II and BR1961/III were reduced and BR1954/IV, BR2237/VI, BR2296/VI, BR2425/IX increased biofilm production. Iron limitation produced reduced adhesion and biofilm production on polystyrene for all samples. Under iron supplementation, there was a reduction in adhesion and biofilm production in polystyrene, however, this reduction was only significant for three samples. As for cell viability in the biofilm, BR1987/I had the highest counts. Except for BR1961/III and BR2103/VIII, which were reduced, all analyzed samples had increased viability in biofilms under iron limitation. Under iron supplementation: BR1987/I was not affected, while BR2369/II, BR1954/IV and BR2103/VIII showed an increase and BR1961/III suffered a reduction in viability. Microscopy analysis indicated that there is no difference in the nature of the matrix secreted in the biofilm under any of the conditions tested, the matrix being mostly protein in nature. Microscopy also revealed that iron limitation induced cell elongation in all tested and that this elongation can be reversed when the elongated cells are submitted to growth in medium unaltered in the iron concentration. The results indicate that iron modulates adhesive, morphological and antimicrobial sensitivity properties in C. striatum and emphasize that this pathogen should not be underestimated or discarded as a contaminant by healthcare professionals. Therefore, it is necessary to commit to monitoring and planning for the prevention, control and treatment of infections caused by this corynebacterium