LIGHT MODULATES GENE EXPRESSION OF COMPONENTS OF THE EFFLUX PUMP AdeIJK IN Acinetobacter baumanii

MÜLLER G.L.; GOLIC A.E.; RAMÍREZ M.S.; MUSSI M. A.

Córdoba

Congreso; XI Congreso Argentino de Microlbiología General - SAMiGE; 2015

SAMIGE

We have recently showed that light modulates A. baumannii susceptibility to antibiotics clinically relevant such as minocycline (MIN) and tigecycline (TIG), which represent important weapons against multidrug resistant (MDR) bacteria. Beyond resistance to antibiotics, the response to light might enhance bacterial persistence until more favorable conditions or additional resistance determinants are accumulated. The magnitude of the phenotype was found to depend on the culture media, being maximal in Luria Bertani (LB) Difco, reduced in the presence of iron and null in Müeller Hinton (MH) media. Also, the phenomena was found to be temperature dependent, as it occurs at 24ºC but reduced at 37ºC.The generation of 1O2 results in the same phenotype as the application of blue light, i.e. reduced susceptibility to MIN and TIG, providing strong evidence that light might exert its effects through 1O2 production. In addition, we showed that light, as well as 1O2, induce the expression of genes previously related to resistance to TIG, such as those coding for the efflux pump AdeABC.The objective of this work is to study the effect of light in the expression of genes coding for the efflux pump AdeIJK, which was previously shown to act synergistically with AdeABC confering resistance to TIG.Our results show that in cells grown in LB plates incubated overnight at 24ºC, as well as in cells grown to exponential phase in liquid LB media, specific gene components of the AdeIJK efflux system are induced under blue light respect to dark conditions. As control, no differences in the levels of AdeIJK transcripts were detected between light and dark conditions in MH, a condition in which no differences in resistance to MIN or TIG were observed between light and dark. The overall results show that adeIJK genes are modulated by light, reinforcing the notion of a correlation between reduction in susceptibility to TIG and induction of efflux pump resistance genes by light, and also suggesting that the efflux pump AdeIJK might act synergistically to AdeABC.