Variation in endogenous oxidative stress in Escherichia coli natural isolates during growth in urine
1 UMR 722 INSERM and Université Paris Diderot, Sorbonne Paris Cité, Faculté de Médecine, Site Xavier Bichat, Paris, France
2 Laboratoire de Biochimie A, Assistance Publique - Hôpitaux de Paris and Université Paris Sud, Hôpital Bicêtre, Le Kremlin-Bicêtre, France
3 Département d’Anesthésie Réanimation, Assistance Publique - Hôpitaux de Paris and Université Paris Sud, Hôpital Bicêtre, Le Kremlin-Bicêtre, France
4 Laboratoire de Biochimie, Assistance Publique - Hôpitaux de Paris and Université Paris Descartes, Hôpital Cochin, Paris, France
5 Institute for Hygiene, University of Münster, Münster, Germany
6 Bioquanta, Mitoxis, France
7 Université Paris-Est, INSERM U955 EQ07, Créteil, France
BMC Microbiology 2012, 12:120 doi:10.1186/1471-2180-12-120Published: 22 June 2012
Uropathogenic strains of Escherichia coli cause symptomatic infections whereas asymptomatic bacteriuria (ABU) strains are well adapted for growth in the human urinary tract, where they establish long-term bacteriuria. Human urine is a very complex growth medium that could be perceived by certain bacteria as a stressful environment. To investigate a possible imbalance between endogenous oxidative response and antioxidant mechanisms, lipid oxidative damage estimated as thiobarbituric acid reactive substances (TBARS) content was evaluated in twenty-one E. coli belonging to various pathovars and phylogenetic groups. Antioxidant defense mechanisms were also analysed.
During exponential growth in urine, TBARS level differs between strains, without correlation with the ability to grow in urine which was similarly limited for commensal, ABU and uropathogenic strains. In addition, no correlation between TBARS level and the phylogroup or pathogenic group is apparent. The growth of ABU strain 83972 was associated with a high level of TBARS and more active antioxidant defenses that reduce the imbalance.
Our results indicate that growth capacity in urine is not a property of ABU strains. However, E. coli isolates respond very differently to this stressful environment. In strain ABU 83972, on one hand, the increased level of endogenous reactive oxygen species may be responsible for adaptive mutations. On the other hand, a more active antioxidant defense system could increase the capacity to colonize the bladder.