2008, Number 3
Rev Biomed 2008; 19 (3)
Damage and response to oxidative stress in anaerobic bacteria of the genus Bacteroides: antimicrobial resistance and virulence factors
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ABSTRACTSome bacterial species such as Escherichia coli have tolerance features against oxygen reactive substance (ROS). One of the main products from oxidative damage to the DNA molecule in in vivo and in vitro is the 8-hydroxydeoxyguanosine (8OHdG), which could be used as a biological marker as result of such effect. The exposure of Prevotella to H2O2 in an atmosphere free of oxygen results in high levels of 8OHdG with a surviving rate of less than 1.0 %.
In anaerobic bacteria of clinical importance, mainly in those of the genus Bacteroides it has been observed that an increasing of the 8OHdG correlates with a lower surviving rate. Some of the responses to oxidative stress have been found in B. fragilis and the genes involved in ROS detoxification mechanism and DNA repair are katB (catalase), sod (superoxide dismutase), ahpCF (alquil-hydroperoxide reductase) and dps (DNA unspecific binding proteins).
In B. thetaiotaomicron recA- the sensitivity to oxygen is higher as compared with the wild type strain. It also shows higher resistance to metronidazol, one of the first choice antimicrobial used against anaerobic bacterial infections.
The oxidative stress has a negative effect on Bacteroides growth, however a group of genes known as oxidative stress response (OSR) allow this bacterial genus a significant aerotolerance, therefore, higher virulence ability as to cause infection in humans.
In this review, the mechanisms against the oxidative damage in the anaerobic bacterium Bacteroides are summarized. In addition, the protection events mentioned above are correlated with virulence of this anaerobe in human infections and with a possible relation with resistance to antimicrobials such as the metronidazol.