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Infect. Immun., Jul 1997, 2700-2706, Vol 65, No. 7
RA D'Mello, PR Langford and JS Kroll
Haemophilus influenzae type b, a causative agent of bacterial sepsis and
meningitis in young children, contains a single superoxide dismutase (SOD),
a cytoplasmic MnSOD. To study the role of this enzyme, a chromosomal
sodA::lacZ mutant (M-2) was constructed. M-2 had an increased sensitivity
towards oxygen and the redox-active agent paraquat. A 3.4-fold increase in
sodA-lacZ expression was found in M-2 grown with oxygen supply rates
between 3 and 36 mmol of O2/liter/h. In similar experiments with the wild
type, assaying SodA activity, a 3.1- fold increase was found. Both the wild
type and M-2 grew best at the lowest oxygen supply rate tested, consistent
with the notion that H. influenzae prefers a more anaerobic environment. In
the infant rat model of infection, the ability of M-2 to colonize the
nasopharynx was found to be impaired, but its ability to cause invasive
disease was unaffected. This suggests that after invasion, the growth
disadvantage imposed by a SodA- phenotype is not limiting.
Copyright © 1997, American Society for Microbiology
Role of bacterial Mn-cofactored superoxide dismutase in oxidative stress responses, nasopharyngeal colonization, and sustained bacteremia caused by Haemophilus influenzae type b
Department of Paediatrics, Imperial College School of Medicine at St. Mary's Hospital, London, United Kingdom.
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