title: Rhodococcus equi's extreme resistance to hydrogen peroxide is mainly conferred by one of its four catalase genes.
abstract: Rhodococcus equi is one of the most widespread causes of disease in foals aged from 1 to 6 months. R. equi possesses antioxidant defense mechanisms to protect it from reactive oxygen metabolites such as hydrogen peroxide (H(2)O(2)) generated during the respiratory burst of phagocytic cells. These defense mechanisms include enzymes such as catalase, which detoxify hydrogen peroxide. Recently, an analysis of the R. equi 103 genome sequence revealed the presence of four potential catalase genes. We first constructed ΔkatA-, ΔkatB-, ΔkatC-and ΔkatD-deficient mutants to study the ability of R. equi to survive exposure to H(2)O(2)in vitro and within mouse peritoneal macrophages. Results showed that ΔkatA and, to a lesser extent ΔkatC, were affected by 80 mM H(2)O(2). Moreover, katA deletion seems to significantly affect the ability of R. equi to survive within murine macrophages. We finally investigated the expression of the four catalases in response to H(2)O(2) assays with a real time PCR technique. Results showed that katA is overexpressed 367.9 times (± 122.6) in response to exposure to 50 mM of H(2)O(2) added in the stationary phase, and 3.11 times (± 0.59) when treatment was administered in the exponential phase. In untreated bacteria, katB, katC and katD were overexpressed from 4.3 to 17.5 times in the stationary compared to the exponential phase. Taken together, our results show that KatA is the major catalase involved in the extreme H(2)O(2) resistance capability of R. equi.
authors.affiliation: Dozulé Laboratory for Equine Diseases, Unit Bacteriology and Parasitology, ANSES, Goustranville, France.
authors.forename: Pauline
authors.initials: P
authors.lastname: Bidaud
authors.forename: Laurent
authors.initials: L
authors.lastname: Hébert
authors.forename: Corinne
authors.initials: C
authors.lastname: Barbey
authors.forename: Anne-Cécile
authors.initials: AC
authors.lastname: Appourchaux
authors.forename: Riccardo
authors.initials: R
authors.lastname: Torelli
authors.forename: Maurizio
authors.initials: M
authors.lastname: Sanguinetti
authors.forename: Claire
authors.initials: C
authors.lastname: Laugier
authors.forename: Sandrine
authors.initials: S
authors.lastname: Petry
mesh_terms: D000818:Animals; D002374:Catalase / Q000235:genetics*; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D005798:Genes, Bacterial / Q000235:genetics*; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D008264:Macrophages / Q000187:drug effects / Q000382:microbiology; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D050296:Microbial Viability / Q000187:drug effects; D010802:Phylogeny; D016929:Rhodococcus equi / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development
chemical_list: D006861:Hydrogen Peroxide; D002374:Catalase