ROLE OF THE hssR GENE IN THE INTERACTION BETWEEN Staphylococcus aureus AND Pseudomonas aeruginosa

Los Cocos

Congreso; XVII Congreso Argentino de Microbiología General; 2022

SAMIGE

Staphylococcus aureus and Pseudomonas aeruginosa are opportunistic pathogens, which can generate co-infections, especially within the context of fibrocystic patients. We analyzed the role of the gene encoding hssR, a member of the two-component hssS/hssR regulatory system involved in intracellular heme homeostasis. An in-silico analysis of this gene determined synteny within different commensal Staplylococcus strains and interestingly it was absent, in free-living forms Staphylococcus strains. Growth rate of the reference strain USA300 vs. hssR in both aerobic and microaerobic conditions was similar between both strains suggesting that hssR mutation did not alter growth.Subsequently, we performed different phenotypic assays to characterize the mutant clone such as casein hydrolysis, alpha-hemolysis production, sensitivity to hydrogen peroxide, lipase production, exopolysaccharide production analysis as well as biofilm formation and antibiotic minimum inhibitory concentration (MIC). Of these, alpha-hemolysis production, biofilm production and antibiotic MIC showed significant differences, where hssR showed a lower alpha hemolysin production, biofilm production and a lower MIC for ampicillin as well as penicillin G, compared to the USA300 strain. To analyze the impact of hemin on growth kinetics, growth curves of the wild type USA300 strain and hssR were performed in presence of pure hemin where an excess of hemin and the inactivation of hssR produce a decrease in the growth of S. aureus. Regarding the behavior of hssR strain in cocultures, we found no significant differences in the growth of hssR and USA300 in the presence of PAO in liquid cultures under aerobic conditions. -When we performed plate competition for wild-type P.aeruginosa PAO1 and its mutant mucA22, as well as P. aeruginosa HexT1 and its mutant strain lasR competition results were similar. However, we found that the hssR mutant presented higher resistance to P. aeruginosa HexT1 lasR. Our results showed that heme metabolism can impact on the S. aureus-P. aeruginosa interaction