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

GALEANO MARIANA BELEN; SOLAR VENERO ESMERALDA C.; SMANIA ANDREA; PALOMINO MARIA MERCEDES; TRIBELLI PAULA M

Congreso; XVII Congreso Argentino de Microbiología General; 2022

Staphylococcus aureus and Pseudomonas aeruginosa are opportunistic pathogens, which cangenerate co-infections, especially within the context of fibrocystic patients. We analyzed the role ofthe gene encoding hssR, a member of the two-component hssS/hssR regulatory system involved inintracellular heme homeostasis. An in-silico analysis of this gene determined synteny within differentcommensal Staplylococcus strains and interestingly it was absent, in free-living forms strains. Growth rate of the reference strain USA300 vs. hssR in both aerobic and microaerobicconditions 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 ascasein hydrolysis, alpha-hemolysis production, sensitivity to hydrogen peroxide, lipase production,exopolysaccharide production analysis as well as biofilm formation and antibiotic minimuminhibitory concentration (MIC). Of these, alpha-hemolysis production, biofilm production andantibiotic MIC showed significant differences, where hssR showed a lower alpha hemolysinproduction, 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 co-cultures, 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 platecompetition 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.