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

BELEN GALEANO; ESMERALDA VENERO; ANDREA SMANIA; PALOMINO, MARIA MERCEDES; TRIBELLI PAULA

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 Staphylococcusstrains. 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 minimum inhibitoryconcentration (MIC). Of these, alpha-hemolysis production, biofilm production and antibiotic MICshowed significant differences, where hssR showed a lower alpha hemolysin production, biofilmproduction and a lower MIC for ampicillin as well as penicillin G, compared to the USA300 strain.Toanalyze the impact of hemin on growth kinetics, growth curves of the wild type USA300 strain andhssR were performed in presence of pure hemin where an excess of hemin and the inactivation ofhssR 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 PAOin 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 lasRcompetition results were similar. However, we found that the hssR mutant presented higherresistance to P. aeruginosa HexT1 lasR. Our results showed that heme metabolism can impact on theS. aureus-P. aeruginosa interaction.