INSIGHT TO NEW GENES INVOLVED IN Staphylococcus aureus AND Pseudomonas aeruginosa INTERACTION

BELEN GALEANO; SOLAR VENERO; ANDREA SMANIA; MARÍA MERCEDES PALOMINO; TRIBELLI PAULA

Buenos Aires

Congreso; SAIB - SAMIGE Joint meeting 2021 on line; 2021

SAIB-SAMIGE

Staphylococcus aureus and Pseudomonas aeruginosa are bacterial species that provoke infections in patients with chronicdiseases, after surgery or long-term catheter usage. Bacteria can form communities and co-infections and lead to worse patientprognosis. In general terms the interaction between these species is thought to be antagonist but in vivo studies suggest it is afar more complex. Mutations were described in both species during individual infections, but no study analyzed the effectduring co-infections. Our hypothesis is that there are mutations in S. aureus that can modify the interaction with P. aeruginosa.To detect new genes involved in S. aureus - P. aeruginosa interaction we use the Nebraska Library that comprises an orderedcollection of S. aureus mutant clones with a transposon (Tn) interrupting non-essential genes and P. aeruginosa PAO1 with afluorescent protein under a constitutive promoter. We performed a 2000 clones from the Nebraska Library screening to detectmodifications in P. aeruginosa PAO1 growth when was co-culture with the wild type S. aureus USA300 strain or the mutantclones. Our results showed S. aureus clones that presented an altered interaction with P. aeruginosa were mutated in genesinvolved in envelope biosynthesis, iron and energy metabolisms, adhesion and biofilm formation and hypothetical proteins.Among them, we studied the survival of S. aureus lrgA and uppP mutant strains, both genes related with envelope biosynthesisand its modifications. We showed 5 times decrease in survival of lrgA strain in co-cultures of 24 hours when P. aeruginosawas present in comparison with the USA300 under aerobic conditions but interestingly a 2-times increase of survival underlow oxygen conditions. Survival of uppP also showed differences depending on oxygen availability, while under aerobicconditions survival was 10 times lower in comparison with the wild type strain at microaerobiosis the survival was similarbetween both strains. Competition plate assays were performed using P. aeruginosa strains PAO1 wild type and its mucA22mutant as well as P. aeruginosa HexT1 and its lasR mutant strain. We did not find significant differences among the differentstrains except for mucA22 that presented higher competence behavior against the S. aureus upp mutant strain in comparisonwith USA300 wild type. A bioinformatic analysis of uppP gene was conserved among different S. aureus strains and aphylogenetic analysis using MEGA software showed a clustering similar to that observed for the rRNA gene. On the contrary,for lrgA analysis we observed that while 16S coding gene from S. aureus form a cluster with other human commensal Staphylococci species (such as S. capiatis and S. epidermidis), lrgA sequence form a cluster with other pathogenic Stphylococcilike S. feli (produces infections in cats), S. intermedius and S. pseudointermedius (cause infection in dogs) and S. delphini(causes infections in horses among other animals), suggesting a role in virulence. We will focus on these genes in future invitro and in vivo interaction experiments.