Coexistence withPseudomonas aeruginosaaltersStaphylococcus aureustranscriptome, antibiotic resistance and internalization into epithelial cells

Abstract

15Cystic fibrosis (CF) is the most common life-threatening genetic disease among Caucasians. CF 16 patients suffer from chronic lung infections due to the presence of thick mucus, caused by cftr 17 gene dysfunction. The two most commonly found bacteria in the mucus of CF patients are 18Staphylococcus aureus and Pseudomonas aeruginosa. It is well known that early-infecting P. 19 aeruginosa strains produce anti-staphylococcal compounds and inhibit S. aureus growth. More 20 recently, it has been shown that late-infecting P. aeruginosa strains develop commensal-21 like/coexistence interaction with S. aureus. The aim of this study was to decipher the impact of P. 22While P. aeruginosa is recognized as the leading cause of lung function decline, the significance 49 of S. aureus in the course of CF disease is still being debated. It has been shown that one of the 50 risk factors for initial P. aeruginosa airway infection includes S. aureus pre-colonization [8][9][10] . 51However, the impact of coinfection by the two pathogens on the evolution of the disease remains 52 unclear 11-13 . 53 S. aureus and P. aeruginosa have been identified in the same lobe of CF lungs 14,15 , suggesting 54 that both pathogens are present in the same niche and can in fact interact in vivo. Interactions 55 4 have been widely studied and it is commonly admitted that P. aeruginosa outcompetes S. aureus. 56 Different mechanisms have been described 16 : for example, P. aeruginosa secreted products can 57 inhibit the growth or lyse S. aureus as well as induce epithelial cells to kill S. aureus and other 58Gram-positive bacteria 8,17,18 . 59 However, these interactions can evolve during chronic colonization. Indeed, P. aeruginosa strains 60 isolated from early infection outcompete S. aureus, as previously described, while strains isolated 61 from chronic infection are less aggressive and can be co-cultivated with S. aureus 19,20 . 62 Furthermore, P. aeruginosa isolates from mono-infected patients are more competitive towards S. 63 aureus than isolates from coinfected patients 21 . 64 In contrast to antagonistic interactions, nothing is known about the effects of P. aeruginosa and 65 S. aureus interactions in this context of coexisting bacteria within the same infectious niche. 66Using a transcriptomic approach, we analyzed how co-cultivation with non-competitive P. 67 aeruginosa altered S. aureus gene expression, especially genes encoding Nor family efflux 68 pumps. In the presence of P. aeruginosa, over-expression of these genes increased S. aureus 69 antibiotic tolerance and the rate of internalization into epithelial cells, two key determinants of 70 chronic infection. 71 72 5 RESULTS 73Coexistence interaction involves more than half of the S. aureus and P. aeruginosa isolates 74 from co-infected CF patients. 75Two types of interactions between S. aureus and P. aeruginosa could be observed with CF 76 patient isolates: the well-described competitive phenotype, where P. aeruginosa inhibits S. 77 aureus growth, 16 and the newly describe...

Characterisation of key genotypic and phenotypic traits of clinical cystic fibrosisStaphylococcus aureusisolates

“…Additionally, a higher percentage of coinfection strains showed resistance to ciprofloxacin, an antibiotic commonly used with CF patients, compared to monoinfection strains (6, 42.8% vs 2, 18.1%), non-significant using Fisher's exact test (p=0.2337). This is in line with previous studies showing that antibiotic pumps for ciprofloxacin are upregulated when S. aureus grows in coexistence with P. aeruginosa (61). Six coinfection isolates exhibited induced clindamycin resistance; this was established using the D-test, no monoinfection isolates presented induced clindamycin resistance, non-significant using Fisher's exact test (p = 0.1804).…”

“…It is being increasingly recognised that polymicrobial infections contribute to increased drug resistance of individual species (59). Previous work has identified modified drug resistance profiles in co-existing S. aureus and P. aeruginosa strains due to higher drug efflux pump activity and altered biofilm formation (60,61). Therefore, to determine whether S. aureus strains isolated from P. aeruginosa coinfection presented increased antibiotic resistance, the resistance phenotypes of the S. aureus only and S. aureus/P.…”

Trophic cooperation promotes bacterial survival of Staphylococcus aureus and Pseudomonas aeruginosa

“…Coinfection with S. aureus and P. aeruginosa is a frequent situation, especially in the lungs of CF patients, where coinfection accounts for 25% to 50% of cases (17)(18)(19). In this context of coinfection, two states of interaction between the two pathogens have been described: the well-known competitive interaction where P. aeruginosa is able to inhibit the growth of S. aureus and the coexistence state where the growth of both species is not affected by either individual species.…”

“…Briaud et al recently demonstrated that this interaction pattern appears to be more frequent than expected. Indeed, among the quarter of CF patients co-infected by both pathogens, 65% were infected by a coexisting S. aureus-P. aeruginosa pair (18,19). Recent studies have shown that coexistence between P. aeruginosa and S. aureus could promote their persistence throughout the establishment of cooperative interaction.…”