Acute ileitis facilitates infection with multidrug resistant Pseudomonas aeruginosa in human microbiota-associated mice

Abstract

BackgroundThe rising incidence of multidrug resistant (MDR) Gram-negative bacteria including Pseudomonas aeruginosa has become a serious issue in prevention of its spread particularly among hospitalized patients. It is, however, unclear whether distinct conditions such as acute intestinal inflammation facilitate P. aeruginosa infection of vertebrate hosts.Methods and resultsTo address this, we analysed P. aeruginosa infection in human microbiota-associated (hma) mice with acute ileitis induced by peroral Toxoplasma gondii challenge. When perorally infected with P. aeruginosa at day 3 post ileitis induction, hma mice displayed higher intestinal P. aeruginosa loads as compared to hma mice without ileitis. However, the overall intestinal microbiota composition was not disturbed by P. aeruginosa (except for lowered bifidobacterial populations), and the infection did not further enhance ileal immune cell responses. Pro-inflammatory cytokines including IFN-γ and IL-12p70 were similarly increased in ileum and mesenteric lymph nodes of P. aeruginosa infected and uninfected hma mice with ileitis. The anti-inflammatory cytokine IL-10 increased multifold upon ileitis induction, but interestingly more distinctly in P. aeruginosa infected as compared to uninfected controls. Immune responses were not restricted to the intestines as indicated by elevated pro-inflammatory cytokine levels in liver and kidney upon ileitis induction. However, except for hepatic TNF-α levels, P. aeruginosa infection did not result in more distinct pro-inflammatory cytokine secretion in liver and kidney of hma mice with ileitis. Whereas viable intestinal bacteria were more frequently detected in systemic compartments such as spleen and cardiac blood of P. aeruginosa infected than uninfected mice at day 7 following ileitis induction, P. aeruginosa infection did not exacerbate systemic pro-inflammatory sequelae, but resulted in lower IL-10 serum levels.ConclusionAcute intestinal inflammation facilitates infection of the vertebrate host with MDR bacteria including P. aeruginosa and might also pose particularly hospitalized patients at risk for acquisition. Since acute T. gondii induced inflammation might mask immunopathology caused by P. aeruginosa, a subacute or chronic inflammation model might be better suited to investigate the potential role of P. aeruginosa infection in the aggravation of intestinal disease.Electronic supplementary materialThe online version of this article (doi:10.1186/s13099-017-0154-4) contains supplementary material, which is available to authorized users.

Toll-like receptor-4 dependent inflammatory responses following intestinal colonization of secondary abiotic IL10-deficient mice with multidrug-resistant Pseudomonas aeruginosa

“…The MDR P. aeruginosa isolate was initially isolated from respiratory material of a patient with nosocomial pneumonia and kindly provided by Prof. Dr. Bastian Opitz (Charité – University Medicine Berlin, Berlin, Germany). Notably, the bacterial strain exhibited exclusive antimicrobial sensitivity to fosfomycin and colistin [ 22 ]. Before peroral challenge, the P. aeruginosa isolate was grown on Cetrimide agar (Oxoid) for 48 h in an aerobic atmosphere at 37 °C.…”

Multidrug-resistant Pseudomonas aeruginosa induce systemic pro-inflammatory immune responses in colonized mice

“…Whereas the pathogenic potential of P. aeruginosa is well known, its potential in initiation and perpetuation of immunopathologies, particularly within the intestinal tract, is only incompletely understood. In a very recent study, we were able to show that acute ileitis facilitated infection with MDR P. aeruginosa in mice harboring a human gut microbiota, but the inflammation model was too acute to decipher additional inflammatory sequelae induced by the MDR bacterial strain [ 17 ].…”

“…The MDR P. aeruginosa isolate was initially cultured from respiratory material of a patient with nosocomial pneumonia and kindly provided by Prof. Dr. Bastian Opitz (Charité – University Medicine Berlin, Berlin, Germany). Notably, the bacterial strain displayed antimicrobial sensitivity to fosfomycin and colistin only [ 17 ].…”

“…On two consecutive days (i.e., days 0 and 1), mice were perorally challenged either with 10 9 colony forming units (CFU) of the MDR P. aeruginosa or the commensal E. coli strain by gavage in a total volume of 0.3 ml PBS as reported earlier [ 14 , 17 , 18 ].…”

“…Fecal samples were homogenized in sterile PBS. Serial dilutions were then streaked onto Columbia agar supplemented with 5% sheep blood (Oxoid, Germany) and cetrimid or MacConkey agar and incubated in an aerobic atmosphere at 37 °C for 48 and 24 h in order to assess intestinal P. aeruginosa and E. coli loads, respectively, as described previously [ 14 , 17 , 18 ].…”