Sepsis-trained macrophages promote antitumoral tissue-resident T cells.

Sepsis induces immune alterations, which last for months after the resolution of illness. The effect of this immunological reprogramming on the risk of developing cancer is unclear. Here we use a national claims database to show that sepsis survivors had a lower cumulative incidence of cancers than matched nonsevere infection survivors. We identify a chemokine network released from sepsis-trained resident macrophages that triggers tissue residency of T cells via CCR2 and CXCR6 stimulations as the immune mechanism responsible for this decreased risk of de novo tumor development after sepsis cure. While nonseptic inflammation does not provoke this network, laminarin injection could therapeutically reproduce the protective sepsis effect. This chemokine network and CXCR6 tissue-resident T cell accumulation were detected in humans with sepsis and were associated with prolonged survival in humans with cancer. These findings identify a therapeutically relevant antitumor consequence of sepsis-induced trained immunity.

Regulatory T Cells Expressing Tumor Necrosis Factor Receptor Type 2 Play a Major Role in CD4+ T-Cell Impairment During Sepsis.

Sepsis causes inflammation-induced immunosuppression with lymphopenia and alterations of CD4+ T-cell functions that renders the host prone to secondary infections. Whether and how regulatory T cells (Treg) are involved in this postseptic immunosuppression is unknown. We observed in vivo that early activation of Treg during Staphylococcus aureus sepsis induces CD4+ T-cell impairment and increases susceptibility to secondary pneumonia. The tumor necrosis factor receptor 2 positive (TNFR2pos) Treg subset endorsed the majority of effector immunosuppressive functions, and TNRF2 was particularly associated with activation of genes involved in cell cycle and replication in Treg, probably explaining their maintenance. Blocking or deleting TNFR2 during sepsis decreased the susceptibility to secondary infection. In humans, our data paralleled those in mice; the expression of CTLA-4 was dramatically increased in TNFR2pos Treg after culture in vitro with S. aureus. Our findings describe in vivo mechanisms underlying sepsis-induced immunosuppression and identify TNFR2pos Treg as targets for therapeutic intervention.

Live intramacrophagic Staphylococcus aureus as a potential cause of antibiotic therapy failure: observations in an in vivo mouse model of prosthetic vascular material infections.

Objectives: To evaluate the significant role played by biofilms during prosthetic vascular material infections (PVMIs). Methods: We developed an in vivo mouse model of Staphylococcus aureus PVMI allowing its direct observation by confocal microscopy to describe: (i) the structure of biofilms developed on Dacron® vascular material; (ii) the localization and effect of antibiotics on these biostructures; and (iii) the interaction between bacteria and host tissues and cells during PVMI. Results: In this model we demonstrated that the biofilm structures are correlated to the activity of antibiotics. Furthermore, live S. aureus bacteria were visualized inside the macrophages present at the biofilm sites, which is significant as antibiotics do not penetrate these immune cells. Conclusions: This intracellular situation may explain the limited effect of antibiotics and also why PVMIs can relapse after antibiotic therapy.

Efficacy of ceftolozane in a murine model of Pseudomonas aeruginosa acute pneumonia: in vivo antimicrobial activity and impact on host inflammatory response.

OBJECTIVES: To assess the activity of ceftolozane, a novel oxyimino-cephalosporin, in comparison with ceftazidime and piperacillin/tazobactam against a multidrug-resistant Pseudomonas aeruginosa strain using a murine model of pneumonia. METHODS: Quantitative bacteriology, survival, histological examination, myeloperoxidase activity, proinflammatory cytokine levels in lungs and endothelial permeability were evaluated to determine the effects of ceftolozane and comparators on P. aeruginosa-induced pneumonia. RESULTS: After 48 h of treatment, ceftolozane reduced the bacterial load by 3-4 log(10) cfu/g of lung. Systemic dissemination of the pulmonary infection and development of lung damage were inhibited in all ß-lactam-treated animals. P. aeruginosa-induced pneumonia led to elevated concentrations of tumour necrosis factor-α, interleukin (IL)-1ß and macrophage inflammatory protein (MIP)-2 in the lungs. While the levels of proinflammatory cytokines decreased following ceftazidime and piperacillin/tazobactam therapy, ceftolozane exhibited increased concentrations of IL-1ß and MIP-2 after 24 h of infection, resulted in significantly increased levels of recruited neutrophils within the infected lung without increasing lung endothelial permeability. CONCLUSIONS: These data strongly support ceftolozane as an effective option for the treatment of severe P. aeruginosa respiratory infections by improving the early pulmonary inflammatory response without impairing 48 h post-infection homeostasis.

Comparison of ceftaroline fosamil, daptomycin and tigecycline in an experimental rabbit endocarditis model caused by methicillin-susceptible, methicillin-resistant and glycopeptide-intermediate Staphylococcus aureus.

OBJECTIVES: The aim of this study was to compare the in vivo activities of the new antistaphylococcal drugs ceftaroline fosamil, daptomycin and tigecycline at projected human therapeutic doses against methicillin-susceptible Staphylococcus aureus (MSSA), methicillin-resistant S. aureus (MRSA) and glycopeptide-intermediate S. aureus (GISA) strains in a rabbit model of endocarditis. METHODS: The efficacy of therapeutic regimens in our model was evaluated following 4 days of treatment by determining colony counts of infected vegetations. Emergence of resistant variants during therapy was assessed. RESULTS: Using this model of infective endocarditis, ceftaroline fosamil and daptomycin demonstrated high bactericidal in vivo activity (reduction of >5 log(10) cfu/g of vegetation) after a 4 day treatment against MSSA, MRSA and GISA strains. Both drugs were more efficacious than tigecycline, which showed moderate activity but failed to exhibit a bactericidal effect. Ceftaroline was superior to daptomycin in terms of sterilization of the vegetations. Emergence of resistant variants during daptomycin therapy was observed in two animals (one in the MSSA group and one in the MRSA group) but was not observed in ceftaroline- or tigecycline-treated animals. CONCLUSIONS: The novel ß-lactam agent ceftaroline fosamil was the most active bactericidal drug in this model and is a promising therapeutic option for the treatment of severe S. aureus infections, including those caused by MRSA and GISA strains.

Efficacy of doripenem in the treatment of Pseudomonas aeruginosa experimental pneumonia versus imipenem and meropenem.

OBJECTIVES: The aim of this study was to compare doripenem with imipenem and meropenem in an experimental rabbit model of Pseudomonas aeruginosa pneumonia and then to compare different doripenem doses and methods of intravenous administration. METHODS: Using a rabbit experimental model of pneumonia, efficacy was assessed following 2 days of treatment by colony counts of different tissues (lung, spleen and blood culture). RESULTS: Mean pulmonary bacterial loads were 3.17 ± 0.53, 3.42 ± 0.61 and 2.75 ± 0.59 log(10) cfu/g for imipenem, doripenem (0.5 g three times daily) and meropenem, respectively, compared with 7.57 ± 0.99 cfu/g for control animals. At a higher dose (1 g three times daily), doripenem showed significantly better efficacy (2.70 ± 0.65 log(10) cfu/g) than the standard regimen of doripenem. Sterilization of spleen cultures was achieved with standard regimens of imipenem (1 g three times daily) and a higher dose of doripenem. CONCLUSIONS: In this model of P. aeruginosa pneumonia, doripenem had an efficacy equivalent to that of meropenem and imipenem at a high dose of 1 g three times a day and lower efficacy at a standard dose (0.5 g three times daily) than the other two agents in terms of bacteria cultivated from spleens. Doripenem is a new drug that offers new therapeutic options, especially for difficult-to-treat infections such as pneumonia due to non-fermenting Gram-negative bacteria.

Efficacy of the new cephalosporin ceftaroline in the treatment of experimental methicillin-resistant Staphylococcus aureus acute osteomyelitis.

OBJECTIVES: To evaluate the activity of a new cephalosporin, ceftaroline, in comparison with other antistaphylococcal drugs (linezolid and vancomycin) at projected human therapeutic doses against methicillin-resistant Staphylococcus aureus (MRSA) and glycopeptide-intermediate S. aureus (GISA) strains. METHODS: Using a rabbit experimental model of acute osteomyelitis, efficacy was assessed following 4 days of treatment by colony counts of infected bone tissues (joint fluid, femoral bone marrow and bone). RESULTS: Although vancomycin remains the standard treatment for MRSA osteomyelitis, it was ineffective against the MRSA strain and poorly active against GISA infections in this model. Ceftaroline and linezolid demonstrated significant activity in bone marrow and bone, and were significantly better than vancomycin treatment. However, ceftaroline was the only drug to exhibit significant activity against MRSA in infected joint fluid. CONCLUSIONS: The present study supports ceftaroline as a promising therapeutic option for the treatment of severe MRSA infections, including osteomyelitis.

In vivo activity of a novel anti-methicillin-resistant Staphylococcus aureus cephalosporin, ceftaroline, against vancomycin-susceptible and -resistant Enterococcus faecalis strains in a rabbit endocarditis model: a comparative study with linezolid and vancomycin.

We assessed the in vitro and in vivo efficacy of the novel parenteral broad-spectrum cephalosporin ceftaroline against Enterococcus faecalis in time-kill experiments and in a rabbit endocarditis model with simulated human dosing. Ceftaroline was more active than either vancomycin or linezolid against vancomycin-sensitive and -resistant isolates of E. faecalis.

In vivo efficacy of linezolid in combination with gentamicin for the treatment of experimental endocarditis due to methicillin-resistant Staphylococcus aureus.

Indifference or even antagonism has mainly been reported with combinations including linezolid. The presence of in vitro antagonism is not always correlated with in vivo failure. The purpose of this study was to evaluate the in vivo activity of linezolid combined with gentamicin using a methicillin-resistant Staphylococcus aureus (MRSA) endocarditis experimental model. A human-like pharmacokinetic simulation was used for linezolid and gentamicin to improve the extrapolation of the results to human therapy. Contrary to the antagonism previously described in vitro, linezolid combined with gentamicin exhibited bactericidal activity on the two strains with a decrease of at least 4 log(10)cfu/g of vegetation compared with controls. These data suggest that linezolid plus gentamicin could be an appropriate combination for the treatment of severe MRSA infections.

In vivo impact of the MexAB-OprM efflux system on beta-lactam efficacy in an experimental model of Pseudomonas aeruginosa infection.

In this study, the in vivo impact of the MexAB-OprM efflux system on antipseudomonal beta-lactam efficacy was investigated. The respective activities of human simulated regimens of ticarcillin (TIC), piperacillin/tazobactam (PIP/TAZ) and ceftazidime (CFZ) on two isogenic mutants of Pseudomonas aeruginosa PAO1, namely PAO4098E overexpressing MexAB-OprM and PAO4098ET which is OprM-depleted, were evaluated in an experimental rabbit endocarditis model. The following human daily doses by intermittent administration or continuous infusion were simulated: 15 g and 18 g for TIC; 12 g and 16 g for PIP/TAZ; and 3g and 6g for CFZ. TIC, PIP/TAZ and CFZ exhibited minimum inhibitory concentrations of 64, 8 and 2 microg/mL, respectively, against PAO4098E and 0.5, 0.5 and 1 microg/mL against PAO4098ET. Against PAO4098E, only the high-dose regimens of CFZ were effective, with the most significant effect being achieved by continuous infusion. In contrast, all the tested regimens were effective against PAO4098ET. In the most difficult-to-treat infections due to P. aeruginosa exhibiting the efflux system MexAB-OprM, CFZ at high doses and by continuous infusion should be preferred to TIC and PIP/TAZ.

In vivo efficacy of ceftaroline (PPI-0903), a new broad-spectrum cephalosporin, compared with linezolid and vancomycin against methicillin-resistant and vancomycin-intermediate Staphylococcus aureus in a rabbit endocarditis model.

Using the rabbit endocarditis model, we compared the activity of a new broad-spectrum cephalosporin, ceftaroline, with those of linezolid and vancomycin against methicillin-resistant Staphylococcus aureus. After a 4-day treatment, ceftaroline exhibited superior bactericidal in vivo activity against resistant S. aureus strains and appeared to be the most effective drug against a heterogeneous glycopeptide-intermediate S. aureus strain.

In vitro and in vivo assessment of linezolid combined with ertapenem: a highly synergistic combination against methicillin-resistant Staphylococcus aureus.

Linezolid in combination with ertapenem showed in vitro synergy against methicillin-resistant Staphylococcus aureus strains. We confirmed this interaction in vivo by using a rabbit endocarditis experimental model and simulation of the human pharmacokinetics in animals for both antibiotics. Linezolid plus ertapenem exhibited highly synergistic activity in vivo after 4 days of treatment.

Activity of glycopeptides against Staphylococcus aureus infection in a rabbit endocarditis model: MICs do not predict in vivo efficacy.

The in vivo efficacy of vancomycin and teicoplanin against five Staphylococcus aureus strains with different susceptibilities to them and methicillin was studied. Rabbits were allocated at random to groups for endocarditis induction with one of these five strains and then treated for 2 days with vancomycin or teicoplanin. Each treated group was compared with a control group infected with the same strain. Vancomycin and teicoplanin showed similar activities. Low MICs did not predict better in vivo results.

In vitro and in vivo synergistic activities of linezolid combined with subinhibitory concentrations of imipenem against methicillin-resistant Staphylococcus aureus.

Indifference or moderate antagonism of linezolid combined with other antibiotics in vitro and in vivo have mainly been reported in the literature. We have assessed the in vitro activities of linezolid, alone or in combination with imipenem, against methicillin-resistant Staphylococcus aureus (MRSA) strains using the dynamic checkerboard and time-kill curve methods. Linezolid and low concentrations of imipenem had a synergistic effect, leading us to evaluate the in vivo antibacterial activity of the combination using the rabbit endocarditis experimental model. Two MRSA strains were used for in vivo experiments: one was a heterogeneous glycopeptide-intermediate clinical S. aureus strain isolated from blood cultures, and the other was the S. aureus COL reference strain. Animals infected with one of two MRSA strains were randomly assigned to one of the following treatments: no treatment (controls), linezolid (simulating a dose in humans of 10 mg/kg of body weight every 12 h), a constant intravenous infusion of imipenem (which allowed the steady-state concentration of about 1/32 the MIC of imipenem for each strain to be reached in serum), or the combination of both treatments. Linezolid and imipenem as monotherapies exhibited no bactericidal activity against either strain. The combination of linezolid plus imipenem showed in vivo bactericidal activity that corresponded to a decrease of at least 4.5 log CFU/g of vegetation compared to the counts for the controls. In conclusion, the combination exhibited synergistic and bactericidal activities against two MRSA strains after 5 days of treatment. The combination of linezolid plus imipenem appears to be promising for the treatment of severe MRSA infections and merits further investigations to explore the mechanism underlying the synergy between the two drugs.

In vitro activity of linezolid alone and in combination with gentamicin, vancomycin or rifampicin against methicillin-resistant Staphylococcus aureus by time-kill curve methods.

The in vitro activity of the oxazolidinone linezolid was studied alone and in combination with three antibiotics acting on different cellular targets. Oxazolidinones are bacterial protein synthesis inhibitors that act at a very early stage by preventing the formation of the initiation complex. Combinations of linezolid with gentamicin, vancomycin or rifampicin were evaluated against four methicillin-resistant Staphylococcus aureus strains, using killing curves in conjunction with scanning electron microscopy. Time-kill curves were performed over 24 h using an inoculum of 5 x 10(6)- 1 x 10(7) cfu/mL. Linezolid was studied at concentrations of 1 x, 4 x and 8 x MIC, with partner drugs at 8 x MIC. Addition of linezolid resulted in a decrease of antibacterial activity for gentamicin and vancomycin, and linezolid was antagonistic to the early bactericidal activity of gentamicin. Linezolid, in combination with rifampicin, showed an additive interaction for susceptible strains and inhibited rifampicin-resistant variants. Linezolid plus rifampicin appeared to be the most active combination against methicillin-resistant S. aureus strains in time-kill experiments.