We performed a multicentre retrospective cohort study including 606,649 acute inpatient episodes at 10 European hospitals in 2010 and 2011 to estimate the impact of antimicrobial resistance on hospital mortality, excess length of stay (LOS) and cost. Bloodstream infections (BSI) caused by third-generation cephalosporin-resistant Enterobacteriaceae (3GCRE), meticillin-susceptible (MSSA) and -resistant Staphylococcus aureus (MRSA) increased the daily risk of hospital death (adjusted hazard ratio (HR) = 1.80; 95% confidence interval (CI): 1.34–2.42, HR = 1.81; 95% CI: 1.49–2.20 and HR = 2.42; 95% CI: 1.66–3.51, respectively) and prolonged LOS (9.3 days; 95% CI: 9.2–9.4, 11.5 days; 95% CI: 11.5–11.6 and 13.3 days; 95% CI: 13.2–13.4, respectively). BSI with third-generation cephalosporin-susceptible Enterobacteriaceae (3GCSE) significantly increased LOS (5.9 days; 95% CI: 5.8–5.9) but not hazard of death (1.16; 95% CI: 0.98–1.36). 3GCRE significantly increased the hazard of death (1.63; 95% CI: 1.13–2.35), excess LOS (4.9 days; 95% CI: 1.1–8.7) and cost compared with susceptible strains, whereas meticillin resistance did not. The annual cost of 3GCRE BSI was higher than of MRSA BSI. While BSI with S. aureus had greater impact on mortality, excess LOS and cost than Enterobacteriaceae per infection, the impact of antimicrobial resistance was greater for Enterobacteriaceae.

During intracellular infections, autophagy significantly contributes to the elimination of pathogens, regulation of pro-inflammatory signaling, secretion of immune mediators and in coordinating the adaptive immune system. Intracellular pathogens such as S. Typhimurium have evolved mechanisms to circumvent autophagy. However, the regulatory mechanisms targeted by S. Typhimurium to modulate autophagy have not been fully resolved. Here we report that cytosolic energy loss during S. Typhimurium infection triggers transient activation of AMPK, an important checkpoint of mTOR activity and autophagy. The activation of AMPK is regulated by LKB1 in a cytosolic complex containing Sirt1 and LKB1, where Sirt1 is required for deacetylation and subsequent activation of LKB1. S. Typhimurium infection targets Sirt1, LKB1 and AMPK to lysosomes for rapid degradation resulting in the disruption of the AMPK-mediated regulation of mTOR and autophagy. The degradation of cytosolic Sirt1/LKB1/AMPK complex was not observed with two mutant strains of S. Typhimurium, ΔssrB and ΔssaV, both compromising the pathogenicity island 2 (SPI2). The results highlight virulence factor-dependent degradation of host cell proteins as a previously unrecognized strategy of S. Typhimurium to evade autophagy.

Type I interferon (IFN-I) triggers necroptosis in macrophages infected with S. Typhimurium by an unclear mechanism. Hos et al. now demonstrate that RIP3 enhances the interaction of Nrf2 with Pgam5 in response to IFN-I signaling in S. Typhimurium–infected macrophages, which abates Nrf2-dependent cytoprotective pathways and increases cell death.

Background Sick newborns admitted to neonatal units in low-resource settings are at an increased risk of developing hospital-acquired infections due to poor clinical care practices. Clusters of infection, due to the same species, with a consistent antibiotic resistance profile, and in the same ward over a short period of time might be indicative of an outbreak. We used whole-genome sequencing (WGS) to define the transmission pathways and characterise two distinct outbreaks of neonatal bacteraemia in a west African neonatal unit.Methods We studied two outbreaks of Burkholderia cepacia and multidrug-resistant extended spectrum β-lactamase (ESBL)-producing Klebsiella pneumoniae in a neonatal unit that provides non-intensive care on the neonatal ward in the Edward Francis Small Teaching Hospital, Banjul, The Gambia. We used WGS to validate and expand findings from the outbreak investigation. We retrospectively sequenced all clinical isolates associated with each outbreak, including isolates obtained from swabs of ward surfaces, environmental fluid cultures, intravenous fluids, and antibiotics administered to newborns. We also sequenced historical B cepacia isolates associated with neonatal sepsis in the same ward. ResultsBetween March 1 and Dec 31, 2016, 321 blood cultures were done, of which 178 (55%) were positive with a clinically significant isolate. 49 episodes of neonatal B cepacia bacteraemia and 45 episodes of bacteraemia due to ESBL-producing K pneumoniae were reported. WGS revealed the suspected K pneumoniae outbreak to be contemporaneous outbreaks of K pneumoniae (ST39) and previously unreported Klebsiella quasipneumoniae subspecies similipneumoniae (ST1535). Genomic analysis showed near-identical strain clusters for each of the three outbreak pathogens, consistent with transmission within the neonatal ward from extrinsically contaminated in-use intravenous fluids and antibiotics. Time-dated phylogeny, including retrospective analysis of archived bacterial strains, suggest B cepacia has been endemic in the neonatal ward over several years, with the Klebsiella species a more recent introduction.Interpretation Our study highlights the emerging threat of previously unreported strains of multidrug-resistant Klebsiella species in this neonatal unit. Genome-based surveillance studies can improve identification of circulating pathogen strains, characterisation of antimicrobial resistance, and help understand probable infection acquisition routes during outbreaks in newborn units in low-resource settings. Our data provide evidence for the need to regularly monitor endemic transmission of bacteria within the hospital setting, identify the introduction of resistant strains from the community, and improve clinical practices to reduce or prevent the spread of infection and resistance.

No abstract

Salmonella enterica serovar Typhimurium (S. Typhimurium) is a Gram-negative bacterium that induces cell death of macrophages as a key virulence strategy. We have previously demonstrated that the induction of macrophage death is dependent on the host's type I IFN (IFN-I) response. IFN-I signaling has been shown to induce tripartite motif (TRIM) 21, an E3 ubiquitin ligase with critical functions in autoimmune disease and antiviral immunity. However, the importance and regulation of TRIM21 during bacterial infection remains poorly understood. In this study, we investigated the role of TRIM21 upon S. Typhimurium infection of murine bone marrow-derived macrophages. Although Trim21 expression was induced in an IFN-I-dependent manner, we found that TRIM21 levels were mainly regulated posttranscriptionally. Following TLR4 activation, TRIM21 was transiently degraded via the lysosomal pathway by chaperone-mediated autophagy (CMA). However, S. Typhimurium-induced mTORC2 signaling led to phosphorylation of Akt at S473, which subsequently impaired TRIM21 degradation by attenuating CMA. Elevated TRIM21 levels promoted macrophage death associated with reduced transcription of NF erythroid 2-related factor 2 (NRF2)-dependent antioxidative genes. Collectively, our results identify IFN-I-inducible TRIM21 as a negative regulator of innate immune responses to S. Typhimurium and a previously unrecognized substrate of CMA. To our knowledge, this is the first study reporting that a member of the TRIM family is degraded by the lysosomal pathway.

The dynamic interplay between metabolism and immune responses in health and disease, by which different immune cells impact on metabolic processes, are being increasingly appreciated. However, the potential of master regulators of metabolism to control innate immunity are less understood. Here, we studied the cross-talk between leptin signaling and macrophage function in the context of bacterial infections. We found that upon infection with Gram-negative pathogens, such as Salmonella Typhimurium, leptin receptor (Lepr) expression increased in both mouse and human macrophages. Unexpectedly, both genetic Lepr ablation in macrophages and global pharmacologic leptin antagonization augmented lysosomal functions, reduced S. Typhimurium burden, and diminished inflammation in vitro and in vivo. Mechanistically, we show that leptin induction activates the mTORC2/Akt pathway and subsequently down-regulates Phlpp1 phosphatase, allowing for phosphorylated Akt to impair lysosomal-mediated pathogen clearance. These data highlight a link between leptin signaling, the mTORC2/Phlpp1/Akt axis, and lysosomal activity in macrophages and have important therapeutic implications for modulating innate immunity to combat Gram-negative bacterial infections.

BackgroundNonsynonymous single nucleotide polymorphisms (SNPs) in fibronectin binding protein A (fnbA) of Staphylococcus aureus are associated with cardiac device infections. However, the role of fnbA SNPs in S. aureus arthroplasty infection is unknown.MethodsBloodstream S. aureus isolates from a derivation cohort of patients at a single U.S. medical center with S. aureus bacteremia (SAB) and prosthetic hip or knee arthroplasties that were infected (PJI, n = 27) or uninfected (PJU, n = 43) underwent sequencing of fnbA and fnbB. A validation cohort of S. aureus bloodstream PJI (n = 12) and PJU (n = 58) isolates from Germany also underwent fnbA and fnbB sequencing.ResultsOverall, none of the individual fnbA or fnbB SNPs were significantly associated with the PJI or PJU clinical groups within the derivation cohort. Similarly, none of the individual fnbA or fnbB SNPs were associated with PJI or PJU when the analysis was restricted to patients with either early SAB (i.e., bacteremia occurring <1 year after placement or manipulation of prostheses) or late SAB (i.e., bacteremia >1 year after placement or manipulation of prostheses).ConclusionsIn contrast to cardiac device infections, there is no association between nonsynonymous SNPs in fnbA or fnbB of bloodstream S. aureus isolates and arthroplasty infection. These results suggest that initial steps leading to S. aureus infection of cardiovascular and orthopedic prostheses may arise by distinct processes.