Clinical Outcomes of Third-Generation Cephalosporin Definitive Therapy for Bloodstream Infections Due to Enterobacterales with Potential AmpC Induction: A Single-Center Retrospective Study.

The recommended therapy for severe infections caused by AmpC-inducible Enterobacterales (AmpC-E) typically involves cefepime or carbapenems. In an era of emerging resistance to these antimicrobials, we aim to assess the impact of third-generation cephalosporins (3GCs) vs. alternative antibiotics on clinical outcomes in bloodstream infections (BSIs) due to AmpC-E. We retrospectively included hospitalized adult patients with BSIs caused by 3GC-susceptible AmpC-E between 2012 and 2022, comparing the outcomes of 3GC and non-3GC definitive therapies. The primary outcome was overall treatment failure (OTF), encompassing 90-day all-cause mortality, 90-day reinfection, and 90-day readmission. Secondary outcomes comprised components of the OTF, in-hospital all-cause mortality, and length-of-stay. Within a total cohort of 353 patients, OTF occurred in 46.5% and 41.5% in the 3GC- and non-3GC-therapy groups, respectively (p = 0.36). The 3GC-therapy group exhibited a longer length-of-stay (38 vs. 21 days, p = 0.0003) and higher in-hospital mortality (23.3% vs. 13.4%, p = 0.019). However, the 90-day mortality, 90-day reinfection, and 90-day readmission were comparable between the therapy groups. Subgroup analyses involving high-risk AmpC-E and 3GC vs. standard-of-care yielded similar conclusions. Overall, our findings suggest that 3GC definitive therapy may not result in poorer clinical outcomes for the treatment of BSIs caused by AmpC-E.

What remains from living cells in bacterial lysate-based cell-free systems.

Because they mimic cells while offering an accessible and controllable environment, lysate-based cell-free systems (CFS) have emerged as valuable biotechnology tools for synthetic biology. Historically used to uncover fundamental mechanisms of life, CFS are nowadays used for a multitude of purposes, including protein production and prototyping of synthetic circuits. Despite the conservation of fundamental functions in CFS like transcription and translation, RNAs and certain membrane-embedded or membrane-bound proteins of the host cell are lost when preparing the lysate. As a result, CFS largely lack some essential properties of living cells, such as the ability to adapt to changing conditions, to maintain homeostasis and spatial organization. Regardless of the application, shedding light on the black-box of the bacterial lysate is necessary to fully exploit the potential of CFS. Most measurements of the activity of synthetic circuits in CFS and in vivo show significant correlations because these only require processes that are preserved in CFS, like transcription and translation. However, prototyping circuits of higher complexity that require functions that are lost in CFS (cell adaptation, homeostasis, spatial organization) will not show such a good correlation with in vivo conditions. Both for prototyping circuits of higher complexity and for building artificial cells, the cell-free community has developed devices to reconstruct cellular functions. This mini-review compares bacterial CFS to living cells, focusing on functional and cellular process differences and the latest developments in restoring lost functions through complementation of the lysate or device engineering.

Effects of different nutrient supply on metabolism and mammary immune response to an LPS challenge in early lactation of dairy cows.

Energy and nutrient deficiency in dairy cows in early lactation is considered to contribute to their increased susceptibility to mastitis. We have tested the hypothesis that feeding diets with high contents of either nitrogenic, glucogenic, or lipogenic components in early lactation affects both the endocrine and metabolic status, as well as the mammary immune competence. After calving, cows were fed increasing amounts of concentrate up to 10 kg/d rich in crude protein (nitrogenic, n = 10), glucogenic precursors (glucogenic, n = 11), or lipids (lipogenic, n = 11). In wk 3, one udder quarter was challenged with lipopolysaccharide (LPS) from Escherichia coli. Blood and milk were sampled on the day before LPS challenge (d -1), and on d 0, 1, 2, 3, and 9 after LPS challenge. On the day of LPS challenge additional samples were taken hourly for quarter milk and every 3 h for blood. Urea concentrations were higher in plasma and milk of cows fed the nitrogenic diet. However, plasma concentrations of glucose, cholesterol, triglycerides, ß-hydroxybutyrate, nonesterified fatty acids, as well as insulin, glucagon, and insulin-like growth factor-1 were not affected by the different diets. The mammary immune challenge induced a substantial increase of somatic cell count (SCC) in the treated quarter, and a transient decrease of total milk yield and white blood cells similar in all diet groups for one day. The absolute phagocytosis of blood leukocytes was decreased; however, the phagocytosis per cell was increased in glucogenic-fed cows at 6 h after LPS challenge. During mammary inflammation an insulin resistance, shown by increased plasma glucose, insulin, and glucagon, developed similarly in all diet groups. ß-hydroxybutyrate and nonesterified fatty acids were decreased at 1 d after LPS challenge in glucogenic-fed cows only. Cholesterol did not change, and triglycerides only decreased significantly in lipogenic-fed cows 6 h after challenge. On d 9 after LPS challenge, SCC and milk yield and metabolic factors were recovered in all groups. In conclusion, the endocrine and metabolic situation, and the immune response to intramammary LPS of dairy cows during early lactation was not substantially influenced by the elevated supply of nitrogenic, glucogenic, or lipogenic components due to the provided feed in this study.

Influence of nutrient availability on in vitro growth of major bovine mastitis pathogens.

The aim of the present study was to investigate the effects of milk composition changes on the in vitro growth of bovine mastitis pathogens. Nutritional requirements of three major bovine mastitis pathogens Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and Streptococcus uberis (S. uberis) were investigated in vitro. We used ultra-high temperature (UHT) treated milk with different contents of fat, protein, and carbohydrates to test the influence of the availability of various milk constituents on pathogen growth characteristics. Additionally, the bacterial growth was investigated under experimentally modified nutrient availability by dilution and subsequent supplementation with individual nutrients (carbohydrates, different nitrogen sources, minerals, and different types of B vitamins) either to milk or to a conventional medium (thioglycolate broth, TB). Varying contents of fat, protein or lactose did not affect bacterial growth with the exception of growth of S. uberis being promoted in protein-enriched milk. The addition of nutrients to diluted whole milk and TB partly revealed different effects, indicating that there are media-specific growth limiting factors after dilution. Supplementation of minerals to diluted milk did not affect growth rates of all studied bacteria. Bacterial growth in diluted whole milk was decreased by the addition of high concentrations of amino acids in S. aureus, and by urea and additional B vitamins in E. coli and S. aureus. The growth rate of S. uberis was increased by the addition of B vitamins to diluted whole milk. The present results demonstrate that growth-limiting nutrients differ among pathogen types. Because reduced bacterial growth was only shown in diluted milk or TB, it is unlikely that alterations in nutrient availability occurring as a consequence of physiological changes of milk composition in the cow's udder would directly affect the susceptibility or course of bovine mastitis.