Microbiome-Independent Effects of Antibiotics in a Murine Model of Nosocomial Infections

Dietary and water restriction leads to increased susceptibility to antimicrobial resistant pathogens

Dehydration and malnutrition are common and often underdiagnosed in hospital settings. Multidrug-resistant bacterial infections result in more than 35,000 deaths a year in nosocomial patients. The effect of temporal dietary and water restriction (DWR) on susceptibility to multidrug-resistant pathogens is unknown. We report that DWR markedly increased susceptibility to systemic infection by ESKAPE pathogens. Using a murine bloodstream model of methicillin-resistant Staphylococcus aureus infection, we show that DWR leads to significantly increased mortality and morbidity. DWR causes increased bacterial burden, severe pathology, and increased numbers of phagocytes in the kidney. DWR appears to alter the functionality of these phagocytes and is therefore unable to control infection. Mechanistically, we show that DWR impairs the ability of macrophages to phagocytose multiple bacterial pathogens and efferocytose apoptotic neutrophils. Together, this work highlights the crucial impact that diet and hydration play in protecting against infection.

Epidemiology and risk factors of nosocomial infections in a Chinese tertiary-care hospital: a 10-year retrospective case-control study

BACKGROUND

Nosocomial infections (NIs) are the most frequent adverse events among patients and cause a heavy burden on both health and economics. To investigate epidemiology of NIs and identify risk factors for NIs by integrating continuous long-term surveillance data.

METHODS

We performed an observational study among inpatients at the Chinese People's Liberation Army General Hospital between January 1, 2010, and December 31, 2019. Infection rates, mortality rates and percentage of NIs were calculated. Trends of yearly infection rates by pathogens were assessed using Mann-Kendall trend test. Controls were matched to cases (2:1) by age (±2 years), sex, admission date (±1 year) and admission diagnosis, and conditional logistic regression was used to estimate odds ratios.

RESULTS

A total of 1,534,713 inpatients were included among which 33,468 NIs cases occurred with an infection rate of 2.18%. The most common infections were respiratory system infection (52.22%), bloodstream infection (17.60%), and genitourinary system infection (15.62%). Acinetobacter. baumannii (9.6%), Klebsiella. pneumoniae (9.0%), Pseudomonas. aeruginosa (8.6%), Escherichia. coli (8.6%) and Enterococcus. faecium (5.0%) were the top five isolated pathogens. Infection rates of K. pneumoniae and carbapenems-resistant K. pneumoniae significantly increased. Prior ICU stay, surgery, any device placement (including central venous catheter, mechanical ventilation, urinary catheter, and tracheotomy), prior use of triple or more antibiotics combinations, carbapenem, and β-Lactamase inhibitors were significantly associated with NIs.

CONCLUSION

K. pneumoniae has the potential to cause a clinical crisis with increasing infection rates and carbapenem resistance. Clinical management of invasive operations and antibiotics use should be further strengthened.

The tempo and mode of gene regulatory programs during bacterial infection

Innate immune recognition of bacterial pathogens is a key determinant of the ensuing systemic response, and host or pathogen heterogeneity in this early interaction can impact the course of infection. To gain insight into host response heterogeneity, we investigate macrophage inflammatory dynamics using primary human macrophages infected with Group B Streptococcus. Transcriptomic analysis reveals discrete cellular states within responding macrophages, one of which consists of four sub-states, reflecting inflammatory activation. Infection with six additional bacterial species-Staphylococcus aureus, Listeria monocytogenes, Enterococcus faecalis, Yersinia pseudotuberculosis, Shigella flexneri, and Salmonella enterica-recapitulates these states, though at different frequencies. We show that modulating the duration of infection and the presence of a toxin impacts inflammatory trajectory dynamics. We provide evidence for this trajectory in infected macrophages in an in vivo model of Staphylococcus aureus infection. Our cell-state analysis defines a framework for understanding inflammatory activation dynamics in response to bacterial infection.