The c-di-AMP-binding protein CbpB modulates the level of ppGpp alarmone in Streptococcus agalactiae.

Cyclic di-AMP is an essential signalling molecule in Gram-positive bacteria. This second messenger regulates the osmotic pressure of the cell by interacting directly with the regulatory domains, either RCK_C or CBS domains, of several potassium and osmolyte uptake membrane protein systems. Cyclic di-AMP also targets stand-alone CBS domain proteins such as DarB in Bacillus subtilis and CbpB in Listeria monocytogenes. We show here that the CbpB protein of Group B Streptococcus binds c-di-AMP with a very high affinity. Crystal structures of CbpB reveal the determinants of binding specificity and significant conformational changes occurring upon c-di-AMP binding. Deletion of the cbpB gene alters bacterial growth in low potassium conditions most likely due to a decrease in the amount of ppGpp caused by a loss of interaction between CbpB and Rel, the GTP/GDP pyrophosphokinase.

Optimizing the correct timing of vancomycin level collection utilizing a vancomycin medication administration record (MAR) level order.

OBJECTIVE: Vancomycin, a commonly used antimicrobial, has a narrow therapeutic index; therefore, Therapeutic Drug Monitoring (TDM) is required. Although the Electronic Medical Record (EMR) may improve patient care, without appropriate optimization, it can contribute to incorrectly drawn vancomycin levels. For medication administration, nurses utilize the Medication Administration Record (MAR) for medication administration documentation and medication workflow guidance. Therefore, we hypothesized creating a MAR level order which would be incorporated into this already established medication workflow may improve the rate of correctly drawn vancomycin levels. MATERIALS AND METHODS: This was a multicenter, retrospective, pre-and post-intervention study which evaluated the effect of a Medication Administration Record (MAR) level order within the EMR on the correct timing of vancomycin level collection. Vancomycin levels were classified into pre-and post-intervention groups. The primary endpoint was the rate of incorrectly drawn levels, defined as a level being drawn early, a level being drawn late, a level drawn while infusing, or a missed level. RESULTS: A total of 1353 vancomycin levels were assessed, and 628 levels met inclusion criteria. Of the levels eligible for inclusion, 331 were in the pre-intervention period and 297 were in the post-intervention period. Levels in the post-intervention group utilizing the vancomycin MAR level order were less likely to be missed or drawn at an incorrect time (11.1 % vs 36 %, P < 0.01) and were less likely to require rescheduling (3.4 % vs 8.5 %, P < 0.01). CONCLUSION: Utilization of a vancomycin MAR level order was associated with a significant decrease in incorrectly drawn vancomycin levels.

A Hospital-Based Program to Reduce Central Line-Associated Bloodstream Infections among Hospitalized Patients Receiving Hemodialysis Using a Central Venous Catheter for Vascular Access.

Central venous catheter (CVC) vascular access is common among patients on hemodialysis. CVC use carries a substantial risk of central line-associated bloodstream infections (CLABSIs), costly events that place patients at a high risk of mortality. Our hospital and dialysis organization developed a cooperative strategy to reduce the rate of CLABSI among hospitalized patients on hemodialysis with a CVC. The program included the use of training and reporting tools to guide hospital staff with CLABSI prevention, as well as leadership committees to oversee the process. Fourteen CLABSIs were reported in the 17-month period prior to the implementation of the program, while no new CLABSIs occurred in the 30 months following implementation of the program. This prevention program effectively reduced the frequency of CLABSIs. Broader implementation of such programs may result in better outcomes and lower costs for hospitalized patients on hemodialysis.

Cyclic di-AMP regulation of osmotic homeostasis is essential in Group B Streptococcus.

Cyclic nucleotides are universally used as secondary messengers to control cellular physiology. Among these signalling molecules, cyclic di-adenosine monophosphate (c-di-AMP) is a specific bacterial second messenger recognized by host cells during infections and its synthesis is assumed to be necessary for bacterial growth by controlling a conserved and essential cellular function. In this study, we sought to identify the main c-di-AMP dependent pathway in Streptococcus agalactiae, the etiological agent of neonatal septicaemia and meningitis. By conditionally inactivating dacA, the only diadenyate cyclase gene, we confirm that c-di-AMP synthesis is essential in standard growth conditions. However, c-di-AMP synthesis becomes rapidly dispensable due to the accumulation of compensatory mutations. We identified several mutations restoring the viability of a ΔdacA mutant, in particular a loss-of-function mutation in the osmoprotectant transporter BusAB. Identification of c-di-AMP binding proteins revealed a conserved set of potassium and osmolyte transporters, as well as the BusR transcriptional factor. We showed that BusR negatively regulates busAB transcription by direct binding to the busAB promoter. Loss of BusR repression leads to a toxic busAB expression in absence of c-di-AMP if osmoprotectants, such as glycine betaine, are present in the medium. In contrast, deletion of the gdpP c-di-AMP phosphodiesterase leads to hyperosmotic susceptibility, a phenotype dependent on a functional BusR. Taken together, we demonstrate that c-di-AMP is essential for osmotic homeostasis and that the predominant mechanism is dependent on the c-di-AMP binding transcriptional factor BusR. The regulation of osmotic homeostasis is likely the conserved and essential function of c-di-AMP, but each species has evolved specific c-di-AMP mechanisms of osmoregulation to adapt to its environment.

Cyclic di-AMP in host-pathogen interactions.

Cyclic di-AMP (c-di-AMP) is a bacterial signaling nucleotide synthesized by several human pathogens. This widespread and specific bacterial product is recognized by infected host cells to trigger an innate immune response. Detection of c-di-AMP in the host cytosol leads primarily to the induction of type I interferon via the STING-cGAS signaling axis, while being also entangled in the activation of the NF-κB pathway. During their long-standing interaction, host and pathogens have co-evolved to control c-di-AMP activation of innate immunity. On the bacterial side, the quantity of c-di-AMP released inside cells allows to manipulate the host response to exacerbate infection by avoiding immune recognition or, at the opposite, by overloading the STING-cGAS pathway.