Rationale: Saline is the intravenous fluid most commonly administered to critically ill adults, but it may be associated with acute kidney injury and death. Whether use of balanced crystalloids rather than saline affects patient outcomes remains unknown.Objectives: To pilot a cluster-randomized, multiple-crossover trial using software tools within the electronic health record to compare saline to balanced crystalloids.Methods: This was a cluster-randomized, multiple-crossover trial among 974 adults admitted to a tertiary medical intensive care unit from February 3, 2015 to May 31, 2015. The intravenous crystalloid used in the unit alternated monthly between saline (0.9% sodium chloride) and balanced crystalloids (lactated Ringer's solution or PlasmaLyte A). Enrollment, fluid delivery, and data collection were performed using software tools within the electronic health record. The primary outcome was the difference between study groups in the proportion of isotonic crystalloid administered that was saline. The secondary outcome was major adverse kidney events within 30 days (MAKE30), a composite of death, dialysis, or persistent renal dysfunction.Measurements and Main Results: Patients assigned to saline (n = 454) and balanced crystalloids (n = 520) were similar at baseline and received similar volumes of crystalloid by 30 days (median [interquartile range]: 1,424 ml [500-3,377] vs. 1,617 ml [500-3,628]; P = 0.40). Saline made up a larger proportion of the isotonic crystalloid given in the saline group than in the balanced crystalloid group (91% vs. 21%; P , 0.001). MAKE30 did not differ between groups (24.7% vs. 24.6%; P = 0.98).Conclusions: An electronic health record-embedded, clusterrandomized, multiple-crossover trial comparing saline with balanced crystalloids can produce well-balanced study groups and separation in crystalloid receipt.Clinical trial registered with www.clinicaltrials.gov (NCT 02345486).

Clostridium difficile is the most commonly reported nosocomial pathogen in the United States and is an urgent public health concern worldwide1. Over the past decade, incidence, severity, and costs associated with C. difficile infection (CDI) have increased dramatically2. CDI is most commonly initiated by antibiotic-mediated disruption of the gut microbiota; however, non-antibiotic associated CDI cases are well documented and on the rise3,4. This suggests that unexplored environmental, nutrient, and host factors likely influence CDI. Here we show that excess dietary zinc (Zn) significantly alters the gut microbiota and in turn reduces the threshold of antibiotics needed to confer susceptibility to C. difficile infection. In mice colonized with C. difficile, excess dietary Zn severely exacerbates C. difficile-associated disease by increasing toxin activity and altering the host immune response. In addition, we show that the Zn binding S100 protein calprotectin is antimicrobial against C. difficile and an essential component of the innate immune response to CDI. Together, these data suggest that nutrient Zn levels play a key role in determining susceptibility to CDI and severity of disease, and that calprotectin-mediated metal limitation is an important factor in the host immune response to C. difficile.

Importance Daily bathing of critically ill patients with the broad spectrum, topical antimicrobial agent chlorhexidine is widely performed and may reduce healthcare-associated infections. Objective To determine if daily bathing of critically ill patients with chlorhexidine decreases the incidence of healthcare-associated infections. Design, setting, and participants A pragmatic cluster-randomized, cross-over study of 9,340 patients admitted to five adult intensive care units of a tertiary medical center in Nashville, Tennessee Intervention Units performed once-daily bathing of all patients with disposable cloths impregnated with 2% chlorhexidine or non-antimicrobial cloths as a control. Bathing treatments were performed for a 10-week period followed by a two-week washout period during which patients were bathed with non-antimicrobial disposable cloths, before crossover to the alternate bathing treatment for 10 weeks. Each unit crossed over between bathing assignments three times during the study Main Outcome and Measures The primary prespecified outcome was a composite of central line-associated blood stream infections (CLABSI), catheter-associated urinary tract infections (CAUTI), ventilator-associated pneumonia (VAP), and Clostridium difficile infections. Secondary outcomes included rates of clinical cultures positive for multi-drug resistant organisms, blood culture contamination, healthcare-associated bloodstream infections, and rates of the primary outcome by ICU. Results A total of 55 and 60 infections occurred during chlorhexidine and control bathing periods, respectively (4 and 4 CLABSI, 21 and 32 CAUTI, 17 and 8 VAP, 13 and 16 C. difficile infections, respectively, between chlorhexidine and control bathing periods). The primary outcome rate was 2.86 per 1000 patient-days and 2.90 per 1000 patient-days during chlorhexidine and control bathing periods, respectively (rate difference, −0.04; 95% CI, −1.09 to 1.01; P=0.95). After adjusting for baseline variables, no difference between groups in the rate of the primary outcome was detected. Chlorhexidine bathing did not change rates of infection-related secondary outcomes including hospital-acquired bloodstream infections, blood culture contamination, or clinical cultures yielding multi-drug resistant organisms. In a prespecified subgroup analysis, no difference in the primary outcome was detected in any individual ICU. Conclusion and Relevance In this pragmatic trial, daily bathing with chlorhexidine did not reduce the incidence of healthcare-associated infections including central line-associated bloodstream infections, catheter-associated urinary tract infections, ventilator-associated pneumonia, or C. difficile. These findings do not support daily bathing of critically ill patients with chlorhexidine. Trial Registration ClinicalTrials.gov number, NCT02033187

SCCmec is a mobile genetic element that carries the gene (mecA) mediating methicillin resistance in staphylococci. For Staphylococcus aureus, four SCCmec types have been described, one (type IV) of which has been associated with newly identified community-acquired methicillin-resistant S. aureus. However, the distribution of SCCmec types among S. epidermidis is not known. SCCmec typing of a collection of 44 methicillinresistant Staphylococcus epidermidis (MRSE) isolates recovered between 1973 and 1983 from the blood of patients with prosthetic valve endocarditis (PVE) was performed by PCR amplification of key genetic elements (mecA, mecI, IS1272, and ccrAB). Of the 44 isolates, 1 (2%) harbored SCCmec type I, 15 (34%) harbored type II, 12 (28%) harbored type III, and 16 (36%) harbored type IV. The complete nucleotide sequence of SCCmec type IV was determined for 16 isolates and found to be identical in size (24 kb) and 98% homologous to DNA sequences published for S. aureus. Type IV SCCmec was also common (5 of 10 isolates) among a geographically dispersed collection of 10 recent (1998 to 2001) S. epidermidis bloodstream isolates. Multilocus sequence typing (MLST) (using the same seven genes presently employed for S. aureus MLST) of these MRSE isolates and of 10 additional recent geographically dispersed methicillin-susceptible isolates demonstrated that all 16 PVE isolates and 2 of 5 recent isolates harboring type IV SCCmec were in three related clonal groups. All three MSSE PVE isolates recovered from patients between 1976 and 1979 were in the same clonal groups as type IV SCCmec MRSE isolates. These data support the hypothesis of intra-and interspecies transfer of type IV SCCmec and suggest that there are clonal associations in S. epidermidis that correlate with SCCmec type.

Microorganisms form biofilms containing differentiated cell populations. To determine factors driving differentiation, we herein visualize protein and metal distributions within Pseudomonas aeruginosa biofilms using imaging mass spectrometry. These in vitro experiments reveal correlations between differential protein distribution and metal abundance. Notably, zinc- and manganese-depleted portions of the biofilm repress the production of anti-staphylococcal molecules. Exposure to calprotectin (a host protein known to sequester metal ions at infectious foci) recapitulates responses occurring within metal-deplete portions of the biofilm and promotes interaction between P. aeruginosa and Staphylococcus aureus. Consistent with these results, the presence of calprotectin promotes co-colonization of the murine lung, and polymicrobial communities are found to co-exist in calprotectin-enriched airspaces of a cystic fibrosis lung explant. These findings, which demonstrate that metal fluctuations are a driving force of microbial community structure, have clinical implications because of the frequent occurrence of P. aeruginosa and S. aureus co-infections.