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ObjectiveTo compare clinical outcomes in children with hemophagocytic lymphohistiocytosis (HLH) and macrophage activation syndrome (MAS) who were managed before and after implementation of an evidence-based guideline (EBG).MethodsA management algorithm for MAS-HLH was developed at our institution based on literature review, expert opinion, and consensus building across multiple pediatric subspecialties. An electronic medical record search retrospectively identified hospitalized patients with MAS-HLH in the pre-EBG (October 15, 2015, to December 4, 2017) and post-EBG (January 1, 2018, to January 21, 2020) time periods. Predetermined outcome metrics were evaluated in the 2 cohorts.ResultsAfter the EBG launch, 57 children were identified by house staff as potential patients with MAS-HLH, and rheumatology was consulted for management. Ultimately, 17 patients were diagnosed with MAS-HLH by the treating team. Of these, 59% met HLH 2004 criteria, and 94% met 2016 classification criteria for MAS complicating systemic juvenile idiopathic arthritis. There was a statistically significant reduction in mortality from 50% before implementation of the EBG to 6% in the post-EBG cohort (P = 0.02). There was a significant improvement in time to 50% reduction in C-reactive protein level in the post-EBG vs pre-EBG cohorts (log-rank P < 0.01). There were trends toward faster time to MAS-HLH diagnosis, faster initiation of immunosuppressive therapy, shorter length of hospital stay, and more rapid normalization of MAS-HLH–related biomarkers in the patients post-EBG.ConclusionWhile the observed improvements may be partially attributed to advances in treatment of MAS-HLH that have accumulated over time, this analysis also suggests that a multidisciplinary treatment pathway for MAS-HLH contributed meaningfully to favorable patient outcomes.

The purpose of this document is to highlight practical recommendations to assist acute care hospitals to prioritize and implement strategies to prevent ventilator-associated pneumonia (VAP), ventilator-associated events (VAE), and non-ventilator hospital-acquired pneumonia (NV-HAP) in adults, children, and neonates. This document updates the Strategies to Prevent Ventilator-Associated Pneumonia in Acute Care Hospitals published in 2014. This expert guidance document is sponsored by the Society for Healthcare Epidemiology (SHEA), and is the product of a collaborative effort led by SHEA, the Infectious Diseases Society of America, the American Hospital Association, the Association for Professionals in Infection Control and Epidemiology, and The Joint Commission, with major contributions from representatives of a number of organizations and societies with content expertise.

We instituted Kamishibai (K-card rounding) with the goals of improving indwelling urinary catheter maintenance bundle reliability and decreasing catheter associated urinary tract infection (CAUTI) rates.In a free-standing children's hospital, we undertook a hospital-wide quality improvement project from January 2019 to June 2021 after developing a K-card based on our urinary catheter maintenance bundle. Auditors used K-cards to ask standardized questions during weekly rounds. Bundle reliability and CAUTI rates were analyzed prospectively.During the study period, 826 K-card audits were performed for 657 unique patients. While overall maintenance bundle reliability remained stable at 84%, there was a statistically significant improvement in reliability to the bundle element "medical discussion of need for the urinary catheter" from 88% to 94% (P=0.01). The hospital-wide CAUTI rate significantly decreased (incidence rate ratio [IRR], 0.38; 95% CI, 0.15-0.93; P=0.04).Hospital-wide urinary catheter K-card rounding facilitated standardized data collection, discussion of reliability and real-time feedback to nurses. Maintenance bundle reliability remained stable after implementation, accompanied by a significant decrease in the CAUTI rate.Implementation of hospital-wide urinary catheter K-card rounding was associated with reduction in CAUTI rates. The project demonstrated likelihood of reproducibility with support of a multidisciplinary team.

The Gram-negative pathogen Pseudomonas aeruginosa is a common cause of pneumonia in hospitalized patients. Its increasing antibiotic resistance and widespread occurrence present a pressing need for vaccines. We previously showed that a P. aeruginosa type III secretion system protein, PopB elicits a strong Th17 response in mice after intranasal (IN) immunization and confers antibody-independent protection against pneumonia in mice. In the current study, we evaluated the immunogenicity and protective efficacy in mice of the combination of PopB (purified with its chaperone protein PcrH) and OprF/I, an outer membrane hybrid fusion protein, compared to immunization with the proteins individually either by the intranasal (IN) or subcutaneous (SC) routes. Our results show that after vaccination, a Th17 recall response from splenocytes was detected only in mice vaccinated with PopB/PcrH, either alone or in combination with OprF/I. Mice that were immunized with the combination of PopB/PcrH and OprF/I had enhanced protection in an acute lethal P. aeruginosa pneumonia model, regardless of vaccine route, compared to the mice vaccinated the with either alone or adjuvant control. Immunization generated IgG titers against the vaccine proteins and whole P. aeruginosa cells. Interestingly, none of these antisera had opsonophagocytic killing activity, but antisera from mice immunized with vaccines containing OprF/I had the ability to block IFN-γ binding to OprF/I, a known virulence mechanism. Hence, vaccines combining PopB/PcrH with OprF/I that elicit functional antibodies lead to a broadly and potently protective vaccine against P. aeruginosa pulmonary infections.

Blood culture overuse in the pediatric intensive care unit (PICU) can lead to unnecessary antibiotic use and contribute to antibiotic resistance. Optimizing blood culture practices through diagnostic stewardship may reduce unnecessary blood cultures and antibiotics.To evaluate the association of a 14-site multidisciplinary PICU blood culture collaborative with culture rates, antibiotic use, and patient outcomes.This prospective quality improvement (QI) collaborative involved 14 PICUs across the United States from 2017 to 2020 for the Bright STAR (Testing Stewardship for Antibiotic Reduction) collaborative. Data were collected from each participating PICU and from the Children's Hospital Association Pediatric Health Information System for prespecified primary and secondary outcomes.A local QI program focusing on blood culture practices in the PICU (facilitated by a larger QI collaborative).The primary outcome was blood culture rates (per 1000 patient-days/mo). Secondary outcomes included broad-spectrum antibiotic use (total days of therapy and new initiations of broad-spectrum antibiotics ≥3 days after PICU admission) and PICU rates of central line-associated bloodstream infection (CLABSI), Clostridioides difficile infection, mortality, readmission, length of stay, sepsis, and severe sepsis/septic shock.Across the 14 PICUs, the blood culture rate was 149.4 per 1000 patient-days/mo preimplementation and 100.5 per 1000 patient-days/mo postimplementation, for a 33% relative reduction (95% CI, 26%-39%). Comparing the periods before and after implementation, the rate of broad-spectrum antibiotic use decreased from 506 days to 440 days per 1000 patient-days/mo, respectively, a 13% relative reduction (95% CI, 7%-19%). The broad-spectrum antibiotic initiation rate decreased from 58.1 to 53.6 initiations/1000 patient-days/mo, an 8% relative reduction (95% CI, 4%-11%). Rates of CLABSI decreased from 1.8 to 1.1 per 1000 central venous line days/mo, a 36% relative reduction (95% CI, 20%-49%). Mortality, length of stay, readmission, sepsis, and severe sepsis/septic shock were similar before and after implementation.Multidisciplinary diagnostic stewardship interventions can reduce blood culture and antibiotic use in the PICU. Future work will determine optimal strategies for wider-scale dissemination of diagnostic stewardship in this setting while monitoring patient safety and balancing measures.

Background: The gram-negative bacterial pathogen Pseudomonas aeruginosa causes a wide range of infections, mostly in hospitalized and immunocompromised patients, those with burns, surgical wounds, or combat-related wounds, and in people with cystic fibrosis. The increasing antibiotic resistance of P. aeruginosa confers a pressing need for vaccines, yet there are no P. aeruginosa vaccines approved for human use, and recent promising candidates have failed in large clinical trials. Discussion: In this review, we summarize recent clinical trials and pre-clinical studies of P. aeruginosa vaccines and provide a suggested framework for the makeup of a future successful vaccine. Murine models of infection suggest that antibodies, specifically opsonophagocytic killing antibodies (OPK), antitoxin antibodies, and anti-attachment antibodies, combined with T cell immunity, specifically TH17 responses, are needed for broad and potent protection against P. aeruginosa infection. A better understanding of the human immune response to P. aeruginosa infections, and to vaccine candidates, will eventually pave the way to a successful vaccine for this wily pathogen.

ObjectiveTo assess variability in antimicrobial use and associations with infection testing in pediatric ventilator-associated events (VAEs).DesignDescriptive retrospective cohort with nested case-control study.SettingPediatric intensive care units (PICUs), cardiac intensive care units (CICUs), and neonatal intensive care units (NICUs) in 6 US hospitals.PatientsChildren≤18 years ventilated for≥1 calendar day.MethodsWe identified patients with pediatric ventilator-associated conditions (VACs), pediatric VACs with antimicrobial use for≥4 days (AVACs), and possible ventilator-associated pneumonia (PVAP, defined as pediatric AVAC with a positive respiratory diagnostic test) according to previously proposed criteria.ResultsAmong 9,025 ventilated children, we identified 192 VAC cases, 43 in CICUs, 70 in PICUs, and 79 in NICUs. AVAC criteria were met in 79 VAC cases (41%) (58% CICU; 51% PICU; and 23% NICU), and varied by hospital (CICU, 20–67%; PICU, 0–70%; and NICU, 0–43%). Type and duration of AVAC antimicrobials varied by ICU type. AVAC cases in CICUs and PICUs received broad-spectrum antimicrobials more often than those in NICUs. Among AVAC cases, 39% had respiratory infection diagnostic testing performed; PVAP was identified in 15 VAC cases. Also, among AVAC cases, 73% had no associated positive respiratory or nonrespiratory diagnostic test.ConclusionsAntimicrobial use is common in pediatric VAC, with variability in spectrum and duration of antimicrobials within hospitals and across ICU types, while PVAP is uncommon. Prolonged antimicrobial use despite low rates of PVAP or positive laboratory testing for infection suggests that AVAC may provide a lever for antimicrobial stewardship programs to improve utilization.

The Pseudomonas aeruginosa type III secretion system protein PopB and its chaperon protein PcrH, when co-administered with the adjuvant curdlan, elicit Th17 responses after intranasal immunization of mice. These PopB/PcrH-curdlan vaccines protect mice against acute lethal pneumonia in an IL-17-dependent fashion involving CD4 helper T cells secreting IL-17 (Th17 cells). In this study, we tested whether encapsulation of PopB/PcrH in poly-lactic-co-glycolic acid (PLGA) nanoparticles could elicit Th17 responses to PopB. Recombinant PopB/PcrH or PcrH alone was encapsulated into PLGA nanoparticles. Mice (FVB/N) were intranasally immunized with the PLGA-PopB/PcrH nanoparticles, PLGA-PcrH nanoparticles, PLGA alone, or PopB/PcrH alone. The protective efficacy was assessed in an acute lung infection model with a lethal dose of an ExoU-producing version of P. aeruginosa strain PAO1. Th17 responses were assayed by intracellular flow cytometry and by ELISA for IL-17 in supernatants of splenocytes co-cultured with purified PopB/PcrH. PLGA-PopB/PcrH-immunized mice showed 3-4-fold higher Th17 responses both in the lung and in the spleen compared to mice immunized with empty PLGA or PopB/PcrH alone. After challenge with P. aeruginosa, PLGA-PopB/PcrH-immunized mice showed significantly lower bacterial counts in the lungs and improved survival. In conclusion, encapsulation of PopB/PcrH in PLGA nanoparticles can elicit Th17 responses to intranasal vaccination and protect mice against acute lethal P. aeruginosa pneumonia.

Isoflurane and sevoflurane are volatile anesthetics (VA) widely used in clinical practice to provide general anesthesia. We and others have previously shown that VAs have immunomodulatory effects and may have a significant impact on the progression of disease states. Flagellin is a component of Gram negative bacteria and plays a significant role in the pathophysiology of bacterial pneumonia through its binding to Toll-like Receptor 5 (TLR5). Our results showed that VAs, not an intravenous anesthetic, significantly attenuated the activation of TLR5 and the release of the neutrophil chemoattractant IL-8 from lung epithelial cells. Furthermore, flagellin-induced lung injury was significantly attenuated by VAs by inhibiting neutrophil migration to the bronchoalveolar space. The lungs of cystic fibrosis (CF) patients are highly colonized by Pseudomonas aeruginosa, which causes inflammation. The retrospective study of oxygenation in patients with CF who had received VA versus intravenous anesthesia suggested that VAs might have the protective effect for gas exchange. To understand the interaction between VAs and TLR5, a docking simulation was performed, which indicated that isoflurane and sevoflurane docked into the binding interphase between TLR5 and flagellin.

Background Infection is a major complication following cerebral spinal fluid (CSF) diversion procedures for hydrocephalus. However, pediatric risk factors for surgical site infection (SSI) are currently not well defined. Because a SSI prevention bundle is increasingly introduced, the purpose of this study was to evaluate risk factors associated with SSIs following CSF diversion surgeries following a SSI bundle at a single quaternary care pediatric hospital. Methods We performed a retrospective cohort study of patients undergoing CSF diversion procedures from 2017 to 2019. SSIs were identified prospectively through continuous surveillance. We performed unadjusted logistic regression analyses and univariate analyses to determine an association between SSIs and patient demographics, comorbidities and perioperative factors to identify independent risk factors for SSI. Results We identified a total of 558 CSF diversion procedures with an overall SSI rate of 3.4%. The SSI rates for shunt, external ventricular drain (EVD) placement, and endoscopic third ventriculostomy (ETV) were 4.3, 6.9 and 0%, respectively. Among 323 shunt operations, receipt of clindamycin as perioperative prophylaxis and presence of cardiac disease were significantly associated with SSI (O.R. 4.99, 95% C.I. 1.27–19.70, p = 0.02 for the former, and O.R. 7.19, 95% C.I. 1.35–38.35, p = 0.02 for the latter). No risk factors for SSI were identified among 72 EVD procedures. Conclusion We identified receipt of clindamycin as perioperative prophylaxis and the presence of cardiac disease as risk factors for SSI in shunt procedures. Cefazolin is recommended as a standard antibiotic for perioperative prophylaxis. Knowing that unsubstantiated beta-lactam allergy label is a significant medical problem, efforts should be made to clarify beta-lactam allergy status to maximize the number of patients who can receive cefazolin for prophylaxis before shunt placement. Further research is needed to elucidate the mechanism by which cardiac disease may increase SSI risk after shunt procedures.

Structured Summary Background Although surgical site infections (SSIs) remain a significant health care issue, a limited number of studies have analyzed risk factors for SSIs in children, particularly the role of intraoperative anesthetic management. Pediatric patients are less likely to have major adult risk factors for SSIs such as smoking and diabetes. Thus children may be more suitable as a cohort for examining the role of intraoperative anesthetics in SSIs. Aim We examined an association between SSI incidence and anesthetic management in children who underwent elective intestinal surgery in a single institution. Methods We performed a retrospective study of 621 patients who underwent elective intestinal surgery under general anesthesia between January 2017 and September 2019, with primary outcome as the incidence of SSIs. We compared patients who were dichotomized in accordance with the median of the sevoflurane dose. We used propensity score (PS) pairwise matching of these patients to avoid selection biases. PS matching yielded 204 pairs of patients. Results We found that higher doses of sevoflurane were associated with a higher incidence of SSIs (9.8% versus 3.9%, P = 0.019). We adjusted for intraoperative factors that were not included in the PS adjustment factors, and multivariate regression analysis after PS matching showed compatible results (odds ratio: 2.58, 95% confidence interval: 1.11-6.04, P = 0.028). Conclusions Higher doses of sevoflurane are associated with increased odds of SSIs after pediatric elective intestinal surgery. A randomized controlled study of volatile anesthetic-based versus intravenous anesthetic-based anesthesia will be needed to further determine the role of anesthetic drugs in SSI risk.

Objective:To institute facility-wide Kamishibai card (K-card) rounding for central venous catheter (CVC) maintenance bundle education and adherence and to evaluate its impact on bundle reliability and central-line–associated bloodstream infection (CLABSI) rates.Design:Quality improvement project.Setting:Inpatient units at a large, academic freestanding children’s hospital.Participants:Data for inpatients with a CVC in place for ≥1 day between November 1, 2017 and October 31, 2018 were included.Intervention:A K-card was developed based on 7 core elements in our CVC maintenance bundle. During monthly audits, auditors used the K-cards to ask bedside nurses standardized questions and to conduct medical record documentation reviews in real time. Adherence to every bundle element was required for the audit to be considered “adherent.” We recorded bundle reliability prospectively, and we compared reliability and CLABSI rates at baseline and 1 year after the intervention.Results:During the study period, 2,321 K-card audits were performed for 1,051 unique patients. Overall maintenance bundle reliability increased significantly from 43% at baseline to 78% at 12 months after implementation (P < .001). The hospital-wide CLABSI rate decreased from 1.35 during the 12-month baseline period to 1.17 during the 12-month intervention period, but the change was not statistically significant (incidence rate ratio [IRR], 0.87; 95% confidence interval [CI], 0.60–1.24; P = .41).Conclusions:Hospital-wide CVC K-card rounding facilitated standardized data collection, discussion of reliability, and real-time feedback to nurses. Maintenance bundle reliability increased after implementation, accompanied by a nonsignificant decrease in the CLABSI rate.

Background Critically ill infants with congenital heart disease (CHD) are often prescribed stress ulcer prophylaxis (SUP) to prevent upper gastrointestinal bleeding, despite the low incidence of stress ulcers and limited data on the safety and efficacy of SUP in infants. Recently, SUP has been associated with an increased incidence of hospital-acquired infections, community-acquired pneumonia, and necrotizing enterocolitis. The objective of this pilot study is to investigate the feasibility of performing a randomized controlled trial to assess the safety and efficacy of withholding SUP in infants with congenital heart disease admitted to the cardiac intensive care unit. Methods A single center, prospective, double-blinded, randomized placebo-controlled pilot feasibility trial will be performed in infants with CHD admitted to the cardiac intensive care unit and anticipated to require respiratory support for > 24 h. Patients will be randomized to receive a histamine-2 receptor antagonist (H2RA) or placebo until they are discontinued from respiratory support. Randomization will be performed within 2 strata defined by admission type (medical or surgical) and age (neonate, age Discussion Routine use of SUP to prevent upper gastrointestinal bleeding in infants is controversial due to a low incidence of bleeding events and concern for adverse effects. The role of SUP in infants with CHD has not been examined, and there is equipoise on the risks and benefits of withholding this therapy. In addition, this therapy has been discontinued in other neonatal populations due to the concern for hospital-acquired infections and necrotizing enterocolitis. Furthermore, exploring changes to the microbiome after exposure to SUP may highlight the mechanisms by which SUP impacts potential microbial dysbiosis of the gut and its association with hospital-acquired infections. Assessment of the feasibility of a trial of withholding SUP in critically ill infants with CHD will facilitate planning of a larger multicenter trial of safety and efficacy of SUP in this vulnerable population. Trial registration ClinicalTrials.gov, NCT03667703. Registered 12 September 2018, https://clinicaltrials.gov/ct2/show/NCT03667703?term=SUPPRESS+CHD&draw=2&rank=1. All WHO Trial Registration Data Set Criteria are met in this manuscript.

TheBurkholderia cepaciacomplex (BCC) is composed of multiple species, includingB. multivoransandB. dolosa,that are significant pathogens for people with cystic fibrosis (CF) and are extensively resistant to many antibiotics. ThefixLgene of thefixLJ2-component system (TCS) in these BCC species shows evidence of positive selection for nonsynonymous mutations during chronic lung infection in CF. Previous work showed that theB. dolosa fixLJsystem regulates 11% of the genome and modulates biofilm formation, motility, persistence within macrophages, and virulence in a murine pneumonia model. Here, we assess the impacts of clinically observed FixL evolved variants infixLJpathway-mediated phenotypes inB. dolosaandB. multivorans.BCC carrying the ancestralfixLsequence are less pathogenic than constructs carrying evolved variants in both a macrophage infection model and a murine pneumonia model.In vitrophospho-transfer experiments demonstrate that the evolvedB. dolosaFixL variants are able to reducefixLJpathway activity by either having lower levels of kinase activity or increased phosphatase activity. Notably, the ancestralfixLgenotype has increased ability to survive within the soil compared to isogenic constructs with evolvedfixLgenotypes, demonstrating that increased virulence comes at an expense. Modulation of the FixLJ system has profound effects on many BCC phenotypes including full pathogenicity, and this modulation is critical for BCC adaptation to the host.

Volatile anesthetics are widely known to be immomodulatory, and may have a significant impact on the progression of disease states. Flagellin is a component of Gram negative bacteria and plays a significant role in the pathophysiology of bacterial pneumonia. Here we found that volatile anesthetics, not intravenous anesthetics, significantly attenuated the activation of TLR5 by flagellin and the release of the neutrophil chemoattract IL-8 from lung epithelial cells. Furthermore, flagellin-induced lung injury was significantly attenuated by volatile anesthetics by inhibiting neutrophil migration to bronchoalveolar space. Docking simulations indicated that volatile anesthetics isoflurane and sevoflurane docked into the interphase of TLR5-flagellin binding. Cystic fibrosis (CF) patients are plagued by Pseudomonas aeruginosa pneumonia, which is facilitated by TLR5-flagellin binding. We clinically validated our findings by retrospectively studying the oxygenation in patients with CF under volatile anesthetic-based anesthesia versus intravenous anesthesia showed that former was associated with significantly higher oxygenation compared to intravenous anesthesia, which suggested a protective effect of volatile anesthetics in this patient population.

Introduction: Suboptimal hand hygiene (HH) remains a significant modifiable cause of healthcare-associated infections in the intensive care unit. We report a single-center, quality improvement project aimed at improving adherence to optimal HH among physicians, nurse practitioners, and nursing staff, and to sustain any improvement over time. Methods: A key driver diagram was developed to identify 5 primary drivers of change: leadership support, education initiatives, patient-family engagement, increased audit frequency, and individual feedback to promote accountability. We examined HH compliance over 3 years in 3 phases (pre-intervention, intervention, and post-intervention). The intervention period involved a multimodal approach designed to influence unit culture as well as individual HH practice. HH screens were installed outside the patient rooms to provide just-in-time reminders and display of regularly updated HH adherence data for provider groups. Results: We recorded 6,563 HH opportunities, providers included nurses (66%), attendings (12%), fellow/resident (16%), and nurse practitioners (NP) (6%). All clinical groups demonstrated HH compliance >90% during the post-intervention period. The improvements in practice were sustained for a year after the intervention. Conclusion: Our report highlights modifiable factors that impact HH and may inform quality improvement interventions aimed at improving HH compliance at other centers.

Despite numerous efforts to develop an effective vaccine against Pseudomonas aeruginosa, no vaccine has yet been approved for human use. This study investigates the utility of the P. aeruginosa inherently produced polyhydroxyalkanaote (PHA) inclusions and associated host–cell proteins (HCP) as a particulate vaccine platform. We further engineered PHA inclusions to display epitopes derived from the outer membrane proteins OprF/OprI/AlgE (Ag) or the type III secretion system translocator PopB. PHA and engineered PHA beads induced antigen-specific humoral, cell-mediated immune responses, anti-HCP and anti-polysaccharide Psl responses in mice. Antibodies mediated opsonophagocytic killing and serotype-independent protective immunity as shown by 100% survival upon challenge with P. aeruginosa in an acute pneumonia murine model. Vaccines were stable at 4 °C for at least one year. Overall, our data suggest that vaccination with subcellular empty PHA beads was sufficient to elicit multiple immune effectors that can prevent P. aeruginosa infection.

OBJECTIVEAdult ventilator-associated event (VAE) definitions include ventilator-associated conditions (VAC) and subcategories for infection-related ventilator-associated complications (IVAC) and possible ventilator-associated pneumonia (PVAP). We explored these definitions for children.DESIGNRetrospective cohortSETTINGPediatric, cardiac, or neonatal intensive care units (ICUs) in 6 US hospitalsPATIENTSPatients ≤18 years old ventilated for ≥1 dayMETHODSWe identified patients with pediatric VAC based on previously proposed criteria. We applied adult temperature, white blood cell count, antibiotic, and culture criteria for IVAC and PVAP to these patients. We matched pediatric VAC patients with controls and evaluated associations with adverse outcomes using Cox proportional hazards models.RESULTSIn total, 233 pediatric VACs (12,167 ventilation episodes) were identified. In the cardiac ICU (CICU), 62.5% of VACs met adult IVAC criteria; in the pediatric ICU (PICU), 54.2% of VACs met adult IVAC criteria; and in the neonatal ICU (NICU), 20.2% of VACs met adult IVAC criteria. Most patients had abnormal white blood cell counts and temperatures; we therefore recommend simplifying surveillance by focusing on “pediatric VAC with antimicrobial use” (pediatric AVAC). Pediatric AVAC with a positive respiratory diagnostic test (“pediatric PVAP”) occurred in 8.9% of VACs in the CICU, 13.3% of VACs in the PICU, and 4.3% of VACs in the NICU. Hospital mortality was increased, and hospital and ICU length of stay and duration of ventilation were prolonged among all pediatric VAE subsets compared with controls.CONCLUSIONSWe propose pediatric AVAC for surveillance related to antimicrobial use, with pediatric PVAP as a subset of AVAC. Studies on generalizability and responsiveness of these metrics to quality improvement initiatives are needed, as are studies to determine whether lower pediatric VAE rates are associated with improvements in other outcomes.Infect Control Hosp Epidemiol 2017;38:327–333

Staphylococcus aureus is an early colonizer in the lungs of individuals with cystic fibrosis (CF), but surprisingly, only a limited number of genomes from CF-associated S. aureus isolates have been sequenced. Here, we present the whole-genome sequences of 65 S. aureus isolates obtained from 50 individuals with CF.

Introduction: We aimed to describe utilization and indication(s) for long-term central venous catheters (CVCs) in a pediatric intensive care unit (PICU) and identify potential strategies to decrease CVC utilization. Methods: We conducted a single-center prospective quality improvement initiative at a 30-bed PICU in a large, freestanding, academic children’s hospital. We created an electronic report to identify patients with an indwelling CVC for 7 days and older (defined as long term). We discussed the ongoing need for each long-term CVC with PICU clinicians at weekly interdisciplinary structured “CVC stewardship rounds.” We then made recommendations around expedited removal of CVCs. We conducted multiple Plan-Do-Study-Act cycles to categorize CVC indications, identify modifiable factors, and educate PICU clinicians. We hypothesized that CVC stewardship rounds would decrease long-term CVC utilization in our PICU. Results: From October 2016 to September 2017, 607 long-term CVCs were eligible for the stewardship intervention. Compared to the preintervention period, we recorded a significant increase in peripherally inserted central catheters and a decrease in nontunneled CVCs (P < 0.001). Most patients had single- or double-lumen CVCs in both the preintervention and intervention periods (86% and 91%, respectively). The utilization of overall long-term CVC devices, and those with modifiable indications, decreased during the intervention period. Conclusions: A single-center QI intervention focused on PICU CVC stewardship was associated with a decrease in CVC utilization.

Probiotics are routinely administered to hospitalized patients for many potential indications

A newly proposed surveillance definition for ventilator-associated conditions among neonatal and pediatric patients has been associated with increased morbidity and mortality among ventilated patients in cardiac ICU, neonatal ICU, and PICU. This study aimed to identify potential risk factors associated with pediatric ventilator-associated conditions.Retrospective cohort.Six U.S. hospitals PATIENTS:: Children less than or equal to 18 years old ventilated for greater than or equal to 1 day.None.We identified children with pediatric ventilator-associated conditions and matched them to children without ventilator-associated conditions. Medical records were reviewed for comorbidities and acute care factors. We used bivariate and multivariate conditional logistic regression models to identify factors associated with ventilator-associated conditions. We studied 192 pairs of ventilator-associated conditions cases and matched controls (113 in the PICU and cardiac ICU combined; 79 in the neonatal ICU). In the PICU/cardiac ICU, potential risk factors for ventilator-associated conditions included neuromuscular blockade (odds ratio, 2.29; 95% CI, 1.08-4.87), positive fluid balance (highest quartile compared with the lowest, odds ratio, 7.76; 95% CI, 2.10-28.6), and blood product use (odds ratio, 1.52; 95% CI, 0.70-3.28). Weaning from sedation (i.e., decreasing sedation) or interruption of sedation may be protective (odds ratio, 0.44; 95% CI, 0.18-1.11). In the neonatal ICU, potential risk factors included blood product use (odds ratio, 2.99; 95% CI, 1.02-8.78), neuromuscular blockade use (odds ratio, 3.96; 95% CI, 0.93-16.9), and recent surgical procedures (odds ratio, 2.19; 95% CI, 0.77-6.28). Weaning or interrupting sedation was protective (odds ratio, 0.07; 95% CI, 0.01-0.79).In mechanically ventilated neonates and children, we identified several possible risk factors associated with ventilator-associated conditions. Next steps include studying propensity-matched cohorts and prospectively testing whether changes in sedation management, transfusion thresholds, and fluid management can decrease pediatric ventilator-associated conditions rates and improve patient outcomes.

Background Methicillin-resistant Staphylococcus aureus (MRSA) is a prevalent pathogen in patients with cystic fibrosis (CF) associated with increased morbidity. Ceftaroline fosamil is an intravenous (IV) cephalosporin with activity against MRSA. There are minimal data regarding dosing in the CF population. The objective of this study was to determine the pharmacokinetic and pharmacodynamic profile of IV ceftaroline in patients with CF. Methods We conducted a single-center prospective study of children and young adults with CF receiving ceftaroline (15mg/kg IV up to 600mg every 8h) as part of treatment for a CF pulmonary exacerbation between June 2016 and April 2017. Seven patients were enrolled for a total of 10 treatment courses. For each treatment course, up to 8 plasma samples were assayed for ceftaroline using ultra-high performance liquid chromatography with mass spectrometry. Maximum plasma concentration, systemic clearance, and elimination half-life were calculated. The area under the curve (AUC) above the minimum inhibitory concentration (MIC) and the percent time above the MIC (%fT>MIC) were determined for each subject using MICs of 0.5, 1, and 2μg/mL and the measured MIC if available. Results The mean (SD) age for the 7 patients was 20.3 (8.0) years. Mean (SD) maximum plasma concentration of ceftaroline was 22.7 (9.6) μg/mL, systemic clearance 7.9 (3.3) L/h, and half-life 1.1 (0.4) hours. Using a MIC of 1 μg/mL, accepted as the MIC 90 of MRSA isolates, AUC above MIC mean (SD) was 53.6 (19.5) μg·h/mL, mean (SD) %fT>MIC was 75.7 (10.4), and all subjects had >60%fT>MIC. Conclusions In this cohort of CF patients, mean ceftaroline half-life was 1.1h, which is notably lower than the general population. The dosing regimen studied, which exceeds the recommended dosing in the non-CF population, was adequate to achieve >60% time above the MIC in all patients.

Objectives To determine whether incident detection of Stenotrophomonas maltophilia (SM) in patients with cystic fibrosis (CF) is associated with accelerated lung function decline and increased hospitalizations and to determine whether this effect is more pronounced in individuals with subsequent chronic infection. Methods We performed a longitudinal, retrospective single-center, pre-post study of 88 patients with CF, ages 6–51 years, with first positive respiratory culture for SM between 2008 and 2014. Rate of decline in FEV1 and hospitalization rates prior to and following incident SM infection were analyzed using segmented regression analysis of interrupted time series. Results Mean (SD) age was 17.4 (9.2) years and the mean (SD) FEV1 % predicted at acquisition was 90.0% (25.2). A total of 44% developed chronic SM infection. In regression analysis adjusted for clinical and demographic factors, there was worsening of the mean annual decline in FEV1 % predicted from −1.79 (95%CI: −2.43, −1.15) pre-acquisition to −2.14 (95%CI: −2.61, −1.67) post-acquisition (P = 0.005). A significant change was observed in those with either subsequent intermittent or chronic infection. The mean annual hospitalization rate increased significantly in the subgroup with chronic infection from 0.46 (95%CI: 0.33, 0.60) to 0.88 (95%CI: 0.68, 1.07) (P = 0.007). Conclusions In this single-center cohort, acquisition of SM in CF was associated with an acceleration in lung function decline. Among those with chronic colonization, acquisition was also associated with increased hospitalization rates.

Burkholderia dolosa is a member of the Burkholderia cepacia complex (BCC), which is a group of bacteria that cause chronic lung infection in patients with cystic fibrosis (CF) and can be associated with outbreaks carrying high morbidity and mortality. While investigating the genomic diversity of B. dolosa strains collected from an outbreak among CF patients, we previously identified fixL as a gene showing signs of strong positive selection. This gene has homology to fixL of the rhizobial FixL/FixJ two-component system. The goals of this study were to determine the functions of FixLJ and their role in virulence in B. dolosa. We generated a fixLJ deletion mutant and complemented controls in B. dolosa strain AU0158. Using a fixK-lacZ reporter we found that FixLJ was activated in low oxygen in multiple BCC species. In a murine pneumonia model, the B. dolosa fixLJ deletion mutant was cleared faster from the lungs and spleen than wild-type B. dolosa strain AU0158 at 7 days post infection. Interestingly, the fixLJ deletion mutant made more biofilm, albeit with altered structure, but was less motile than strain AU0158. Using RNA-seq with in vitro grown bacteria, we found ~11% of the genome was differentially expressed in the fixLJ deletion mutant relative to strain AU0158. Multiple flagella-associated genes were down-regulated in the fixLJ deletion mutant, so we also evaluated virulence of a fliC deletion mutant, which lacks a flagellum. We saw no difference in the ability of the fliC deletion mutant to persist in the murine model relative to strain AU0158, suggesting factors other than flagella caused the phenotype of decreased persistence. We found the fixLJ deletion mutant to be less invasive in human lung epithelial and macrophage-like cells. In conclusion, B. dolosa fixLJ is a global regulator that controls biofilm formation, motility, intracellular invasion/persistence, and virulence., Author Summary In people with cystic fibrosis (CF), infection with bacteria in the Burkholderia cepacia complex (BCC) is often associated with clinical deterioration. In a whole-genome sequencing study of the BCC species B. dolosa, we previously identified the fixL gene of the FixL/FixJ two-component system called FixLJ to be under strong positive selective pressure during chronic infection. In this study we show that low oxygen levels activate FixLJ, and that a mutant of B. dolosa in which the fixLJ genes are deleted is less able to persist in the lungs and spread to the spleen in a lung infection model in mice. The fixLJ deletion mutant has defective motility and intracellular survival within epithelial cells and macrophage cell lines. However, a flagella mutant is fully infectious, suggesting that low motility is not responsible for the fixLJ deletion mutant’s inability to persist within the host. Analysis of global RNA expression shows that the fixLJ system regulates many genes, indicating that multiple pathways likely contribute to the low virulence of the fixLJ deletion mutant. In conclusion, B. dolosa FixLJ compose an oxygen sensor that regulates the ability of the bacteria to survive inside host cells.

Previously published guidelines are available that provide comprehensive recommendations for detecting and preventing healthcare-associated infections (HAIs). The intent of this document is to highlight practical recommendations in a concise format to assist acute care hospitals in implementing and prioritizing strategies to prevent ventilator-associated pneumonia (VAP) and other ventilator-associated events (VAEs) and to improve outcomes for mechanically ventilated adults, children, and neonates. This document updates "Strategies to Prevent Ventilator-Associated Pneumonia in Acute Care Hospitals," published in 2008. This expert guidance document is sponsored by the Society for Healthcare Epidemiology of America (SHEA) and is the product of a collaborative effort led by SHEA, the Infectious Diseases Society of America (IDSA), the American Hospital Association (AHA), the Association for Professionals in Infection Control and Epidemiology (APIC), and The Joint Commission, with major contributions from representatives of a number of organizations and societies with content expertise. The list of endorsing and supporting organizations is presented in the introduction to the 2014 updates.

Despite the recognition of Pseudomonas aeruginosa is an opportunistic pathogen, no vaccine against this bacteria have come to market. This review describes the current state-of-the-art in vaccinology for this bacterium. This includes a discussion of those at risk for infection, the types of vaccines and the approaches for empirical and targeted antigen selection under development, as well as a perspective on where the field should go. In addition, the challenges in developing a vaccine for those individuals at risk are discussed.

Burkholderia dolosa caused an outbreak in the cystic fibrosis (CF) clinic at Boston Children's Hospital from 1998 to 2005 and led to the infection of over 40 patients, many of whom died due to complications from infection by this organism. To assess whether B. dolosa significantly contributes to disease or is recognized by the host immune response, mice were infected with a sequenced outbreak B. dolosa strain, AU0158, and responses were compared to those to the well-studied CF pathogen Pseudomonas aeruginosa . In parallel, mice were also infected with a polar flagellin mutant of B. dolosa to examine the role of flagella in B. dolosa lung colonization. The results showed a higher persistence in the host by B. dolosa strains, and yet, neutrophil recruitment and cytokine production were lower than those with P. aeruginosa . The ability of host immune cells to recognize B. dolosa was then assessed, B. dolosa induced a robust cytokine response in cultured cells, and this effect was dependent on the flagella only when bacteria were dead. Together, these results suggest that B. dolosa can be recognized by host cells in vitro but may avoid or suppress the host immune response in vivo through unknown mechanisms. B. dolosa was then compared to other Burkholderia species and found to induce similar levels of cytokine production despite being internalized by macrophages more than Burkholderia cenocepacia strains. These data suggest that B. dolosa AU0158 may act differently with host cells and is recognized differently by immune systems than are other Burkholderia strains or species.

Enteral nutrition has been implicated as a risk factor for ventilator-associated pneumonia. We explored the prevalence of ventilator-associated pneumonia and its association with clinical and nutrition-related therapies in mechanically ventilated children.Prospective, multicenter, cohort study.Fifty-nine PICU in 15 countries.Children less than 18 years old, mechanically ventilated for more than 48 hours.None. Multivariable logistic regression to determine factors associated with ventilator-associated pneumonia.Data are presented as median (interquartile range) or counts (%). We enrolled 1,245 subjects (45% women; 42% surgical), age 20 months (4-84 mo), and duration of mechanical ventilation 7 days (3-13 d). Culture-positive ventilator-associated pneumonia was diagnosed in 80 patients (6.4%); duration of mechanical ventilation for this subgroup was 17 days (8-39 d). Enteral nutrition was delivered in 985 patients (79%), initiated within 48 hours in 592 patients (60%), and via postpyloric route in 354 patients (36%). Acid-suppressive agents were used in 763 patients (61%). The duration of enteral nutrition (p = 0.21), route (gastric vs postpyloric) of delivery (p = 0.94), severity of illness (p = 0.17), and diagnostic category on admission (p = 0.31) were not associated with ventilator-associated pneumonia. After adjusting for enteral nutrition days, illness severity, and site, ventilator-associated pneumonia was significantly associated with mechanical ventilation more than 10 days (odds ratio, 3.7; 95% CI, 2.2-6.5; p0.001), PICU length of stay more than 10 days (odds ratio, 1.8; 95% CI, 1.1-3.1; p = 0.029), and the use of acid-suppressive medication (odds ratio, 2.0; 95% CI, 1.2-3.6; p = 0.011).Ventilator-associated pneumonia was diagnosed in 6.5% of mechanically ventilated children in a heterogeneous multicenter cohort. We did not find a link between enteral nutrition duration or route of delivery and ventilator-associated pneumonia. In addition to duration of mechanical ventilation and length of PICU stay, the use of acid-suppressive therapy independently increased the likelihood of developing ventilator-associated pneumonia in this population. This association must be further explored in clinical trials.

New vaccine approaches are needed for Pseudomonas aeruginosa, which continues to be a major cause of serious pulmonary infections. Although Th17 cells can protect against gram-negative pathogens at mucosal surfaces, including the lung, the bacterial proteins recognized by Th17 cells are largely unknown and could be potential new vaccine candidates.We describe a strategy to identify Th17-stimulating protein antigens of Pseudomonas aeruginosa to assess their efficacy as vaccines against pneumonia.Using a library of in vitro transcribed and translated P. aeruginosa proteins, we screened for Th17-stimulating antigens by coculturing the library proteins with splenocytes from mice immunized with a live-attenuated P. aeruginosa vaccine that is protective via Th17-based immunity. We measured antibody and Th17 responses after intranasal immunization of mice with the purified proteins mixed with the Th17 adjuvant curdlan, and we tested the protective efficacy of vaccination in a murine model of acute pneumonia.The proteins PopB, FpvA, FptA, OprL, and PilQ elicited strong IL-17 secretion in the screen, and purified versions of PopB, FpvA, and OprL stimulated high IL-17 production from immune splenocytes. Immunization with PopB, which is a highly conserved component of the type III secretion system and a known virulence factor, elicited Th17 responses and also enhanced clearance of P. aeruginosa from the lung and spleen after challenge. PopB-immunized mice were protected from lethal pneumonia in an antibody-independent, IL-17-dependent manner.Screening for Th17-stimulating protein antigens identified PopB as a novel and promising vaccine candidate for P. aeruginosa.

Background. New therapeutic targets for antibiotic-resistant bacterial pathogens are desperately needed. The bacterial surface polysaccharide poly-β-(1-6)-N-acetyl-glucosamine (PNAG) mediates biofilm formation by some bacterial species, and antibodies to PNAG can confer protective immunity. By analyzing sequenced genomes, we found that potentially multidrug-resistant bacterial species such as Klebsiella pneumoniae, Enterobacter cloacae, Stenotrophomonas maltophilia, and the Burkholderia cepacia complex (BCC) may be able to produce PNAG. Among patients with cystic fibrosis patients, highly antibiotic-resistant bacteria in the BCC have emerged as problematic pathogens, providing an impetus to study the potential of PNAG to be targeted for immunotherapy against pan-resistant bacterial pathogens. Methods. The presence of PNAG on BCC was assessed using a combination of bacterial genetics, microscopy, and immunochemical approaches. Antibodies to PNAG were tested using opsonophagocytic assays and for protective efficacy against lethal peritonitis in mice. Results. PNAG is expressed in vitro and in vivo by the BCC, and cystic fibrosis patients infected by the BCC species B. dolosa mounted a PNAG-specific opsonophagocytic antibody response. Antisera to PNAG mediated opsonophagocytic killing of BCC and were protective against lethal BCC peritonitis even during coinfection with methicillin-resistant Staphylococcus aureus. Conclusions. Our findings raise potential new therapeutic options against PNAG-producing bacteria, including even pan-resistant pathogens.

To identify a pediatric ventilator-associated condition definition for use in neonates and children by exploring whether potential ventilator-associated condition definitions identify patients with worse outcomes.Retrospective cohort study and a matched cohort analysis.Pediatric, cardiac, and neonatal ICUs in five U.S. hospitals.Children 18 years old or younger ventilated for at least 1 day.None.We evaluated the evidence of worsening oxygenation via a range of thresholds for increases in daily minimum fraction of inspired oxygen (by 0.20, 0.25, and 0.30) and daily minimum mean airway pressure (by 4, 5, 6, and 7 cm H2O). We required worsening oxygenation be sustained for at least 2 days after at least 2 days of stability. We matched patients with a ventilator-associated condition to those without and used Cox proportional hazard models with frailties to examine associations with hospital mortality, hospital and ICU length of stay, and duration of ventilation. The cohort included 8,862 children with 10,209 hospitalizations and 77,751 ventilator days. For the fraction of inspired oxygen 0.25/mean airway pressure 4 definition (i.e., increase in minimum daily fraction of inspired oxygen by 0.25 or mean airway pressure by 4), rates ranged from 2.9 to 3.2 per 1,000 ventilator days depending on ICU type; the fraction of inspired oxygen 0.30/mean airway pressure 7 definition yielded ventilator-associated condition rates of 1.1-1.3 per 1,000 ventilator days. All definitions were significantly associated with greater risk of hospital death, with hazard ratios ranging from 1.6 (95% CI, 0.7-3.4) to 6.8 (2.9-16.0), depending on thresholds and ICU type. Each definition was associated with prolonged hospitalization, time in ICU, and duration of ventilation, among survivors. The advisory board of the study proposed using the fraction of inspired oxygen 0.25/mean airway pressure 4 thresholds to identify pediatric ventilator-associated conditions in ICUs.Pediatric patients with ventilator-associated conditions are at substantially higher risk for mortality and morbidity across ICUs, regardless of thresholds used. Next steps include identification of risk factors, etiologies, and preventative measures for pediatric ventilator-associated conditions.

Bacterial pathogens evolve during the infection of their human host(1-8), but separating adaptive and neutral mutations remains challenging(9-11). Here we identify bacterial genes under adaptive evolution by tracking recurrent patterns of mutations in the same pathogenic strain during the infection of multiple individuals. We conducted a retrospective study of a Burkholderia dolosa outbreak among subjects with cystic fibrosis, sequencing the genomes of 112 isolates collected from 14 individuals over 16 years. We find that 17 bacterial genes acquired nonsynonymous mutations in multiple individuals, which indicates parallel adaptive evolution. Mutations in these genes affect important pathogenic phenotypes, including antibiotic resistance and bacterial membrane composition and implicate oxygen-dependent regulation as paramount in lung infections. Several genes have not previously been implicated in pathogenesis and may represent new therapeutic targets. The identification of parallel molecular evolution as a pathogen spreads among multiple individuals points to the key selection forces it experiences within human hosts.

Many animal studies investigating adaptive immune effectors important for protection against Pseudomonas aeruginosa have implicated opsonic antibody to the antigenically variable lipopolysaccharide (LPS) O antigens as a primary effector. However, active and passive vaccination of humans against these antigens has not shown clinical efficacy. We hypothesized that optimal immunity would require inducing multiple immune effectors targeting multiple bacterial antigens. Therefore, we evaluated a multivalent live-attenuated mucosal vaccination strategy in a murine model of acute P. aeruginosa pneumonia to assess the contributions to protective efficacy of various bacterial antigens and host immune effectors. Vaccines combining 3 or 4 attenuated strains having different LPS serogroups were associated with the highest protective efficacy compared to vaccines with fewer components. Levels of opsonophagocytic antibodies, which were directed not only to the LPS O antigens but also to the LPS core and surface proteins, correlated with protective immunity. The multivalent live-attenuated vaccines overcame prior problems involving immunologic interference in the development of O-antigen-specific antibody responses when closely related O antigens were combined in multivalent vaccines. Antibodies to the LPS core were associated with in vitro killing and in vivo protection against strains with O antigens not expressed by the vaccine strains, whereas antibodies to the LPS core and surface proteins augmented the contribution of O-antigen-specific antibodies elicited by vaccine strains containing a homologous O antigen. Local CD4 T cells in the lung also contributed to vaccine-based protection when opsonophagocytic antibodies to the challenge strain were absent. Thus, multivalent live-attenuated vaccines elicit multifactorial protective immunity to P. aeruginosa lung infections.

Burkholderia dolosa caused an outbreak in the cystic fibrosis clinic at Boston Children's Hospital and was associated with high mortality in these patients. This species is part of a larger complex of opportunistic pathogens known as the Burkholderia cepacia complex (Bcc). Compared to other species in the Bcc, B. dolosa is highly transmissible; thus understanding its virulence mechanisms is important for preventing future outbreaks. The genome of one of the outbreak strains, AU0158, revealed a homolog of the lafA gene encoding a putative lateral flagellin, which, in other non-Bcc species, is used for movement on solid surfaces, attachment to host cells, or movement inside host cells. Here, we analyzed the conservation of the lafA gene and protein sequences, which are distinct from those of the polar flagella, and found lafA homologs to be present in numerous β-proteobacteria but notably absent from most other Bcc species. A lafA deletion mutant in B. dolosa showed a greater swimming motility than wild-type due to an increase in the number of polar flagella, but did not appear to contribute to biofilm formation, host cell invasion, or murine lung colonization or persistence over time. However, the lafA gene was important for cytokine production in human peripheral blood mononuclear cells, suggesting it may have a role in recognition by the human immune response.

Pseudomonas aeruginosa is a leading cause of pneumonia, and many components of the innate immune system have been proposed to exert important effects in preventing lung infection. However, a vigorous experimental system to identify an overriding, key effector mediating innate immunity to lung infection has not been utilized. As many of the important components of innate immunity are involved in recruitment and activation of polymorphonuclear neutrophils (PMNs) to infected tissues, we hypothesized that the cells and factors needed for their proper recruitment to the lung comprised the major mediators of innate immunity. In neutropenic mice, intranasal (i.n.) doses of P. aeruginosa as low as 10 to 100 CFU/mouse produced a fatal lung infection, compared with 10 7 to >10 8 CFU for nonneutropenic mice. There was only a very modest increased mortality in mice lacking mature lymphocytes and no increased mortality in mice depleted of alveolar macrophages when administered i.n. P. aeruginosa . Recombinant mouse granulocyte colony-stimulating factor increased survival of neutropenic mice after i.n. P. aeruginosa inoculation. MyD88 −/− mice, which cannot recruit PMNs to the lungs, were highly susceptible to fatal P. aeruginosa lung infection, with bacterial doses of −/− mice resulted in enhanced protection against P. aeruginosa lung infection. Overall, in the absence of PMNs, mice cannot resist P. aeruginosa lung infection from extremely small bacterial doses. There is an inescapable requirement for local PMN recruitment and activation to mediate innate immunity to P. aeruginosa lung infection.

In a murine model of acute fatal pneumonia, we previously showed that nasal immunization with a live-attenuated aroA deletant of Pseudomonas aeruginosa strain PAO1 elicited LPS serogroup-specific protection, indicating that opsonic Ab to the LPS O Ag was the most important immune effector. Because P. aeruginosa strain PA14 possesses additional virulence factors, we hypothesized that a live-attenuated vaccine based on PA14 might elicit a broader array of immune effectors. Thus, an aroA deletant of PA14, denoted PA14ΔaroA, was constructed. PA14ΔaroA-immunized mice were protected against lethal pneumonia caused not only by the parental strain but also by cytotoxic variants of the O Ag-heterologous P. aeruginosa strains PAO1 and PAO6a,d. Remarkably, serum from PA14ΔaroA-immunized mice had very low levels of opsonic activity against strain PAO1 and could not passively transfer protection, suggesting that an antibody-independent mechanism was needed for the observed cross-serogroup protection. Compared with control mice, PA14ΔaroA-immunized mice had more rapid recruitment of neutrophils to the airways early after challenge. T cells isolated from P. aeruginosa ΔaroA-immunized mice proliferated and produced IL-17 in high quantities after coculture with gentamicin-killed P. aeruginosa. Six hours following challenge, PA14ΔaroA-immunized mice had significantly higher levels of IL-17 in bronchoalveolar lavage fluid compared with unimmunized, Escherichia coli-immunized, or PAO1ΔaroA-immunized mice. Antibody-mediated depletion of IL-17 before challenge or absence of the IL-17 receptor abrogated the PA14ΔaroA vaccine’s protection against lethal pneumonia. These data show that IL-17 plays a critical role in antibody-independent vaccine-induced protection against LPS-heterologous strains of P. aeruginosa in the lung.

Neutrophil serine proteases (NSPs; elastase, cathepsin G, and proteinase-3) directly kill invading microbes. However, excess NSPs in the lungs play a central role in the pathology of inflammatory pulmonary disease. We show that serpinb1, an efficient inhibitor of the three NSPs, preserves cell and molecular components responsible for host defense against Pseudomonas aeruginosa. On infection, wild-type (WT) and serpinb1-deficient mice mount similar early responses, including robust production of cytokines and chemokines, recruitment of neutrophils, and initial containment of bacteria. However, serpinb1−/− mice have considerably increased mortality relative to WT mice in association with late-onset failed bacterial clearance. We found that serpinb1-deficient neutrophils recruited to the lungs have an intrinsic defect in survival accompanied by release of neutrophil protease activity, sustained inflammatory cytokine production, and proteolysis of the collectin surfactant protein–D (SP-D). Coadministration of recombinant SERPINB1 with the P. aeruginosa inoculum normalized bacterial clearance in serpinb1−/− mice. Thus, regulation of pulmonary innate immunity by serpinb1 is nonredundant and is required to protect two key components, the neutrophil and SP-D, from NSP damage during the host response to infection.