Surgical Urgency, Patient Comorbidities, and Socioeconomic Factors in Surgical Site Infections in Pediatric Surgery.

BACKGROUND: The rise of value-based purchasing has led to decreased compensation for hospital-acquired conditions, including surgical site infections (SSI). This study aims to assess the risk factors for SSI in children and teenagers undergoing gastrointestinal surgery across US hospitals. METHODS: The 2018-2020 Nationwide Readmissions Database was queried for patients undergoing gastrointestinal surgery under the age of 18. The primary outcome was SSI during index admission or readmission within a year. Comparison groups were elective, trauma, and emergent surgery based on anatomic location and urgency. Univariable comparison used chi-squared tests for relevant variables. Confounders were addressed through multivariable logistic regression with significant variables from univariable analysis. RESULTS: 113 108 total patients met the study criteria. The SSI rate during admission or readmission was 2.9% (n = 3254). Infections during admission and readmission were 1.4% (n = 1560) and 1.5% (n = 1694), respectively. The most common site was organ space (48.6%, n = 1657). Increased infection risk was associated with trauma (OR 1.80 [1.51-2.16] P < .001), emergency surgery (OR 1.31 [1.17-1.47] P < .001), large bowel surgery (OR 2.78 [2.26-3.43] P < .001), and those with three or more comorbidities (OR 2.03 [1.69-2.45] P < .001). Investor-owned hospitals (OR .65 [.56-.76] P < .001) and highest quartile income (OR .80 [.73-.88] P < .001) were associated with decreased infection risk. CONCLUSIONS: Pediatric patients undergoing gastrointestinal surgery face an elevated risk of SSI, especially in trauma and emergency surgeries, particularly with multiple comorbidities. Meanwhile, a reduced risk is observed in high-income and investor-owned hospital settings. Hospitals and surgeons caring for high risk patients should advocate for risk adjustment in value-based payment systems.

Venous Thromboembolism in Children and Teenagers Admitted for Trauma: A 5-Year Nationwide Perspective.

Venous thromboembolism (VTE) in pediatric trauma patients is under-investigated. The purpose of this study was to perform an evaluation of the risk factors for VTE after pediatric trauma, including readmissions across the United States. The Nationwide Readmissions Database for 2016-2020 was queried for all patients under the age of 18 years admitted for trauma. 276 670 patients were identified; 2063 (.8%) were diagnosed with VTE. Among those with VTE, 300 (15%) were identified during a readmission. Higher rates of VTE were seen in ages 15-17 years (n = 1,294, 1.3%, P < .001), penetrating injuries (n = 478, .9%, P < .001), and assault (n = 271, 2.7%, P < .001). The strongest risk factor for VTE was prolonged mechanical ventilation (OR 5.5 [4.9-6.3] P < .001). Our study found that a significant portion of post-traumatic VTE in children and teenagers occur during readmissions. A deeper understanding of the risk factors outlined here can guide enhanced clinical protocols, ensuring early detection and prevention of this complication.

Optimizing Triage Practice in Pediatric Trauma: Lessons From Under-triage and Over-triage Rates and Risk Factors.

BACKGROUND: Triage accuracy is essential for delivering effective trauma care, especially in the pediatric population where unique challenges exist. The purpose of this study was to investigate risk factors contributing to under-triage and over-triage in an urban pediatric trauma center. METHODS: This retrospective cohort study included all trauma activations at an urban level 1 trauma center between January 1, 2021, and July 31, 2023 (patients <18 years old.) Patients who were under- or over-triaged were identified based on the level of trauma activation and injury severity score. RESULTS: There were 1094 trauma activations included in this study. The rate of under-triage was 3.8% (n = 42) and over-triage was 13.6% (n = 149). Infants aged 0-1 years had the highest rate of under-triage (10.9%, n = 19, P < .001), while those aged 11-17 had the highest rate of over-triage (17.0%, n = 82, P = .003). Non-accidental trauma was the strongest risk factor for under-triage (OR 30.2 [6.4-142.8] P < .001). Penetrating mechanism was the strongest risk factor for over-triage (OR 12.2 [5.6-26.2] P < .001). DISCUSSION: This study reveals the complexity of trauma triage in the pediatric population. We identified key predictive factors, such as age, comorbidities, and mechanism of injury, that can be used to refine triage practices and improve the care of pediatric trauma patients.

Nationwide Propensity-Matched Comparison of Surgical Site Infections in Safety Net Hospitals.

This cohort study examines the rates and risks associated with surgical site infection during admission or readmission of socioeconomically marginalized patients undergoing gastrointestinal surgery.

Chemoembolization Versus Radioembolization for Neuroendocrine Liver Metastases: A Meta-analysis Comparing Clinical Outcomes.

BACKGROUND: Studies have shown intra-arterial therapies to be effective in controlling neuroendocrine liver metastases (NELMs), but the evidence supporting the selection of specific methods is limited. This meta-analysis is the first to compare survival outcomes between transarterial chemoembolization (TACE) and transarterial radioembolization (TARE) in the treatment of NELM. METHODS: A systematic search according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines in PubMed and Embase databases was conducted in February 2020 for published studies comparing survival outcomes between TACE and TARE in the treatment of NELM. RESULTS: Six eligible cohort studies with a total of 643 patients were identified. The TACE and TARE groups were similar in terms of age, sex, hepatic tumor burden, tumor grade, and Eastern Cooperative Oncology Group (ECOG) score. The patients treated with TACE had significantly better overall survival (odds ratio [OR], 1.92; 95% confidence interval [CI] 1.14-3.22, p = 0.014) than those treated with TARE. Overall survival ranged from 16.8 to 81.9 months with TACE and from 14.5 to 66.8 months with TARE. No significant differences in hepatic progression-free survival (OR, 1.01; 95% CI 0.75-1.35; p = 0.96) or tumor response were observed within the first 3 months (OR, 2.87; 95% CI 0.81-10.21; p = 0.10) or thereafter (OR, 0.98; 95% CI 0.12-7.86; p = 0.99). The complication rates were similar between the two groups, with 6.9% of the TACE patients versus 8.5% of TARE patients reporting major complications (OR, 1.16; 95% CI 0.54-2.48; p = 0.71) and respectively 44.6% and 58.8% of the TACE and TARE patients reporting minor adverse events (OR, 1.08; 95% CI 0.39-2.99; p = 0.88). CONCLUSIONS: Despite similar tumor responses, an overall survival benefit was associated with TACE treatment of NELM compared with TARE treatment. Randomized controlled trials are warranted to confirm this finding and clarify whether certain subpopulations benefit from different transarterial methods.

Group B streptococcus exploits vaginal epithelial exfoliation for ascending infection.

Thirteen percent of pregnancies result in preterm birth or stillbirth, accounting for fifteen million preterm births and three and a half million deaths annually. A significant cause of these adverse pregnancy outcomes is in utero infection by vaginal microorganisms. To establish an in utero infection, vaginal microbes enter the uterus by ascending infection; however, the mechanisms by which this occurs are unknown. Using both in vitro and murine models of vaginal colonization and ascending infection, we demonstrate how a vaginal microbe, group B streptococcus (GBS), which is frequently associated with adverse pregnancy outcomes, uses vaginal exfoliation for ascending infection. GBS induces vaginal epithelial exfoliation by activation of integrin and ß-catenin signaling. However, exfoliation did not diminish GBS vaginal colonization as reported for other vaginal microbes. Rather, vaginal exfoliation increased bacterial dissemination and ascending GBS infection, and abrogation of exfoliation reduced ascending infection and improved pregnancy outcomes. Thus, for some vaginal bacteria, exfoliation promotes ascending infection rather than preventing colonization. Our study provides insight into mechanisms of ascending infection by vaginal microbes.

Diminished Capsule Exacerbates Virulence, Blood-Brain Barrier Penetration, Intracellular Persistence, and Antibiotic Evasion of Hyperhemolytic Group B Streptococci.

Group B streptococci (GBS) are encapsulated, ß-hemolytic bacteria that are a common cause of infections in human newborns and certain adults. Two factors important for GBS virulence are the sialic acid capsular polysaccharide that promotes immune evasion and the hemolytic pigment that induces host cell cytotoxcity. These virulence factors are often oppositely regulated by the CovR/CovS two-component system. Clinical GBS strains exhibiting hyperhemolysis and low capsule due to pathoadaptive covR/S mutations have been isolated from patients. Given the importance of capsule to GBS virulence, we predicted that a decrease or loss of capsule would attenuate the virulence of covR/S mutants. Surprisingly, hyperhemolytic GBS with low or no capsule exhibit increased virulence, intracellular persistence, and blood-brain barrier penetration, which was independent of a Trojan horse mechanism of barrier penetration. Additionally, intracellular persistence enabled both hemolytic and hyperhemolytic GBS to evade antibiotics routinely used to treat these infections. The finding that diminished capsule expression promotes GBS virulence, intracellular persistence, and antibiotic evasion has important implications for sustained antibiotic therapy and efficacy of capsule-based vaccines.

Group B Streptococcus circumvents neutrophils and neutrophil extracellular traps during amniotic cavity invasion and preterm labor.

Preterm birth is a leading cause of neonatal morbidity and mortality. Although microbial invasion of the amniotic cavity (MIAC) is associated with the majority of early preterm births, the temporal events that occur during MIAC and preterm labor are not known. Group B Streptococci (GBS) are ß-hemolytic, gram-positive bacteria, which commonly colonize the vagina but have been recovered from the amniotic fluid in preterm birth cases. To understand temporal events that occur during MIAC, we utilized a unique chronically catheterized nonhuman primate model that closely emulates human pregnancy. This model allows monitoring of uterine contractions, timing of MIAC and immune responses during pregnancy-associated infections. Here, we show that adverse outcomes such as preterm labor, MIAC, and fetal sepsis were observed more frequently during infection with hemolytic GBS when compared to nonhemolytic GBS. Although MIAC was associated with systematic progression in chorioamnionitis beginning with chorionic vasculitis and progressing to neutrophilic infiltration, the ability of the GBS hemolytic pigment toxin to induce neutrophil cell death and subvert killing by neutrophil extracellular traps (NETs) in placental membranes in vivo facilitated MIAC and fetal injury. Furthermore, compared to maternal neutrophils, fetal neutrophils exhibit decreased neutrophil elastase activity and impaired phagocytic functions to GBS. Collectively, our studies demonstrate how a unique bacterial hemolytic lipid toxin enables GBS to circumvent neutrophils and NETs in placental membranes to induce fetal injury and preterm labor.

Bacterial Hyaluronidase Promotes Ascending GBS Infection and Preterm Birth.

UNLABELLED: Preterm birth increases the risk of adverse birth outcomes and is the leading cause of neonatal mortality. A significant cause of preterm birth is in utero infection with vaginal microorganisms. These vaginal microorganisms are often recovered from the amniotic fluid of preterm birth cases. A vaginal microorganism frequently associated with preterm birth is group B streptococcus (GBS), or Streptococcus agalactiae However, the molecular mechanisms underlying GBS ascension are poorly understood. Here, we describe the role of the GBS hyaluronidase in ascending infection and preterm birth. We show that clinical GBS strains associated with preterm labor or neonatal infections have increased hyaluronidase activity compared to commensal strains obtained from rectovaginal swabs of healthy women. Using a murine model of ascending infection, we show that hyaluronidase activity was associated with increased ascending GBS infection, preterm birth, and fetal demise. Interestingly, hyaluronidase activity reduced uterine inflammation but did not impact placental or fetal inflammation. Our study shows that hyaluronidase activity enables GBS to subvert uterine immune responses, leading to increased rates of ascending infection and preterm birth. These findings have important implications for the development of therapies to prevent in utero infection and preterm birth. IMPORTANCE: GBS are a family of bacteria that frequently colonize the vagina of pregnant women. In some cases, GBS ascend from the vagina into the uterine space, leading to fetal injury and preterm birth. Unfortunately, little is known about the mechanisms underlying ascending GBS infection. In this study, we show that a GBS virulence factor, HylB, shows higher activity in strains isolated from cases of preterm birth than those isolates from rectovaginal swabs of healthy women. We discovered that GBS rely on HylB to avoid immune detection in uterine tissue, but not placental tissue, which leads to increased rates of fetal injury and preterm birth. These studies provide novel insight into the underlying mechanisms of ascending infection.

Mast cell degranulation by a hemolytic lipid toxin decreases GBS colonization and infection.

Ascending infection of microbes from the lower genital tract into the amniotic cavity increases the risk of preterm birth, stillbirth, and newborn infections. Host defenses that are critical for preventing ascending microbial infection are not completely understood. Group B Streptococcus (GBS) are Gram-positive bacteria that frequently colonize the lower genital tract of healthy women but cause severe infections during pregnancy, leading to preterm birth, stillbirth, or early-onset newborn infections. We recently described that the GBS pigment is hemolytic, and increased pigment expression promotes GBS penetration of human placenta. Here, we show that the GBS hemolytic pigment/lipid toxin and hyperpigmented GBS strains induce mast cell degranulation, leading to the release of preformed and proinflammatory mediators. Mast cell-deficient mice exhibit enhanced bacterial burden, decreased neutrophil mobilization, and decreased immune responses during systemic GBS infection. In a vaginal colonization model, hyperpigmented GBS strains showed increased persistence in mast cell-deficient mice compared to mast cell-proficient mice. Consistent with these observations, fewer rectovaginal GBS isolates from women in their third trimester of pregnancy were hyperpigmented/hyperhemolytic. Our work represents the first example of a bacterial hemolytic lipid that induces mast cell degranulation and emphasizes the role of mast cells in limiting genital colonization by hyperpigmented GBS.

Uterine overdistention induces preterm labor mediated by inflammation: observations in pregnant women and nonhuman primates.

OBJECTIVE: Uterine overdistention is thought to induce preterm labor in women with twin and multiple pregnancies, but the pathophysiology remains unclear. We investigated for the first time the pathogenesis of preterm birth associated with rapid uterine distention in a pregnant nonhuman primate model. STUDY DESIGN: A nonhuman primate model of uterine overdistention was created using preterm chronically catheterized pregnant pigtail macaques (Macaca nemestrina) by inflation of intraamniotic balloons (N = 6), which were compared to saline controls (N = 5). Cesarean delivery was performed due to preterm labor or at experimental end. Microarray, quantitative reverse transcriptase polymerase chain reaction, Luminex (Austin, TX), and enzyme-linked immunosorbent assay were used to measure messenger RNA (mRNA) and/or protein levels from monkey (amniotic fluid, myometrium, maternal plasma) and human (amniocytes, amnion, myometrium) tissues. Statistical analysis employed analysis of covariance and Wilcoxon rank sum. Biomechanical forces were calculated using the law of Laplace. RESULTS: Preterm labor occurred in 3 of 6 animals after balloon inflation and correlated with greater balloon volume and uterine wall stress. Significant elevations of inflammatory cytokines and prostaglandins occurred following uterine overdistention in an "inflammatory pulse" that correlated with preterm labor (interleukin [IL]-1ß, tumor necrosis factor [TNF]-α, IL-6, IL-8, CCL2, prostaglandin E2, prostaglandin F2α, all P < .05). A similar inflammatory response was observed in amniocytes in vitro following mechanical stretch (IL1ß, IL6, and IL8 mRNA multiple time points, P < .05), in amnion of women with polyhydramnios (IL6 and TNF mRNA, P < .05) and in amnion (TNF-α) and myometrium of women with twins in early labor (IL6, IL8, CCL2, all P < .05). Genes differentially expressed in the nonhuman primate after balloon inflation and in women with polyhydramnios and twins are involved in tissue remodeling and muscle growth. CONCLUSION: Uterine overdistention by inflation of an intraamniotic balloon is associated with an inflammatory pulse that precedes and correlates with preterm labor. Our results indicate that inflammation is an early event after a mechanical stress on the uterus and leads to preterm labor when the stress is sufficiently great. Further, we find evidence of uterine tissue remodeling and muscle growth as a common, perhaps compensatory, response to uterine distension.

A streptococcal lipid toxin induces membrane permeabilization and pyroptosis leading to fetal injury.

Group B streptococci (GBS) are Gram-positive bacteria that cause infections in utero and in newborns. We recently showed that the GBS pigment is hemolytic and increased pigment production promotes bacterial penetration of human placenta. However, mechanisms utilized by the hemolytic pigment to induce host cell lysis and the consequence on fetal injury are not known. Here, we show that the GBS pigment induces membrane permeability in artificial lipid bilayers and host cells. Membrane defects induced by the GBS pigment trigger K(+) efflux leading to osmotic lysis of red blood cells or pyroptosis in human macrophages. Macrophages lacking the NLRP3 inflammasome recovered from pigment-induced cell damage. In a murine model of in utero infection, hyperpigmented GBS strains induced fetal injury in both an NLRP3 inflammasome-dependent and NLRP3 inflammasome-independent manner. These results demonstrate that the dual mechanism of action of the bacterial pigment/lipid toxin leading to hemolysis or pyroptosis exacerbates fetal injury and suggest that preventing both activities of the hemolytic lipid is likely critical to reduce GBS fetal injury and preterm birth.

A multicenter outcomes analysis of children with severe rhino/enteroviral respiratory infection.

OBJECTIVES: To investigate the impact of human rhino/enteroviruses on morbidity and mortality outcomes in children with severe viral respiratory infection. DESIGN: Retrospective cohort study. SETTING: The ICU, either PICU or cardiac ICU, at three urban academic tertiary-care children's hospitals. PATIENTS: All patients with laboratory-confirmed human rhino/enteroviruses infection between January 2010 and June 2011. INTERVENTIONS: We captured demographic and clinical data and analyzed associated morbidity and mortality outcomes. MEASUREMENTS AND MAIN RESULTS: There were 519 patients included in our analysis. The median patient age was 2.7 years. The median hospital and ICU lengths of stay were 4 days and 2 days, respectively. Thirty-four percent of patients had a history of asthma, and 25% of patients had a chronic medical condition other than asthma. Thirty-two percent of patients required mechanical ventilation. Eleven patients (2.1%) did not survive to hospital discharge. The rate of viral coinfection was 12.5% and was not associated with mortality. Predisposing factors associated with increased mortality included immunocompromised state (p < 0.001), ICU admission severity of illness score (p < 0.001), and bacterial coinfection (p = 0.003). CONCLUSIONS: There is substantial morbidity associated with severe respiratory infection due to human rhino/enteroviruses in children. Mortality was less severe than reported in other respiratory viruses such as influenza and respiratory syncytial virus. The burden of illness from human rhino/enteroviruses in the ICU in terms of resource utilization may be considerable.

The sensor histidine kinase RgfC affects group B streptococcal virulence factor expression independent of its response regulator RgfA.

Group B streptococci (GBS; Streptococcus agalactiae) are beta-hemolytic, Gram-positive bacteria that are common asymptomatic colonizers of healthy adults. However, these opportunistic bacteria also cause invasive infections in human newborns and in certain adult populations. To adapt to the various environments encountered during its disease cycle, GBS encodes a number of two-component signaling systems. Previous studies have indicated that the TCS comprising the sensor histidine kinase RgfC and the response regulator RgfA mediate GBS binding to extracellular matrix components, such as fibrinogen. However, in certain GBS clinical isolates, a point mutation in rgfA results in premature truncation of the response regulator. The truncated RgfA protein lacks the C-terminal DNA binding domain necessary for promoter binding and gene regulation. Here, we show that deletion of rgfC in GBS strains lacking a functional RgfA increased systemic infection. Furthermore, infection with the rgfC mutant increased induction of proinflammatory signaling pathways in vivo. Phosphoproteomic analysis revealed that 19 phosphopeptides corresponding to 12 proteins were differentially phosphorylated at aspartate, cysteine, serine, threonine, or tyrosine residues in the rgfC mutant. This included aspartate phosphorylation of a tyrosine kinase, CpsD, and a transcriptional regulator. Consistent with this observation, microarray analysis of the rgfC mutant indicated that >200 genes showed altered expression compared to the isogenic wild-type strain and included transcriptional regulators, transporters, and genes previously associated with GBS pathogenesis. Our observations suggest that in the absence of RgfA, nonspecific RgfC signaling affects the expression of virulence factors and GBS pathogenesis.

Inflammatory monocytes mediate early and organ-specific innate defense during systemic candidiasis.

Candida albicans is a commensal fungus that can cause systemic disease in patients with breaches in mucosal integrity, indwelling catheters, and defects in phagocyte function. Although circulating human and murine monocytes bind C. albicans and promote inflammation, it remains unclear whether C-C chemokine receptor 2 (CCR2)- and Ly6C-expressing inflammatory monocytes exert a protective or a deleterious function during systemic infection. During murine systemic candidiasis, interruption of CCR2-dependent inflammatory monocyte trafficking into infected kidneys impaired fungal clearance and decreased murine survival. Depletion of CCR2-expressing cells led to uncontrolled fungal growth in the kidneys and brain and demonstrated an essential antifungal role for inflammatory monocytes and their tissue-resident derivatives in the first 48 hours postinfection. Adoptive transfer of purified inflammatory monocytes in depleted hosts reversed the defect in fungal clearance to a substantial extent, indicating a compartmentally and temporally restricted protective function that can be transferred to enhance systemic innate antifungal immunity.

A hemolytic pigment of Group B Streptococcus allows bacterial penetration of human placenta.

Microbial infection of the amniotic fluid is a significant cause of fetal injury, preterm birth, and newborn infections. Group B Streptococcus (GBS) is an important human bacterial pathogen associated with preterm birth, fetal injury, and neonatal mortality. Although GBS has been isolated from amniotic fluid of women in preterm labor, mechanisms of in utero infection remain unknown. Previous studies indicated that GBS are unable to invade human amniotic epithelial cells (hAECs), which represent the last barrier to the amniotic cavity and fetus. We show that GBS invades hAECs and strains lacking the hemolysin repressor CovR/S accelerate amniotic barrier failure and penetrate chorioamniotic membranes in a hemolysin-dependent manner. Clinical GBS isolates obtained from women in preterm labor are hyperhemolytic and some are associated with covR/S mutations. We demonstrate for the first time that hemolytic and cytolytic activity of GBS is due to the ornithine rhamnolipid pigment and not due to a pore-forming protein toxin. Our studies emphasize the importance of the hemolytic GBS pigment in ascending infection and fetal injury.

Hypoxia enhances innate immune activation to Aspergillus fumigatus through cell wall modulation.

Infection by the human fungal pathogen Aspergillus fumigatus induces hypoxic microenvironments within the lung that can alter the course of fungal pathogenesis. How hypoxic microenvironments shape the composition and immune activating potential of the fungal cell wall remains undefined. Herein we demonstrate that hypoxic conditions increase the hyphal cell wall thickness and alter its composition particularly by augmenting total and surface-exposed ß-glucan content. In addition, hypoxia-induced cell wall alterations increase macrophage and neutrophil responsiveness and antifungal activity as judged by inflammatory cytokine production and ability to induce hyphal damage. We observe that these effects are largely dependent on the mammalian ß-glucan receptor dectin-1. In a corticosteroid model of invasive pulmonary aspergillosis, A. fumigatus ß-glucan exposure correlates with the presence of hypoxia in situ. Our data suggest that hypoxia-induced fungal cell wall changes influence the activation of innate effector cells at sites of hyphal tissue invasion, which has potential implications for therapeutic outcomes of invasive pulmonary aspergillosis.

Tracing conidial fate and measuring host cell antifungal activity using a reporter of microbial viability in the lung.

Fluorescence can be harnessed to monitor microbial fate and to investigate functional outcomes of individual microbial cell-host cell encounters at portals of entry in native tissue environments. We illustrate this concept by introducing fluorescent Aspergillus reporter (FLARE) conidia that simultaneously report phagocytic uptake and fungal viability during cellular interactions with the murine respiratory innate immune system. Our studies using FLARE conidia reveal stepwise and cell-type-specific requirements for CARD9 and Syk, transducers of C-type lectin receptor and integrin signals, in neutrophil recruitment, conidial uptake, and conidial killing in the lung. By achieving single-event resolution in defined leukocyte populations, the FLARE method enables host cell profiling on the basis of pathogen uptake and killing and may be extended to other pathogens in diverse model host organisms to query molecular, cellular, and pharmacologic mechanisms that shape host-microbe interactions.

In vivo hypoxia and a fungal alcohol dehydrogenase influence the pathogenesis of invasive pulmonary aspergillosis.

Currently, our knowledge of how pathogenic fungi grow in mammalian host environments is limited. Using a chemotherapeutic murine model of invasive pulmonary aspergillosis (IPA) and (1)H-NMR metabolomics, we detected ethanol in the lungs of mice infected with Aspergillus fumigatus. This result suggests that A. fumigatus is exposed to oxygen depleted microenvironments during infection. To test this hypothesis, we utilized a chemical hypoxia detection agent, pimonidazole hydrochloride, in three immunologically distinct murine models of IPA (chemotherapeutic, X-CGD, and corticosteroid). In all three IPA murine models, hypoxia was observed during the course of infection. We next tested the hypothesis that production of ethanol in vivo by the fungus is involved in hypoxia adaptation and fungal pathogenesis. Ethanol deficient A. fumigatus strains showed no growth defects in hypoxia and were able to cause wild type levels of mortality in all 3 murine models. However, lung immunohistopathology and flow cytometry analyses revealed an increase in the inflammatory response in mice infected with an alcohol dehydrogenase null mutant strain that corresponded with a reduction in fungal burden. Consequently, in this study we present the first in vivo observations that hypoxic microenvironments occur during a pulmonary invasive fungal infection and observe that a fungal alcohol dehydrogenase influences fungal pathogenesis in the lung. Thus, environmental conditions encountered by invading pathogenic fungi may result in substantial fungal metabolism changes that influence subsequent host immune responses.