Risk factors for hospital-acquired infection during the SARS-CoV-2 pandemic.

OBJECTIVE: To evaluate risk factors for hospital-acquired infection (HAI) in patients during the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) pandemic, including historical and concurrent cohorts. DESIGN: Retrospective cohort. SETTING: Three Missouri hospitals, data from 1st January 2017 to 30th September 2020. PARTICIPANTS: Patients aged ≥18 years and admitted for ≥48 h. METHODS: Univariate and multi-variate Cox proportional hazards models incorporating the competing risk of death were used to determine risk factors for HAI. A-priori sensitivity analyses were performed to assess the robustness of the urine-, blood- and respiratory-culture-based HAI definition. RESULTS: The cohort included 254,792 admissions, with 7147 (2.8%) HAIs (1661 blood, 3407 urine, 2626 respiratory). Patients with SARS-CoV-2 had increased risk of HAI (adjusted hazards ratio 1.65, 95% confidence interval 1.38-1.96), and SARS-CoV-2 infection was one of the strongest risk factors for development of HAI. Other risk factors for HAI included certain admitting services, chronic comorbidities, intensive care unit stay during index admission, extremes of body mass index, hospital, and selected medications. Factors associated with lower risk of HAI included year of admission (declined over the course of the study), admitting service and medications. Risk factors for HAI were similar in sensitivity analyses restricted to patients with diagnostic codes for pneumonia/upper respiratory infection and urinary tract infection. CONCLUSIONS: SARS-CoV-2 was associated with significantly increased risk of HAI.

Risk factors for Clostridioides difficile infection in hospitalized patients and associated mortality in Japan: a multi-centre prospective cohort study.

BACKGROUND: Although population characteristics and antimicrobial prescribing practices suggest that the hospitalized population in Japan is at high risk of Clostridioides difficile infection (CDI), the epidemiology of CDI in Japan is poorly understood. AIM: This prospective cohort study aimed to investigate the epidemiology of CDI at 12 hospitals in Japan. METHODS: Patients with clinically significant diarrhoea (CSD) were enrolled. Stool specimens were tested for C. difficile by toxin A and/or B enzyme immunoassay (EIA) in the hospital laboratories, and a toxigenic culture and nucleic acid amplification tests were performed at a central laboratory. The risk factors of CDI and the impact of CDI on mortality were investigated. FINDINGS: In total, 566 patients with CSD were included in the analyses. A total of 152 patients received the diagnosis of CDI by Toxin A/B EIA, toxigenic culture, or nucleic acid amplification test. Factors associated with CDI included low albumin (adjusted odds ratio (aOR): 1.56; 95% confidence interval (CI): 1.03-2.34) and length of hospital stay before stool collection >18 days (aOR: 1.73; 95% CI: 1.09-2.75). CDI was associated with an increased mortality on univariate analysis (OR: 1.6, 95% CI: 1.0-2.6) but was not associated with an increased risk of mortality on multivariable analysis. CONCLUSION: Risk factors for CDI in Japan were similar to those identified in the USA and Europe. However, CDI was not associated with an increased risk of mortality in this population of patients with CSD.

Epidemiology and outcomes of Clostridium difficile infection in allogeneic hematopoietic cell and lung transplant recipients.

BACKGROUND: Clostridium difficile infection (CDI) is a common complication of lung and allogeneic hematopoietic cell (HCT) transplant, but the epidemiology and outcomes of CDI after transplant are poorly described. METHODS: We performed a prospective, multicenter study of CDI within 365 days post-allogeneic HCT or lung transplantation. Data were collected via patient interviews and medical chart review. Participants were followed weekly in the 12 weeks post-transplant and while hospitalized and contacted monthly up to 18 months post-transplantation. RESULTS: Six sites participated in the study with 614 total participants; 4 enrolled allogeneic HCT (385 participants) and 5 enrolled lung transplant recipients (229 participants). One hundred and fifty CDI cases occurred within 1 year of transplantation; the incidence among lung transplant recipients was 13.1% and among allogeneic HCTs was 31.2%. Median time to CDI was significantly shorter among allogeneic HCT than lung transplant recipients (27 days vs 90 days; P = .037). CDI was associated with significantly higher mortality from 31 to 180 days post-index date among the allogeneic HCT recipients (Hazard ratio [HR] = 1.80; P = .007). There was a trend towards increased mortality among lung transplant recipients from 120 to 180 days post-index date (HR = 4.7, P = .09). CONCLUSIONS: The epidemiology and outcomes of CDI vary by transplant population; surveillance for CDI should continue beyond the immediate post-transplant period.

Recurrent Clostridium difficile infection is associated with increased mortality.

Clostridium difficile infections (CDI) are associated with decreased survival, and up to 30% of CDI patients may experience a recurrence. Data on the impact of recurrent CDI on mortality are scarce. The purpose of this study was to determine whether recurrent CDI was independently associated with decreased 6-month survival compared with patients with CDI who did not develop a recurrence. We performed a retrospective cohort study at an academic, urban, tertiary care hospital. Data were collected from the electronic medical record and chart review. CDI patients were followed for 180 days from the end of their index hospital discharge or end of index CDI antibiotic treatment, whichever was later, to determine mortality. Kaplan-Meier analysis was used to compare patient mortality by recurrent CDI status. Cox proportional hazards models were used to determine independent risk factors for death within 180 days. In all, 3958 patients aged ≥ 18 years who developed an initial CDI episode from 2003 to 2009, including 421 patients with recurrent CDI, were included in the study. Thirty-six per cent of persons with recurrent CDI died within 180 days, compared with 26% of persons without CDI recurrence (log-rank p <0.001). Recurrent CDI was associated with significantly higher hazards of death within 180 days, adjusting for demographics, comorbidities and medications received during the index CDI hospitalization (hazard ratio 1.33; 95% CI 1.12-1.58). Recurrent CDI is associated with significantly increased risk of death within 6 months after completion of their initial CDI treatment compared with CDI patients who do not develop a recurrence.

Epidemiological model for Clostridium difficile transmission in healthcare settings.

OBJECTIVE: Recent outbreaks of Clostridium difficile infection (CDI) have been difficult to control, and data indicate that the importance of different sources of transmission may have changed. Our objectives were to evaluate the contributions of asymptomatic and symptomatic C. difficile carriers to new colonizations and to determine the most important epidemiological factors influencing C. difficile transmission. DESIGN, SETTING, AND PATIENTS: Retrospective cohort study of all patients admitted to medical wards at a large tertiary care hospital in the United States in the calendar year 2008. METHODS: Data from six medical wards and published literature were used to develop a compartmental model of C. difficile transmission. Patients could be in one of five transition states in the model: resistant to colonization (R), susceptible to colonization (S), asymptomatically colonized without protection against CDI (C(-)), asymptomatically colonized with protection against CDI (C(+)), and diseased (ie, with CDI; D). RESULTS: The contributions of C(-), C(+), and D patients to new colonizations were similar. The simulated basic reproduction number ranged from 0.55 to 1.99, with a median of 1.04. These values suggest that transmission within the ward alone from patients with CDI cannot sustain new C. difficile colonizations and therefore that the admission of colonized patients plays an important role in sustaining transmission in the ward. The epidemiological parameters that ranked as the most influential were the proportion of admitted C(-) patients and the transmission coefficient for asymptomatic carriers. CONCLUSION: Our study underscores the need to further evaluate the role of asymptomatically colonized patients in C. difficile transmission in healthcare settings.

Identification of major histocompatibility complex class II-associated peptides derived from freshly prepared rat Langerhans cells using MALDI-PSD and Edman degradation.

The isolation and identification is described of MHC class II-bound peptides derived from Langerhans cells. A combination of preparative micro-HPLC, MALDI-MS, Edman degradation was used for determining the amino acid sequence of MHC-associated peptides. Sample handling was crucial because fractions containing trace amounts of material require immediate storage at -80 degrees C to prevent peptide losses.

Involvement of dendritic cell response to resistance of stomach carcinogenesis caused by N-methyl-N'-nitro-N-nitrosoguanidine in rats.

The involvement of immune response in the resistance of chemically induced stomach cancer was studied in a resistant rat strain (Buffalo) and a sensitive rat strain (ACI). Groups of 10 male Buffalo and ACI rats, 6 weeks of age, were given drinking water with or without N-methyl-N'-nitro-N-nitrosoguanidine (MNNG; 100 mg/l) for 14 days. Total RNA was isolated from the stomach pyloric mucosa from five rats, and cDNA was prepared with reverse transcriptase. Tissue sections of the stomach pyloric mucosa from five rats were stained with antibodies recognizing molecules expressed by various immune cells. Reverse transcription-PCR (RT-PCR), competitive RT-PCR, and Northern blot demonstrated that the expression of MHC class II group genes [MHC class II, MHC class II-associated invariant chain (Ii), CD4 and IgM (B cell marker)], MHC class I group genes (MHC class I and CD8), B7-1 (costimulator on dendritic cells), and CD28 (receptor to B7 on T cells) in the pyloric mucosa was elevated by MNNG in both rat strains but was elevated to a 4-7-fold greater extent in Buffalo rats than in ACI rats. These genes were scarcely expressed in control rats. Histochemical antibody staining after MNNG exposure showed a greater number of cells stained with monoclonal antibody to Ii, OX-62 (dendritic cell marker), and ED-1 (dendritic cell and macrophage common marker) in the interstitial tissue of the pyloric mucosa of Buffalo rats compared with ACI rats. Cell proliferation, as measured by 5-bromo-2-deoxyuridine (BrdUrd)-labeling indices, revealed the presence of BrdUrd-labeled cells only among epithelial cells in the proliferative zone; cells in the interstitial tissue were not labeled with BrdUrd. The results suggest the involvement of dendritic cell response in the resistance to the MNNG induction of stomach carcinogenesis in rats.

Full length cDNA of rat RT1.DMa and RT1.DMb and expression of RT1.DM genes in dendritic and Langerhans cells.

MHC encoded DM heterodimers and classical MHC class II complexes meet in an endosomal/lysosomal compartment where DM heterodimers support peptide loading of MHC class II. Studies on peptide loading of rat class II and on peptide persistence in cells of the dendritic lineage prompted us to establish full length cDNA clones coding for the subunits alpha and beta of rat DM molecules as well as a mAb directed against the luminal moiety of the beta subunit. Here we describe the establishment of the first full length cDNA clones of rat RT1.DMa and RT1.DMb. The mode of expression of RT1.DM at the transcript level in bone marrow culture-derived dendritic cells, in Langerhans cells and in a number of additional accessory cells is reported. The beta protein was identified in detergent lysates of RT1.DM expressing cells by Western blot analysis using a newly established monoclonal antibody directed against the luminal part of RT1.DMbeta.

Differentially expressed MHC class II-associated invariant chain in rat stomach pyloric mucosa with N-methyl-N-nitro-nitrosoguanidine exposure.

Administration of N-methyl-N'-nitro-N-nitrosoguanidine, a glandular stomach carcinogen, at the concentration of 100 microg/ml in drinking water for 8 days induced the appearance of a MHC class II-associated invariant chain in the target organ of stomach pyloric mucosa of male Lewis rats. The up-regulation of the MHC class II-associated invariant chain was revealed by fluorescent differential display analysis, reverse transcription-PCR, Northern blot, and histochemical staining. The appearance of MHC class II and MHC class I was also demonstrated by reverse transcription-PCR and Northern blot. The results suggest the involvement of MHC-controlled immune reactions in chemically-induced stomach carcinogenesis.

An MHC class II-expressing T cell clone presenting conventional antigen lacks the ability to present bacterial superantigen.

We have analyzed the response of rat T cells to myelin basic protein (MBP) and the bacterial superantigen, staphylococcal enterotoxin E (SEE). Rat T cells reactive with MBP can respond to SEE presented by spleen cells but not to SEE presented by LOA, a rat T cell clone that expresses both I-A and I-E MHC class II molecules, even though LOA is much more efficient than splenic APC in the presentation of MBP. The inability of LOA to present superantigen is not due to a structural difference in MHC II molecules between LOA and the splenic APC or to differential expression of major accessory/adhesion molecules, including CD2, CD5, CD4 and CD44, on LOA. The non-responsiveness of SEE/LOA-induced T cells differs from anergy, in that such cells do not lose their subsequent responsiveness to either MBP or SEE. Our results demonstrate that: (i) MHC class II molecules (I-A and I-E) alone are insufficient for the activation of T cells by bacterial superantigen, (ii) failure to respond to antigen presented upon inappropriate APC or in inadequate doses may not necessarily represent anergy, and (iii) the quality of the T cell response towards certain ligands can be strongly influenced by the nature of the APC.

Uptake of microparticle-adsorbed protein antigen by bone marrow-derived dendritic cells results in up-regulation of interleukin-1 alpha and interleukin-12 p40/p35 and triggers prolonged, efficient antigen presentation.

Dendritic cells synthesize and express major histocompatibility complex (MHC) class II peptide-binding elements constitutively and, therefore, belong to the category of professional antigen-presenting cells. Unlike other cells that show constitutive class II expression, such as B cells and certain T cell clones, dendritic cells possess the unique capacity to activate naive T cells. Using dendritic cells generated in vitro by culture of mouse bone marrow in the presence of low doses of recombinant mouse granulocyte/macrophage colony-stimulating factor, we found that discrete maturation stages of these cells can be distinguished which were correlated with defined functional capabilities. The striking observation was the presence of a progenitor dendritic cell expressing low levels of class II which, unlike its differentiated counterpart in vitro, possessed pronounced phagocytic activity. Adding protein antigen to dendritic cells in a particle-adsorbed form, as compared to a soluble form, we demonstrate that phagocytosis of the particle-adsorbed protein by progenitor dendritic cells involves an activation event. This is evidenced by the de novo synthesis of transcripts of interleukin-1 alpha and interleukin-12 p40/p35 as well as transcripts of MHC class II. Most importantly, an augmented and prolonged antigen-presentation capacity was observed when the antigen was given in particle-adsorbed instead of soluble form. These findings indicate that progenitor dendritic cells are functionally more flexible and potent than fully differentiated dendritic cells and that they play a crucial role in antigen presentation. It is suggested that these findings will open up new possibilities to devise strategies for vaccine development.

Potassium-inhibited processing of IL-1 beta in human monocytes.

Agents that deplete cells of K+ without grossly disrupting the plasma membrane were found to stimulate the cleavage of pro-interleukin (IL)-1 beta to mature IL-1 beta. Agents examined in this study included staphylococcal alpha-toxin and gramicidin, both of which selectively permeabilize plasma membranes for monovalent ions, the ionophores nigericin and valinomycin, and the Na+/K+ ATPase inhibitor ouabain. K+ depletion by brief hypotonic shock also triggered processing of pro-IL-1 beta. The central role of K+ depletion for inducing IL-1 beta maturation was demonstrated in cells permeabilized with alpha-toxin: processing of pro-IL-1 beta was totally blocked when cells were suspended in medium that contained high K+, but could be induced by replacing extracellular K+ with Na+, choline+ or sucrose. To test whether K+ flux might also be important in physiological situations, monocytes were stimulated with lipopolysaccharide (LPS) for 1-2 h to trigger pro-IL-1 beta synthesis, and transferred to K(+)-rich medium. This maneuver totally suppressed IL-1 beta maturation. Even after 16 h, however, removal of K+ from the medium resulted in rapid processing and export of IL-1 beta. Ongoing export of mature IL-1 beta from cells stimulated with LPS for 2-6 h could also be arrested by transfer to K(+)-rich medium. Moreover, a combination of two K+ channel blockers inhibited processing of IL-1 beta in LPS-stimulated monocytes. We hypothesize that K+ movement and local K+ concentrations directly or indirectly influence the action of interleukin-1 beta-converting enzyme (ICE) and, possibly, of related intracellular proteases.

Experimental autoimmune panencephalitis and uveoretinitis transferred to the Lewis rat by T lymphocytes specific for the S100 beta molecule, a calcium binding protein of astroglia.

The pathogenic potential of autoimmune T cell responses to nonmyelin autoantigens was investigated in the Lewis rat using the astrocyte-derived calcium binding protein S100 beta, as a model nonmyelin autoantigen. The Lewis rat mounts a vigorous RT1B1 (major histocompatibility complex class II) restricted autoimmune response to an immunodominant S100 beta epitope (amino acid residues 76-91). The adoptive transfer of S100 beta-specific T cell lines induced a severe inflammatory response in the nervous system, but only minimal neurological dysfunction in naive syngeneic recipients. The inability of S100 beta-specific T cell transfer to induce severe disease was associated with a decreased recruitment of ED1+ macrophages into the central nervous system (CNS) in comparison with that seen in severe experimental autoimmune encephalomyelitis (EAE) induced by the adoptive transfer of myelin basic protein (MBP)-specific T line cells. Moreover, unlike encephalitogenic MBP-specific T cell lines, S100 beta-specific T cell lines exhibited no cytotoxic activity in vitro. Histopathological analysis also revealed striking differences in the distribution of inflammatory lesions in MBP- and S100 beta-specific T cell-mediated disease. In contrast to the MBP paradigm, S100 beta-specific T cell transfer induces intense inflammation not only in the spinal cord, but throughout the entire CNS and also in the uvea and retina of the eye. In view of the distribution of lesions throughout the grey and white matter of the CNS we propose to term this new model experimental autoimmune panencephalomyelitis (EAP) to differentiate it from EAE. These experiments demonstrate for the first time that nonmyelin CNS autoantigens can initiate a pathogenic autoimmune T cell response, although the nature of the target autoantigen profoundly influences the clinical and histopathological characteristics of the resulting autoimmune disease. This is not simply a consequence of the distribution of the autoantigen, as both MBP and S100 beta are coexpressed in many areas of the CNS, but reflects differences in the capacity of different regions of the CNS to process and present specific autoantigens. This new model of T cell-mediated autoimmune CNS disease exhibits a number of similarities to multiple sclerosis (MS), such as its mild clinical course and the involvement of areas of the brain and eye, which are absent in myelin-mediated models of EAE. Nonmyelin autoantigens may therefore play an unexpectedly important role in the immunopathogenesis of inflammatory diseases of the CNS.

Direct binding of autoimmune disease related T cell epitopes to purified Lewis rat MHC class II molecules.

New strategies applied in the treatment of experimental autoimmune disease models involve blocking or modulation of MHC-peptide-TCR interactions either at the level of peptide-MHC interaction or, alternatively, at the level of T cell recognition. In order to identify useful competitor peptides one must be able to assess peptide-MHC interactions. Several well described autoimmune disease models exist in the Lewis rat and thus this particular rat strain provides a good model system to study the effect of competitor peptides. So far no information has been available on the peptide binding characteristics of the Lewis rat MHC class II RT1.B1 molecule. We have now developed a biochemical binding assay which enables competition studies in which the relative MHC binding affinity of a set of non-labelled peptides can be assessed while employing detection of biotinylated marker peptides by chemiluminescence. The assay is sensitive and specific. We have used this assay to determine the binding characteristics of several disease associated T cell determinants and their sequence analogues in the Lewis rat. Notably, most of the autoimmune disease associated peptide sequences tested were found to be intermediate to poor binders. Single amino acid substitutions at defined positions were sufficient to turn certain peptides into good binders. These results are relevant to the design of competitor peptides in the treatment of experimental autoimmune diseases.

An in vitro test for endocytotic activation of murine epidermal Langerhans cells under the influence of contact allergens.

Several in vivo and in vitro studies have shown that contact sensitizing agents induce enhanced internalization of cell membrane constituents by epidermal Langerhans cells (LC). However the intracellular distribution of the internalized material has not yet been clearly defined. For this reason we investigated the uptake of gold-labeled antibodies against MHC class II molecules by cultured murine LC under the influence of various contact sensitizing agents, non-sensitizing analogues, and irritants. Antigen-antibody complexes were visualized by light microscopy using the silver enhancement technique and by pre-embedding electron microscopy. Viability was monitored by staining dead cells with propidium iodide. For light-microscopic evaluation of the intracellular distribution pattern of gold particles, a stimulation index was defined and used for the assessment of endocytotic activation. Untreated and solvent treated (control) cells exhibited an accumulation of internalized gold complexes into large aggregates composed of few intracellular vesicles. Cytoplasmic staining was absent and few gold particles were detectable in the endocytotic organelles under these conditions. In contrast to the non-sensitizing compounds DCNB and DNBSO3, which had no effect at all, treatment with subtoxic concentrations of the contact sensitizing agents DNFB, DNCB, TNCB, K2Cr2O7, NISO4 and p-phenylenediamine resulted in diffuse intracellular staining which was most pronounced in the submembraneous region. This was due to the numerous endocytotic vesicles which were closely associated with the cell membrane. Consequently a significant increase in the stimulation index was noted for these compounds. An irritant such as sodium lauryl sulphate used in subtoxic concentrations did not influence the intracellular distribution of internalized gold particles whereas toxic amounts of this compound induced a diffuse intracellular staining pattern indicative of membrane destruction. This approach represents a practical and reliable test for endocytotic activation of murine LC and may be useful for in vitro tests of the activating and possibly sensitizing properties of new chemical compounds.

Non-coordinate synthesis of MHC class II proteins and invariant chains by epidermal Langerhans cells derived from short-term in vitro culture.

Epidermal cells (EC) prepared from Lewis rat skin contained 2-3% class II+, LCA+ Langerhans cells (LC). LC enriched from freshly isolated EC suspensions proved highly effective accessory cells when presenting the nominal antigen OVA to an RT1.Bl-restricted ovalbumin (OVA)-specific rat T cell clone. Short-term preculture of the EC resulted in diminished OVA presenting capacity of the LC. Flow cytometry (FCM) analysis of class II and gamma chain expression revealed an up-regulation of class II on the LC's cell surface, consistent with earlier findings in mouse and human. However, while the presence of gamma chains in mouse LC was reported to decline to negligible levels during culture we observed substantial gamma surface expression on 3 day cultured rat LC, accompanied by increasing quantities of gamma inside the cells as revealed by FCM analysis on permeabilized cells. Biosynthetic labeling of panning-enriched LC from fresh and cultured EC confirmed and extended the immunocytological analysis. In contrast to the synthesis of class II proteins, that declined during culture to background levels, gamma chain synthesis was strongly augmented after 1 day in culture and remained at prominent levels throughout the culture period. In LC pulse labeled for 4 h and subjected to a 3 day chase period prominent quantities of labeled class II complexes were detectable with the majority of the dimers exhibiting the compact (C)-type folding form. On the basis of our findings a novel function of the invariant gamma chain is suggested to be effective in LC.