Clinical features and prognostic factors of listeriosis: the MONALISA national prospective cohort study

BACKGROUND

Listeriosis is a severe foodborne infection and a notifiable disease in France. We did a nationwide prospective study to characterise its clinical features and prognostic factors.

METHODS

MONALISA was a national prospective observational cohort study. We enrolled eligible cases declared to the National Reference Center for Listeria (all microbiologically proven) between Nov 3, 2009, and July 31, 2013, in the context of mandatory reporting. The outcomes were analysis of clinical features, characterisation of Listeria isolates, and determination of predictors of 3-month mortality or persisting impairment using logistic regression. A hierarchical clustering on principal components was also done for neurological and bacteraemic cases. The study is registered at ClinicalTrials.gov, number NCT01520597.

FINDINGS

We enrolled 818 cases from 372 centres, including 107 maternal-neonatal infections, 427 cases of bacteraemia, and 252 cases of neurolisteriosis. Only five (5%) of 107 pregnant women had an uneventful outcome. 26 (24%) of 107 mothers experienced fetal loss, but never after 29 weeks of gestation or beyond 2 days of admission to hospital. Neurolisteriosis presented as meningoencephalitis in 212 (84%) of 252 patients; brainstem involvement was only reported in 42 (17%) of 252 patients. 3-month mortality was higher for bacteraemia than neurolisteriosis (hazard ratio [HR] 0·54 [95% CI 0·41-0·69], p<0·0001). For both bacteraemia and neurolisteriosis, the strongest mortality predictors were ongoing cancer (odds ratio [OR] 5·19 [95% CI 3·01-8·95], p<0·0001), multi-organ failure (OR 7·98 [4·32-14·72], p<0·0001), aggravation of any pre-existing organ dysfunction (OR 4·35 [2·79-6·81], p<0·0001), and monocytopenia (OR 3·70 [1·82-7·49], p=0·0003). Neurolisteriosis mortality was higher in blood-culture positive patients (OR 3·67 [1·60-8·40], p=0·002) or those receiving adjunctive dexamethasone (OR 4·58 [1·50-13·98], p=0·008).

INTERPRETATION

The severity of listeriosis is higher than reported elsewhere. We found evidence of a significantly reduced survival in patients with neurolisteriosis treated with adjunctive dexamethasone, and also determined the time window for fetal losses. MONALISA provides important new data to improve management and predict outcome in listeriosis.

FUNDING

Programme Hospitalier Recherche Clinique, Institut Pasteur, Inserm, French Public Health Agency.

A longitudinal study of SARS-CoV-2-infected patients reveals a high correlation between neutralizing antibodies and COVID-19 severity

Understanding the immune responses elicited by SARS-CoV-2 infection is critical in terms of protection against reinfection and, thus, for public health policy and vaccine development for COVID-19. In this study, using either live SARS-CoV-2 particles or retroviruses pseudotyped with the SARS-CoV-2 S viral surface protein (Spike), we studied the neutralizing antibody (nAb) response in serum samples from a cohort of 140 SARS-CoV-2 qPCR-confirmed infections, including patients with mild symptoms and also more severe forms, including those that required intensive care. We show that nAb titers correlated strongly with disease severity and with anti-spike IgG levels. Indeed, patients from intensive care units exhibited high nAb titers; conversely, patients with milder disease symptoms had heterogeneous nAb titers, and asymptomatic or exclusive outpatient-care patients had no or low nAbs. We found that nAb activity in SARS-CoV-2-infected patients displayed a relatively rapid decline after recovery compared to individuals infected with other coronaviruses. Moreover, we found an absence of cross-neutralization between endemic coronaviruses and SARS-CoV-2, indicating that previous infection by human coronaviruses may not generate protective nAbs against SARS-CoV-2. Finally, we found that the D614G mutation in the spike protein, which has recently been identified as the current major variant in Europe, does not allow neutralization escape. Altogether, our results contribute to our understanding of the immune correlates of SARS-CoV-2-induced disease, and rapid evaluation of the role of the humoral response in the pathogenesis of SARS-CoV-2 is warranted.

Development of three multiplex RT-PCR assays for the detection of 12 respiratory RNA viruses

Three multiplex hemi-nested RT-PCR assays were developed to detect simultaneously 12 RNA respiratory viruses: influenza viruses A, B and C, human respiratory syncytial virus (hRSV), human metapneumovirus (hMPV), parainfluenza virus types 1-4 (PIV-1, -2, -3 and -4), human coronavirus OC43 and 229E (HCoV) and rhinovirus (hRV). An internal amplification control was included in one of the RT-PCR assays. The RT-PCR multiplex 1 and the hemi-nested multiplex 1 detected 1 and 0.1 TCID50 of RSV A, respectively, and 0.01 and 0.001 TCID50 of influenza virus A/H3N2, respectively. Two hundred and three nasal aspirates from hospitalised children were retrospectively tested in comparison with two conventional methods: direct immunofluorescence assay and viral isolation technique. Almost all samples (89/91) that were positive by immunofluorescence assay and/or viral isolation technique were detected by the multiplex assay. This method also detected an additional 85 viruses and 33 co-infections. The overall sensitivity (98%), rapidity and enhanced efficiency of these multiplex hemi-nested RT-PCR assays suggest that they would be a significant improvement over conventional methods for the detection of a broad spectrum of respiratory viruses.

Clinical recurrences of COVID-19 symptoms after recovery: Viral relapse, reinfection or inflammatory rebound?

For the first 3 months of COVID-19 pandemic, COVID-19 was expected to be an immunizing non-relapsing disease. We report a national case series of 11 virologically-confirmed COVID-19 patients having experienced a second clinically- and virologically-confirmed acute COVID-19 episode. According to the clinical history, we discuss either re-infection or reactivation hypothesis. Larger studies including further virological, immunological and epidemiologic data are needed to understand the mechanisms of these recurrences.

Surveillance network for herpes simplex virus resistance to antiviral drugs: 3-year follow-up

Herpes simplex virus (HSV) infections are very common in the general population and among immunocompromised patients. Acyclovir (ACV) is an effective treatment which is widely used. We deemed it essential to conduct a wide and coordinated survey of the emergence of ACV-resistant HSV strains. We have formed a network of 15 virology laboratories which have isolated and identified, between May 1999 and April 2002, HSV type 1 (HSV-1) and HSV-2 strains among hospitalized subjects. The sensitivity of each isolate to ACV was evaluated by a colorimetric test (C. Danve, F. Morfin, D. Thouvenot, and M. Aymard, J. Virol. Methods 105:207-217, 2002). During this study, 3900 isolated strains among 3357 patients were collected; 55% of the patients were immunocompetent. Only six immunocompetent patients excreted ACV-resistant HSV strains (0.32%), including one female patient not treated with ACV who was infected primary by an ACV-resistant strain. Among the 54 immunocompromised patients from whom ACV-resistant HSV strains were isolated (3.5%), the bone marrow transplantation patients showed the highest prevalence of resistance (10.9%), whereas among patients infected by human immunodeficiency virus, the prevalence was 4.2%. In 38% of the cases, the patients who excreted the ACV-resistant strains were treated with foscarnet (PFA), and 61% of them developed resistance to PFA. The collection of a large number of isolates enabled an evaluation of the prevalence of resistance of HSV strains to antiviral drugs to be made. This prevalence has remained stable over the last 10 years, as much among immunocompetent patients as among immunocompromised patients.

Platelets and infections - complex interactions with bacteria

Platelets can be considered sentinels of vascular system due to their high number in the circulation and to the range of functional immunoreceptors they express. Platelets express a wide range of potential bacterial receptors, including complement receptors, FcγRII, Toll-like receptors but also integrins conventionally described in the hemostatic response, such as GPIIb–IIIa or GPIb. Bacteria bind these receptors either directly, or indirectly via fibrinogen, fibronectin, the first complement C1q, the von Willebrand Factor, etc. The fate of platelet-bound bacteria is questioned. Several studies reported the ability of activated platelets to internalize bacteria such as Staphylococcus aureus or Porphyromonas gingivalis, though there is no clue on what happens thereafter. Are they sheltered from the immune system in the cytoplasm of platelets or are they lysed? Indeed, while the presence of phagolysosome has not been demonstrated in platelets, they contain antimicrobial peptides that were shown to be efficient on S. aureus. Besides, the fact that bacteria can bind to platelets via receptors involved in hemostasis suggests that they may induce aggregation; this has indeed been described for Streptococcus sanguinis, S. epidermidis, or C. pneumoniae. On the other hand, platelets are able to display an inflammatory response to an infectious triggering. We, and others, have shown that platelet release soluble immunomodulatory factors upon stimulation by bacterial components. Moreover, interactions between bacteria and platelets are not limited to only these two partners. Indeed, platelets are also essential for the formation of neutrophil extracellular traps by neutrophils, resulting in bacterial clearance by trapping bacteria and concentrating antibacterial factors but in enhancing thrombosis. In conclusion, the platelet–bacteria interplay is a complex game; its fine analysis is complicated by the fact that the inflammatory component adds to the aggregation response.

Cytomegalovirus load in inflamed intestinal tissue is predictive of resistance to immunosuppressive therapy in ulcerative colitis

OBJECTIVES

Previous studies have suggested an association between cytomegalovirus (CMV) infection and steroid-refractory inflammatory bowel disease. In this study, the use of CMV DNA load during acute flare-ups of ulcerative colitis (UC) to predict resistance to immunosuppressive therapy was evaluated in intestinal tissue.

METHODS

Forty-two consecutive patients (sex ratio M/F: 0.9, mean age: 43.6 years) hospitalized for moderate to severe UC and treated with IV steroids were included prospectively. A colonoscopy was performed for each patient at inclusion; colonic biopsy samples of the pathological tissue, and if possible, of the healthy mucosa, were tested for histological analysis and determination of CMV DNA load by real-time polymerase chain reaction assay. Patients were treated as recommended by the current guidelines.

RESULTS

Sixteen patients were found positive for CMV DNA in inflamed intestinal tissue but negative in endoscopically healthy tissue; all of these patients were positive for anti-CMV IgG, three exhibited CMV DNA in blood, and none was positive for intestinal CMV antigen by immunohistochemistry detection. In the 26 remaining patients, no stigmata of recent CMV infection were recorded by any technique. By multivariate analysis, the only factor associated with CMV DNA in inflammatory tissue was the resistance to steroids or to three lines of treatment (risk ratio: 4.7; 95% confidence interval: 1.2-22.5). A CMV DNA load above 250 copies/mg in tissue was predictive of resistance to three successive regimens (likelihood ratio+=4.33; area under the receiver-operating characteristic curve=0.85). Eight UC patients with CMV DNA in inflamed tissue and therapeutic failure received ganciclovir; a clinical remission was observed in seven cases, with a sustained response in five of them.

CONCLUSIONS

The CMV DNA load determined in inflamed intestinal tissue predicts resistance to steroid treatment and to three drug regimens in UC. Initiation of an early antiviral treatment in these patients might delay the occurrence of resistance to current treatments.

The Inflammatory Role of Platelets via Their TLRs and Siglec Receptors

Platelets are non-nucleated cells that play central roles in the processes of hemostasis, innate immunity, and inflammation; however, several reports show that these distinct functions are more closely linked than initially thought. Platelets express numerous receptors and contain hundreds of secretory products. These receptors and secretory products are instrumental to the platelet functional responses. The capacity of platelets to secrete copious amounts of cytokines, chemokines, and related molecules appears intimately related to the role of the platelet in inflammation. Platelets exhibit non-self-infectious danger detection molecules on their surfaces, including those belonging to the “toll-like receptor” family, as well as pathogen sensors of other natures (Ig- or complement receptors, etc.). These receptors permit platelets to both bind infectious agents and deliver differential signals leading to the secretion of cytokines/chemokines, under the control of specific intracellular regulatory pathways. In contrast, dysfunctional receptors or dysregulation of the intracellular pathway may increase the susceptibility to pathological inflammation. Physiological vs. pathological inflammation is tightly controlled by the sensors of danger expressed in resting, as well as in activated, platelets. These sensors, referred to as pathogen recognition receptors, primarily sense danger signals termed pathogen associated molecular patterns. As platelets are found in inflamed tissues and are involved in auto-immune disorders, it is possible that they can also be stimulated by internal pathogens. In such cases, platelets can also sense danger signals using damage associated molecular patterns (DAMPs). Some of the most significant DAMP family members are the alarmins, to which the Siglec family of molecules belongs. This review examines the role of platelets in anti-infection immunity via their TLRs and Siglec receptors.

Immunogenicity and efficacy of heterologous ChAdOx1-BNT162b2 vaccination

Following severe adverse reactions to the AstraZeneca ChAdOx1-S-nCoV-19 vaccine^1,2, European health authorities recommended that patients under the age of 55 years who received one dose of ChAdOx1-S-nCoV-19 receive a second dose of the Pfizer BNT162b2 vaccine as a booster. However, the effectiveness and the immunogenicity of this vaccination regimen have not been formally tested. Here we show that the heterologous ChAdOx1-S-nCoV-19 and BNT162b2 combination confers better protection against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection than the homologous BNT162b2 and BNT162b2 combination in a real-world observational study of healthcare workers (n = 13,121). To understand the underlying mechanism, we conducted a longitudinal survey of the anti-spike immunity conferred by each vaccine combination. Both combinations induced strong anti-spike antibody responses, but sera from heterologous vaccinated individuals displayed a stronger neutralizing activity regardless of the SARS-CoV-2 variant. This enhanced neutralizing potential correlated with increased frequencies of switched and activated memory B cells that recognize the SARS-CoV-2 receptor binding domain. The ChAdOx1-S-nCoV-19 vaccine induced a weaker IgG response but a stronger T cell response than the BNT162b2 vaccine after the priming dose, which could explain the complementarity of both vaccines when used in combination. The heterologous vaccination regimen could therefore be particularly suitable for immunocompromised individuals.

The signaling role of CD40 ligand in platelet biology and in platelet component transfusion

The CD40 ligand (CD40L) is a transmembrane molecule of crucial interest in cell signaling in innate and adaptive immunity. It is expressed by a variety of cells, but mainly by activated T-lymphocytes and platelets. CD40L may be cleaved into a soluble form (sCD40L) that has a cytokine-like activity. Both forms bind to several receptors, including CD40. This interaction is necessary for the antigen specific immune response. Furthermore, CD40L and sCD40L are involved in inflammation and a panoply of immune related and vascular pathologies. Soluble CD40L is primarily produced by platelets after activation, degranulation and cleavage, which may present a problem for transfusion. Soluble CD40L is involved in adverse transfusion events including transfusion related acute lung injury (TRALI). Although platelet storage designed for transfusion occurs in sterile conditions, platelets are activated and release sCD40L without known agonists. Recently, proteomic studies identified signaling pathways activated in platelet concentrates. Soluble CD40L is a good candidate for platelet activation in an auto-amplification loop. In this review, we describe the immunomodulatory role of CD40L in physiological and pathological conditions. We will focus on the main signaling pathways activated by CD40L after binding to its different receptors.

High sensitivity and specificity of serum procalcitonin levels in adults with bacterial meningitis

It was shown in children that serum procalcitonin was the best marker to use to differentiate bacterial from viral meningitis. To evaluate procalcitonin in the diagnosis of acute bacterial and viral meningitis, we conducted a prospective study including adult patients who were suspected of having meningitis and who were admitted to an emergency department. Cerebrospinal fluid (CSF) and serum levels of procalcitonin were measured in 105 consecutive patients. The diagnosis of meningitis was based on clinical findings, gram staining, culture, and chemical analysis of CSF. Twenty-three patients had bacterial meningitis, 57 had viral meningitis, and 25 did not have meningitis. Bacteriologic and chemical analysis of CSF did not allow correct differentiation of viral from bacterial meningitis. On the other hand, a serum procalcitonin level >0.2 ng/mL had a sensitivity and specificity of up to 100% in the diagnosis of bacterial meningitis. Serum procalcitonin levels seem to be the best marker in differentiating between bacterial and viral meningitis in adults.

Toll-like receptor 4 ligand can differentially modulate the release of cytokines by human platelets

Blood platelets link the processes of haemostasis and inflammation. This study examined the immunomodulatory factors released by platelets after Toll-Like Receptor 4 (TLR4) engagement on their surfaces. Monoclonal anti-human FcgammaRII Ab (IV.3)-treated human platelets were cultured with TLR4 ligands in the presence or absence of blocking monoclonal antibody to human TLR4. The release of sCD62p, epidermal growth factor (EGF), transforming growth factor beta (TGFbeta), interleukin (IL)-8, platelet activating factor 4 (PAF4), platelet-derived growth factor, alpha, beta polypeptide (PDGF-AB), Angiogenin, RANTES (regulated upon activation, normal T-cell expressed, and presumably secreted) and sCD40L were measured by specific enzyme-linked immunosorbent assay. TLR4 ligand [Escherichia coli lipopolysaccharide (LPS)] bound platelet TLR4, which differentially modulates the release of cytokines by platelets. It was noted that (i) sCD62p, IL-8, EGF and TGFbeta release were each independent of platelet activation after TLR4 engagement; (ii) RANTES, Angiogenin and PDGF-AB concentration were weaker in platelet supernatant after TLR4 engagement; (iii) sCD40L and PAF4 are present in large concentration in the releaseate of platelets stimulated by TLR4 ligand. The effects of LPS from E. coli on the modulation of secretory factors were attenuated by preincubation of platelets with an anti-TLR4 monoclonal antibody, consistent with the immunomodulation being specifically mediated by the TLR4 receptor. We propose that platelets adapt the subsequent responses, with polarized cytokine secretion, after TLR4 involvement.

Human platelets can discriminate between various bacterial LPS isoforms via TLR4 signaling and differential cytokine secretion

Platelets are currently acknowledged as cells of innate immunity and inflammation and play a complex role in sepsis. We examined whether different types of LPS have different effects on the release of soluble signaling/effective molecules from platelets. We used platelet-rich plasma from healthy volunteers and LPS from two strains of gram-negative bacteria with disparate LPS structures. We combined LPS-stimulated platelet supernatants with reporter cells and measured the PBMC cytokine secretion profiles. Upon stimulation of platelets with both Escherichia coli O111 and Salmonella minnesota LPS, the platelet LPS::TLR4 interaction activated pathways to trigger the production of a large number of molecules. The different platelet supernatants caused differential PBMC secretion of IL-6, TNFα, and IL-8. Our data demonstrate that platelets have the capacity to sense external signals differentially through a single type of pathogen recognition receptor and adjust the innate immune response appropriately for pathogens exhibiting different types of 'danger' signals.

European surveillance for enterovirus D68 during the emerging North-American outbreak in 2014

BACKGROUND

In August and September 2014, unexpected clusters of enterovirus-D68 (EV-D68) infections associated with severe respiratory disease emerged from North-America. In September, the European Centre for Disease Prevention and Control (ECDC) asked European countries to strengthen respiratory sample screening for enterovirus detection and typing in cases with severe respiratory presentations.

OBJECTIVES

To provide a detailed picture of EV-D68 epidemiology in Europe by conducting a retrospective and prospective laboratory analysis of clinical specimens.

STUDY DESIGN

An initiative supported by the European Society for Clinical Virology (ESCV) and ECDC was launched to screen for EV-D68 in respiratory specimens between July 1st and December 1st 2014 in Europe and to sequence the VP1 region of detected viruses for phylogenetic analytic purposes.

RESULTS

Forty-two institutes, representing 51 laboratories from 17 European countries, analyzed 17,248 specimens yielding 389 EV-D68 positive samples (2.26%) in 14 countries. The proportion of positive samples ranged between 0 and 25% per country. These infections resulted primarily in mild respiratory disease, mainly detected in young children presenting with wheezing and in immuno-compromised adults. The viruses detected in Europe are genetically very similar to those of the North-American epidemic and the majority (83%) could be assigned to clade B. Except for 3 acute flaccid paralysis (AFP) cases, one death and limited ICU admissions, no severe cases were reported.

CONCLUSIONS

The European study showed that EV-D68 circulated in Europe during summer and fall of 2014 with a moderate disease burden and different pathogenic profile compared to the North-American epidemic.

Plasma therapy against infectious pathogens, as of yesterday, today and tomorrow

Plasma therapy consists in bringing to a patient in need – in general suffering a severe, resistant to current therapy, and even lethal infection – plasma or specific, fractioned, antibodies, along with other immunoglobulins and possibly healing factors that can be obtained from immunized blood donors; donors (voluntary and benevolent) can be either actively immunized individuals or convalescent persons. Plasma therapy has been used since the Spanish flu in 1917–1918, and regularly then when viral epidemics threatened vulnerable populations, the last reported occurrence being the 2013–2015 Ebola virus outbreak in West Africa. The precise action mechanism of plasma therapy is not fully delineated as it may function beyond purified, neutralizing antibodies.

Povidone Iodine: Properties, Mechanisms of Action, and Role in Infection Control and Staphylococcus aureus Decolonization

Nasal decolonization is an integral part of the strategies used to control and prevent the spread of methicillin-resistant Staphylococcus aureus (MRSA) infections. The two most commonly used agents for decolonization are intranasal mupirocin 2% ointment and chlorhexidine wash, but the increasing emergence of resistance and treatment failure has underscored the need for alternative therapies. This article discusses povidone iodine (PVP-I) as an alternative decolonization agent and is based on literature reviewed during an expert’s workshop on resistance and MRSA decolonization.

Nasal decolonization is an integral part of the strategies used to control and prevent the spread of methicillin-resistant Staphylococcus aureus (MRSA) infections. The two most commonly used agents for decolonization are intranasal mupirocin 2% ointment and chlorhexidine wash, but the increasing emergence of resistance and treatment failure has underscored the need for alternative therapies. This article discusses povidone iodine (PVP-I) as an alternative decolonization agent and is based on literature reviewed during an expert’s workshop on resistance and MRSA decolonization. Compared to chlorhexidine and mupirocin, respectively, PVP-I 10 and 7.5% solutions demonstrated rapid and superior bactericidal activity against MRSA in in vitro and ex vivo studies. Notably, PVP-I 10 and 5% solutions were also active against both chlorhexidine-resistant and mupirocin-resistant strains, respectively. Unlike chlorhexidine and mupirocin, available reports have not observed a link between PVP-I and the induction of bacterial resistance or cross-resistance to antiseptics and antibiotics. These preclinical findings also translate into clinical decolonization, where intranasal PVP-I significantly improved the efficacy of chlorhexidine wash and was as effective as mupirocin in reducing surgical site infection in orthopedic surgery. Overall, these qualities of PVP-I make it a useful alternative decolonizing agent for the prevention of S. aureus infections, but additional experimental and clinical data are required to further evaluate the use of PVP-I in this setting.

Detection and clinical relevance of Staphylococcus aureus nasal carriage: an update

Staphylococcus aureus nasal carriage is a well-defined risk factor of infection with this bacterium. The increased risk of S. aureus infection in nasal carriers is supported by the fact that the strains isolated from both colonization and infection sites are indistinguishable in most of the cases. Persistent nasal carriage seems to be associated with an increased risk of infection and this status could be defined now in clinical routine by using one or two quantitative nasal samples. There is evidence for supporting the detection of nasal carriage of S. aureus in patients undergoing cardiac surgery and in those undergoing hemodialysis in order to implement decolonization measures. More studies are needed to determine which carriers have the highest risk of infection and why decolonization strategies failed to reduce S. aureus infection in some other groups of patients.

Enteroviral capsid protein VP1 is present in myocardial tissues from some patients with myocarditis or dilated cardiomyopathy

BACKGROUND

There are still discrepancies in the association of enterovirus and myocardial disease, partially due to lack of data on the detection of virus antigens in tissues. It is desirable to localize enteroviral antigens so as to establish a link between the two and to study mechanisms of virus persistence.

METHODS AND RESULTS

Nineteen fixed explanted or postmortem myocardial samples were obtained from patients with myocarditis or dilated cardiomyopathy (DCM). Control samples were collected from 11 subjects who had died accidentally or of noncardiovascular disease. Viral antigen was detected by an improved immunohistochemical technique using an enterovirus group-specific antibody to viral capsid protein VP1. Nine of 11 myocarditis cases (81.8%) and 6 of 8 DCM cases (75%) were positive. Signals were localized in the cytoplasm of myocytes. Intense immunostaining was observed in acute myocarditis, whereas VP1 was detected in scattered myocytes in chronic myocarditis or DCM. Enteroviral RNA was detected in 6 of 11 myocarditis samples (54.5%) and 3 of 8 DCM samples (37.5%) by the reverse transcription-nested polymerase chain reaction, correlating with antigen detection (kappa=0.6+/-0.21). Neither viral antigen nor RNA was detected in any controls.

CONCLUSIONS

Our findings demonstrate a direct link between enterovirus infection and some myocarditis or DCM cases. The pattern of VP1 detection may correlate with disease stage and severity. The data suggest that viral protein synthesis may be involved in persistent enterovirus infection in the pathogenesis of DCM.

Use of flow cytometry to monitor Legionella viability

Legionella viability was monitored during heat shock treatment at 70 degrees C by a flow cytometric assay (FCA). After 30 min of treatment, for 6 of the 12 strains tested, the FCA still detected 10 to 25% of cells that were viable but nonculturable (VBNC). These VBNC cells were able to produce ATP and to be resuscitated after culture on amoebae.

Comparison of hepatitis C virus NS5b and 5' noncoding gene sequencing methods in a multicenter study

A national evaluation study was performed in 11 specialized laboratories with the objective of assessing their capacities to genotype hepatitis C virus (HCV) and define the applicability of a given genotyping method. The panel consisted of 14 samples positive for HCV RNA of different genotypes (including 3 samples with two different artificially mixed genotypes) and 1 HCV-negative sample. Seventeen sets of data were gathered from the 11 participating laboratories. The sensitivities ranged from 64.3 to 100% and from 42.7 to 85.7% for the methods that used sequencing of the NS5b region and the 5' noncoding (5' NC) region, respectively. When the data for the artificially mixed samples were excluded, NS5b genotyping gave correct results for 80% of the samples, 1.7% of the samples were misclassified, and 18.3% of the samples had false-negative results. By 5' NC-region genotyping methods, 58.3% of the results were correct, 29.7% were incomplete, 8.3% were misclassifications, 1.2% were false positive, and 2.4% were false negative. Only two procedures based on NS5b sequencing correctly identified one of the three samples with mixtures of genotypes; the other methods identified the genotype corresponding to the strain with the highest viral load in the sample. Our results suggest that HCV 5' NC-region genotyping methods give sufficient information for clinical purposes, in which the determination of the subtype is not essential, and that NS5b genotyping methods are more reliable for subtype determination, which is required in epidemiological studies.

Genotypic and phenotypic analysis of type III secretion system in a cohort of Pseudomonas aeruginosa bacteremia isolates: evidence for a possible association between O serotypes and exo genes

The type III secretion system (TTSS) of Pseudomonas aeruginosa was characterized genetically and phenotypically in 92 epidemiologically unrelated bacteremic strains. Four groups of strains (TTSS types) were defined according to the level of type III protein secretion and kinetics of cytotoxicity. Type 1 strains (n=26) were highly and rapidly cytotoxic and secreted ExoU, type 2 strains (n=48) exhibited slower cytotoxic rates and expressed ExoS but not ExoU, type 3 strains (n=14) were poorly cytotoxic, and type 4 strains (n=4) were not cytotoxic. Type 3 and 4 strains did not have detectable secretion phenotype; however, some type 4 strains were able to reach a level of cytotoxicity similar to that of type 1 and type 2 strains when complemented in trans by a functional exsA gene. A statistically significant association (P<.001) was found between TTSS types and detection of the mutually exclusive exoU and exoS genes. In addition, 24 of 25 serotype O:1, O:10, and O:11 strains contained exoU, whereas 54 of 55 serotype O:3, O:4, O:6, O:12, and O:16 strains contained exoS (P<.001). Our results demonstrate correlations among exoU or exoS genotype, TTSS phenotype, and O serotype in bacteremic P. aeruginosa isolates.

Early nasal type I IFN immunity against SARS-CoV-2 is compromised in patients with autoantibodies against type I IFNs

IFN-I and IFN-III immunity in the nasal mucosa is poorly characterized during SARS-CoV-2 infection. We analyze the nasal IFN-I/III signature, namely the expression of ISGF-3-dependent IFN-stimulated genes, in mildly symptomatic COVID-19 patients and show its correlation with serum IFN-α2 levels, which peak at symptom onset and return to baseline from day 10 onward. Moreover, the nasal IFN-I/III signature correlates with the nasopharyngeal viral load and is associated with the presence of infectious viruses. By contrast, we observe low nasal IFN-I/III scores despite high nasal viral loads in a subset of critically ill COVID-19 patients, which correlates with the presence of autoantibodies (auto-Abs) against IFN-I in both blood and nasopharyngeal mucosa. In addition, functional assays in a reconstituted human airway epithelium model of SARS-CoV-2 infection confirm the role of such auto-Abs in abrogating the antiviral effects of IFN-I, but not those of IFN-III. Thus, IFN-I auto-Abs may compromise not only systemic but also local antiviral IFN-I immunity at the early stages of SARS-CoV-2 infection.