Factors linked to Staphylococcus aureus healthcare-associated infections among pediatric intensive care unit colonized patients.

BACKGROUND: Staphylococcus aureus (SA) is one of the main pathogens responsible for healthcare-associated infection (HCAI) in pediatrics. The aim of this study was to describe the prevalence of SA-HCAI among colonized patients and the factors associated with it in the pediatric intensive care unit (PICU). METHODS: We designed a 6-year retrospective cohort study of a PICU in a French university children's hospital including all children admitted to the PICU from January 1, 2011, to December 31, 2016, who had SA colonization on PICU admission. For each patient, the past medical history and the hospitalization data were collected. HCAIs related to SA were verified according to the criteria of the United States Centers for Disease Control and Prevention. RESULTS: Among all patients colonized with SA (n = 1381, 26%), 105 (8%) had methicillin-resistant SA carriage and 41 (3%) developed an HCAI caused by SA. The main HCAIs were ventilator-associated pneumonia (51%) and central line-associated bloodstream infections (27%). Patients developing HCAI caused by SA had a significantly longer length of hospital stay and a higher mortality rate than the rest of the population. Using a multivariate logistic regression model, the presence of mechanical ventilation, the implementation of a surgical procedure during the PICU stay, and the onset of at least one episode of anemia during the PICU stay were significantly associated with the occurrence of HCAI due to SA. CONCLUSION: HCAIs linked to SA carriage are rare but severe. Mechanical ventilation, surgery during the PICU stay, and anemia are factors associated with SA-HCAI.

Comparison between enzyme-linked immunospot assay and intracellular cytokine flow cytometry assays for the evaluation of T cell response to SARS-CoV-2 after symptomatic COVID-19.

INTRODUCTION: Evaluation of different cell-based assays for the study of adaptive immune responses against SARS-CoV-2 is crucial for studying long-term and vaccine-induced immunity. METHODS: Enzyme-linked immunospot assay (ELISpot) and intracellular cytokine staining (ICS) using peptide pools spanning the spike protein and nucleoprotein of SARS-CoV-2 were performed in 25 patients who recovered from paucisymptomatic (n = 19) or severe COVID-19 (n = 6). RESULTS: The proportion of paucisymptomatic patients with detectable SARS-CoV-2 T cells was low, as only 44% exhibit a positive T cell response with the ICS and 67% with the ELISpot. The magnitude of SARS-CoV-2 T cell responses was low, both with ICS (median at 0.12% among total T cells) and ELISpot (median at 61 SFCs/million peripheral blood mononuclear cells [PBMC]) assays. Moreover, T cell responses in paucisymptomatic patients seemed lower than among patients with severe disease. In the paucisymptomatic patients, the two assays were well correlated with 76% of concordant responses and a Cohen's kappa of 55. Furthermore, in four patients SARS-CoV-2 T cells were detected by ELISpot but not with ICS. Short-term culture could improve the detection of specific T cells. CONCLUSIONS: In patients who recovered from paucisymptomatic COVID-19, the proportion of detectable anti-SARS-CoV-2 responses and their magnitude seemed lower than in patients with more severe symptoms. The ELISpot appeared to be more sensitive than the ICS assay. Short-term culture revealed that paucisymptomatic patients had nonetheless few SARS-CoV-2 T cells at a very low rate in peripheral blood. These data indicate that various ex-vivo assays may lead to different conclusions about the presence or absence of SARS-CoV-2 T cell immunity.

Does the use of intrawound povidone-iodine irrigation and local vancomycin powder impact surgical site infection rate in adolescent idiopathic scoliosis surgery?

PURPOSE: Surgical site infection (SSI) is a major complication after adolescent idiopathic scoliosis (AIS) surgery, with an incidence ranging from 0.5 to 7%. Intraoperative wound decontamination with povidone-iodine (PVP-I) irrigation and/or vancomycin powder in adult spinal surgery has gained attention in the literature with controversial results. The aim of this study was to investigate the impact of using intrawound PVP-I irrigation and local vancomycin powder (LVP) on the incidence of early SSI in AIS surgery. METHODS: All AIS patients who underwent posterior spinal fusion between October 2016 and December 2019 were retrospectively reviewed. The incidence of early SSI was reported and compared between 2 groups defined by the treating spinal surgeons' preferences: group 1-intrawound irrigation with 2L of PVP-I and application of 3 g LVP before closure and control group 2-patients that did not receive either of these measures. RESULTS: Nine early cases of SSI (2.9%) were reported among the 307 AIS posterior spinal fusion patients. Incidence of SSI in group 1 (2/178 = 1.1%) was significantly lower than in group 2 (7/129 = 5.4%; p = 0.04). There were no adverse reactions to the use of PVP-I and LVP in our study. At latest follow-up, rate of surgical revision for mechanical failure with pseudarthrosis was significantly lower in group 1 (2/178 = 1.1%) than in group 2 (9/129 = 7.0%; p = 0.01). CONCLUSION: Intraoperative use of intrawound PVP-I irrigation and vancomycin powder is associated with a significant reduction of early SSI after AIS spine surgery. LEVEL OF EVIDENCE IV: Retrospective study.

Case Report: Hyperammonemic Encephalopathy Linked to Ureaplasma spp. and/or Mycoplasma hominis Systemic Infection in Patients Treated for Leukemia, an Emergency Not to Be Missed.

Background: Hyperammonemic encephalopathy caused by Ureaplasma spp. and Mycoplasma hominis infection has been reported in immunocompromised patients undergoing lung transplant, but data are scarce in patients with hematological malignancies. Case Presentation: We describe the cases of 3 female patients aged 11-16 years old, developing initially mild neurologic symptoms, rapidly evolving to coma and associated with very high ammonia levels, while undergoing intensive treatment for acute leukemia (chemotherapy: 2 and hematopoietic stem cell transplant: 1). Brain imaging displayed cerebral edema and/or microbleeding. Electroencephalograms showed diffuse slowing patterns. One patient had moderate renal failure. Extensive liver and metabolic functions were all normal. Ureaplasma spp. and M. hominis were detected by PCR and specific culture in two patients, resulting in prompt initiation of combined antibiotics therapy by fluoroquinolones and macrolides. For these 2 patients, the improvement of the neurological status and ammonia levels were observed within 96 h, without any long-term sequelae. M. hominis was detected post-mortem in vagina, using 16S rRNA PCR for the third patient who died of cerebral edema. Conclusion: Hyperammonemic encephalopathy linked to Ureaplasma spp. and M. hominis is a rare complication encountered in immunocompromised patients treated for acute leukemia, which can lead to death if unrecognized. Combining our experience with the few published cases (n=4), we observed a strong trend among female patients and very high levels of ammonia, consistently uncontrolled by classical measures (ammonia-scavenging agents and/or continuous kidney replacement therapy). The reversibility of the encephalopathy without sequelae is possible with prompt diagnosis and adequate combined specific antibiotherapy. Any neurological symptoms in an immunocompromised host should lead to the measurement of ammonia levels. If increased, and in the absence of an obvious cause, it should prompt to perform a search for Ureaplasma spp. and M. hominis by PCR as well as an immediate empirical initiation of combined specific antibiotherapy.

A Microbiota-Dependent Response to Anticancer Treatment in an In Vitro Human Microbiota Model: A Pilot Study With Hydroxycarbamide and Daunorubicin.

Background: Anticancer drug efficacy is linked to the gut microbiota's composition, and there is a dire need to better understand these interactions for personalized medicine. In vitro microbiota models are promising tools for studies requiring controlled and repeatable conditions. We evaluated the impact of two anticancer drugs on human feces in the MiniBioReactor Array (MBRA) in vitro microbiota system. Methods: The MBRA is a single-stage continuous-flow culture model, hosted in an anaerobic chamber. We evaluated the effect of a 5-day treatment with hydroxycarbamide or daunorubicine on the fecal bacterial communities of two healthy donors. 16S microbiome profiling allowed analysis of microbial richness, diversity, and taxonomic changes. Results: In this host-free setting, anticancer drugs diversely affect gut microbiota composition. Daunorubicin was associated with significant changes in alpha- and beta-diversity as well as in the ratio of Firmicutes/Bacteroidetes in a donor-dependent manner. The impact of hydroxycarbamide on microbiota composition was not significant. Conclusion: We demonstrated, for the first time, the impact of anticancer drugs on human microbiota composition, in a donor- and molecule-dependent manner in an in vitro human microbiota model. We confirm the importance of personalized studies to better predict drug-associated-dysbiosis in vivo, linked to the host's response to treatment.

Reassessing the Performance of the "Step-By-Step" Approach to Febrile Infants 90 Days of Age and Younger in the Context of the COVID-19 Pandemic: A Multicentric Retrospective Study.

BACKGROUND: Infants with COVID-19 can often present with fever without source, which is a challenging situation in infants <90 days old. The "step-by-step" algorithm has been proposed to identify children at high risk of bacterial infection. In the context of the COVID-19 pandemic, we aimed to reassess the diagnostic performance of this algorithm. METHODS: We performed a multicentric retrospective study in 3 French pediatric emergency departments between 2018 and 2020. We applied the "step-by-step" algorithm to 4 clinical entities: COVID-19, febrile urinary tract infections (FUTI), invasive bacterial infection (IBI), and enterovirus infections. The main outcome was the proportion of infants classified at high risk (ill-appearing, ≤21 days old, with leukocyturia or procalcitonin level ≥0.5 ng/mL). RESULTS: Among the 199 infants included, 40 had isolated COVID-19, 25 had IBI, 60 had FUTI, and 74 had enterovirus infection. All but 1 infant with bacterial infection were classified at high risk (96% for IBI and 100% for FUTI) as well as 95% with enterovirus and 82% with COVID-19. Infants with COVID-19 were classified at high risk because an ill-appearance (72%), an age ≤21 days (27%), or leukocyturia (19%). All these infants had procalcitonin values <0.5 ng/mL and only 1 had C-reactive protein level >20 mg/L. CONCLUSIONS: The "step-by-step" algorithm remains effective to identify infants with bacterial infection but misclassifies most infants with COVID-19 as at high risk of bacterial infection leading to unnecessary cares. An updated algorithm based adding viral testing may be needed to discriminate fever related to isolated COVID-19 in infants <90 days old.

The interplay between anticancer challenges and the microbial communities from the gut.

Cancer being an increasing burden on human health, the use of anticancer drugs has risen over the last decades. The physiological effects of these drugs are not only perceived by the host's cells but also by the microbial cells it harbors as commensals, notably the gut microbiota. Since the early '50 s, the cytotoxicity of anticancer chemotherapy was evaluated on bacteria revealing some antimicrobial activities that result in an established perturbation of the gut microbiota. This perturbation can affect the host's health through dysbiosis, which can lead to multiple complications, but has also been shown to have a direct effect on the treatment efficiency.We, therefore, conducted a review of literature focusing on this triangular relationship involving the microbial communities from the gut, the host's disease, and the anticancer treatment. We focused specifically on the antimicrobial effects of anticancer chemotherapy, their impact on mutagenesis in bacteria, and the perspectives of using bacteria-based tools to help in the diagnostic and treatment of cancer.

Correction to: Is Cutibacterium acnes early surgical site infection rate related to the duration of antibiotic prophylaxis in adolescent idiopathic scoliosis surgery?

Unfortunately, the authors first name and family name were incorrectly swapped in the original publication. The complete correct names of the author group is given below.

Is Cutibacterium acnes early surgical site infection rate related to the duration of antibiotic prophylaxis in adolescent idiopathic scoliosis surgery?

PURPOSE: Cutibacterium acnes (C. acnes) is a gram-positive anaerobic bacillus located in pilosebaceous glands, usually responsible for late postoperative surgical site infections (SSI). A recent study performed in our institution highlighted an unexpected emergence of C. acnes early SSI. One potential explanation was the change of the perioperative antibioprophylaxis (ATB) protocol, which switched from 48 h postoperative cefamandole to intraoperative only cefazoline. The aim of this study was therefore to investigate the influence of the ATB duration on the occurrence of C. acnes early SSI, by comparing the incidence rates during 3 consecutive ATB protocols. METHODS: Between January 2007 and September 2017, all patients who underwent posterior fusion for AIS were retrospectively reviewed. Early C. acnes SSI were reported and compared between 3 periods, during which the ATB protocols were modified. January 2007-February 2012: Intraoperative Cefamandole continued 48 h (protocol 1) March 2012-August 2016: Single shot of intraoperative Cefazoline (protocol 2) September 2016-September 2017: Intraoperative Cefazoline continued 48 h (protocol 3). RESULTS: Fifty-three early SSI (7.2%) were reported among the 732 posterior AIS fusions included. Global incidence of C. acnes infection was 2.9%. The incidence of C. acnes in early SSI increased from 0 to 4.9% between protocol 1 and 2, but was reduced to 1.7% with protocol 3. CONCLUSIONS: Early C acnes SSI can be explained by the difficulty to eradicate this pathogen with current skin preparation procedures and some Beta-lactam antibiotics tolerance. Longer duration antibioprophylaxis is preferable to prevent from early C. acnes SSI.

Respiratory pathogens and acute chest syndrome in children with sickle cell disease.

BACKGROUND: Acute chest syndromes (ACS) may be associated with upper respiratory tract infections, but the epidemiology of viral and intracellular respiratory pathogens in children with sickle cell disease (SCD) is not precisely known. The aim of this study was to describe the epidemiology of viral and intracellular respiratory pathogens in children with SCD presenting with fever and/or ACS. MATERIALS AND METHODS: An observational, prospective, single-centre cohort study with nested case-control analysis was conducted on children with SCD admitted from October 2016 to October 2017 for fever and/or ACS to the paediatric department of Robert Debré university hospital, Paris, France. They were screened for 20 respiratory pathogens by a multiplex PCR in the nasopharynx (FilmArray). RESULTS: We included 101 children. M/F sex ratio of 0.45. The median age was 3.2 years (IQR: 1.4-8.2). At least one pathogen was isolated in 67 patients (67%). The most frequent viruses were as follows: rhinovirus (n=33), adenovirus (n=14), respiratory syncytial virus (n=13) and parainfluenza viruses (n=11). Mycoplasma pneumoniae was detected in one case. Twenty-three (23%) presented with or developed ACS. A nested case-control analysis was performed, after pairing ACS with non-ACS children for age and inclusion period. There was no statistical association between any viral detection or multiple viral infection, and ACS (p=0.51) even though parainfluenza viruses were twice as common in ACS. CONCLUSIONS: Viral detection in febrile children with SCD is frequent, but its association with ACS was not demonstrated. In this study, M. pneumoniae was rare in young children with SCD experiencing ACS.

Impact of anticancer chemotherapy on the extension of beta-lactamase spectrum: an example with KPC-type carbapenemase activity towards ceftazidime-avibactam.

Through their action on DNA replication, anticancer chemotherapies could increase the basal mutation rate in bacteria and increase the risk of selecting antibiotic resistant mutants. We investigated the impact of several drugs on a beta-lactamase model using KPC-type carbapenemase-producing Enterobacteriaceae. We studied the impact of anticancer chemotherapies used in pediatric hematologic malignancies on 7 clinical isolates of Enterobacteriaceae producing KPC-type carbapenemases. We compared the mutation rates from cultures with/without chemotherapy on ceftazidime-avibactam, rifampicin and ceftazidime-avibactam combined with meropenem media. Mechanisms of ceftazidime-avibactam resistance were explored on a subset of mutants. After exposure to some cytotoxic molecules, the bacterial mutation rates leading to ceftazidime-avibactam and to rifampicin resistance increased up to 104-fold while we observed no emergence of resistant mutants (frequency of <10-10) on a meropenem combined with ceftazidime-avibactam media. Compared to the parental strains, an increased susceptibility to meropenem was observed in the ceftazidime-avibactam resistant mutants. The blaKPC genes of ceftazidime-avibactam mutants harbored either mutations, deletions or insertions, especially in the region encoding the Ω-loop of the KPC-type carbapenemase. Anticancer chemotherapy can increase the mutation rates of bacteria accelerating the extension of KPC-type carbapenemases towards ceftazidime-avibactam, one of the last resort antimicrobial chemotherapy.

Group A Streptococcal Paronychia and Blistering Distal Dactylitis in Children: Diagnostic Accuracy of a Rapid Diagnostic Test and Efficacy of Antibiotic Treatment.

Among 174 children with blistering distal dactylitis or paronychia, 36.2% had a positive group A Streptococcus (GAS) rapid detection antigen. For GAS, the outcome for patients who received amoxicillin was favorable in all cases without any surgical procedures; 44.6% of cases due to Staphylococcus aureus infection (38.7%) required surgery.

Cord blood procalcitonin level and early-onset sepsis in extremely preterm infants.

Early-onset neonatal sepsis (EOS) is observed in 1.7% of extremely preterm infants, with high morbidity and mortality rate. Cord blood procalcitonin (PCT) is a sensitive marker of EOS in full-term newborns, but it has been rarely studied in premature infants. The diagnostic value of cord blood PCT by immunofluorescence has been assessed as an early marker of EOS in a prospective cohort of extremely preterm infants, with a threshold at 0.5 µg/L. EOS was defined by a positive bacterial culture or by the association of postnatal biological/clinical signs of EOS and antibiotic treatment for more than 72 h. Correlation between PCT serum concentrations and postnatal morbidities was also analyzed. Among a total of 186 infants, 45 (24%) were classified as EOS. Blood PCT concentration was ≤ 0.5 µg/L in 114 infants, including 11 EOS (9.6%) and PCT was > 0.5 µg/L in 72 babies including 34 EOS (47.2%). PCT concentration > 0.5 µg/L was associated with higher risk of EOS (OR 2.18; CI95% 1.58-3.02; p < 0.0001). The receiver operating characteristic curve determined a cutoff of 0.7 µg/L as the best compromise, with an area under the curve of 0.75 (sensitivity 69%, specificity 70%). In multivariate analysis, clinical chorioamnionitis was associated with PCT concentration > 0.5 µg/L (OR 2.58; CI95% 1.35-4.94; p = 0.004). Cord blood PCT is a marker significantly associated with EOS in extremely preterm infants, but its sensitivity remains low. Its added value in combination with other early marker of EOS needs to be further investigated in this high-risk population.

Does Staphylococcus aureus nasal decontamination affect the rate of early surgical site infection in adolescent idiopathic scoliosis surgery?

PURPOSE: Surgical site infection (SSI) is a main complication after adolescent idiopathic scoliosis (AIS) surgery. Nasal colonization with S. aureus is a known risk factor for developing nosocomial infections in cardiac surgery. However, the risk in orthopedic surgery remains unclear, especially in spine surgery. This study aims to report the efficacy of a preoperative nasal decontamination program in S. aureus carriers on the incidence of early SSI after AIS posterior surgery. METHODS: Between January 2014 and July 2017, all AIS patients were screened preoperatively with nasal swabs and decontaminated if positive 5 days before surgery. Early SSI was identified, and microorganisms findings were analyzed within nasal carriage and compared to a previous series published before the decontamination program (2007-2011). RESULTS: Among the 331 AIS posterior fusion performed during the study period, incidence of positive nasal swab was 23% (n = 75). Those were preoperatively decontaminated. In comparison with the period before the nasal decontamination program, incidence of S. aureus early SSI significantly decreased from 5.1 to 1.3%, p < 0.05. None of those S. aureus decontaminated patients had an early S. aureus SSI. In all cases of S. aureus infections, S. aureus nasal screening was negative with a mean delay of 315 days (± 115) before surgery, which was significantly different from the global cohort (104 days ± 67, p < 0.05). CONCLUSIONS: Preoperative S. aureus nasal decontamination was associated with a significant decrease in S. aureus SSI. Optimal delay of nasal screening needs to be optimized in order to diagnose intermittent S. aureus carriers. These slides can be retrieved under Electronic Supplementary Material.

Arthritis in children: comparison of clinical and biological characteristics of septic arthritis and juvenile idiopathic arthritis.

AIM: Childhood arthritis arises from several causes. The aim of this observational study is to compare the clinical and biological features and short-term outcome of different types of arthritis because they have different treatment and prognoses. METHODS: Children <16 years of age hospitalised in a French tertiary care centre for a first episode of arthritis lasting for less than 6 weeks who underwent joint aspiration were retrospectively included. We performed non-parametrical tests to compare groups (septic arthritis (SA), juvenile idiopathic arthritis (JIA) and arthritis with no definitive diagnosis). The time before apyrexia or C reactive protein (CRP) <10 mg/L was analysed using the Kaplan-Meier method. RESULTS: We studied 125 children with a sex ratio (M/F) of 1.1 and a median age of 2.2 years (range 0.3 to 14.6). SA was associated with a lower age at onset (1.5 years, IQR 1.2-3.0 vs 3.6 years, IQR 2.2-5.6), shorter duration of symptoms before diagnosis (2 days, IQR 1-4 vs 7 days, IQR 1-19) and higher synovial white blood cell count (147 cells ×103/mm3, IQR 71-227, vs 51 cells ×103/mm3, IQR 12-113), than JIA. Apyrexia occurred later in children with JIA (40% after 2 days, 95% CI 17% to 75%) than children with SA (82%, 95% CI 68% to 92%), as did CRP<10 mg/L (18% at 7 days, 95% CI 6.3% to 29.6% vs 82.1%, 95% CI 76.1% to 89.7%, p=0.01). CONCLUSIONS: There were no sufficiently reliable predictors for differentiating between SA and JIA at onset. The outcomes were different; JIA should be considered in cases of poor disease evolution after antibiotic treatment and joint aspiration.

Surgical Site Infections in Pediatric Spine Surgery: Comparative Microbiology of Patients with Idiopathic and Nonidiopathic Etiologies of Spine Deformity.

BACKGROUND: Surgical site infections (SSIs) are a concern in pediatric spine surgery with unusually high rates for a clean surgery and especially for patients with deformity of nonidiopathic etiology. Microbiologic differences between etiologies of spine deformities have been poorly investigated. METHODS: We reviewed all cases of SSI in spinal surgery between 2007 and 2011. Characteristics of cases and of bacteria according to the etiology of the spine disease were investigated. RESULTS: Of 496 surgeries, we identified 51 SSIs (10.3%) in 49 patients. Staphylococcus aureus was the most frequent pathogen whatever the etiology (n = 31, 61% of infection cases). The second most frequent pathogens vary according to the etiology of the spine deformity. It was Gram-negative bacilli (GNB) in nonidiopathic cases (n = 19, 45% of cases) and anaerobe in idiopathic cases (n = 8, 38% of cases), particularly Gram-positive anaerobic cocci (n = 5, 24% of cases). Infection rate was 6.8% in cases with idiopathic spine disease (n = 21) and 15.9% in cases with nonidiopathic spine disease (n = 30). Nonidiopathic cases were more frequently male with lower weight. American Society of Anesthesiologists score was more often greater than 2, they had more frequently sacral implants and postoperative intensive care unit stay. GNB were significantly associated with a nonidiopathic etiology, low weight, younger age and sacral fusion. SSIs were polymicrobial in 31% of cases with a mean of 1.4 species per infection cases. CONCLUSION: S. aureus is the first cause of SSI in pediatric spine surgery. However, Gram-positive anaerobic cocci should be taken into account in idiopathic patients and GNB in nonidiopathic patients when considering antibiotic prophylaxis and curative treatment.

Escherichia coli virulence patterns may help to predict vesicoureteral reflux in paediatric urinary tract infections.

AIM: Ultrasound and biological tools are used to predict high-grade vesicoureteral reflux, but other markers are needed to better select patients who need voiding cystography. Our aim was to determine whether studying Escherichia coli virulence factors would help to predict vesicoureteral reflux in patients with their first acute pyelonephritis. METHODS: We included children presenting with E. coli-related acute pyelonephritis or cystitis. Vesicoureteral reflux was assessed by voiding cystography. Virulence factors were identified by multiplex polymerase chain reaction. Statistical analysis was performed using logistic regression and the mean c-statistic test. RESULTS: We included 198 patients: 30 with cystitis and 168 with acute pyelonephritis, including 46 with vesicoureteral reflux. High-grade reflux was associated with acute pyelonephritis caused by the E. coli lacking virulence factors papGII (82% versus 47%, p < 0.001) or papC (85% versus 53%, p < 0.001) or belonging to phylogenetic group A or B1. When we added genetic data (lack of papGII, fyuA and phylogenetic groups) to classical predictors of vesicoureteral reflux (ultrasound examination, gender, age), the ability to predict high-grade reflux increased, with the c-statistic rising from 0.88 to 0.93. CONCLUSION: Bacterial virulence factors and clinical factors helped to predict high-grade reflux and may help to avoid unnecessary voiding cystographies.

Nod2 regulates the host response towards microflora by modulating T cell function and epithelial permeability in mouse Peyer's patches.

Nucleotide oligomerisation domain 2 (NOD2) mutations are associated with susceptibility to Crohn's disease and graft-versus-host disease, two human disorders related with dysfunctions of Peyer's patches (PPs). In Nod2(-/-) mice transcellular permeability and bacterial translocation are increased in PPs. In this study, we show that both anti-CD4(+) and anti-interferon gamma (anti-IFNgamma) monoclonal antibodies abrogate this phenotype and reduce the expression of tumour necrosis factor (TNF) receptor 2 and the long isoform of myosin light chain kinase, thus demonstrating that immune T cells influence the epithelial functions. In turn, intraperitoneal injection of ML-7 (a myosin light chain kinase inhibitor) normalises the values of CD4(+) T cells, IFNgamma and TNFalpha. This reciprocal cross-talk is under the control of the gut microflora as shown by the normalisation of all parameters after antibiotic treatment. Toll-like receptor 2 (TLR2) and TLR4 expression were increased in Nod2(-/-) mice under basal conditions and TLR2 and TLR4 agonists induced an increased transcellular permeability in Nod2(+/+) mice. Muramyldipeptide (a Nod2 agonist) or ML-7 was able to reverse this phenomenon. It thus appears that Nod2 modulates the cross-talk between CD4(+) T cells and the epithelium recovering PP and that it downregulates the pro-inflammatory effect driven by the ileal microflora, likely by inhibiting the TLR pathways.

Similarity and divergence among adherent-invasive Escherichia coli and extraintestinal pathogenic E. coli strains.

Adherent-invasive Escherichia coli (AIEC) pathovar strains, which are associated with Crohn's disease, share many genetic and phenotypic features with extraintestinal pathogenic E. coli (ExPEC) strains, but little is known about the level of genetic similarity between the two pathovars. We aimed to determine the frequency of strains with the "AIEC phenotype" among a collection of ExPEC strains and to further search for a common phylogenetic origin for the intestinal and extraintestinal AIEC strains. The adhesion, invasion, and intramacrophage replication capabilities (AIEC phenotype) of 63 ExPEC strains were determined. Correlations between virulence genotype and AIEC phenotype and between intestinal/extraintestinal origin, serotype, and phylogroup were evaluated for the 63 ExPEC and 23 intestinal AIEC strains. Phylogenetic relationships between extraintestinal and intestinal AIEC strains were determined using multilocus sequence typing (MLST) and pulsed-field gel electrophoresis. Only four (6.35%) ExPEC strains, belonging to the O6:H1, O83:H1, and O25:H4 serotypes, were classified as having an AIEC phenotype. These strains were found to be genetically related to some intestinal AIEC strains of the same serotypes as revealed by MLST. No particular virulence gene sets correlated with the intestinal/extraintestinal origin of the strains or with the AIEC phenotype, whereas the gene sets did correlate with the serogroup. We identified two intestinal AIEC strains and one extraintestinal AIEC strain belonging to the O25:H4 serotype that also belonged to the emerging and virulent clonal group ST131. In conclusion, the ExPEC and AIEC pathovars share similar virulence gene sets, and certain strains are phylogenetically related. However, the majority of ExPEC strains did not behave like AIEC strains, thus confirming that the AIEC pathovar possesses virulence-specific features that, to date, are detectable only phenotypically.