Search

International audience; Advances in whole-genome sequencing (WGS) technologies have documented genetic diversity and epidemiology of the major foodborne pathogen Listeria monocytogenes (Lm) in Europe and North America, but data concerning South America are scarce. Here, we examined the population structure and genetic diversity of this major foodborne pathogen collected in Brazil. Based on core genome multilocus sequence typing (cgMLST), isolates from lineages I (n = 22; 63%) and II (n = 13; 37%) were distributed into 10 different sublineages (SLs) and represented 31 new cgMLST types (CTs). The most prevalent SLs were SL9 (n = 9; 26%), SL3 (n = 6; 17%) and SL2 and SL218 (n = 5; 14%). Isolates belonging to CTs L2-SL9-ST9-CT4420 and L1-SL315-ST520-CT4429 were collected 3 and 9 years apart, respectively, revealing long-term persistence of Lm in Brazil. Genetic elements associated with stress survival were present in 60% of isolates (57% SSI-1 and 3% SSI-2). Pathogenic islands were present in 100% (LIPI-1), 43% (LIPI-3) and 6% (LIPI-4) of the isolates. Mutations leading to premature stop codons were detected in the prfA and inlA virulence genes. This study is an important contribution to understanding the genomic diversity and epidemiology of Lm in South America. In addition, the results highlight the importance of using WGS to reveal Lm long-term persistence.

International audience; Background: The recent outbreak of Zika virus (ZIKV) infection and the associated increased prevalence of microcephaly in Brazil underline the impact of viral infections on embryo-fetal development. The aim of the present study is to provide a detailed clinical and histopathological study of the fetal disruption caused by the ZIKV, with a special focus on the associated neuropathological findings. Methods: A detailed feto-placental examination, as well as neuropathological and neurobiological studies were performed on three fetuses collected after pregnancy termination between 22 and 25 weeks of gestation (WG), because brain malforma-tions associated with a maternal and fetal ZIKV infection was diagnosed. Results: In all three cases, the maternal infection occurred during the first trimester of pregnancy. A small head was observed on the ultrasound examination of the second trimester of pregnancy and led to the diagnosis of ZIKV fetopathy and pregnancy termination. The fetal histopathological examination was unremarkable on the viscera but showed on the testis an interstitial lymphocytic infiltrate. The placenta contained a Hofbauer cells hyperplasia with signs of inflammation. Neu-ropathological findings included a meningoencephalitis and an ex vacuo hydrocepha-lus. Immunohistochemical studies showed the presence of T lymphocytic and histiocytic meningitis associated with an abundant cerebral astroglial and macrophagic reaction. In situ hybridization demonstrated, abundant ZIKV particles within the cerebral parenchyma mainly in the ventricular/subventricular zone and in the cortical plate. In addition massive cells death and endoplasmic reticulum damage were present. Conclusion: The present study reports on the clinical and histopathological findings observed in three fetuses infected by the ZIKV. It emphasizes the severity of brain damages and the minimal visceral and placental changes observed upon ZIKV infection. This confirms the selective neurotropism of ZIKV. Finally, it allows us to describe the cascade of multifactorial developmental defects leading to microcephaly.

Summary Listeria monocytogenes is a bacterial pathogen classified into distinct serovars (SVs) based on somatic and flagellar antigens. To correlate phenotype with genetic variation, we analyzed the wall teichoic acid (WTA) glycosylation genes of SV 1/2, 3 and 7 strains, which differ in decoration of the ribitol-phosphate backbone with N-acetylglucosamine (GlcNAc) and/or rhamnose. Inactivation of lmo1080 or the dTDP-l-rhamnose biosynthesis genes rmlACBD (lmo1081–1084) resulted in loss of rhamnose, whereas disruption of lmo1079 led to GlcNAc deficiency. We found that all SV 3 and 7 strains actually originate from a SV 1/2 background, as a result of small mutations in WTA rhamnosylation and/or GlcNAcylation genes. Genetic complementation of different SV 3 and 7 isolates using intact alleles fully restored a characteristic SV 1/2 WTA carbohydrate pattern, including antisera reactions and phage adsorption. Intriguingly, phage-resistant L. monocytogenes EGDe (SV 1/2a) isolates featured the same glycosylation gene mutations and were serotyped as SV 3 or 7 respectively. Again, genetic complementation restored both carbohydrate antigens and phage susceptibility. Taken together, our data demonstrate that L. monocytogenes SV 3 and 7 originate from point mutations in glycosylation genes, and we show that phage predation represents a major driving force for serovar diversification and evolution of L. monocytogenes.

Listeria monocytogenes is ubiquitously prevalent in natural environments and is transmitted via the food chain to animals and humans, in whom it can cause life-threatening diseases. We used Multilocus Sequence Typing (MLST) of ∼2000 isolates of L. monocytogenes to investigate whether specific associations existed between clonal complexes (CCs) and the environment versus diseased hosts. Most CCs (72%) were not specific for any single source, and many have been isolated from the environment, food products, animals as well as from humans. Our results confirm that the population structure of L. monocytogenes is largely clonal and consists of four lineages (I-IV), three of which contain multiple CCs. Most CCs have remained stable for decades, but one epidemic clone (CC101) was common in the mid-1950s and very rare until recently when it may have begun to re-emerge. The historical perspective used here indicates that the central sequence types of CCs were not ancestral founders but have rather simply increased in frequency over decades.

The gut is a major barrier against microbes and encloses various innate lymphoid cells (ILCs), including two subsets expressing the natural cytotoxicity receptor NKp46. A subset of NKp46(+) cells expresses retinoic acid receptor-related orphan receptor γt (RORγt) and produces IL-22, like lymphoid tissue inducer (LTi) cells. Other NKp46(+) cells lack RORγt and produce IFN-γ, like conventional Natural Killer (cNK) cells. The identity, the regulation and the in vivo functions of gut NKp46(+) ILCs largely remain to be unravelled. Using pan-genomic profiling, we showed here that small intestine (SI) NKp46(+)RORγt(-) ILCs correspond to SI NK cells. Conversely, we identified a transcriptional programme conserved in fetal LTi cells and adult SI NKp46(+)RORγt(+) and NKp46(-)RORγt(+) ILCs. We also demonstrated that the IL-1β/IL-1R1/MyD88 pathway, but not the commensal flora, drove IL-22 production by NKp46(+)RORγt(+) ILCs. Finally, oral Listeria monocytogenes infection induced IFN-γ production in SI NK and IL-22 production in NKp46(+)RORγt(+) ILCs, but only IFN-γ contributed to control bacteria dissemination. NKp46(+) ILC heterogeneity is thus associated with subset-specific transcriptional programmes and effector functions that govern their implication in gut innate immunity.

There is a causal association between Helicobacter pylori (Hp) gastric infection and the development of gastric MALT lymphoma. In contrast, the link between Hp gastric infection and the development of extragastric lymphoma has not been thoroughly investigated. We, therefore, studied the prevalence of gastric Hp infection at initial diagnosis of ophthalmologic and nonophthalmologic extragastric lymphoma patients. Three cohorts of patients were studied: a first one of 83 patients with OAL, a second one of 101 patients with extraophthalmologic extragastric lymphoma, and a third one of 156 control individuals (control) without malignant lymphoma. Gastric Hp infection was investigated by histopathological analysis and Hp-specific PCR assay on gastric biopsy tissue samples. We found gastric Hp infection in 37 OAL patients (45%), in 25 extraophthalmologic extragastric lymphoma cases (25%), and in 18 controls individuals (12%) (P < 0.0001 OAL/C and P < 0.01 OAL/extra-OAL cases). Gastritis was found in 51% and 9% of Hp-positive and Hp-negative lymphoma patients, respectively (P < 10−4). Gastric Hp infection only correlated with MALT/LPL lymphoma (P = 0.03). There is a significant association between gastric Hp infection and MALT/LPL OAL. This suggests a novel mechanism of indirect infection-associated lymphomagenesis whereby chronic local antigen stimulation would lead to the emergence of ectopic B-cell lymphoma. © 2010 Wiley-Liss, Inc. Am. J. Hematol.

International audience; By comparative genomics, we have identified a gene of the intracellular pathogen Listeria monocytogenes that encodes an LPXTG surface protein absent from nonpathogenic Listeria species. This gene, vip, is positively regulated by PrfA, the transcriptional activator of the major Listeria virulence factors. Vip is anchored to the Listeria cell wall by sortase A and is required for entry into some mammalian cells. Using a ligand overlay approach, we identified a cellular receptor for Vip, the endoplasmic reticulum (ER) resident chaperone Gp96 recently shown to interact with TLRs. The Vip-Gp96 interaction is critical for bacterial entry into some cells. Comparative infection studies using oral and intravenous inoculation of nontransgenic and transgenic mice expressing human E-cadherin demonstrated a role for Vip in Listeria virulence, not only at the intestine level but also in late stages of the infectious process. Vip thus appears as a new virulence factor exploiting Gp96 as a receptor for cell invasion and/or signalling events that may interfere with the host immune response in the course of the infection.

Listeria monocytogenes is a Gram-positive intracellular bacterium responsible for severe opportunistic infections in humans and animals. Signature-tagged mutagenesis (STM) was used to identify a gene named fbpA, required for efficient liver colonization of mice inoculated intravenously. FbpA was also shown to be required for intestinal and liver colonization after oral infection of transgenic mice expressing human E-cadherin. fbpA encodes a 570-amino-acid polypeptide that has strong homologies to atypical fibronectin-binding proteins. FbpA binds to immobilized human fibronectin in a dose-dependent and saturable manner and increases adherence of wild-type L. monocytogenes to HEp-2 cells in the presence of exogenous fibronectin. Despite the lack of conventional secretion/anchoring signals, FbpA is detected using an antibody generated against the recombinant FbpA protein on the bacterial surface by immunofluorescence, and in the membrane compartment by Western blot analysis of cell extracts. Strikingly, FbpA expression affects the protein levels of two virulence factors, listeriolysin O (LLO) and InlB, but not that of InlA or ActA. FbpA co-immunoprecipitates with LLO and InlB, but not with InlA or ActA. Thus, FbpA, in addition to being a fibronectin-binding protein, behaves as a chaperone or an escort protein for two important virulence factors and appears as a novel multifunctional virulence factor of L. monocytogenes.

Pasteurella are commensal gram-negative bacteria isolated from the oral cavity of many domesticated animals. Most human infections occur post animal bite or scratch injury resulting in local cutaneous infection; however, case reports suggest that transmission may occur via animal secretions. Pasteurella species can be associated with serious systemic infections particularly in those with underlying disease and in the immunocompromised. We present a case of invasive Pasteurella multocida sinusitis in an immunocompromised renal transplant patient most likely acquired from a pet dog through direct mucosal inoculation via licking.

Listeria monocytogenes is an intracellular foodborne pathogen that causes listeriosis, an infection characterized by gastroenteritis, meningitis, encephalitis, and maternofetal infections in humans. L. monocytogenes enters the host via contaminated foods, invades the small intestine, translocates to mesenteric lymph nodes, and spreads to the liver, spleen, brain and, in pregnant women, the fetoplacental unit. Many pathogenicity tests for studying L. monocytogenes have been developed, including tests using laboratory animals. A number of small animal species can be experimentally infected with Listeria. Mice and guinea pigs can be infected either intragastrically or intravenously, and virulence evaluated either by enumerating bacteria within infected target organs or by evaluating the 50% lethal dose (LD50). Although mice and guinea pigs can be infected with Listeria by a variety of routes, the intragastric route is the most relevant to the human foodborne listeriosis.