Listeria monocytogenes-associated spontaneous bacterial peritonitis in France: a nationwide observational study of 208 cases.

BACKGROUND: Listeriosis is a foodborne infection caused by Listeria monocytogenes. Three main forms of listeriosis are well characterised, but little is known about L monocytogenes-associated spontaneous bacterial peritonitis. We used data from the French national surveillance of listeriosis to perform a nationwide retrospective study. METHODS: All patients with L monocytogenes isolated by culture from a peritoneal fluid sample in France between April 1, 1993, and Dec 31, 2022, were included. Individuals for whom bacterial peritonitis was not confirmed and those who also had another type of invasive listeriosis were excluded. A standardised checklist was used to collect demographic, clinical, and biological data as well as antibiotic treatment and follow-up data. The primary outcome was to determine the characteristics of L monocytogenes-associated spontaneous bacterial peritonitis. We did descriptive analyses and assessed risk factors for 1-month mortality using an exploratory multivariable Cox model analysis. FINDINGS: Among the 8768 L monocytogenes cases reported, 208 (2%) were patients with L monocytogenes-associated spontaneous bacterial peritonitis. Mean age was 65 years (SD 13), 50 (24%) of 208 patients were female, and 158 (76%) were male (no data on race or ethnicity were available). 200 (98%) of 205 patients with L monocytogenes-associated spontaneous bacterial peritonitis with available data had immunosuppressive comorbidities, including cirrhosis (148 [74%] of 201 with available data), ongoing alcoholism (58 [62%] of 94), and ongoing neoplasia (60 [31%] of 195). Causes of ascites included cirrhosis (146 [70%] of 208), ongoing neoplasia (26 [13%]), end-stage heart failure (13 [6%]), and peritoneal dialysis (11 [5%]). Among those with available data, presentation was pauci-symptomatic and non-specific; only 67 (50%) of 135 patients presented with fever, 49 (37%) of 132 with abdominal pain, and 27 (21%) of 129 with diarrhoea. 61 (29%) of 208 patients were dead at 1 month, 92 (44%) were dead at 3 months, and 109 (52%) were dead at 6 months after diagnosis. Ongoing neoplasia (hazard ratio 2·42 [95% CI 1·05-5·56]; p=0·039), septic shock (8·03 [2·66-24·02]; p=0·0021), and high blood leukocyte count (1·05 [1·00-1·09]; p=0·045) were independently associated with 1-month mortality. INTERPRETATION: Despite the non-specific and mild presentation of L monocytogenes-associated spontaneous bacterial peritonitis, the outcome is poor and similar to that of neurolisteriosis, and so identification of L monocytogenes in ascitic fluid samples requires urgent parenteral amoxicillin-based treatment to avoid a fatal outcome. FUNDING: Institut Pasteur, Inserm, and French Public Health Agency. TRANSLATION: For the French translation of the abstract see Supplementary Materials section.

Phenotypic and genotypic antimicrobial resistance of Listeria monocytogenes: an observational study in France.

Background: Large-scale studies are needed to clarify antimicrobial resistance in the foodborne pathogen Listeria monocytogenes (Lm) and the effectiveness of listeriosis treatment options. Here we examined the antimicrobial resistance patterns in Lm over time and assessed genotype-phenotype concordances. Methods: We analyzed 5339 Lm isolates (2908 clinical and 2431 food isolates) collected in France and overseas territories, between 2012 and 2019. Whole genome sequencing was performed for all isolates and antimicrobial resistance profiles inferred from draft assemblies. Antimicrobial susceptibility towards 22 antimicrobials was determined for all clinical isolates, and in food isolates with acquired resistance genes. Findings: All tested isolates were resistant to at least 3 different classes of antimicrobials, consistent with Lm intrinsic traits. Acquired antimicrobial resistance in Lm was rare (2.23% isolates) and more prevalent in food (mainly lineage II) compared to clinical isolates (mainly lineage I) (3.74% vs 0.98%, p < 0.0001), and in isolates with disinfectants or stress resistance traits (e.g. bcrABC, 20.20% vs 7.20%, p < 0.0001), suggesting co-selection of resistance in food-production environments. Acquired antimicrobial resistance could be predicted from genomes with high accuracy (>99%), except for ciprofloxacin. Acquired antimicrobial phenotypes were towards tetracyclines (mostly due to tetM), trimethoprim (dfrD), lincosamides (lnuG), macrolides (ermB, mphB) and phenicols (fexA). Interpretation: The reference treatment for listeriosis (aminopenicillins/aminoglycosides) remains effective, with no acquired resistance observed. Continuous surveillance of antimicrobial resistance in clinical and food isolates is crucial to detect the emergence of novel resistance. Funding: Institut Pasteur, INSERM, Santé Publique France, Investissement d'Avenir program Laboratoire d'Excellence 'Integrative Biology of Emerging Infectious Diseases' (ANR-10-LABX-62-IBEID).

Genome-Based Characterization of Listeria monocytogenes, Costa Rica.

Genomic data on the foodborne pathogen Listeria monocytogenes from Central America are scarce. We analyzed 92 isolates collected during 2009-2019 from different regions in Costa Rica, compared those to publicly available genomes, and identified unrecognized outbreaks. Our findings suggest mandatory reporting of listeriosis in Costa Rica would improve pathogen surveillance.

Fatal neonatal listeriosis following L. monocytogenes horizontal transmission highlights neonatal susceptibility to orally acquired listeriosis.

We report a case of fulminant fatal neonatal listeriosis due to horizontal transmission of Listeria monocytogenes (Lm) in a neonatal double room. Genomic analyses reveal a close genetic relationship between clinical isolates, supporting cross-contamination. Oral inoculation experiments in adult and neonatal mice show that neonates are susceptible to a low Lm inoculum and that this susceptibility results from the immaturity of the neonatal gut microbiota. Infected neonates should therefore be isolated for as long as they shed Lm in their feces to avoid horizontal transmission and its dire consequences.

Genomic characterization of Listeria spp. isolated from tonsils, udder and feces of domestic dairy ruminants in Spain.

Two species of Listeria are pathogenic, Listeria monocytogenes and Listeria ivanovii. Although studies have shown that dairy ruminants shed Listeria spp. in feces, there is little information about ruminants that do not shed Listeria spp. in their feces but asymptomatically carry them in organs. We evidence that ruminants can asymptomatically carry L. ivanovii in udders and L. monocytogenes and L. ivanovii in tonsils without fecal shedding. Whole-genome sequence of L. monocytogenes and L. ivanovii contained known core genes involved in virulence and antibiotic resistance. This work highlights tonsils and udders as a Listeria intra-host site of colonization.

Listeria ilorinensis sp. nov., isolated from cow milk cheese in Nigeria.

During microbial assessment of cow milk cheese products in the city of Ilorin, Nigeria, a Listeria-like isolate was detected that could not be assigned to any known species. Whole-genome sequence analyses against all currently known 26 Listeria species confirmed that this isolate constitutes a new taxon within the genus Listeria, with highest similarity to Listeria costaricensis (average nucleotide identity blast of 82.66%, in silico DNA-DNA hybridization of 28.3%). Phenotypically, it differs from L. costaricensis by the inability to ferment sucrose, l-fucose and starch. The absence of haemolysis and Listeria pathogenic islands suggest that this novel species is not pathogenic for humans and animals. The name Listeria ilorinensis sp. nov. is proposed, with the type strain CLIP 2019/01311T (=CIP 111875T=DSM 111566T).

Listeria-Associated Lymphadenitis: A Series of 11 Consecutive Cases and Review of the Literature.

We studied 11 cases of culture-proven Listeria-associated lymphadenitis reported to the French National Reference Center for Listeria from 1994 to 2019 and 8 additional published cases. Listeria-associated lymphadenitis is rare, but it is associated with a mortality as high as for invasive listeriosis, and it is frequently diagnosed with concomitant neoplasia.

Neonatal Listeriosis Presentation and Outcome: A Prospective Study of 189 Cases.

BACKGROUND: Listeriosis is caused by the foodborne pathogen Listeria monocytogenes. It can present as a maternal-neonatal infection. We implemented a nationwide prospective cohort and analyzed the features of neonatal listeriosis. METHODS: We studied all neonates born alive from mothers with microbiologically proven maternal-neonatal listeriosis enrolled from November 2009 to December 2017. We analyzed presentation, neonatal outcome at discharge, and predictors of severe presentation and outcome. RESULTS: We studied 189 infants; 133 of 189 (70%) had abnormal clinical status at birth, including acute respiratory distress in 106 of 189 (56%). There were 132 of 189 (70%) infants who developed early-onset listeriosis and 12 of 189 (6%) who developed late-onset listeriosis; all presented with acute meningitis. There were 17 of 189 (9%) infants who had major adverse outcomes: 3%, (5 of 189) death; 6% (12 of 189), severe brain injury; and 2% (3 of 189), severe bronchopulmonary dysplasia. Fifteen of 17 infants were born <34 weeks of gestation (P < .0001 vs infants born ≥34 weeks of gestation). Maternal antimicrobial treatment ≥1 day before delivery was associated with a significant decrease in presentation severity for the infant, resulting in significantly fewer inotropic drugs, fluid resuscitation, and mechanical ventilation requirement (odds ratio, 0.23; 95% confidence interval, 0.09-0.51; P < .0001). CONCLUSIONS: Antenatal maternal antimicrobial treatment is associated with reduced neonatal listeriosis severity, justifying the prescription of preemptive maternal antimicrobial therapy when maternal-fetal listeriosis is suspected. Neonatal outcome is better than reported earlier, and its major determinant is gestational age at birth. CLINICAL TRIALS REGISTRATION: NCT01520597.

Ruminant-associated Listeria monocytogenes isolates belong preferentially to dairy-associated hypervirulent clones: a longitudinal study in 19 farms.

Studies have shown that ruminants constitute reservoirs of Listeria monocytogenes, but little is known about the epidemiology and genetic diversity of this pathogen within farms. Here we conducted a large-scale longitudinal study to monitor Listeria spp. in 19 dairy farms during three consecutive seasons (N = 3251 samples). L. innocua was the most prevalent species, followed by L. monocytogenes. Listeria monocytogenes was detected in 52.6% of farms and more frequently in cattle (4.1%) and sheep (4.5%) than in goat farms (0.2%). Lineage I accounted for 69% of L. monocytogenes isolates. Among animal samples, the most prevalent sublineages (SL) and clonal complexes (CC) were SL1/CC1, SL219/CC4, SL26/CC26 and SL87/CC87, whereas SL666/CC666 was most prevalent in environmental samples. Sixty-one different L. monocytogenes cgMLST types were found, 28% common to different animals and/or surfaces within the same farm and 21% previously reported elsewhere in the context of food and human surveillance. Listeria monocytogenes prevalence was not affected by farm hygiene but by season: higher prevalence was observed during winter in cattle, and during winter and spring in sheep farms. Cows in their second lactation had a higher probability of L. monocytogenes faecal shedding. This study highlights dairy farms as a reservoir for hypervirulent L. monocytogenes.

Listeria valentina sp. nov., isolated from a water trough and the faeces of healthy sheep.

In the context of a study on the occurrence of Listeria species in an animal farm environment in Valencia, Spain, six Listeria-like isolates could not be assigned to any known species. Phylogenetic analysis based on the 16S rRNA gene and on 231 Listeria core genes grouped these isolates in a monophyletic clade within the genus Listeria, with highest similarity to Listeria thailandensis. Whole-genome sequence analyses based on in silico DNA-DNA hybridization, the average nucleotide blast and the pairwise amino acid identities against all currently known Listeria species confirmed that these isolates constituted a new taxon within the genus Listeria. Phenotypically, these isolates differed from other Listeria species mainly by the production of acid from inositol, the absence of acidification in presence of methyl α-d-glucoside, and the absence of α-mannosidase and nitrate reductase activities. The name Listeria valentina sp. nov. is proposed for this novel species, and the type strain is CLIP 2019/00642T (=CIP 111799T=DSM 110544T).

Author Correction: Hypervirulent Listeria monocytogenes clones' adaptation to mammalian gut accounts for their association with dairy products.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Listeria monocytogenes-associated endovascular infections: A study of 71 consecutive cases.

BACKGROUND: Listeria monocytogenes-associated endovascular infections are not well characterized. METHODS: Retrospective study of 71 culture-proven cases reported to the French National Reference Center for Listeria from 1993 to 2018. RESULTS: Seventy-one cases were identified: 42 with vascular aneurysms/prosthetic infections, 27 with endocarditis, 2 with both. Fifty-eight were men (82%); median age was 75 years [46-92]; 93% reported co-morbidities (66/71), including 50% with immunosuppressive conditions. Vascular infections consisted of infected aneurysms (68%) or prosthetic graft infections (32%); vascular rupture was reported in 25/42 (60%). Tissue samples grew L. monocytogenes in 98% (43/44) and blood cultures in 64% (27/42). Endocarditis cases involved prosthetic or native valves or intracardiac devices in respectively 62% (18/29), 28% (8/29) and 10% (3/29). Infected valves were aortic (62%, 16/26), mitral (31%, 8/26) or both (8%, 2/26); 38% patients required surgery; 45% displayed heart failure; 17% had concomitant neurolisteriosis. In-hospital mortality in vascular infections was 12% (5/42) and 41% (12/29) for Lm-associated endocarditis. CONCLUSIONS: Endovascular listeriosis is a rare but severe infection. It manifests as vascular infections and endocarditis, mostly in older patients with vascular or cardiac valve prosthetic devices and co-morbidities. Mortality in Lm-associated endocarditis is twice higher than with other pathogens, requiring prompt recognition and treatment.

Hypervirulent Listeria monocytogenes clones' adaption to mammalian gut accounts for their association with dairy products.

Listeria monocytogenes (Lm) is a major human and animal foodborne pathogen. Here we show that hypervirulent Lm clones, particularly CC1, are strongly associated with dairy products, whereas hypovirulent clones, CC9 and CC121, are associated with meat products. Clone adaptation to distinct ecological niches and/or different food products contamination routes may account for this uneven distribution. Indeed, hypervirulent clones colonize better the intestinal lumen and invade more intestinal tissues than hypovirulent ones, reflecting their adaption to host environment. Conversely, hypovirulent clones are adapted to food processing environments, with a higher prevalence of stress resistance and benzalkonium chloride tolerance genes and a higher survival and biofilm formation capacity in presence of sub-lethal benzalkonium chloride concentrations. Lm virulence heterogeneity therefore reflects the diversity of the ecological niches in which it evolves. These results also have important public health implications and may help in reducing food contamination and improving food consumption recommendations to at-risk populations.

Listeria thailandensis sp. nov.

During a screening of Listeria species in food samples in Thailand, a Listeria-like bacterium was recovered from fried chicken and could not be assigned to any known species. Phylogenetic analysis based on the 16S rRNA gene and on 243 Listeria core genes placed the novel taxon within the Listeria aquatica, Listeria floridensis, Listeria fleishmannii and Listeria costaricensis clade (Listeria sensu lato), with highest similarity to L. floridensis (98.9 %) and L. costaricensis (98.8 %). Whole-genome sequence analyses based on the average nucleotide blast identity (ANI<86 %), the pairwise amino acid identity (AAI>64 %) and on the percentage of conserved proteins (POCP>77 %) with currently known Listeria species confirmed that the strain constituted a new taxon within the genus Listeria. At the phenotypical level, it differs from other Listeria species by the production of acid from d-tagatose and inositol. The name Listeria thailandensis sp. nov. is proposed for the novel species, and is represented by the type strain CLIP 2015/00305T (=CIP 111635T=DSM 107638T).

Listeria costaricensis sp. nov.

A bacterial strain isolated from a food processing drainage system in Costa Rica fulfilled the criteria as belonging to the genus Listeria, but could not be assigned to any of the known species. Phylogenetic analysis based on the 16S rRNA gene revealed highest sequence similarity with the type strain of Listeria floridensis (98.7 %). Phylogenetic analysis based on Listeria core genomes placed the novel taxon within the Listeria fleishmannii, L. floridensis and Listeria aquatica clade (Listeria sensu lato). Whole-genome sequence analyses based on the average nucleotide blast identity (ANI<80 %) indicated that this isolate belonged to a novel species. Results of pairwise amino acid identity (AAI>70 %) and percentage of conserved proteins (POCP>68 %) with currently known Listeria species, as well as of biochemical characterization, confirmed that the strain constituted a novel species within the genus Listeria. The name Listeria costaricensis sp. nov. is proposed for the novel species, and is represented by the type strain CLIP 2016/00682T (=CIP 111400T=DSM 105474T).

MALDI-TOF mass spectrometry-based identification of Listeria species in surveillance: A prospective study.

This study aimed to evaluate MALDI-TOF MS for species discrimination of Listeria in the context of routine surveillance. MALDI-TOF MS yielded 100% accuracy for the identification of L. monocytogenes, L. innocua, L. ivanovii, L. fleischmannii, L. grayi, L. seeligeri, L. weihenstephanensis and L. welshimeri, as confirmed by whole genome sequence analyses.

Spontaneous Loss of Virulence in Natural Populations of Listeria monocytogenes.

The pathogenesis of Listeria monocytogenes depends on the ability of this bacterium to escape from the phagosome of the host cells via the action of the pore-forming toxin listeriolysin O (LLO). Expression of the LLO-encoding gene (hly) requires the transcriptional activator PrfA, and both hly and prfA genes are essential for L. monocytogenes virulence. Here, we used the hemolytic activity of LLO as a phenotypic marker to screen for spontaneous virulence-attenuating mutations in L. monocytogenes Sixty nonhemolytic isolates were identified among a collection of 57,820 confirmed L. monocytogenes strains isolated from a variety of sources (0.1%). In most cases (56/60; 93.3%), the nonhemolytic phenotype resulted from nonsense, missense, or frameshift mutations in prfA Five strains carried hly mutations leading to a single amino acid substitution (G299V) or a premature stop codon causing strong virulence attenuation in mice. In one strain, both hly and gshF (encoding a glutathione synthase required for full PrfA activity) were missing due to genomic rearrangements likely caused by a transposable element. The PrfA/LLO loss-of-function (PrfA-/LLO-) mutants belonged to phylogenetically diverse clades of L. monocytogenes, and most were identified among nonclinical strains (57/60). Consistent with the rare occurrence of loss-of-virulence mutations, we show that prfA and hly are under purifying selection. Although occurring at a low frequency, PrfA-/LLO- mutational events in L. monocytogenes lead to niche restriction and open an evolutionary path for obligate saprophytism in this facultative intracellular pathogen.

Real-Time Whole-Genome Sequencing for Surveillance of Listeria monocytogenes, France.

During 2015-2016, we evaluated the performance of whole-genome sequencing (WGS) as a routine typing tool. Its added value for microbiological and epidemiologic surveillance of listeriosis was compared with that for pulsed-field gel electrophoresis (PFGE), the current standard method. A total of 2,743 Listeria monocytogenes isolates collected as part of routine surveillance were characterized in parallel by PFGE and core genome multilocus sequence typing (cgMLST) extracted from WGS. We investigated PFGE and cgMLST clusters containing human isolates. Discrimination of isolates was significantly higher by cgMLST than by PFGE (p<0.001). cgMLST discriminated unrelated isolates that shared identical PFGE profiles and phylogenetically closely related isolates with distinct PFGE profiles. This procedure also refined epidemiologic investigations to include only phylogenetically closely related isolates, improved source identification, and facilitated epidemiologic investigations, enabling identification of more outbreaks at earlier stages. WGS-based typing should replace PFGE as the primary typing method for L. monocytogenes.