Eosinophilic meningitis due to Angiostrongylus cantonensis (AC) is an emerging parasitic disease worldwide but remains endemic in the Pacific region. In New Caledonia, sporadic cases occur each year, and the route of transmission is often unclear. In January 2023, an unusual cluster of three cases occurred in a village on Lifou Island following week-long community festivities, leading to an epidemiological investigation to determine the outbreak scope, the source of contamination, and inform public health interventions. We conducted a retrospective epidemiological and environmental investigation in one month after the suspected exposure. Cases were defined according to international criteria and classified as confirmed, probable, or suspected. Clinical data, attendance at the festivities and food exposures were collected from medical records and interviews. Environmental observations focused on potential contamination sources in food preparation areas. Serological analyses were performed in symptomatic and asymptomatic exposed individuals. Descriptive statistics were used to summarize demographic, clinical, and exposure characteristics. Nineteen cases were identified, including three confirmed and sixteen suspected cases; no probable cases were identified. Headache was the predominant symptom, often associated with vomiting or paresthesias. All cases attended festivities on December 27, 2022 suggesting a common exposure during that day. The median incubation period was 3 weeks (IQR: 2–4). Two exposure hypotheses were identified: beverages diluted with rainwater and contamination of blended fruit juice. Environmental investigations revealed rats and gastropods around rainwater reservoirs and food preparation areas, including on utensils left to dry outdoors. No AC DNA was detected in water samples. Serology for AC was positive in all confirmed cases (3/3), in 13 of 14 tested suspected cases, and in all ten exposed asymptomatic individuals tested 9 months after the outbreak. This investigation highlights the diagnostic and epidemiological challenges of neuroangiostrongyliasis in endemic areas, where mild presentations often remain unconfirmed and where the value of serological testing is limited by the lack of baseline seroprevalence data. The findings support the hypothesis of accidental incorporation of a heavily infected gastropod into blended fruit juice during preparation, potentially facilitated by open-air kitchen practices in rural Pacific settings.

BACKGROUND:Carbapenemase-producing Enterobacterales (CPE) have been designated by the World Health Organization as critical global priority pathogens. Their widespread dissemination and nosocomial outbreaks pose a major public health threat. This study examined the transmission patterns and genetic characteristics of CPE isolated in New Caledonia between 2013 and 2022. METHODS:A total of 214 CPE isolates were collected, comprising 199 non-duplicate clinical isolates from 164 patients and 15 environmental isolates from hospital surfaces. Isolates were characterized using phenotypic methods and whole-genome sequencing. RESULTS:Among clinical isolates, the most prevalent genera was Enterobacter (n = 68; 34%) and Klebsiella (n = 50; 25%), with 194 isolates (98%) harbouring IMP-type carbapenemases. WGS of 89 selected CPE revealed the predominance of the blaIMP-4 gene (n = 82; 92%). This gene was primarily associated with IncM2-type plasmids carrying a class 1 integron, identified in 65 sequenced isolates. Long-read sequencing resolved these plasmids into seven distinct variants, differentiated by integron structures and a 9305-bp insertion. Genomic, phenotypic, and epidemiological triangulation have identified 12 hospital spread events, with 10 linked to IMP-4 IncM2 plasmids, whose transferability is confirmed by conjugation assays. CONCLUSION:These results highlighted the pivotal role of plasmid-mediated dissemination in CPE spread and emphasize the urgency of enhanced surveillance to curb silent transmission. The study provided critical insights for targeted infection control strategies in New Caledonia healthcare system, with broader implications for regional antimicrobial resistance containment.

Metal pollution poses significant ecological and economic concerns for many countries, resulting from anthropogenic activities such as intensive farming, mining, and other industrial sectors. Many of these metals can be toxic, affecting not only plant and animal nutrition but also human health. Phytoremediation of metal-polluted soils is now regarded as one of the most promising nature-based solutions for removing metals from contaminated environments. It can be enhanced by plant inoculation with beneficial microorganisms, such as arbuscular mycorrhizal fungi (AMF) and plant growth-promoting rhizobacteria (PGPR). For about two decades, the combined use of PGPR and AMF has attracted interest. This review summarizes the studies carried out on this subject, highlighting the complementary mechanisms of these two types of microbes and their synergistic effects, which improve the plant’s mineral nutrition and tolerance to heavy metals, as well as better metal neutralization through stabilization in the plant’s aerial and root organs and in the soil. Among these mechanisms, AMF intervene by mobilizing essential minerals due to their external mycelium, which explores a large volume of soil. AMF also contribute to reducing soil erosion through the soil-binding capacity of their extraradical mycelium and glomalin production, which enhances soil aggregation and stability. These symbionts contribute efficiently to metal toxicity alleviation in plants. PGPR can improve plant growth through various mechanisms, including hormone production, 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity, nitrogen fixation, and the secretion of different chelating substances. Metals can be neutralized by a variety of processes, including binding, biosorption, transformation, and immobilization. Mycorrhiza helper bacteria are associated with AMF and can stimulate their mycelial growth, spore production, and spore germination, thus increasing mycorrhizal colonization. The selection of bacteria and AMF for phytoremediation purposes should be based on these different complementary properties. Furthermore, genomic and transcriptomic studies may be utilized to identify the most active genes in terms of their positive effects on the plant and phytoremediation mechanisms. This approach enables a more rigorous selection of strains. Field experiments with co-inoculation of AMF and bacteria are rare at present and need to be developed in different edaphic and climatic conditions.

Background:Antimicrobial resistance (AMR) issues have emerged in New Caledonia, particularly involving methicillin-resistant Staphylococcus aureus (MRSA), and carbapenem-resistant Acinetobacter baumannii (CR-AB). However, a comprehensive overall picture is still required to guide an antimicrobial stewardship. Methods:A prospective collection of antimicrobial susceptibility testing results was performed over a 20-year period (2005-2024) in the Territorial Hospital Center, the main hospital in New Caledonia. This surveillance encompassed 22 different pathogens and 28 antimicrobial agents, covering 157 pathogen-drug combinations. Resistance rates over time were analyzed using logistic models. A focus was placed on high-priority pathogens, including MRSA, CR-AB, vancomycin-resistant Enterococcus faecium, ceftazidime-resistant Pseudomonas aeruginosa, extended-spectrum β-lactamase Enterobacterales (ESBL-E), and carbapenemase-producing Enterobacterales (CPE). Multidrug-resistant (MDR) and possible extensively drug-resistant (pXDR) isolates were also identified and characterized. Findings:Across 111,022 included isolates, emergences of resistance were observed, notably to penicillins, third-generation cephalosporins, tetracycline, and fusidic acid. Temporal resistance trends were described, along with outbreaks of MRSA and CR-AB, and the emergence of ESBL-E and CPE, representing 3.7% [95% CI: 3.5-3.8] (N = 2208), and 0.1% [95% CI: 0.1-0.2] (N = 85) of the 59,954 Enterobacterales isolates, respectively. Overall, 11% [95% CI: 10.8-11.1] were MDR and 0.6% [95% CI: 0.5-0.6] were pXDR. Interpretation:Through trend analyses, this surveillance highlighted both the emergence and decline of AMR across diverse bacterial pathogens, helping inform which antibiotics may remain appropriate as first-line options and addressing the lack of data from Pacific Island settings. Funding:This work received financial support from the Pierre Ledoux Jeunesse Internationale scholarship (Fondation de France) and the Institut Pasteur, Paris.

Paraburkholderia ultramafica STM10279T is a metal-tolerant rhizobacterium that promotes plant growth. It was isolated from the roots of Tetraria arundinaceae, a pioneer endemic tropical herb growing on ultramafic soils in New Caledonia. We have recently shown that the main mechanism of metal tolerance of P. ultramafica is related to the production of an acidic exopolysaccharide (EPS). To explore the potential role of this EPS in the plant’s environmental adaptation, we first elucidated its structure by employing a combination of chromatography and mass spectrometry techniques. These analyses revealed that the EPS is highly branched and composed of galactosyl (35.8%), glucosyl (33.2%), rhamnosyl (19.5%), mannosyl (7.2%), and glucuronosyl residues (4.4%), similar to the EPS of the Burkholderia cepacia complex known as cepacian. We subsequently conducted greenhouse experiments on Tetraria comosa plantlets inoculated with P. ultramafica or a solution of its EPS during transplanting onto ultramafic substrate. The data showed that the dry weight of T. comosa shoots was 2.5 times higher in the plants treated with the EPS compared to the unexposed plants. In addition, inductively coupled plasma–optical emission spectrometry (ICP-OES) analysis revealed that exposure to the EPS significantly increased Ca, Mg, K, and P uptake as well as K content in roots. In vitro experiments using the Pikovskaya method showed that the EPS was able to solubilize phosphorus. Consistent with the retention of metals in roots and a reduction in shoots, our data revealed a significant decrease in metal translocation factors (TFs) in the plants inoculated with the EPS. These results suggest a beneficial effect of the rhizobacterial EPS on plant growth and abiotic stress mitigation. In addition, the data suggest that the reduced levels of trace metals in plants exposed to P. ultramafica STM10279T are due to metal chelation by the EPS. Further investigations are needed to firmly demonstrate whether this EPS could be used as a biostimulant for plant growth and adaptation to ultramafic soils.

Carbapenemase-producing Enterobacterales (CPE) have been identified by the World Health Organization as global priority pathogens. The dissemination of these bacteria and outbreaks within healthcare facilities are of serious concern. This study investigated the transmission patterns and genetic characteristics of CPE isolated in New Caledonia from 2013 to 2022. The isolates were identified and characterized both phenotypically and whole-genome sequencing (WGS). In total 214 CPE were isolated: 199 non duplicate clinical isolates from 164 patients and 15 from hospital environmental surface. The most common genera in clinical samples were Enterobacter (34%) and Klebsiella (25%), with 194 isolates (98%) carrying IMP-type carbapenemase. WGS of 89 isolates revealed the dominance of the blaIMP-4 carbapenemase gene, found in 82 isolates. The blaIMP-4 was primarily predicted to be carried by IncL/M-type plasmid, found in 69% of the sequenced isolates. Our work revealed the circulation of 12 bacterial clusters with 61 strains involved in outbreaks or persistent over time. Genomic, phenotypic and clinical approaches identified 12 distinct outbreaks involving IMP producers. These results highlight the importance of studying plasmid transmission to better prevent silent spread of CPE. Ultimately, this study provides new guidelines for limiting the clinical spread of CPE in New Caledonia.

Our knowledge about New Caledonian serpentine ecosystems has increased greatly during the past half-century, mainly thanks to Jaffre's group. However, research on soil microflora and plant symbionts started only in the nineties and was mainly published during the last two decades. We aim to synthesize these studies, focusing particularly on arbuscular mycorrhizal fungi (AMF). Research on AMF consists firstly of a global and inventory approach aiming to produce a basic but essential lacking knowledge. These studies showed that AMF are abundant in ultramafic soils and concerned nearly all plant species of these ecosystems. Even Ni-hyperaccumulator plants and sedges, generally considered non-mycorrhizal, were found to be functionally colonized by AMF in New Caledonian ultramafic soils. The adaptation of AMF communities to the extreme conditions of these soils led to high levels of metal tolerance (particularly to Ni) and noticeable originality of the taxa. The influence of these symbionts on plant growth and adaptation was assessed in greenhouse and field conditions. An accurate selection of AMF isolates that improve plant growth, and plant metal tolerance was performed. It was demonstrated that combinations of AMF isolates with complementary functional traits showed highly synergistic effects on plant development. Finally, a partnership with a biotechnological company led to the production of an efficient commercial inoculant now used in the ecological restoration of mine-degraded areas. Today studies are focused mainly on the additive effects of AMF and mycorrhiza-helper bacteria.

The increase in carbapenem-resistant Enterobacterales (CRE) is mostly driven by the spread of carbapenemase-producing (CP) strains. In New Caledonia, the majority of carbapenemases found are IMP-type carbapenemases that are difficult to detect on routine selective media. In this study, a culture-based method with ertapenem selection is proposed to distinguish non-CRE, non-CP-CRE, and CP-CRE from samples with very high bacterial loads. Firstly, assays were carried out with phenotypically well-characterized β-lactam-resistant Enterobacterales isolates. Then, this approach was applied to clinical and environmental samples. Presumptive CP-CRE isolates were finally identified, and the presence of a carbapenemase was assessed. In a collection of 27 phenotypically well-characterized β-lactam-resistant Enterobacterales, an ertapenem concentration of 0.5 µg·mL−1 allowed distinguishing CRE from non-CRE. A concentration of 4 µg·mL−1 allowed distinguishing CP-CRE from non-CP-CRE after nine hours of incubation. These methods allowed isolating 18 CP-CRE from hospital effluents, including the first detection of a KPC in New Caledonia. All these elements show that this cost-effective strategy to distinguish β-lactam-resistant Enterobacterales provides fast and reliable results. This could be applied in the Pacific islands or other resource-limited settings, where limited data are available.

OBJECTIVE:Carbapenemase-producing Enterobacteriaceae (CRE) and Enterococcus faecium resistant to vancomycin (VRE) constitute major threats to public health worldwide. The Pacific area is concerned and has implemented strategies to control antimicrobial resistance (AMR). However, accurate epidemiological data are rarely reported. Our study aimed to present the strategies applied to prevent and control the spread of highly resistant bacteria in the Pacific territory of New Caledonia.PATIENTS AND METHODS:Cohort prospective study of all cases of highly resistant bacteria (HRB) isolated in New Caledonia from September 2004 to December 2020. Evaluation of the impact of the infection control measures implemented in healthcare settings: screening strategy, cohorting unit, IT tools and control of antibiotic prescriptions.RESULTS:A total of 346 patients with HRB were identified. Most of them (63.0%) were infected or colonized by VRE (n=218) and 128 by CRE. While the number of CREs significantly increased from 2013 to 2020 (P<0.0001), control procedures have limited their dissemination. Most patients were colonized by IMP-4-CRE (n=124/128). The incidence density of VRE significantly decreased from 38.52 for 100,000 hospitalisation-days in 2015 to 4.19 for 100,000 hospitalisation-days in 2019 due to systematic screening of patients before sanitary repatriation from Australia and cohorting implementation. The risk of VRE diffusion is now well under control.CONCLUSIONS:Our study confirms that it is possible to control the spread of AMR in a circumscribed territory by means of a global control strategy involving screening, cohorting unit, IT tools and antibiotic prescription controls.

OBJECTIVES:Since 2014, Staphylococcus aureus methicillin resistance has been rapidly increasing in New Caledonia and is associated with potential serious clinical repercussions. In the present study, we investigated the epidemiology of methicillin-resistant S. aureus (MRSA) in New Caledonia and the possible emergence of a particular clonal strain.METHODS:An overview of the distribution of MRSA in New Caledonia in 2019 is presented. We collected and analysed 171 clinical MRSA isolates from New Caledonia medical laboratories during August and September 2019. Among this collection, 49 representative isolates were analyzed by the French National Reference Center for Staphylococci using the StaphyType DNA microarray, allowing genetic characterization of the isolates.RESULTS:Among the 1144 S. aureus isolated over the year 2019, 442 isolates (39%) were resistant to methicillin, and 62% of these isolates were resistant to fusidic acid (FA). During the inclusion period, FA resistance rate was similar (60%). Genetic characterization evidenced CC6 as the predominant clonal complex (70%) with 26 isolates (53%) identified as CC6-MRSA-[IV+fus] (PVL+).CONCLUSIONS:These findings demonstrated a low diversity of MRSA in New Caledonia, with the dominance of a clonal complex not reported previously. The frequent fusidic acid (FA) resistance in MRSA was associated with a high prevalence of fusC gene, suggesting that FA misuse contributed to driving the selection of this clone. Our findings suggest the recommendation to stop the topical use of FA to control the emergence of this severe MRSA clone and decrease the rate of MRSA in New Caledonia.

The ecological restoration of nickel mining-degraded areas in New Caledonia is strongly limited by low availability of soil mineral nutrients, metal toxicity, and slow growth rates of native plant species. In order to improve plant growth for restoration programs, special attention was paid to interactions between plant and soil microorganisms. In this study, we evaluated the influence of inoculation with Curtobacterium citreum BE isolated from a New Caledonian ultramafic soil on arbuscular mycorrhizal symbiosis and growth of Tetraria comosa , an endemic sedge used in restoration programs . A greenhouse experiment on ultramafic substrate was conducted with an inoculum comprising two arbuscular mycorrhizal fungi (AMF) species isolated from New Caledonian ultramafic soils: Rhizophagus neocaledonicus and Claroideoglomus etunicatum . The effects on plant growth of the AMF and C. citreum BE inoculated separately were not significant, but their co-inoculation significantly enhanced the dry weight of T. comosa compared with the non-inoculated control. These differences were positively correlated with mycorrhizal colonization which was improved by C. citreum BE. Compared with the control, co-inoculated plants were characterized by better mineral nutrition, a higher Ca/Mg ratio, and lower metal translocation. However, for Ca/Mg ratio and metal translocation, there were no significant differences between the effects of AMF inoculation and co-inoculation.

In New Caledonia, one third of the main island is covered by ultramafic soils characterized by high levels of metals and low levels of plant nutrients. In these soils, metal tolerant bacteria may play a role in plant adaptation to the edaphic constraints. Recently, two new bacteria species belonging to the genus Burkholderia sensu lato were isolated from rhizospheric roots of pioneer plant growing in New Caledonian ultramafic soils and were able to tolerate high metal concentrations. The purpose of this study was to determine the major mechanisms by which these two bacteria were able to tolerate metals and if they were able to reduce metal absorption by plants from which they were isolated. Bioaccumulation, adsorption on cell surface, ability to form biofilm and production of exopolysaccharides were assessed. A focus was carried out on Ni, generally the most toxic metal in New Caledonian ultramafic soils. All experiments were performed in comparison with a reference strain isolated from a non-ultramafic habitat, Paraburkholderia caribensis MWAP64(T). The two ultramafic bacterial species showed a high tolerance to Ni with a Ni-IC50 of 5 mM for Caballeronia novacaledonica STM10272(T) and 30 mM for Paraburkholderia ultramafica STM10279(T), values significantly higher than those of P. caribensis MWAP64T (2 mM). The major mechanism involved in the bacterial Ni tolerance was related to biofilm formation for C. novacaledonica STM10272(T) and to acidic exopolysaccharide production for P. ultramafica STM10279(T). Both species alleviated metal contents in roots of Tetraria comosa, an endemic pioneer herbaceous species growing on New Caledonian ultramafic soils.

The present study focused on the characterization of 10 Curtobacterium citreum strains isolated from the rhizosphere of pioneer plants growing on ultramafic soils from New Caledonia. Taxonomic status was investigated using a polyphasic approach. Three strains (BE, BB, and AM) were selected in terms of multiple-metal resistance and plant-growth-promoting traits. They were tested on sorghum growing on ultramafic soil and compared with the reference strain C. citreum DSM20528T. To better understand the bacterial mechanisms involved, biosorption, bioaccumulation, and biofilm formation were investigated for the representative strain of the ultramafic cluster (strain BE) versus C. citreum DSM20528T. The polyphasic approach confirmed that all native isolates belong to the same cluster and are C. citreum. The inoculation of sorghum with strains BE and BB significantly reduced Ni content in shoots compared with inoculation with C. citreum DSM20528T and control values. This result was related to the higher Ni tolerance of the ultramafic strains compared with C. citreum DSM20528T. Ni biosorption and bioaccumulation showed that BE exhibited a lower Ni content, which is explained by the ability of this strain to produce exopolysaccharides involved in Ni chelation. We suggested that ultramafic C. citreum strains are more adapted to this substrate than is C. citreum DSM20528T, and their features allow them to enhance plant metal tolerance.