New Delhi metallo-β-lactamase-1-producing Citrobacter portucalensis belonging to the novel ST264 causing fatal sepsis in a vulnerable migratory sea turtle

The Gut Microbiome of the Asiatic Toad (Bufo gargarizans) Reflects Environmental Changes and Human Activities

Amphibians are extremely sensitive to environmental changes, and their gut microbiome may have different responses to environmental changes. Here, metagenomic sequencing was used to investigate the intestinal microbiota of the Asiatic toad (Bufo gargarizans) from three different habitats (city areas, transition areas, and wild areas) of Sichuan Province, China. The results showed that Proteobacteria, Firmicutes, and Fusobacteria were the main bacteria in the gut of B. gargarizans. There were significant differences in the composition and function of the gut microbiome among the samples from the three different habitats. Enterobacteriaceae showed significant changes in the three habitats and occupied a high relative abundance in the city areas, especially for Citrobacter. Especially, antibiotic resistance genes (ARGs) and virulence factors (VFs) were significantly increased in city areas. We performed de novo assembly of the metagenome-assembled genomes (MAGs). In total, 322 nonredundant MAGs were reconstructed, 304 of which might be potential novel genomes. Among the 13 species-level genome bins (SGBs) belonging to Enterobacteriaceae, the one belonging to Citrobacter portucalensis annotated the most types of ARGs and VFs. Phylogenetic and functional analyses of the assembled C. portucalensis MAG and public genome data were carried out, suggesting that it may play a potential role in intestinal diseases in amphibians. Our study revealed the differences in the gut microbiome of B. gargarizans across different habitats and suggests that amphibian intestinal microbiota could serve as environmental indicators to reflect environmental changes and human activities. The reconstructed MAGs expanded our understanding of the gut microbiota in amphibians, which may serve as a substantial reservoir for microbiome resources.

The curious case of the rare Citrobacter pasteurii isolated from an endangered primate in Brazil

The genus Citrobacter comprises clinically important human pathogens but has been less frequently associated with wildlife infections. Citrobacter pasteurii was first identified as causing human diarrhea and remains rarely documented. In this study, a Gram-negative bacterial strain, named A318, was identified as causing diarrhea in a black lion tamarin. This strain was biochemically identified as Trabulsiella guamensis, a species of unusual nature, and was submitted to whole-genome characterization. Curiously, phylogenomic analysis showed that A318 strain belonged to the genus Citrobacter, with confirmation of the species C. pasteurii by average nucleotide identity (99.02 %) and digital DNA-DNA hybridization (93.80 %) analyzes. Cases of misidentification of C. pasteurii as Citrobacter youngae were detected and corrected in this study. In addition to the genome sequence of the type strain of C. pasteurii, only two others from the Australian cockle and Portuguese silver gull are publicly available. Single nucleotide polymorphism differences among all C. pasteurii indicated a highly diverse population. No acquired antimicrobial resistance genes and plasmid replicons were found. Therefore, our findings emphasize the importance of gold-standard methods for accurate identification and underscores the importance of continued surveillance and research to mitigate the risks posed by zoonotic and zooanthroponotic pathogens.

Emergence of an Extensive Drug Resistant Citrobacter portucalensis Clinical Strain Harboring bla SFO-1, bla KPC-2, and bla NDM-1

Background

To explore the plasmid characteristics and transfer mechanisms of an extensive drug resistant (XDR) clinical isolate, Citrobacter portucalensis L2724hy, co-producing bla SFO-1, bla NDM-1, and bla KPC-2.

Methods

Species confirmation of L2724hy was achieved through 16S rRNA sequencing and Average Nucleotide Identity (ANI) analysis. Antimicrobial susceptibility testing (AST) employed the agar dilution and micro broth dilution methods. Identification of resistance genes was carried out by PCR and whole-genome sequencing (WGS). Essential resistance gene locations were verified by S1 nuclease pulsed-field gel electrophoresis (S1-PFGE) and southern hybridization experiments. Subsequent WGS data analysis delved into drug resistance genes and plasmids.

Results

The confirmation of the strain L2724hy as an extensive drug-resistant Citrobacter portucalensis, resistant to almost all antibiotics tested except polymyxin B and tigecycline, was achieved through 16S rRNA sequencing, ANI analysis and AST results. WGS and subsequent analysis revealed L2724hy carrying bla SFO-1, bla NDM-1, and bla KPC-2 on plasmids of various sizes. The uncommon ESBL gene bla SFO-1 coexists with the fosA3 gene on an IncFII plasmid, featuring the genetic environment IS26-fosA3-IS26-ampR-bla SFO-1-IS26. The bla NDM-1 was found on an IncX3 plasmid, coexisting with bla SHV-12, displaying the sequence IS5-IS3000-IS3000-Tn2-bla NDM-1-ble-trpF-dsbD-cutA-gros-groL, lacking ISAa125. The bla KPC-2 is located on an unclassified plasmid, exhibiting the sequence Tn2-tnpR-ISKpn27-bla KPC-2-ISKpn6-korC. Conjugation assays confirmed the transferability of both bla NDM-1 and bla KPC-2.

Conclusion

We discovered the coexistence of bla SFO-1, bla NDM-1, and bla KPC-2 in C. portucalensis for the first time, delving into plasmid characteristics and transfer mechanisms. Our finding highlights the importance of vigilant monitoring of drug-resistance genes and insertion elements in uncommon strains.

Successful expansion of hospital-associated clone of vanA-positive vancomycin-resistant Enterococcus faecalis ST9 to an anthropogenically polluted mangrove in Brazil

Mangrove ecosystems are hotspots of biodiversity, but have been threatened by anthropogenic activities. Vancomycin-resistant enterococci (VRE) are nosocomial bacteria classified as high priority by the World Health Organization (WHO). Herein, we describe the identification and genomic characteristics of a vancomycin-resistant Enterococcus faecalis strain isolated from a highly impacted mangrove ecosystem of the northeastern Brazilian, in 2021. Genomic analysis confirmed the existence of the transposon Tn1546-vanA and clinically relevant antimicrobial resistance genes, such as streptogramins, tetracycline, phenicols, and fluoroquinolones. Virulome analysis identified several genes associated to adherence, immune modulation, biofilm, and exoenzymes production. The UFSEfl strain was assigned to sequence type (ST9), whereas phylogenomic analysis with publicly available genomes from a worldwide confirmed clonal relatedness with a hospital-associated Brazilian clone. Our findings highlight the successful expansion of hospital-associated VRE in a mangrove area and shed light on the need for strengthening genomic surveillance of WHO priority pathogens in these vital ecosystems.