Fernandez Do Porto, D. | bioRxiv Science

bioRxiv2024

Genome sequence and characterization of a hypervirulent BI/NAP1/027 Clostridioides difficile (CDC20121308)

Clostridioides difficile is a gram-positive bacterium implicated in antibiotic-associated diarrhea. The use of antibiotics alters the gut microbiota, rendering the host susceptible to infection by C. difficile. This pathogen colonizes the large intestine of humans and animals leading to asymptomatic carriage or clinical manifestations such as toxic megacolon and fulminant colitis depending on a wide range of pathogen and host factors. The emergence of BI/NAP1/027 strains in North America and the spread of these hypervirulent ribotypes worldwide have been linked to the increase in incidence and severity of C. difficile infections (CDI) over the last decade. In this work, we aimed to characterize the BI/NAP1/027 C. difficile commercial strain CDC20121308 widely employed in the study of host-pathogen interactions. The genome sequence was obtained using a whole-genome shotgun strategy. A total of 3,717 coding sequences (CDS) and 45 tRNAs were predicted. The annotation of the CDC20121308 strain identified 26% of CDS into RAST subsystems. We also detected the presence of RT 027 lineage markers such as thyA, cdtA, cdtB and tcdC 18bp-deletion. Moreover, the genome of CDC20121308 had 11 genes devoted to resistance to toxic compounds, antibiotics (e.g. Tetracycline (Tet) and Vancomycin (Van)) and disinfecting agents as predicted using CARD. C. difficile CDC20121308 resistance to Van and Tet was confirmed by broth microdilution assay. Crystal violet staining demonstrated biofilm formation, which could be associated with antibiotic resistance and pathogenicity. Additionally, we observed a spreading diffuse growth in soft agar tubes, suggesting a motile phenotype. Lastly, a genomic region containing Type 4 Secretory System components such as virD4, virB4, and virB6 was identified. In conclusion, our results allowed a genomic and functional characterization of the BI/NAP1/027 C. difficile CDC20121308 strain. We demonstrated the presence of several genes associated with pathogenesis that were validated by experimental assays. This study provides additional data for the use of this highly virulence commercial strain of epidemiological relevance in research works involving in vitro and in vivo approaches.

bioinformatics↗

bioRxiv2023

Fever like temperature impacts on Staphylococcus aureus and Pseudomonas aeruginosa interaction, physiology, and virulence both in vitro and in vivo

BackgroundStaphylococcus aureus and Pseudomonas aeruginosa cause a wide variety of bacterial infections and coinfections, showing a complex interaction that involves the production of different metabolites and metabolic changes. Temperature is a key factor for bacterial survival and virulence and within the host, bacteria could be exposed to an increment in temperature during fever development. We analyzed the previously unexplored effect of fever-like temperatures (39{degrees}C) on S. aureus USA300 and P. aeruginosa PAO1 microaerobic mono- and co-cultures compared with 37{degrees}C, by using RNAseq and physiological assays including in-vivo experiments. ResultsIn general terms both temperature and co-culturing had a strong impact on both PA and SA with the exception of the temperature response of monocultured PA. We studied metabolic and virulence changes on both species. Altered metabolic features at 39{degrees}C included arginine biosynthesis and the periplasmic glucose oxidation in S. aureus and P. aeruginosa monocultures respectively. When PA co-cultures were exposed at 39{degrees}C they upregulated ethanol oxidation related genes along with an increment in organic acid accumulation. Regarding virulence factors, monocultured SA showed an increase in the mRNA expression of the agr operon and hld, pms and pms{beta} genes at 39{degrees}C. Supported by mRNA data, we performed physiological experiments and detected and increment in hemolysis, staphylxantin production and a decrease in biofilm formation at 39{degrees}C. On the side of PA monocultures, we observed increase in extracellular lipase and protease and biofilm formation at 39{degrees}C along with a decrease in motility in correlation with changes observed at mRNA abundance. Additionally, we assessed host-pathogen interaction both in-vitro and in-vivo. S. aureus monocultured at 39{degrees}C showed a decrease in cellular invasion and an increase in IL-8 -but not in IL-6- production by A549 cell line. PA also decreased its cellular invasion when monocultured at 39{degrees}C and did not induce any change in IL-8 or IL-6 production. PA strongly increased cellular invasion when co-cultured at 37{degrees}C and 39{degrees}C. Finally, we observed increased lethality in mice intranasally inoculated with S. aureus monocultures pre-incubated at 39{degrees}C and even higher levels when inoculated with co-cultures. The bacterial burden for P. aeruginosa was higher in liver when the mice were infected with co-cultures previously incubated at 39{degrees}C comparing with 37{degrees}C. ConclusionOur results highlight a relevant change in the virulence of bacterial opportunistic pathogens exposed to fever-like temperatures in presence of competitors, opening new questions related to bacteria-bacteria and host-pathogen interactions and coevolution.

microbiology↗