Biology subjects

Bonacorsi, S.

Publications and source records attributed to Bonacorsi, S..

3 recordsLinked to original sources

bioRxiv2025

Exploring mutational possibilities of KPC variants to reach high level resistance to cefiderocol

IntroductionKlebsiella pneumoniae carbapenemase (KPC) is one of the most widespread carbapenemases, with over 242 variants identified. Some, like KPC-33 (D179Y), resist both ceftazidime-avibactam (CZA) and cefiderocol but show only a moderate cefiderocol MIC increase. KPCs success stems from its genetic adaptability, enabling mutation accumulation and necessitating proactive resistance monitoring. This study investigates the mutational possibilities for three KPC variants to develop high-level cefiderocol resistance. MethodUsing random mutagenesis and enrichment selection over a 10-day cefiderocol exposure at increasing concentration, we investigated the mutational potential of KPC-2, KPC-3, and KPC-33 to develop high-level cefiderocol resistance. Resistance mechanisms were then analyzed through phenotypic testing and sequencing. ResultsRandom mutagenesis generated 10, 10, and 105 mutants for blaKPC-2, blaKPC- 3, and blaKPC-33, respectively. After ten days of increasing cefiderocol exposure, MICs rose significantly, with KPC-2 mutants reaching >32 mg/L. Phenotypic analysis revealed a common resistance profile across all tested mutants, with resistance to ceftazidime, ceftazidime-avibactam, cefixime, and piperacillin, but restored susceptibility to carbapenems and most other {beta}-lactams. Sequencing identified key mutations (D179Y- D209V in KPC-2, L169P in KPC-3), while chromosomal changes, particularly cirA and ybiX disruptions, played a crucial role in resistance evolution. DiscussionOur results show that the enriched mutations in KPC genes are not sufficient to confer high cefiderocol MICs, suggesting that, in the studied variants, no simple mutational pathway allows the KPC enzyme to efficiently hydrolyze cefiderocol. These findings underscore the interplay between enzymatic and iron transport mutations in cefiderocol resistance, highlighting the importance of surveillance to anticipate emerging resistance in KPC-producing pathogens.

microbiology↗

bioRxiv2022

Pre-clinical in vitro and in vivo characterization of a maternal vaccination before conception to protect against severe neonatal infections caused by Escherichia coli K1

Preterm birth remains the leading cause of neonatal morbidity and mortality today. Genetic, immunological, and infectious substrates are suspected. Preterm infants are at higher risk of severe neonatal infections and the main cause of bacterial infection in this population is Escherichia coli K1. Unfortunately, women with history of preterm birth have a high risk of recurrence. Therefore, these women constitute a target population for a vaccine, to date non-existent, against E. coli K1 to prevent these infections. In this study, we characterize the immunological and microbiological properties in adult female mice of a live attenuated vaccine candidate and the protection it conferred to newborn mice against severe infection caused by E. coli K1. We show that our E. coli K1 {Delta}aroA vaccine induces a strong immunity driven by polyclonal bactericidal antibodies. In our model of meningitis, pups born from mothers immunized before conception were strongly protected against different strains of E. coli K1 both in early-onset and late-onset diseases. Given the very high rate of mortality and neurological sequalae in neonatal meningitis caused by E. coli K1, this pre-clinical study provides a proof-of-concept for the development of a vaccine strategy against E. coli K1 severe infection in women at risk of preterm birth.

microbiology↗

bioRxiv2022

A high-throughput sequencing approach identifies immunotherapeutic targets for bacterial meningitis in neonates

BackgroundWorldwide, Escherichia coli is the leading cause of neonatal Gram-negative bacterial meningitis, but full understanding of the pathogenesis of this disease is not yet achieved. Moreover, to date, no vaccine is available against bacterial neonatal meningitis. MethodsHere, we used Transposon Sequencing of saturated banks of mutants (TnSeq) to evaluate E. coli K1 genetic fitness in murine neonatal meningitis. We identified E. coli K1 genes encoding for factors important for systemic dissemination and brain infection, and focused on products with a likely outer-membrane or extra-cellular localization, as these are potential vaccine candidates. We used in vitro and in vivo models to study the efficacy of active and passive immunization. ResultsWe selected for further study the conserved surface polysaccharide Poly-{beta}-(1-6)-N-Acetyl Glucosamine (PNAG), as a strong candidate for vaccine development. We found that PNAG was a virulence factor in our animal model. We showed that both passive and active immunization successfully prevented and/or treated meningitis caused by E. coli K1 in neonatal mice. We found an excellent opsonophagocytic killing activity of the antibodies to PNAG and in vitro these antibodies were also able to decrease binding, invasion and crossing of E. coli K1 through two blood brain barrier cell lines. Finally, to reinforce the potential of PNAG as a vaccine candidate in bacterial neonatal meningitis, we demonstrated that Group B Streptococcus, the main cause of neonatal meningitis in developed countries, also produced PNAG and that antibodies to PNAG could protect in vitro and in vivo against this major neonatal pathogen. InterpretationAltogether, these results indicate the utility of a high-throughput DNA sequencing method to identify potential immunotherapy targets for a pathogen, including in this study a potential broad-spectrum target for prevention of neonatal bacterial infections. FundingsANR Seq-N-Vaq, Charles Hood Foundation, Hearst Foundation. Groupe Pasteur Mutualite

microbiology↗