Biology subjects

Le Van, A.

Publications and source records attributed to Le Van, A..

3 recordsLinked to original sources

bioRxiv2025

The role of the L421P mutation in Penicillin-Binding Protein 1 (PBP1) in the evolution of chromosomally mediated penicillin resistance in Neisseria gonorrhoeae

ponAL421P encodes a mutated variant of penicillin-binding protein 1 (PBP1) and is a key resistance determinant that increases the penicillin MIC (MICPEN) above the clinical breakpoint in Neisseria gonorrhoeae. Despite the removal of penicillin from treatment guidelines for gonococcal infections in the 1980s, ponAL421P is present in nearly 50% of current N. gonorrhoeae isolates in the PubMLST database. Bioinformatic analysis indicates that ponAL421P is exclusive to N. gonorrhoeae isolates, whereas Leu-421 is 100% conserved in other Neisseria species. To understand the involvement of ponAL421P in antibiotic resistance, we introduced ponA variants encoding 16 different amino acids at position-421 into FA6140, a penicillin-resistant gonococcal isolate that naturally harbors ponAL421P. Proline-421 was the only mutation that increased the MICPEN to the same level as FA6140. We also assessed the fitness of strains with the 16 mutant ponA alleles over multiple serial passages, both with and without sub-MIC levels of penicillin. There was no fitness defect attributed to ponAL421P under these experimental conditions; instead, our analyses suggest that the widespread occurrence of ponAL421P is driven by its capacity to increase the MICpen above the clinical breakpoint. In FA6140 transformed with the mosaic penA allele from strain H041, a ceftriaxone-resistant isolate, ponAL421P increased the MIC of ceftriaxone, suggesting that ceftriaxone targets PBP1 in this strain. We conclude that the ponAL421P allele emerged in gonococcal isolates, increasing the MICPEN above the clinical breakpoint, and has remained in the population even after the removal of penicillin from treatment guidelines. ImportanceThe emergence of antibiotic-resistant Neisseria gonorrhoeae threatens effective treatment of gonorrhea, one of the most common sexually transmitted infections worldwide. Understanding the genetic changes that drive and maintain resistance is crucial for anticipating future resistance trends. Here, we investigated the impact of a key resistance mutation in PBP1 (encoded by ponAL421P). Although penicillin has not been used to treat gonorrhea for decades, this mutation remains widespread even in recent N. gonorrhoeae isolates. ponAL421P confers clinically relevant penicillin resistance without imposing an in vitro fitness cost. ponAL421P also increases resistance to ceftriaxone in strains with penA alleles that are associated with ceftriaxone resistance. This work highlights the role of the ponAL421P allele in shaping the current antibiotic resistance landscape and supports the need for ongoing surveillance and evolutionary studies of such mutations in the gonococcal population.

microbiology↗

bioRxiv2025

Gentamicin induction of the gonococcal hicAB toxin-antitoxin encoding system and 2 impact on gene expression influencing biofilm formation and in vivo fitness in a strain specific manner

The continued emergence of Neisseria gonorrhoeae (Ng) isolates resistant to first-line antibiotics has focused efforts on understanding how alternative therapies such as expanded use of gentamicin (Gen) might counteract this global public health problem. Focusing on Gen as a viable alternative antibiotic for treatment of gonorrheal infections, we used RNA-Seq to determine if sub-lethal levels of Gen might impact gonococci on a transcriptional level. We found that sub-lethal Gen levels altered expression of 23 genes in Ng strain FA19. Many of the differentially regulated genes were associated with known stress responses elaborated by Ng under different harmful conditions. We found that the transcripts of the hicAB operon, which encodes a putative HicA-HicB toxin-antitoxin system that is encoded by tandem genes with the prophage Ngo {varphi}3, were increased in response to Gen. While loss of hicAB did not impact gonococcal susceptibility to a variety of antimicrobial agents or harmful environmental conditions it did reduce biofilm formation in Ng strains F62, FA1090, WHO X and CDC200 but not that of strain FA19. Further, in strain F62, but not FA19, loss of hicAB reduced the in vivo fitness of Ng during experimental lower genital tract infection of female mice. Further, we found that expression of hicAB can influence levels of the norB transcript, which encodes the nitrate reductase shown previously to be upregulated in gonococcal biofilms. We propose that sub-lethal Gen has the capacity to influence gonococcal pathogenesis through the action of the HicAB toxin-antitoxin system. ImportanceDuring antibiotic treatment bacteria can be exposed to sub-lethal levels that could serve as a stress signal resulting in changes in gene expression. The continued emergence of multi-drug resistant strains of Ng has rekindled interest in expanded use of gentamicin (Gen) for treatment of gonorrheal infections. We report that sub-lethal levels of Gen can influence levels of Ng transcripts including that of the gonococcal hicAB-encoded toxin-antitoxin (TA) locus, which is embedded within an integrated prophage, While loss of this TA locus did not impact Ng susceptibility to Gen it reduced the biofilm forming ability of 4/5 Ng strains. Further, in an examined strain in this group we found that Ng fitness during experimental infection was negatively impacted. We propose that that levels of the hicA-hicB transcripts can be increased by sub-lethal levels of an antibiotic used in treatment of gonorrhea and that this could influence pathogenicity.

microbiology↗

bioRxiv2020

A novel gonorrhea vaccine composed of MetQ lipoprotein formulated with CpG shortens experimental murine infection

Bacterial surface lipoproteins are emerging as attractive vaccine candidates due to their biological importance and the feasibility of their large-scale production for vaccine manufacturing. The global prevalence of gonorrhea, resistance to antibiotics, and serious consequences to reproductive and neonatal health necessitate development of effective vaccines. Reverse vaccinology identified the surface-displayed L-methionine binding lipoprotein MetQ (NGO2139) and its homolog GNA1946 (NMB1946) as gonococcal and meningococcal vaccine candidates, respectively. Here, we assessed the suitability of MetQ for inclusion in a gonorrhea vaccine by examining MetQ conservation, its function in Neisseria gonorrhoeae (Ng) pathogenesis, and its ability to induce protective immune responses using a female murine model of lower genital tract infection. In-depth bioinformatics, phylogenetics and mapping the most prevalent Ng polymorphic amino acids to the GNA1946 crystal structure revealed remarkable MetQ conservation: ~97% Ng isolates worldwide possess a single MetQ variant. Mice immunized with rMetQ-CpG (n=40), a vaccine containing a tag-free version of MetQ formulated with CpG, exhibited robust, antigen-specific antibody responses in serum and at the vaginal mucosae including secretory IgA. Consistent with the activity of CpG as a Th1-stimulating adjuvant, the serum IgG1/IgG2a ratio of 0.38 indicated a Th1 bias. Combined data from two independent challenge experiments demonstrated that rMetQ-CpG immunized mice cleared infection faster than control animals (vehicle, p<0.0001; CpG, p=0.002) and had lower Ng burden (vehicle, p=0.03; CpG, p<0.0001). We conclude rMetQ-CpG induces a protective immune response that accelerates bacterial clearance from the murine lower genital tract and represents an attractive component of a gonorrhea subunit vaccine.

microbiology↗