Development and Standardization of a High-Throughput Bordetella pertussis Growth-Inhibition Assay

Synergism with Shikimic Acid Restores β-Lactam Antibiotic Activity against Methicillin-Resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) has evolved into a dangerous pathogen resistant to beta-lactam antibiotics (BLAs) and has become a worrisome superbug. In this study, a strategy in which shikimic acid (SA), which has anti-inflammatory and antibacterial activity, is combined with BLAs to restart BLA activity was proposed for MRSA treatment. The synergistic effects of oxacillin combined with SA against oxacillin resistance in vitro and in vivo were investigated. The excellent synergistic effect of the oxacillin and SA combination was confirmed by performing the checkerboard assay, time-killing assay, live/dead bacterial cell viability assay, and assessing protein leakage. SEM showed that the cells in the control group had a regular, smooth, and intact surface. In contrast, oxacillin and SA or the combination treatment group exhibited different degrees of surface collapse. q-PCR indicated that the combination treatment group significantly inhibited the expression of the mecA gene. In vivo, we showed that the combination treatment increased the survival rate and decreased the bacterial load in mice. These results suggest that the combination of oxacillin with SA is considered an effective treatment option for MRSA, and the combination of SA with oxacillin in the treatment of MRSA is a novel strategy.

A novel approach to design a multiepitope peptide as a vaccine candidate for Bordetella pertussis

Bordetella pertussis is a very contagious pathogen in humans, causing pertussis disease. Pertussis is one of the 10 leading causes of death due to infectious diseases, especially among infants and children. Antibiotic-resistant strains have recently emerged in this bacterium, and despite the high vaccination coverage, the prevalence of this disease has been increasing recently in both developed and developing countries. The objective of this study is to introduce a novel in silico vaccine candidate aimed at countering B. pertussis effectively. Differing from other comparable studies, this research employed a computational screening methodology to assess the genome of 'Bordetella pertussis 18323.' The purpose was to identify an innovative antigen for the development of a vaccine against B. pertussis. Notably, our investigation introduces an innovative antigen distinguished by its elevated immunogenicity score. Importantly, this antigen lacks toxicity and allergenicity, making it recognizable to the immune system and thus capable of inducing a robust immune response. In the subsequent phase, our antigen was utilized to identify potential epitopes conducive to the construction of a B. pertussis vaccine. These epitopes, alongside linkers, his-tag and adjuvants, were amalgamated to form the vaccine candidate. Subsequently, a comprehensive evaluation of the vaccine was conducted, encompassing various computational tests such as secondary and tertiary structure analysis, physicochemical examination, and structural analysis involving docking and molecular dynamics simulations. Importantly, our vaccine successfully passed all in silico tests.Communicated by Ramaswamy H. Sarma.

A Novel Method to Determine the Longitudinal Antibacterial Activity of Drug-Eluting Materials

Ultrahigh molecular weight polyethylene (UHMWPE) is widely used in total joint arthroplasties as a load-bearing surface. Periprosthetic joint infections, the majority of which occur shortly after joint replacement, constitute almost 25% of total knee revision surgeries, and the complete eradication of bacterial infection poses a major challenge. A promising way to tackle this problem is to ensure the local sustained delivery of antibiotic concentrations sufficient to inhibit the bacteria to support routine systemic antibiotic prophylaxis. There is increased research into the development of efficient local drug delivery devices. Although established antibacterial testing methods for drugs can be used to test the antibacterial efficacy of drug-eluting materials, they are lacking in terms of providing real-time and longitudinal antibacterial efficacy data that can be correlated to the elution profiles of antibiotics from these devices. Here, we report a direct and versatile methodology to determine the antibacterial efficacy of antibiotic-eluting UHMWPE implants. This methodology can be used as a platform to avoid bacterial culture at each time point of a lengthy experiment and can also be adapted to other local drug delivery devices.

Antibodies binding diverse pertactin epitopes protect mice from B. pertussis infection

Infection by the bacterium Bordetella pertussis continues to cause considerable morbidity and mortality worldwide. Many current acellular pertussis vaccines include the antigen pertactin, which has presumptive adhesive and immunomodulatory activities, but is rapidly lost from clinical isolates after the introduction of these vaccines. To better understand the contributions of pertactin antibodies to protection and pertactin's role in pathogenesis, we isolated and characterized recombinant antibodies binding four distinct epitopes on pertactin. We demonstrate that four of these antibodies bind epitopes that are conserved across all three classical Bordetella strains, and competition assays further showed that antibodies binding these epitopes are also elicited by B. pertussis infection of baboons. Surprisingly, we found that representative antibodies binding each epitope protected mice against experimental B. pertussis infection. A cocktail of antibodies from each epitope group protected mice against a subsequent lethal dose of B. pertussis and greatly reduced lung colonization levels after sublethal challenge. Each antibody reduced B. pertussis lung colonization levels up to 100-fold when administered individually, which was significantly reduced when antibody effector functions were impaired, with no antibody mediating antibody-dependent complement-induced lysis. These data suggest that antibodies binding multiple pertactin epitopes protect primarily by the same bactericidal mechanism, which overshadows contributions from blockade of other pertactin functions. These antibodies expand the available tools to further dissect pertactin's role in infection and understand the impact of antipertactin antibodies on bacterial fitness.

Acellular Pertussis Vaccines Induce Anti-pertactin Bactericidal Antibodies Which Drives the Emergence of Pertactin-Negative Strains

Despite high vaccination coverage, Bordetella pertussis the causative agent of whooping cough is still a health concern worldwide. A resurgence of pertussis cases has been reported, particularly in countries using acellular vaccines with waning immunity and pathogen adaptation thought to be responsible. A better understanding of protective immune responses is needed for the development of improved vaccines. In our study, B. pertussis strain B1917 variants presenting a single gene deletion were generated to analyze the role of vaccine components or candidate vaccine antigens as targets for bactericidal antibodies generated after acellular vaccination or natural infection. Our results show that acellular vaccination generates bactericidal antibodies that are only directed against pertactin. Serum bactericidal assay performed with convalescent samples show that disease induces bactericidal antibodies against Prn but against other antigen(s) as well. Four candidate vaccine antigens (CyaA, Vag8, BrkA, and TcfA) have been studied but were not targets for complement-mediated bactericidal antibodies after natural infection. We confirm that Vag8 and BrkA are involved in complement resistance and would be targeted by blocking antibodies. Our study suggests that the emergence and the widespread circulation of Prn-deficient strains is driven by acellular vaccination and the generation of bactericidal antibodies targeting Prn.