Leptospirosis is a globally distributed zoonosis that affects both humans and animals, with Leptospira interrogans being the main causative agent. In horses, the disease is associated with considerable economic losses. The Microscopic Agglutination Test (MAT) is the reference test for diagnosis but has limitations, emphasizing the need for effective diagnostic alternatives. In this study, was evaluated the use of a recombinant chimera, composed of ErpY-like and LemA proteins, as an antigen for ELISA-based detection of equine leptospirosis. The chimera was successfully expressed, purified and tested on 915 horse serum samples previously analyzed by MAT. The ELISA correctly identified all positive samples, with no false negative observed. The ROC curve analysis, considering different hypothetical prevalence values, reached up to 0.92. The assay demonstrated sensitivity ranging from 98.8% to 100%, specificity from 77.6% to 84%, positive predictive value between 68.6% and 77.2%, and negative predictive value between 92% and 100%. The Kappa coefficient was 0.7432, indicating good agreement with MAT. When samples were categorized by titers, those with a 1:400 dilution achieved the highest accuracy (99%), while those with a 1:100 dilution showed slightly lower accuracy (94.8%), demonstrating that higher antibody titers resulted in a more effective assay. The major serovars that cause infection in horses, such as Bratislava, Icterohaemorrhagiae, Sejroe, Pomona, and Copenhageni, react with rErpY-lemA. These results suggest that the ErpY-LemA chimera is a promising screening tool for equine leptospirosis, offering a valuable alternative for the rapid and accurate detection of different serovars and titers.

The increasing resistance of Klebsiella pneumoniae to antibiotics, particularly carbapenems, underscores the urgent need for alternative antimicrobial strategies. This study aimed to evaluate the antimicrobial and antibiofilm activity of biogenic silver nanoparticles (Bio-AgNPs), synthesized using Trichilia catigua extract and to investigate their mechanism of action on bacterial cells. The antimicrobial efficacy of Bio-AgNPs was assessed by determining the minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), and through susceptibility assays, time-kill analysis, flow cytometry, and electron microscopy. Bio-AgNPs exhibited strong antibacterial activity against all tested K. pneumoniae strains, with MICs ranging from 0.49 to 15.62 µg/mL. Eradication of biofilms required concentrations 16 to 64 times higher than those effective against planktonic cells, highlighting the protective nature of biofilm matrix. Time-kill assays showed a concentration-dependent bactericidal effect, with 4xMIC rapidly eliminating viable cells. Flow cytometry indicated membrane destabilization, increased fluidity at lower concentrations, and extensive structural damage at higher concentrations. Although lipid peroxidation and reactive oxygen species (ROS) were detected, they were not statistically significant, suggesting that membrane disruption is the primary bactericidal mechanism. Electron microscopy corroborated the structural disintegration of both bacterial cells and biofilms after treatment. Bio-AgNPs demonstrated potent antimicrobial and antibiofilm effects against multidrug-resistant K. pneumoniae, with membrane damage as the main mechanism of action. These results support the potential application of Bio-AgNPs as a therapeutic alternative for biofilm-associated infections. This study highlights the antibacterial and anti-biofilm potential of biogenic silver nanoparticles (Bio-AgNPs) as an effective tool against multidrug-resistant Klebsiella pneumoniae, with efficancy against both free-living cells and structured biofilms.

This study aimed to develop a multi-epitope recombinant chimera (rChimera) based on two outer membrane proteins of Acinetobacter baumannii, targeting passive or active immunization strategies against biofilm-forming strains of this multidrug-resistant bacterium. Using bioinformatics and reverse vaccinology, we identified CAM87009.1 and FilF as two conserved proteins involved in biofilm formation and host cell adherence. An in silico analysis was performed to design the rChimera, selecting 36 promising B- and T-cell epitopes, including those recognized by MHC class I and II. These epitopes were linked using a glycine linker (GGGG) and a rigid linker (EAAKEAAAKA). The chimera was chemically synthesized, successfully expressed in Escherichia coli BL21 Star, and recognized by antibodies from naturally infected patients. Polyclonal antibodies (pAbs) produced in a murine model elicited a significant IgG response from the 14th day after the first immunization, with IgG1 and IgG2 (a and b) being the predominant isotypes generated. Anti-rChimera pAbs effectively inhibited biofilm formation in multidrug-resistant isolates and the ATCC® 19,606 strain of A. baumannii. The recombinant chimera shows promise for passive or active immunization against biofilm-forming strains of A. baumannii.

Leptospirosis is an emerging zoonotic disease that causes over a million human cases and numerous fatalities annually, imposing substantial public health, economic, and veterinary burdens worldwide. Despite its impact, control strategies remain limited, as commercial bacterin vaccines offer only short-term, serovar-specific protection. The extensive genetic and antigenic diversity of Leptospira species presents a major challenge to the development of broadly protective vaccines. In response, several alternative strategies have been explored, including DNA vaccines, viral-vectored platforms and multi-epitope recombinant chimeric proteins. Among these, chimeric constructs have emerged as promising candidates due to their ability to combine conserved immunogenic regions from multiple antigens, potentially eliciting broader and more effective immune responses. Advances in immunoinformatics, reverse vaccinology and structural modeling have enabled the rational design of these constructs, allowing for the identification of B- and T-cell epitopes with high antigenic potential and wide population coverage. This mini-review provides an overview of recent progress in the development of innovative vaccine strategies against leptospirosis, with particular focus on recombinant chimeric proteins. We discuss the advantages and limitations, highlighting their potential to enhance cross-protection and contribute to more effective control of leptospirosis.

Objective: to identify the antimicrobial sensitivity profile of Klebsiella pneumoniae isolates causing infections in a university hospital in southern Brazil. Method: this descriptive, observational study analyzed 50 isolates collected from patients hospitalized between August 2022 and May 2023 in a university hospital in southern Brazil. Data collected included date, sex, age, sample type, antibiogram results, and location of hospitalization, obtained from the BD Phoenix™ system. Results: all isolates (100%) were sensitive to amikacin, highlighting the potential of aminoglycosides as important therapeutic options. In contrast, none of the isolates showed sensitivity to ampicillin. Notably, 60% of the isolates tested for ceftazidime/avibactam demonstrated sensitivity. The most prevalent resistance markers were carbapenemase production (36%) and extended-spectrum beta-lactamase (32%). Conclusion: the study revealed a high level of antibiotic resistance in K. pneumoniae isolates.

Adjuvants are crucial for maintaining specific, protective, and long-lasting immunity. Here, we aimed to evaluate the antigenic and immunogenic activity of a recombinant form of the S1 domain of the Spike protein, associated with biogenic silver nanoparticles (bio-AgNP) and Alhydrogel® as an alternative and conventional adjuvant, respectively, for a SARS-CoV-2 subunit vaccine. We produced and evaluated the antigenicity of the recombinant S1 (rS1) protein by testing its recognition by antibodies present in SARS-CoV-2 positive human serum. The immunogenicity of the rS1 protein was assessed in vivo by its ability to induce antibody production in mice. Furthermore, we sought to establish the types of humoral and cellular immune responses generated through intramuscular immunization in BALB/c mice with the rS1 + bio-AgNP vaccine. The recombinant S1 (rS1) protein was successfully cloned, expressed in Escherichia coli, and confirmed to have strong antigenic potential, being recognized by human antibodies up to a 1:51,200 serum dilution. In vivo assays showed that vaccines using rS1 with either bio-AgNP or Alhydrogel® as adjuvants induced high and consistent antibody titers (1:51,200) and a range of antibody isotypes in mice. Cellular immune response analysis revealed significant IL-10 expression with rS1 + bio-AgNP and both IL-10 and TNFα expression with rS1 + Alhydrogel®. These results support rS1 + bio-AgNP as a promising vaccine candidate for future development, highlighting its potential not only as a viable alternative to traditional adjuvants but also as an innovative contribution to advancing more effective and accessible immunological strategies.

ABSTRACT Combating multidrug-resistant Acinetobacter baumannii is considered a priority by the World Health Organization. Virulence mechanisms, such as biofilm formation, multidrug resistance, and high adherence to both biotic and abiotic surfaces, underscore the urgency of exploring approaches to control this pathogen. The search for new antibiotic compounds and alternative strategies like immunotherapies and vaccination offers potential solutions to address this pressing health concern. In this context, adhesins play a crucial role in the pathogenicity and virulence of A. baumannii , making them potential targets for therapeutic interventions. To address this, we conducted a systematic review of A. baumannii adhesin research from the last decade (2013–2023). We reviewed 24 papers: 6 utilizing reverse vaccinology bioinformatic tools to predict adhesin targets for vaccine construction, 17 employing DNA recombinant techniques for in vivo active and passive immunization or in vitro antibody-mediated therapy assays, and 1 paper exploring the impact of pyrogallol therapy on A. baumannii virulence mechanisms. Our review identified over 20 potential targets with significant findings. We screened and summarized these targets to aid in further exploration of therapies and prevention.

AIMS:This study aimed to design and evaluate novel antimicrobial peptides (AMPs) with antibacterial and antibiofilm activity against Pseudomonas aeruginosa. Computational analyses included interactions with quorum sensing (QS) receptors as potential targets involved in bacterial virulence regulation. METHODS AND RESULTS:AMP sequences were generated using TACaPe, a deep learning model based on transformers, to predict peptides with antibacterial activity. The selected AMPs were assessed in silico for their ability to bind QS receptors (LasR, RhlR, and PqsR) using molecular docking analysis. The five AMPs with the highest binding affinities were chemically synthesized and tested in vitro against P. aeruginosa ATCC® 27853. Two peptides exhibited significant antibacterial effects and dose-dependent inhibition of biofilm formation. Additionally, both peptides showed synergistic activity with meropenem, lowering its minimum inhibitory concentration (MIC). Hemolytic and cytotoxic assays indicated their potential for therapeutic application. CONCLUSIONS:Computationally designed AMPs exhibited antibacterial and antibiofilm activity against P. aeruginosa. Their synergistic effects with meropenem further enhance their therapeutic potential.

Bartonella henselae is a fastidious, facultative intracellular, Gram-negative bacterium that causes Cat Scratch Disease (CSD), a zoonosis in which domestic cats are the primary reservoir and humans as incidental hosts. While CSD is often self-limiting, it can lead to severe systemic complications, particularly in immunocompromised individuals. Diagnosing Ba. henselae infection remains challenging, as conventional methods - including culture, Enzyme -Linked Immunosorbent Assay (ELISA), Indirect Immunofluorescence Assay (IFA) and Polymerase Chain Reaction (PCR) - suffer from low sensitivity, cross-reactivity and lack of standardization. Serological assays are widely used but frequently exhibit cross-reactivity with antigenically related pathogens such as Chlamydia pneumoniae and Coxiella burnetii, limiting specificity. To overcome these issues, the identification of specific antigenic determinants has become a key focus. Recombinant protein-based assays have emerged as promising tools, offering improved specificity, reduced cross-reactivity and greater reproducibility compared to traditional whole-cell antigen approaches. This review critically assesses current diagnostic techniques for B. henselae, highlights their limitations and explores innovative strategies centered on the use of recombinant antigens for enhanced serological diagnosis.

Leptospirosis remains a significant public health concern worldwide, particularly in tropical regions, where its diagnosis is often challenging due to nonspecific symptoms and limitations of current diagnostic methods. In this study, we evaluated the diagnostic potential of the recombinant chimera ErpY-LemA constructed from two Leptospira proteins with known immunogenic properties. The chimera was successfully expressed in Escherichia coli and demonstrated strong antigenicity, effectively recognizing sera from hamsters infected with diverse Leptospira serovars, indicating its non-serovar-specific nature (P < 0.001). ELISA assays were conducted using 80 human sera previously characterized by MAT. In the acute phase, IgM detection achieved 95 % of sensitivity and specificity (cut-off = 0.15, AUC = 0.990; P < 0.001). In the convalescent phase, IgG detection showed 80 % sensitivity and 100 % specificity (cut-off = 0.16, AUC = 0.968; P < 0.001). When the unknown disease phase were assessed, both IgG and IgM ELISAs maintained high diagnostic performance, with sensitivities and specificities ≥95 % and AUC values above 0.98. These findings highlight the ErpY-LemA chimera as a promising antigen for the development of a rapid, cost-effective serological diagnostic test for human leptospirosis, with high sensitivity and specificity regardless of disease stage or infecting serovar.

Acinetobacter baumannii is recognized as a critical priority for drug development due to the growing threat posed by antibiotic-resistant strains to public health. In response, research into non-antibiotic therapies, including passive immunization, has emerged as a promising alternative. This study investigates the immune responses induced by a fimbrial adhesin (FilF) from A. baumannii, used here as an immunogen. Recombinant FilF (rFilF) was formulated with Alhydrogel® adjuvant and administered intramuscularly in a three-dose schedule on days 0, 14 and 28 (n = 4). A control group (n = 4) received adjuvant diluted in 1 x PBS. Serum samples were collected weekly, and the spleens were harvested 14 days after the final immunization. Anti-rFilF IgG levels were evaluated by ELISA using pooled serum samples corresponding to each time point. To evaluate the functional activity of the immune response, anti-rFilF serum was incubated with A. baumannii ATCC® 19606™ and a carbapenem-resistant clinical strain. The opsonization ability of anti-rFilF antibodies to enhance macrophage phagocytosis was assessed using RAW264.7 cell cultures. Treatment with anti-rFilF serum significantly reduced bacterial viability in both strains, associated with increased macrophage phagocytic activity. By flow cytometry analysis we observe increased bacterial reactive oxygen species (ROS) levels and alterations in bacterial membrane integrity following treatment with anti-rFilF serum, suggesting potential mechanisms of bacterial clearance. Additionally, cytokine profiling of splenocyte cultures from immunized mice indicated a balanced cytokine response, with upregulation of IL-1β, IL-4, and IL-10, alongside the downregulation of IFN-γ. These findings indicate that rFilF immunization induces functional antibodies with therapeutic potential against A. baumannii infection.

Leptospirosis is a zoonosis with widespread worldwide. Transmission occurs through direct or indirect contact with contaminated water, urine, milk, and soil. Symptoms are variable but can lead to significant losses for producers, making it a major economic concern in livestock farming. The Microscopic Agglutination Test (MAT) is the gold standard for leptospirosis diagnosis but presents limitations, such as the need for live Leptospira cultures, specialized infrastructure, and trained personnel. It is time-consuming, labor-intensive, and poses health risks due to live pathogen handling. Simpler, safer alternatives, such as the Enzyme-Linked Immunosorbent Assay (ELISA) using recombinant antigens, are needed. In this study, we developed an ELISA using a recombinant chimera, rErpY-LemA, which combines the ErpY-like and LemA Leptospira proteins as an antigen. The chimera was tested with sera from various Leptospira serovars and showed significant reactions (P < 0.001) with antibodies against 12 strains. The chimera showed promising diagnostic performance in cattle (n = 335) and sheep (n = 259) sera, confirmed by MAT. The AUC was 0.903 for bovine (sensitivity: 98.3-100 %, specificity: 60.9-78.2 %) and 0.917 for ovine (sensitivity: 97.7-100 %, specificity: 57.1-76.5 %). The test showed strong agreement with MAT, with a PPV of 81.3 %-90.2 % for cattle and 77.4 %-88.4 % for sheep. These results confirm that rErpY-LemA is an effective antigen for diagnosing leptospirosis in cattle and sheep, being able to detect different serovars. Thus, ELISA using the rErpY-LemA chimera is a promising tool for leptospirosis screening in livestock, offering a safer and more practical alternative to MAT.

Acinetobacter baumannii is a bacteria associated with nosocomial infections and outbreaks, difficult to control due to its antibiotic resistance, ability to survive in adverse conditions, and biofilm formation adhering to biotic and abiotic surfaces. Therefore, this study aimed to evaluate the antibiofilm activity of biogenic silver nanoparticle (Bio-AgNP) and polymyxin B alone and combined in biofilms formed by isolates of carbapenem-resistant A. baumannii (CR-Ab). In the biofilm formation inhibition assay, CR-Ab strains were exposed to different concentrations of the treatments before inducing biofilm formation, to determine the ability to inhibit/prevent bacterial biofilm formation. While in the biofilm rupture assay, the bacterial biofilm formation step was previously carried out and the adhered cells were exposed to different concentrations of the treatments to evaluate their ability to destroy the bacterial biofilm formed. All CR-Ab isolates and ATCC® 19606™ used in this study are strong biofilm formers. The antibiofilm activity of Bio-AgNP and polymyxin B against CR-Ab and ATCC® 19606™ demonstrated inhibitory and biofilm-disrupting activity. When used in combination, Bio-AgNP and polymyxin B inhibited 4.9–100

The current public health worry revolves around infections stemming from the consumption of meat contaminated with Salmonella spp., which has been linked to the growing issue of antimicrobial resistance. We investigated the presence of non-typhoidal Salmonella (NTS) in the retail of spicy chicken meat and its antimicrobial susceptibility profile. Forty establishments (supermarkets and butcheries) in Mid-West Brazil were visited in February and July 2017, totaling 80 samples. Salmonella isolation, molecular serotyping and antimicrobial analyses were performed. Of the total establishments, 18 sold meat NTS-positive, 6 of which were contaminated in the two visits, resulting in 24 contaminated samples (30%). Of these, the prevalent serovars were Heidelberg (58%–14/24), Minnesota (21%–05/24), Muenchen (17%–04/24) and Mbandaka (4%–01/24), but none was positive for Typhimurium and Enteritidis. Still, 55.6% (10/18) of the establishments did not have a veterinary inspection seal, and 50% (09/18) sold products beyond their expiration date. Worse still, 87.5% (21/24) of NTS isolates were resistant to at least one antimicrobial agent, being 66.7% (16/24) multidrug-resistant. The bla gene was detected in 41.6% (10/24), confirming resistance by β-lactamase enzymes. These findings highlighted the great risk of foodborne illness due to the possibility of contaminated seasoned chicken meat and transmission of bla resistant genes through the food chain.

Due to its antimicrobial resistance characteristics, the World Health Organization (WHO) classifies A. baumannii as one of the critical priority pathogens for the development of new therapeutic strategies. Vaccination has been approached as an interesting strategy to overcome the lack of effective antimicrobials and the long time required to develop and approve new drugs. In this study, we aimed to evaluate as a vaccine the hypothetical adhesin protein CAM87009.1 in its recombinant format (rCAM87009.1) associated with aluminum hydroxide (Alhydrogel®) or biogenic silver nanoparticles (bio-AgNP) as adjuvant components against lethal infection by A. baumannii MDR strain. Both vaccine formulations were administered in three doses intramuscularly in BALB/c murine models and the vaccinated animals were tested in a challenge assay with A. baumannii MDR strain (DL100). rCAM87009.1 protein associated with both adjuvants was able to protect 100 % of animals challenged with the lethal strain during the challenge period. After the euthanasia of the animals, no A. baumannii colonies were detected in the lungs of animals vaccinated with the rCAM87009.1 protein in both formulations. Since the first immunization, high IgG antibody titers were observed (1:819,200), with results being statistically similar in both vaccine formulations evaluated. rCAM87009.1 associated with both adjuvants was capable of inducing at least one class of isotypes associated with the processes of neutralization (IgG2b and IgA for bio-AgNP and Alhydrogel®, respectively), opsonization (IgG1 in both vaccines) and complement activation (IgM and IgG3 for bio-AgNP and Alhydrogel®, respectively). Furthermore, reduced tissue damage was observed in animals vaccinated with rCAM87009.1 + bio-AgNP when compared to animals vaccinated with Alhydrogel®. Our results indicate that the rCAM87009.1 protein associated with both bio-AgNP and Alhydrogel® are combinations capable of promoting immunity against infections caused by A. baumannii MDR. Additionally, we demonstrate the potential of silver nanoparticles as alternative adjuvant molecules to the use of aluminum salts.

Antibiotic resistance and the potential persistence of Klebsiella pneumoniae strains in hospital environments is an important challenge for human medicine. This research aims to detect resistance to antibiotics, biofilm formation, and the genetic pattern among clinical isolates associated with nosocomial infection obtained from a university hospital in the city of Pelotas, RS, Brazil. Twenty-eight isolates were identified at the species level by polymerase chain reaction (PCR) and were characterized regarding the profile of biofilm formation and antibiotic resistance. The genetic relationship was determined through pulsed-field gel electrophoresis (PFGE). The antibiotic resistance profile was made following the standards established by CLSI. All clinical isolates included in this study were confirmed as belonging to the species K. pneumoniae, 96.42

Aims Antibiotic management of infections caused by Acinetobacter baumannii often fails due to antibiotic resistance (especially to carbapenems) and biofilm-forming strains. Thus, the objective here was to evaluate in vitro the antibacterial and antibiofilm activity of biogenic silver nanoparticle (Bio-AgNP) combined with meropenem, against multidrug-resistant isolates of A. baumannii.Methods and results In this study, A. baumannii ATCC (R) 19606 (TM) and four carbapenem-resistant A. baumannii (Ab) strains were used. The antibacterial activity of Bio-AgNP and meropenem was evaluated through broth microdilution. The effect of the Bio-AgNP association with meropenem was determined by the checkboard method. Also, the time-kill assay and the integrity of the bacterial cell membrane were evaluated. Furthermore, the antibiofilm activity of Bio-AgNP and meropenem alone and in combination was determined. Bio-AgNP has antibacterial activity with minimum inhibitory concentration (MIC) and minimum bactericidal concentration ranging from 0.46 to 1.87 mu g ml-1. The combination of Bio-AgNP and meropenem showed a synergistic and additive effect against Ab strains, and Bio-AgNP was able to reduce the MIC of meropenem from 4- to 8-fold. Considering the time-kill of the cell, meropenem and Bio-AgNP when used in combination reduced bacterial load to undetectable levels within 10 min to 24 h after treatment. Protein leakage was observed in all treatments evaluated. When combined, meropenem/Bio-AgNP presents biofilm inhibition for Ab2 isolate and ATCC (R) 19606 (TM), with 21% and 19%, and disrupts the biofilm from 22% to 50%, respectively. The increase in nonviable cells in the biofilm can be observed after treatment with Bio-AgNP and meropenem in carbapenem-resistant A. baumannii strains.Conclusions The combination of Bio-AgNP with meropenem can be a therapeutic option in the treatment of infections caused by carbapenem-resistant A. baumannii.

Aims Enterococcus faecalis (E. faecalis) is a leading cause of nosocomial infection and presents a wide spectrum of antibiotic resistance, being vancomycin-resistant Enterococcus (VRE) one of the most relevant. Synthetic antimicrobial peptides (SAMPs) are currently a promising option to overcome antimicrobial resistance. Thus, the purpose of this study was to assess the effect of eight SAMPs against vancomycin-resistant E. faecalis, as well as to investigate their mechanism of action and synergy with conventional antibiotics.Methods and results Here, eight SAMPs, Mo-CBP3-PepI, Mo-CBP3-PepII, Mo-CBP3-PepIII, RcAlb-PepI, RcAlb-PepII, RcAlb-PepIII, PepGAT, and PepKAA, were tested for antibacterial activity in vitro against E. faecalis (ATCC (R) 51299) through broth microdilution. A maximum of 48% of E. faecalis growth inhibition was achieved by treatment with SAMPs alone. However, when these peptides were combined with the antibiotic chloramphenicol, assessed by checkerboard method, the inhibition increased to 55%-76% of inhibition, two to three-folds of increase if compared to the effects of the compounds alone. Microscopic analysis showed that E. faecalis cells treated with a combination of SAMPs and chloramphenicol resulted in bacterial membrane damage. The biofilm inhibition maximum was 22% for SAMPs alone, when combined with chloramphenicol, the maximum increased to 33%.Conclusions SAMPs and their combination with chloramphenicol demonstrate antibacterial activity against E. faecalis, possibly by inducing bacterial membrane damage.

Aims Currently, immunoinformatic approaches have shown promise in rapidly and cost-effectively identifying new antigens from the Leptospira proteome. Chimeric multiepitope proteins offer a strategy with significant potential for implementation in diagnosis and vaccines development. Methods and results In this study, we detail the immunoinformatic analyses and design of a new recombinant chimeric protein constructed with epitopes identified from the sequences of ErpY-like and LemA proteins, previously identified as potential antigens for controlling leptospirosis. We expressed the chimeric protein using Escherichia coli heterologous systems, evaluated its antigenicity using serum from naturally infected patients, and its immunogenicity in mice as an animal model, with Freund as an adjuvant. The resulting recombinant chimeric protein, named rErpY-LemA, was successfully expressed and purified using a prokaryotic system, with an expected mass of 35 kDa. Serologic assays using serum samples from naturally infected patients demonstrated recognition of the chimera protein by antibodies present in sera. Animals immunized with the chimera exhibited a significant IgG antibody response from the 7th day (P < 0.001), persisting until day 49 of experimentation, with a titer of 1:12,800 (P < 0.05). Notably, significant production of IgA, IgM, and IgG subclasses was observed in animals immunized with the chimera. Conclusions These results highlight the promising role of immunoinformatics in rapidly identifying antigens and the potential of chimeric multiepitope proteins in developing effective strategies for leptospirosis control.

Acinetobacter baumannii is an opportunistic bacterium that causes infection in several sites. Carbapenem-resistant A. baumannii strains (CRAb) lead the World Health Organization's list of 12 pathogens considered a priority for developing new antimicrobials. The pathogenicity of A. baumannii is related to the different virulence factors employed in the colonization of biotic and abiotic surfaces, biofilm formation and multidrug resistance. We analyze the outer membrane protein FilF from A. baumannii in silico and produce it in recombinant form (rFilF). rFilF protein was successfully expressed in Escherichia coli BL21 Star in an insoluble form. Immunization with rFilF induced significant anti-rFilF IgG antibody production in mice, detected by indirect enzyme-linked immunosorbent assay, since the first evaluation until 49th. On the last experimentation day, the predominant immunoglobulin found was IgG1 followed by IgG2a, IgG2b, IgM, IgG3, and IgA. We observe that interleukins 4 and 10 show significant production after the 28th day of experimentation in mice immunized with rFilF. Anti-rFilF pAbs were able to inhibit biofilm formation in nine CRAb strains evaluated, and in the standard strain ATCC® 19606. These results demonstrate the anti-biofilm activity of anti-rFilF antibodies, promising in the development of a non-antibiotic approach based on the control of CRAb strains.