Microbial pathogenesis最新文献

In this work, the antibiotic resistance, biofilm formation capability, and clonal relatedness of 50 A. baumannii isolates collected from three hospitals in Ardabil city, Iran, were evaluated. Antibiotic sensitivity and biofilm formation of isolates were determined by disk diffusion and microtiter-plate methods, respectively. Molecular typing of isolates was also performed using repetitive sequence-based PCR (REP-PCR). The majority of isolates were resistant to cephems, aminoglycosides, and carbapenems, with 80 % classified as multi-drug resistant (MDR). While, only isolates collected from blood and tracheal were resistant to colistin. Additionally, 42 isolates (84 %) had biofilm formation capability. According to rep-PCR results, 34 isolates showed similar banding patterns, while 16 isolates had unique banding patterns. Finally, based on the molecular analysis, there was a direct relationship between biofilm formation and the antibiotic resistance of isolates. In other words, MDR isolates had a higher ability to form biofilm.

Antibiotic resistance poses a persistent threat to modern medicine due to the emergence of novel antibiotic-resistant strains. Therefore, a timely understanding of antibiotic resistance and the virulence biology of pathogenic bacteria, particularly those of public health significance, is crucial for implementing effective mitigation strategies. This study aimed to investigate the virulence profiles of ten S. aureus isolates (NDa to NDj) and ten E. coli isolates (ND1 to ND10) originating from livestock and poultry, and to assess how various cell surface properties and biofilm formation abilities influence antibiotic resistance phenotypes. Antibiotic resistance profiling through phenotypic (AST) and genotypic methods (PCR) confirmed that NDa to NDe were methicillin-resistant S. aureus (MRSA) and ND1 to ND5 were extended-spectrum β-lactamase (ESBL) producing E. coli isolates. Virulence properties such as hemolytic activity, coagulase activity, and nuclease activity were found to be independent of the antibiotic resistance phenotype in S. aureus. In contrast, biofilm formation phenotype was observed to influence antibiotic resistance phenotypes, with MRSA and ESBL E. coli isolates demonstrating higher biofilm formation potency. Chemical and enzymatic analysis of S. aureus and E. coli biofilms revealed proteins and polysaccharides as major components, followed by nucleic acids. Furthermore, cell surface properties such as auto-aggregation and hydrophobicity were notably higher in isolates with strong to medium biofilm-forming capabilities (ESBL and MRSA isolates), corroborated by genomic confirmation of various genes associated with biofilm, adhesion, and colonization. In conclusion, this study highlights that surface hydrophobicity and biofilm formation ability of MRSA (NDa to NDe) and ESBL E. coli (ND1 to ND5) isolates may influence antibiotic resistance phenotypes.

Bacterial septicemia represents a significant disease affecting cultured grass carp culture, with the primary etiological agent identified as the Gram-negative bacterium Aeromonas veronii. In response to an outbreak of septicemia in Guangzhou, we developed a formaldehyde-inactivated vaccine against an A. veronii strain designated AV-GZ21-2. This strain exhibited high pathogenicity in experimental infections across at all developmental stages of grass carp. Mortality rates for grass carp weighing 15 ± 5 g ranged from 16 % to 92 % at exposure temperatures of 19 °C–34 °C, respectively. The median lethal dose (LD₅₀) for grass carp groups weighing 15 ± 5 g, 60 ± 10 g, 150 ± 30 g and 500 ± 50 g were determined to be 1.43, 2.52, 4.65 and 7.12 × 10⁷(CFU/mL), respectively. We investigated the inactivated vaccine in conbination with aluminum hydroxide gel (AV-AHG), Montanide ISA201VG (AV-201VG), and white oil (AV-WO) adjuvants. This study aimed to optimize inactivation conditions and identify the adjuvant that elicits the most robust immune response. The AV-GZ21-2 inactivated bacterial solution (AV),when combined with various adjuvants, was capable of inducing a strong specific immune response in grass carp. The relative percent survival (RPS) following a lethal challenge with AV-GZ21-2 were 94 % for AV-AHG, 88 % for AV-201VG, 84 % for AV-WO and 78 % for AV alone. The minimum immunization dose of the AV-AHG vaccine was determined to be 6.0 × 10⁷ CFU per fish, providing immunity for a duration of six months with an immune protection level exceeding 75 %. Furthermore, the AV-AHG vaccine demonstrated significant protective efficacy against various epidemic isolates of A. veronii. Consequently, we developed an inactivated vaccine targeting a highly pathogenic strain of A. veronii, incorporating an aluminum hydroxide gel adjuvant, which resulted in high immune protection and a duration of immunity exceeding six months. These findings suggest that the AV-AHG vaccine holds substantial potential for industrial application.

Purpose

Pseudomonas plecoglossicida belongs to the Pseudomonas putida group and is a common aquatic pathogen that induces visceral lesions in fish. However, it has never been previously isolated from human specimen and associated with human infections. In the study, we first investigated the pathogenicity of Pseudomonas plecoglossicida strain “SXY” isolated from a child with infectious pneumonia.

Methods

Using 16S rRNA sequencing, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis, and unique biochemical phenotypes, we isolated and identified Pseudomonas plecoglossicida in clinical practice, a highly suspicious pneumonia-related pathogen based on bacteriological examinations and clinical manifestations. Its pathogenicity was assessed and compared with that of Pseudomonas putida clinical strain “ECL” (a recognized pathogen in the Pseudomonas putida group) by a series of in vitro pathogenicity tests (including the growth capacity assay at 37 °C, the lung leukocyte-killing and inflammatory factor release assay, and the whole blood-killing, serum-killing and complement sensitivity assay).

Results

All tests demonstrated its ability to cause colonization, infection, and inflammation in the lungs. However, the pathogenicity and risk of bloodstream infection of Pseudomonas plecoglossicida strain “SXY” were limited and weaker than those of Pseudomonas putida strain “ECL”. Notably, Pseudomonas plecoglossicida could be incorrectly identified as Pseudomonas putida, based on the biochemical identification of VITEK-2, potentially leading to a high rate of missing infections.

Conclusions

Pseudomonas plecoglossicida is a potential and neglected pneumonia pathogen.

Mastitis remains a paramount economic threat to dairy livestock, with antibiotic resistance severely compromising treatment efficacy. This study provides an in-depth investigation into the multidrug resistance (MDR) mechanisms in bacterial isolates from bovine mastitis, emphasizing the roles of antimicrobial resistance genes (ARGs), biofilm formation, and active efflux systems. A total of 162 Staphylococci, eight Escherichia coli, and seven Klebsiella spp. isolates were obtained from 215 milk samples of clinical and subclinical mastitis cases. Antibiotic susceptibility testing identified Twenty Staphylococci (12.35 %), six E. coli (75 %) and seven Klebsiella (100 %) identified as MDR displaying significant resistance to β-lactams and tetracyclines The Multiple Antibiotic Resistance (MAR) index of these isolates ranged from 0.375 to 1.0, highlighting extensive resistance. Notably, 29 of the 33 MDR isolates produced biofilms on Congo red agar, while all exhibited biofilm formation in the Microtitre Plate assay. Critical ARGs (blaZ, blaTEM, blaCTX-M, tetM, tetA, tetB, tetC, strA/B, aadA) and efflux pump genes (acrB, acrE, acrF, emrB, norB) regulating active efflux were identified. This pioneering study elucidates the synergistic contribution of ARGs, biofilm production, and efflux pump activity to MDR in bovine mastitis pathogens. To our knowledge, this comprehensive study is the first of its kind, offering novel insights into the complex resistance mechanisms. The findings underscore the imperative need for advanced antibiotic stewardship and strategic interventions in dairy farming to curb the rise of antibiotic-resistant infections, thereby protecting both animal and public health.

Given the ability of Staphylococcus aureus to form biofilms and produce persister cells, making infections difficult to treat with antibiotics alone, there is a pressing need for an effective antibiotic adjuvant to address this public health threat. In this study, a series of quinone derivatives were evaluated for their antimicrobial and antibiofilm activities against methicillin-susceptible and methicillin-resistant S. aureus reference strains. Following analyses using broth microdilution, growth curve analysis, checkerboard assay, time-kill experiments, and confocal laser scanning microscopy, menadione was identified as a hit compound. Menadione exhibited a notable antibacterial profile (minimum inhibitory concentration, MIC = 4–16 μg/ml; minimum bactericidal concentration, MBC = 256 μg/ml) against planktonic S. aureus and its biofilms (minimum biofilm inhibitory concentration, MBIC₅₀ = 0.0625–0.25 μg/ml). When combined with oxacillin, erythromycin, and vancomycin, menadione exhibited a synergistic or additive effect against planktonic cells and biofilms of two S. aureus reference strains and six clinical isolates, highlighting its potential as a suitable adjuvant for further development against S. aureus biofilm-associated infections.

Brucellosis is a zoonotic disease caused by Brucella, which is difficult to eliminate by conventional drugs. Therefore, a novel multi-epitope vaccine (MEV) was designed to prevent human Brucella infection. Based on the method of “reverse vaccinology”, cytotoxic T lymphocyte epitopes (CTLEs), helper T lymphocyte epitopes (HTLEs), linear B-cell epitopes (LBEs) and conformational B-cell epitopes (CBEs) of four Brucella proteins (VirB9, VirB10, Omp 19 and Omp 25) were obtained. In order to keep the correct protein folding, the multiple epitopes was constructed by connecting epitopes through linkers. In view of the significant connection between human leukocyte antigen CTLA-4 and B7 molecules found on antigen presenting cells (APCs), a new vaccine (V_C4MEV) for preventing brucellosis was created by combining CTLA-4 immunoglobulin variable region (IgV_CTLA-4) with MEV protein. Immunoinformatics analysis showed that V_C4MEV has a good secondary and tertiary structure. Additionally, molecular docking and molecular dynamics simulation (MD) revealed a robust binding affinity between IgV_ CTLA-4 and the B7 molecule. Notably, the vaccine V_C4MEV was demonstrated favorable immunogenicity and antigenicity in both in vitro and in vivo experiments. V_C4MEV had the potential to activate defensive cells and immune responses, offering a hopeful approach for developing vaccines against Brucella in the upcoming years.

Streptococcus agalactiae (S. agalactiae) is an opportunistic pathogen, and to date, studies have mainly focused on S. agalactiae strains isolated from humans, dairy cows, and fish. We reported one S. agalactiae strain, named CFFB, which was isolated from a healthy Sichuan golden snub-nosed monkey. Classical bacteriological approaches, as well as, next-generation sequencing, comparative genomics, and mice challenge test were used to characterize this strain. CFFB was identified as serotype III, ST19 combination which is a common type found in human strains. Phylogenetic analysis showed that the genome of CFFB was closely related to human clinical isolates, rather far away from animal strains. In total, CFFB contained fewer virulence-associated genes and antibiotic resistance genes than human isolates that were close to CFFB in evolutionary relationships. In the mice challenge test, CFFB had a relative weak virulence that just caused death in 33 % of ICR mice at a dose of 10⁸ CFU by intraperitoneal injection, and CFFB was reisolated from the cardiac blood of the dead mice. Meanwhile, two intact prophages (prophage 1 and 2) were identified in the CFFB genome and shared high similarities with phage Javan52 and Javan29 which from human S. agalactiae isolate Gottschalk 1002A and RBH03, respectively. Moreover, the type II-A CRISPR-Cas system was detected in the CFFB genome, and the spacers from CFFB were the same to the streptococci isolates from human. These results suggest that CFFB isolated from healthy Sichuan golden snub-nosed monkeys may have its origin in human S. agalactiae. Our results suggested some genomic similarities between the S. agalactiae colonized in Sichuan golden snub-nosed monkey and those in infected humans.

This study aims to investigate the drug resistance, regulation mechanism of quorum sensing system, expression of related virulence genes, and epidemiological characteristics of carbapenem-resistant Pseudomonas aeruginosa (CRPA).In this study, Polymerase chain reaction amplification was performed to evaluate carbapenemase genes, OprD2 gene, quorum sensing system, and related virulence genes. Bacterial genotypes were analyzed using multilocus sequence typing and evolutionary analysis was conducted based on the goeBURST algorithm. The results demonstrated that a total of 47 CRPA strains were collected in this study, primarily from respiratory specimens in the ICU. Drug sensitivity results showed that the resistance rates of the 47 CRPA strains were highest for imipenem (97.87 %). The loss of OprD2 may be the main factor contributing to carbapenem resistance in our hospital's CRPA strains.All isolates tested positive for the quorum sensing system genes lasI and rhlI/R, and the virulence gene lasB was detected in all isolates, while the algD gene was detected in 19.15 % of the isolates. Among the 47 strains, 6 were untypeable, and the 41 strains with 28 different sequence types were clustered into three clonal complexes (BG1, BG2, and BG3).In conclusion, the CRPA isolates from our hospital exhibit high genetic diversity, with the deletion of the OprD2 gene possibly being the primary determinant of carbapenem resistance in Pseudomonas aeruginosa.Moreover, Las and RhI systems play a key role in quorum sensing signal system. Further research and development of drugs targeting quorum sensing signaling system may provide valuable guidance for the treatment of CRPA.

Neurotropic viruses, characterized by their capacity to invade the central nervous system, present a considerable challenge to public health and are responsible for a diverse range of neurological disorders. This group includes a diverse array of viruses, such as herpes simplex virus, varicella zoster virus, poliovirus, enterovirus and Japanese encephalitis virus, among others. Some of these viruses exhibit high neuroinvasiveness and neurovirulence, while others demonstrate weaker neuroinvasive and neurovirulent properties. The clinical manifestations of infections caused by neurotropic viruses can vary significantly, ranging from mild symptoms to severe life-threatening conditions. Extracellular vesicles (EVs) have garnered considerable attention due to their pivotal role in intracellular communication, which modulates the biological activity of target cells via the transport of biomolecules in both health and disease. Investigating EVs in the context of virus infection is crucial for elucidating their potential role contribution to viral pathogenesis. This is because EVs derived from virus-infected cells frequently transfer viral components to uninfected cells. Importantly, EVs released by virus-infected cells have the capacity to traverse the blood-brain barrier (BBB), thereby impacting neuronal activity and inducing neuroinflammation. In this review, we explore the roles of EVs during neurotropic virus infections in either enhancing or inhibiting viral pathogenesis. We will delve into our current comprehension of the molecular mechanisms that underpin these roles, the potential implications for the infected host, and the prospective diagnostic applications that could arise from this understanding.