Microbial pathogenesis最新文献

Background

Acinetobacter baumannii (A. baumannii) has become a significant nosocomial pathogen globally over the past decade due to the increasing prevalence of antibiotic-resistant isolates. The formation of the mucoid phenotype is a crucial adaptive defense response to external pressure, but the clinical, phenotypic and genotypic characteristics and their relationship with sequence types (ST) and K locus (KL) types remain unclear.

Methods

In this study, we screened a total of 736 A. baumannii isolates, from which we identified and characterized 13 mucoid isolates. The study explored the clinical characteristics of patients with mucoid isolates, investigated the mucoid phenotype, performed capsule observation, quantified capsule production, and assessed antimicrobial susceptibility. Subsequently, whole-genome sequencing (WGS) was used to analyze the sequence types (ST), loci for capsular polysaccharide (KL), antibiotic resistance genes, virulence genes, and core-genome single-nucleotide polymorphisms (SNPs). Additionally, the virulence of all mucoid strains was evaluated through serum resistance assay, biofilm-forming assay, and Galleria mellonella survival assay.

Results

All mucoid A. baumannii isolates were found to be encapsulated and extremely drug-resistant. Among patients infected with these isolates, 92.3 % had pulmonary infections, and the 30-day mortality rate was 61.5 %. The analysis revealed that not all strains are highly virulent. Whole-genome sequencing (WGS) identified the sequence types as ST136, ST208, ST381, ST195, and ST281, and the capsular types as KL77, KL7, KL33, KL2, and KL3. The ST208 and KL7 isolates exhibited higher virulence and greater biofilm formation, with KL7 isolates also showing higher capsule production. Despite these differences, no significant variations in virulence genes were observed among the mucoid isolates, except for biofilm-associated and quorum-sensing genes. The highly virulent ST208/KL7 strains (AB276, AB313, and AB552) lacked biofilm-associated genes (csuA/BABCDE), indicating these genes do not directly cause differences in biofilm formation.

Conclusion

The mucoid A. baumannii isolates were extensively drug-resistant, and infections caused by these isolates could lead to higher mortality. However, not all strains had high virulence, with variations likely related to specific sequence types (ST) and K locus (KL) types.

Spread of hypervirulent and multi-drug resistant Klebsiella pneumoniae in raw milk is public health concern due to its potential impact on food safety and public health. Therefore, this study investigated antibiotic susceptibility test (AST), antibiotic resistance genes (ARGs), mutations conferring ARGs, virulence factor and plasmid replicons to check prevalence of fosfomycin resistant MDR K. pneumoniae isolated from raw milk samples collected from Saurashtra region of Gujarat, India. K. pneumoniae isolated from raw milk and subjected to disk diffusion assay. From that, MDR along with fosfomycin resistant isolates were analysed for multi locus sequence typing, presence of ARGs, mutations conferring resistance, virulence factors and plasmid replicon types by using its whole genome sequence. Results shows that, among 32 K. pneumoniae, 8 were phenotypically resistant to fosfomycin. As per WGS analysis, 8 MDR isolates were assigned into different sequence types such as ST3321, ST37, ST2715, ST1087, ST3157, ST299 and ST29. Among that, ST37 is well recognized MDR high risk clone reported worldwide and first time reported from raw milk of Saurashtra region of Gujarat, India. ARGs responsible for resistance to fosfomycin (fosA) were found in all 8 isolates. Other ARGs such as blaSHV, kdeA, OqxA, OqxB, dfrA1, sul1, qnrB4, aadA2 and ere(A) were also detected. High diversity of virulence factors was also identified by detection of genes encoding virulence factors related to iron uptake such as entE, fepD, entA, entB, Irp2, fepG, ybtU, ybtP, fepC, ybtA, ybtE, fepB, ybtS, fyuA, ybtQ, ybtT, ybtX, Irp1, adherence such as yagZ/ecpA, yagV/ecpE, yagX/ecpC, yagV/ecpE, ykgK/ecpR and invasion such as fimA, pla, fimC, fimH, fimB, fimE were detected in eight genomes. Mutations in murA, uhpT and glpT conferring a fosfomycin resistance were also present in genomes of 8 K. pneumoniae. IncF was the most common plasmid replicon type detected in all 8 genomes. The study reports high diversity of virulent and multidrug resistant K. pneumoniae in raw milk. Hence, genomic surveillance plans are urgently required for food borne pathogens.

Candida albicans (C. albicans) biofilm infections are quite difficult to manage due to their resistance against conventional antifungal drugs. To address this issue, there is a desperate need for new therapeutic drugs. In the present study, a green and efficient protocol has been developed for the synthesis of 2-amino-4H-pyran-3-carbonitrile scaffolds 4a-i, 6a-j, and 8a-g by Knoevenagel-Michael-cyclocondensation reaction between aldehydes, malononitrile, and diverse enolizable C-H activated acidic compounds using guanidinium carbonate as a catalyst either under grinding conditions or by stirring at room temperature. This protocol is operationally simple, rapid, inexpensive, has easy workup and column-free purification. A further investigation of the synthesized compounds was conducted to examine their antifungal potential and their ability to inhibit the growth and development of biofilm-forming yeasts like fungus C. albicans. According to our findings, 4b, 4d, 4e, 6e, 6f, 6g, 6i, 8c, 8d, and 8g were found to be active and potential inhibitors for biofilm infection causing C. albicans. The inhibition of biofilm by active compounds were observed using field emission scanning electron microscopy (FESEM). Biofilm inhibiting compounds were also tested for in vitro toxicity by using 3T3-L1 cell line, and 4b, 6e, 6f, 6g, 6i, 8c, and 8d were found to be biocompatible. Furthermore, the in silico ADME descriptors revealed drug-like properties with no violation of Lipinski's rule of five. Hence, the result suggested that synthesized derivatives could serve as a useful aid in the development of novel antifungal compounds for the treatment of fungal infections and virulence in C. albicans.

Duck spleen marble-like necrosis disease (DSMND) has been prevalent in Chinese duck farms since 2016. The etiological study was carried out in this study using etiological detection, pathogen isolation, whole genome sequencing, and artificial infection test. A highly pathogenic Riemerella anatipestifer (RA) strain was determined as the etiologic agent. Phylogenomic analysis showed that this RA strain was closely related to duck origin RA strain RCAD0421 and chicken origin RA strain S63. The clinical symptoms and pathological changes of artificial infection ducks were similar to those of clinical cases. This is the first identification of RA as the pathogen of DSMND, which provides a theoretical basis for this disease’ s prevention and control.

A priori, early exposure to a wide range of bacteria, viruses, and parasites appears to fortify and regulate the immune system, potentially reducing the risk of autoimmune diseases. However, improving hygiene conditions in numerous societies has led to a reduction in these microbial exposures, which, according to certain theories, could contribute to an increase in autoimmune diseases. Indeed, molecular mimicry is a key factor triggering immune system reactions; while it seeks pathogens, it can bind to self-molecules, leading to autoimmune diseases associated with microbial infections. On the other hand, a hygiene-based approach aimed at reducing the load of infectious agents through better personal hygiene can be beneficial for such pathologies. This review sheds light on how the evolution of the innate immune system, following the evolution of molecular patterns associated with microbes, contributes to our protection but may also trigger autoimmune diseases linked to microbes. Furthermore, it addresses how hygiene conditions shield us against autoimmune diseases related to microbes but may lead to autoimmune pathologies not associated with microbes.

This report aims to describe the identification of porcine astrovirus 3 (PAstV3) RNA in the central nervous system (CNS) of weaned pigs with clinical signs of neurological disease associated with polioencephalomyelitis in southeastern Brazil. Three, 20 -35 days-old piglets that died after clinical manifestations of a neurological syndrome were submitted to post-mortem evaluations. Tissue samples were examined by histopathology, bacteriology, and molecular assays (RT-PCR, nested-PCR, RT-qPCR, and Sanger sequencing) to detect the primary infectious disease agents associated with neurological disease in pigs. The principal neuropathological alterations occurred in the grey matter of the spinal cord and brainstem resulting in nonsuppurative poliomyelitis and rhombencephalitis. PAstV3 RNA was detected in the CNS samples of all piglets with histopathological evidence of disease and was confirmed by nucleotide sequencing. Nucleic acids from pathogens commonly associated with neurological diseases in pigs, such as porcine teschovirus, porcine sapelovirus, porcine enterovirus G, atypical porcine pestivirus, senecavirus A, and encephalomyocarditis virus was not detected by molecular assays in the three piglets. This is the first report of PAstV3 in piglets with neurological disease and lesions consistent with polioencephalomyelitis in Brazil. This report highlights the importance of monitoring health events that could compromise pig farming productivity and animal welfare.

The switch to alternate cell types by Staphylococcus aureus creates sub-populations even within an active population, that are highly resilient, tolerant to antibiotics and lack clinical symptoms of infection. These cells present a challenge for clinical treatment where even after initial intervention has seemingly cleared the infection, these alternate cell types persist within tissue to revert and cause disease. Small colony variants (SCV) are a cell type which facilitate persistent infection but clinically isolated SCVs are often unstable in laboratory conditions. We have isolated a pair of S. aureus isolates from an individual patient with osteomyelitis presenting with heterogenous phenotypes; a stable SCV (sSCV) and a SCV that reverts upon laboratory culturing to the usual, active and non-SCV cell type. Thus we are able use this pair to investigate and compare the genetic mechanisms that underlie the clinical variatons of SCV phenotype. The switch to the sSCV phenotype was associated with frameshift mutations in the enolase eno and the histidine kinase arlS. The phenoptye of the sSCV was an impeded growth dependent on amino acid catabolism and modulated biofilm. These mutations present potentially a new molecular mechanism which confer persistence within osteomyelitis.

The increasing trend of antimicrobial resistance (AMR) pathogens in aquaculture makes it is imperative to find control measures for AMR pathogens causing high economic losses in aquaculture. In the present study, a multidrug resistance (MDR) Aeromonas hydrophila bacterium was isolated from kidney samples of diseased carp originating from a fish farm in Awankot, Rupnagar, Punjab, India. Moribund-infected fish exhibited large irregular hemorrhages on the external body surfaces, exophthalmia and fin-rot-like lesions. Phenotypic characterization using Rimler-Shotts (RS) media showed characteristic yellow color colonies and beta hemolysis on sheep blood agar. Genotyping using species-specific primers for the rpoB and gyrB genes characterized the isolate as A. hydrophila.

The Multiple Antibiotic Resistance (MAR) index analysis showed that the isolated A. hydrophila had an MAR score of 0.29 signifying its resistance to more than three antibiotics, which underscores the need of finding treatment methods for MDR A. hydrophila isolates causing disease in aquaculture. Bacteriophages are considered a better eco-friendly alternative to antibiotics because of their inherent properties of not causing drug residues and resistance. Of the 13 phages tested, the Aeromonas veronii phage designated as AVP3, initially isolated against Aeromonas veronii, showed lytic activity against the MDR A. hydrophila isolated from diseased carp in this study. In addition, it also showed the lytic activity against Aeromonas spp. And A. caviae indicating that it had lytic properties against a wide host range within the Aeromonas species. This finding points to the potential efficacy of bacteriophages in mitigating pathogenic infections in aquaculture.