International Journal of Microbiology最新文献

The rapid emergence of multidrug-resistant (MDR) pathogens, particularly in hospital wastewater, poses a serious threat to public health and emphasizes the need for alternative antimicrobial strategies. In this study, Enterococcus hirae, an environmentally derived strain, was used for the first time in the extracellular green synthesis of zinc oxide nanoparticles (ZnO NPs) and copper oxide/zinc oxide nanoparticles (CuO/ZnO NPs). The nanoparticles were characterized using standard techniques. Ultraviolet-visible (UV-Vis) spectra, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDS) confirmed both nanoparticle formation, size, and morphology. Antimicrobial activity against Staphylococcus aureus (ATCC 6538), Morganella morganii, Kerstersia gyiorum, and Klebsiella pneumoniae was evaluated using minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) assays, showing a 62.5% greater efficacy of bimetallic NPs than ZnO alone. The 2,2-diphenyl-1-picrylhydrazyl hydrate (DPPH) assay revealed that E-CuO/ZnO NPs exhibited superior antioxidant activity with the lowest IC₅₀ of 5.528 μg/mL, outperforming E-ZnO NPs, which is attributed to the synergistic effect between ZnO and CuO NPs. The combination of E-ZnO and E-CuO/ZnO nanoparticles with ciprofloxacin (CIP) and ceftazidime (CAZ) was evaluated against MDR isolates. Synergistic interactions were observed particularly against K. pneumoniae. This study confirms effective E. hirae-mediated synthesis and the enhanced antibacterial and antioxidant potential of CuO/ZnO NPs, supporting eco-friendly strategies against MDR infections, with synergistic interactions observed with conventional antibiotics, particularly against K. pneumoniae, indicating that the nanoparticles can enhance antibiotic efficacy.

Klebsiella pneumoniae is associated with high antimicrobial resistance and is commonly isolated from colonization and healthcare-associated infections (HAIs). This study is aimed at developing and validating molecular assays to detect resistance genes belonging to the bla family in resistant K. pneumoniae isolates. The genes included belong to the subfamilies: blaSHV, blaTEM, blaNDM, blaKPC, blaGES, blaCTX-M, and relevant variants of the blaOXA subfamily. The identified genotypic profile showed a high prevalence of genes belonging to Ambler's classes of beta-lactamases A, B, and D, which was in accordance with the phenotypic results obtained for the isolates investigated. A high prevalence of resistance to penicillins, cephalosporins, and carbapenems was observed. In conclusion, the assays developed were efficient in detecting the main resistance genes of the bla family in K. pneumoniae, revealing a concerning regional burden of resistance genes.

Indigenous backyard poultry is the predominant type of poultry in developing countries. Rural smallholder farmers in these regions usually adopt the free-range (backyard) production system, which exposes the poultry to diverse environments and a broad spectrum of microorganisms that influence their diet and gut microbiota. In this cross-sectional purposive study, we evaluated the microbial community profiles of indigenous backyard poultry and their antimicrobial resistance genes (ARGs) using both cecal samples, which provide a more accurate representation of the core gut microbiota, and fecal samples, which allow for noninvasive monitoring and pathogen screening. We analyzed 32 pooled fecal and cecal samples using shotgun metagenomics, followed by functional and antimicrobial resistance (AMR) analyses to identify genes and metabolic pathways associated with poultry gut health and production. We report the presence of many commensal microorganisms in indigenous backyard poultry, with the most abundant being Bacteroidetes, Firmicutes, and Proteobacteria. The most dominant genera in the feces were Bacteroides, Methanobrevibacter, and Phocaeicola, while Bacteroides, Methanobrevibacter, and Chlamydia dominated in the ceca. No marked differences in microbial diversity were observed between the fecal and cecal samples. KEGG and COG database analyses revealed significantly enriched pathways associated with metabolism, cellular processes, and information storage and processing. Genes that confer resistance to tetracycline were the most abundant, raising concerns about the risks associated with inappropriate and excessive use of this antibiotic in poultry treatment. These findings deepen our understanding of the poultry gut microbiome, particularly regarding indigenous backyard poultry. Furthermore, the information about ARGs is a valuable indicator of antimicrobial use by rural smallholder farmers who have adopted the free-range production system in Kenya and other developing countries. These insights are crucial for farmers and the national livestock sector to monitor AMR in poultry, thereby enabling improved poultry management practices and informed policy decisions.

Enterococcus faecalis is an opportunistic pathogen of growing concern in both human and veterinary medicine due to its virulence traits, biofilm-forming ability, and resistance to multiple antibiotics. This study was aimed at investigating the occurrence, virulence factors, biofilm formation, and antimicrobial resistance (AMR) of E. faecalis in layer parent stock birds in Bangladesh. Samples (n = 80) were collected from healthy (cloacal swabs, n = 60) and dead (liver tissues, n = 20) birds. PCR was used for E. faecalis confirmation and detection of virulence genes. Biofilm formation was assessed using Congo red agar, and antimicrobial susceptibility was determined by disc diffusion. E. faecalis was detected in 76.3% of samples, with higher detection in live birds (80%) than in dead birds (65%). Biofilm production was found in 75.4% of isolates, with a higher rate in dead birds (84.6%) than live birds (72.9%). Strong and intermediate biofilm-forming capacities were more prevalent in isolates from dead birds. All eight tested virulence genes were commonly distributed, particularly pil (95.8%), ace (93.4%), and agg (91.8%), with no significant differences between live and dead bird isolates. High resistance was observed against ampicillin (93.4%), ciprofloxacin (80.3%), erythromycin (78.7%), and tetracycline (72.1%). Multidrug resistance (MDR) was found in 79.2% of isolates from live birds and 69.2% from dead birds, with multiple antibiotic resistance indices ranging from 0.27 to 0.72. To the best of our knowledge, this is the first study in Bangladesh determining MDR and virulence determinants in E. faecalis isolates from layer parent stock. These findings highlight E. faecalis as a prevalent, multidrug-resistant, and virulent bacterium in breeder flocks, emphasizing the need for routine AMR monitoring in parent stock farms.

The increasing use of polylactic acid (PLA) for single-use packaging has led to a growing accumulation of bioplastic waste. This study presents a comprehensive approach for enhancing the degradation of postconsumer PLA packaging waste, beginning with the isolation, screening, and identification of highly effective bacteria and culminating in the statistical optimization of their specific nutritional requirements. From compost samples, two highly effective strains were identified as Bacillus sp. SNRUSAC1 and Priestia aryabhattai SNRUSAC3 based on morphological, biochemical, and 16S rDNA sequence analyses. Notably, this is the first report of PLA degradation by the species P. aryabhattai. Initially, these strains achieved approximately 13% PLA dry weight loss after 56 days. To enhance their efficiency, a statistical optimization of nutritional components was performed. Under the optimized conditions, the degradation efficiency was dramatically enhanced, with SNRUSAC1 and SNRUSAC3 achieving 62.06% and 57.61% dry weight loss, respectively, in only 30 days. This represents over a fourfold increase in degradation in approximately half the time. This optimization also revealed novel, strain-specific requirements, with ferrous sulfate identified as a critical factor that had not been previously reported to influence the growth and degradative activity of P. aryabhattai. These findings establish Bacillus sp. SNRUSAC1 and P. aryabhattai SNRUSAC3 as novel, highly efficient candidates for the biodegradation of PLA plastic waste.

Uropathogenic Escherichia coli (UPEC) is a major cause of more than 80% of urinary tract infections (UTIs), a global health problem, and the second most common infectious disease. UTIs are responsible for approximately 40% of all nosocomial infections and 50% of all bacteremia. Since an approved vaccine against UTIs is not yet approved, evaluating different antigens, injection routes, and adjuvants is necessary to assess the ideal vaccines. In this study, we constructed a fusion protein composed of a truncated form of FimH antigen, the key virulence factor of UPEC, and the FliC antigen of Salmonella typhimurium as an adjuvant. After bioinformatics analysis, the fusion protein was cloned, expressed, and immunologically evaluated in mice. The bladder challenge assay was also used to examine the level of protection in the bladder and kidneys of the immunized mice. The levels of IgG and IgA antibodies in the serum and urine of mice vaccinated with the truncated FimH.FliC (tFimH.FliC) significantly increased compared to the FliC and PBS groups. The cytokine assay showed that tFimH.FliC fusion protein induced higher levels of IFN-γ, IL-4, and IL-17 than the FimH and PBS groups. Additionally, the results of the challenge assay showed a significant decrease in the colony count of bacteria in all of the groups compared to the control group. Our findings showed that the designed candidate can develop effective prophylactic responses against UTIs caused by UPEC strains and that truncated FimH, without an unwanted domain, is an ideal vaccine target.

Depression, a global mental health pandemic, persists with unmet therapeutic needs due to the limitations of conventional antidepressants. Emerging evidence suggests that the microbiota-gut-brain axis (MGB axis) is a crucial regulator of depressive pathophysiology, facilitating bidirectional communication between the gut microbiota and the central nervous system (CNS) through neural, immune, endocrine, and metabolic pathways. This review explores the complex mechanisms underlying MGB dysfunction in depression, including vagus nerve-mediated signaling, cytokine-driven neuroinflammation, and hypothalamic-pituitary-adrenal (HPA) axis dysregulation. Innovations in microbiota-targeted interventions, ranging from probiotic engineering and precision dietary modulation to bacteriophage therapy and AI-driven personalized medicine, have been critically assessed for their potential to restore MGB homeostasis. By linking mechanistic insights with clinical translation, this work outlines a roadmap for transforming the gut microbiota into a therapeutic frontier for depression.

Antimicrobial resistance and environmental impacts have driven the search for effective nonantibiotic strategies in aquaculture. In this study, Bacillus aryabhattai strain CKNJH11 was isolated from shrimp pond sediment and systematically evaluated its suitability as a probiotic both in vitro and in vivo experiments. The results revealed that CKNJH11 spores formed with 95.7% efficiency, survived extreme gastric (pH 2.0, 64.9% viability) and bile salt (5%, 78.1% viability) conditions, and inhibited biofilm formation by Pseudomonas aeruginosa and Vibrio parahaemolyticus by 58.3% and 59.9%, respectively. Hemolysis tests and antibiotic-susceptibility profiling confirmed the strain's safety. To assess its performance in fish, 120 Asian seabass juveniles (initial weight 13.50 ± 0.35 g) were randomly assigned to four diets (1 × 10⁶ CFU/g) as a no-probiotic control, unformulated spores, alginate-encapsulated spores, and spores co-encapsulated with Gracilaria fisheri polysaccharides. After 8 weeks, the co-encapsulated group exhibited the greatest improvements in growth (60.7 ± 1.98 g weight gain (WG) vs. 38.6 ± 1.34 g in controls; p < 0.05), feed conversion ratio (FCR, 5.67 ± 0.18 vs. 8.13 ± 0.37), and immune indices (elevated leukocyte counts and hemoglobin levels). Gut microbiota analysis confirmed successful colonization by B. aryabhattai (3.75-3.93 log CFU/g) and a 60%-75% decline in Vibrio counts (p < 0.05). The enhanced stability and activity afforded by alginate protection combined with prebiotic polysaccharides underscores the potential of this formulation as a sustainable biocontrol agent in aquaculture health management.

Background: The rising incidence of multidrug resistance and drug toxicity has prompted the search for complementary and alternative treatments for bacterial infections.

Objective: This study aimed to screen for the phytochemical present in Psidium guajava leaves, to determine the antibacterial potential of P. guajava leaves, and to compare the effectiveness of the P. guajava leaves against current antibiotics.

Methods: Dried pulverised P. guajava leaves were macerated using different solvents and then concentrated using a rotary evaporator. The extracts were screened for phytochemicals, namely, saponins, alkaloids, tannins, flavonoids, phenols, steroids and terpenoids, according to standard testing procedures. Antibacterial discs were prepared by soaking 6-mm sterile filter paper discs in different concentrations of the various extracts. Antibacterial susceptibility testing was done using the Kirby-Bauer disc diffusion method.

Results: Phytochemical screening confirmed the presence of all tested phytochemicals in Psidium guajava leaf extracts. The ethyl acetate extract (EAE) demonstrated significant antimicrobial activity at 100 mg/mL, showing large zones of inhibition (ZOIs) against Staphylococcus aureus (22.0 ± 6.1 mm), Escherichia coli (16.3 ± 0.9 mm) and Pseudomonas aeruginosa (15.0 ± 0.0 mm). The ethanolic extract (EE) also showed strong activity, with significant ZOI against Klebsiella pneumoniae (22.0 ± 4.3 mm) and P. aeruginosa (14.0 ± 1.0 mm). ZOI for the 100 mg/mL extracts against S. aureus were significantly larger than those for ceftazidime (19 mm), while those against P. aeruginosa exceeded tetracycline (9 mm) (p = 0.001). The MIC results confirmed the strength of the EE, with the lowest values: 3.1 mg/mL against K. pneumoniae ATCC and 6.3 mg/mL against S. aureus, E. coli and P. aeruginosa, possibly due to the presence of saponins.

Conclusions: P. guajava leaves contain many phytochemicals which in turn possess great antibacterial activity and therefore have great potential as a novel complementary and alternative treatment to antibiotics.

Leprosy, one of the oldest diseases, is caused by Mycobacterium leprae and Mycobacterium lepromatosis and continues to pose a significant global public health challenge despite decades of control efforts and the widespread use of multidrug therapy. Clinical manifestations range from tuberculoid to severe lepromatous forms, often accompanied by immune-mediated inflammatory reactions. The disease exhibits a long incubation period, high infectivity, and complex immune-mediated pathology, complicating timely diagnosis and management. Although multidrug therapy comprising rifampicin, dapsone, and clofazimine remains the mainstay treatment recommended by the World Health Organization for leprosy and has proven to be highly effective in managing both multibacillary and paucibacillary forms, the treatment outcomes are hindered by drug resistance, adverse drug reactions, and poor adherence. Resistance primarily arises from genetic mutations in drug target genes such as rpoB, folP1, and gyrA, with additional contributions from efflux mechanisms and cell wall impermeability. This narrative review draws upon a comprehensive search of electronic databases to enhance understanding of the genetic mutations associated with drug resistance. It further highlights ongoing research into resistance mechanisms, novel therapeutic options, postexposure prophylaxis, and vaccine development, which are critical for sustaining the effectiveness of multidrug therapy and advancing global leprosy control efforts.