International Journal of Microbiology最新文献

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.

Slaughterhouses are aimed at controlling organic matter and pathogens during animal processing; however, wastewater discharge often introduces microorganisms into the environment. This investigation focused on the isolation and characterization of thermotolerant Escherichia coli strains exhibiting pathogenicity, multidrug resistance, and biofilm-forming capacity from wastewater collected at the Kaptan Bazar slaughterhouse in Dhaka, Bangladesh. Seventy E. coli isolates were identified using selective culture media (MacConkey and eosin methylene blue agar) and PCR targeting the uidA gene. Antibiotic susceptibility was assessed using the Kirby-Bauer and modified Hodge methods. Biofilm formation was evaluated through the crystal violet assay. The presence of antibiotic resistance, virulence, and biofilm-associated genes was determined by conventional PCR. The most common virotypes were EIEC (7.14%), followed by ETEC (2.86%) and EHEC (1.43%). Extended-spectrum β-lactamase (ESBL) genes blaTEM (6.94%) and blaCTX-M-15 (2.78%) were detected. Carbapenem resistance genes included blaIMP-1 (3.70%), blaIMP-4 (1.85%), blaOXA-48 (21.76%), blaOXA-47 (0.46%), and blaOXA-1 (1.39%). Eleven isolates tested positive for carbapenemase production via the modified Hodge test. Non-β-lactam resistance genes detected included dfrA17 (25.46%), tetA (13.89%), sul2 (6.48%), qnrS (6.48%), and qnrB (3.24%). Class 1 integrons were present in 16 strains (22.86%), while both Class 2 and 3 integrons were absent. Colistin MIC values ranged from ≤ 0.5 to 2 μg/mL. Plasmid analysis showed that 59 isolates (84.29%) carried plasmids ranging in size from > 500 bp to > 10 kb. The crystal violet assay indicated that 74.29% of the isolates were biofilm producers, with 68.57% forming weak biofilms. Most weak biofilm formers and all moderate biofilm formers carried multiple antibiotic resistance genes. The results underscore a significant presence of antimicrobial-resistant and biofilm-producing E. coli in slaughterhouse effluents, highlighting the potential dissemination of ARGs into the surrounding ecosystem and food chains, posing a serious public health risk. The evidence also points to the urgent necessity for enhanced hygiene and treatment protocols to mitigate environmental and public health risks.

Antibiotics are molecules produced by a microbe to inhibit the growth of another microbe. Due to prolonged improper use, the situation in which these antibiotics do not work effectively on these microbes is termed antibiotic resistance or antimicrobial resistance (AMR). Aquaculture farming is one of the major industries in the world today due to the increasing consumption of seafood. Major antibiotics used in aquaculture farms include oxytetracycline, amoxicillin, ciprofloxacin, and azithromycin. The review paper has focused on the types and modes of action of major antibiotics, the mechanism of AMR, the dissemination of AMR in the ecosystem, and their impacts on human health. Moreover, it summarized the use of various antibiotics in aquafarms in Bangladesh and in different countries of the world. Due to the extensive use of these antibiotics, AMR has become a concerning public health issue all over the world. The article also tried to provide insights into the mechanisms of AMR of various pathogenic bacteria, which will help to develop new or modified antibiotics to fight against AMR. The knowledge regarding the rate of resistance and sensitivity of different antibiotics is essential and will provide baseline information for the treatment of these pathogenic bacteria.

Intestinal microbiota plays a crucial role in host physiological adaptation, though research on the characteristics of intestinal microbiota in the endangered great bustard Otis tarda has been initiated, with prior studies focusing on gut microbial composition, diversity dynamics, and the impacts of captivity and overwintering periods. Comprehensive insights into geographical differences and short-term temporal dynamics across diverse habitats remain limited. Here, we used fecal environmental (eDNA) metabarcoding to investigate the geographical differences and temporal dynamics of the intestinal microbiota in great bustards from Hebei (HB), Inner Mongolia Autonomous Region (NMG), and Shaanxi (SX) provinces of China, with temporal sampling in two sites (the confluence area of the Yellow River and the Weihe and the Luohe rivers) of SX during December 2024-March 2025. Results revealed that the great bustard intestinal microbiota was dominated by Firmicutes, Proteobacteria, and Bacteroidota at the phylum level, with core genera including Lachnoclostridium, Subdoligranulum, and Blautia. Significant geographical divergence was observed in the NMG population (grassland habitat), which exhibited a unique enrichment of Verrucomicrobiota (especially Akkermansia), while SX (farmland) and HB populations were dominated by Firmicutes. Temporal dynamics in SX showed fluctuations in microbial diversity and composition, which may be linked to temporal dietary shifts in winter (inferred from habitat vegetation characteristics, as direct diet measurement was not conducted). Functional predictions indicated conserved metabolic functions across populations, with variations in genetic information processing and environmental adaptation-related functions. These findings highlight that the great bustard's intestinal microbiota may be shaped by habitat-specific factors (i.e., diet and environment, inferred from habitat type) and temporal changes, providing insights into putative microbial mechanisms underlying the ecological adaptation of the endangered great bustard O. tarda. This study contributes to understanding host-microbiota interactions in endangered avians and supports evidence-based conservation strategies.