International Journal of Microbiology最新文献

Foodborne diseases (FBDs) pose significant challenges to public health and the food industry worldwide, including Saudi Arabia, where rapid urbanization, changes in dietary habits, and a growing food service sector have increased the risk of contamination. As a result, this study analyzed bacterial contamination in food samples from Riyadh, Saudi Arabia, and investigated food poisoning outbreaks in the city. A total of 7897 food samples and swabs collected between 2015 and 2018 were analyzed for coliforms, Salmonella, Staphylococcus aureus, and Bacillus cereus. Clinical data on food poisoning cases and outbreaks were also gathered to assess incidence rates and epidemiological trends. Bacterial identification followed ISO Standards and AOAC Official Methods. The results showed that 7.4% of the samples tested positive for the target pathogens: Salmonella (12.6%), Bacillus cereus (9.8%), and Staphylococcus aureus (3.4%). Females were found to have a slightly higher likelihood of food poisoning compared to males, with the highest incidence observed in the 20-49 age group. Common sources of foodborne illness included poultry (n = 93 cases), unclassified foods (n = 67), meat products (n = 45), rice (n = 38), vegetables (n = 36), and salads (n = 30). Food poisoning cases peaked in June, followed by April and August. This study highlights a significant gap in regional data on FBDs and emphasizes the need for improved surveillance and monitoring systems to reduce the incidence of foodborne illness in the region.

Mycotoxins pose significant threats to food security and human health, necessitating innovative approaches for fungal control. This study investigated the antifungal and antimycotoxigenic potential of lactic acid bacteria (LAB) isolated from agro-industrial byproducts against the toxigenic fungi Aspergillus flavus and Fusarium verticillioides. Then, 14 LAB isolates were phylogenetically characterized, revealing diverse species including Lactiplantibacillus pentosus, Lactiplantibacillus plantarum, Lacticaseibacillus paracasei, and Leuconostoc pseudomesenteroides. Their antagonistic activity was first screened using an overlay-streak assay, which evaluated the combined effects of competition, pH reduction, and metabolite production on mycelial growth. Subsequently, the effect of their neutralized cell-free supernatants (CFS)-containing possible pH-stable antimicrobial compounds-was tested on fungal proliferation. The results revealed a distinct, mode-of-action-dependent efficacy. In the direct coculturing assay, stronger inhibition was observed against F. verticillioides, with six L. pentosus strains achieving nearly 100% growth suppression. In contrast, CFS treatments exhibited a more pronounced inhibitory effect on A. flavus germination and growth rate, with L. plantarum 71(6)-2F showing activity comparable to a positive control. This shift in efficacy is explicitly attributed to the different mechanisms assessed in each assay: the overlay method reflects broad-spectrum inhibition driven largely by competition and acidification, to which F. verticillioides appears highly sensitive. The CFS assay, however, highlights the impact of specific, pH-neutral antimicrobial metabolites. Furthermore, several CFS extracts significantly reduced mycotoxin biosynthesis, suggesting these LAB metabolites can disrupt critical fungal physiological pathways. These findings underscore the potential of LAB from agro-industrial byproducts as a source of natural antifungal and antimycotoxigenic compounds.

Background: In the present study, the probable association of virulence-associated genes (VAGs) with antibiotic resistance and also sample sources in Proteus isolates was investigated.

Methods: Then, 91 Proteus mirabilis and nine Proteus vulgaris were used in this study. The disk diffusion method was used in order to perform an antibiotic susceptibility assessment. A combination double-disc synergy test was used for the evaluation of extended-spectrum β-lactamases. Eight VAGs were investigated by polymerase chain reaction (PCR) method. ERIC-PCR fingerprinting was also performed for P. mirabilis isolates.

Results: Maximum frequency of resistance was detected against trimethoprim-sulfamethoxazole combination in P. mirabilis isolates and against cefalexin in P. vulgaris isolates. Then, 6% of isolates were multidrug-resistant (MDR) and all were P. mirabilis. Community-acquired (CA) isolates were more virulent than hospital-acquired (HA) isolates. The zapA (98%) and atfA (77%) were the most common and less common VAGs, respectively. The study findings showed that mrpA and atfA genes were predictors of sensitivity to some antibiotic agents. The rsbA gene could also be similarly used in order to distinguish CA isolates from HA isolates.

Conclusions: Higher virulence potential of CA isolates in comparison to the HA isolates is suggested. Amikacin, tobramycin, and meropenem were introduced as the most effective antibiotics against Proteus isolates. Our finding primarily introduced some VAGs as biomarkers for predicting antibiotic susceptibility and also in order to differentiate Proteus isolates. However, it has to be confirmed through complementary studies later.

[This corrects the article DOI: 10.1155/ijm/3915271.].

A native strain of Bacillus aryabhattai M2C was isolated from peanut root nodules and confirmed for its ability to fix atmospheric nitrogen under controlled laboratory conditions. To assess its agronomic potential, field experiments were conducted to evaluate the combined effects of bacterial inoculation and vermicompost on peanut growth, yield, and seed nutritional quality. The trial was arranged in a randomized complete block design with two factors: (i) bacterial inoculation (with or without B. aryabhattai M2C) and (ii) three vermicompost levels (0, 5.0, and 10.0 t ha^-1), resulting in six treatment combinations with four replications each. Growth traits, fresh pod yield, and seed nutrient composition were systematically measured. Results showed that although interactions between bacterial inoculation and vermicompost application were not significant for fresh pod yield, inoculation with B. aryabhattai M2C alone increased yield by 7.43% compared with the uninoculated control. Vermicompost at 5.0 and 10.0 t ha^-1 did not differ significantly from each other, but both outperformed the untreated control by 6.12% and 8.81%, respectively, while also improving vegetative growth, biomass accumulation, and seed nutritional quality. Despite the inconsistent interactions across all traits between strain M2C and vermicompost, the bacterial strain combined with vermicompost application contributed to yield improvements compared with the control treatments. The integration of strain M2C with 5.0 t ha^-1 vermicompost appears to be the optimal strategy, reducing vermicompost input while sustaining yield gains. Overall, this integrated approach represents a sustainable and eco-friendly alternative to chemical inputs, with strong potential to improve peanut productivity and support long-term soil fertility management in agricultural ecosystems.

Salmonella Typhi is the causative agent of typhoid fever, a notifiable disease characterized by prolonged fever and gastrointestinal symptoms that may worsen and lead to death. This study was aimed at determining the epidemiological profile of typhoid fever based on clinical cases treated between 1999 and 2018 at the Evandro Chagas Institute, located in the state of Pará, Brazil. A total of 683 cases were analyzed, confirmed through PCR, stool culture, or blood culture. The findings revealed a consistent annual pattern in the number of reported cases, with the highest incidence occurring between June and November. The majority of affected individuals resided in the municipality of Belém, were male, had low levels of formal education, and were predominantly students. The age range of affected individuals varied from 1 to 88 years, with the majority of cases occurring in adults aged 20-59 years. Most cases occurred in urban areas with brick housing, biological septic tanks, dry soil, regular garbage collection, and access to public water supplies. Consumption of potentially contaminated foods, especially açaí, was identified as a probable source of infection. The most frequently reported symptoms included fever, headache, diarrhea, chills, abdominal pain, nausea, vomiting, myalgia, and asthenia. These findings highlight the need to expand knowledge about the still limited epidemiology of typhoid fever in this region in order to support the implementation of effective control and prevention strategies.

β-Lactam resistance is one of the major health concerns today, primarily due to enzymes called β-lactamases. Metallo-β-lactamases (MβLs) can cleave a wide range of β-lactam antibiotics, including carbapenems. These enzymes require zinc (Zn) ions to function and can be inhibited by conventional β-lactamase inhibitors. According to their structural and functional characteristics, MβLs are categorized into three classes known as B1, B2, and B3, each with distinct substrate preferences and resistance mechanisms. The prevalence of acquired MβLs, such as IMP, VIM, and NDM, demonstrates the necessity for the development of effective treatments. Novel therapeutic approaches have emerged as potential treatment options. However, antibiotic toxicity, resistance development, and coexisting resistance mechanisms, such as efflux pumps and porin modifications, complicate treatment strategies. Recent advances in diagnostics have significantly improved the rapid identification of MβL-producing bacteria, suggesting the selection of treatment and antimicrobial stewardship. This review highlights the urgent need for global efforts to combat MβL-mediated resistance through surveillance, advanced diagnostics, and innovative therapies, emphasizing the role of advanced and innovative theragnostic approaches in managing MβL infections.

PD-L1 inhibitor immunotherapies have achieved significant advances in cancer treatment, yet only a subset of patients benefits, with response rates varying widely. Previous studies demonstrated that ultrasonic-stimulated microbubble cavitation (USMC) enhances the antitumor effects of PD-L1 inhibitors, suppressing tumor progression and prolonging survival in murine models. Given the gut microbiome's critical role in antitumor immunity and treatment efficacy, the interplay between USMC, immunotherapy, and gut microbiota remains poorly understood. To investigate this relationship, we conducted 16S rDNA sequencing to analyze the gut microbiota in mice across four treatment groups: control (ck), USMC group (um), PD-L1 inhibitor (pdl1), and USMC+PD-L1 inhibitor (um-pdl1). Our results revealed significant variations in gut microbial composition and abundance among the groups. Notably, we identified a correlation between commensal microbiota profiles and therapeutic responses. Mice treated with pdl1 alone or in combination with um exhibited marked reductions in tumor volume and weight, along with prolonged survival and concurrent shifts in gut microbiota. Multimatrix correlation analysis further identified four bacterial genera (Akkermansia, Bacteroides, Escherichia-Shigella, and Enterococcus) positively associated with treatment efficacy in the pdl1 and um-pdl1 groups. In summary, our findings preliminarily reveal substantial alterations in gut microbiota following tumor development, with the um-pdl1 regimen exerting a pronounced influence on microbial composition.

Persistent pathogens pose a significant global health burden, contributing to increased morbidity and mortality rates worldwide. This study investigates the relationship between clinically relevant biofilm-associated and antibiotic resistance genes in Klebsiella pneumoniae isolates. Biofilm-forming capabilities of the isolates were evaluated, and their biomass was quantitatively analyzed. The presence of biofilm-associated and resistance genes (mrkA, blaSHV, blaTEM, and blaKPC) in the samples was identified using conventional PCR. Gene expression levels were quantified via RT-qPCR under acidic and neutral pH conditions, and the results were analyzed statistically to evaluate significance. All clinical isolates were found to be biofilm formers. PCR analysis revealed that a significant proportion of the isolates harbored the mrkA, blaSHV, and blaTEM genes, with prevalence rates of 78%, 89%, and 63%, respectively. In contrast, the blaKPC gene was absent. Statistical analysis revealed a significant (p = 0.0357) association between the presence of the mrkA gene and elevated expression of the blaSHV gene. Strains harboring the mrkA gene demonstrated higher resistance gene expression compared to mrkA-negative strains, particularly under neutral conditions (pH 7). In conclusion, these findings suggest that biofilm may contribute to antibiotic resistance not just by acting as a physical layer but also by modulating the expression of resistance genes. This observed relationship highlights the importance of designing novel therapies that can target both biofilm and resistance mechanisms to combat persistent infections.

Background: The gut microbiota of insects represents an underexplored reservoir of bioactive compounds with potential antimicrobial applications. This study is aimed at identifying antimicrobial compounds from fungi associated with the gut microbiota of Hermetia illucens (black soldier fly) larvae active against Salmonella enterica serovar Pullorum, an important poultry pathogen.

Methods: Fungi isolated from H. illucens larval gut were screened for antimicrobial activity against S. enterica serovar Pullorum. The active fungus was identified through molecular analysis of ITS, benA, and CaM regions. Ethyl acetate extract from the fungal culture was assessed for antimicrobial activity, followed by bioguided fractionation using preparative and semipreparative chromatography. Active fractions were analyzed using UHPLC/HRMS, and putative compound identification was performed through mass spectrometry and molecular networking.

Result: Aspergillus chevalieri was identified as active against S. enterica serovar Pullorum, with the ethyl acetate extract exhibiting moderate antimicrobial activity (MIC = 4.00 mg/mL; IC₅₀ = 3.00 ± 0.58 mg/mL). Bioguided fractionation resulted in several active fractions. UHPLC/HRMS analysis putatively annotated 10 compounds, previously shown to be bioactive, including diketopiperazines (Neoechinulin A and echinulin), peptide derivatives (cyclo(L-Tyr-L-Pro) and N-acetyltyramine), a benzofuran derivative, an isocoumarin (diaporthin), a flavin (lumichrome), an aminopurine (isopentenyladenine), and two diterpenoids (4-deoxyphorbol-13-acetate and austinoneol).

Conclusion: This study represents the first report of A. chevalieri associated with H. illucens larvae and demonstrates its potential as a source of antimicrobial compounds against S. enterica serovar Pullorum. The identified bioactive compounds provide promising leads for the development of new antimicrobial agents for poultry health.