Letters in Applied Microbiology最新文献

In this study, a Cu2O/TiO2 (CuTi) visible-light photocatalytic composite was employed for the treatment of Xanthomonas campestris and X. campestris-infected Brassica napus seedlings. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values against X. campestris were determined to be 8 and 32 μg ml-1, respectively. Transmission electron microscopy analysis demonstrated a direct correlation between the extent of bacterial cell damage and the concentration of CuTi. Noteworthily, a bactericidal rate of 100% was achieved at a concentration of 150 μg ml-1 over a treatment duration of 120 min. Moreover, alterations in active oxidants and antioxidants, including reactive oxygen species, glutathione reductase, superoxide dismutase, peroxidase, and catalase within the bacterial cells, were examined to elucidate the underlying mechanism of inhibition by the CuTi. The B. napus infected by X. campestris was treated with CuTi, and the efficacy was validated through determination of plant resistance indexes. The combined data confirmed that the CuTi is characterized by a low dose, fast onset, good effect, and higher safety for killing X. campestris, and it is expected to be developed as an antimicrobial agent for vegetables.

Genes conferring antibiotic resistance phenotype, particularly to last resort antibiotics, pose a significant concern globally. Wastewater treatment plant (WWTP) effluent substantially contributes to antibiotic resistance in receiving rivers, threatening human health. Globally, colistin- and carbapenem-resistant Klebsiella pneumoniae infections cause high morbidity and mortality. We investigated colistin-resistant carbapenemase-producing K. pneumoniae (Co-CRKP) isolates in Kathajodi river receiving WWTP effluent, their resistance genes, and pathogenic potential. Four isolates (Co-CRKP-7, Co-CRKP-8, Co-CRKP-10, and Co-CRKP-15) exhibited extensively drug-resistant (XDR) phenotype, harbouring blaTEM-1, blaCTX-M-15, blaNDM-5, and blaOXA-48 genes. Colistin resistance was attributed to mutations in the pmrA and pmrB genes. Virulence genes (fimH, mrkD, entB, iucA, iutA, and irp1), capsular serotypes (K1, K2) and biofilm formation in the isolates explicated their pathogenicity. Furthermore, Inc plasmid replicons (Y, FrepB, P, K/B, L/M, N, FIA, A/C, and FIB) indicated the dissemination potential of the resistance genes in Co-CRKP isolates. The multi-locus sequence typing showed that Co-CRKP-7 and Co-CRKP-8 belonged to ST42, while Co-CRKP-10 and Co-CRKP-15 were ST16 and ST231, respectively. These high-risk clones carrying multidrug resistance and virulence genes, implicated in numerous outbreaks, have spread worldwide. Our findings emphasize the necessity for effective treatment of hospital wastes to restrict the spread of clinical isolates into aquatic environments.

Antimicrobial resistance (AMR) has become one of the most serious threats to One Health. Aquatic environments are an ideal non-clinical AMR reservoir and can act as a key battlefront for tackling the AMR. However, AMR data using the One Health approach remain scarce in aquatic environments worldwide. Here, we extensively assessed AMR in Escherichia coli isolated from urban and rural lake ecosystems using the One Health perspective. A total of 162 E. coli isolates obtained from lakes were tested against 25 antimicrobials using an in-vitro antimicrobial susceptibility testing method. A low (2%) to moderate (45%) drug resistance rate was found for all antimicrobials used in human/veterinary medicine or animal/plant agriculture. However, <80% E. coli isolates exhibited multidrug resistance (MDR) phenotype to highly important (amikacin, gentamicin, trimethoprim) or critically important (amoxicillin, ampicillin, colistin) drugs of both human and veterinary medicine. Of concern, >50% of E. coli isolates exhibited MDR to drugs used as last-resorts (chloramphenicol, colistin) or as frontline (nitrofurantoin, sulfamethoxazole, ampicillin, gentamicin) against E. coli infections. In conclusion, the presence of MDR E. coli strains in urban or rural lake ecosystems highlights their possible role as AMR reservoirs with potential One Health risks.

Vancomycin-resistant enterococci (VRE) are a public health concern as they lead to therapeutic impasses and play a pivotal role in the dissemination of vancomycin resistance genes. As recent evidence suggests that wildlife can play a role in the dissemination of bacterial resistomes, this study explored the potential role of Algerian wild birds as a reservoir of VRE. A total of 222 cloacal and fecal samples were collected from various wild bird species and screened for VRE using a selective medium. Of the 47 isolated strains, 22 were identified as Enterococcus casseliflavus with the vanC2/C3 gene, 24 as Enterococcus gallinarum (19 carrying vanC1 and five carrying vanC2/C3), and one strain as Enterococcus faecalis with the vanC1 gene. Twenty-four (24) strains were multidrug-resistant with 61.7% resistant to rifampicin, while no resistance to teicoplanin, linezolid, and gentamicin was found. Additionally, 53.20% of the strains exhibited at least one virulence factor. To our knowledge, this study represents the first documentation of the vanC1 gene in E. faecalis isolated from wild birds. Furthermore, this gene was found to be carried by a conjugative plasmid, highlighting its ability to spread among bacterial populations and lead to the emergence of novel resistance phenotypes.

The interest in natural compounds has increased primarily due to their beneficial health and environmental aspects. However, natural sources of some compounds, such as bluish pigments, are limited, requiring the development of efficient processes to meet commercial demands. This study isolated a blue-violet bacterium from spoiled cooked rice and identified it as a potential new species of Janthinobacterium through 16S rDNA analysis. Ultra-high performance liquid chromatography-tandem mass spectrometry analyses confirmed that the blue-violet pigment violacein was responsible for the bluish color. In laboratory conditions, different carbon and nitrogen sources were evaluated in submerged culture media to enhance pigment production. Glycerol did not result in significant pigment production by this strain, as expected from previous reports. Instead, a culture medium composed of yeast extract and fructose yielded higher pigment production, reaching about 113.68 ± 16.68 mg l-1 after 120 h. This result provides crucial insights for future studies aiming for sustainable and commercially viable violacein production. Based on a bioeconomy concept, this approach has the potential to supply natural and economic bluish pigments for various industrial sectors, including pharmaceutical, cosmetic, and food.

With the escalation of hospital-acquired infections by multidrug resistant bacteria, understanding antibiotic resistance is of paramount importance. This study focuses on the β-lactamase gene, blaOXA-58, an important resistance determinant identified in a patient-facing hospital wastewater system. This study aimed to characterize the behaviour of the OXA-58 enzyme when expressed using a non-native plasmid and expression host. blaOXA-58 was cloned using a pET28a(+)/Escherichia coli BL21(DE3) expression system. Nitrocefin hydrolysis and antimicrobial susceptibility of OXA-58-producing cells were assessed against penicillin G, ampicillin, meropenem, and amoxicillin. blaOXA-58 conferred resistance to amoxicillin, penicillin G, and ampicillin, but not to meropenem. This was unexpected given OXA-58's annotation as a carbapenemase. The presence of meropenem also reduced nitrocefin hydrolysis, suggesting it acts as a competitive inhibitor of the OXA-58 enzyme. This study elucidates the phenotypic resistance conferred by an antimicrobial resistance gene (ARG) obtained from a clinically relevant setting and reveals that successful functional expression of ARGs is multifaceted. This study challenges the reliability of predicting antimicrobial resistance based solely on gene sequence alone, and serves as a reminder of the intricate interplay between genetics and structural factors in understanding resistance profiles across different host environments.