Journal of Applied Microbiology最新文献

Aims: Determine efficacy of an aqueous photocatalytic disinfection system, photoClO2, against two human norovirus surrogates [feline calicivirus (FCV) and Tulane virus (TuV)] and Clostridioides difficile endospores on stainless steel and nylon carpet.

Methods and results: The photoClO2 system was first optimized with 1% sodium chlorite (NaClO2) and 10 ppm Eosin Y to produce 60.64 ppm ClO2/min in a 4.5×4.5 cm2 area. It was then tested against FCV, TuV, and C. difficile endospores on stainless steel and nylon carpet with two different backings. On stainless steel, photoClO2 achieved a >5 log10 plaque-forming unit (PFU) reduction of FCV in 45 min, >3 log10 median tissue culture infectious dose (TCID50) reduction of TuV in 60 min, and 1.3 log10 colony-forming unit (CFU) reduction of C. difficile endospores in 120 min. Under indoor lighting conditions, photoClO2 achieved a 4.3 log10 PFU reduction of FCV and 1.4 log10 TCID50 reduction of TuV on stainless steel after 120 min. Further, photoClO2 achieved a 2.9 log10 PFU reduction of FCV and 2.5 log10 TCID50 reduction of TuV on nylon carpet with waterproof backing in 60 min, which was higher than carpet with water-permeable backing (1.3 log10 PFU and 1.1 log10 TCID50 reduction, respectively).

Conclusion: ClO2 production rate of the photoClO2 system was influenced by light distribution, while disinfection efficacy was affected by light intensity, surface characteristics, and target microorganisms. PhotoClO2 was efficacious in inactivating both human norovirus surrogates on stainless steel and nylon carpet. Efficacy against C. difficile endospores was limited.

Aim: This study investigates how replacing fishmeal and fish oil with insect meals in feed impacts the gut microbiota in rainbow trout (Oncorhynchus mykiss), a crucial species in aquaculture.

Methods and results: Dietary inclusion of black soldier fly (Hermetia illucens), cricket (Gryllodes sigillatus), and superworm (Zophobas morio) were evaluated for their impact on intestinal microbial diversity and community composition following a 12-week feeding trial. Fish were fed one of four isonitrogenous and isoenergetic diets: a control diet without insect meal, and diets with 15% defatted black soldier fly meal, full-fat adult cricket meal, or full-fat superworm meal. The microbiota of intestinal digesta and fish feed was characterized using 16S rRNA gene sequencing on the Illumina MiSeq platform. Results revealed significantly lower alpha diversity indices in the cricket treatment compared to the control. Beta diversity analysis showed Bacillota as the dominant phylum across all treatments, with the initial stock population richer in Mycoplasmatota. A novel genus within Mycoplasmataceae was prevalent at day 0 and in all treatments. Black soldier fly meal increased an unidentified Peptostreptococcaceae genus (bsv123) compared to control and superworm diets, while cricket meal elevated Streptococcus levels.

Conclusions: Insect-based diets, particularly with black soldier fly meal, significantly alter beta diversity within the gut microbiota of rainbow trout, with cricket meal reducing alpha diversity and superworm having minimal impact.

Aim: This study investigated occurrence of Salmonella in faecal sludge from public toilets in Nigeria, and genetic relatedness of strains which have been reported to cause human infection across Africa.

Methods and results: The study collected 150 human sludge from public toilets, and identified Salmonella through culture and PCR. Isolates were tested for antimicrobial susceptibility and sequenced using Illumina MiSeq. Draft sequences were compared with sequence data from Enterobase and Genbank. Twenty-four (16.0%) of sewage samples were positive for Salmonella [CI95 (10.2- 21.8)]. S. Give (sequence type (ST) 516), S. Seftenberg (ST-14), and S. Chester (ST-411) were the most prevalent serovars found in 45.8%, 16.7%, and 16.7% of samples, respectively. Most of the isolates were sensitive to the antimicrobials tested, only one isolate of S. Derby showed resistance to ampicillin and cefazolin. Notably, 91.7% of the strains had the aac (6)-Iaa gene, and point mutations in parC, gyrA and acrB. S. Chester showed genetic relatedness with strains from Benin Republic and South Africa.

Conclusion: There is genetic relatedness of present strains and those associated with human infections in Africa.

Solid organ transplantation (SOT) recipients have a heightened risk for infection due to prolonged immunosuppressive drug use following transplant procedures. The occurrence of post-transplant infections is influenced not only by the transplanted organ type but also by varied factors. The kidney is the most common organ in SOT, followed by the liver, heart, and lung. This review aims to provide a comprehensive overview of the current epidemiological characteristics of infections after kidney, liver, heart, and lung transplantation, focusing on bacterial, fungal, and viral infections. The incidence and infection types demonstrated significant variability across different SOTs. Furthermore, this review attempts to elucidate the clinical characteristics of infections across patients following different SOTs and contribute to the development of individualized prevention strategies according to infection incidence, ultimately enhancing the quality of life of transplant recipients.

Aims: The main objective of this study was to produce erythronolide B (EB) and 3-O-α-mycarosylerythronolide B (MEB) in Streptomyces coelicolor and enhance the MEB production by expressing the glucose-1-phosphate thymidylyltransferase (RfbA).

Methods and results: We expressed eryF and eryB genes (eryBII, eryBIII, eryBIV, eryBV, eryBVI and eryBVII) to produce EB and MEB. The expression was confirmed by quantitative real-time PCR. Furthermore, the MEB's production was improved by more than 100-fold by expressing an enzyme, RfbA, which is absent from the erythromycin gene cluster, to promote the biosynthesis of TDP-L-mycarose. We discuss the feasibility of alternative Streptomyces species for erythromycin production based on the presence or absence of RfbA.

Conclusions: The RbfA enzyme from Saccharopolyspora erythraea was expressed in S. coelicolor M1152 along with the MEB biosynthesis pathway, resulting in a large increase in MEB production (>100-fold).

Antimicrobial resistance (AMR) is a significant global health concern, due to the persistence of pathogens and the emergence of resistance in bacterial infections. Bacterial-derived antimicrobial peptides (BAMPs) have emerged as a promising strategy to combat these challenges. Known for their diversity and multifaceted nature, BAMPs are notable bioactive agents which exhibit potent antimicrobial activities against various pathogens. This review explores the intricate properties and underlying mechanisms of BAMPs, emphasizing their diverse applications in addressing AMR. Additionally, the review investigates the mechanisms, analyses the challenges in utilizing BAMPs effectively, and examines their potential applications and associated deployment challenges providing comprehensive insights into how BAMPs can be harnessed to combat AMR across different domains.

Aims: The purpose of this study was to explore impacts of different combinations of co-fermentation PGPR broth on the growth and yield of pepper.

Methods and results: The effects of co-fermentation broth containing a random combination of two PGPR strains on the growth of pepper were analyzed. All inoculation treatments promoted growth, yield and quality of peppers. The relative abundance of the dominant Proteobacteria and Sphingomonas was significantly higher in the planted soil at the seedling and fruiting stages, and the soil available nitrogen, phosphorus, and potassium contents were correspondingly higher. In addition, the co-fermented broth of Bacillus velezensis HP9 and Burkholderia pyrrocinia P10 treatment had the most pronounced effect on plant growth, while the combination of Bacillus flexus HGD12 and P10 had the greatest impact on fruit nutritional indices. This is consistent with the highest enrichment of beneficial bacterial genera at the seedling stage in the HP9 and P10 treatment, and at the fruiting stage in the P10 and HGD12 treatment group, respectively.

Conclusions: Different combinations of co-fermented bacterial broths increased soil nutrient contents and changed the bacterial community, which in turn promoted the growth, yield and quality of pepper.

Aims: UV-C based air cleaners may reduce the transmission of infectious diseases. However, microbiological validation is necessary to quantify their efficiency. In this study, the stability of aerosolized bacteriophages for validation purposes was investigated in a test room, before an UV-C based air cleaner was exemplarily evaluated regarding the inactivation of airborne bacteriophages.

Methods and results: The bacteriophage Phi6 was selected as virus surrogate and aerosolized in a room of 30 m³ volume. The recovery of infectious bacteriophages was first analyzed under variation of the relative humidity (20-55% RH) and sampling time. The aerosol studies showed that a low humidity between 20% RH and 30% RH provides a high and stable recovery of bacteriophages Phi6 over 1 h. However, with increasing humidity, the number of infectious airborne bacteriophages Phi6 decreased significantly. At 50% RH, the recovery of Phi6 was 4 orders of magnitude lower compared to 20% RH. The validation of an UV-C based air cleaner was then demonstrated in the test room whereat the decline of infectious airborne bacteriophages was recorded over time. The non-enveloped bacteriophage MS2 was used as a reference. The validation results were significantly different for Phi6 when the humidity in the test room was either 40% RH or 30% RH whereas comparable results were obtained for MS2 at both humidities.

Conclusion: A rising humidity in the test room caused a significant decline in the recovery of infectious airborne bacteriophages Phi6. The result of a quantitative validation of UV-C based air cleaners may therefore be affected by the respective humidity.

Aims: Glucosaminoglucan (β-1,4-linked glucose and glucosamine) produced by a mixotrophic sulfur-oxidizing bacterium, Thiothrix nivea, is a useful cellulose-aminating agent. Lithotrophic and mixotrophic glucosaminoglucan production were examined using fed-batch techniques.

Methods and results: A jar fermenter was used for the fed-batch cultivation. Glucosaminoglucan was extracted from T. nivea using diluted HCl. Lithotrophic growth was detected by feeding with Na2S as the energy source, and 12 mg L-culture-1 of glucosaminoglucan was obtained. In contrast, no growth was observed with Na2S2O3. Similarly, mixotrophic growth in the presence of acetic acid was promoted by Na2S, whereas Na2S2O3 had no effect. When acetic acid and Na2S were added, 470 mg L-culture-1 of glucosaminoglucan was obtained.

Conclusions: T. nivea was cultured and glucosaminoglucan was produced lithotrophically using Na2S for feeding. Na2S is also indispensable for mixotrophic growth and glucosaminoglucan production, indicating that sulfide oxidation pathways control the TCA cycle. The involvement of the SOX pathway (for thiosulfate oxidation) in the activation of energy metabolism is doubtful because neither lithotrophic nor mixotrophic growth was promoted by Na2S2O3. Based on these results, we assumed that T. nivea is facultatively mixotrophic (lithotrophic growth is possible in addition to organotrophic growth in the presence of sulfide (Na2S)), rather than obligately mixotrophic.

Aims: We aimed to investigate the molecular mechanisms underlying the survival of Mycobacterium abscessus when faced with antibiotic combination therapy. By conducting evolution experiments and whole genome sequencing (WGS), we sought to identify genetic variants associated with stress response mechanisms, with a particular focus on drug survival and resistance.

Methods and results: We conducted evolution experiments on M. abscessus, exposing the bacteria to a combination therapy of amikacin and rifabutin. Genetic mutations associated with increased antibiotic survival and altered susceptibility were subsequently identified by WGS. We focused on mutations that contribute to stress response mechanisms and tolerance. Of particular interest was a novel frameshift mutation in MAB_3509c, a gene of unknown function within the upstream open reading frame of whiB7. A MAB_3509c knockout mutant was constructed, and expression of downstream drug resistance genes was assessed by RT-qPCR. Mutation of MAB_3509c results in increased RNA levels of whiB7 and downstream stress response genes such as eis2, which is responsible for aminoglycoside resistance.

Conclusion: Our findings demonstrate the importance of whiB7 in the adaptive stress response in M. abscessus. Moreover, our results highlight the complexity of M. abscessus adapting to drug stress and underscore the need for further research.