RESUMEN

Seed treatment with plant growth-promoting bacteria represents the primary strategy to incorporate them into agricultural ecosystems, particularly for crops under extensive management, such as maize. In this study, we evaluated the seed bacterization levels, root colonization patterns, and root competitiveness of a collection of autochthonous Pseudomonas isolates that have demonstrated several plant-probiotic abilities in vitro. Our findings indicate that the seed bacterization level, both with and without the addition of various protectants, is specific to each Pseudomonas strain, including their response to seed pre-hydration. Bacterization kinetics revealed that while certain isolates persisted on seed surfaces for up to 4 days post-inoculation (dpi), others experienced a rapid decline in viability after 1 or 2 dpi. The observed differences in seed bacterization levels were consistent with the root colonization densities observed through confocal microscopy analysis, and with root competitiveness quantified via selective plate counts. Notably, isolates P. protegens RBAN4 and P. chlororaphis subsp. aurantiaca SMMP3 demonstrated effective competition with the natural microflora for colonizing the maize rhizosphere and both promoted shoot and root biomass production in maize assessed at the V3 grown stage. Conversely, P. donghuensis SVBP6 was detected at very low levels in the maize rhizosphere, but still exhibited a positive effect on plant parameters, suggesting a growth-stimulatory effect during the early stages of plant development. In conclusion, there is a considerable strain-specific variability in the maize seed bacterization and survival capacities of Pseudomonas isolates with plant-probiotic traits, with a correlation in their root competitiveness under natural conditions. This variability must be understood to optimize their adoption as inputs for the agricultural system. Our experimental approach emphasizes the critical importance of tailoring seed bacterization treatments for each inoculant candidate, including the selection and incorporation of protective substances. It should not be assumed that all bacterial cells exhibit a similar performance.

RESUMEN

Peroxydisulfate (PDS) is widely used in field-scale remediation of organically polluted soil, yet PDS is detrimental to the soil microbiome. In this work, sludge-derived hydrochar was used to alleviate the oxidative damage of PDS to the soil ecosystem and simultaneously improve atrazine (ATZ) degradation. Response surfaces showed that ATZ degradation was enhanced with an increased dosage of PDS (regression slope of 24.09) and hydrochar (regression slope of 4.19). In contrast, bacterial abundance was negatively related to PDS dosage but positively to hydrochar dosage. At the optimum dosage of PDS (2.21% dry weight of soil) and hydrochar (5% dry weight of soil), ATZ degradation reached 95.31%, and bacterial abundance recovered to 7.72 log gene copy number g-1 soil (versus 8.44 in raw soil). Hydrochar alleviated the negative impacts of PDS on soil fertility such as urease activity. High PDS dosages (3% dry weight of soil) facilitated the proliferation of Halomonas, while moderate dosages (1.5% dry weight of soil) stimulated Alicyclobacillus. Hydrochar facilitated the growth of functional genera like Comamonas, Cloacibacterium, and Terrabacter. ATZ degradation pathway was positively correlated with Bacillus and nitrogen metabolism pathway. Hydrochar mediated intracellular reactive oxidative species scavenger reactions in catalase activity, allowing microbial survival under harsh oxidative conditions due to PDS addition.

Asunto(s)

RESUMEN

Helicobacter pylori is a fastidious Gram-negative bacterium that infects over half of the world's population, causing chronic gastritis and is a risk factor for stomach cancer. In developing and rural regions where prevalence rate exceeds 60%, persistence and waterborne transmission are often linked to poor sanitation conditions. Here we demonstrate that H. pylori not only survives but also replicates within acidified free-living amoebal phagosomes. Bacterial counts of the clinical isolate H. pylori G27 increased over 50-fold after three days in co-culture with amoebae. In contrast, a H. pylori mutant deficient in a cagPAI gene (cagE) showed little growth within amoebae, demonstrating the likely importance of a type IV secretion system in H. pylori for amoebal infection. We also demonstrate that H. pylori can be packaged by amoebae and released in extracellular vesicles. Furthermore, and for the first time, we successfully demonstrate the ability of two free-living amoebae to revert and recover viable but non-cultivable coccoid (VBNC)-H. pylori to a culturable state. Our studies provide evidence to support the hypothesis that amoebae and perhaps other free-living protozoa contribute to the replication and persistence of human-pathogenic H. pylori by providing a protected intracellular microenvironment for this pathogen to persist in natural aquatic environments and engineered water systems, thereby H. pylori potentially uses amoeba as a carrier and a vector of transmission.

Asunto(s)

RESUMEN

We evaluated the Copan Eswab transport system for the quantitative recovery of Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa after 1, 2, 3, 5, and 7 days of storage at room and refrigerator temperatures, and 7 and 30 days of storage at -80 °C and -20 °C using mono- and polymicrobial samples. The study was based on Clinical and Laboratory Standards Institute (CLSI) M40-A2 standard procedures on the quality control of microbiological transport systems. Eswab met the CLSI standards at room and refrigerator temperatures for all (combinations of) bacterial strains tested. At room temperature, after 24 h, bacterial growth was observed. At -80 °C, bacterial viability was maintained in monomicrobial samples; however, in polymicrobial samples, P. aeruginosa recovery was compromised. Storage at -20 °C was unsuitable. We conclude that specimens collected using Eswab should be transported to the laboratory as soon as possible. If transport or processing is delayed, specimens should preferably be stored at refrigerator temperatures.

Asunto(s)

RESUMEN

Introduction. Bloodstream infections (BSI) are growing in incidence and present a serious health threat. Most patients wait up to 48 h before microbiological cultures can confirm a diagnosis. Low numbers of circulating bacteria in patients with BSI mean we need to develop new methods and optimize current methods to facilitate efficient recovery of bacteria from the bloodstream. This will allow detection of positive blood cultures in a more clinically useful timeframe. Many bacterial blood recovery methods are available and usually include a combination of techniques such as centrifugation, filtration, serum separation or lysis treatment. Here, we evaluate nine different bacteria recovery methods performed directly from blood culture.Aim. We sought to identify a bacterial recovery method that would allow for a cost-effective and efficient recovery of common BSI pathogens directly from blood culture.Methods. Simulated E. coli ATCC 25922 blood culture was used as a model system to evaluate nine different bacteria recovery methods. Each method was assessed on recovery yield, cost, hands-on time, risk of contamination and ease of use. The highest scoring recovery method was further evaluated using simulated blood cultures spiked with seven of the most frequently occurring bloodstream pathogens. The recovery yield was calculated based on c.f.u. count before and after each recovery method. Independent t-tests were performed to determine if the recovery methods evaluated were significantly different based on c.f.u. ml-1 log recovery.Results. All nine methods evaluated successfully recovered E. coli ATCC 25922 from simulated blood cultures although the bacterial yield differed significantly. The MALDI-TOF intact cell method offered the poorest recovery with a mean loss of 2.94±0.37 log c.f.u. ml-1. In contrast, a method developed by Bio-Rad achieved the greatest bacterial yield with a mean bacteria loss of 0.27±0.013 log c.f.u. ml-1. Overall, a low-speed serum-separation method was demonstrated to be the most efficient method in terms of time, cost and recovery efficiency and successfully recovered seven of the most frequent BSI pathogens with a mean bacteria loss of 0.717±0.18 log c.f.u. ml-1.Conclusion. The efficiency of bacterial recovery can vary significantly between different methods and thereby can have a critical impact on downstream analysis. The low-speed serum-separation method offered a simple and effective means of recovering common BSI pathogens from blood culture and will be further investigated for use in the rapid detection of bacteraemia and susceptibility testing in clinical practice.

Asunto(s)

RESUMEN

ABSTRACT: The use of high-throughput methods allows a better characterization of food-related bacterial communities. However, such methods require large amounts of high-quality bacterial DNA, which may be a challenge when dealing with a complex matrix that has a low concentration of bacteria, such as fresh fish fillets. Therefore, the choice of method used to recover bacteria from a food matrix in a cost-effective way is critical, yet little information is available on the performance of commonly used methods. We assessed the recovery capacity of two such methods: stomaching and mechanical rinsing. The efficiency of the methods was evaluated through quantitative recovery and compatibility with end-point quantitative PCR (qPCR). Fresh rainbow trout (Oncorhynchus mykiss) fillets were inoculated with a bacterial marker, Brochothrix thermosphacta, at different concentrations (7.52 to 1.52 log CFU/g). The fillets were processed by one of the two methods, and the recovery of the marker in the suspensions was assessed by plate counting and qPCR targeting B. thermosphacta-rpoC. The same analyses were performed on six noninoculated fresh fillets. Stomaching and mechanical rinsing allowed efficient and repeatable recovery of the bacterial communities from the 42 inoculated fillets. No significant differences in recovery ratios were observed between the marker enumerated in the inoculation suspensions and in the corresponding recovery suspensions after rinsing and stomaching. However, the stomaching method allowed too many particles to pass through the filters bag, making necessary a limiting supplementary filtration step. As a consequence, only the rinsing recovery method allowed proper PCR quantification of the inoculated B. thermosphacta. The mean recovered bacterial level of the fillets was approximately 3 log CFU/g. It seems more relevant and cost-effective to recover the endogenous bacterial microbiota of a fish fillet structure using the rinsing method rather than the stomaching method.

Asunto(s)

RESUMEN

Many brands of filtering facepiece respirators are used against air pollution, including bioaerosols; however, studies have explored exposure to bioaerosols from the inside surfaces of respirators. We evaluated the filtration efficiencies and microbial recovery rates of commercial filtering facepiece respirators against bioaerosols. Eight filtering facepiece respirators and one surgical mask were selected, all with high market shares in the Republic of Korea and certified by national or international standards. The tested filtering facepiece respirators were installed on the head of a mannequin under various airflow velocity and relative humidity (RH) conditions. The filtration efficiency against Staphylococcus epidermidis and Escherichia coli bioaerosols, the pressure drop of the filter, and the relative recovery rates for the bacteria were evaluated. The filtration efficiency of each filtering facepiece respirator ranged from 82% to 99%, depending on the filtration grade. The pressure drop was significantly affected by variations in the surrounding RH. The mean relative recovery rates of all filtering facepiece respirators were 14 ±â€¯4.8% and 9 ±â€¯4.7% for S. epidermidis and E. coli, respectively. These results indicate that airborne microorganisms can survive and accumulate on the surfaces of filtering facepiece respirators, which may lead to harmful health outcomes. Our findings will be useful as background information for the development of commercial filtering facepiece respirators while considering their biological properties and reliable guidance to users.

Asunto(s)

RESUMEN

OBJECTIVE: To evaluate the antibacterial activity of levofloxacin, moxifloxacin and nemonoxacin against Staphylococcus aureus in vitro. To assesse the impact of gyrA and parC genes mutant on resistance for quinolones and the sequences of gyrA and parC genes for three quinolones. METHODS: The MICs of 50 S. aureus were detected by agar dilution method. The MIC and MPC against four S. aureus which were special gene mutations were detected by agar dilution method. Based on these results, bacterial recovery growth curve of levofloxacin, moxifloxacin and nemonoxacin were traced. RESULTS: Nemonoxacin demonstrated activities 8- to 32- fold more potent(MICs at which 90% of isolates were inhibited, 0.5 μg·mL-1) than those of moxifloxacin(MIC90, 2 μg·mL-1) and levofloxacin (MIC90, 16 μg·mL-1) against 50 S. aureus.In condition of the same drug concentrations, the bacterial recovery growth ratios of nemonoxacin was the lowest, while levofloxacin's was the highest. RN450A3 recovery growth ratio was highest compared with other mutant bacterial strains, while RN450 recovery growth ratio was lowest. CONCLUSION: The antibacterial activities of nemonoxacin, moxifloxacin and levofloxacin against S. aureus in vitro are:nemonoxacin> moxifloxacin >levofloxacin. Compared with levofloxacin and moxifloxacin, nemonoxacin inhibits bacteria in a lower concentration, and nemonoxacin is utterly efficacious with different genes mutant strains.The target preference of levofloxacin may be the parC gene of topoisomerase IV, while moxifloxacin and nenomoxacin can almost act on the gyrA and parC gene at the same time.

RESUMEN

Biological specimens for microbiological analysis are often collected in BD Vacutainers®, which are not specifically designed for microbial recovery. Bacterial and fungal recovery was analyzed for glass and plastic tubes with or without clot-activating silica. No significant impact was found for the recovery of most bacteria and yeasts tested, however, Haemophilus influenzae recovery from cerebrospinal fluid was significantly reduced in both glass and plastic clot activator tubes.

Asunto(s)