Natural Microflora Research Articles

Antagonist activities of native rhizosphere micro-flora against groundnut stem rot pathogen, Sclerotium rolfsii Sacc.

BackgroundStem rot caused by Sclerotium rolfsii Sacc. is a major nuisance in groundnut production, causing substantial yield losses in almost all groundnut-growing areas around the world. Biological control is regarded as a sustainable choice over the currently popular management strategy i.e., chemical control, as later has a negative influence on the environment. The present study evaluated the antagonistic effect of native rhizosphere micro-flora against groundnut stem rot pathogen S. rolfsii.ResultsA total of 111 bacterial isolates and 9 Trichoderma isolates isolated from groundnut rhizosphere soil were evaluated for their antagonist activity against S. rolfsii in vitro. Eight isolates (seven bacterial and one Trichoderma) were chosen as prospective biocontrol candidates based on the findings of the dual culture assay. Molecular characterization of these isolates by 16S rDNA and ITS rDNA sequencing confirmed the identity of bacterial isolates as Bacillus spp. (six B. subtilis and one B. amyloliquefaciens) and fungal isolate as Trichoderma asperellum. Also, the selected seven bacterial isolates recorded favourable results for antagonism-promoting biochemical traits.ConclusionThe results of the current study suggested that the native groundnut rhizosphere micro-flora can be exploited for biological control of groundnut stem rot pathogen S. rolfsii. Further research may enable the use of the isolated rhizosphere biocontrol agents as single organisms or in a consortium for sustainable management of the groundnut stem rot pathogen.

Thermosonication combined with ε-polylysine (TSε): A novel technology to control the microbial population and significantly improve the overall quality attributes of orange juice

At present, most commercial orange juice still uses high temperature-long time thermal treatment (HTLT) to prolong its shelf life. However, HTLT treatment can have many negative effects on the overall quality of juice. Therefore, it is of great significance to explore novel non-thermal sterilization techniques to produce high-quality orange juice. In this study, we compared the inactivation effects of thermosonication (TS), TS combined with ε-polylysine (TSε), TS combined with nisin (TSN) and HTLT on the bactericidal effects of natural microflora in orange juice. On this basis, the effects of TSε and HTLT treatments on the comprehensive quality characteristics of orange juice were further explored. The results showed that TSε and HTLT treatments had better effect on controlling the number of microorganisms and inactivating endogenous enzymes, and ε-polylysine showed a significant synergistic lethal ability (p < 0.05) to the total bacterial count and yeast in orange juice. With HTLT treatment, sterilization is not achieved because Alyciclobacillus spores are not inactivated, and it could be replaced by inactivation or pasteurization when the Alyciclobacillus are high. In addition, TSε treatment maintained sensory quality, which was significantly better in TSε-treated juice compared to HTLT-treated juice. Moreover, TSε treatment markedly enhanced or strongly retained the functional substances of orange juice. The contents of polyphenols and carotenoids increased by 12.53% and 36.46%, respectively, while the antioxidant activities of ORAC, DPPH, and FRAP increased by 53.27%, 14.42%, and 7.26%, respectively. Additionally, the retention rate of ascorbic acid was as high as 85.42%. Therefore, as a novel non-thermal inactivation microbial technology, TSε treatment contributes to the improvement of organoleptic quality and functional characteristics of orange juice.

Trends in the development of methods of disposal of bark and bark-wood waste of long-term storage (review)

The present review analyzes the problem of accumulation and utilization of bark and bark-wood waste from wood-working and pulp and paper industries. The methods of utilization are systematized, which differ for "fresh" bark and bark-wood waste of a long shelf life. The essence of biotechnological methods of deep biotransformation of bark-wood waste of long shelf life is described in more detail: composting with the use of mineral fertilizers, stimulation of native microflora, use of activated sludge and artificial consortia of microorganisms, creation of biotechnical systems in the body of bark dumps, solid-phase fermentation of bark-wood waste by xylotrophic fungi. Successful examples of the implementation of methods of biotransformation of bark-wood waste of long-term storage in the bark dumps of pulp and paper enterprises of the Perm Region of Rusian Federation are given. The algorithm of utilization of bark-wood waste by solid-phase fermentation with the help of xylotrophic fungi at the bark dumps of Syktyvkar woodworking plant (Republoc of Komi, Russia) is proposed in order to obtain soil-like substrates and fertilizers, fruit bodies of edible xylotrophic fungi and valuable fungal metabolites for medicine.

Molecular typing of MDR-K. pneumoniae using ERIC-PCR Technique

Klebsiella pneumoniae is a Gram-negative bacterium that exists naturally in the human body's gastrointestinal tract as part of the natural microflora. It has long been recognized as one of the most frequent nosocomial diseases and a multidrug resistant pathogen. The purpose of the current work was to determine the antimicrobial susceptibility and genetic relatedness of K. pneumoniae strains obtained from Ramadi hospitals, western Iraq, using the ERIC–PCR approach. In the period between June and September 2021, 51 K. pneumonia isolates were obtained from Anbar hospitals. After normal laboratory procedures and differential assays identified K. pneumoniae isolates, disk diffusion susceptibility testing was performed. Also, ERIC-PCR was used to determine genetic relatedness of 15 MDR K. pneumoniae isolates. Kirby –bauer disk diffusion test showed that among K. pneumonia isolates, the highest antibiotic resistance was to Augmentin (96%), cefotaxime (92%), ceftriaxone =Ceftazidime (88%), Amikacin (48%), Levofloxaccin (42%), and imipenem (26%). More than 66.66% of the isolates revealed multi-drug resistant phenotypes. ERIC-PCR results and data analysis indicate that there are 23 distinct ERIC types. The findings of this study show an increase in the prevalence of multiresistant K. pneumoniae in the hospitals studied. The ERIC PCR results revealed a high level of genetic diversity across K. pneumoniae strains, showing that K. pneumoniae isolates are polyclonal in Anbar hospitals.

Enterobacter aerogenes B199A May Be an Effective Surrogate for Quantifying Transfer of Salmonella Newport 96E01152C-TX from Cucumber Peel to Edible Flesh and Peeler during Peeling

Fresh cucumbers have been linked to multistate outbreaks of salmonellosis in the United States. Cutting, slicing, shredding, or peeling can transfer pathogens from the surface of fresh produce to the edible flesh portion through tools or hands. Different nonpathogenic surrogates have been used in various intervention studies to predict Salmonella behavior. Little is known about the degree to which pathogens or their surrogates can transfer from the surface of fresh produce to edible flesh during peeling. This study quantifies the transfer of Salmonella Newport from the surface of cucumber to the edible flesh portion or peeler during peeling and evaluates Enterobacter aerogenes B199A, as well as native mesophilic microbiota, as surrogates for Salmonella transfer. Cucumbers were dip inoculated with Salmonella Newport or E. aerogenes at 7 log CFU per cucumber. Half of each inoculated cucumber was hand peeled by using a sterilized peeler, resulting in four separate samples (unpeeled half, edible flesh half, removed peel, and used peeler) to quantify bacterial transfer. Most (>95%) of inoculated E. aerogenes, Salmonella, or native mesophilic microbiota generally remained associated with the peel during peeling. E. aerogenes transfer to cucumber flesh ranged from 0.02 to 12.9%, while transfer to the peeler ranged from 0.01 to 6.6%. Salmonella to cucumber flesh ranged from 0 to 0.6%, while transfer to the peeler ranged from 0 to 2.2%. Native microflora transfer to cucumber flesh ranged from 0.02 to 3.7%, while transfer to the peeler ranged from 0.04 to 3.7%. The log percent transfer of E. aerogenes at 24 h, as well as several shorter times, was not significantly different (P > 0.05) from that of Salmonella transferred to the edible flesh portion or peeler during peeling. E. aerogenes B199A may be a useful surrogate for Salmonella in cross-contamination studies and may help guide future risk management efforts to reduce pathogen risk associated with fresh cucumbers.

Comparison of traditional and probiotic yogurt in relation to their impact on pediatric acute diarrhea patients

Yogurt itself is known to contain probiotic bacteria but the beneficial bacteria present in it does not survive during their passage from the gastrointestinal tract. Therefore, supplementing yogurt with a probiotic species can make it a functionally beneficial dairy product. The aim of this study was to develop traditional and probiotic yogurt, to assess its nutritional composition, and to evaluate its effectiveness in terms of treating diarrhea. Lyofast-LA3 strain of Lactobacillus acidophilus and Bifidobacterium bifidum BB04 were used to supplement yogurt prepared with the standard culture. The traditional yogurt was prepared in the conventional way. After that, proximate composition and clinical intervention were evaluated. The preparation stages represent a gradual improvement in the sensorial properties of both the yogurts. While the proximate analysis of traditional and probiotic yogurt indicated no significant difference in their nutritional composition. The intervention of probiotic and traditional yogurt, resulted in a significant difference between the two groups. After 72 h of administration of probiotic yogurt, only 8% of participants passed watery stool in the experimental group while in the control group, 48%, that is, almost half, of the subjects still passed watery stools. While the frequency remains the same in both groups, about 88% of children passed stool 1–3 times per day at the end of intervention. Novelty impact statement Acute diarrhea is very common in Pakistan, and it could become fatal if not treated properly on time. Therefore, children suffering from acute diarrhea require immediate management of body constituents like minerals, sugars, and fluids. The use of an oral rehydration solution does not affect either the severity or duration of diarrhea immediately. Therefore, administration of probiotics to cure acute diarrhea in a shorter period of time is more favorable not only in terms of symptoms but also in the number of stools passed per day. Yogurt is known to reduce the symptoms of acute diarrhea and have a natural microflora. However, data on the role of traditional yogurt in routine clinical practice compared to that of probiotics are scarce. If we could establish the role of yogurt in reducing the frequency of diarrhea, it will be beneficial for the patients, as yogurt is easily available, is cost effective, and easy to consume orally.

Cultivable microbiota of Proteus anguinus from underground habitats and animals accidently washed to the surface in Croatia

Proteus anguinus (olm) is an amphibian endemic to underground cave systems of the Dinaric karst of Central Europe, adapted to a life in complete darkness. Recent studies have demonstrated the global decline of amphibians due to poorly understood microbiological diseases, emphasizing just how little is known about the natural microflora of amphibians. Not much is known about the olm’s microbiota in their cave habitats, and nothing is known about the microbiology of animals washed to the surface. This observational study describes the microbiological analysis of the skin, cloaca and oral cavity of six olms collected from their cave habitats, and 16 collected after being washed out by flows from two springs, to learn more about the olm’s normal microbiota and possible changes after contact with the different environmental conditions on the surface. Standard microbiological procedures, MALDI-TOF and Real-Time PCR were used for microbiological species identification. All animals tested negative for Ranavirus, Batrachochytrium dendrobatidis, Batrachochytrium salamandrivorans and Chlamydia spp. The most abundant fungi isolated were Penicillium spp. and Cladosporium spp. The washed out animals showed a higher diversity of bacterial flora than those from cave habitats, with Acinetobacter johnsonii, Aeromonas hydrophila, Bacillus spp. and Janthinobacterium lividum as the most frequently identified isolates.

Experimental and model-based characterisation of Bacillus spizizenii growth under different temperature, pH and salinity conditions prior to aquacultural wastewater treatment application

Aquacultural production generates large amounts of wastewater with all its negative effects on life and the environment, particularly caused by elevated amounts of salt and organic matter. Within the natural microflora of such wastewaters, Bacillus spp. are largely present and therefore also actively used within biological treatment. The study conducted here followed work done in Ho Chi Minh City, Vietnam, that examined local aquacultural wastewater samples and identified different strains including species of Bacillus. More specifically in this study, the recently reclassified species Bacillus spizizenii was investigated in closer detail to quantitatively characterise its growth under different temperature, pH and salinity conditions. The strain was grown in flask and lab-scale batch bioreactor cultures. The experimental data obtained was subjected to mathematical modelling to estimate specific growth parameters. The modelling covers, in a newly combined form, logistic and delayed growth as well as growth dependency on temperature, pH and salinity. Major results obtained quantify the best growth conditions at temperature 38.7∘C, pH 7.5 and salinity 6.6 g l−1, although the organism was experimentally shown here to grow delayed at salinities of 54.7 g l−1, with a likely growth at even higher salinities. The results obtained can be used to grow Bacillus spizizenii under best conditions in bioreactors to high biomass to finally apply it to aquacultural wastewater sites.

Enzymative activity of technogenic surface formations of Kuzbass

The coal mining is one of the leading industries in the global energy balance. Kuzbass is the main region of Russia that specializes in coal mining. About 60 % of the country's coal is mined there. Coal mining is carried out mainly by the open-pit method. As a result, some 178 thousand hectares ha of disturbed land are formed. Enzymatic activity is an indicator of soil self-repair. The aim of the work was to study the enzymatic activity of technogenic surface formations of the Kuzbass to assess their toxicity and further selection of destructor microorganisms, rhizobacteria and hyperaccumulator plants, which will be further used at the biological stage of recultivation. As objects of research, the samples of technogenic surface formations taken on the territory of the Barzassky and Mokhovsky coal dumps. Enzymatic activity of technogenic surface formations of dumps was: invertase – 2,24 and 2,12 mg of sucrose split 1 g soil in 1 h; nitrite reductase – 0,57 and 0,07 mg reduced NO2- per 1 g soil in 24 h; asparaginase – 71,22 and 60,63 mg NH3 per 1 g soil in 24 h, respectively. When studying the enzymatic activity, it was assumed that the native microflora uses low- and high-molecular hydrocarbons (alkanes, polycyclic aromatic hydrocarbons (PAH), etc.) as carbon sources. The content of mobile forms of heavy metals (HM) in the studied samples exceeds the maximum allowable concentration by 1,2-2,6 times. In the course of statistical analysis, it was revealed that the gross and mobile forms of zinc and copper are nitrite reductase inhibitors, the gross and mobile form of nickel is an asparaginase activator, in technogenic disturbed formations of the studied coal dumps. Nickel is also an invertase inhibitor in the Mokhovsky coal dump.

Application of Cosmos caudatus Kunth. (ulam raja) extract as antibacterial agent in beef and shrimp meats, and its sensory evaluation

The use of chemical preservatives in food products to inhibit the growth of microorganisms is widely used nowadays. However, their use has become a concern due to several negative side effects, and when consumers question the safety of the foods they eat. Therefore, the present work was conducted to investigate the potential of plant natural sanitiser from Cosmos caudatus Kunth extract to reduce the natural microflora present in raw beef and shrimp meat samples. The present work aimed to investigate the reduction of natural microflora (B. cereus, E. coli, Pseudomonas spp., S. aureus, and L. monocytogenes) in raw beef and shrimp meat samples following sanitisation with different concentrations of C. caudatus extract (0.05, 0.50, and 5.00%) at different soaking times (5, 10, and 15 min). The sanitised samples were further evaluated with sensory acceptability (colour, odour, texture, and overall acceptability) to determine their acceptance level after treatment. Based on the results, the microflora in beef and shrimp meat samples were reduced significantly (p &lt; 0.05) started from 0.05% at varied soaking times. The decrease in bacterial populations was proportional to the increase in extract concentrations and soaking times. In sensory acceptability, all cooked samples achieved acceptance level by the panellists at 0.05% after 10 min of soaking time. Food samples treated with 0.05% of C. caudatus extract and 10 min of soaking time showed the best combination in terms of bacterial reduction and the level of acceptance by the panellists. Hence, it can be concluded that C. caudatus extract has a high potential as a natural-based food sanitiser that can prevent bacterial contamination while maintaining the sensory acceptability of the foods.

A Sweeter Pill to Swallow: A Review of Honey Bees and Honey as a Source of Probiotic and Prebiotic Products.

Honey bees and honey, have been the subject of study for decades due to their importance in improving health. At times, some of the probiotics may be transferred to the honey stored in the honeycomb. Consumers may benefit from consuming live-probiotics honey, which can aid in suppressing the reproduction of pathogens in their digestive system. Prebiotics, on the other hand, are mainly carbohydrates that promote the growth of native microflora probiotics in the digestive tract to maintain a healthy environment and improve the gut performance of the host. Therefore, this narrative review aims to present and analyze ten years’ worth of information on the probiotic and prebiotic potential of honey bees and honey since not many review articles were found discussing this topic. Results showed that not many studies have been performed on the probiotic and prebiotic aspects of honey bees and honey. If further research is conducted, isolated probiotics from the bee’s gut combined with honey’s prebiotic properties can be manipulated as potential sources of probiotics and prebiotics for human and animal benefits since they appear to be interrelated and function in symbiosis.

Microbial Remediation: A Promising Tool for Reclamation of Contaminated Sites with Special Emphasis on Heavy Metal and Pesticide Pollution: A Review

Heavy metal and pesticide pollution have become an inevitable part of the modern industrialized environment that find their way into all ecosystems. Because of their persistent nature, recalcitrance, high toxicity and biological enrichment, metal and pesticide pollution has threatened the stability of the environment as well as the health of living beings. Due to the environmental persistence of heavy metals and pesticides, they get accumulated in the environs and consequently lead to food chain contamination. Therefore, remediation of heavy metals and pesticide contaminations needs to be addressed as a high priority. Various physico-chemical approaches have been employed for this purpose, but they have significant drawbacks such as high expenses, high labor, alteration in soil properties, disruption of native soil microflora and generation of toxic by-products. Researchers worldwide are focusing on bioremediation strategies to overcome this multifaceted problem, i.e., the removal, immobilization and detoxification of pesticides and heavy metals, in the most efficient and cost-effective ways. For a period of millions of evolutionary years, microorganisms have become resistant to intoxicants and have developed the capability to remediate heavy metal ions and pesticides, and as a result, they have helped in the restoration of the natural state of degraded environs with long term environmental benefits. Keeping in view the environmental and health concerns imposed by heavy metals and pesticides in our society, we aimed to present a generalized picture of the bioremediation capacity of microorganisms. We explore the use of bacteria, fungi, algae and genetically engineered microbes for the remediation of both metals and pesticides. This review summarizes the major detoxification pathways and bioremediation technologies; in addition to that, a brief account is given of molecular approaches such as systemic biology, gene editing and omics that have enhanced the bioremediation process and widened its microbiological techniques toward the remediation of heavy metals and pesticides.

Biotechnological Aspects of the Functional Marmalade Development Using Whey for the Gastrointestinal Diseases Prevention

The article reveals the development processes and scientific substantiation of the marmalade of functional use, that is a functional product formulation with biologically active bifidogenic properties contributing to the prevention of the gastrointestinal tract diseases. The research relevance is due to the need to prevent the incidence of a new type of coronavirus COVID-19, that affects many systems of the human body, reduces immunity, while using drug therapy often leads to the natural intestinal microflora violation. To prevent the complications development, it is worth using food products capable of stopping destructive processes in the gastrointestinal mucosa during rehabilitation measures. The researchers developed the cranberry marmalade formulations with the probiotic culture introduction of a different mass fraction: sample 1 with probiotics in a free state, sample 2 with introduced immobilized probiotics; sample 3 with pasteurized whey enriched with a bacterial concentrate containing 0.001 % acidophilus bacillus. The control sample were the recipe of fruit and jelly marmalade. A man obtained a juice concentrate by pressing using an enzyme preparations composition of cellulolytic and pectolytic action. The researchers used the vacuum evaporation method to concentrate the juice to a dry matter content of 52-55 %; prepared the marmalade mass under laboratory conditions using traditional technology with a change in prescription components: probiotic culture introduction at the stage of swollen pectin into the cooled syrup at a temperature below 45 °C. The authors used mathematical modeling of formulations in the technological process to establish the ingredients optimal ratios; identified the rational introduction methods of acidophilus bacillus depending on the organoleptic and rheological product properties after a five-fold measurements repeatability.

Exploring bacterial communities through metagenomics during bioremediation of polycyclic aromatic hydrocarbons from contaminated sediments

The goal of this study was to evaluate the degradation effectiveness of PAHs degrading bacteria at the mesocosm level, including Stenotrophomonas maltophilia (SC), mixed culture (MC), and enriched native microflora (EC) at the mesocosm level. Maximum degradation was found in the mesocosm MC (26.67 %), followed by SC (25.08 %) and EC (18.25 %) after 60 days. Thus, mixed culture and Stenotrophomonas maltophilia could be a game changer in the PAHs bioremediation at the chronically contaminated sites. MiSeq sequencing has revealed dominancy of γ-Proteobacteria, α-Proteobacteria, β-Proteobacteria at class level and Sphingomonadales, oceanospirillales, Rhodothermales at Order level. Families Alcanivoracaceae, Alteromonadaceae, Nocardiaceae, Rhodospirillaceae and genus Stenotrophomonas, Alcanivorax, Methylophaga, Fluviicola and Rhodoplanes were considerably increased which play key role in the PAHs degradation. Dominant bacterial communities have revealed resilience community to enable potential PAHs degradation process in all the mesocosms. To the best our knowledge this is the first ever attempt in PAHs biodegradation study conducted at the mesocosm level mimicking natural environmental conditions. Consequently, this study could be a benchmark against which future progress studies for the policy makers and stakeholders to design appropriate bioremediation study for the historically PAHs polluted contaminate sites.

Microflora of sputum and autopsy material of patients with COVID-19.

The rapid spread of a new coronavirus infection in the country actualizes the conduct of bacteriological studies of clinical material obtained from the respiratory tract of patients with COVID-19. During the experiments, 230 sputum samples and 260 autopsy lung samples from patients with COVID-19 were analyzed. 946 high-risk strains were isolated and identified by MALDI-ToF mass spectrometry on a Microflex LT instrument (Bruker®). According to the results of bacteriological cultures of sputum, a predominance of gram-positive ones was revealed, amounting to 50.5% (222 strains) of the total number of isolated pathogens. However, falling into this group is manifested by natural representatives of the microflora of the human mucous membranes from the genera Streptococcus, Rothia and Lactobacillus (109 strains in total), which can be manifested by the detection of improper sputum collection, causing contamination by the substance of intense salivation and nasopharyngeal discharge. In turn, the "classic" gram-positive causative agents of pneumonia were detected much less frequently: S. aureus in 5 cases, S. pneumoniae in 6 patients. The causative agents in the order Enterobacterales are represented by 42 strains, among which the most likely species are K.pneumoniae (27 strains). In the group of non-fermenting gram-negative bacteria, A. baumanii (29 strains) prevailed, and P. aeruginosa was also identified in 2 cases. When analyzing the results of a microbiological study of autopsy material (lungs) of patients with COVID-19, significant differences in the qualitative and quantitative composition of the microflora were revealed, compared with sputum. In the group of gram-positive bacteria, 15 strains of the natural microflora of the mucous membranes were identified, while sensitive species dominated among gram-negative pathogens: K. pneumoniae (102 strains), A. baumanii (75 strains), P. aeruginosa (11 strains). Regular microbiological monitoring is essential for antibiotic therapy and prevention of secondary bacterial infection. In the event of a fatal outcome, the results of microbiological analysis of autopsy material can determine the cause of death of the patient.

Enriched bacterial community efficiently degrade polycyclic aromatic hydrocarbons in soil ecosystem: Insights from a mesocosms study

The comprehensive study on PAHs bioremediation together with microbial communities and their functional potential analysis is limited. PAHs biodegradation through mesocosm studies using polluted sediment from Alang-Sosiya ship breaking yard was performed to compare the impact of 3 different bioremediation approaches (natural attenuation, combined treatment of bioaugmentation-biostimulation using enriched consortia and chemical fertilizers and combined treatment using enriched consortia and organic manures). The highest degradation of naphthalene, phenanthrene, fluoranthene, pyrene and total PAHs after 60d of incubation were 94.3%, 88.9%, 59.2%, 60.7% and 76.0%, respectively in bioaugmented-biostimulated mesocosms using eight consortia and chemical fertilizers. Microbial community structure analysis indicated that combined treatments of bioaugmentation-biostimulation were able to replace the native microflora with PAHs degraders. Proteobacteria and Firmicutes phyla were dominant in all mesocosms. Chelatococcus genus was absent as native microflora in natural attenuation treatment, which was dominant in bioaugmented-biostimulated mesocosms. The functional potential of microbial communities was estimated using the PICRUSt.

Effects of pulsed light and aerosolized formic acid treatments on inactivation of Salmonella enterica on cherry tomato, reduction of microbial loads, and preservation of fruit quality

Fresh produce remains the leading cause of foodborne illness outbreaks. Novel nonthermal technologies are needed to reduce the risk of pathogen contamination. The objective of this study was to develop a novel intervention technology exploiting integration of high intensity short time (10 s) pulsed light (PL) and aerosolized formic acid (AFA) for inactivation of Salmonella and maintenance of quality of cherry tomato. Smooth surface of tomatoes, inoculated with a cocktail containing three serotypes of Salmonella enterica, was treated with PL for 10 s followed by 2 min treatment with 1% AFA. Non-inoculated tomatoes were used to study the treatment effects on native microflora and quality. PL delivered significant inactivation at low doses. An optimal 10 s PL treatment equivalent to a dose of 10.5 J/cm2, provided 2.2 log CFU/g reduction while a 2 min exposure in 1% AFA antimicrobial yielded comparatively low, 1.7 log CFU/g reductions of Salmonella on tomato. The combination treatments of PL (10 s) followed by 1% AFA (2 min) provided additive inactivation yielding 4.2 log CFU/g reductions (P ≤ 0.05) of the pathogen. During cold storage (10 °C) the survivor population declined further providing 4.8 log CFU/g reductions on day 21. The combination PL-AFA treatment significantly reduced the native microbiota of tomato and also hindered their growth while in storage for three weeks. Mold and yeast (M&Y) spoilage organism populations declined to below the detection level. Furthermore, the quality factors as firmness and color of tomatoes were not significantly affected by the combination treatments. The treatment boosted the redness appearance of tomatoes indicating favorable consumer acceptability. Overall, our results demonstrate that combination of PL and AFA treatment could potentially be used as a novel approach to enhance microbial safety and quality of tomatoes.

High-throughput coating with biodegradable antimicrobial pullulan fibres extends shelf life and reduces weight loss in an avocado model.

Food waste and food safety motivate the need for improved food packaging solutions. However, current films/coatings addressing these issues are often limited by inefficient release dynamics that require large quantities of active ingredients. Here we developed antimicrobial pullulan fibre (APF)-based packaging that is biodegradable and capable of wrapping food substrates, increasing their longevity and enhancing their safety. APFs were spun using a high-throughput system, termed focused rotary jet spinning, with water as the only solvent, allowing the incorporation of naturally derived antimicrobial agents. Using avocados as a representative example, we demonstrate that APF-coated samples had their shelf life extended by inhibited proliferation of natural microflora, and lost less weight than uncoated control samples. This work offers a promising technique to produce scalable, low-cost and environmentally friendly biodegradable antimicrobial packaging systems.

The effect of crisping, misting, and storage temperature on the survival or growth of Listeria monocytogenes and natural psychrotrophic bacteria on romaine lettuce.

L. monocytogenes has been linked to fresh produce and detected in the retail environment. This study simulated the retail practices (crisping, misting, and storage) of unbagged whole heads of romaine lettuce to determine the growth of L. monocytogenes and natural psychrotrophic microflora. Three nalidixic acid-resistant strains of L. monocytogenes strains were inoculated to each head of lettuce (≈5 log10 CFU/g). For crisping, 24 heads of romaine lettuce were immersed in tap water or electrolyzed water (EW; free chlorine: 55 ppm) for 5 min, followed by holding at 5 °C for 2 h. The water-crisped (WC), EW crisped (EWC), or non-crisped (NC) lettuces were placed in a commercial refrigerated cabinet for misting at 5 °C. After 24-h misting, heads of lettuce were placed in perforated drain boxes with cover at 5 °C or 15 °C. The tap water and EW crisping achieved 1.3 and 2.9 log10 CFU/g reduction of L. monocytogenes, respectively. Approximately 1 log additional reduction of L. monocytogenes in the non-crisped lettuce was shown after misting (p < 0.05), but no significant effect of misting on the population of L. monocytogenes was observed on WC or EWC lettuces (p > 0.05). Regardless of the storage temperature or misting, L. monocytogenes populations remained significantly (p < 0.05) lower on EWC lettuce than NC and WC lettuce. On days 4 and 7 of storage, the natural psychrotrophic bacteria on lettuce stored at 5 °C was significantly lower than stored at 15 °C, and its population was not affected by crisping and misting. These provide insight into the influence of retail lettuce handling practices on the risk of L. monocytogenes.

The Role of the Bacteroides spp. in Bacteraemia

Abstract Anaerobic bacteraemia is not frequent (1.2–13.7%), but is associated with a high mortality rate of 16–27%. Anaerobic infections including bacteraemia nearly always arise from contamination by endogenous bacteria into contiguous or other sites like gastrointestinal tracts, genito-urinary tracts, abscesses etc. Factors leading to anaerobic bacteraemia are mainly surgical procedures, crush injuries, the presence of foreign bodies, tissue necrosis, tumours, diabetes. The most common infectious anaerobic agents are Gram-negative bacilli belonging to the Bacteroides/Parabacteroides, which under normal conditions constitute the natural human microflora. An important factor in the virulency of B. fragilis is the ability to form abscesses; a limited infection may progress to bacteraemia and then systemic inflammatory response syndrome and sepsis. Anaerobic bacteraemia mainly affects adults, with elderly patients over 65 years with underlying diseases. The importance of anaerobic bacteria in neonatal bacteraemia and sepsis is a relatively new phenomenon. In contrast the prevalence of anaerobes in bloodstream infections in children is extremely rare with children between 2 and 6 years of age having the least risk ranging 0–0.5% overall. The incidence of recovery of anaerobes in neonatal bacteraemia varies between 1.8% and 12.5%. The majority of cases reported in the literature were due to Bacteroides spp. (41%) other cultured anaerobes belonged to Clostridium spp. (32%), Peptostreptococcus spp. (20%). Blood cultures remain the gold standard for detection of the etiologic both anaerobes and aerobes agent of bloodstream infection. In recent years significant progress has been made in the methods used in the diagnosis of anaerobes, which significantly reduced the time and cost of the examination. Currently, the mass spectometry MALDI-TOF MS and 16S rRNA sequencing are increasingly used for anaerobic bacteria identification. In 2022, EUCAST published standardized disk diffusion method for the drug susceptibility testing of Bacteroides spp. and other 4 clinically significant anaerobes. Determining the sensitivity of anaerobes to antibiotics is important due to the increasing drug resistance in this group. Number of B. fragilis strains resistant to clindamycin and moxifloxacin is increasing. According to the published studies sensitivity to clindamycin and moxifloxacin is significantly rare and occurs in 64% and 68% of isolates and in 50.8% and 58.2% respectively. Carbapenems and metronidazole continue to be the most effective active antibiotics to be used in the empirical therapy of anaerobic bacteraemia. There are case reports of infections caused by multidrug-resistant strains of Bacteroides spp, meaning resistant to at least three antibiotics from different groups. Rapid microbial diagnosis, targeted therapy and surgical treatment of a possible source of infection are crucial in treatment of sepsis caused by anaerobic bacteria.