Viable Bacterial Counts Research Articles

Potential effect of topical antibiotics administration in the oral cavity on the reduced number of bacteria entering the lower respiratory tract after oral cancer surgery

Background/purposeOne of the causes of ventilator-associated pneumonia (VAP) is aspiration of oropharyngeal fluid containing pathogenic microorganisms into the lower respiratory tract. In this study, we aimed to investigate whether antibiotic ointment applied to the oral cavity can reduce the number of bacteria in the fluid on the cuff of a tracheal cannula. Materials and methodsTetracycline ointment was applied intraorally once to a patient under endotracheal intubation by postoperative tracheostomy for oral cancer. The tetracycline concentrations in the oropharyngeal fluid and fluid on the cuff of tracheal cannula were determined by bioassay, and the total viable bacterial count was determined by delayed real-time polymerase chain reaction developed by the authors from before to 6 h after application. ResultsA total of seven patients were enrolled. Very high antibiotic concentrations were maintained, ranging from 481 μg/ml to 2060 μg/ml in oropharyngeal fluid and from 267 μg/ml to 858 μg/ml in fluid on the cuff from 1 h to 6 h after application. Compared to the pre-application results, the inhibition rates of viable bacteria were 80.0–97.7% for oropharyngeal fluid and 47.6%–91.9% for fluid on the cuff at 1–6 h after application, indicating that antibiotic ointment can inhibit bacteria entering the lower respiratory tract for a long period of time in intubated patients. ConclusionOral application of antibiotic ointment reduced the number of bacteria entering the lower respiratory tract, suggesting that it may be useful in the prevention or treatment of VAP.

Use of a peracetic acid (PAA) disinfectant to reduce total viable bacteria count in hospital wastewater drains

The periphery of the hospital water system interfaces at multiple points with patients and staff in clinical areas. This comprises mostly sinks and showers and presents a significant infection control risk. Wastewater drains in particular act as a reservoir of pathogens that can be transmitted to patients. Numerous strategies have been investigated as potential methods to reduce biofilm and bacterial load including regular application of biocidal chemicals. Traditional methods of assessing the efficacy of such products relies on culture-based microbiological techniques, usually targeting a limited range of key pathogens. We assessed the efficacy of a peracetic acid containing drain disinfectant product on seven clinical handwash basin drains, taking daily samples over six weeks (before, during and after use of the drain disinfectant product). We used a rapid, culture-independent estimation of total bacterial viable count (TVC) to assess efficacy. We applied long-read metagenomic sequencing to study the entire drain microbiome, which allowed taxonomic changes to be documented following use of the drain disinfectant product. All samples were found to be heavily contaminated, however the drain disinfectant product reduced the TVC from an estimated mean of 4228cfu/mL to 2874cfu/mL. This reduction was sustained in the two weeks following cessation of the product. Long-read metagenomic sequencing showed a microbiome dominated with Gram-negative organisms, with some taxonomic shifts in samples before and after application of the drain disinfectant. The impact on hospital-acquired infections from reducing bioburden in hospital drains by approximately a third, along with any associated changes in bacterial composition, needs evaluation in future studies.

Bioactive compounds, volatile compounds, rheological properties and bacteriostatic activities of fig juices with oligosaccharides supplementation fermented by Lactiplantibacillus plantarum

The objective of this study was to investigate the effects of Lactiplantibacillus plantarum fermentation on the bioactive compounds, volatile compounds, rheological properties and bacteriostatic activities of fig juices supplemented with oligosaccharides, namely fructooligosaccharides (FOS), galactooligosaccharides (GOS), isomaltooligosaccharides (IMO), xylooligosaccharides (XOS), stachyose (SOE) and mannanoligosaccharides (MOS). Results showed that SOE, FOS and IMO supplementations stimulated the proliferation of Lactiplantibacillus plantarum, especially for SOE, exhibiting the highest viable bacterial counts (9.84 log CFU/mL). Oligosaccharides supplementation accelerated the conversion of carbohydrates to organic acids, and increased the total contents of flavonoid (TFC) and carotenoid (TCC) during fermentation, of which FOS exhibited the greatest increases in TFC (66.28 mg RE/L) and TCC (0.032 mg/L). Furthermore, the highest levels of DPPH RSA (65.88%) and ABTS RSA (66.24%) were found in fermented fig juice supplemented with MOS, while the highest level of FRAP (0.97 mmol Trolox/L) and protocatechuic acid (6.97 mg/L) was observed in that with GOS. The total contents of alcohols and esters were significantly increased, while aldehyde content was decreased by oligosaccharides supplementation. In addition, oligosaccharides supplementation decreased the apparent viscosity of fermented juices. Fermented juices supplemented with FOS exhibited dramatically effective inhibition against Escherichia coli, Staphylococcus aureus and Listeria monocytogenes, due to the ruptures of cell surfaces and collapse of cellular structure. According to Pearson's correlation analysis, protocatechuic acid content was significantly and positively correlated with bacteriostatic activities. It was suggested that FOS should be a better probiotic additive for the preparation of fermented fig juice.

Can antimicrobial photodynamic therapy serve as an effective adjunct protocol for disinfecting the necrotic root canal system? A randomized controlled study

BackgroundBacterial infection plays an important role in persistent periapical lesions and inadequate disinfection of root canals is considered the biggest factor responsible for endodontic treatment failure. Antimicrobial Photodynamic Therapy (aPDT) has become the latest choice to eradicate microorganisms in root canals.ObjectiveThis study aims to evaluate the effectiveness of Antimicrobial Photodynamic Therapy (aPDT) in bacterial count reduction compared to Passive Ultrasonic Activation (PUI) and Ca(OH)2 dressings.Materials and methodsForty-five anterior single canal teeth with medium-sized periapical lesions (2–5 mm) were divided into three groups according to the disinfecting technique (each group consists of 15 canals with 1:1:1 allocation ratio): Group A: Ca(OH)2 dressing. Group B: Passive Ultrasonic Activation (PUI). Group C: Antimicrobial Photodynamic Therapy (aPDT). Direct bacterial viable count method was used to count the colonies forming units (CFU) before and after the disinfecting and the bacterial count reduction was estimated, the statistical analysis was performed at a 95% confidence level using the Chi-square and Mann–Whitney U test.ResultsaPDT showed no statistically significant difference when compared to passive ultrasonic irrigation (P > 0.05) but showed higher and more promising results when compared to Ca(OH)2 dressings (P < 0.05).ConclusionsaPDT has the ability and effectiveness as a disinfecting technique in necrotic and infected root canals.Clinical significance of the studyThe results of this clinical trial provide that aPDT can be considered an adjunct method for root canal disinfection with the same effectiveness as passive ultrasonic irrigation.

Critical Involvement of the Thioredoxin Reductase Gene (trxB) in Salmonella Gallinarum-Induced Systemic Infection in Chickens.

Salmonella enterica serovar Gallinarum biovar Gallinarum (SG) causes fowl typhoid, a notifiable infectious disease in poultry. However, the pathogenic mechanism of SG-induced systemic infection in chickens remains unclear. Thioredoxin reductase (TrxB) is a redox protein crucial for regulating various enzyme activities in Salmonella serovar, but the role in SG-induced chicken systemic infection has yet to be determined. Here, we constructed a mutant SG strain lacking the trxB gene (trxB::Cm) and used chicken embryo inoculation and chicken oral infection to investigate the role of trxB gene in the pathogenicity of SG. Our results showed that trxB::Cm exhibited no apparent differences in colony morphology and growth conditions but exhibited reduced tolerance to H2O2 and increased resistance to bile acids. In the chicken embryo inoculation model, there was no significant difference in the pathogenicity of trxB::Cm and wild-type (WT) strains. In the chicken oral infection, the WT-infected group exhibited typical clinical symptoms of fowl typhoid, with complete mortality between days 6 and 9 post infection. In contrast, the trxB::Cm group showed a 100% survival rate, with no apparent clinical symptoms or pathological changes observed. The viable bacterial counts in the liver and spleen of the trxB::Cm-infected group were significantly reduced, accompanied by decreased expression of cytokines and chemokines (IL-1β, IL-6, IL-12, CXCLi1, TNF-α, and IFN-γ), which were significantly lower than those in the WT group. These results show that the pathogenicity of the trxB-deficient strain was significantly attenuated, indicating that the trxB gene is a crucial virulence factor in SG-induced systemic infection in chickens, suggesting that trxB may become a potentially effective target for controlling and preventing SG infection in chickens.

The Passive Environmental Effect of the Fungicide Benomyl on Soil Promoting Bacteria and Concentration of Some Important Soil Elements

Loam examples were gathered through the 2020-2021 rising periods, and the following measurements were made: Viable bacterial count by reducing root colonization. The outcomes of reviewing the impact of the fungicide Benomyl on development and viable microflora count revealed that the highest microbial count was in Al-Madaein 80 ×103 CFU/mL was recorded ., and the lowest count was 60 ×103 CFU/mL for the Aushtar area, The microbial viable count values for the affected microorganisms with Benomyl were decrease to 27×103 and 65 × 103 CFU/mL respectively. Those consequences specify that Benomyl has a robust choosiness contrary to microflora, especially when compared to the benomyl effect as folded dose, the microflora l count decreases to 25 ×103 CFU /mL in the Aushtar area and increases to 60 ×103 CFU/mL in Al-Madaein area. Whereas the study estimated the level of eight elements in soil (Mn, Fe, Cu, Zn, NO3, P, K, and NH4) cultured with Cyperus rotundus L. Which mentioned the effect of benomyl on these levels after three days of treatment. Mn concentration ranged between 5.96 to 9.11 ppm, while after fungicide benomyl, it decreased to 5.63 -6.53 ppm similar results were observed for other elements. The highest affected element was Mn in the Aushtar area. Those consequences designate that Benomyl has a stout fussiness in contrast to soil nutrients. The greatness of benomyl impacts on loam ingredients and procedures were minor, qualified to impact on mycorrhizal root foundation (reduction through benomyl).

Impact of Airborne Exposure to PM10 Increases Susceptibility to P. aeruginosa Infection.

The effects of exposure to airborne particulate matter with a size of 10 μm or less (PM10) on C57BL/6 mouse corneas, their response to Pseudomonas aeruginosa (PA) infection, and the protective effects of SKQ1 were determined. C57BL/6 mouse corneas receiving PBS or SKQ1 were exposed to control (air) or PM10 for 2 weeks, infected, and the disease was documented by clinical score, PMN quantitation, bacterial plate count, RT-PCR and Western blot. PBS-treated, PM10-exposed corneas did not differ at 1 day postinfection (dpi), but exhibited earlier (3 dpi) corneal thinning compared to controls. By 3 dpi, PM10 significantly increased corneal mRNA levels of several pro-inflammatory cytokines, but decreased IL-10, NQO1, GR1, GPX4, and Nrf2 over control. SKQ1 reversed these effects and Western blot selectively confirmed the RT-PCR results. PM10 resulted in higher viable bacterial plate counts at 1 and 3 dpi, but SKQ1 reduced them at 3 dpi. PM10 significantly increased MPO in the cornea at 3 dpi and was reduced by SKQ1. SKQ1, used as an adjunctive treatment to moxifloxacin, was not significantly different from moxifloxacin alone. Exposure to PM10 increased the susceptibility of C57BL/6 to PA infection; SKQ1 significantly reversed these effects, but was not effective as an adjunctive treatment.

Studying the viability and growth kinetics of vancomycin-resistant Enterococcus faecalis V583 following femtosecond laser irradiation (420–465 nm)

Enterococcus faecalis is among the most resistant bacteria found in infected root canals. The demand for cutting-edge disinfection methods has rekindled research on photoinactivation with visible light. This study investigated the bactericidal activity of femtosecond laser irradiation against vancomycin-resistant Enterococcus faecalis V583 (VRE). The effect of parameters such as wavelength and energy density on the viability and growth kinetics of VRE was studied to design an optimized laser-based antimicrobial photoinactivation approach without any prior addition of exogenous photosensitizers. The most effective wavelengths were 430 nm and 435 nm at a fluence of 1000 J/cm2, causing a nearly 2-log reduction (98.6% and 98.3% inhibition, respectively) in viable bacterial counts. The colony-forming units and growth rate of the laser-treated cultures were progressively decreased as energy density or light dose increased at 445 nm but reached a limit at 1250 J/cm2. At a higher fluence of 2000 J/cm2, the efficacy was reduced due to a photobleaching phenomenon. Our results highlight the importance of optimizing laser exposure parameters, such as wavelength and fluence, in bacterial photoinactivation experiments. To our knowledge, this is the first study to report an optimized wavelength for the inactivation of VRE using visible femtosecond laser light.

Physicochemical, microbiological and sensory characterization of yogurt fermented by Weissella confusa SW1 and traditional starters

Starter cultures play important roles in the quality and functional activity of yogurt. In this study, a novel strain Weissella confusa SW1 was isolated from naturally fermented milk. The potential application of this strain in yogurt preparation was investigated and the unique qualities it conferred on yogurt was characterized. W. confusa SW1 could efficiently metabolize lactose and galactose, and the whole-genome sequencing showed that it has a complete Leloir metabolic pathway. Besides, W. confusa SW1 had strong antioxidant capacity, and could significantly promote the growth of Streptococcus thermophilus. Subsequently, W. confusa SW1 was co-cultured with traditional starters (Lb. bulgaricus and S. thermophilus) to prepare yogurt. The results showed that the scavenging rates of DPPH and ABTS radicals of W. confusa SW1 fermented yogurt increased from 79.51% to 85.19% and 80.14%–85.47%, respectively. Meanwhile, the viable bacterial counts of Lb. bulgaricus and S. thermophilus were increased in yogurt when co-cultured with W. confusa SW1. Furthermore, the addition of W. confusa SW1 reduced the curd time and improved the water holding capacity of yogurt. Thus, this study laid a theoretical foundation for the development of functional yogurt with the application of W. confusa SW1.

Assessment of the Microbial and Physicochemical Quality of Water: Evidence from Selected Groundwater Sources from The Coastal Region of Ondo State, Nigeria

The coastal area of Nigeria frequently experiences pollution of water due to various human activities that may compromise the quality of underground water. This study evaluated the microbial contamination and quality indicators of groundwater in the coastal environment of Ondo State, Nigeria. Nine underground water samples were collected from the study area and assayed using conventional microbiological techniques coupled with standard physical and chemical analytical procedures. Results revealed that all the samples had total viable bacterial counts, fungal counts and coliform counts which ranged from 61.25 to 85.32 CFU/100 mL, 10.00 to 35.32 SFU/100 mL and 6 – 24 MPN/100 mL respectively, which were higher than the set WHO limit. Results also revealed that the samples from Irele and Ese- Odo Local Governments Areas had acidic pH in the range of 4.20 -5.21 considered to be below the WHO permissible limit whereas only one of three samples from Ilaje Local Government had acidic pH of 5.23. The concentrations of the heavy metals varied among the samples with manganese (0.183-0.311) mg/L exceeding the 0.08 mg/L prescribed by the WHO. The high microbial load, acidic pH of 4.20 -5.23 in 77.78 % of samples and elevated amount of certain metals suggest the need for water quality monitoring and intervention by government and oil multinationals operating in the area noting that adequate supply of safe - drinking water will improve human health and reduce the burden of waterborne diseases.

Eugenol-infused alginate nanoemulsion: A fluorescent label for direct food shelf-life extension and non-contact detection of food spoilage through biogenic amine sensing

The implementation plan of extending the shelf life of food while ensuring food safety is playing an increasingly important role in promoting global solutions to food waste. Here, we have logically created a new eugenol nanoemulsion to sense spoilage and extend the shelf life. The nano lotion (Eu/SA) was loaded with sodium alginate nanoparticles as carrier, eugenol as antibacterial agent and antioxidant. Fluorescein isothiocyanate (FITC) was utilized concurrently as an indicator by simply mixed with Eu/SA nanoemulsion, then physically deposited on a commercial filter membrane to create smart fluorescent labels. Shrimp with and without the Eu/SA nanoemulsion coating had their freshness monitored using a non-contact tagging technique. And through smartphone integrated with RGB (red/green/blue) analysis for digitization, it was found that the RGB of uncoated shrimp was greater than that of treated shrimp. Additionally, without coating treatment, thiobarbituric acid (TBA), pH and viable bacterial count (TVC) of Shrimp all exceed the established. Eu/SA nanoemulsion offers a more appealing monitoring and preservation integration platform for the food safety industry.

Investigation of the effect of electric field on bacteria isolated from skin infection

Abstract. Al-Salami RB, Mukhaifi EA, Al-Tamimi WH. 2024. Investigation of the effect of electric field on bacteria isolated from skin infection. Biodiversitas 25: 1320-1328. Nineteen bacterial isolates were obtained from twenty-six samples obtained from various patients with skin infections in the current study. These bacteria were identified by a genetic method depending on 16S rRNA and the molecular identification of cna and fnbA genes of Staphylococcus aureus isolates were detected, and an antimicrobial electric field was applied using various voltages and durations to target both Gram-positive and Gram-negative bacteria. The results showed that Staphylococcus sp. was the most dominant genera, followed its Acinatobacter sp. The high frequent species was Staphylococcus aureus (24%) followed by Staphylococcus epidermidis (21%), Staphylococcus epidermidis and Staphylococcus argenteus (10.5%), Staphylococcus haemolyticus, Acinetobacter baumannii and Acinetobacter variabilis (5.2%). Eleven new strains were identified and recorded in GenBank. A phylogenetic tree was also constructed based on 16S rRNA gene sequences of isolates to evaluate their close relationship and evolution between them. The bands of each amplified cna and fnbA gene were described at 192 bp and 191 bp respectively. The effect of the antimicrobial electric field showed an extremely high and significant decrease of the viable bacterial count of S. haemolyticus and A. baumannii after the exposure to an electric field of (1-5) V for 15 min, where the viable count of bacteria reduced sharply with percentage bacterial death (19-95%) and (16-100%), respectively, and from (66-100%) and (52-100%) after 30 min, respectively.

Changes in the Quality and Microflora of Yellowtail Seriola quinqueradiata Muscles during Cold Storage.

We evaluated the changes in the quality and microflora of yellowtail flesh cold-stored until spoilage. Based on the sensory evaluation, odor palatability was deemed unacceptable for dark muscle (DM) and the dorsal part of the ordinary muscle (OD) after >10 days and 14 of storage, respectively. Log 7 CFU/g in DM as well as OD was obtained on days 10 (Aeromonas spp.) and 14 (Enterobacteriaceae and Pseudomonas spp.) of storage, whereas log 5 (Brocothrix thermosphacta) and 6 (H2S-producing bacteria) CFU/g in them were obtained on day 14 of storage. In these bacteria, the viable bacterial counts of Pseudomonas spp. and Aeromonas spp. in DM were significantly higher than those in OD only at some storage times. Amplicon sequencing revealed that in both muscles, Pseudomonas became predominant after storage, with greater than 90% recorded after more than 10 days of storage. The relative abundances of Acinetobacter, Unclassified Gammaproteobacter, and Shewanella were relatively high in both muscles after more than 10 days of storage; however, these values were less than 5%. Ethyl butyrate in the OD and DM and 2,3-butanedione in the OD were first detected on days 14 and 10 of storage, respectively. Acetoin in the OD increased by 81-fold after 14 days of storage and was significantly increased in the DM after more than 10 days compared with the amount detected pre-storage. Volatiles, such as (E)-2-pentenal in the OD and 1-pentanol in the DM, decreased and increased linearly, respectively, throughout the 14-day storage period. Altogether, these volatile components may cause quality deterioration due to spoilage and/or lipid oxidation during cold storage of the OD and DM.

A STUDY OF MICROBIAL CONTAMINATION IN PUNARNAVA MANDURA

Introduction: Herbal medicines are being used extensively in many countries to treat many diseases, as seen in the COVID-19 pandemic, so the global market for herbal medicines has grown suddenly. In India, under the Ayurveda system of medicine, apart from plants, animal and mineral products have also been used as medicine since long ago. Both herbal and animal products contain primarily organic components; therefore, like food in-gredients (biological ingredients), herbal medicine and animal products are at risk of microbial growth and con-tamination. Punarnava Mandura is a popular Ayurvedic medicine described in various classical and authoritative texts of Ayurveda. It is a perfect example of a medicine made from substances derived from plants, minerals, and animals. It contains Mandura Bhasma as a mineral component apart from other herbal ingredients, while cow urine (Gomutra) is of animal origin. It is widely used in infectious and non-infectious fever, cold, indigestion, and other diseases of the Gastrointestinal tract. Microbial contamination of medicines is defined as the unintend-ed habitation of pathogenic microbes that cause their degradation. In pharmaceutics, various factors may be a source of microbes, including the ingredients of drugs, manpower, machines, and the environment of the phar-macy. Microbial contamination is a pertinent issue and essential in quality control steps in pharmaceutical man-ufacturing and food processing. Microbial contamination of medicines and food products may also affect human health. Objective: The primary aim and purpose of the present study was to determine the microbial contamina-tion of an Ayurvedic Herbo-mineral drug sample of Punarnava Mandura. Material and methods: The drug sam-ple (Self-made) was made in the institute pharmacy. Another drug sample (market sample) of Punarnava Man-dura of a pharmacy was also kept as a control to compare the results. Quantitative and qualitative assessment of microbial loads in Punarnava Mandura was assessed. The following strains of microbes: E. Coli, Salmonella spp., Staphylococcus aureus, Fungus, and Total viable aerobic bacterial count were evaluated. Results: Both the samples of Punarnava Mandura have shown an insignificant load of selected microbes.

LC-MS/MS determination of pyocyanin-N-acetyl cysteine adduct: application for understanding Pseudomonas aeruginosa virulence factor neutralization.

Combating Pseudomonas aeruginosa infection is challenging. It secretes pyocyanin (PCN) pigment that contributes to its virulence. Neutralizing PCN via reaction with thiol-containing compounds may represent a potential therapeutic option. This study investigates the neutralization reaction between PCN and N-acetyl cysteine (NAC) for bacterial inhibition and explores its mechanism of action. The neutralization adduct (PCN-NAC) was synthesized by reacting the purified PCN and NAC. The adduct was analyzed and its structure was elucidated. LC-MS/MS method was developed for the determination of PCN-NAC in P. aeruginosa cultures post-treatment with NAC (0-5 mg/mL). The corresponding anti-bacterial potential was estimated and compared to nanoparticles (NPs) alone and under stress conditions. In silico studies were performed to support explaining the mechanism of action. Results revealed that PCN-NAC was exclusively detected in NAC-treated cultures in a concentration-dependent manner. PCN-NAC concentration (230-915 µg/mL) was directly proportional to the reduction in the bacterial viable count (28.3% ± 7.1-87.5% ± 5.9) and outperformed all tested NPs, where chitosan NPs induced 56.9% ± 7.9 inhibition, followed by zinc NPs (49.4% ± 0.9) and gold NPs (17.8% ± 7.5) even post-exposure to different stress conditions. A concomitant reduction in PCN concentration was detected. In silico studies revealed possible interactions between key bacterial proteins and PCN-NAC rather than the NAC itself. These results pose NAC as a potential choice for the management of P. aeruginosa infection, where it neutralizes PCN via the formation of PCN-NAC adduct.

Evaluation of Antibiotic Penicillin G Activities Based on Electrochemical Measurement of a Tetrazolium Salt.

This study focused on the electrochemical properties of tetrazolium salts to develop a simple method for evaluating viable bacterial counts, which are indicators of drug susceptibility. Considering that the oxidized form of tetrazolium, which has excellent cell membrane permeability, changes to the insoluble reduced form formazan inside the cell, the number of viable cells was estimated based on the reduction current of the tetrazolium remaining in the bacterial suspension. Dissolved oxygen is an important component of bacterial activity. However, it interferes with the electrochemical response of tetrazolium. We estimated the number of viable bacteria in the suspension based on potential-selective current responses that were not affected by dissolved oxygen. Based on solubility, cell membrane permeability, and characteristic electrochemical properties of the tetrazolium salt 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium, we developed a method for rapidly measuring viable bacteria within one-fifth of the time required by conventional colorimetric methods for drug susceptibility testing.

Nutrient enrichment increases virulence in an opportunistic environmental pathogen, with greater effect at low bacterial doses.

Eutrophication of aquatic ecosystems is associated with an increased risk of pathogen infection via increased pathogen growth and host exposure via increased pathogen doses. Here, we studied the effect of nutrients on the virulence of an opportunistic bacterial pathogen of fish, Flavobacterium columnare, in challenge experiments with rainbow trout fingerlings. We hypothesized that removing all nutrients by washing the bacteria would reduce virulence as compared to unwashed bacteria, but adding nutrients to the tank water would increase the virulence of the bacterium. Nutrient addition and increase in bacterial dose increased virulence for both unwashed and washed bacteria. For unwashed bacteria, the addition of nutrients reduced the survival probability of fish challenged with low bacterial doses more than for fish challenged with higher bacterial doses, suggesting activation of bacterial virulence factors. Washing and centrifugation reduced viable bacterial counts, and the addition of washed bacteria alone did not lead to fish mortality. However, a small addition of nutrient medium, 0.05% of the total water volume, added separately to the fish container, restored the virulence of the washed bacteria. Our results show that human-induced eutrophication could trigger epidemics of aquatic pathogens at the limits of their survival and affect their ecology and evolution by altering the dynamics between strains that differ in their growth characteristics.

Biodegradation potentials of edaphic bacterial isolates cultured on Haloxyfop R Methyl ester herbicide-mineral salt medium

The heterotrophic and haloxyfop-R methyl ester utilizing bacterial counts associated with top soil samples was evaluated. Three (3) bacterial isolates; Bacillus sp., Micrococcus sp. and Staphylococcus sp. were cultured and screened for their ability to utilize haloxyfop-R methyl ester as sole source of carbon and energy using the turbidimeteric procedure. The growth profiles of two axenic cultures; Bacillus sp. and Micrococcus sp. were determined using the shake flask test. Parameters which included pH, mean viable bacterial counts, optical density and dissolved CO2 were determined during growth profiling using relevant procedures and equipment. The pH of the soil samples was 5.08 ± 0.02 for sample A and 4.62 ± 0.02 for sample B. The total heterotrophic bacterial count was 2.8 × 104 cfu/g ± 849 for A and 4.62 × 104 cfu/g ± 989 for B. The mean dissolved CO2 data for Micrococcus sp. during the growth profile study ranged from 1.1 mg/l ± 0.1 to 6.8 mg/l ± 0.2. Axenic Micrococcus sp. was the most effective amongst the growth profile cultures in mineralizing the herbicide content of the culture medium.

Enhancing the activity of β-lactamase inhibitory protein-II with cell-penetrating peptide against KPC-2-carrying Klebsiella pneumoniae.

Carbapenem-resistant Enterobacterales (CRE) is considered a paramount threat due to its rapid spread and high mortality rate. Klebsiella pneumoniae carbapenemases (KPCs), specifically KPC-2, are prevalent enzymes responsible for carbapenem resistance in many countries. While combinations of antibiotics are commonly used, they must be tailored to match the remaining susceptibility of the infecting strains. Therefore, there is a need to develop the β-lactamase inhibitor to effectively address this issue. β-lactamase inhibitor protein (BLIP) and its variants, BLIP-I and BLIP-II, have demonstrated the ability to inhibit class A β-lactamases. In particular, BLIP-II shows strong binding to the KPC-2 carbapenemase, making it a potential candidate for inhibition. To improve the intracellular penetration of BLIP-II, a cell-penetrating peptide (CPP) was employed. In this study, a KRK-rich peptide was introduced at either the N-terminal or C-terminal region of tBLIP-II, excluding the signal sequence of the BLIP-II protein. tBLIP-II, tBLIP-II-CPP, and CPP-BLIP-II were successfully expressed, and the chimeric proteins retained inhibitory activity compared to tBLIP-II alone. It is apparent that homology modeling demonstrated neither the poly-histidine tag nor the CPP interfered with the essential interaction residues of tBLIP-II. Interestingly, BLIP-II-CPP exhibited the highest inhibitory activity, reducing the minimal inhibitory concentration (MIC) of meropenem by 8 folds. Moreover, the combination of tBLIP-CPP with meropenem significantly decreased the viable bacterial cell count compared to the combination of tBLIP-II with meropenem or meropenem alone. These findings suggest that tBLIP-CPP is a promising candidate for restoring carbapenem susceptibility against CRE and provides a valuable therapeutic option for infections caused by CRE.

Effects of pretreated garlic on bacterial composition and metabolite profiles during kimchi fermentation

This study investigated the effects of pretreated garlic on the fermentation characteristics of kimchi; four types of kimchi using pretreated garlic [raw (RGK), frozen (FGK), blanched (BGK), and blanched-frozen (BFGK)] were prepared; fermentation was carried out at 4 °C for 6 weeks. The fermentation properties, microbial community composition, metabolic compounds, and volatile organic compounds (VOC) were investigated. The total viable bacterial count in blanched garlic was reduced significantly compared to those in raw and frozen garlic. Latilactobacillus spp. became the dominant species in all kimchi samples as the fermentation progressed. Of the 145 metabolites observed by gas chromatography and mass spectrometry, 51 volatile metabolites were observed. Glucose, fructose, sucrose, lactic acid, citric acid, and mannitol were present as major metabolites (variable importance in projection scores >1.0). Frozen garlic (FGK and BFGK) reduced the production of sulfuric VOC compounds, while raw garlic increased the production of these compounds, specifically that of allyl methyl sulfide, dimethyl disulfide, and dimethyl trisulfide. In conclusion, the condition of garlic added to kimchi affects the abundance of microorganisms during initial fermentation and the quality characteristics of kimchi during the fermentation period. These results help establish garlic pretreatment conditions for kimchi manufacturing.