The research carried out so far for phage-antibiotic synergy (PAS) differs as regards the technique of modifying the double-layer agar (DLA) method to show the PAS effect on Petri plates, which may contribute to non-uniform research results. Therefore, there is a need to unify the method to effectively detect the PAS effect, at its most basic in vitro test. In this study, bacteriophage T4₅ and 43 antibiotics belonging to different antibiotic classes were used. Seven different DLA method modifications were tested, in terms of antibiotic addition placement and presence or absence of the base agar. The overall number of phage plaques per plate mainly depended on the antibiotic used. Differences in plaque quantity depended on the type of the DLA method modification. The largest total number of plaques was obtained by the addition of an antibiotic to a bottom agar with the presence of a top agar. This indicates that even though an antibiotic could manifest the PAS effect by a standard disk method, it would be worth examining if the effect is equally satisfactory when applying antibiotics directly into the agar, with regards to using the same bacteriophage and bacterial host.

The ambiguous nature of pyocyanin was noted quite early after its discovery. This substance is a recognized Pseudomonas aeruginosa virulence factor that causes problems in cystic fibrosis, wound healing, and microbiologically induced corrosion. However, it can also be a potent chemical with potential use in a wide variety of technologies and applications, e.g. green energy production in microbial fuel cells, biocontrol in agriculture, therapy in medicine, or environmental protection. In this mini-review, we shortly describe the properties of pyocyanin, its role in the physiology of Pseudomonas and show the ever-growing interest in it. We also summarize the possible ways of modulating pyocyanin production. We underline different approaches of the researchers that aim either at lowering or increasing pyocyanin production by using different culturing methods, chemical additives, physical factors (e.g. electromagnetic field), or genetic engineering techniques. The review aims to present the ambiguous character of pyocyanin, underline its potential, and signalize the possible further research directions.

Incorporating zinc oxide nanoparticles (ZnO NPs) into cement mortars may provide additional functions, e.g., self-cleaning and antibacterial or electroconductive ability. However, these NPs are also known for their potential toxicity. During the life cycle of a cement mortar, various abrasive forces cause the release of admixtures to the natural environment. The effect of the released NPs on model microorganisms has not been extensively studied. Previous studies have shown that nanomaterials may affect various microorganisms’ physiological responses, including changes in metabolic activity, biofilming, or growth rate. In this study, we have focused on evaluating the response of model microorganisms, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Candida albicans, towards ZnO nanoparticles released from cement mortars in different deterioration scenarios. The addition of ZnO nanoparticles to cement mortars had a noticeable effect on impeding the strength development. We have also detected that depending on the deterioration scenario, the release of ZnO nanoparticles was varied. Our studies have also shown that even though the release of nanoform ZnO could be limited by poor dispersion or the used filtration technique, the eluates have caused slight but statistically significant changes in the physiological features of studied microorganisms showing relatively low toxicity.

Here, we designed paper sheets coated with chitosan, bacterial cellulose (nanofibers), and ZnO with boosted antibacterial and mechanical activity. We investigated the compositions, with ZnO exhibiting two different sizes/shapes: (1) rods and (2) irregular sphere-like particles. The proposed processing of bacterial cellulose resulted in the formation of nanofibers. Antimicrobial behavior was tested using E. coli ATCC^® 25922™ following the ASTM E2149-13a standard. The mechanical properties of the paper sheets were measured by comparing tearing resistance, tensile strength, and bursting strength according to the ISO 5270 standard. The results showed an increased antibacterial response (assigned to the combination of chitosan and ZnO, independent of its shape and size) and boosted mechanical properties. Therefore, the proposed composition is an interesting multifunctional mixture for coatings in food packaging applications.

Alternative therapies against multidrug-resistant bacteria are widely investigated in the postantibiotic era. Polymicrobial biofilms formed by two or more species of bacteria or fungi pose an additional threat. The removal of such complex communities requires more effort and a multidirectional approach. In this study, the effectiveness of two bacteriophages vB_SauM-A (A) and vB_SauM-D (D) combined with ciprofloxacin was used to combat Staphylococcus aureus in the presence of Candida albicans both in liquid culture and biofilm. The results showed that phage-antibiotic synergy (PAS) led to the complete removal of S. aureus in liquid culture without bacterial population regrowth after 24 hours, and C. albicans enhanced this therapeutic effect. In a biofilm assay, C. albicans presence caused a decrease of bacterial eradication and a reduction of biofilm-specific activity (BSA). However, the strong effect of PAS was observed both in mono- and dual-species biofilm. Usage of phages and ciprofloxacin (1 mg/L) caused a 90% reduction of BSA of mono-species biofilm and 69% of dual-species biofilm. Phages alone resulted in a decrease of 71% and 48%, and ciprofloxacin (1 mg/L) alone resulted in 45% and 23% reduction, respectively. The influence of C. albicans on the PAS effect against S. aureus presented in this study was not previously investigated.

The main objectives of this study were to isolate bacteria from soil chronically contaminated with polycyclic aromatic hydrocarbons (PAHs), develop an autochthonous microbial consortium, and evaluate its ability to degrade PAHs in their native contaminated soil. Strains with the best bioremediation potential were selected during the multi-stage isolation process. Moreover, to choose bacteria with the highest bioremediation potential, the presence of PAH-degrading genes (pahE) was confirmed and the following tests were performed: tolerance to heavy metals, antagonistic behavior, phytotoxicity, and antimicrobial susceptibility. In vitro degradation of hydrocarbons led to the reduction of the total PAH content by 93.5% after the first day of incubation and by 99.22% after the eighth day. Bioremediation experiment conducted in situ in the contaminated area resulted in the average reduction of the total PAH concentration by 33.3% after 5 months and by over 72% after 13 months, compared to the concentration recorded before the intervention. Therefore, this study implicates that the development of an autochthonous microbial consortium isolated from long-term PAH-contaminated soil has the potential to enhance the bioremediation process.