Helicobacter pylori, a gastric pathogen associated with a broad range of stomach diseases, has a high tendency to become resistant to antibiotics. One of the most important factors related to therapeutic failures is its ability to change from a spiral to a coccoid form. Therefore, the main aim of our original article was to determine the influence of myricetin, a natural compound with an antivirulence action, on the morphological transformation of H. pylori and check the potential of myricetin to increase the activity of antibiotics against this pathogen. We observed that sub-minimal inhibitory concentrations (sub-MICs) of this compound have the ability to slow down the process of transformation into coccoid forms and reduce biofilm formation of this bacterium. Using checkerboard assays, we noticed that the exposure of H. pylori to sub-MICs of myricetin enabled a 4–16-fold reduction in MICs of all classically used antibiotics (amoxicillin, clarithromycin, tetracycline, metronidazole, and levofloxacin). Additionally, RT-qPCR studies of genes related to the H. pylori morphogenesis showed a decrease in their expression during exposure to myricetin. This inhibitory effect was more strongly seen for genes involved in the muropeptide monomers shortening (csd3, csd6, csd4, and amiA), suggesting their significant participation in the spiral-to-coccoid transition. To our knowledge, this is the first research showing the ability of any compound to synergistically interact with all five antibiotics against H. pylori and the first one showing the capacity of a natural substance to interfere with the morphological transition of H. pylori from spiral to coccoid forms.

Quantifying changes in bacteria cells in the presence of antibacterial treatment is one of the main challenges facing contemporary medicine; it is a challenge that is relevant for tackling issues pertaining to bacterial biofilm formation that substantially decreases susceptibility to biocidal agents. Three-dimensional label-free imaging and quantitative analysis of bacteria–photosensitizer interactions, crucial for antimicrobial photodynamic therapy, is still limited due to the use of conventional imaging techniques. We present a new method for investigating the alterations in living cells and quantitatively analyzing the process of bacteria photodynamic inactivation. Digital holographic tomography (DHT) was used for in situ examination of the response of Escherichia coli and Staphylococcus aureus to the accumulation of the photosensitizers immobilized in the copolymer revealed by the changes in the 3D refractive index distributions of single cells. Obtained results were confirmed by confocal microscopy and statistical analysis. We demonstrated that DHT enables real-time characterization of the subcellular structures, the biophysical processes, and the induced local changes of the intracellular density in a label-free manner and at sub-micrometer spatial resolution.

Bovine respiratory disease causes significant economic losses in cattle farming due to mortality, treatment costs, and reduced productivity. It involves viral and bacterial infections, with Pasteurella multocida and Mannheimia haemolytica key bacterial pathogens. These bacteria contribute to severe pneumonia and are often found together. Poland has one of the highest levels of antimicrobial use in food-producing animals among European Union countries. A total of 70 bacterial strains were analyzed, 48 P. multocida and 22 M. haemolytica, collected from affected calves’ respiratory tracts. The bacterial species were confirmed molecularly using PCR, which was also employed to detect antimicrobial resistance and virulence-associated genes. Antimicrobial susceptibility was determined using the broth microdilution method. Antimicrobial resistance varied between the two bacterial species studied. The highest resistance in P. multocida was to chlortetracycline 79.2% (38/48) and oxytetracycline 81.3% (39/48), while M. haemolytica showed 63.6% (14/22) resistance to penicillin and tilmicosin. The highest susceptibility was found for fluoroquinolones: P. multocida demonstrated 91.7% (44/48) susceptibility to enrofloxacin and 87.5% (42/48) to danofloxacin, while 77.3% (17/22) of M. haemolytica were susceptible to both tested fluoroquinolones. The tetH and tetR genes were observed only in P. multocida, at frequencies of 20.8% (10/48) and 16.7% (8/48), respectively. Both species carried the mphE and msrE genes, though at lower frequencies. All M. haemolytica contained the lkt, gs60, and gcp genes. All P. multocida carried the sodA gene, while the hgbB and ompH genes were present in 37.5% (18/48) and 20.8% (10/48) of strains, respectively. The highest resistance was observed against the most commonly used antibiotics in the European Union, although the resistance differed between the studied bacterial species and each strain exhibited the presence of at least one virulence gene.

Gallibacterium anatis biovar haemolytica is a bacterium that is frequently associated with infections of the reproductive tract and respiratory system in poultry. To assess the current prevalence and resistance profile of these bacteria in Poland, we collected and investigated 63 strains of Gallibacterium from diseased domestic poultry flocks including geese, laying hens, breeding hens and an ornamental hen. Detailed characterization of the isolates included the analysis of phenotypic antimicrobial resistance profiles and biofilm formation ability. Furthermore, the genetic background of 40 selected isolates regarding the presence of virulence and antimicrobial resistance genes and mobile genetic elements was determined. All investigated isolates were multidrug resistant, most prominently to β-lactams, fluoroquinolones, sulfonamides and macrolides. A total of 48 different resistance profiles were detected. Of all isolates, 50.8% formed a strong biofilm, where strains isolated from geese appeared to be better at biofilm formation than strains isolated from laying and breeding hens. Single-nucleotide polymorphism genotyping revealed that G. anatis bv. haemolytica strains are restricted in host and geographical distribution, and the geese isolates showed greater phylogenetic similarity. Whole genome sequencing enabled identification of 25 different antimicrobial resistance determinants. The most common resistance genes were tetB, bla_ROB-1, and bla_TEM-1 which may be located on mobile genetic elements. All isolates possessed the toxin gene gtxA, and the fimbrial gene flfA was identified in 95% of strains. Our results indicated that all G. anatis bv. haemolytica isolates showed multidrug resistant phenotypes. Strains isolated from geese were characterized by the highest percentage of isolates resistant to selected antimicrobials, probably reflecting host-related adaptations.

Staphylococcus saprophyticus (S. saprophyticus) is an opportunistic coagulase-negative staphylococcus (CoNS) known to cause urinary tract infections in humans and is increasingly recognized in veterinary medicine. The aim of this study was to provide an epidemiological characterization of S. saprophyticus strains and to identify potential virulence factors that may contribute to interspecies transmission. This research is particularly important, as companion animals represent an understudied reservoir of this microorganism, and their role in the spread of resistant pathogens remains insufficiently understood. A total of 61 S. saprophyticus strains isolated from humans, dogs, and cats were analyzed. Identification was performed using MALDI-TOF MS and confirmed by PCR targeting the hrcA gene. Antimicrobial susceptibility was assessed using the disk diffusion and broth microdilution methods, while resistance genes were detected by PCR. The blaZ and mecA genes were present in all strains; additionally, the majority harbored the resistance genes ermA, ermB, tetM, and tetK. Multidrug resistance (MDR) was identified in 21/61 strains (34.4%). Biofilm-forming capacity was temperature-dependent, with the strongest biofilm production observed at 37 °C (70.5%). At 38 °C and 39 °C, the proportion of strong biofilm producers decreased to 50.8% and 52.5%, respectively. All tested strains demonstrated pathogenic potential in the Galleria mellonella larvae infection model, with the highest mortality recorded for selected feline and canine strains. These findings indicate that S. saprophyticus strains from both humans and companion animals possess notable virulence and multidrug resistance. The detection of genotypically and phenotypically resistant strains in animals highlights their potential role as reservoir for zoonotic transmission.

The worldwide increase in bacterial resistance and healthcare-associated bacterial infections pose a serious threat to human health. The antimicrobial photodynamic method reveals the opportunity for a new therapeutic approach that is based on the limited delivery of photosensitizer from the material surface. Nanoporous inorganic–organic composites were obtained by entrapment of photosensitizer Photolon in polysiloxanes that was prepared by the sol–gel method. The material was characterized by its porosity, optical properties (fluorescence and absorbance), and laser-induced antimicrobial activity against Staphylococcus epidermidis, Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. The permanent encapsulation of Photolon in the silica coating and the antimicrobial efficiency was confirmed by confocal microscope and digital holotomography. The generation of free radicals from nanoporous surfaces was proved by scanning Kelvin probe microscopy. For the first time, it was confirmed that Kelvin probe microscopy can be a label-free, noncontact alternative to other conventional methods based on fluorescence or chemiluminescence probes, etc. It was confirmed that the proposed photoactive coating enables the antibacterial photodynamic effect based on free radicals released from the surface of the coating. The highest bactericidal efficiency of the proposed coating was 87.16%. This coating can selectively limit the multiplication of bacterial cells, while protecting the environment and reducing the risk of surface contamination.