An increase in the number of reports of legionellosis in the European Union and the European Economic Area have been recorded in recent years. The increase in cases is significant: from 6947 reports in 2015 to 11,298 in 2019. This is alarming as genus Legionella, which comprises a large group of bacteria inhabiting various aquatic systems, poses a serious threat to human health and life, since more than 20 species can cause legionellosis, with L. pneumophila being responsible for the majority of cases. The ability to colonize diverse ecosystems makes the eradication of these microorganisms difficult. A detailed understanding of the Legionella habitat may be helpful in the effective control of this pathogen. This paper provides an overview of Legionella environments in Europe: natural (lakes, groundwater, rivers, compost, soil) and anthropogenic (fountains, air humidifiers, water supply systems), and the role of Legionella spp. in nosocomial infections, which are potentially fatal for children, the elderly and immunocompromised patients. Graphical abstract

Agarose gel electrophoresis is a well-known tool to detect DNA fragments amplified in polymerase chain reaction (PCR). Its usefulness has also been confirmed for epidemiological studies based on restriction fragments length polymorphism (RFLP), usually performed using pulsed-field gel electrophoresis (PFGE). Little is known on the effectiveness for alert-pathogen epidemiological studies of another less time-consuming and costly technique called randomly amplified polymorphic DNA-PCR (RAPD-PCR). Meanwhile, its usefulness is believed to be comparable to RFLP-PFGE. Therefore, the aim of the study was to establish and optimize the conditions of agarose gel electrophoresis following RAPD-PCR for 19 Enterococcus faecium strains derived from epidemic outbreaks at intensive care units. An application of different PCR primers, primer combinations, and, in particular, agarose gel concentrations and electrophoresis conditions revealed the usefulness of this relatively fast and inexpensive method based on RAPD-PCR for epidemiological studies without a compulsion to use the specialized equipment necessary for RFLP-PFGE.

The reuse of wash water in the agri-food industry is in line with sustainability goals through the reduction of the water footprint. Depending on the production process and raw material type, wash waters may exhibit severe biological and physicochemical contamination. The use of traditional methods of chlorine disinfection of water may be linked to the formation of hazardous by-products. The recycling of contaminated water should be supported by the evaluation of physicochemical and microbiological parameters before and after application of a treatment to validate the process. This study aimed to assess physicochemical and microbiological properties of rinse water from a post-harvest processing plant before and after applying an innovative modular water treatment system. The test material was washing water after apple rinsing obtained from a post-harvest processing plant (Northern Poland). The water recovery system included a wash water tank, a sand pre-filter, an ultrafiltration system, and an ozonation tank. No microorganisms were found in the treated water. The physicochemical properties of the water were also improved: pH, conductivity, turbidity, ammonium ion, bromide, and nitrate content. The results indicate that rinse water from the fruit industry may be effectively purified using the tested purification system and reused in production processes.

Water used in cleaning processes within the agri-food industry can be a vector for post-harvest contaminants, thus contributing to cross-contamination. The contamination risk is increased when water is not replaced between batches or when disinfection protocols are insufficient. Given the increasing focus in recent years on the potential of natural, non-invasive plant extracts to combat a variety of pathogens, including multidrug-resistant bacteria, environmental strains, and clinical isolates, this study aimed to evaluate the antibacterial activity of selected water-ethanol plant extracts against six opportunistic pathogens isolated from wash water in the agri-food industry, along with chromatographic analyses of the selected extracts. Plant extracts were obtained from the fruits, leaves, shoots, roots, and bark of 13 species. Antibacterial activity was assessed using the well diffusion method. The results indicated that antimicrobial activity was exhibited by six extracts: Tilia cordata Mill., Camellia sinensis, Quercus robur L., Betula pendula Roth, Rubus idaeus L., and Salix alba L. The extracts showed strain-dependent antimicrobial activity, with C. sinensis and R. idaeus up to 4.0 mm and 8.0 mm inhibition zones, respectively. P. aeruginosa and E. faecalis were the most susceptible strains, demonstrating the largest inhibition zones. In contrast, P. vulgaris and K. oxytoca were more resistant. The efficacy of the most active extracts can be linked to the presence of phytochemicals identified via GC-MS, including epicatechin, shikimic acid, quinic acid, gallic acid, and caffeine. These metabolites are known to interfere with bacterial cell structures and metabolic pathways. These studies may serve as a preliminary step toward the development of non-invasive water treatment methods for wash water.

The fruit and vegetable industry in post-harvest processing plants is characterized by a substantial consumption of water resources. Wash waters may serve as an environment for the periodic or permanent habitation of microorganisms, particularly if biofilm forms on the inner walls of tanks and flushing channels. Despite the implementation of integrated food safety monitoring systems in numerous countries, foodborne pathogens remain a global public health and food safety concern, particularly for minimally processed food products such as vegetables and fruits. This necessitates the importance of studies that will explore wash water quality to safeguard minimally processed food against foodborne pathogen contamination. Therefore, the current study aimed to isolate and identify bacteria contaminating the wash waters of four fresh-cut processing plants (Poland) and to evaluate the phenotypic antibiotic resistance profiles in selected species. Bacteria were isolated using membrane filtration and identified through mass spectrometry, followed by antibiotic susceptibility testing according to EUCAST guidelines. The results revealed that the level of contamination with total aerobic bacteria in the water ranged from 1.30 × 10⁶ cfu/mL to 2.54 × 10⁸ cfu/mL. Among the isolates, opportunistic pathogens including Enterococcus faecalis, Pseudomonas aeruginosa, Klebsiella oxytoca, Klebsiella pneumoniae, Serratia marcescens, and Proteus vulgaris strains were identified. An especially noteworthy result was the identification of cefepime-resistant K. oxytoca isolates. These findings highlight the importance of monitoring the microbial microflora in minimally processed foods and the need for appropriate sanitary control procedures to minimize the risk of pathogen contamination, ensuring that products remain safe and of high quality throughout the supply chain.

Pseudomonas aeruginosa is an opportunistic pathogen encoding several virulence factors in its genome, which is well-known for its ability to cause severe and life-threatening infections, particularly among cystic fibrosis patients. The organism is also a major cause of nosocomial infections, mainly affecting patients with immune deficiencies and burn wounds, ventilator-assisted patients, and patients affected by other malignancies. The extensively reported emergence of multidrug-resistant (MDR) P. aeruginosa strains poses additional challenges to the management of infections. The aim of this study was to compare the incidence rates of selected virulence-factor-encoding genes and the genotype distribution amongst clinical multidrug-sensitive (MDS) and MDR P. aeruginosa strains. The study involved 74 MDS and 57 MDR P. aeruginosa strains and the following virulence-factor-encoding genes: lasB, plC H, plC N, exoU, nan1, pilA, and pilB. The genotype distribution, with respect to the antimicrobial susceptibility profiles of the strains, was also analyzed. The lasB and plC N genes were present amongst several P. aeruginosa strains, including all the MDR P. aeruginosa, suggesting that their presence might be used as a marker for diagnostic purposes. A wide variety of genotype distributions were observed among the investigated isolates, with the MDS and MDR strains exhibiting, respectively, 18 and 9 distinct profiles. A higher prevalence of genes determining the virulence factors in the MDR strains was observed in this study, but more research is needed on the prevalence and expression levels of these genes in additional MDR strains.