Results and Discussion
Microbiological analyses for the two collections of ATSW, “Nuove Terme di Agnano srl”, was performed during the winter and autumn seasons through two procedures, in order to increase the yield for the microbiological characterization. The two procedures, filtration and enrichment, highlighted in both sampling the abundance of bacterial species belonging mainly to three different phyla: Actinobacteria, Firmicutes and Proteobacteria with a prevalence of species belonging to the phylum Firmicutes (Table 2). The filtration procedure determined the isolation of four bacterial isolates for winter sampling and ten isolates form autumn sampling, while the enrichment method revealed the presence in thermal water of sixteen different bacterial species for winter sampling and eight bacterial species for autumn sampling (Table 3). The analysis showed a difference between the bacterial populations associated with seasonal changes, highlighting a majority of species belonging to the genus Staphylococcus , with a prevalence of Coagulase-negative Staphylococci (ConS) for winter sampling using enrichment procedure, and the genus Bacillus for autumn sampling, using both procedures. To underline, the species Pseudomonas stutzeri and Bacillus subtilis have been isolated from cultures incubated at 50°C for autumn sampling.
The most represented phylum, Firmicutes, mainly includes gram-positive species with a genome characterized by a low GC content and includes several mobile and capable of forming endospores species (Schleifer, 2009). The members of this phylum are abundant in soil and water where they are involved in the decomposition and recycling of organic matter (Gibbons and Murray, 1978). However, different genera of phylum Firmicutes belong to the normal human flora or can be associated with diseases in humans and animals (Baik et al., 2008). Moreover, some members of this phylum may have an industrial use for the production of enzymes or antimicrobial and antifungal activities, such as the speciesLactobacillus plantarum , which is used in the food industry, andBacillus pumilus , which has an antimicrobial activity towardsVibrio spp. and fungicide (Liu et al., 2012) (both isolated during the autumn sampling by filtration procedure).
Within the phylum Proteobacteria, in particular, in the Gamma proteobacteria some Pseudomonas spp. like P. luteola andP. stutzeri , could be relevant because they are both involved in bio-absorption’s mechanisms. P. luteola is involved in bio-absorption processes of heavy metals such as chromium and aluminum in acid environments, metal ions often present in industrial waste water and is also involved in the absorption of copper and nickel as it is a producer of exopolysaccharide (Ozdemir and Baysal, 2004). Also, the species P. stutzeri is considered an excellent candidate for the simultaneous absorption of nitrogen and phosphate in waste water, in fact it oxidizes ammonia exhibiting the ability of nitrification and denitrification as well as the ability to degrade organophosphorus pesticides (Ozdemir et al., 2005).
Among the identified phyla is represented, although to a lesser extent, the phylum Actinobacteria. To this phylum belong different genera of Gram positive bacteria present both in terrestrial and aquatic environments. These microorganisms have a great importance for the human being since agriculture and forests depend on the contribution of these bacteria to the processes that take place in the soil. In this environment, the Actinobacteria grow with characteristics similar to fungi, forming extensive structures similar to mycelia, favoring the decomposition of the organic matter of dead organisms so as to provide the essential elements for plant growth (Servin et al., 2008).
Therefore, the ATSW analyzed is rich in non-pathogenic bacteria that may play a role in treating various skin disease (Balato et al., 2019). As ATSW contains live bacteria that could impact the skin’s microbiota, the water itself is considered to be a probiotic (Zeichner et al., 2018). Although probiotics have been widely used in the past for the treatment/prevention of gastrointestinal disorders, a growing number of evidences has suggested that they can modulate the composition of microbial community, exerting their healthy effect directly or indirectly on the skin (Balato et al., 2019; Zeichner et al., 2018).
Moreover, the ATSW is a rich source of minerals. About 31 minerals have been identified of which 17 are found as major ions (>/= 0,4 mg/l) like chloride, sodium, bicarbonate, sulphate, carbon dioxide, potassium, silicon, calcium, magnesium, boron, ammonium, bromide, strontium, litium, fluoride, manganese, arsenic.
Sodium helps to maintain the suppleness of skin due to its water-holding capacity. Hence it is very useful in dry dermatoses like psoriasis and ichthyosis. It also helps in desquamation of hyperkeratotic lesions (Rivaz et al., 2011).
Noteworty, among cations of interest, Mg2+ and Ca2+ have been recognized for their benefits in skin barrier recovery (Denda et a., l999). In normal skin, magnesium and calcium ions were localized with a high concentration in the upper epidermis (Proksch et al., 2005). After barrier disruption, the gradients of calcium, magnesium, and potassium in the epidermis disappeared while the pH was not altered (Denda et a., l999). Loss in the ion gradient is a signal for an increase in proliferation, differentiation and lipid synthesis aimed to repair the perturbed barrier (Lee et al., 1992, Denda et al., 2003). Magnesium is also essential for cell metabolism. It helps in maturation and differentiation of keratinocytes. Hence it is very useful in psoriatic patients who have a low magnesium level in the serum and scales (Rivaz et al., 2011). Calcium-and magnesium-rich thermal spring waters are known to improve skin barrier function and accelerate wound healing (Proksch et al., 2005).
Moreover, the soothing and protective properties of thermal spring waters in sensitive skin (antioxidant or anti-ageing) are enhanced by the presence of trace elements such as selenium, strontium (Celerier et al., 1995). These properties have been demonstrated in many studies using human keratinocytes, fibroblasts or other response-appropriate cell lines (Seite et al., 2013; Joly et al., 1998). Furthermore, a recent study demonstrated the activity of salso-bromo-iodine water on mucous-secretory disorders, in particular it helped to improve the relationship between the mucous-protein complexes and the water: initially, this action was congestive, subsequently, it became an anti-catarrhal, anti-inflammatory, antiseptic and immunostimulant action (La Mantia et al., 2018).
The ATWS for its mineral composition and microbial diversity exhibits both prebiotic and probiotic characteristic, thus it will be analyzed for its anti-inflammatory and regenerative properties in an in vitro system.