L cysteine cys

The Legionella isolation was performed using a standard culture technique in accordance with ISO 11731:2017 (International Organization for Standardization, 2017 ). Briefly, for the enumeration of Legionella, different aliquots of the sample (from 200 to 100 μl), which comes from filtered water (untreated), heat- and acid-treated, were seeded on glycine–polymyxin B–vancomycin–cycloheximide (GVPC) selective agar (Thermo Fisher Scientific, Diagnostic, Ltd., Basingstoke, UK) and incubated at 35 ± 2°C with 2.5% of CO₂. The culture required a minimum of 10 for up to 15 days. Every 2 days, the plates were examined and the presumptive colonies were enumerated and sub-cultured on buffered charcoal yeast extract (BCYE) agar with and without L-cysteine (Cys+) and L-cysteine (Cys–) (Thermo Fisher Scientific, Diagnostic, Ltd., Basingstoke, UK). The Legionella colonies, growth only on BCYE Cys+, were identified using the Legionella latex agglutination test kit differentiating between Lp1, and Lp serogroups 2–14 (Lp2-14) and seven species of non-Lp species (Thermo Fisher Scientific, Ltd. Basingstoke, UK), based on manufacturing instructions.