Legionella is an aerobic gram-negative bacterium of which more than 60 species have been identified and divided into approximately 70 serotypes. Among the species identified, the most dangerous and the one responsible for 90% of cases of legionellosis is Legionella pneumophila. The object of this thesis is to study Legionella spp. present in sanitary waters through the ISO 11731:2017 method; specifically, one hundred water samples taken, in different places, were considered and then analyzed through filtration and direct placement of the membrane on the plate. The procedure requires that these samples are examined as they are (NT), after both heat (TT) treatment, at a temperature of 50°C, and acid (TA), using an HCl-KCl acid solution. In the case in question, out of 100 samples analyzed only 26 proved useful for comparison purposes. The data was finally reprocessed (using Excel software) both by analyzing - in light of the results obtained - the different types of samples analyzed (pie charts) and with the use of specific statistical tests (two-tailed Student's t test for paired data, Pearson's r correlation coefficient, linear regression) to evaluate whether the differences found were significant or not. In terms of results, the study conducted, highlighted that by comparing NT and TA statistically equal results are obtained, while by comparing NT with TT and TT with TA we have statistically different outcomes.
La Legionella è un batterio gram-negativo aerobio di cui sono state identificate più di 60 specie suddivise in circa 70 sierotipi. Tra le specie identificate, quella più pericolosa e responsabile del 90% dei casi di legionellosi è la Legionella pneumophila. L’oggetto del presente lavoro di tesi è lo studio della Legionella spp. presente nelle acque idrosanitarie attraverso il metodo ISO 11731:2017; nello specifico sono stati presi in considerazione cento campioni di acqua prelevati in luoghi differenti e poi analizzati tramite la filtrazione e la posa diretta della membrana su piastra. La procedura prevede che questi campioni vengano esaminati tal quali (NT) e dopo trattamento sia termico (TT), alla temperatura di 50°C, che acido (TA), utilizzando una soluzione acida HCl-KCl. Nel caso in esame, su 100 campioni analizzati solo 26 si sono rivelati utili al fine del confronto. I dati sono stati infine rielaborati (avvalendosi del software Excel) sia analizzando - alla luce dei risultati ottenuti - le diverse tipologie dei campioni analizzati (grafici a torta) che con l’utilizzo di appositi test statistici (test t di Student a due code per dati appaiati, coefficiente di correlazione r di Pearson, regressione lineare) per valutare se le differenze riscontrate fossero o meno significative. In termini di risultato, lo studio condotto ha evidenziato che confrontando NT e TA si ottengono risultati statisticamente uguali, mentre comparando NT con TT e TT con TA abbiamo esiti statisticamente diversi.
Trattamento acido e termico nella ricerca del batterio Legionella secondo il metodo ISO 11731:2017: confronto dei risultati ottenuti in campioni di acqua ad uso umano
LAMPIS, ILENIA
2023/2024
Abstract
Legionella is an aerobic gram-negative bacterium of which more than 60 species have been identified and divided into approximately 70 serotypes. Among the species identified, the most dangerous and the one responsible for 90% of cases of legionellosis is Legionella pneumophila. The object of this thesis is to study Legionella spp. present in sanitary waters through the ISO 11731:2017 method; specifically, one hundred water samples taken, in different places, were considered and then analyzed through filtration and direct placement of the membrane on the plate. The procedure requires that these samples are examined as they are (NT), after both heat (TT) treatment, at a temperature of 50°C, and acid (TA), using an HCl-KCl acid solution. In the case in question, out of 100 samples analyzed only 26 proved useful for comparison purposes. The data was finally reprocessed (using Excel software) both by analyzing - in light of the results obtained - the different types of samples analyzed (pie charts) and with the use of specific statistical tests (two-tailed Student's t test for paired data, Pearson's r correlation coefficient, linear regression) to evaluate whether the differences found were significant or not. In terms of results, the study conducted, highlighted that by comparing NT and TA statistically equal results are obtained, while by comparing NT with TT and TT with TA we have statistically different outcomes.File | Dimensione | Formato | |
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https://hdl.handle.net/20.500.12608/61931