Today Legionella pneumophila infections represent a significant problem for the Public Health due to the common presence of the microorganism in the sanitary water of numerous community places with a temperature of 25°C, ideal for the proliferation of this microorganism. These infections are commonly called Legionellosis, but actually we can distinguish two different forms: the mild form called Pontiac fever and the most common and severe form called Legionnaire’s disease. The transmission takes place through inhalation or aspiration of aerosols contaminated with Legionella. Droplets smaller than 5 μm are the most dangerous as they can reach the lower airways (lower respiratory tract) more easily. The mortality rate varies according to several factors and (it) is between 5 and 10%, reaching 40-80% in case of untreated immunocompromised patients. Identified for the first time in 1976, to the present day, knowledge about Legionella has greatly improved, nevertheless Legionellosis remains a very significant problem as the epidemiological data recorded in Italy and in the rest of the world have had a continuous increase in recent years due to partly to the improvement of surveillance systems, partly to the modification of lifestyle of the people, potentially more exposed to the risk of infections. It is a ubiquitous bacterium that can live in both natural and artificial habitats, this feature does not allow for a permanent and regulated solutions in order to prevent contamination. Actually, the prevention of the infection risk is based on the follow-up of environments potentially at risk of colonization and the main system able to generate aerosols. The aim of the thesis was to evaluate the contamination detected in three different community environments in northern Italy: a business centre (Administrative Directional Centre), a medical Centre and a sports centre; subsequently the effectiveness of decontamination process was checked by comparing the CFU values before and after the treatment. The tests were carried out according to the Directives of the Lombardy Region concerning the surveillance and control of legionellosis, with particular reference to the method reported in the analytical water sheet, “Metodo delle Membrane Filtranti”. The cultures were carried out on selective media with or without cysteine to test the auxotrophy for the aminoacids; the validation of the suspected colonies, after microscopic checking, was confirmed through the latex agglutination test. The procedure used includes four steps: culturing, observation of Petri plates, preliminary differential test and identification. The analysis of business centre samples revealed some points with higher contamination, while in others the contamination was less. A sanitization treatment and a local disinfection treatment were carried out in different points using chlorine, obtaining a significantly lower average concentration of Legionella. The samples from the Medical centre revealed the most critical issues, so precautionary measures were taken to prevent infections and decontamination interventions such as continuous hyperchlorination and thermal shock; however they were not sufficient to eradicate Legionella due to the high contamination level and the considerable area of the plant. After three months, a re-proliferation of the microorganism was detected. In some samples concerning the sports centre, high bacterial concentrations were detected and a thermal decontamination treatment was carried out. Thus, to contain the growth (proliferation) below (under) the limits listed in the Guidelines, especially in critical environments such as hospitals, it is necessary to periodically check the Legionella concentration by repeating the antimicrobial treatments several times a year.
Le infezioni da Legionella pneumophila rappresentano oggi un problema rilevante per la Salute pubblica a causa della frequente presenza del microrganismo nell’acqua sanitaria di numerosi luoghi comunitari con una temperatura di 25°C, ideale per la proliferazione del microrganismo. Queste infezioni vengono denominate comunemente legionellosi, anche se in realtà possiamo distinguere due forme differenti: la febbre di Pontiac che rappresenta la forma meno grave e la Malattia del legionario, forma più comune e severa della patologia. L’acquisizione avviene attraverso l’inalazione o l’aspirazione di aerosol contaminati da Legionella; le goccioline inferiori a 5 µm sono le più pericolose, in quanto riescono più facilmente a raggiungere le basse vie aeree. Il tasso di mortalità varia in base a diversi fattori e si attesta tra il 5 e il 10%, arrivando al 40-80% in caso di pazienti immunodepressi non trattati. Isolata per la prima volta nel 1976, ad oggi le conoscenze su Legionella sono ampiamente migliorate, ciò nonostante la legionellosi rimane un problema molto rilevante in quanto i dati epidemiologici registrati in Italia e nel resto del Mondo hanno avuto un incremento continuo negli ultimi anni dovuto in parte al miglioramento dei sistemi di sorveglianza, in parte alla modifica dello stile di vita della popolazione, potenzialmente sempre più esposta al rischio infezione. È un batterio ubiquitario che può vivere sia in habitat naturali che artificiali e questa caratteristica non permette delle soluzioni definitive e regolamentate per prevenire le contaminazioni. La prevenzione del rischio di infezione, ad oggi si basa sul monitoraggio degli ambienti potenzialmente a rischio colonizzazione e dei principali sistemi in grado di generare aerosol. Lo scopo del lavoro è stato la valutazione delle contaminazioni rilevate in 3 ambienti comunitari differenti nel nord Italia: un CDA, un centro clinico e un centro sportivo; successivamente è stata verificata l’efficacia del processo di decontaminazione attraverso il confronto tra i valori di CFU prima e dopo il trattamento. Le analisi sono state effettuate secondo quanto previsto dalle Direttive della Regione Lombardia in materia di Sorveglianza e controllo della legionellosi, con particolare riferimento al metodo indicato nella scheda analitica acqua, metodica Membrane Filtranti. Le colture sono state realizzate su terreni selettivi con o senza cisteina per verificare l’auxotrofia per l’amminoacido; la conferma delle colonie sospette, dopo verifica al microscopio, è stata confermata attraverso il test di agglutinazione al lattice. La procedura utilizzata prevede 4 fasi: semina, lettura, prova differenziale preliminare e identificazione. L’analisi dei campioni relativi al CDA hanno rilevato alcuni punti con una contaminazione più elevata, mentre in altri la contaminazione era più contenuta. È stato effettuato un trattamento di sanificazione e uno di disinfezione locale dei diversi punti utilizzando il cloro, ottenendo una concentrazione media di Legionella nettamente inferiore. I campioni relativi al centro clinico hanno rilevato le maggiori criticità, per cui sono state adottate misure precauzionali per evitare infezioni ed interventi di decontaminazione quali iperclorazione in continuo e shock termico, tuttavia non sono stati sufficienti ad eradicare Legionella a causa del livello elevato di contaminazione batterica e dell’estensione dell’impianto. Dopo 3 mesi è stata rilevata una riproliferazione del microrganismo. In alcuni campioni relativi al centro sportivo sono state rilevate concentrazioni batteriche elevate ed è stato effettuato un trattamento decontaminante termico. Per contenere la proliferazione sotto i limiti indicati nelle Linee Guida, soprattutto in ambienti critici come quello ospedaliero, è necessario un controllo periodico della concentrazione di Legionella ripetendo più volte l’anno i trattamenti antimicrobici indicati.
Prevenzione della legionellosi in ambito comunitario.
LA PASTINA, DANIELA
2019/2020
Abstract
Today Legionella pneumophila infections represent a significant problem for the Public Health due to the common presence of the microorganism in the sanitary water of numerous community places with a temperature of 25°C, ideal for the proliferation of this microorganism. These infections are commonly called Legionellosis, but actually we can distinguish two different forms: the mild form called Pontiac fever and the most common and severe form called Legionnaire’s disease. The transmission takes place through inhalation or aspiration of aerosols contaminated with Legionella. Droplets smaller than 5 μm are the most dangerous as they can reach the lower airways (lower respiratory tract) more easily. The mortality rate varies according to several factors and (it) is between 5 and 10%, reaching 40-80% in case of untreated immunocompromised patients. Identified for the first time in 1976, to the present day, knowledge about Legionella has greatly improved, nevertheless Legionellosis remains a very significant problem as the epidemiological data recorded in Italy and in the rest of the world have had a continuous increase in recent years due to partly to the improvement of surveillance systems, partly to the modification of lifestyle of the people, potentially more exposed to the risk of infections. It is a ubiquitous bacterium that can live in both natural and artificial habitats, this feature does not allow for a permanent and regulated solutions in order to prevent contamination. Actually, the prevention of the infection risk is based on the follow-up of environments potentially at risk of colonization and the main system able to generate aerosols. The aim of the thesis was to evaluate the contamination detected in three different community environments in northern Italy: a business centre (Administrative Directional Centre), a medical Centre and a sports centre; subsequently the effectiveness of decontamination process was checked by comparing the CFU values before and after the treatment. The tests were carried out according to the Directives of the Lombardy Region concerning the surveillance and control of legionellosis, with particular reference to the method reported in the analytical water sheet, “Metodo delle Membrane Filtranti”. The cultures were carried out on selective media with or without cysteine to test the auxotrophy for the aminoacids; the validation of the suspected colonies, after microscopic checking, was confirmed through the latex agglutination test. The procedure used includes four steps: culturing, observation of Petri plates, preliminary differential test and identification. The analysis of business centre samples revealed some points with higher contamination, while in others the contamination was less. A sanitization treatment and a local disinfection treatment were carried out in different points using chlorine, obtaining a significantly lower average concentration of Legionella. The samples from the Medical centre revealed the most critical issues, so precautionary measures were taken to prevent infections and decontamination interventions such as continuous hyperchlorination and thermal shock; however they were not sufficient to eradicate Legionella due to the high contamination level and the considerable area of the plant. After three months, a re-proliferation of the microorganism was detected. In some samples concerning the sports centre, high bacterial concentrations were detected and a thermal decontamination treatment was carried out. Thus, to contain the growth (proliferation) below (under) the limits listed in the Guidelines, especially in critical environments such as hospitals, it is necessary to periodically check the Legionella concentration by repeating the antimicrobial treatments several times a year.È consentito all'utente scaricare e condividere i documenti disponibili a testo pieno in UNITESI UNIPV nel rispetto della licenza Creative Commons del tipo CC BY NC ND.
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https://hdl.handle.net/20.500.14239/12176