engleski

The effect of desiccation on Legionella viability and infectivity

ABSTRAKT: Legionella bacteria are gram-negative rods which are considered to be ubiquitous in the aquatic environment including natural and man-made waters. Some of species, such as Legionella longbeachae, have the ability to grow and reproduce in soil and potting compost. Legionella species are recognized as a common cause of community-acquired and nosocomial bacterial pneumonia. Legionella are also known for its ability to multiply intracellularly within protozoan hosts. These amoebal hosts provide Legionella with protection from different unfavorable environmental conditions. The purpose of this study was to determine the survival of Legionella species on plastic surfaces in dry conditions. Also, infectivity and viability of bacteria exposed to desiccation was tested in Achanthamoeba castellanii as host. For desiccation study, bacteria were prepared in sterile water and 5 x 20µl of bacterial suspension (~10(8) cfu/ml) were transferred in 96 wells plates and dried for 1 hour under laminar flow hood. The plates with dried Legionella, as well as plates with control bacterial suspensions (wet conditions) were stored at room temperature. Bacteria were rehydrated and cultivated at different time points on BCYE agar. At the same time, Legionella cells exposed to desiccation were added to A. castellanii monolayers and incubated for 48 hours. The results of cocultivation of L. pneumophila and L. longbeachae showed that both Legionella were able to replicate in A. castellanii. Both Legionella could be cultivated only after first day of desiccation. After 2, 3, 4 and 7 days of desiccation viable but nonculturable (VBNC) Legionella were able to infect and proliferate within amoeba. In conclusion, L. pneumophila and L. longbeachae exposed to desiccation loss their culturability but are able to infect and replicate in Acanthamoeba castellanii and may represent a threat for humans.

Legionella; desiccation; survival

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