Legionellae can infect and multiply intracellularly in both human phagocyti
c cells and protozoa. Growth of legionellae in the absence of protozoa has
been documented only on complex laboratory media. The hypothesis upon which
this study was based was that biofilm matrices, known to provide a habitat
and a gradient of nutrients, might allow the survival and multiplication o
f legionellae outside a host cell. This study determined whether Legionella
pneumophila can colonize and grow in biofilms with and without an associat
ion with Hartmannella vermiformis. The laboratory model used a rotating dis
c reactor at a retention time of 6(.)7 h to grow biofilms on stainless stee
l coupons. The biofilm was composed of Pseudomonas aeruginosa, Klebsiella p
neumoniae and a Flavobacterium sp. The levels of L. pneumophila cells prese
nt in the biofilm were monitored for 15 d, with and without the presence of
H. vermiformis, and it was found that, although unable to replicate in the
absence of H. vermiformis, L. pneumophila was able to persist.