Experimental Transmission of Legionnaires' Disease by Exposure to Aerosols of Legionella Pneumophila

Survival of virulentLegionella pneumophilain aerosols

“…This study and those of Baskerville et al (1981Baskerville et al ( , 1982 show clearly that L. pneumophila strain 74/81 can retain viability, virulance and aerosol stability when stored in an aqueous environment. The aerosol stability of organisms with low metabolic activity is such that significant numbers of viable organisms can be recovered from bacterial clouds after up to 2 h. Since contaminated evaporative condensers, for example, might be anticipated to generate continuously aerosols containing viable L. pneumophila organisms, it is clearly likely that exposed susceptible humans might inhale and retain sufficient viable organisms to acquire an infection.…”

“…There is little or no evidence to support person to person transmission of legionellosis (Mallison, 1980), indeed, sentinel guinea pigs housed with others having experimental respiratory legionellosis do not succomb to infection (R. B. Fitzgeorge, unpublished; Katz et al 1982). Confirmation of airborne transmission as the most likely route of infection was provided when Baskerville and co-workers described experimental respiratory infection of guinea pigs and rhesus monkeys (Baskerville et al 1981) and marmosets (Baskerville et al 1982) with aerosols of a virulent strain (74/81) of L. pneumophila which gave rise to pneumonic lesions resembling those seen in human legionellosis.…”

“…The strain of L. pneumophila used was the serogroup 1 74/81 strain isolated from a naturally contaminated water supply (Baskerville et al 1981). The organisms were grown on Edelstein's (1981) modification of charcoal-yeast-extract (CYE) agar for 4 days at 37°C in air or, for some experiments, in a liquid medium similar to that described by Ristroph, Hedlund & Allen (1980).…”

“…Aerosols of L. pneumophila strain 74/81 grown on a solid medium and suspended in water are infectious for laboratory animals (Baskerville et al 1981) and a similar suspension of this strain, stored at 4 C, was used for much of the present study.…”

Temperature-dependent expression of flagella in Legionella

“…Bacterial strains used are listed in Table 1. The avirulent derivative of L. pneumophila Philadelphia I , XXXV, has been described elsewhere (Bender et al, 1990 (ATCC 33 152) has been passaged intraperitoneally in guinea pigs. Bacteria removed after the second passage from the peritoneum of the animal exhibiting symptomatic peritonitis were cultured once on buffered charcoal yeast extract (BCYE) agar and frozen.…”