LETTERSsequencing. This infection rate is within the range (13.5%-90%) that has been reported for R. felis infecting Ctenocephalides fl eas in Brazil and Uruguay (2,3,7). Sixteen (72.7%) cats contained R. felis-reactive antibodies; 4 of them showed titers to R. felis at least 4-fold higher than those to the other 5 rickettsial strains, fi ndings that enabled us to technically conclude that these cats were exposed to R. felis or a closely related organism (1,7,9). Our fi nding of 70% R. felis infection in fl eas infesting the cats indicates that cats acquired the infection through infected fl eas. However, the mechanism of R. felis transmission by fl eas is yet to be demonstrated under experimental conditions.To our knowledge, the presence of R. felis, or a spotted fever group Rickettsia species, has not been reported in Chile. Recent investigations have provided clinical and serologic evidence of canine (10) and human (K. Abarca and J. Lopez, unpub. data) infection by spotted fever rickettsia in Chile, confi rmed by IFA that used R. conorii commercial antigen. Since substantial serologic cross-reaction occurs between R. conorii and R. felis antigens (1), R. felis could be causing infection in dogs or humans in Chile.

Legionellosis (LG, infection by members of the genus Legionella) can range from mild respiratory illness to acute life-threatening pneumonia. The majority of LG cases are caused by Legionella pneumophila (LP), particularly serogroup 1 (18). Since the first outbreak in Philadelphia in 1976 (12), LP has been recognized as an important etiological agent of hospital-and community-acquired pneumonia. This microbe can survive in a wide range of temperature (5-65 C) and pH (5.5-9.5), particularly in warm and damp environments of 35-45 C which is their favorable growth temperature range. Because of their high survival rate in a thermal and wet environment, which happens to be the atmosphere regularly established in a whirlpool spa, numerous outbreaks of LG have been traced to the spa water as the source of their causative agents (2,17,20,21,23,31).Tracing the source of LG was often determined by linking environmental isolates to clinical isolates by various molecular subtyping methods, of which at least 7 kinds have been reported (15). Among them, amplified fragment length polymorphism (AFLP) and pulsefield gel electrophoresis (PFGE) were two methods most often used and highly recommended (3, 13).