Free-living amoebae and their relationship to air quality in hospital environments: characterization of Acanthamoeba spp. obtained from air-conditioning systems

Abstract

Free-living amoebae (FLA) are widely dispersed in the environment, can cause opportunistic and non-opportunistic infections in humans and other animals. The aim of the present study was characterize FLA obtained from air-conditioners of a public hospital in the city of Florianópolis, SC, Brazil. Fifty-four dust samples were collected of air conditioners, and were inoculated on 1.5% non-nutrient agar, overlaid with layers of Escherichia coli. Subsequently the isolates were axenised in PYG growth medium. The morphological and molecular characterization of the isolates was performed, as well as the tolerance (physiological) assays were used to evaluate the pathogenic potential. The results revealed the presence of FLA in 42 (77.8%) of the collected samples. Of these, 39 (92.9%) axenic isolates of FLA were obtained for morphological and genotypic studies. All the isolates characterized belong to the genus Acanthamoeba. Nineteen (48.7%) isolates belong to the genotype T4, 16 (41.0%) to the T5 genotype and 4 (10.3%) to genotype T11. Seven (18.0%) isolates were considered potentially pathogenic in tolerance assays. These findings require attention, considering the isolation environment and immunocompromised characteristics of many hospitalized patients.

Keywords: Acanthamoeba; air-conditioners; free-living amoebae; hospital.

Fig. 1.

Trophozoite of Acanthamoeba spp. presenting acanthopodia, and a nucleus with well-defined central nucleolus (a) and cyst compatible with group II (b). The bars represent 10 μm.

Fig. 2.

Neighbour-joining 18S rDNA tree of genotype Acanthamoeba spp. (MEGA X program). Test isolates including reference strains representing T1–T20 genotypes. Numbers at the nodes are percentage-bootstrapping values on 1000 replicates. Balamuthia mandrillaris was used as the outgroup. Bar 0.02 substitutions per nucleotide position.