Nontuberculous Mycobacteria Prevalence in Bats' Guano from Caves and Attics of Buildings Studied by Culture and qPCR Examinations

A total of 281 guano samples were collected from caves (N = 181) in eight European countries (Bulgaria, Czech Republic, France, Hungary, Italy, Romania, Slovakia and Slovenia) and attics in the Czech R. (N = 100). The correlation of detection of mycobacteria between Ziehl-Neelsen (ZN) microscopy and culture examination and qPCR was strong. ZN microscopy was positive in guano from caves (58.6%) more than double than positivity in guano from attics (21.0%; p < 0.01). From 89 mycobacterial isolates (73 isolates from cave guano and 16 isolates from attics' guano), 68 (76.4%) isolates of 19 sp., ssp. and complex were identified as members of three Groups (M. fortuitum, M. chelonae, and M. mucogenicum) and four complexes (M. avium, M. terrae, M. vaccae, and M. smegmatis). A total of 20 isolates (22.5%) belonged to risk group 1 (environmental saprophytes), 48 isolates (53.9%) belonged to risk group 2 (potential pathogens), and none of the isolates belonged to risk group 3 (obligatory pathogens). When comparing bat guano collected from caves and attics, differences (p < 0.01; Mann-Whitney test) were observed for the electrical conductivity, total carbon, total organic, and total inorganic carbon. No difference (p > 0.05; Mann-Whitney test) was found for pH and oxidation-reduction potential parameters.

Automated summary

This study collected bat guano samples from eight European countries, finding a higher detection rate of mycobacteria in guano from caves compared to guano from attics. Additionally, different risk groups of mycobacterial isolates were identified, and differences in physical and chemical properties between cave and attic guano were observed.