Investigation of Legionella contamination in soil

Abstract

Objective To understand the contamination of Legionella in soil and the molecular type, sensitivity to antibiotics and intracellular growth ability of isolated strains. Methods A total of 123 soil samples from public places in Beijing were collected. Legionella in soil was detected by GVPC (Legionella selective medium) culture and quantitative real-time PCR detection. The intracellular growth ability of the Legionella isolates were tested by cell culture methods with mouse macrophage J774. The genotypes of the isolates were determined by pulsed-field gel electrophoresis. Antibiotic sensitivity detection of the isolates was conducted with E-test. Results Quantitative PCR assay detected Legionella in flower & bird market samples and reservoir samples in summer. The positive rates were 50.00% and 24.24% respectively. The plate culture method only detected Legionella in reservoir samples in summer. The positive rate was 6.06%. All the two Legionella strains isolated, TR1 and TR2, were L. pneumophila, and the serotypes were type 5 and type 8 respectively. All the two strains of L. pneumophila had high intracellular growth ability. PFGE typing showed two different band types. The drug sensitivity test showed that the two strains were sensitive to erythromycin, azithromycin, rifampicin, levofloxacin and moxifloxacin. TR1 showed resistance to cefuroxime, and TR2 was sensitive to cefuroxime. Conclusions Legionella pneumophila was detected in the soil of public places, and the isolates have higher intracellular growth ability, indicating the pathogenicity of the strains and suggesting the potential of causing legionellosis epidemic. Therefore, we should strengthen the monitoring of Legionella in public places.