Prevalence, phenotypic characteristics and genetic diversity of Burkholderia gladioli isolated from edible mushrooms

Burkholderia gladioli (B. gladioli) may cause food poisoning through the production of the toxin bongkrekic acid (BA), and could induce lung infections in patients with cystic fibrosis (CF). Edible mushrooms are a route of B. gladioli transmission; however, little effort has been focused on the prevalence of B. gladioli in edible mushrooms. In this study, 25 of the 325 edible mushroom samples were positive for B. gladioli, which showed moderate or strong biofilm formation capacity with a wide range of motility. Seventeen strains were capable of producing BA, while the isolates without toxin production lacked BA synthesis pathway genes bonK or bonR2. Antibiotic susceptibility testing indicated that all isolates were multidrug resistant. A considerable proportion of isolates were resistant to polymyxin B (100 %), chloramphenicol (84.62 %), aztreonam (84.62 %), ceftriaxone (84.62 %), and ticarcillin (61.54 %). None of the strains grew under environmental conditions such as pH below 4.0 or NaCl concentrations above 3.0 g/100 mL. Furthermore, 10 novel sequence typings (STs) were detected among the 25 isolates by multilocus sequence typing. This study provides valuable information for the control and prevention of B. gladioli contamination in common edible mushrooms for the first time.