Investigation of virulence factors and genes associated with biofilm and protease in Stenotrophomonas maltophilia isolates in Bushehr, Iran

This study aimed to investigate the virulence factors and genes associated with biofilm and protease in Stenotrophomonas maltophilia in Bushehr, Iran. Eighty-seven S. maltophilia isolates (67 clinical and 20 environmental isolates) were studied. The isolates were assessed for the production of virulence factors including several enzymes and biofilm. To detect rmlA, rpfF, spgM, smf-1, StmPr1 868 bp, StmPr1 1621 bp, and StmPr2 genes, PCR and sequencing were performed. All isolates (100%) produced DNase, hemolysin, protease, lipase, and hyaluronidase. Seventy-eight (89.7%) isolates were gelatinase producers, and 85 (97.7%) isolates were lecithinase producers. All isolates were biofilm producers: 79 (90.8%) isolates produced strong biofilm, 5 (5.7%) isolates produced moderate biofilm, and 3 (3.5%) isolates produced weak biofilm. The frequency of smf-1, rmlA, rpfF, and spgM was 93.1%, 86.2%, 26.4%, and 59.8%, respectively. The frequency of protease genes including StmPr1 868 bp, StmPr1 1621 bp, and StmPr2 was 12.6%, 41.4%, and 18.4%, respectively. Our findings revealed a high frequency of isolates that produce DNase, hemolysin, protease, gelatinase, lipase, lecithinase, hyaluronidase, and biofilm. All isolates that harbored spgM or rpfF or both genes were strong biofilm producers. Notably, the presence of isolates that lacked spgM and rpfF genes but produced strong biofilm indicates that in addition to these two genes, other genes or factors may play a role in the production of strong biofilm. Based on this research, S. maltophilia in our area possesses the capability to produce several factors that could play roles in pathogenicity.