Biofilm Formation among Stenotrophomonas maltophilia Isolates Has Clinical Relevance: The ANSELM Prospective Multicenter Study

Abstract

The ability to form biofilms is a recognized trait of Stenotrophomonas maltophilia, but the extent of its clinical relevance is still unclear. The present multicenter prospective study (ANSELM) aims at investigating the association between biofilm formation and clinical outcomes of S. maltophilia infections. One hundred and nine isolates were collected from various geographical origins and stratified according to their clinical relevance. Biofilm formation was evaluated by the microtiter plate assay and correlated with microbiological and clinical data from the associated strains. Antibiotic susceptibility of the planktonic cells was tested by the disk diffusion technique, while antibiotic activity against mature biofilms was spectrophotometrically assessed. Most strains (91.7%) were able to form biofilm, although bloodborne strains produced biofilm amounts significantly higher than strains causing hospital- rather than community-acquired infections, and those recognized as “definite” pathogens. Biofilm formation efficiency was positively correlated with mechanical ventilation (p = 0.032), whereas a negative relationship was found with antibiotic resistance (r2 = 0.107; p < 0.001), specifically in the case of the pathogenic strains. Mature S. maltophilia biofilms were markedly more resistant (up to 128 times) to cotrimoxazole and levofloxacin compared with their planktonic counterparts, especially in the case of bloodborne strains. Our findings indicate that biofilm formation by S. maltophilia is obviously a contributing factor in the pathogenesis of infections, especially in deep ones, thus warranting additional studies with larger cohort of patients and isolates.

Inactivation of Opportunistic Pathogens Acinetobacter baumannii and Stenotrophomonas maltophilia by Antimicrobial Photodynamic Therapy

“…The ability to form biofilms is one of the most important virulence factors for both pathogens, and the majority of clinical isolates are biofilm producers [ 41 ]. It was shown that S. maltophilia biofilms were up to 128 times more resistant to trimethoprim/sulfamethoxazole and levofloxacin treatment compared with planktonic cells [ 42 ]. Biofilm-mediated antibiotic resistance in clinical A. baumannii strains was also described [ 43 ].…”

Bactericidal Activity of Ceragenin in Combination with Ceftazidime, Levofloxacin, Co-Trimoxazole, and Colistin against the Opportunistic Pathogen Stenotrophomonas maltophilia

“…Considering that more than 60% of infections are associated with the ability of a microorganism to form a biofilm, much attention is also paid to research on the anti-biofilm properties of ceragenins. Biofilm is also an important factor in S. maltophilia infections, [48] and the anti-biofilm effects of ceragenins suggest that they have the potential for application against S. maltophilia strains [19,49]. The high anti-biofilm activity of ceragenins is confirmed by many previous studies [50][51][52].…”

Comparative Proteomic Analysis of Protein Patterns of Stenotrophomonas maltophilia in Biofilm and Planktonic Lifestyles

“…S. maltophilia can adhere to several surfaces and grow as a biofilm, a microbial consortium embedded in a self-produced polymeric matrix and inherently resistant to antibiotic therapy and the host immune response [ 6 ]. Several studies have recently indicated that the ability to form biofilm is highly conserved in clinically relevant S. maltophilia isolates [ 7 ]. Biofilm formation can occur on inert surfaces (e.g., respiratory tubes and nebulizers, intravenous cannulae, prosthetic devices, and dental unit waterlines), causing medical implant-associated infections [ 3 ].…”

“…The genetic regulation of biofilm formation in S. maltophilia is complex, as suggested by the significant number of genes involved [ 6 ]. Several studies indicated that the ability of S. maltophilia to form biofilm is mainly influenced by bacterial virulence factors (e.g., flagella, pili, LPS/exopolysaccharide biosynthesis, motility) [ 7 ], cell surface traits (e.g., outer membrane proteins, hydrophobicity) [ 9 , 10 ], and quorum-sensing communication [ 11 ].…”