Towards individualized diagnostics of biofilm-associated infections: a case study

Abstract

Organized within biofilm communities, bacteria exhibit resistance towards a broad spectrum of antibiotics. Thus, one might argue that bacteria isolated from biofilm-associated chronic infections should be subjected to resistance profiling under biofilm growth conditions. Various test systems have been developed to determine the biofilm-associated resistance; however, it is not clear to what extent the in vitro results reflect the situation in vivo, and whether the biofilm-resistance profile should guide clinicians in their treatment choice. To address this issue, we used confocal microscopy in combination with live/dead staining, and profiled biofilm-associated resistance of a large number (>130) of clinical Pseudomonas aeruginosa isolates from overall 15 cystic fibrosis patients. Our results demonstrate that in addition to a general non-responsiveness of bacteria when grown under biofilm conditions, there is an isolate-specific and antibiotic-specific biofilm-resistance profile. This individual resistance profile is independent on the structural properties of the biofilms. Furthermore, biofilm resistance is not linked to the resistance profile under planktonic growth conditions, or a mucoid, or small colony morphology of the tested isolates. Instead, it seems that individual biofilm structures evolve during biofilm-associated growth and are shaped by environment-specific cues. In conclusion, our results demonstrate that biofilm resistance profiles are isolate specific and cannot be deduced from commonly studied phenotypes. Further clinical studies will have to show the added value of biofilm-resistance profiling. Individualized diagnosis of biofilm resistance might lead to more rational recommendations for antimicrobial therapy and, thus, increased effectiveness of the treatment of chronically infected patients.

Breaking the Vicious Cycle of Antibiotic Killing and Regrowth of Biofilm-Residing Pseudomonas aeruginosa

“…The more efficient an antimicrobial therapy is, the more space it leaves for surviving bacteria to repopulate the empty niche. A similar fast repopulation of the biofilms might be the reason why in the clinic colistin treatment, despite being more effective in killing of biofilm cells (demonstrated here and before [37]), is not superior to an inhalative therapy with tobramycin (55-57). One might even argue that repeated killing and fast regrowth of the bacteria leave bacterial debris that may trigger a strong inflammatory response contributing to tissue destruction.…”

“…We tested colistin, which disrupts the outer membrane, and tobramycin, a well-known translational inhibitor. The biofilms were allowed to establish in flow chambers under continuous-flow conditions, and the antibiotic activity was monitored by following uptake of propidium iodide (PI), which is not permeant to live cells and thus has proved to be a reliable indicator of cell death (37)(38)(39)(40). For Fig.…”

Parallel evolutionary paths to produce more than one Pseudomonas aeruginosa biofilm phenotype

“…We have previously shown that clinical P. aeruginosa isolates from various patients and infectious sites exhibit very different in vitro biofilm structures. 40,41 In this study, we recorded the biofilm phenotypes of 414 clinical P. aeruginosa isolates by the use of confocal laser scanning microscopy (CLSM) following live/dead staining. Clinical isolates exhibited a large diversity of biofilm phenotypes; however, on the basis of visual inspection of microscopy images, we identified clusters of strains that share common structural characteristics (Fig.…”

Predicting antibiotic-associated virulence ofPseudomonas aeruginosausing anex-vivolung biofilm model

“…There is a drastic increase in antibiotic tolerance using biofilm-based diagnostics, such as the Calgary device, in comparison to MIC methods, demonstrating the limitation of using planktonic-based models for biofilm infections [7]. Some of these in vitro biofilm models are robust for antibiotic susceptibility screening; they fail to recapitulate the complexity of biofilm infections, environment and host-dependent interactions [6, 8], all of which affect the antibiotic susceptibility profile [8]. Also, these biofilm models have not been developed to demonstrate antibiotic susceptibility profile in multi-species infections.…”

“…Also, these biofilm models have not been developed to demonstrate antibiotic susceptibility profile in multi-species infections. Thus, if diagnostic tests fail to accurately detect in vivo antibiotic resistance, this will result in in recurrent and complicated infections [8], and may lead to a vicious cycle of increased resistance.…”