Real-time monitoring of Pseudomonas aeruginosa biofilm formation on endotracheal tubes in vitro

Abstract

BackgroundPseudomonas aeruginosa is an opportunistic bacterial pathogen responsible for both acute and chronic infections in humans. In particular, its ability to form biofilm, on biotic and abiotic surfaces, makes it particularly resistant to host’s immune defenses and current antibiotic therapies as well. Innovative antimicrobial materials, like hydrogel, silver salts or nanoparticles have been used to cover new generation catheters with promising results. Nevertheless, biofilm remains a major health problem. For instance, biofilm produced onto endotracheal tubes (ETT) of ventilated patients plays a relevant role in the onset of ventilation-associated pneumonia. Most of our knowledge on Pseudomonas aeruginosa biofilm derives from in vitro studies carried out on abiotic surfaces, such as polystyrene microplates or plastic materials used for ETT manufacturing. However, these approaches often provide underestimated results since other parameters, in addition to bacterial features (i.e. shape and material composition of ETT) might strongly influence biofilm formation.ResultsWe used an already established biofilm development assay on medically-relevant foreign devices (CVC catheters) by a stably transformed bioluminescent (BLI)-Pseudomonas aeruginosa strain, in order to follow up biofilm formation on ETT by bioluminescence detection. Our results demonstrated that it is possible: i) to monitor BLI-Pseudomonas aeruginosa biofilm development on ETT pieces in real-time, ii) to evaluate the three-dimensional structure of biofilm directly on ETT, iii) to assess metabolic behavior and the production of microbial virulence traits of bacteria embedded on ETT-biofilm.ConclusionsOverall, we were able to standardize a rapid and easy-to-perform in vitro model for real-time monitoring Pseudomonas aeruginosa biofilm formation directly onto ETT pieces, taking into account not only microbial factors, but also ETT shape and material. Our study provides a rapid method for future screening and validation of novel antimicrobial drugs as well as for the evaluation of novel biomaterials employed in the production of new classes of ETT.Electronic supplementary materialThe online version of this article (10.1186/s12866-018-1224-6) contains supplementary material, which is available to authorized users.

The β-Lactamase Inhibitor Boronic Acid Derivative SM23 as a New Anti-Pseudomonas aeruginosa Biofilm

“…The results shown in Figure 2 (left panel) indicated that the SM23, at the dose of 0.390 μM, was already able to significantly inhibit biofilm formation (about 40% of biofilm biomass), achieving its greatest effect in the dose range of 0.780-6.250 μM (about 50% of biomass reduction observed). Next, we analyzed the inhibitory effect of SM23 on biofilm, exploiting the bioluminescent properties of P. aeruginosa strain P1242, a model that allows to evaluate the effects of a given compound directly on the metabolically active biofilm (Pericolini et al, 2018). Thus, bacterial biofilm was allowed to form in 96-black well microtiter plates without or with SM23 at different concentrations.…”

“…We have recently described a rapid and easy-to-perform in vitro model for the real-time monitoring of P. aeruginosa biofilm formation on endotracheal tube (ETT) pieces (Pericolini et al, 2018). Accordingly, we evaluated the effect of SM23 on a 24 h-old Pseudomonas biofilm produced on ETT pieces.…”

Differential Efficacy of Two Dental Implant Decontamination Techniques in Reducing Microbial Biofilm and Re-Growth onto Titanium Disks In Vitro

“…By a recently established model assessing in real time microbial biofilm formation onto medical devices [27], here we show that BLI-Pseudomonas has the ability to adhere onto the titanium disks, thus rapidly forming a consistent biofilm on their surfaces within 24 h. Moreover, we provide the first evidence on the different efficacy of the two decontamination treatments, since Brush and BIC-40 are capable of impairing biofilm up to 76% and 99.9%, respectively. In particular, as evaluated by RLU analysis and subsequent conversion in CFU/disk, we show that microbial load is reduced of about 1 log following Brush treatment, while more than 3 logs decrease occurs upon BIC-40 treatment.…”

“…Moreover, we favor the hypothesis that the good performance of BIC-40 can also be related to the fact that sodium bicarbonate particles, remaining onto BIC-40-treated titanium disks [25], likely render the device surface hostile to subsequent microbial re-growth. In any case, using a BLI-based system that allows kinetic monitoring of microbial load onto medical devices [27], we have been able to show a different efficacy of the two decontamination procedures not only in impairing preformed biofilm but also in limiting subsequent re-growth onto titanium disks.…”

“…The set-up of new experimental models, such as the recently described use of an engineered laboratory strain of Pseudomonas aeruginosa (P. aeruginosa) to assess, in real time, biofilm formation onto medical devices [27], opens new pathways for a better comprehension of the events involved in microbial biofilm formation onto abiotic surfaces and its abatement by chemical and/or mechanical procedures.…”