New Adapted In Vitro Technology to Evaluate Biofilm Formation and Antibiotic Activity Using Live Imaging under Flow Conditions

How to study biofilms: technological advancements in clinical biofilm research

Biofilm formation is an important survival strategy commonly used by bacteria and fungi, which are embedded in a protective extracellular matrix of organic polymers. They are ubiquitous in nature, including humans and other animals, and they can be surface- and non-surface-associated, making them capable of growing in and on many different parts of the body. Biofilms are also complex, forming polymicrobial communities that are difficult to eradicate due to their unique growth dynamics, and clinical infections associated with biofilms are a huge burden in the healthcare setting, as they are often difficult to diagnose and to treat. Our understanding of biofilm formation and development is a fast-paced and important research focus. This review aims to describe the advancements in clinical biofilm research, including both in vitro and in vivo biofilm models, imaging techniques and techniques to analyse the biological functions of the biofilm.

Antimicrobial Multidrug Resistance: Clinical Implications for Infection Management in Critically Ill Patients

The increasing incidence of antimicrobial resistance (AMR) worldwide represents a serious threat in the management of sepsis. Due to resistance to the most common antimicrobials prescribed, multidrug-resistant (MDR) pathogens have been associated with delays in adequate antimicrobial therapy leading to significant increases in mortality, along with prolonged hospital length of stay (LOS) and increases in healthcare costs. In response to MDR infections and the delay of microbiological results, broad-spectrum antibiotics are frequently used in empirical antimicrobial therapy. This can contribute to the overuse and misuse of antibiotics, further promoting the development of resistance. Multiple measures have been suggested to combat AMR. This review will focus on describing the epidemiology and trends concerning MDR pathogens. Additionally, it will explore the crucial aspects of identifying patients susceptible to MDR infections and optimizing antimicrobial drug dosing, which are both pivotal considerations in the fight against AMR. Expert commentary: The increasing AMR in ICUs worldwide makes the empirical antibiotic therapy challenging in septic patients. An AMR surveillance program together with improvements in MDR identification based on patient risk stratification and molecular rapid diagnostic tools may further help tailoring antimicrobial therapies and avoid unnecessary broad-spectrum antibiotics. Continuous infusions of antibiotics, therapeutic drug monitoring (TDM)-based dosing regimens and combination therapy may contribute to optimizing antimicrobial therapy and limiting the emergence of resistance.

How Can Omics Inform Diabetic Foot Ulcer Clinical Management? A Whole Genome Comparison of Four Clinical Strains of Staphylococcus aureus

Foot ulcers and associated infections significantly contribute to morbidity and mortality in diabetes. While diverse pathogens are found in the diabetes-related infected ulcers, Staphylococcus aureus remains one of the most virulent and widely prevalent pathogens. The high prevalence of S. aureus in chronic wound infections, especially in clinical settings, is attributed to its ability to evolve and acquire resistance against common antibiotics and to elicit an array of virulence factors. In this study, whole genome comparison of four strains of S. aureus (MUF168, MUF256, MUM270, and MUM475) isolated from diabetic foot ulcer (DFU) infections showing varying resistance patterns was carried out to study the genomic similarity, antibiotic resistance profiling, associated virulence factors, and sequence variations in drug targets. The comparative genome analysis showed strains MUM475 and MUM270 to be highly resistant, MUF256 with moderate levels of resistance, and MUF168 to be the least resistant. Strain MUF256 and MUM475 harbored more virulence factors compared with other two strains. Deleterious sequence variants were observed suggesting potential role in altering drug targets and drug efficacy. This comparative whole genome study offers new molecular insights that may potentially inform evidence-based diagnosis and treatment of DFUs in the clinic.

Antimicrobial activity of antibiotics on biofilm formed by Staphylococcus aureus and Pseudomonas aeruginosa in an open microfluidic model mimicking the diabetic foot environment

BACKGROUND

Diabetic foot infections (DFIs) represent a public health problem because of their frequency and the severity of their consequences, i.e. amputation and mortality. Polymicrobial biofilms on the skin surface of these ulcers complicate wound healing. Few in vitro models exist to study the antibiotics activity in this context.

OBJECTIVES

This study evaluated the in vitro activity of antibiotics against the two main bacteria isolated in DFI, Staphylococcus aureus and Pseudomonas aeruginosa, using a dynamic system (BioFlux™ 200) and a chronic wound-like medium (CWM) that mimic the foot ulcer environment.

METHODS

Reference strains and two pairs of clinical S. aureus and P. aeruginosa isolated together from a DFI were cultivated in brain heart infusion and CWM media during 72 h at 37°C, alone and combined in the BioFlux™ 200 system. Antibiotic activity was evaluated after a mechanical debridement. The activities were measured by the reduction of biofilm percentage of bacteria in the microfluidic system using microscopy.

RESULTS

Daptomycin for S. aureus and ceftazidime for P. aeruginosa showed excellent activity to reduce biofilm biomass, whereas linezolid action was more mitigated and dalbavancin was ineffective. Ceftazidime + daptomycin presented the most potent in vitro activity on a mixed biofilm.

CONCLUSIONS

The combination of CWM and the BioFlux™ microfluidic system represents a valuable tool to screen the potential antimicrobial activity of antibiotics under conditions mimicking those encountered in DFI. It could help clinicians in their management of chronic wounds.

Biofilms in Chronic Wound Infections: Innovative Antimicrobial Approaches Using the In Vitro Lubbock Chronic Wound Biofilm Model

Chronic wounds have harmful effects on both patients and healthcare systems. Wound chronicity is attributed to an impaired healing process due to several host and local factors that affect healing pathways. The resulting ulcers contain a wide variety of microorganisms that are mostly resistant to antimicrobials and possess the ability to form mono/poly-microbial biofilms. The search for new, effective and safe compounds to handle chronic wounds has come a long way throughout the history of medicine, which has included several studies and trials of conventional treatments. Treatments focus on fighting the microbial colonization that develops in the wound by multidrug resistant pathogens. The development of molecular medicine, especially in antibacterial agents, needs an in vitro model similar to the in vivo chronic wound environment to evaluate the efficacy of antimicrobial agents. The Lubbock chronic wound biofilm (LCWB) model is an in vitro model developed to mimic the pathogen colonization and the biofilm formation of a real chronic wound, and it is suitable to screen the antibacterial activity of innovative compounds. In this review, we focused on the characteristics of chronic wound biofilms and the contribution of the LCWB model both to the study of wound poly-microbial biofilms and as a model for novel treatment strategies.

Antibiofilm Properties of Antiseptic Agents Used on Pseudomonas aeruginosa Isolated from Diabetic Foot Ulcers

In diabetic foot ulcers (DFUs), biofilm formation is a major challenge that promotes wound chronicity and delays healing. Antiseptics have been proposed to combat biofilms in the management of DFUs. However, there is limited evidence on the activity of these agents against biofilms, and there are questions as to which agents have the best efficiency. Here, we evaluated the antibiofilm activity of sodium hypochlorite, polyvinylpyrrolidoneIodine (PVPI), polyhexamethylenebiguanide (PHMB) and octenidine against Pseudomonas aeruginosa strains using static and dynamic systems in a chronic-wound-like medium (CWM) that mimics the chronic wound environment. Using Antibiofilmogram®, a technology assessing the ability of antiseptics to reduce the initial phase of biofilm formation, we observed the significant activity of antiseptics against biofilm formation by P. aeruginosa (at 1:40 to 1:8 dilutions). Moreover, 1:100 to 1:3 dilutions of the different antiseptics reduced mature biofilms formed after 72 h by 10-log, although higher concentrations were needed in CWM (1:40 to 1:2). Finally, in the BioFlux200TM model, after biofilm debridement, sodium hypochlorite and PHMB were the most effective antiseptics. In conclusion, our study showed that among the four antiseptics tested, sodium hypochlorite demonstrated the best antibiofilm activity against P. aeruginosa biofilms and represents an alternative in the management of DFUs.

Polymicrobial Biofilm Organization of Staphylococcus aureus and Pseudomonas aeruginosa in a Chronic Wound Environment

Biofilm on the skin surface of chronic wounds is an important step that involves difficulties in wound healing. The polymicrobial nature inside this pathogenic biofilm is key to understanding the chronicity of the lesion. Few in vitro models have been developed to study bacterial interactions inside this chronic wound. We evaluated the biofilm formation and the evolution of bacteria released from this biofilm on the two main bacteria isolated in this condition, Staphylococcus aureus and Pseudomonas aeruginosa, using a dynamic system (BioFlux™ 200) and a chronic wound-like medium (CWM) that mimics the chronic wound environment. We observed that all species constituted a faster biofilm in the CWM compared to a traditional culture medium (p < 0.01). The percentages of biofilm formation were significantly higher in the mixed biofilm compared to those determined for the bacterial species alone (p < 0.01). Biofilm organization was a non-random structure where S. aureus aggregates were located close to the wound surface, whereas P. aeruginosa was located deeper in the wound bed. Planktonic biofilm-detached bacteria showed decreased growth, overexpression of genes encoding biofilm formation, and an increase in the mature biofilm biomass formed. Our data confirmed the impact of the chronic wound environment on biofilm formation and on bacterial lifecycle inside the biofilm.

The Multifunctional Role of Poloxamer P338 as a Biofilm Disrupter and Antibiotic Enhancer: A Small Step forward against the Big Trouble of Catheter-Associated Escherichia coli Urinary Tract Infections

Poloxamer 338 (P338), a nonionic surfactant amphiphilic copolymer, is herein proposed as an anti-biofilm compound for the management of catheter-associated urinary tract infections (CAUTIs). P338’s ability to disrupt Escherichia coli biofilms on silicone urinary catheters and to serve as antibiotic enhancer was evaluated for biofilm-producing E. coli Ec5FSL and Ec9FSL clinical strains, isolated from urinary catheters. In static conditions, quantitative biofilm formation assay allowed us to determine the active P338 concentration. In dynamic conditions, the BioFlux system, combined with confocal laser scanning microscopy, allowed us to investigate the P338 solution’s ability to detach biofilm, alone or in combination with sub-MIC concentrations of cefoxitin (FOX). The 0.5% P338 solution was able to destroy the structure of E. coli biofilms, to reduce the volume and area fraction covered by adherent cells (41.42 ± 4.79% and 56.20 ± 9.22% reduction for the Ec5FSL and Ec9FSL biofilms, respectively), and to potentiate the activity of 1\2 MIC FOX in disaggregating biofilms (19.41 ± 7.41% and 34.66 ± 3.75% reduction in the area fraction covered by biofilm for Ec5FSL and Ec9FSL, respectively) and killing cells (36.85 ± 7.13% and 32.33 ± 4.65% increase in the biofilm area covered by dead Ec5FSL and Ec9FSL cells, respectively).