ESCMID∗ guideline for the diagnosis and treatment of biofilm infections 2014

Aspect ratio of nano/microstructures determines Staphylococcus aureus adhesion on PET and titanium surfaces

AIMS

Joint infections cause premature implant failure. The avoidance of bacterial colonization of implant materials by modification of the material surface is therefore the focus of current research. In this in vitro study the complex interaction of periodic structures on PET and titanium surfaces on the adhesion of Staphylococcus aureus is analysed.

METHODS AND RESULTS

Using direct laser interference patterning as well as roll-to-roll hot embossing methods, structured periodic textures of different spatial distance were produced on surfaces and S. aureus were cultured for 24 h on these. The amount of adhering bacteria was quantified using fluorescence microscopy and the local adhesion behaviour was investigated using scanning electron microscopy. For PET structures, minimal bacterial adhesion was identified for an aspect ratio of about 0·02. On titanium structures, S. aureus adhesion was significantly decreased for profile heights of < 200 nm. Our results show a significantly decreased bacterial adhesion for structures with an aspect ratio range of 0·02 to 0·05.

CONCLUSIONS

We show that structuring on surfaces can decrease the amount of S. aureus on titanium and PET as common implant materials.

SIGNIFICANCE AND IMPACT OF THE STUDY

The study highlights the immense potential of applying specific structures to implant materials to prevent implant colonization with pathogen bacteria.

Indwelling Device-Associated Biofilms in Critically Ill Cancer Patients-Study Protocol

Health care-associated infections are a leading cause of inpatient complications. Rapid pathogen detection/identification is a major challenge in sepsis management that highly influences the successful outcome. The current standard of microorganism identification relies on bacterial growth in culture, which has several limitations. Gene sequencing research has developed culture-independent techniques for microorganism identification, with the aim to improve etiological diagnosis and, therefore, to change sepsis outcome. A prospective, observational, non-interventional, single-center study was designed that assesses biofilm-associated pathogens in a specific subpopulation of septic critically ill cancer patients. Indwelling device samples will be collected in septic patients at the moment of the removal of the arterial catheter, central venous catheter, endotracheal tube and urinary catheter. Concomitantly, clinical data regarding 4 sites (nasal, pharyngeal, rectal and skin) of pathogen colonization at the time of hospital/intensive care admission will be collected. The present study aims to offer new insights into biofilm-associated infections and to evaluate the infection caused by catheter-specific and patient-specific biofilm-associated pathogens in association with the extent of colonization. The analysis relies on the two following detection/identification techniques: standard microbiological method and next generation sequencing (NGS). Retrospectively, the study will estimate the clinical value of the NGS-based detection and its virtual potential in changing patient management and outcome, notably in the subjects with missing sepsis source or lack of response to anti-infective treatment.

Antimicrobial stewardship of antiseptics that are pertinent to wounds: the need for a united approach

Long before the nature of infection was recognized, or the significance of biofilms in delayed healing was understood, antimicrobial agents were being used in wound care. In the last 70 years, antibiotics have provided an effective means to control wound infection, but the continued emergence of antibiotic-resistant strains and the documented antibiotic tolerance of biofilms has reduced their effectiveness. A range of wound dressings containing an antimicrobial (antibiotic or non-antibiotic compound) has been developed. Whereas standardized methods for determining the efficacy of non-antibiotic antimicrobials in bacterial suspension tests were developed in the early twentieth century, standardized ways of evaluating the efficacy of antimicrobial dressings against microbial suspensions and biofilms are not available. Resistance to non-antibiotic antimicrobials and cross-resistance with antibiotics has been reported, but consensus on breakpoints is absent and surveillance is impossible. Antimicrobial stewardship is therefore in jeopardy. This review highlights these difficulties and in particular the efficacy of current non-antibiotic antimicrobials used in dressings, their efficacy, and the challenges of translating in vitro efficacy data to the efficacy of dressings in patients. This review calls for a unified approach to developing standardized methods of evaluating antimicrobial dressings that will provide an improved basis for practitioners to make informed choices in wound care.

Ex situ model of biofilm-associated wounds: providing a host-like environment for the study of Staphylococcus aureus and Pseudomonas aeruginosa biofilms

AIM

This study aimed to assess an ex situ model of biofilm-associated wounds on porcine skin for the study of Staphylococcus aureus and Pseudomonas aeruginosa biofilms in a host-like environment, after 48 to 120 h of incubation.

MATERIAL AND RESULTS

Ex situ and in vitro biofilms were comparatively analysed. Overall, CFU-counts and matrix quantification yielded significantly (P < 0·05) higher results for ex situ than in vitro biofilms. Confocal microscopy revealed greater (P < 0·05) biomass and thickness at 48-72 h and greater (P < 0·05) robustness at 72 h of growth. S. aureus ex situ biofilms produced less (P < 0·05) siderophore and proteases than in vitro biofilms, while P. aeruginosa ex situ biofilms produced more (P < 0·05) siderophores and less proteases than in vitro biofilms.

CONCLUSIONS

Biofilms grown ex situ present a greater amount of bacterial cells and polymeric matrix than their in vitro counterparts, reaching maturity at 72 h of growth. Moreover the production of virulence factors differs between ex situ and in vitro biofilms.

SIGNIFICANCE AND IMPACT OF THE STUDY

These findings emphasize the importance of using ex situ biofilm models, once they mimic in vivo conditions. The use of these models brings perspectives for the pursuit of therapeutic alternatives, as tests may be performed in a host-like environment.

Diagnosis of biofilm infections: current methods used, challenges and perspectives for the future

The diagnosis of biofilms continues to be a challenge, and there is no standardized protocol for such a diagnosis in clinical practice. In addition, some proposed methodologies are expensive to require significant amounts of time and a high number of trained staff, making them impracticable for clinical practice. In recent years, mass spectrophotometry/matrix-assisted laser desorption ionization time of flight (MALDI-TOF) has been applied it in biofilm studies. However, due to several problems and limitations of the technique, MALDI-TOF is far from being the gold standard for identifying biofilm formation. The omics analysis may prove to be a promising strategy for the diagnosis of biofilms in clinical laboratories since it allows the identification of pathogens in less time than needed for conventional techniques and in a more specific manner. However, omic tools are expensive and require qualified technical expertise, and an analysis of the data obtained needs to be careful not to neglect subpopulations in the biofilm. More studies must therefore be developed for creating a protocol that guarantees rapid biofilm identification, ensuring greater chances of success in infection control. This review discusses the current methods of microbial biofilm detection and future perspectives for its diagnosis in clinical practice.

Immune Responses to Pseudomonas aeruginosa Biofilm Infections

Pseudomonas aeruginosa is a key pathogen of chronic infections in the lungs of cystic fibrosis patients and in patients suffering from chronic wounds of diverse etiology. In these infections the bacteria congregate in biofilms and cannot be eradicated by standard antibiotic treatment or host immune responses. The persistent biofilms induce a hyper inflammatory state that results in collateral damage of the adjacent host tissue. The host fails to eradicate the biofilm infection, resulting in hindered remodeling and healing. In the present review we describe our current understanding of innate and adaptive immune responses elicited by P. aeruginosa biofilms in cystic fibrosis lung infections and chronic wounds. This includes the mechanisms that are involved in the activation of the immune responses, as well as the effector functions, the antimicrobial components and the associated tissue destruction. The mechanisms by which the biofilms evade immune responses, and potential treatment targets of the immune response are also discussed.

Biofilms by bacterial human pathogens: Clinical relevance - development, composition and regulation - therapeutical strategies

Notably, bacterial biofilm formation is increasingly recognized as a passive virulence factor facilitating many infectious disease processes. In this review we will focus on bacterial biofilms formed by human pathogens and highlight their relevance for diverse diseases. Along biofilm composition and regulation emphasis is laid on the intensively studied biofilms of Vibrio cholerae, Pseudomonas aeruginosa and Staphylococcus spp., which are commonly used as biofilm model organisms and therefore contribute to our general understanding of bacterial biofilm (patho-)physiology. Finally, therapeutical intervention strategies targeting biofilms will be discussed.

Self-Adaptation of Pseudomonas fluorescens Biofilms to Hydrodynamic Stress

In some conditions, bacteria self-organize into biofilms, supracellular structures made of a self-produced embedding matrix, mainly composed of polysaccharides, DNA, proteins, and lipids. It is known that bacteria change their colony/matrix ratio in the presence of external stimuli such as hydrodynamic stress. However, little is still known about the molecular mechanisms driving this self-adaptation. In this work, we monitor structural features of Pseudomonas fluorescens biofilms grown with and without hydrodynamic stress. Our measurements show that the hydrodynamic stress concomitantly increases the cell density population and the matrix production. At short growth timescales, the matrix mediates a weak cell-cell attractive interaction due to the depletion forces originated by the polymer constituents. Using a population dynamics model, we conclude that hydrodynamic stress causes a faster diffusion of nutrients and a higher incorporation of planktonic bacteria to the already formed microcolonies. This results in the formation of more mechanically stable biofilms due to an increase of the number of crosslinks, as shown by computer simulations. The mechanical stability also relies on a change in the chemical compositions of the matrix, which becomes enriched in carbohydrates, known to display adhering properties. Overall, we demonstrate that bacteria are capable of self-adapting to hostile hydrodynamic stress by tailoring the biofilm chemical composition, thus affecting both the mesoscale structure of the matrix and its viscoelastic properties that ultimately regulate the bacteria-polymer interactions.

Efficacy of a topical concentrated surfactant gel on microbial communities in non-healing diabetic foot ulcers with chronic biofilm infections: A proof-of-concept study

This proof‐of‐concept study sought to determine the effects of standard of care (SOC) and a topically applied concentrated surfactant gel (SG) on the total microbial load, community composition, and community diversity in non‐healing diabetic foot ulcers (DFUs) with chronic biofilm infections. SOC was provided in addition to a topical concentrated SG, applied every 2 days for 6 weeks. Wound swabs were obtained from the base of ulcers at baseline (week 0), week 1, mid‐point (week 3), and end of treatment (week 6). DNA sequencing and real‐time quantitative polymerase chain reaction (qPCR) were employed to determine the total microbial load, community composition, and diversity of patient samples. Tissue specimens were obtained at baseline and scanning electron microscopy and peptide nucleic acid fluorescent in situ hybridisation with confocal laser scanning microscopy were used to confirm the presence of biofilm in all 10 DFUs with suspected chronic biofilm infections. The application of SG resulted in 7 of 10 samples achieving a reduction in mean log10 total microbial load from baseline to end of treatment (0.8 Log10 16S copies, ±0.6), and 3 of 10 samples demonstrated an increase in mean Log10 total microbial load (0.6 log10 16S copies, ±0.8) from baseline to end of treatment. Composition changes in microbial communities were driven by changes to the most dominant bacteria. Corynebacterium sp. and Streptococcus sp. frequently reduced in relative abundance in patient samples from week 0 to week 6 but did not disappear. In contrast, Staphylococcus sp., Finegoldia sp., and Fusobacterium sp., relative abundances frequently increased in patient samples from week 0 to week 6. The application of a concentrated SG resulted in varying shifts to diversity (increase or decrease) between week 0 and week 6 samples at the individual patient level. Any shifts in community diversity were independent to changes in the total microbial loads. SOC and a topical concentrated SG directly affect the microbial loads and community composition of DFUs with chronic biofilm infections.

Sampling challenges in diagnosis of chronic bacterial infections

In recent decades there has been an increase in knowledge of the distribution, species diversity and growth patterns of bacteria in human chronic infections. This has challenged standard diagnostic methods, which have undergone a development to both increase the accuracy of testing as well as to decrease the occurrence of contamination. In particular, the introduction of new technologies based on molecular techniques into the clinical diagnostic process has increased detection and identification of infectious pathogens. Sampling is the first step in the diagnostic process, making it crucial for obtaining a successful outcome. However, sampling methods have not developed at the same speed as molecular identification. The heterogeneous distribution and potentially small number of pathogenic bacterial cells in chronic infected tissue makes sampling a complicated task, and samples must be collected judiciously and handled with care. Clinical sampling is a step in the diagnostic process that may benefit from innovative methods based on current knowledge of bacteria present in chronic infections. In the present review, we describe and discuss different aspects that complicate sampling of chronic infections. The purpose is to survey representative scientific work investigating the presence and distribution of bacteria in chronic infections in relation to various clinical sampling methods.

Can Leaves and Stems of Rubus idaeus L. Handle Candida albicans Biofilms?

Candida albicans is an opportunistic pathogen involved in many infections, especially linked to implanted medical devices. Its ability to form biofilms complicates the treatment of these infections as few molecules are active against sessile C. albicans. The aim of this study was to evaluate the potential of leaves, three-month-old and one-year-old stems of Rubus idaeus L. against C. albicans biofilm growth. Extractions with a polarity gradient were carried out on hydroacetonic extracts and followed by fractionation steps. The obtained extracts and fractions were tested for their anti-biofilm growth activity against C. albicans using XTT method. Compounds of active subfractions were identified by LC-MS. The hexane extracts from leaves and stems were the most active against the fungus with IC50 at 500 and 250 µg/mL. Their bioguided fractionation led to 4 subfractions with IC50 between 62.5 and 125 µg/mL. Most of the components identified in active subfractions were fatty acids and terpenoïds.

Biofilm Formation as a Complex Result of Virulence and Adaptive Responses of Helicobacter pylori

Helicobacter pylori is a bacterium that is capable of colonizing a host for many years, often for a lifetime. The survival in the gastric environment is enabled by the production of numerous virulence factors conditioning adhesion to the mucosa surface, acquisition of nutrients, and neutralization of the immune system activity. It is increasingly recognized, however, that the adaptive mechanisms of H. pylori in the stomach may also be linked to the ability of this pathogen to form biofilms. Initially, biofilms produced by H. pylori were strongly associated by scientists with water distribution systems and considered as a survival mechanism outside the host and a source of fecal-oral infections. In the course of the last 20 years, however, this trend has changed and now the most attention is focused on the biomedical aspect of this structure and its potential contribution to the therapeutic difficulties of H. pylori. Taking into account this fact, the aim of the current review is to discuss the phenomenon of H. pylori biofilm formation and present this mechanism as a resultant of the virulence and adaptive responses of H. pylori, including morphological transformation, membrane vesicles secretion, matrix production, efflux pump activity, and intermicrobial communication. These mechanisms will be considered in the context of transcriptomic and proteomic changes in H. pylori biofilms and their modulating effect on the development of this complex structure.

Groin dissections in skin cancer: Effect of a change in prophylactic antibiotic protocol

OBJECTIVES

To determine whether groin dissection surgical site infection (SSI) incidence changed with shorter post-operative antibiotic prophylaxis.

BACKGROUND

Post-operative prophylaxis changed due to antimicrobial stewardship, from regular oral antibiotics until drain removal, to three intravenous doses. Both groups had a single intravenous dose at induction.

METHODS

A prospective database of groin dissections for metastatic skin cancer was retrospectively reviewed for SSI according to Public Health England criteria. Eighty groin dissections in 79 consecutive patients were included: 40 had oral antibiotics until drain removal [mean 26±7 (range 19-36) days] and 39 had three post-operative intravenous doses.

RESULTS

Longer prophylaxis was associated with lower SSI incidence [10 (25%) versus 21 (54%), odds ratio (OR) 3.50, 95% confidence interval (CI) 1.34-9.08, p = 0.009], fewer deep infections [5 (13%) versus 16 (41%), OR 4.89, 95% CI 1.57-15.13, p = 0.004], fewer readmissions for infection [5 (13%) versus 15 (38%), OR 4.38, 95% CI 1.40-13.65, p = 0.008], but similar seroma incidence [18 (45%) versus 16 (41%), OR 0.85, 95% CI 0.35-2.07, p = 0.72] and wound dehiscence [7 (18%) versus 5 (13%), OR 0.69, 95% CI 0.20-2.40, p = 0.56]. BMI ≥30 (n = 21) was associated with SSI, occurring in 13 of 21 (62%) (OR 3.859, 95% CI 1.34-11.10, p = 0.01). Median infection onset was 22 days (IQR 12-27) versus 17 (IQR 13-22), (p = 0.53). Multiple organisms were cultured in 21 of 31 (68%) patients with positive microbiological samples.

CONCLUSIONS

SSI rates doubled with shorter prophylaxis; deep infections and readmissions for infection tripled. Obesity was independently associated with infection. Seroma and wound dehiscence incidence were unchanged. Infections mainly occurred in the third week after surgery and were polymicrobial.

Screening of FDA-Approved Drugs Using a 384-Well Plate-Based Biofilm Platform: The Case of Fingolimod

In an effort to find new repurposed antibacterial compounds, we performed the screening of an FDA-approved compounds library against Staphylococcus aureus American Type Culture Collection (ATCC) 25923. Compounds were evaluated for their capacity to prevent both planktonic growth and biofilm formation as well as to disrupt pre-formed biofilms. One of the identified initial hits was fingolimod (FTY720), an immunomodulator approved for the treatment of multiple sclerosis, which was then selected for follow-up studies. Fingolimod displayed a potent activity against S. aureus and S. epidermidis with a minimum inhibitory concentration (MIC) within the range of 12–15 µM at which concentration killing of all the bacteria was confirmed. A time–kill kinetic study revealed that fingolimod started to drastically reduce the viable bacterial count within two hours and we showed that no resistance developed against this compound for up to 20 days. Fingolimod also displayed a high activity against Acinetobacter baumannii (MIC 25 µM) as well as a modest activity against Escherichia coli and Pseudomonas aeruginosa. In addition, fingolimod inhibited quorum sensing in Chromobacterium violaceum and might therefore target this signaling pathway in certain Gram-negative bacteria. In conclusion, we present the identification of fingolimod from a compound library and its evaluation as a potential repurposed antibacterial compound.

Evaluation of Staphylococcal Bacteriophage Sb-1 as an Adjunctive Agent to Antibiotics Against Rifampin-Resistant Staphylococcus aureus Biofilms

Rifampin plays a crucial role in the treatment of staphylococcal implant-associated infection, as it is the only antibiotic capable of eradicating Staphylococcus aureus biofilms. However, the emergence of rifampin resistance strongly limits its use. Combinatorial therapy of antibiotics and bacteriophages may represent a strategy to overcome the resistance. Here, we evaluated the activity of staphylococcal bacteriophage Sb-1 in combination with different antibiotics against the biofilms of 10 rifampin-resistant S. aureus clinical strains, including MRSA and MSSA. S. aureus biofilms formed on porous glass beads were exposed to antibiotics alone or combined with Sb-1 simultaneously or staggered (first Sb-1 for 24 h followed by antibiotic). Recovered bacteria were detected by measuring growth-related heat production at 37°C (isothermal microcalorimetry) and the biofilm eradication was assessed by sonication of beads and plating of the resulting sonication fluid. Minimum biofilm eradication concentration (MBEC) was defined as the lowest concentration of antibiotic required to kill all adherent bacteria, resulting in absence of growth after plating the sonication fluid. Tested antibiotics presented high MBEC values when administered alone (64 to > 1,024 μg/ml). The simultaneous or staggered combination of Sb-1 with daptomycin showed the highest activity against all MRSA biofilms, whereas the exposure to Sb-1 with vancomycin showed no improved anti-biofilm activity. Staggered administration of Sb-1 and flucloxacillin, cefazolin, or fosfomycin improved the antibiofilm activity in four out of six MSSA, whereas simultaneous exposure exhibited similar or lesser synergy. In conclusion, the combinatorial effect of Sb-1 and antibiotics enabled to eradicate rifampin-resistant S. aureus biofilms in vitro.

Staphylococcus epidermidis Biofilms Have a High Tolerance to Antibiotics in Periprosthetic Joint Infection

Both Staphylococcus aureus and Staphylococcus epidermidis are commonly associated with periprosthetic joint infections (PJIs). The treatment of PJI can be challenging because biofilms are assumed to have an increased intolerance to antibiotics. This makes the treatment of PJI challenging from a clinical perspective. Although S. aureus has been previously demonstrated to have increased biofilm antibiotic tolerance, this has not been well established with Staphylococcus epidermidis. A prospective registry of PJI S. epidermidis isolates was developed. The efficacy of clinically relevant antibiotics was quantified against these isolates. S. epidermidis planktonic minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were collected using clinical laboratory standard index (CLSI) assays for eight antibiotics (doxycycline, vancomycin, daptomycin, clindamycin, rifampin, nafcillin, and trimethoprim/sulfamethoxazole). Mature biofilms were grown in vitro, after which minimum biofilm inhibitory concentration (MBIC) and minimum biofilm bactericidal concentration (MBBC) were quantified. Only rifampin and doxycycline had a measurable MBIC across all tested isolates. Based on MBBC, 64% of S. epidermidis biofilms could be eliminated by rifampin, whereas only 18% by doxycycline. S. epidermidis biofilm was observed to have a high tolerance to antibiotics as compared to planktonic culture. Isolate biofilm antibiotic tolerance varied to a larger degree than was seen in planktonic cultures.

Biofilm exacerbates antibiotic resistance: Is this a current oversight in antimicrobial stewardship?

Objective

To raise awareness of the role of environmental biofilm in the emergence and spread of antibiotic resistance and its consideration in antimicrobial stewardship.

Background

Antibiotic resistance is a major threat to public health. Overuse of antibiotics, increased international travel, and genetic promiscuity amongst bacteria have contributed to antibiotic resistance, and global containment efforts have so far met with limited success. Antibiotic resistance is a natural mechanism by which bacteria have adapted to environmental threats over billions of years and is caused either by genetic mutations or by horizontal gene transfer. Another ancient survival strategy involves bacteria existing within a self-produced polymeric matrix, which today is termed biofilm. Biofilm similarly enables bacterial tolerance to environmental threats, and also encourages the transfer of antibiotic resistance genes between bacterial species. This natural and ubiquitous mode of bacterial life has not been considered amongst strategies to tackle antibiotic resistance in healthcare facilities, despite its ability to significantly enhance bacterial survival and persistence, and to encourage antibiotic resistance.

Conclusion

Biofilm must be considered synonymously with antibiotic resistance because of its proficiency in transferring resistance genes as well as its innate phenotypic tolerance to antibiotics. Although biofilm falls outside of the current definition of antimicrobial stewardship, greater awareness of the existence, ubiquity, and consequences of environmental biofilm amongst healthcare practitioners is crucial to improving hygiene practices and controlling the emergence and spread of antibiotic resistance in healthcare facilities.

Biofilms in Diabetic Foot Ulcers: Significance and Clinical Relevance

Foot infections are the main disabling complication in patients with diabetes mellitus. These infections can lead to lower-limb amputation, increasing mortality and decreasing the quality of life. Biofilm formation is an important pathophysiology step in diabetic foot ulcers (DFU)-it plays a main role in the disease progression and chronicity of the lesion, the development of antibiotic resistance, and makes wound healing difficult to treat. The main problem is the difficulty in distinguishing between infection and colonization in DFU. The bacteria present in DFU are organized into functionally equivalent pathogroups that allow for close interactions between the bacteria within the biofilm. Consequently, some bacterial species that alone would be considered non-pathogenic, or incapable of maintaining a chronic infection, could co-aggregate symbiotically in a pathogenic biofilm and act synergistically to cause a chronic infection. In this review, we discuss current knowledge on biofilm formation, its presence in DFU, how the diabetic environment affects biofilm formation and its regulation, and the clinical implications.

Antimicrobial Hypochlorous Wound Irrigation Solutions Demonstrate Lower Anti-biofilm Efficacy Against Bacterial Biofilm in a Complex in-vitro Human Plasma Biofilm Model (hpBIOM) Than Common Wound Antimicrobials

Biofilms pose a relevant factor for wound healing impairment in chronic wounds. With 78% of all chronic wounds being affected by biofilms, research in this area is of high priority, especially since data for evidence-based selection of appropriate antimicrobials and antiseptics is scarce. Therefore, the objective of this study was to evaluate the anti-biofilm efficacy of commercially available hypochlorous wound irrigation solutions compared to established antimicrobials. Using an innovative complex in-vitro human plasma biofilm model (hpBIOM), quantitative reduction of Pseudomonas aeruginosa, Staphylococcus aureus, and Methicillin-resistant S. aureus (MRSA) biofilms by three hypochlorous irrigation solutions [two <0.08% and one 0.2% sodium hypochlorite (NaClO)] was compared to a 0.04% polyhexanide (PHMB) irrigation solution and 0.1% octenidine-dihydrochloride/phenoxyethanol (OCT/PE). Efficacy was compared to a non-challenged planktonic approach, as well as with increased substance volume over a prolonged exposure (up to 72 h). Qualitative visualization of biofilms was performed by scanning electron microscopy (SEM). Both reference agents (OCT/PE and PHMB) induced significant biofilm reductions within 72 h, whereby high volume OCT/PE even managed complete eradication of P. aeruginosa and MRSA biofilms after 72 h. The tested hypochlorous wound irrigation solutions achieved no relevant penetration and eradication of biofilms despite increased volume and exposure. Only 0.2% NaClO managed a low reduction under prolonged exposure. The results demonstrate that low-dosed hypochlorous wound irrigation solutions are significantly less effective than PHMB-based irrigation solution and OCT/PE, thus unsuitable for biofilm eradication on their own. The used complex hpBIOM thereby mimics the highly challenging clinical wound micro-environment, providing a more profound base for future clinical translation.

Bacteriophage Infections of Biofilms of Health Care-Associated Pathogens: Klebsiella pneumoniae

Members of the family Enterobacteriaceae, such as Klebsiella pneumoniae, are considered both serious and urgent public health threats. Biofilms formed by these health care-associated pathogens can lead to negative and costly health outcomes. The global spread of antibiotic resistance, coupled with increased tolerance to antimicrobial treatments in biofilm-associated bacteria, highlights the need for novel strategies to overcome treatment hurdles. Bacteriophages (phages), or viruses that infect bacteria, have reemerged as one such potential strategy. Virulent phages are capable of infecting and killing their bacterial hosts, in some cases producing depolymerases that are able to hydrolyze biofilms. Phage therapy does have its limitations, however, including potential narrow host ranges, development of bacterial resistance to infection, and the potential spread of phage-encoded virulence genes. That being said, advances in phage isolation, screening, and genome sequencing tools provide an upside in overcoming some of these limitations and open up the possibilities of using phages as effective biofilm control agents.

Selective digestive decontamination solution used as "lock therapy" prevents and eradicates bacterial biofilm in an in vitro bench-top model

Background

Most preventing measures for reducing ventilator-associated pneumonia (VAP) are based mainly on the decolonization of the internal surface of the endotracheal tubes (ETTs). However, it has been demonstrated that bacterial biofilm can also be formed on the external surface of ETTs. Our objective was to test in vitro the efficacy of selective digestive decontamination solution (SDDs) onto ETT to prevent biofilm formation and eradicate preformed biofilms of three different microorganisms of VAP.

Methods

We used an in vitro model in which we applied, at the subglottic space of ETT, biofilms of either P. aeruginosa ATCC 15442, or E. coli ATCC 25922, or S. aureus ATCC 29213, and the SDDs at the same time (prophylaxis) or after 72 h of biofilm forming (treatment). ETT were incubated during 5 days with a regimen of 2 h-locks. ETT fragments were analyzed by sonication and confocal laser scanning microscopy to calculate the percentage reduction of cfu and viable cells, respectively.

Results

Median (IQR) percentage reduction of live cells and cfu/ml counts after treatment were, respectively, 53.2% (39.4%—64.1%) and 100% (100%–100.0%) for P. aeruginosa, and 67.9% (46.7%–78.7%) and 100% (100%–100.0%) for E. coli. S. aureus presented a complete eradication by both methods. After prophylaxis, there were absence of live cells and cfu/ml counts for all microorganisms.

Conclusions

SDDs used as “lock therapy” in the subglottic space is a promising prophylactic approach that could be used in combination with the oro-digestive decontamination procedure in the prevention of VAP.

Efficacy of a ciprofloxacin/amikacin combination against planktonic and biofilm cultures of susceptible and low-level resistant Pseudomonas aeruginosa

BACKGROUND

Eradicating bacterial biofilm without mechanical dispersion remains a challenge. Combination therapy has been suggested as a suitable strategy to eradicate biofilm.

OBJECTIVES

To evaluate the efficacy of a ciprofloxacin/amikacin combination in a model of in vitro Pseudomonas aeruginosa biofilm.

METHODS

The antibacterial activity of ciprofloxacin and amikacin (alone, in combination and successively) was evaluated by planktonic and biofilm time-kill assays against five P. aeruginosa strains: PAO1, a WT clinical strain and three clinical strains overexpressing the efflux pumps MexAB-OprM (AB), MexXY-OprM (XY) and MexCD-OprJ (CD), respectively. Amikacin MIC was 16 mg/L for XY and ciprofloxacin MIC was 0.5 mg/L for CD. The other strains were fully susceptible to ciprofloxacin and amikacin. The numbers of total and resistant cells were determined.

RESULTS

In planktonic cultures, regrowth of high-level resistant mutants was observed when CD was exposed to ciprofloxacin alone and XY to amikacin alone. Eradication was obtained with ciprofloxacin or amikacin in the other strains, or with the combination in XY and CD strains. In biofilm, bactericidal reduction after 8 h followed by a mean 4 log10 cfu/mL plateau in all strains and for all regimens was noticed. No regrowth of resistant mutants was observed whatever the antibiotic regimen. The bacterial reduction obtained with a second antibiotic used simultaneously or consecutively was not significant.

CONCLUSIONS

The ciprofloxacin/amikacin combination prevented the emergence of resistant mutants in low-level resistant strains in planktonic cultures. Biofilm persister cells were not eradicated, either with monotherapy or with the combination.

In vitro activity of ceftolozane-tazobactam and ceftazidime-avibactam against Pseudomonas aeruginosa isolated from patients with cystic fibrosis

Pseudomonas aeruginosa is a commonly isolated pathogen in adults with cystic fibrosis (CF). Antimicrobial resistance is an escalating problem due to chronic colonization and frequent antimicrobial exposure. Ceftolozane-tazobactam (C/T) and ceftazidime-avibactam (CZA) exhibit promising activity against antimicrobial resistant organisms, including P. aeruginosa. A retrospective review was conducted comparing the in vitro activities of C/T and CZA against 42 P. aeruginosa isolates from the respiratory tract of 32 adults with CF. The first isolate per patient per year that underwent susceptibility testing for C/T, CZA, and colistin was included. C/T was more susceptible than CZA (60% versus 43%). Thirty-eight (90%) isolates were considered highly drug resistant and demonstrated higher C/T susceptibilities compared to CZA (55% versus 45%). These results suggest using C/T while awaiting susceptibilities when standard antipseudomonal agents cannot be used.

Bacterial aggregate size determines phagocytosis efficiency of polymorphonuclear leukocytes

The ability of bacteria to aggregate and form biofilms impairs phagocytosis by polymorphonuclear leukocytes (PMNs). The aim of this study was to examine if the size of aggregates is critical for successful phagocytosis and how bacterial biofilms evade phagocytosis. We investigated the live interaction between PMNs and Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli and Staphylococcus epidermidis using confocal scanning laser microscopy. Aggregate size significantly affected phagocytosis outcome and larger aggregates were less likely to be phagocytized. Aggregates of S. epidermidis were also less likely to be phagocytized than equally-sized aggregates of the other three species. We found that only aggregates of approx. 5 μm diameter or smaller were consistently phagocytosed. We demonstrate that planktonic and aggregated cells of all four species significantly reduced the viability of PMNs after 4 h of incubation. Our results indicate that larger bacterial aggregates are less likely to be phagocytosed by PMNs and we propose that, if the aggregates become too large, circulating PMNs may not be able to phagocytose them quickly enough, which may lead to chronic infection.

The effect of Cyclic-di-GMP on biofilm formation by Pseudomonas aeruginosa in a novel empyema model

Background

Pseudomonas aeruginosa (P. aeruginosa) is a common pathogenic bacterium which causes pleural empyema, and infection of P. aeruginosa is often associated with biofilm. The aim of this study was to establish a model of rabbit empyema infected by P. aeruginosa to determine whether it causes the formation of biofilm in the pleural cavity. Furthermore, we investigated the effect of cyclic diguanosine monophosphate (c-di-GMP) on biofilm formation in this P. aeruginosa empyema model.

Methods

Twenty rabbits were used and randomly divided into five groups: PAO1, PAO1ΔwspF, and PAO1/p_lac-yhjH infection groups, and Luria-Bertani (LB) broth and turpentine control groups. A drainage catheter was implanted into the pleural cavity through thoracentesis. The three infection groups were respectively infected with PAO1, PAO1ΔwspF, and PAO1/p_lac-yhjH strains, which caused empyema. The two control groups were injected with LB or turpentine. After 4 days of infection, we sacrificed the rabbits. We evaluated the pathology of pleura through hematoxylin-eosin staining. Colony count and crystal violet assay were used to analyze the biofilm formation on the surface of catheters. Scanning electron was used to observe the biofilm on the surface of the pleura. Peptide nucleic acids-fluorescence in situ hybridization (PNA-FISH) was used to observe the biofilm in the fibrinous deposition.

Results

By the PNA-FISH assay, biofilms were observed in the fibrinous deposition of the three infection groups. The red fluorescence area of the PAO1ΔwspF infection group was larger than that of the PAO1 and PAO1/p_lac-yhjH infection groups. Through electron microscopy, we observed that PAO1 strains were embedded in an electron-dense extracellular matrix on the surface of pleural tissue, and appeared to be biofilm-like structures. For the crystal violet assay, the optical density values of different groups were significantly different: PAO1ΔwspF > PAO1 > PAO1/p_lac-yhjH > control groups (P<0.05).

Conclusions

To the best knowledge of the authors, this is the first study to report P. aeruginosa forming biofilm in a novel animal model of pleural empyema. In addition, c-di-GMP signaling molecules played an important role in biofilm formation in the pleural cavity.

Targeting Biofilms Therapy: Current Research Strategies and Development Hurdles

Biofilms are aggregate of microorganisms in which cells are frequently embedded within a self-produced matrix of extracellular polymeric substance (EPS) and adhere to each other and/or to a surface. The development of biofilm affords pathogens significantly increased tolerances to antibiotics and antimicrobials. Up to 80% of human bacterial infections are biofilm-associated. Dispersal of biofilms can turn microbial cells into their more vulnerable planktonic phenotype and improve the therapeutic effect of antimicrobials. In this review, we focus on multiple therapeutic strategies that are currently being developed to target important structural and functional characteristics and drug resistance mechanisms of biofilms. We thoroughly discuss the current biofilm targeting strategies from four major aspects—targeting EPS, dispersal molecules, targeting quorum sensing, and targeting dormant cells. We explain each aspect with examples and discuss the main hurdles in the development of biofilm dispersal agents in order to provide a rationale for multi-targeted therapy strategies that target the complicated biofilms. Biofilm dispersal is a promising research direction to treat biofilm-associated infections in the future, and more in vivo experiments should be performed to ensure the efficacy of these therapeutic agents before being used in clinic.

Self-targeting, zwitterionic micellar dispersants enhance antibiotic killing of infectious biofilms-An intravital imaging study in mice

Extracellular polymeric substances (EPS) hold infectious biofilms together and limit antimicrobial penetration and clinical infection control. Here, we present zwitterionic micelles as a previously unexplored, synthetic self-targeting dispersant. First, a pH-responsive poly(ε-caprolactone)-block-poly(quaternary-amino-ester) was synthesized and self-assembled with poly(ethylene glycol)-block-poly(ε-caprolactone) to form zwitterionic, mixed-shell polymeric micelles (ZW-MSPMs). In the acidic environment of staphylococcal biofilms, ZW-MSPMs became positively charged because of conversion of the zwitterionic poly(quaternary-amino-ester) to a cationic lactone ring. This allowed ZW-MSPMs to self-target, penetrate, and accumulate in staphylococcal biofilms in vitro. In vivo biofilm targeting by ZW-MSPMs was confirmed for staphylococcal biofilms grown underneath an implanted abdominal imaging window through direct imaging in living mice. ZW-MSPMs interacted strongly with important EPS components such as eDNA and protein to disperse biofilm and enhance ciprofloxacin efficacy toward remaining biofilm, both in vitro and in vivo. Zwitterionic micellar dispersants may aid infection control and enhance efficacy of existing antibiotics against remaining biofilm.

Pathological and microbiological impact of a gentamicin-loaded biocomposite following limited or extensive debridement in a porcine model of osteomyelitis

Aims

CERAMENT|G is an absorbable gentamicin-loaded biocomposite used as an on-site vehicle of antimicrobials for the treatment of chronic osteomyelitis. The purpose of the present study was to investigate the sole effect of CERAMENT|G, i.e. without additional systemic antimicrobial therapy, in relation to a limited or extensive debridement of osteomyelitis lesions in a porcine model.

Methods

Osteomyelitis was induced in nine pigs by inoculation of 10⁴ colony-forming units (CFUs) of Staphylococcus aureus into a drill hole in the right tibia. After one week, the pigs were allocated into three groups. Group A (n = 3) received no treatment during the study period (19 days). Groups B (n = 3) and C (n = 3) received limited or extensive debridement seven days postinoculation, respectively, followed by injection of CERAMENT|G into the bone voids. The pigs were euthanized ten (Group C) and 12 (Group B) days after the intervention.

Results

All animals presented confirmatory signs of bone infection post-mortem. The estimated amount of inflammation was substantially greater in Groups A and B compared to Group C. In both Groups B and C, peptide nucleic acid fluorescence in situ hybridization (PNA FISH) of CERAMENT|G and surrounding bone tissue revealed bacteria embedded in an opaque matrix, i.e. within biofilm. In addition, in Group C, the maximal measured post-mortem gentamicin concentrations in CERAMENT|G and surrounding bone tissue samples were 16.6 μg/ml and 6.2 μg/ml, respectively.

Conclusion

The present study demonstrates that CERAMENT|G cannot be used as a standalone alternative to extensive debridement or be used without the addition of systemic antimicrobials.

Cite this article: Bone Joint Res 2020;9(7):394–401.

Anti-biofilm efficacy of a medieval treatment for bacterial infection requires the combination of multiple ingredients

Novel antimicrobials are urgently needed to combat drug-resistant bacteria and to overcome the inherent difficulties in treating biofilm-associated infections. Studying plants and other natural materials used in historical infection remedies may enable further discoveries to help fill the antibiotic discovery gap. We previously reconstructed a 1,000-year-old remedy containing onion, garlic, wine, and bile salts, known as 'Bald's eyesalve', and showed it had promising antibacterial activity. In this current paper, we have found this bactericidal activity extends to a range of Gram-negative and Gram-positive wound pathogens in planktonic culture and, crucially, that this activity is maintained against Acinetobacter baumannii, Stenotrophomonas maltophilia, Staphylococcus aureus, Staphylococcus epidermidis and Streptococcus pyogenes in a soft-tissue wound biofilm model. While the presence of garlic in the mixture can explain the activity against planktonic cultures, garlic has no activity against biofilms. We have found the potent anti-biofilm activity of Bald's eyesalve cannot be attributed to a single ingredient and requires the combination of all ingredients to achieve full activity. Our work highlights the need to explore not only single compounds but also mixtures of natural products for treating biofilm infections and underlines the importance of working with biofilm models when exploring natural products for the anti-biofilm pipeline.

The evolutionary trajectories of P. aeruginosa in biofilm and planktonic growth modes exposed to ciprofloxacin: beyond selection of antibiotic resistance

Ciprofloxacin (CIP) is used to treat Pseudomonas aeruginosa biofilm infections. We showed that the pathways of CIP-resistance development during exposure of biofilms and planktonic P. aeruginosa populations to subinhibitory levels of CIP depend on the mode of growth. In the present study, we analyzed CIP-resistant isolates obtained from previous evolution experiments, and we report a variety of evolved phenotypic and genotypic changes that occurred in parallel with the evolution of CIP-resistance. Cross-resistance to beta-lactam antibiotics was associated with mutations in genes involved in cell-wall recycling (ftsZ, murG); and could also be explained by mutations in the TCA cycle (sdhA) genes and in genes involved in arginine catabolism. We found that CIP-exposed isolates that lacked mutations in quorum-sensing genes and acquired mutations in type IV pili genes maintained swarming motility and lost twitching motility, respectively. Evolved CIP-resistant isolates showed high fitness cost in planktonic competition experiments, yet persisted in the biofilm under control conditions, compared with ancestor isolates and had an advantage when exposed to CIP. Their persistence in biofilm competition experiments in spite of their fitness cost in planktonic growth could be explained by their prolonged lag-phase. Interestingly, the set of mutated genes that we identified in these in vitro-evolved CIP-resistant colonies, overlap with a large number of patho-adaptive genes previously reported in P. aeruginosa isolates from cystic fibrosis (CF) patients. This suggests that the antibiotic stress is contributing to the bacterial evolution in vivo, and that adaptive laboratory evolution can be used to predict the in vivo evolutionary trajectories.

The Arginine Deiminase Pathway Impacts Antibiotic Tolerance during Biofilm-Mediated Streptococcus pyogenes Infections

Bacterial biofilms are responsible for a variety of serious human infections and are notoriously difficult to treat due to their recalcitrance to antibiotics. Further work is necessary to elicit a full understanding of the mechanism of this antibiotic tolerance. The arginine deiminase (ADI) pathway is responsible for bacterial pH maintenance and is highly expressed during biofilm growth in multiple bacterial species. Using the group A Streptococcus (GAS) as a model human pathogen, the ADI pathway was demonstrated to contribute to biofilm growth. The inability of antibiotics to reduce GAS populations when in a biofilm was demonstrated by in vitro studies and a novel animal model of nasopharyngeal infection. However, disruption of the ADI pathway returned GAS biofilms to planktonic levels of antibiotic sensitivity, suggesting the ADI pathway is influential in biofilm-related antibiotic treatment failure and provides a new strategic target for the treatment of biofilm infections in GAS and potentially numerous other bacterial species.IMPORTANCE Biofilm-mediated bacterial infections are a major threat to human health because of their recalcitrance to antibiotic treatment. Through the study of Streptococcus pyogenes, a significant human pathogen that is known to form antibiotic-tolerant biofilms, we demonstrated the role that a bacterial pathway known for responding to acid stress plays in biofilm growth and antibiotic tolerance. This not only provides some insight into antibiotic treatment failure in S. pyogenes infections but also, given the widespread nature of this pathway, provides a potentially broad target for antibiofilm therapies. This discovery has the potential to impact the treatment of many different types of recalcitrant biofilm infections.

A review of iodine-based compounds, with a focus on biofilms: results of an expert panel

Biofilms play a central role in the chronicity of non-healing lesions such as venous leg ulcers and diabetic foot ulcers. Therefore, biofilm management and treatment is now considered an essential part of wound care. Many antimicrobial treatments, whether topical or systemic, have been shown to have limited efficacy in the treatment of biofilm phenotypes. The antimicrobial properties of iodine compounds rely on multiple and diverse interactions to exert their effects on microorganisms. An expert panel, held in Las Vegas during the autumn Symposium on Advanced Wound Care meeting in 2018, discussed these properties, with the focus on iodine and iodophors and their effects on biofilm prevention and treatment.

Patient genetics is linked to chronic wound microbiome composition and healing

The clinical importance of microbiomes to the chronicity of wounds is widely appreciated, yet little is understood about patient-specific processes shaping wound microbiome composition. Here, a two-cohort microbiome-genome wide association study is presented through which patient genomic loci associated with chronic wound microbiome diversity were identified. Further investigation revealed that alternative TLN2 and ZNF521 genotypes explained significant inter-patient variation in relative abundance of two key pathogens, Pseudomonas aeruginosa and Staphylococcus epidermidis. Wound diversity was lowest in Pseudomonas aeruginosa infected wounds, and decreasing wound diversity had a significant negative linear relationship with healing rate. In addition to microbiome characteristics, age, diabetic status, and genetic ancestry all significantly influenced healing. Using structural equation modeling to identify common variance among SNPs, six loci were sufficient to explain 53% of variation in wound microbiome diversity, which was a 10% increase over traditional multiple regression. Focusing on TLN2, genotype at rs8031916 explained expression differences of alternative transcripts that differ in inclusion of important focal adhesion binding domains. Such differences are hypothesized to relate to wound microbiomes and healing through effects on bacterial exploitation of focal adhesions and/or cellular migration. Related, other associated loci were functionally enriched, often with roles in cytoskeletal dynamics. This study, being the first to identify patient genetic determinants for wound microbiomes and healing, implicates genetic variation determining cellular adhesion phenotypes as important drivers of infection type. The identification of predictive biomarkers for chronic wound microbiomes may serve as risk factors and guide treatment by informing patient-specific tendencies of infection.

Chronic, or non-healing, wounds represent a costly burden to patients, and bacterial infection of wounds is an important driver of chronicity. A variety of bacterial species often occur in chronic wounds, but it is unknown why certain species are observed in some wound infections and not others. In this study, genetic variation of wound clinic patients was compared to the bacteria observed in their infected wounds. Through these comparisons, genetic variation in the TLN2 and ZNF521 genes was found to be associated with both the number of bacteria observed in wounds and the abundance of common pathogens (primarily Pseudomonas aeruginosa and Staphylococcus epidermidis). Moreover, Pseudomonas infected wounds were found to have fewer species present and wounds with fewer species were slower to heal. Furthermore, patient genes associated with microbiomes commonly encode proteins known to be important for cellular structures important to healing and to which bacteria directly interact. Experimental investigation of one such gene, TLN2, identified genotype-dependent differences in the expression of functionally different versions of TLN2 that is hypothesized to shape differences in cellular adhesion structures. Finally, a new statistical approach is presented in which patient biomarkers are used to predict the number of species observed during infection. Overall, our results describe how patient genetic variation influence the types of bacteria likely to infect an individual as well as influence healing.

The microbiome of diabetic foot ulcers: a comparison of swab and tissue biopsy wound sampling techniques using 16S rRNA gene sequencing

Background

Health-care professionals need to collect wound samples to identify potential pathogens that contribute to wound infection. Obtaining appropriate samples from diabetic foot ulcers (DFUs) where there is a suspicion of infection is of high importance. Paired swabs and tissue biopsies were collected from DFUs and both sampling techniques were compared using 16S rRNA gene sequencing.

Results

Mean bacterial abundance determined using quantitative polymerase chain reaction (qPCR) was significantly lower in tissue biopsies (p = 0.03). The mean number of reads across all samples was significantly higher in wound swabs \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \Big(\overline{X} $$\end{document}(X¯ = 32,014) compared to tissue (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \overline{X} $$\end{document}X¯ = 15,256, p = 0.001). Tissue biopsies exhibited greater overall diversity of bacteria relative to swabs (Shannon’s H diversity p = 0.009). However, based on a presence/absence analysis of all paired samples, the frequency of occurrence of bacteria from genera of known and potential pathogens was generally higher in wound swabs than tissue biopsies. Multivariate analysis identified significantly different bacterial communities in swabs compared to tissue (p = 0.001). There was minimal correlation between paired wound swabs and tissue biopsies in the number and types of microorganisms. RELATE analysis revealed low concordance between paired DFU swab and tissue biopsy samples (Rho = 0.043, p = 0.34).

Conclusions

Using 16S rRNA gene sequencing this study identifies the potential for using less invasive swabs to recover high relative abundances of known and potential pathogen genera from DFUs when compared to the gold standard collection method of tissue biopsy.

The endolysin of the Acinetobacter baumannii phage vB_AbaP_D2 shows broad antibacterial activity

The emergence and rapid spread of multidrug‐resistant bacteria has induced intense research for novel therapeutic approaches. In this study, the Acinetobacter baumannii bacteriophage D2 (vB_AbaP_D2) was isolated, characterized and sequenced. The endolysin of bacteriophage D2, namely Abtn‐4, contains an amphipathic helix and was found to have activity against multidrug‐resistant Gram‐negative strains. By more than 3 log units, A. baumannii were killed by Abtn‐4 (5 µM) in 2 h. In absence of outer membrane permeabilizers, Abtn‐4 exhibited broad antimicrobial activity against several Gram‐positive and Gram‐negative bacteria, such as Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumonia, Enterococcus and Salmonella. Furthermore, Abtn‐4 had the ability to reduce biofilm formation. Interestingly, Abtn‐4 showed antimicrobial activity against phage‐resistant bacterial mutants. Based on these results, endolysin Abtn‐4 may be a promising candidate therapeutic agent for multidrug‐resistant bacterial infections.

Lipid-based nanosystems for targeting bone implant-associated infections: current approaches and future endeavors

Bone infections caused by Staphylococcus aureus are a major concern in medical care, particularly when associated with orthopedic-implant devices. The ability of the bacteria to form biofilms and their capacity to invade and persist within osteoblasts turn the infection eradication into a huge challenge. The reduction of antibiotic penetration through bacterial biofilms associated with the presence of persistent cells, ability to survive in the host, and high tolerance to antibiotics are some of the reasons for the difficult treatment of these infections. Effective therapeutic approaches are urgently needed. In this sense, lipid-based nanosystems, such as liposomes, have been investigated as an innovative and alternative strategy for the treatment of implant-associated S. aureus infections, due to their preferential accumulation at infected sites and interaction with S. aureus. This review highlights the recent advances on antibiotic-loaded liposome formulations both in vitro and in vivo and how the interaction with S. aureus biofilms may be improved by modulating the liposomal external surface. Graphical Abstract.

Quorum Sensing Communication: Molecularly Connecting Cells, Their Neighbors, and Even Devices

Quorum sensing (QS) is a molecular signaling modality that mediates molecular-based cell–cell communication. Prevalent in nature, QS networks provide bacteria with a method to gather information from the environment and make decisions based on the intel. With its ability to autonomously facilitate both inter- and intraspecies gene regulation, this process can be rewired to enable autonomously actuated, but molecularly programmed, genetic control. On the one hand, novel QS-based genetic circuits endow cells with smart functions that can be used in many fields of engineering, and on the other, repurposed QS circuitry promotes communication and aids in the development of synthetic microbial consortia. Furthermore, engineered QS systems can probe and intervene in interkingdom signaling between bacteria and their hosts. Lastly, QS is demonstrated to establish conversation with abiotic materials, especially by taking advantage of biological and even electronically induced assembly processes; such QS-incorporated biohybrid devices offer innovative ways to program cell behavior and biological function.

Antimicrobial resistance three ways: healthcare crisis, major concepts and the relevance of biofilms

Worldwide, infections are resuming their role as highly effective killing diseases, as current treatments are failing to respond to the growing problem of antimicrobial resistance (AMR). The social and economic burden of AMR seems ever rising, with health- and research-related organizations rushing to collaborate on a worldwide scale to find effective solutions. Resistant bacteria are spreading even in first-world nations, being found not only in healthcare-related settings, but also in food and in the environment. In this minireview, the impact of AMR in healthcare systems and the major bacteria behind it are highlighted. Ecological aspects of AMR evolution and the complexity of its molecular mechanisms are explained. Major concepts, such as intrinsic, acquired and adaptive resistance, as well as tolerance and heteroresistance, are also clarified. More importantly, the problematic of biofilms and their role in AMR, namely their main resistance and tolerance mechanisms, are elucidated. Finally, some of the most promising anti-biofilm strategies being investigated are reviewed. Much is still to be done regarding the study of AMR and the discovery of new anti-biofilm strategies. Gladly, considerable research on this topic is generated every day and increasingly concerted actions are being engaged globally to try and tackle this problem.

Preliminary assessment of nanopore-based metagenomic sequencing for the diagnosis of prosthetic joint infection

OBJECTIVES

Pathogen identification is crucial for the diagnosis and management of periprosthetic joint infection (PJI). Although culturing methods are the foundation of pathogen detection in PJI, false-negative results often occur. Oxford nanopore sequencing (ONS) is a promising alternative for detecting pathogens and providing information on their antimicrobial resistance (AMR) profiles, without culturing.

METHODS

To evaluate the capability of metagenomic ONS (mONS) in detecting pathogens from PJI samples, both metagenomic next-generation sequencing (mNGS) and mONS were performed in 15 osteoarticular samples from nine consecutive PJI patients according to the modified Musculoskeletal Infection Society (MSIS) criteria. The sequencing data generated from both platforms were then analyzed for pathogen identification and AMR detection using an in-house-developed bioinformatics pipeline.

RESULTS

Our results showed that mONS could be applied to detect the causative pathogen and characterize its AMR features in fresh PJI samples. By real-time sequencing and analysis, pathogen identification and AMR detection from the initiation of sequencing were accelerated.

CONCLUSION

We showed proof of concept that mONS can function as a rapid, accurate tool in PJI diagnostic microbiology. Despite efforts to reduce host DNA, the high proportion of host DNA was still a limitation of this method that prevented full genome analysis.

Natural brominated phenoxyphenols kill persistent and biofilm-incorporated cells of MRSA and other pathogenic bacteria

Due to a high unresponsiveness to chemotherapy, biofilm formation is an important medical problem that frequently occurs during infection with many bacterial pathogens. In this study, the marine sponge-derived natural compounds 4,6-dibromo-2-(2',4'-dibromophenoxy)phenol and 3,4,6-tribromo-2-(2',4'-dibromophenoxy)phenol were found to exhibit broad antibacterial activity against medically relevant gram-positive and gram-negative pathogens. The compounds were not only bactericidal against both replicating and stationary phase-persistent planktonic cells of methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa; they also killed biofilm-incorporated cells of both species while not affecting biofilm structural integrity. Moreover, these compounds were active against carbapenemase-producing Enterobacter sp. This simultaneous activity of compounds against different growth forms of both gram-positive and gram-negative bacteria is rare. Genome sequencing of spontaneous resistant mutants and proteome analysis suggest that resistance is mediated by downregulation of the bacterial EIIBC phosphotransferase components scrA and mtlA in MRSA likely leading to a lower uptake of the molecules. Due to their only moderate cytotoxicity against human cell lines, phenoxyphenols provide an interesting new scaffold for development of antimicrobial agents with activity against planktonic cells, persisters and biofilm-incoporated cells of ESKAPE pathogens. KEY POINTS: • Brominated phenoxyphenols kill actively replicating and biofilm-incorporated bacteria. • Phosphotransferase systems mediate uptake of brominated phenoxyphenols. • Downregulation of phosphotransferase systems mediate resistance.

Radial Extracorporeal Shock Wave Therapy Against Cutibacterium acnes Implant-Associated Infections: An in Vitro Trial

BACKGROUND

Antibiotic management of low-virulent implant-associated infections induced by Cutibacterium acnes may be compromised by multi-drug resistance development, side effects, and increased cost. Therefore, we sought to assess the effects of shock wave therapy against the above pathogen using an in vitro model of infection.

METHODS

We used a total of 120 roughened titanium alloy disks, simulating orthopedic biomaterials, to assess the results of radial extracorporeal shock wave therapy (rESWT) against C. acnes (ATCC 11827) biofilms relative to untreated control. In particular, we considered 1.6 to 2.5 Bar with a frequency ranging from 8-11 Hz and 95 to 143 impulses per disk to investigate the antibacterial effect of rESWT against C. acnes planktonic (free-floating) and biofilm forms.

RESULTS

Planktonic bacteria load diminished by 54% compared to untreated control after a 1.8-bar setting with a frequency of 8 Hz and 95 impulses was applied (median absorbance (MA) for intervention vs. control groups was 0.9245 (IQR= 0.888 to 0.104) vs. 0.7705 (IQR = 0.712 to 0.864), respectively, p = 0.001). Likewise, a statistically significant reduction in the amount of biofilm relative to untreated control was documented when the above setting was considered (MA for treatment vs biofilm control groups was 0.244 (IQR= 0.215-0.282) and 0.298 (IQR = 0.247-0.307), respectively, p = 0.033).

CONCLUSION

A 50% biofilm eradication was documented following application of low-pressure and low-frequency radial shock waves, so rESWT could be investigated as an adjuvant treatment to antibiotics, but it cannot be recommended as a standalone treatment against device-associated infections induced by C. ances.

Time to Say Goodbye to Bronchiolitis, Viral Wheeze, Reactive Airways Disease, Wheeze Bronchitis and All That

The diagnosis and management of infants and children with a significant viral lower respiratory tract illness remains the subject of much debate and little progress. Over the decades various terms for such illnesses have been in and fallen out of fashion or have evolved to mean different things to different clinicians. Terms such as "bronchiolitis," "reactive airways disease," "viral wheeze," and many more are used to describe the same condition and the same term is frequently used to describe illnesses caused by completely different dominant pathologies. This lack of clarity is due, in large part, to a failure to understand the basic underlying inflammatory and associated processes and, in part, due to the lack of a simple test to identify a condition such as asthma. Moreover, there is a lack of insight into the fact that the same pathology can produce different clinical signs at different ages. The consequence is that terminology and fashions in treatment have tended to go around in circles. As was noted almost 60 years ago, amongst pre-school children with a viral LRTI and airways obstruction there are those with a "viral bronchitis" and those with asthma. In the former group, a neutrophil dominated inflammation response is responsible for the airways' obstruction whilst amongst asthmatics much of the obstruction is attributable to bronchoconstriction. The airways obstruction in the former group is predominantly caused by airways secretions and to some extent mucosal oedema (a "snotty lung"). These patients benefit from good supportive care including supplemental oxygen if required (though those with a pre-existing bacterial bronchitis will also benefit from antibiotics). For those with a viral exacerbation of asthma, characterized by bronchoconstriction combined with impaired b-agonist responsiveness, standard management of an exacerbation of asthma (including the use of steroids to re-establish bronchodilator responsiveness) represents optimal treatment. The difficulty is identifying which group a particular patient falls into. A proposed simplified approach to the nomenclature used to categorize virus associated LRTIs is presented based on an understanding of the underlying pathological processes and how these contribute to the physical signs.

Chronic wound biofilms: diagnosis and therapeutic strategies

OBJECTIVE

To review the diagnosis of chronic wound biofilms and discuss current treatment approaches.

DATA SOURCES

Articles included in this review were obtained from the following databases: Wanfang, China National Knowledge Infrastructure, PubMed, and the Web of Science. We focused on research published before August 2019 with keywords including chronic wound, biofilm, bacterial biofilms, and chronic wound infection.

STUDY SELECTION

Relevant articles were selected by carefully reading the titles and abstracts. Further, different diagnosis and clinical treatment methods for chronic wound biofilm were compared and summarized from the selected published articles.

RESULTS

Recent guidelines on medical biofilms stated that approaches such as the use of scanning electron microscopy and confocal laser scanning microscopy are the most reliable types of diagnostic techniques. Further, therapeutic strategies include debridement, negative pressure wound therapy, ultrasound, antibiotic, silver-containing dressing, hyperbaric oxygen therapy, and others.

CONCLUSION

This review provides the identification and management of biofilms, and it can be used as a tool by clinicians for a better understanding of biofilms and translating research to develop best clinical practices.

Development of a high throughput and low cost model for the study of semi-dry biofilms

The persistence of microorganisms as biofilms on dry surfaces resistant to the usual terminal cleaning methods may pose an additional risk of transmission of infections. In this study, the Centre for Disease Control (CDC) dry biofilm model (DBM) was adapted into a microtiter plate format (Model 1) and replicated to create a novel in vitro model that replicates conditions commonly encountered in the healthcare environment (Model 2). Biofilms of Staphylococcus aureus grown in the two models were comparable to the biofilms of the CDC DBM in terms of recovered log₁₀ CFU well^-1. Assessment of the antimicrobial tolerance of biofilms grown in the two models showed Model 2 a better model for biofilm formation. Confirmation of the biofilms' phenotype with an extracellular matrix deficient S. aureus suggested stress tolerance through a non-matrix defined mechanism in microorganisms. This study highlights the importance of conditions maintained in bacterial growth as they affect biofilm phenotype and behaviour.

Can metagenomic next-generation sequencing identify the pathogens responsible for culture-negative prosthetic joint infection?

BACKGROUND

The aims of this study were to (1) evaluate the efficacy and safety of targeted antibiotics for the treatment of culture-negative prosthetic joint infection based on metagenomic next-generation sequencing results and (2) verify the accuracy and reliability of metagenomic next-generation sequencing for identifying pathogens related to culture-negative prosthetic joint infection.

METHODS

Ninety-seven consecutive PJI patients, including 27 patients with culture-negative prosthetic joint infection, were treated surgically at our center. Thirteen of the 27 culture-negative prosthetic joint infection patients, who were admitted before June 2017 and treated with empirical antibiotics, comprised the empirical antibiotic group (EA group), and the other 14 patients, who were admitted after June 2017 and treated with targeted antibiotics according to their metagenomic next-generation sequencing results, were classified as the targeted antibiotic group (TA group). The short-term infection control rate, incidence of antibiotic-related complications and costs were compared between the two groups.

RESULTS

Two of the patients in the EA group experienced debridement and prolonged antimicrobial therapy due to wound infection after the initial revision surgery. No recurrent infections were observed in the TA group; however, no significant difference in the infection control rate was found between the two groups (83.33% vs 100%, P = 0.217). More cases of antibiotic-related complications were recorded in the EA group (6 cases) than in the TA group (1 case), but the difference was not statistically significant (P = 0.0697). The cost of antibiotics obtained for the EA group was 20,168.37 Yuan (3236.38-45,297.16), which was higher than that found for the TA group (10,164.16 Yuan, 2959.54-16,661.04, P = 0.04).

CONCLUSIONS

Targeted antibiotic treatment for culture-negative prosthetic joint infection based on metagenomic next-generation sequencing results is associated with a favorable outcome, and metagenomic next-generation sequencing is a reliable tool for identifying pathogens related to culture-negative prosthetic joint infection.

Six-week antibiotic therapy after one-stage replacement arthroplasty for hip and knee periprosthetic joint infection

OBJECTIVES

One-stage replacement arthroplasty for treatment of periprosthetic joint infection (PJI) results in similar cure rate than two-stage (around 85-92%), but antibiotic therapy duration is not well established. The aim of this study was to evaluate the efficacy of a short six-week antibiotic course in periprosthetic joint infections after onstage exchange.

PATIENTS AND METHODS

Retrospective, observational study conducted at Orthopaedic Department of Cochin Hospital, Paris, between 1st January 2010 and 31 December 2015. Patients with a microbiologically proven PJI, treated with one-stage replacement and 6 weeks (+/1week) of antimicrobial therapy were included. Pearson's-χ² and Wilcoxon tests were used to compare categorical and continuous variables.

RESULTS

Fifty patients with periprosthetic joint infections (42 hip, 8 knee PJI) treated with one-stage replacement arthroplasty were included. Median age was 69.3 years (IQR 24.5-97.4). Infections occurred after a mean of 36 months (IQR 1-216). Bone biopsy cultures were positive for Staphylococcus spp. in 29 patients (58%), Cutibacterium acnes in 19 (38%), Gram-negative bacilli in 6 (12%). Polymicrobial infections occurred in 12 (24%). Intravenous antibiotics were administered for a median of 11 days (IQR 4-45) and 46 patients (92%) were switched to an oral therapy. Medium follow-up was of 32 months (IQR 12-101). Overall remission rate was 90%.

CONCLUSIONS

A six-week course of antibiotics in knee and hip PJIs treated with one-stage RA has a satisfactory remission rate in this open study.