Adjunct phage treatment enhances the effectiveness of low antibiotic concentration against Staphylococcus aureus biofilms in vitro

Bacteriophages for ESKAPE: role in pathogenicity and measures of control

INTRODUCTION

The quest to combat bacterial infections has dreaded humankind for centuries. Infections involving ESKAPE (Enterococcus spp., Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.) impose therapeutic challenges due to the emergence of antimicrobial drug resistance. Recently, investigations with bacteriophages have led to the development of novel strategies against ESKAPE infections. Also, bacteriophages have been demonstrated to be instrumental in the dissemination of virulence markers in ESKAPE pathogens.

AREAS COVERED

The review highlights the potential of bacteriophage in and against the pathogenicity of antibiotic-resistant ESKAPE pathogens. The review also emphasizes the challenges of employing bacteriophage in treating ESKAPE pathogens and the knowledge gap in the bacteriophage mediated antibiotic resistance and pathogenicity in ESKAPE infections.

EXPERT OPINION

Bacteriophage infection can kill the host bacteria but in survivors can transfer genes that contribute toward the survival of the pathogens in the host and resistance toward multiple antimicrobials. The knowledge on the dual role of bacteriophages in the treatment and pathogenicity will assist in the prediction and development of novel therapeutics targeting antimicrobial-resistant ESKAPE. Therefore, extensive investigations on the efficacy of synthetic bacteriophage, bacteriophage cocktails, and bacteriophage in combination with antibiotics are needed to develop effective therapeutics against ESKAPE infections.

Bacteriophage AB-SA01 Cocktail in Combination with Antibiotics against MRSA-VISA Strain in an In Vitro Pharmacokinetic/Pharmacodynamic Model

This study aimed to test the efficacy of bacteriophage-antibiotic combinations (BACs) in vitro in 24-h time-kill settings and in ex vivo simulated endocardial vegetation (SEV) pharmacokinetic/pharmacodynamic models for 96 h. BACs prevented the development of bacteriophage resistance, while some bacteriophage resistance emerged in bacteriophage-alone treatments. In addition, BACs resulted in an enhancement of bacterial eradication in SEV models. Our findings support the potential activity of BAC therapy for combating serious methicillin-resistant Staphylococcus aureus (MRSA) infections.

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.

Bacteriophage Enumeration and Detection Methods

Application of phages as alternative antimicrobials to combat pathogenic bacteria and their association to a healthy gut microbiome has prompted a need for precise methods for detection and enumeration of phage particles. There are many applicable methods, but care should be taken considering the measured object (infectious phage, whole phage particle or nucleic acid and proteins) and the concept behind the technique to avoid misinterpretations. While molecular methods cannot discriminate between viable and non-infectious phages, the traditional techniques for counting infectious phages can be time consuming and poorly reproducible. Here, we describe the methods currently used for phage detection and enumeration and highlight their advantages as well as their limitations. Finally, we provide insight on how to deal with complex samples, as well as future prospects in the field of phage quantification.

Proximate and ultimate causes of the bactericidal action of antibiotics

During the past 85 years of antibiotic use, we have learned a great deal about how these ‘miracle’ drugs work. We know the molecular structures and interactions of these drugs and their targets and the effects on the structure, physiology and replication of bacteria. Collectively, we know a great deal about these proximate mechanisms of action for virtually all antibiotics in current use. What we do not know is the ultimate mechanism of action; that is, how these drugs irreversibly terminate the ‘individuality’ of bacterial cells by removing barriers to the external world (cell envelopes) or by destroying their genetic identity (DNA). Antibiotics have many different ‘mechanisms of action’ that converge to irreversible lethal effects. In this Perspective, we consider what our knowledge of the proximate mechanisms of action of antibiotics and the pharmacodynamics of their interaction with bacteria tell us about the ultimate mechanisms by which these antibiotics kill bacteria.

We know a lot about antibiotics and their targets; however, how antibiotics actually kill bacteria is not entirely clear and is up for debate. In this Perspective, Baquero and Levin reflect on this ultimate action of antibiotics and consider different mechanisms and modulating factors.

Therapeutics and delivery vehicles for local treatment of osteomyelitis

Osteomyelitis, or the infection of the bone, presents a major complication in orthopedics and may lead to prolonged hospital visits, implant failure, and in more extreme cases, amputation of affected limbs. Typical treatment for this disease involves surgical debridement followed by long-term, systemic antibiotic administration, which contributes to the development of antibiotic-resistant bacteria and has limited ability to eradicate challenging biofilm-forming pathogens including Staphylococcus aureus-the most common cause of osteomyelitis. Local delivery of high doses of antibiotics via traditional bone cement can reduce systemic side effects of an antibiotic. Nonetheless, growing concerns over burst release (then subtherapeutic dose) of antibiotics, along with microbial colonization of the nondegradable cement biomaterial, further exacerbate antibiotic resistance and highlight the need to engineer alternative antimicrobial therapeutics and local delivery vehicles with increased efficacy against, in particular, biofilm-forming, antibiotic-resistant bacteria. Furthermore, limited guidance exists regarding both standardized formulation protocols and validated assays to predict efficacy of a therapeutic against multiple strains of bacteria. Ideally, antimicrobial strategies would be highly specific while exhibiting a broad spectrum of bactericidal activity. With a focus on S. aureus infection, this review addresses the efficacy of novel therapeutics and local delivery vehicles, as alternatives to the traditional antibiotic regimens. The aim of this review is to discuss these components with regards to long bone osteomyelitis and to encourage positive directions for future research efforts.

Local Bacteriophage Delivery for Treatment and Prevention of Bacterial Infections

As viruses with high specificity for their bacterial hosts, bacteriophages (phages) are an attractive means to eradicate bacteria, and their potential has been recognized by a broad range of industries. Against a background of increasing rates of antibiotic resistance in pathogenic bacteria, bacteriophages have received much attention as a possible "last-resort" strategy to treat infections. The use of bacteriophages in human patients is limited by their sensitivity to acidic pH, enzymatic attack and short serum half-life. Loading phage within a biomaterial can shield the incorporated phage against many of these harmful environmental factors, and in addition, provide controlled release for prolonged therapeutic activity. In this review, we assess the different classes of biomaterials (i.e., biopolymers, synthetic polymers, and ceramics) that have been used for phage delivery and describe the processing methodologies that are compatible with phage embedding or encapsulation. We also elaborate on the clinical or pre-clinical data generated using these materials. While a primary focus is placed on the application of phage-loaded materials for treatment of infection, we also include studies from other translatable fields such as food preservation and animal husbandry. Finally, we summarize trends in the literature and identify current barriers that currently prevent clinical application of phage-loaded biomaterials.

Antibiotic Tolerance of Staphylococcus aureus Biofilm in Periprosthetic Joint Infections and Antibiofilm Strategies

The need for bone and joint prostheses is currently growing due to population aging, leading to an increase in prosthetic joint infection cases. Biofilms represent an adaptive and quite common bacterial response to several stress factors which confer an important protection to bacteria. Biofilm formation starts with bacterial adhesion on a surface, such as an orthopedic prosthesis, further reinforced by matrix synthesis. The biofilm formation and structure depend on the immediate environment of the bacteria. In the case of infection, the periprosthetic joint environment represents a particular interface between bacteria, host cells, and the implant, favoring biofilm initiation and maturation. Treating such an infection represents a huge challenge because of the biofilm-specific high tolerance to antibiotics and its ability to evade the immune system. It is crucial to understand these mechanisms in order to find new and adapted strategies to prevent and eradicate implant-associated infections. Therefore, adapted models mimicking the infectious site are of utmost importance to recreate a relevant environment in order to test potential antibiofilm molecules. In periprosthetic joint infections, Staphylococcus aureus is mainly involved because of its high adaptation to the human physiology. The current review deals with the mechanisms involved in the antibiotic resistance and tolerance of Staphylococcus aureus in the particular periprosthetic joint infection context, and exposes different strategies to manage these infections.

Staphylococcal Biofilm Development: Structure, Regulation, and Treatment Strategies

In many natural and clinical settings, bacteria are associated with some type of biotic or abiotic surface that enables them to form biofilms, a multicellular lifestyle with bacteria embedded in an extracellular matrix. Staphylococcus aureus and Staphylococcus epidermidis, the most frequent causes of biofilm-associated infections on indwelling medical devices, can switch between an existence as single free-floating cells and multicellular biofilms. During biofilm formation, cells first attach to a surface and then multiply to form microcolonies. They subsequently produce the extracellular matrix, a hallmark of biofilm formation, which consists of polysaccharides, proteins, and extracellular DNA. After biofilm maturation into three-dimensional structures, the biofilm community undergoes a disassembly process that leads to the dissemination of staphylococcal cells. As biofilms are dynamic and complex biological systems, staphylococci have evolved a vast network of regulatory mechanisms to modify and fine-tune biofilm development upon changes in environmental conditions. Thus, biofilm formation is used as a strategy for survival and persistence in the human host and can serve as a reservoir for spreading to new infection sites. Moreover, staphylococcal biofilms provide enhanced resilience toward antibiotics and the immune response and impose remarkable therapeutic challenges in clinics worldwide. This review provides an overview and an updated perspective on staphylococcal biofilms, describing the characteristic features of biofilm formation, the structural and functional properties of the biofilm matrix, and the most important mechanisms involved in the regulation of staphylococcal biofilm formation. Finally, we highlight promising strategies and technologies, including multitargeted or combinational therapies, to eradicate staphylococcal biofilms.

Staphylococcal Biofilm Development: Structure, Regulation, and Treatment Strategies

In many natural and clinical settings, bacteria are associated with some type of biotic or abiotic surface that enables them to form biofilms, a multicellular lifestyle with bacteria embedded in an extracellular matrix. Staphylococcus aureus and Staphylococcus epidermidis, the most frequent causes of biofilm-associated infections on indwelling medical devices, can switch between an existence as single free-floating cells and multicellular biofilms. During biofilm formation, cells first attach to a surface and then multiply to form microcolonies. They subsequently produce the extracellular matrix, a hallmark of biofilm formation, which consists of polysaccharides, proteins, and extracellular DNA. After biofilm maturation into three-dimensional structures, the biofilm community undergoes a disassembly process that leads to the dissemination of staphylococcal cells. As biofilms are dynamic and complex biological systems, staphylococci have evolved a vast network of regulatory mechanisms to modify and fine-tune biofilm development upon changes in environmental conditions. Thus, biofilm formation is used as a strategy for survival and persistence in the human host and can serve as a reservoir for spreading to new infection sites. Moreover, staphylococcal biofilms provide enhanced resilience toward antibiotics and the immune response and impose remarkable therapeutic challenges in clinics worldwide. This review provides an overview and an updated perspective on staphylococcal biofilms, describing the characteristic features of biofilm formation, the structural and functional properties of the biofilm matrix, and the most important mechanisms involved in the regulation of staphylococcal biofilm formation. Finally, we highlight promising strategies and technologies, including multitargeted or combinational therapies, to eradicate staphylococcal biofilms.

Phage-Antibiotic Synergy Is Driven by a Unique Combination of Antibacterial Mechanism of Action and Stoichiometry

The continued rise in antibiotic resistance is precipitating a medical crisis. Bacteriophage (phage) has been hailed as one possible therapeutic option to augment the efficacy of antibiotics. However, only a few studies have addressed the synergistic relationship between phage and antibiotics. Here, we report a comprehensive analysis of phage-antibiotic interaction that evaluates synergism, additivism, and antagonism for all classes of antibiotics across clinically achievable stoichiometries. We combined an optically based real-time microtiter plate readout with a matrix-like heat map of treatment potencies to measure phage and antibiotic synergy (PAS), a process we term synography. Phage-antibiotic synography was performed against a pandemic drug-resistant clonal group of extraintestinal pathogenic Escherichia coli (ExPEC) with antibiotic levels blanketing the MIC across seven orders of viral titers. Our results suggest that, under certain conditions, phages provide an adjuvating effect by lowering the MIC for drug-resistant strains. Furthermore, synergistic and antagonistic interactions are highly dependent on the mechanism of bacterial inhibition by the class of antibiotic paired to the phage, and when synergism is observed, it suppresses the emergence of resistant cells. Host conditions that simulate the infection environment, including serum and urine, suppress PAS in a bacterial growth-dependent manner. Lastly, two different related phages that differed in their burst sizes produced drastically different synograms. Collectively, these data suggest lytic phages can resuscitate an ineffective antibiotic for previously resistant bacteria while also synergizing with antibiotics in a class-dependent manner, processes that may be dampened by lower bacterial growth rates found in host environments.IMPORTANCE Bacteriophage (phage) therapy is a promising approach to combat the rise of multidrug-resistant bacteria. Currently, the preferred clinical modality is to pair phage with an antibiotic, a practice thought to improve efficacy. However, antagonism between phage and antibiotics has been reported, the choice of phage and antibiotic is not often empirically determined, and the effect of the host factors on the effectiveness is unknown. Here, we interrogate phage-antibiotic interactions across antibiotics with different mechanisms of action. Our results suggest that phage can lower the working MIC for bacterial strains already resistant to the antibiotic, is dependent on the antibiotic class and stoichiometry of the pairing, and is dramatically influenced by the host microenvironment.

Bacteriophage-Antibiotic Combination Strategy: an Alternative against Methicillin-Resistant Phenotypes of Staphylococcus aureus

Comparative time-kill experiments with Staphylococcus aureus bacteriophage (phage) Sb-1 alone and phage-antibiotic combinations (PACs) against two methicillin-resistant S. aureus (MRSA) strains have shown synergy with both daptomycin-phage and vancomycin-phage combinations. PACs prevented development of phage resistance and demonstrated bactericidal activity for all triple combinations. In addition, the extracellular membrane vesicle (MV) formation and the potential impact of phage on MV suppression were examined. Our results demonstrate the potential of PAC for combating MRSA infections.

Fitness Trade-Offs Resulting from Bacteriophage Resistance Potentiate Synergistic Antibacterial Strategies

Bacteria that cause life-threatening infections in humans are becoming increasingly difficult to treat. In some instances, this is due to intrinsic and acquired antibiotic resistance, indicating that new therapeutic approaches are needed to combat bacterial pathogens. There is renewed interest in utilizing viruses of bacteria known as bacteriophages (phages) as potential antibacterial therapeutics. However, critics suggest that similar to antibiotics, the development of phage-resistant bacteria will halt clinical phage therapy. Although the emergence of phage-resistant bacteria is likely inevitable, there is a growing body of literature showing that phage selective pressure promotes mutations in bacteria that allow them to subvert phage infection, but with a cost to their fitness. Such fitness trade-offs include reduced virulence, resensitization to antibiotics, and colonization defects. Resistance to phage nucleic acid entry, primarily via cell surface modifications, compromises bacterial fitness during antibiotic and host immune system pressure. In this minireview, we explore the mechanisms behind phage resistance in bacterial pathogens and the physiological consequences of acquiring phage resistance phenotypes. With this knowledge, it may be possible to use phages to alter bacterial populations, making them more tractable to current therapeutic strategies.

Antibacterial efficacy of R-type pyocins against Pseudomonas aeruginosa on biofilms and in a murine model of acute lung infection

BACKGROUND

The appearance of MDR strains and the development of biofilms make Pseudomonas aeruginosa infections a therapeutic challenge. To overcome this scenario, bacteriocins have been proposed as a potential adjuvant or alternative to antibiotic treatment.

OBJECTIVES

To study the activity of R-pyocins on biofilms and in a murine model of pneumonia using a high-risk clone of P. aeruginosa.

METHODS

The activity of R-pyocins on P. aeruginosa biofilms was tested on bacteria attached to a silicone surface, before and after biofilm formation. The effectiveness of R1-pyocin was studied in a murine model of pneumonia using ST175, a high-risk clone of P. aeruginosa.

RESULTS

R-pyocins attacked adherent bacteria, preventing biofilm formation, and penetrated into the biofilm, killing P. aeruginosa within it, resulting in a dramatic reduction in bacterial load. R1-pyocin was active in a murine model of P. aeruginosa lung infection, administered before infection as a preventive treatment, and in acute pneumonia, with efficiency higher than standard colistin treatment. In addition, this work is the first to describe histopathological lung changes after administration of R-pyocins, contributing to the resolution of P. aeruginosa pneumonia in a murine model.

CONCLUSIONS

This work highlights the potential use of the R-pyocins as therapeutic agents, alone or as adjuvants, due to its effectiveness on biofilms and in a murine model of pneumonia using ST175, a high-risk clone of P. aeruginosa. It may thus be feasible to consider R-pyocins as a possible therapeutic alternative in XDR infections, where treatment alternatives are limited.

Quantitative Models of Phage-Antibiotic Combination Therapy

This work develops and analyzes a novel model of phage-antibiotic combination therapy, specifically adapted to an in vivo context. The objective is to explore the underlying basis for clinical application of combination therapy utilizing bacteriophage that target antibiotic efflux pumps in Pseudomonas aeruginosa. In doing so, the paper addresses three key questions. How robust is combination therapy to variation in the resistance profiles of pathogens? What is the role of immune responses in shaping therapeutic outcomes? What levels of phage and antibiotics are necessary for curative success? As we show, combination therapy outperforms either phage or antibiotic alone, and therapeutic effectiveness is enhanced given interaction with innate immune responses. Notably, therapeutic success can be achieved even at subinhibitory concentrations of antibiotic. These in silico findings provide further support to the nascent application of combination therapy to treat MDR bacterial infections, while highlighting the role of system-level feedbacks in shaping therapeutic outcomes.

The spread of multidrug-resistant (MDR) bacteria is a global public health crisis. Bacteriophage therapy (or “phage therapy”) constitutes a potential alternative approach to treat MDR infections. However, the effective use of phage therapy may be limited when phage-resistant bacterial mutants evolve and proliferate during treatment. Here, we develop a nonlinear population dynamics model of combination therapy that accounts for the system-level interactions between bacteria, phage, and antibiotics for in vivo application given an immune response against bacteria. We simulate the combination therapy model for two strains of Pseudomonas aeruginosa, one which is phage sensitive (and antibiotic resistant) and one which is antibiotic sensitive (and phage resistant). We find that combination therapy outperforms either phage or antibiotic alone and that therapeutic effectiveness is enhanced given interaction with innate immune responses. Notably, therapeutic success can be achieved even at subinhibitory concentrations of antibiotics, e.g., ciprofloxacin. These in silico findings provide further support to the nascent application of combination therapy to treat MDR bacterial infections, while highlighting the role of innate immunity in shaping therapeutic outcomes.

IMPORTANCE This work develops and analyzes a novel model of phage-antibiotic combination therapy, specifically adapted to an in vivo context. The objective is to explore the underlying basis for clinical application of combination therapy utilizing bacteriophage that target antibiotic efflux pumps in Pseudomonas aeruginosa. In doing so, the paper addresses three key questions. How robust is combination therapy to variation in the resistance profiles of pathogens? What is the role of immune responses in shaping therapeutic outcomes? What levels of phage and antibiotics are necessary for curative success? As we show, combination therapy outperforms either phage or antibiotic alone, and therapeutic effectiveness is enhanced given interaction with innate immune responses. Notably, therapeutic success can be achieved even at subinhibitory concentrations of antibiotic. These in silico findings provide further support to the nascent application of combination therapy to treat MDR bacterial infections, while highlighting the role of system-level feedbacks in shaping therapeutic outcomes.

Bacteriophage Therapeutics: A Primer for Clinicians on Phage-Antibiotic Combinations

Multidrug-resistant organisms have caused a marked depletion of effective antimicrobials, and the narrow pipeline of antibiotics has demanded the need to find novel therapeutic alternatives including nonantibiotic agents. Bacteriophages (phages) are viruses that use the bacterial machinery to infect, replicate, and kill bacterial cells. Although a marked decline in their use was driven by the discovery of antibiotics, the era of antibiotic resistance has led to a resurgence of phage therapy into clinical practice. The term phage-antibiotic synergy (PAS) was coined just over a decade ago and described that sublethal concentrations of antibiotics could stimulate phage production by bacterial cells. Recent literature has described PAS and other encouraging interactions with various phage and antibiotic combinations against a variety of bacterial strains. The primary objective of this review is to discuss the positive interactions between phage and antibiotic combinations, with an emphasis on PAS, reductions in bacterial growth or minimum inhibitory concentrations, enhanced biofilm eradication, and alterations in the emergence of bacterial resistance. A peer-reviewed literature search was conducted (1890-2019) using the PubMed, Medline, and Google Scholar databases. Although more investigation is certainly needed, the combination of bacteriophages with antibiotics is a promising strategy to target organisms with limited or no therapeutic options. This approach may also foster the ability to lower the antibiotic dose and may reduce the potential for antibiotic resistance emergence during therapy.

Bacteriophages as Adjuvant to Antibiotics for the Treatment of Periprosthetic Joint Infection Caused by Multidrug-Resistant Pseudomonas aeruginosa

We documented the adjunctive bacteriophage therapy to treat a chronic relapsing periprosthetic joint infection of the knee and chronic osteomyelitis of the femur caused by multidrug-resistant Pseudomonas aeruginosa The combined antibiotic-phage treatment eradicated the infection, and no side effects to phages were observed.

Pharmacologically Aware Phage Therapy: Pharmacodynamic and Pharmacokinetic Obstacles to Phage Antibacterial Action in Animal and Human Bodies

The use of viruses infecting bacteria (bacteriophages or phages) to treat bacterial infections has been ongoing clinically for approximately 100 years. Despite that long history, the growing international crisis of resistance to standard antibiotics, abundant anecdotal evidence of efficacy, and one successful modern clinical trial of efficacy, this phage therapy is not yet a mainstream approach in medicine. One explanation for why phage therapy has not been subject to more widespread implementation is that phage therapy research, both preclinical and clinical, can be insufficiently pharmacologically aware. Consequently, here we consider the pharmacological obstacles to phage therapy effectiveness, with phages in phage therapy explicitly being considered to serve as drug equivalents. The study of pharmacology has traditionally been differentiated into pharmacokinetic and pharmacodynamic aspects. We therefore separately consider the difficulties that phages as virions can have in traveling through body compartments toward reaching their target bacteria (pharmacokinetics) and the difficulties that phages can have in exerting antibacterial activity once they have reached those bacteria (pharmacodynamics). The latter difficulties, at least in part, are functions of phage host range and bacterial resistance to phages. Given the apparently low toxicity of phages and the minimal side effects of phage therapy as practiced, phage therapy should be successful so long as phages can reach the targeted bacteria in sufficiently high numbers, adsorb, and then kill those bacteria. Greater awareness of what obstacles to this success generally or specifically can exist, as documented in this review, should aid in the further development of phage therapy toward wider use.

Phage-Antibiotic Combination Treatments: Antagonistic Impacts of Antibiotics on the Pharmacodynamics of Phage Therapy?

Bacteria can evolve resistance to antibiotics. Even without changing genetically, bacteria also can display tolerance to antibiotic treatments. Many antibiotics are also broadly acting, as can result in excessive modifications of body microbiomes. Particularly for antibiotics of last resort or in treating extremely ill patients, antibiotics furthermore can display excessive toxicities. Antibiotics nevertheless remain the standard of care for bacterial infections, and rightly so given their long track records of both antibacterial efficacy and infrequency of severe side effects. Antibiotics do not successfully cure all treated bacterial infections, however, thereby providing a utility to alternative antibacterial approaches. One such approach is the use of bacteriophages, the viruses of bacteria. This nearly 100-year-old bactericidal, anti-infection technology can be effective against antibiotic-resistant or -tolerant bacteria, including bacterial biofilms and persister cells. Ideally phages could be used in combination with standard antibiotics while retaining their anti-bacterial pharmacodynamic activity, this despite antibiotics interfering with aspects of bacterial metabolism that are also required for full phage infection activity. Here I examine the literature of pre-clinical phage-antibiotic combination treatments, with emphasis on antibiotic-susceptible bacterial targets. I review evidence of antibiotic interference with phage infection activity along with its converse: phage antibacterial functioning despite antibiotic presence.

Diagnosis and treatment of biofilm infections in children

PURPOSE OF REVIEW

Biofilm-associated infections cause difficulties in the management of childhood chronic infections and other diseases, due to the invasive nature of interventions which are often necessary for definitive management. Despite their importance, there are challenges in diagnosing biofilm infections and gaps in clinicians' understanding regarding the significance of biofilms.

RECENT FINDINGS

Many chronic infections associated with biofilms remain difficult or impossible to eradicate with conventional therapy. Surgical intervention, implant removal or long-term intermittent or suppressive antimicrobial therapy may be required. There are still significant challenges in detecting biofilms which presents a barrier in clinical practice and research. Novel therapies to disrupt biofilms are currently under investigation, which may help reduce the impact of antimicrobial resistance.

SUMMARY

Biofilm-associated infection should be considered wherever there is clinical concern for an infection affecting prosthetic material, where there is a predisposing condition such as suppurative lung disease; or in the setting of chronic or relapsing infections which may be culture negative. New diagnostic methods for detecting biofilms are a research priority for both clinical diagnosis and the ability to conduct high quality clinical trials of novel antibiofilm interventions.