A combination of roxithromycin and imipenem as an antimicrobial strategy against biofilms formed by Staphylococcus aureus

New Perspectives on Old and New Therapies of Staphylococcal Skin Infections: The Role of Biofilm Targeting in Wound Healing

Among the most common complications of both chronic wound and surgical sites are staphylococcal skin infections, which slow down the wound healing process due to various virulence factors, including the ability to produce biofilms. Furthermore, staphylococcal skin infections are often caused by methicillin-resistant Staphylococcus aureus (MRSA) and become a therapeutic challenge. The aim of this narrative review is to collect the latest evidence on old and new anti-staphylococcal therapies, assessing their anti-biofilm properties and their effect on skin wound healing. We considered antibiotics, quorum sensing inhibitors, antimicrobial peptides, topical dressings, and antimicrobial photo-dynamic therapy. According to our review of the literature, targeting of biofilm is an important therapeutic choice in acute and chronic infected skin wounds both to overcome antibiotic resistance and to achieve better wound healing.

Use of fluorescence foldscope as an effective tool for detection of biofilm formation in Pseudomonas aeruginosa

Purpose

Pseudomonas aeruginosa is an opportunistic pathogen with biofilm-forming ability, by the virtue of which they can evade the immune response and antimicrobial chemotherapy. Several methods have been designed for the detection of biofilms but require sophisticated instrumentation and expertise. The present study, therefore, used an improvised device, 'fluorescence foldscope' which is an origami-based fluorescence microscope as an easy and effective tool to detect biofilm formation.

Methodology

Three representatives of P. aeruginosa of clinical origin were taken for the study along with two reference strains PA01 and ATCC27853. The strains were cultured in Luria Bertani (LB) broth with and without carbapenem (imipenem and meropenem) and cephalosporin (ceftazidime, cefotaxime and ceftriaxone) pressure, respectively. The cultures were diluted to 1:100 in LB; seeded with sterile glass slides at 90° angle and incubated for 5 consecutive days. The slides were observed with fluorescence foldscope.

Results

Fluorescence emission was observed in two test isolates CD1 and CD2 at 48 and 72 h, respectively, whereas no fluorescence was observed in CD3. The fluorescence observed in the isolates was not affected by 2 μg/ml carbapenem pressure, while with 2 μg/ml ceftazidime stress, a change in fluorescence was observed in CD2 in comparison to the fluorescence observed under normal growth condition.

Conclusion

Fluorescence foldscopy is an effective and reliable tool for the detection of biofilm formation in clinical isolates of P. aeruginosa under different laboratory conditions. Biofilm-forming P. aeruginosa worsens the medical condition and is difficult to eradicate. The present study came up with an effective and reliable tool for the detection of biofilm formation in clinical isolates of P. aeruginosa.

Importance of Biofilms in Urinary Tract Infections: New Therapeutic Approaches

Bacterial biofilms play an important role in urinary tract infections (UTIs), being responsible for persistence infections causing relapses and acute prostatitis. Bacterial forming biofilm are difficult to eradicate due to the antimicrobial resistant phenotype that this structure confers being combined therapy recommended for the treatment of biofilm-associated infections. However, the presence of persistent cells showing reduced metabolism that leads to higher levels of antimicrobial resistance makes the search for new therapeutic tools necessary. Here, a review of these new therapeutic approaches is provided including catheters coated with hydrogels or antibiotics, nanoparticles, iontophoresis, biofilm enzyme inhibitors, liposomes, bacterial interference, bacteriophages, quorum sensing inhibitors, low-energy surface acoustic waves, and antiadhesion agents. In conclusion, new antimicrobial drugs that inhibit bacterial virulence and biofilm formation are needed.

Bacterial biofilms: a diagnostic and therapeutic challenge

Bacteria have traditionally been regarded as individual organisms growing in homogeneous planktonic populations. However, bacteria in natural environments usually form communities of surface-adherent organisms embedded in an extracellular matrix, called biofilms. Current antimicrobial strategies often fail to control bacteria in the biofilm mode of growth. Treatment failure is particularly frequent in association with intracorporeal or transcutaneous medical devices and compromised host immunity. The rising prevalence of these risk factors over the last decades has paralleled the increase in biofilm infections. This review discusses the shortcomings of current therapies against biofilms both in theory and with clinical examples. Biofilm characteristics are described with a focus on new diagnostic and therapeutic targets.

Activity of imipenem against Klebsiella pneumoniae biofilms in vitro and in vivo

Encapsulated Klebsiella pneumoniae has emerged as one of the most clinically relevant and more frequently encountered opportunistic pathogens in combat wounds as the result of nosocomial infection. In this report, we show that imipenem displayed potent activity against established K. pneumoniae biofilms under both static and flow conditions in vitro. Using a rabbit ear model, we also demonstrated that imipenem was highly effective against preformed K. pneumoniae biofilms in wounds.

In vitro effectiveness of colistin, tigecycline and levofloxacin alone and combined with clarithromycin and/or heparin as lock solutions against embedded Acinetobacter baumannii strains

OBJECTIVES

To determine the in vitro stability and efficacy of colistin, tigecycline and levofloxacin alone or in combination with clarithromycin and/or heparin as lock solutions against biofilm-embedded Acinetobacter baumannii strains.

METHODS

Candidate antibiotics (colistin, tigecycline and levofloxacin) were investigated in vitro, either alone or in combination with clarithromycin and/or heparin in solution. The efficacy of antibiotic lock solutions was tested in an in vitro catheter biofilm model against A. baumannii isolated from catheter-related bacteraemia.

RESULTS

Candidate antibiotics at 400× MICs combined with clarithromycin (200 mg/mL) and/or heparin (1000 U/mL) were compatible. Colistin, tigecycline and levofloxacin and their combinations with clarithromycin demonstrated bactericidal activity against the biofilm-embedded A. baumannii strains. Compared with other antibiotics alone, the lock solution including only colistin was the best agent to eradicate A. baumannii embedded in the catheter model. When tested antibiotics were used in combination with clarithromycin, the combinations were significantly more effective and more rapid in reducing the live cell number or eliminating A. baumannii colonization in biofilms than each of the antibiotics alone.

CONCLUSIONS

Catheter lock solutions containing colistin may have the most promise for treating or preventing biofilm-producing catheter infections caused by A. baumannii. Clarithromycin was ultimately effective with the studied antibiotics to reduce live cell number or eradicate A. baumannii colonization in biofilms and could serve as an antibiotic enhancer. Our in vitro model findings now warrant clinical trials to investigate their real role in the management of catheter-related bacteraemia.

Biofilm elimination on intravascular catheters: important considerations for the infectious disease practitioner

The presence of biofilms on intravascular catheters and their role in catheter-related bloodstream infections is well accepted. The tolerance of catheter-associated biofilm organisms toward systemic antimicrobial treatments and the potential for development of antimicrobial resistance in the health care environment underscores the importance of alternative treatment strategies. Biofilms are microbial communities that exhibit unique characteristics that must be considered when evaluating the potential of biofilm prevention or control strategies. Because biofilm-associated infections do not respond consistently to therapeutically achievable concentrations of many antimicrobial agents, treatments that are more effective against slowly growing biofilm cells or combination treatments that can penetrate the biofilm matrix may be more effective. Alternative strategies that do not incorporate antimicrobial drugs have also been investigated. These approaches have the potential to prevent or eradicate biofilms on indwelling intravascular catheters and prevent or resolve catheter-related infections.

Roxithromycin inhibits tumor necrosis factor-alpha-induced matrix metalloproteinase-1 expression through regulating mitogen-activated protein kinase phosphorylation and Ets-1 expression

BACKGROUND AND OBJECTIVE

In periodontitis, matrix metalloproteinases (MMPs) are upregulated in response to locally released inflammatory cytokines, resulting in pathologic processes. Roxithromycin is a 14-membered ring macrolide antibiotic with broad-spectrum antibacterial effects against oral pathogens and immunomodulatory effects. Recently, we reported that roxithromycin inhibits tumor necrosis factor (TNF)-alpha-induced vascular endothelial growth factor expression in human periodontal ligament (HPDL) cell cultures. In the present study, we examined the effect of roxithromycin on TNF-alpha-induced MMP-1 production by HPDL cells.

MATERIAL AND METHODS

Cultured cells were incubated with 1% fetal bovine serum for 24 h, followed by treatment with 10 ng/ml TNF-alpha, 10 microM roxithromycin, and mitogen-activated protein kinase inhibitor at various concentrations. Culture supernatants and sediments were collected at different time-points and used for enzyme-linked immunosorbent assays, and northern and western blot analyses.

RESULTS

In HPDL cell cultures, roxithromycin strongly inhibited TNF-alpha-induced MMP-1 mRNA expression and production. The inhibition of MMP-1 gene expression by roxithromycin was dependent on de novo protein synthesis and was regulated at the transcriptional level. Roxithromycin significantly inhibited TNF-alpha-induced c-Jun N-terminal kinase activation (JNP) and marginally inhibited extracellular signal-regulated kinase (ERK) 1/2 activation, but not p38 mitogen-activated protein kinase activation. Furthermore, roxithromycin reduced the induction of Ets-1, one of the critical factors in MMP-1 transcription.

CONCLUSION

Roxithromycin inhibits TNF-alpha-mediated MMP-1 induction through the downregulation of ERK1/2 and JNK activation and the subsequent reduction of Ets-1, suggesting that roxithromycin may have therapeutic use in periodontitis and other chronic inflammatory conditions involving MMP-1 induction.

Bacteria and wound healing

PURPOSE OF REVIEW

Wound healing is a complex process with many potential factors that can delay healing. There is increasing interest in the effects of bacteria on the processes of wound healing. All chronic wounds are colonized by bacteria, with low levels of bacteria being beneficial to the wound healing process. Wound infection is detrimental to wound healing, but the diagnosis and management of wound infection is controversial, and varies between clinicians.

RECENT FINDINGS

There is increasing recognition of the concept of critical colonization or local infection, when wound healing may be delayed in the absence of the typical clinical features of infection. The progression from wound colonization to infection depends not only on the bacterial count or the species present, but also on the host immune response, the number of different species present, the virulence of the organisms and synergistic interactions between the different species. There is increasing evidence that bacteria within chronic wounds live within biofilm communities, in which the bacteria are protected from host defences and develop resistance to antibiotic treatment.

SUMMARY

An appreciation of the factors affecting the progression from colonization to infection can help clinicians with the interpretation of clinical findings and microbiological investigations in patients with chronic wounds. An understanding of the physiology and interactions within multi-species biofilms may aid the development of more effective methods of treating infected and poorly healing wounds. The emergence of consensus guidelines has helped to optimize clinical management.

Assessment of Streptococcus pyogenes microcolony formation in infected skin by confocal laser scanning microscopy

BACKGROUND

Streptococcus pyogenes and Staphylococcus aureus are often simultaneously detected from many cases of non-bullous impetigo with atopic dermatitis.

OBJECTIVES

Using confocal laser scanning microscopy (CLSM), to investigate formation of S. pyogenes microcolonies in skin lesions.

METHODS

The S. pyogenes cells in the stationary growth phase alone were strongly stained with fluorescein isothiocyanate-concanavalin A (FITC-ConA), and this staining was reduced by pretreatment with amylase. Although the components of sugars in glycocalyx produced by S. pyogenes cells are unknown, we suggested that the materials stained by FITC-ConA were consistent with the presence of ConA-reactive sugars in glycocalyx produced by S. pyogenes cells.

RESULTS

S. pyogenes cells associated with streptococcal impetigo skin and croton-oil inflamed mouse skin formed microcolonies encircled by materials (glycocalyx) that stained strongly with FITC-ConA, and these findings were consistent with those in biofilms. In croton-oil inflamed mouse skin, polymorphonuclear leukocytes (PMNs) infiltrated to just below the epidermis in the cefdinir-treated group but only to the middle dermis in the cefdinir-non-treated group. In this case S. pyogenes and S. aureus cells formed separate microcolonies and existed independently in the outer walls of pustule lesions of streptococcal impetigo.

CONCLUSION

In skin infections, S. pyogenes and S. aureus formed aggregates of microcolonies (similar to that in biofilms) encircled by glycocalyx, which can make the infection hard to eradicate using an antimicrobial agent alone. The effect of conventional antimicrobial agents against biofilm is mainly due to the increase of the invasion of PMNs into the biofilm.

Confocal laser scanning microscopic observation of glycocalyx production by Staphylococcus aureus in skin lesions of bullous impetigo, atopic dermatitis and pemphigus foliaceus

BACKGROUND

Glycocalyx collapses during dehydration to produce electron-dense accretions. Confocal laser scanning microscopy (CLSM) may be used to visualize fully hydrated microbial biofilms.

OBJECTIVES

Using CLSM, to analyse glycocalyx production by Staphylococcus aureus cells in skin lesions of bullous impetigo, atopic dermatitis and pemphigus foliaceus. A second objective was to compare numbers of S. aureus cells in tissue sections prepared by different methods for routine light microscopy.

METHODS

S. aureus cells in skin lesions of impetigo, atopic dermatitis and pemphigus were stained with safranin, and positive staining with fluorescein isothiocyanate-conjugated concanavalin A was considered to indicate the presence of glycocalyx.

RESULTS

All S. aureus cells tested in skin lesions of impetigo, atopic dermatitis and pemphigus were covered with glycocalyx and formed microcolonies. The numbers of S. aureus cells in a routine light microscopy section were significantly lower than those in a frozen section that had not been dehydrated with ethanol.

CONCLUSIONS

S. aureus cells generally produce glycocalyx in skin lesions of bullous impetigo, atopic dermatitis and pemphigus foliaceus, which accounts for the difficulty of removing S. aureus cells from these skin lesions. The glycocalyx may collapse during dehydration and most of the S. aureus cells may be carried away during preparation of routine light microscope sections.

Confocal laser scanning microscopic observation of glycocalyx production by Staphylococcus aureus in mouse skin: does S. aureus generally produce a biofilm on damaged skin?

BACKGROUND

Bacteria that adhere to damaged tissues encase themselves in a hydrated matrix of polysaccharides, forming a slimy layer known as a biofilm. This is the first report of detection of glycocalyx production by Staphylococcus aureus using confocal laser scanning microscopy (CLSM) on damaged skin tissues.

OBJECTIVES

To analyse glycocalyx production by S. aureus cells on damaged skin tissues and the influence of polymorphonuclear leucocytes (PMNs) and various antimicrobial agents on its production using CLSM in cyclophosphamide (Cy)-treated (neutropenic) or non-Cy-treated (normal) mice.

METHODS

S. aureus cells were inoculated on damaged skin tissues in neutropenic or normal mice with or without topical application of antimicrobial agents. S. aureus cells were stained with safranine, and positive staining with fluorescein isothiocyanate-conjugated concanavalin A was considered to indicate the presence of glycocalyx.

RESULTS

All S. aureus cells tested on damaged skin tissues formed microcolonies encircled by glycocalyx. The colony counts of S. aureus cells on croton oil dermatitis in normal mice treated with 2% fusidic acid ointment were about 100 times lower than those in neutropenic mice (control).

CONCLUSIONS

As S. aureus cells can generally produce a biofilm on damaged skin tissues, antimicrobial agents may not eradicate S. aureus cells without the help of PMNs. S. aureus glycocalyx may play a crucial role in colonization and adherence to damaged skin tissues.