Impact of selective antimicrobial agents on staphylococcal adherence to biomedical devices

A new dynamic in vitro model for evaluating antimicrobial activity against bacterial biofilms on central venous catheters

Central venous catheters (CVCs) are widely used for intravenous medication administration. However, biofilm formation along the catheter surface is the main most important cause of catheter-related bloodstream infections. Nowadays, several antimicrobial-coated catheters are available to prevent biofilm development. In this study, we introduced a new dynamic in vitro model to evaluate the antimicrobial activity against bacterial biofilms on CVCs. Rifampicin-minocycline-coated catheters and control catheters without antimicrobial component were assembled into the model to test the antimicrobial activity on external surface and internal surface. After 1 h irrigation of Staphylococcus epidermidis or Staphylococcus aureus preculture and 23 h irrigation of Trypticase Soy Broth, the viable adherent organism was collected and counted. The enumeration results showed that the number of bacteria attached to antibacterial catheter was significantly less than that of the control catheter, both on external surface (P < 0.05) and internal surface (P < 0.05). The results were further confirmed by the scanning electron microscopy. In conclusion, the dynamic in vitro model can be applied to evaluate the antimicrobial activity against bacterial biofilms grown on the external and internal surfaces of CVCs used in clinical practice.IMPORTANCEFor the first time, a new dynamic in vitro model was constructed to evaluate the antimicrobial activity against bacterial biofilms on central venous catheters (CVCs) on both external surface and internal surface. This model could be applied to evaluate the antimicrobial activity against bacterial biofilms not only on CVCs but also other types of catheters.

Treatment of long-term catheter-related bloodstream infections with short-course Daptomycin lock and systemic therapy associated with Taurolidine-lock: A multicenter experience

PURPOSE

Few studies describe the efficacy of antibiotic lock therapy (ALT) in long-term catheter-related bloodstream (CRBSI) infections. We applied local protocols combining Daptomycin (DPT) and Taurolidine ALT, associated with systemic antibiotic treatment (SAT), for conservative management of coagulase-negative Staphylococci (CoNS) CRBSI.

METHODS

Patients admitted for CoNS-associated CRBSI and treated with DPT and Taurolidine as ALT were retrospectively analyzed. Success was defined as catheter retention 30 days after ending treatment. Catheter removal within 30 days was considered as failure.

RESULTS

From April 2018 to September 2021, 22 subjects with CoNS-associated-CRBSI were included (95% with cancer, mean age 64 years, 59% male). Staphylococcus epidermidis was isolated in 82% of cases. Mean duration of DPT was 3.9 and 3 days as ALT and SAT, respectively. SAT also included Rifampin for 3 days. Taurolidine ALT was started on day 4 and was combined with oral SAT, that is, either Linezolid or Tedizolid. Mean duration of Taurolidine was 10.5 days, while total antibiotic treatment lasted 13.5 days. Clinical success and failure rates were 95% and 5%, respectively.

DISCUSSION

Short course DPT as ALT, combined with SAT and Taurolidine ALT, allowed high rates of conservative management of catheters in case of CoNS-associated-CRBSI.

Treatment of vascular graft infections: gentamicin-coated ePTFE grafts reveals strong antibacterial properties in vitro

Vascular graft infections (VGI) are severe complications in prosthetic vascular surgery with an incidence ranging from 1 to 6%. In these cases, synthetic grafts are commonly used in combination with antimicrobial agents. Expanded polytetrafluoroethylene (ePTFE) is in clinical use as a synthetic graft material and shows promising results by influencing bacterial adhesion. However, the literature on antibiotic-bound ePTFE grafts is scarce. Gentamicin is a frequently used antibiotic for local treatment of surgical site infections, but has not been evaluated as antimicrobial agent on ePTFE grafts. In this study, we examine the antimicrobial efficacy and biocompatibility of novel types of gentamicin-coated ePTFE grafts in vitro. ePTFE grafts coated with gentamicin salt formulations with covalently-bound palmitate were evaluated in two drug concentrations (GP1.75% and GP3.5%). To investigate effects from types of formulations, also suspensions of gentamicin in palmitate as well as polylactide were used at comparable levels (GS + PA and GS + R203). Antibacterial efficacies were estimated by employing a zone of inhibition, growth inhibition and bacterial adhesion assay against Staphylococcus aureus (SA). Cytotoxicity was determined with murine fibroblasts according to the ISO standard 10993-5. Gentamicin-coated ePTFE grafts show low bacterial adherence and strong antibacterial properties in vitro against SA. Bactericidal inhibition lasted until day 11. Highest biocompatibility was achieved using gentamicin palmitate GP1.75% coated ePTFE grafts. ePTFE grafts with gentamicin-coating are effective in vitro against SA growth and adherence. Most promising results regarding antimicrobial properties and biocompatibility were shown with chemically bounded gentamicin palmitate GP1.75% coatings. Graphical abstract.

Open wounds and rifampicin therapy are associated with rifampicin resistance among staphylococcal vascular graft/endograft infections

Background

Optimal timing for rifampicin combination therapy in patients with staphylococcal vascular graft/endograft infection (S-VGEI) is unknown. Experts recommend adding rifampicin after lowering bacterial load by surgery and wound closure.

Objectives

To assess predictors of rifampicin resistance among staphylococci isolated from patients in the Vascular Graft Infection Cohort Study.

Methods

We included prospective patients with S-VGEI diagnosis from 1 January 2002 to 30 June 2020. We retrospectively assessed determinants of rifampicin resistance using exact logistic regression and described survival with Kaplan–Meier curves.

Results

We analysed 513 Staphylococcus spp. among 143 predominantly male (82%) patients with a median age of 68 years (IQR 60–75). Thereof, 82 (57%) received a rifampicin combination therapy and 61 (43%) received an antimicrobial therapy without rifampicin. Among 82 patients with rifampicin, 26/26 patients with any rifampicin resistance had open wounds with a strong association of rifampicin resistance with rifampicin treatment while having open wounds (OR 37, 95% CI 6.1 to ∞). Among 75 patients with a rifampicin combination therapy and rifampicin-susceptible staphylococci at S-VGEI diagnosis, 12/12 patients with a secondary rifampicin-resistant isolate had an open wound (OR 14, 95% CI 2.1 to ∞).

Conclusions

Rifampicin should be started after wound closure due to increased risk of rifampicin resistance observed while having open wounds or second-look surgeries among patients with S-VGEI.

Antibiotic Lock Therapy with Linezolid for the Treatment of Persistent Catheter-Related Infection in Children with Cancer

Objective Central venous catheter (CVC) colonization is a common problem in the pediatric oncology department. Initial colonization of CVC by coagulase-negative staphylococci (CoNS), Staphylococcus aureus, and enterococci is followed by the growth of intraluminal biofilm formation, and results in antibiotic therapy failure. The removal of the old CVC and insertion of new CVC is a difficult and expensive procedure in small children with cancer. The present article aimed to study our treatment results of antibiotic lock therapy (ALT) with linezolid in pediatric cancer patients.

Methods This study was planned as retrospective presentation of case series with eight pediatric cancer patients treated with 11 courses of systemic and linezolid lock therapy. Demographic information, clinical findings, laboratory data, blood culture results, complications, and outcome were collected for each patient retrospectively and descriptive statistical methods were used.

Results Prior to treatment, peripheral and CVC blood culture results showed Staphylococcus epidermidis in seven patients and Staphylococcus hominis in four patients. All pathogens were susceptible to vancomycin and teicoplanin; first-line treatment was vancomycin in six and teicoplanin in five patients. After first-line treatment, peripheral blood cultures of all patients were negative, whereas blood cultures from CVC remained positive. During second-line therapy with linezolid, microbiological eradication was achieved on the fourth day of treatment in each patient. Median catheter survival time for all patients was 14 (range: 8–30) months. No side effects were observed during the treatment and no resistant organisms were documented.

Conclusion Although multicentric prospective controlled trials will be required to provide more generalizable results, we suggest that systemic antibiotics combined with linezolid lock therapy used in pediatric cancer patients may be an effective option in treating catheter-related bloodstream infection (CRBSI) and prolonging CVC survival when CoNS are identified.

Antibiotic Delivery Strategies to Treat Skin Infections When Innate Antimicrobial Defense Fails

The epidermal skin barrier protects the body from a host of daily challenges, providing protection against mechanical insults and the absorption of chemicals and xenobiotics. In addition to the physical barrier, the epidermis also presents an innate defense against microbial overgrowth. This is achieved through the presence of a diverse collection of microorganisms on the skin (the "microbiota") that maintain a delicate balance with the host and play a significant role in overall human health. When the skin is wounded, the local tissue with a compromised barrier can become colonized and ultimately infected if bacterial growth overcomes the host response. Wound infections present an immense burden in healthcare costs and decreased quality of life for patients, and treatment becomes increasingly important because of the negative impact that infection has on slowing the rate of wound healing. In this review, we discuss specific challenges of treating wound infections and the advances in drug delivery platforms and formulations that are under development to improve topical delivery of antimicrobial treatments.

Daptomycin to bone and joint infections and prosthesis joint infections: a systematic review

Backgroud

Daptomycin has been used in bone and joint infections (BJI) and prosthesis joint infections (PJI) considering spectrum of activity and biofilm penetration. However, the current experience is based on case reports, case series, cohorts, and international surveys. The aim of this systematic review was to evaluate studies about daptomycin treatment efficacy in BJI/PJI compared to other antibiotic regimens.

Methods

PubMed, LILACS, Scielo and Web of Science databases were searched for articles about daptomycin and treatment of BJI and PJI from inception to March 2018. Inclusion criteria were any published researches that included patients with BJI treated with daptomycin. Diagnosis of BJI was based on clinical, laboratory and radiological findings according to IDSA guidelines.

Results

From 5107 articles, 12 articles were included. Only three studies described the outcomes of patients with BJI treated with daptomycin with comparator regimen (vancomycin, teicoplanin and oxacillin). Studies presented large heterogeneity regarding device related infections, surgical procedures, and daptomycin regimens (varied from 4 mg/kg to 10 mg/kg). A total of 299 patients have been included in all studies (184 infections associated with orthopedic disposal and 115 osteomyelitis/septic arthritis). Two hundred and thirty-three patients were treated with daptomycin. The clinical cure rates on device related and non-device related infections (i.e. osteomyelitis) were 70% and 78%, respectively. Compared to all regimens evaluated, daptomycin group outcomes were non-inferior.

Conclusion

Although a randomized clinical trial is needed, this systematic review tends to support daptomycin usage for bone and joint infections.

Update on the Role of Infection and Biofilms in Wound Healing: Pathophysiology and Treatment

BACKGROUND

Chronic wounds, and among these infected diabetic foot ulcers, are a worldwide problem. The poor treatment outcomes result in high healthcare costs, amputations, a decreased quality of life, and an increased mortality. These outcomes are influenced by several factors, including biofilm formation. A biofilm consists of pathogenic bacteria that are encased in an exopolysaccharide layer and communicate through secretion of signaling molecules. Bacteria that live in a biofilm are refractory to host responses and treatment.

METHODS

We performed a nonsystematic review of the currently published to-date medical biofilm literature. The review summarizes the evidence of biofilm in chronic wounds, the role of biofilm in wound healing, detection of biofilm, and available antibiofilm treatments. Articles containing basic science and clinical research, as well as systematic reviews, are described and evaluated. The articles have variable levels of evidence. All articles have been peer reviewed and meet the standards of evidence-based medicine.

RESULTS

Both animal and human studies have identified biofilm in chronic wounds and have suggested that healing might be influenced by its presence. A promising development in biofilm detection is rapid molecular diagnostics combined with direct microscopy. This technique, rather than classic culture, might support individualized treatment in the near future. A wide range of treatments for chronic wounds also influence biofilm formation. Several agents that specifically target biofilm are currently being researched.

CONCLUSIONS

Biofilm formation has a substantial role in chronic wounds. Several diagnostic and therapeutic methods against biofilm are currently being developed.

Inactivation of Acinetobacter baumannii Biofilms on Polystyrene, Stainless Steel, and Urinary Catheters by Octenidine Dihydrochloride

Acinetobacter baumannii is a major nosocomial pathogen causing human infections with significant mortality rates. In most cases, infections are acquired through exposure to A. baumannii biofilms that persist on contaminated hospital equipment and surfaces. Thus, it is imperative to develop effective measures for controlling A. baumannii biofilms in nosocomial settings. This study investigated the efficacy of octenidine dihydrochloride (OH), a new generation disinfectant for reducing A. baumannii biofilms on polystyrene, stainless steel and catheters. OH at 0.3% (5 mM), 0.6% (10 mM), and 0.9% (15 mM) was effective in significantly inactivating A. baumannii biofilms on all tested surfaces (P < 0.05). Furthermore, OH was equally effective in inactivating biofilms of multidrug resistant and drug susceptible A. baumannii isolates. In addition, confocal imaging revealed the predominance of dead cells in the OH-treated samples in comparison to the control. Further, scanning electron microscopy of biofilms formed on catheters revealed that OH treatment significantly reduced A. baumannii biofilm populations in corroboration with our antibiofilm assay. These data underscore the efficacy of OH in inactivating A. baumannii biofilms, thereby suggesting its potential use as a disinfectant or a catheter lock solution to control A. baumannii infections.

Effects of vancomycin, daptomycin, and tigecycline on coagulase-negative staphylococcus biofilm and bacterial viability within biofilm: an in vitro biofilm model

Bacteria may hide in a hydrated polysaccharide matrix known as a biofilm. The structure of the bacterial biofilm renders phagocytosis difficult and increases antibiotic resistance. We hypothesized that repeated doses of antibiotics have an effect on bacteria within the biofilm and that it could inhibit or eradicate biofilm formation. Two clinical biofilm-positive coagulase-negative staphylococcus isolates were evaluated. The effects of antibiotics on preformed and nascent biofilm and on bacterial eradication within the biofilm were determined using different doses of vancomycin, daptomycin, and tigecycline for different durations in an in vitro biofilm model. Vancomycin neither penetrated the biofilm nor had any microbicidal effect on bacteria within the biofilm. Daptomycin had a microbicidal effect on bacteria within the biofilm but had no effect on biofilm inhibition and eradication (independent from dose and treatment time). Tigecycline inhibited and eradicated biofilm formation and had a microbicidal effect on bacteria within the biofilm. In conclusion, (i) biofilm formation appeared to be a major barrier to vancomycin activity, (ii) daptomycin had an antimicrobial effect on the bacteria within the biofilm but not on the biofilm burden, and (iii) tigecycline had effects both on bacteria within the biofilm and on biofilm burden. Thus, both tigecycline and daptomycin might be promising candidates for the treatment of biofilm infections.

New in vitro and in vivo models to evaluate antibiotic efficacy in Staphylococcus aureus prosthetic vascular graft infection

OBJECTIVE

Prosthetic vascular graft infection (PVGI) is an emerging disease, mostly caused by staphylococci, with limited data regarding efficacy of current antistaphylococcal agents. We aimed to assess the efficacy of different antibiotic regimens.

METHODS

Six different strains of MSSA and MRSA were used. We compared results of minimal biofilm inhibitory and eradicating concentrations (MBICs and MBECs) obtained with a Calgary Biofilm Pin Lid Device (CBPD) with those yielded by an original Dacron(®)-related minimal inhibitory and eradicating concentration measure model. We then used a murine model of Staphylococcus aureus vascular prosthetic material infection to evaluate efficacy of different antibiotic regimens: vancomycin and daptomycin combined or not with rifampicin for MRSA and the same groups with cloxacillin and cloxacillin combined with rifampicin for MSSA.

RESULTS

We demonstrated that classical measures of MBICs and MBECs obtained with a CPBD could overestimate the decrease in antibiotic susceptibility in material-related infections and that the nature of the support used might influence the measure of biofilm susceptibility, since results yielded by our Dacron(®)-related minimal eradicating assay were lower than those found with a plastic device. In our in vivo model, we showed that daptomycin was significantly more bactericidal than comparators for some strains of MRSA or MSSA but not for all. For the majority of strains, it was as efficient as comparators. The addition of rifampicin to daptomycin did not enhance daptomycin efficacy.

CONCLUSIONS

Despite the heterogeneity of results according to bacterial strains, these innovative models represent an option to better evaluate the in vitro efficacy of antibiotics on Dacron(®)-related biofilm S. aureus infections, and to screen different antibiotic regimens in a mouse model of PVGIs.

Medical treatment of prosthetic vascular graft infections: Review of the literature and proposals of a Working Group

More than 400000 vascular grafts are inserted annually in the USA. Graft insertion is complicated by infection in 0.5-4% of cases. Vascular graft infections (VGIs) are becoming one of the most frequent prosthesis-related infections and are associated with considerable mortality, ranging from 10 to 25% within 30 days following the diagnosis. Treatment of VGI is based on urgent surgical removal of the infected graft followed by prolonged antibiotherapy. Data regarding the best antibiotherapy to use are lacking since no well designed trial to study antimicrobial treatment of VGI exists. Moreover, since VGIs demonstrate very specific pathophysiology, guidelines on other material-related infections or infective endocarditis treatment cannot be entirely applied to VGI. A French multidisciplinary group gathering infectious diseases specialists, anaesthesiologists, intensivists, microbiologists, radiologists and vascular surgeons was created to review the literature dealing with VGI and to make some proposals regarding empirical and documented antibiotic therapy for these infections. This article reveals these proposals.

Efficacy of linezolid, teicoplanin, and vancomycin in prevention of an experimental polytetrafluoroethylene graft infection model caused by methicillin-resistant Staphylococcus aureus

Background

The aim of this study was to evaluate the effectiveness of linezolid, teicoplanin, and vancomycin in prevention of prosthetic vascular graft infections in a vascular graft infection model.

Material/Methods

Fifty rats were divided into 5 groups. A polytetrafluoroethylene graft was implanted on the back of each rat. Methicillin-resistant Staphylococcus aureus (MRSA) strain was inoculated into all rats except Group 1. Group 2 was not given any treatment, Group 3 received linezolid, Group 4 received vancomycin, and Group 5 received teicoplanin. The grafts were removed for microbiological and histological examinations on the 7^th day. In addition, C-reactive protein and prealbumin levels and leukocyte counts in obtained blood specimens were determined.

Results

Group 1 did not have infection. Group 2 had bacteria 5.7×10⁴ CFU/cm². Group 3 and Group 4 had less bacterial growth. Group 5 had no bacterial growth. The number of bacteria was significantly higher in Group 2 than in the other experimental groups and the control group (p<0.001). Although there was no bacterial growth in Group 5, it did not significantly differ from Group 3 and Group 4. Group 2 had a significantly higher CRP level and leukocyte count and a significantly lower prealbumin level than the other groups.

Conclusions

Linezolid, teicoplanin, and vancomycin are effective in prevention of prosthetic vascular graft infections.

Approach to chronic wound infections

Infection is the likeliest single cause of delayed healing in healing of chronic open wounds by secondary intention. If neglected it can progress from contamination to colonization and local infection through to systemic infection, sepsis and multiple organ dysfunction syndrome, and it can be life-threatening. Infection in chronic wounds is not as easy to define as in acute wounds, and is complicated by the presence of biofilms. There is, as yet, no diagnostic for biofilm presence, but it contributes to excessive inflammation - through excessive and prolonged stimulation of nitric oxide, inflammatory cytokines and free radicals - and activation of immune complexes and complement, leading to a delay in healing. Control of biofilm is a key part of chronic wound management. Maintenance debridement and use of topical antimicrobials (antiseptics) are more effective than antibiotics, which should be reserved for treating spreading local and systemic infection. The continuing rise of antimicrobial resistance to antibiotics should lead us to reserve their use for these indications, as no new effective antibiotics are in the research pipeline. Antiseptics are effective through many mechanisms of action, unlike antibiotics, which makes the development of resistance to them unlikely. There is little evidence to support the theoretical risk that antiseptics select resistant pathogens. However, the use of antiseptic dressings for preventing and managing biofilm and infection progression needs further research involving well-designed, randomized controlled trials.

Clinical and microbiological aspects of biofilm-associated surgical site infections

While microbial biofilms have been recognized as being ubiquitous in nature for the past 40 years, it has only been within the past 20 years that clinical practitioners have realized that biofilm play a significant role in both device-related and tissue-based infections. The global impact of surgical site infections (SSIs) is monumental and as many as 80 % of these infections may involve a microbial biofilm. Recent studies suggest that biofilm- producing organisms play a significant role in persistent skin and soft tissue wound infections in the postoperative surgical patient population. Biofilm, on an organizational level, allows bacteria to survive intrinsic and extrinsic defenses that would inactivate the dispersed (planktonic) bacteria. SSIs associated with biomedical implants are notoriously difficult to eradicate using antibiotic regimens that would typically be effective against the same bacteria growing under planktonic conditions. This biofilm-mediated phenomenon is characterized as antimicrobial recalcitrance, which is associated with the survival of a subset of cells including "persister" cells. The ideal method to manage a biofilm-mediated surgical site wound infection is to prevent it from occurring through rational use of antibiotic prophylaxis, adequate skin antisepsis prior to surgery and use of innovative in-situ irrigation procedures; together with antimicrobial suture technology in an effort to promote wound hygiene at the time of closure; once established, biofilm removal remains a significant clinical problem.

Risk factors for failure in early prosthetic joint infection treated with debridement. Influence of etiology and antibiotic treatment

PURPOSES

The aim of the present study was to evaluate the importance of isolated microorganisms according to the Gram stain and the type of antibiotic received on the outcome of early prosthetic joint infection (PJI) treated with debridement, antibiotics and implant retention (DAIR).

METHODS

From January 1999 to December 2009, all patients with an early PJI were prospectively registered in a database and they were retrospectively reviewed for this study.

RESULTS

During the study period, 160 patients met the inclusion criteria of the study. After a mean (SD) post-debridement follow-up of 5.2 (2.5) years, 117 patients (73.1%) were considered to be in remission and 43 (26.9%) were classified as failure. Variables associated with failure were liver cirrhosis (66.7% vs. 22.8%, p=0.001), diagnosis within the first 30 days from arthroplasty (30.4% vs. 8.0%, p=0.020), C-reactive protein (CRP) >12 mg/dl (46.7% vs. 21.2%, p=0.005), microorganism isolated in all deep samples (31.1% vs. 16.0%, p=0.047) and Gram-negative (GN) infection not treated with a fluoroquinolone (57.1% vs. 20.0%, P=0.004). Gram-positive (GP) infection not treated with rifampin was close to be statistically significantly associated with failure (34.4% vs. 19.2%, p=0.067). A multivariate analysis identified liver cirrhosis (OR: 12.4 CI95%: 3.1-49.7, p<0.001), CRP-value (OR: 1.06 CI95%: 1.0-1.11, p=0.049), and when a GN-infection was not treated with a fluoroquinolone (OR: 6.5, CI95%: 1.8-23.8, p=0.005) as independent predictors of failure.

CONCLUSION

The remission rate of PJI treated with DAIR after 3 years of follow-up was 73%. The main predictors of failure were liver cirrhosis, the selected antibiotic most specially fluoroquinolones for GN and rifampin for GP infections, the C-reactive protein and the number of samples culture positive as a potential surrogate markers of bacterial density.

Tolerability of High Doses of Daptomycin in the Treatment of Prosthetic Vascular Graft Infection: A Retrospective Study

INTRODUCTION

In treatment of prosthetic vascular graft infection (PVGI), appropriate antimicrobial treatment is crucial for controlling the septic process and preventing re-infection of the new graft. Glycopeptides are the mainstay of treatment for device-related infections by methicillin-resistant Staphylococcus aureus strains, but with some limitations, especially concerning vancomycin-intermediate and glycopeptide-intermediate S. aureus. We report our experience using a high dose of daptomycin (DAP) for treatment of PVGI.

METHODS

We reviewed medical reports of 26 patients treated with high doses of DAP (>8 mg/kg) and beta-lactams/aminosides for PVGI, defined as positive bacterial culture of intraoperative specimens or blood samples and/or clinical, biological, and radiological signs of infection. Clinical success was defined by resolution of all clinical signs at the end of follow-up, without the need for additional antibiotic therapy, and/or negative culture in case of new surgery.

RESULTS

Cultures of intraoperative samples were positive in 21 patients (80.8%). Blood and intraoperative cultures were concomitantly positive in 10 patients. The main microorganism identified in microbiological samples was S. aureus (n = 18). Surgery was performed in 23 patients (88.4%). The mean duration of the DAP regimen was 12.3 ± 11.9 days. DAP was discontinued in 26 patients [need to switch to microbiological results (n = 19), bacterial pneumonia (n = 2), and increased creatine phosphokinase levels (n = 4)]. One patient had myalgia, while 9 received concomitant statins.

CONCLUSION

High-dose DAP therapy shows a satisfactory toxicity profile even in severely ill patients with multiple comorbidities, and may favorably compete with vancomycin, especially concerning the risk of induced nephrotoxicity.

Antibiofilm Effect of Octenidine Hydrochloride on Staphylococcus aureus, MRSA and VRSA

Millions of indwelling devices are implanted in patients every year, and staphylococci (S. aureus, MRSA and vancomycin-resistant S. aureus (VRSA)) are responsible for a majority of infections associated with these devices, thereby leading to treatment failures. Once established, staphylococcal biofilms become resistant to antimicrobial treatment and host response, thereby serving as the etiological agent for recurrent infections. This study investigated the efficacy of octenidine hydrochloride (OH) for inhibiting biofilm synthesis and inactivating fully-formed staphylococcal biofilm on different matrices in the presence and absence of serum protein. Polystyrene plates and stainless steel coupons inoculated with S. aureus, MRSA or VRSA were treated with OH (zero, 0.5, one, 2 mM) at 37 °C for the prevention of biofilm formation. Additionally, the antibiofilm effect of OH (zero, 2.5, five, 10 mM) on fully-formed staphylococcal biofilms on polystyrene plates, stainless steel coupons and urinary catheters was investigated. OH was effective in rapidly inactivating planktonic and biofilm cells of S. aureus, MRSA and VRSA on polystyrene plates, stainless steel coupons and urinary catheters in the presence and absence of serum proteins. The use of two and 10 mM OH completely inactivated S. aureus planktonic cells and biofilm (>6.0 log reduction) on all matrices tested immediately upon exposure. Further, confocal imaging revealed the presence of dead cells and loss in biofilm architecture in the OH-treated samples when compared to intact live biofilm in the control. Results suggest that OH could be applied as an effective antimicrobial to control biofilms of S. aureus, MRSA and VRSA on appropriate hospital surfaces and indwelling devices.

Factors predictive of treatment failure in staphylococcal prosthetic vascular graft infections: a prospective observational cohort study: impact of rifampin

BACKGROUND

There exists considerable debate concerning management of prosthetic vascular graft infection (PVGI), especially in terms of antimicrobial treatment. This report studies factors associated with treatment failure in a cohort of patients with staphylococcal PVGI, along with the impact of rifampin (RIF).

METHODS

All data on patients with PVGI between 2006 and 2010 were reviewed. Cure was defined as the absence of evidence of infection during the entire post-treatment follow-up for a minimum of one year. Failure was defined as any other outcome.

RESULTS

84 patients (72 M/12 F, median age 64.5 ± 11 y) with diabetes mellitus (n = 25), obesity (n = 48), coronary artery disease (n = 48), renal failure (n = 24) or COPD (n = 22) were treated for PVGI (median follow-up was 470 ± 469 d). PVGI was primarily intracavitary (n = 47). Staphylococcus aureus (n = 65; including 17 methicillin-resistant S. aureus) and coagulase-negative Staphylocococcus (n = 22) were identified. Surgical treatment was performed in 71 patients. In univariate analysis, significant risk factors associated with failure were renal failure (p = 0.04), aortic aneurysm (p = 0.03), fever (p = 0.009), aneurysm disruption (p = 0.02), septic shock in the peri-operative period (p = 0.005) and antibiotic treatment containing RIF (p = 0.03). In multivariate analysis, 2 variables were independently associated with failure:septic shock [OR 4.98: CI 95% 1.45-16.99; p=0.01] and antibiotic containing rifampin [OR: 0.32: CI95% 0.10-0.96; p=0.04].

CONCLUSION

Results of the present study suggest that fever, septic shock and non-use of antibiotic treatment containing RIF are associated with poor outcome.

Successful daptomycin lock therapy for implantable intra-arterial catheter infection in a patient with liver metastases of colon cancer

There are no data on how to manage implantable intra-arterial catheter (IAC) infections. We report the case of a patient with liver metastases of colon cancer treated by regional intra-arterial chemotherapy who presented a suspected IAC-related infection, in whom daptomycin systemic treatment and lock therapy allowed to cure the IAC infection.

In vitro efficacies and resistance profiles of rifampin-based combination regimens for biofilm-embedded methicillin-resistant Staphylococcus aureus

To compare the in vitro antibacterial efficacies and resistance profiles of rifampin-based combinations against methicillin-resistant Staphylococcus aureus (MRSA) in a biofilm model, the antibacterial activities of vancomycin, teicoplanin, daptomycin, minocycline, linezolid, fusidic acid, fosfomycin, and tigecycline alone or in combination with rifampin against biofilm-embedded MRSA were measured. The rifampin-resistant mutation frequencies were evaluated. Of the rifampin-based combinations, rifampin enhances the antibacterial activities of and even synergizes with fusidic acid, tigecycline, and, to a lesser extent, linezolid, fosfomycin, and minocycline against biofilm-embedded MRSA. Such combinations with weaker rifampin resistance induction activities may provide a therapeutic advantage in MRSA biofilm-related infections.

Modified intraatrial translocation for prosthetic mitral valve endocarditis

Despite prompt diagnosis and aggressive surgical treatment of prosthetic mitral valve endocarditis (PVE), morbidity and mortality remain high. Surgical strategies have mostly been limited to debridement and anatomic valve reinstallation. Alternative surgical techniques have been attempted sporadically against this mortal disease, either with protection by antibiotic sewing rings or by anatomic evacuation of infectious foci. These methods have not been performed concurrently, however, and their joint deployment might improve surgical outcome. We describe a surgical procedure of modified intraatrial translocation combined with sewing ring shielding, aimed at preventing the recurrence of severe methicillin-resistant staphylococci PVE in the mitral position.

[Daptomycin in outpatient antimicrobial parenteral therapy]

Daptomycin is a cyclic lipopeptide with a rapid bactericidal effect against Gram-positive bacteria. The pharmacokinetic properties of this drug allow once-daily intravenous infusion as the best posology (including a 2-minute bolus). Because of its ease of administration and excellent safety profile, daptomycin is a first-line agent for use as outpatient antimicrobial parenteral therapy (OPAT). The best evidence supporting this indication exists for the treatment of complicated and uncomplicated skin and soft tissue infections, as well as osteoarticular infections caused by Gram-positive bacteria. For the remaining indications, the use of daptomycin as OPAT should be analyzed in each patient. Information from the EUCORE Registry in Spain indicates that daptomycin has high rates of treatment success in both hospitalized patient and in those included in OPAT programs.

Novel fatty acid gentamicin salts as slow-release drug carrier systems for anti-infective protection of vascular biomaterials

Infections of vascular prostheses are still a major risk in surgery. The current work presents an in vitro evaluation of novel slow release antibiotic coatings based on new gentamicin fatty acid salts for polytetrafluoroethylene grafts. These grafts were coated with gentamicin sodium dodecyl sulfate, gentamicin laurate and gentamicin palmitate. Drug release kinetics, anti-infective characteristics, biocompatibility and haemocompatibility of developed coatings were compared to commercially available gelatin sealed PTFE grafts (SEALPTFE™) and knitted silver coated Dacron(®) grafts (InterGard(®)). Each gentamicin fatty acid coating showed a continuous drug release in the first eight hours followed by a low continuous release. Grafts coated with gentamicin fatty acids reduced bacterial growth even beyond pathologically relevant high concentrations. Cytotoxicity levels depending on drug formulation bringing up gentamicin palmitate as the most promising biocompatible coating. Thrombelastography studies, ELISA assays and an amidolytic substrate assay confirmed haemocompatibility of developed gentamicin fatty acid coatings comparable to commercially available grafts.

Daptomycin: local application in implant-associated infection and complicated osteomyelitis

BACKGROUND

The rise of highly resistant bacteria creates a persistent urge to develop new antimicrobial agents. This paper investigates the application of the lipopeptide antibiotic daptomycin in infections involving the human bone.

METHODS

Compressive and tensile strength testing of daptomycin-laden PMMA was performed referring to the ISO 5833. The microstructure of the antibiotic-laden PMMA was evaluated by scanning electron microscopy. Intracellular activity of daptomycin was determined by a human osteoblast infection model. Elution kinetics of the antibiotic-laden bone cement was measured by using a continuous flow chamber setup.

RESULTS

There was no significant negative effect of adding 1.225% and 7.5% per weight of daptomycin to the PMMA. There was no significant difference in intracellular activity comparing gentamicin to daptomycin. Elution of daptomycin from PMMA showed within the first-hour initial peak values of 15-20 μg/mL.

CONCLUSION

Daptomycin has a certain degree of activity in the intracellular environment of osteoblasts. Daptomycin admixed to PMMA remains bactericidal and does not significantly impair structural characteristics of the PMMA. The results of this paper suggest that daptomycin might be a potent alternative for treating osteomyelitis and implant-associated infection in trauma and orthopedic surgery caused by multiresistant strains.

Daptomycin and tigecycline have broader effective dose ranges than vancomycin as prophylaxis against a Staphylococcus aureus surgical implant infection in mice

Vancomycin is widely used for intravenous prophylaxis against surgical implant infections. However, it is unclear whether alternative antibiotics used to treat methicillin-resistant Staphylococcus aureus (MRSA) infections are effective as prophylactic agents. The aim of this study was to compare the efficacies of vancomycin, daptomycin, and tigecycline as prophylactic therapy against a methicillin-sensitive S. aureus (MSSA) or MRSA surgical implant infection in mice. MSSA or MRSA was inoculated into the knee joints of mice in the presence of a surgically placed medical-grade metallic implant. The efficacies of low- versus high-dose vancomycin (10 versus 110 mg/kg), daptomycin (1 versus 10 mg/kg), and tigecycline (1 versus 10 mg/kg) intravenous prophylaxis were compared using in vivo bioluminescence imaging, ex vivo bacterial counts, and biofilm formation. High-dose vancomycin, daptomycin, and tigecycline resulted in similar reductions in bacterial burden and biofilm formation. In contrast, low-dose daptomycin and tigecycline were more effective than low-dose vancomycin against the implant infection. In this mouse model of surgical implant MSSA or MRSA infection, daptomycin and tigecycline prophylaxis were effective over a broader dosage range than vancomycin. Future studies in humans will be required to determine whether these broader effective dose ranges for daptomycin and tigecycline in mice translate to improved efficacy in preventing surgical implant infections in clinical practice.

In vitro efficacy of fosfomycin-containing regimens against methicillin-resistant Staphylococcus aureus in biofilms

OBJECTIVES

To compare the in vitro antibacterial efficacy of antistaphylococcal antibiotics in combination with fosfomycin or rifampicin, using a biofilm model.

METHODS

The antibacterial activities of fusidic acid, linezolid, vancomycin, teicoplanin, rifampicin, minocycline, fosfomycin and tigecycline, individually and in fosfomycin or rifampicin combinations, were measured against planktonic or biofilm-embedded methicillin-resistant Staphylococcus aureus (MRSA) with susceptible and resistant breakpoint concentrations (SBCs and RBCs, respectively), using the MTT-staining method and by counting the number of cfu in the biofilms.

RESULTS

Linezolid alone at its SBC, and fosfomycin, linezolid, minocycline and tigecycline at their RBCs, exhibited killing effects on biofilm-embedded MRSA (P < 0.0001). Of the eight fosfomycin combinations studied, fosfomycin combined with linezolid, minocycline, vancomycin or teicoplanin at their respective SBCs, exhibited enhanced antibacterial activities (P < 0.0001) when compared with the control group, and outperformed rifampicin combinations (P < 0.01). The killing effects of fosfomycin combinations at their respective RBCs were better than those at their respective SBCs (P < 0.05). Significantly enhanced killing effects were observed with fosfomycin in combination with vancomycin or teicoplanin, compared with vancomycin or teicoplanin alone. For 10 randomly selected MRSA isolates, the results of colony counting in biofilms were comparable with those of the MTT-staining method.

CONCLUSIONS

Fosfomycin enhanced the activities of linezolid, minocycline, vancomycin and teicoplanin. These combinatorial treatments were even better than rifampicin combination regimens, and may provide therapeutic advantages in catheter-related or prosthetic joint infections.

Infections in vascular surgery

Infections in vascular surgery are usually of multifactorial nature resulting from a complex interplay of patient, surgical and environmental factors. Preventative measures initiated from the stage of pre-operative screening, maintenance of patient homeostasis and the use of organism-directed antibiotics can contribute to reduce infection rates. Graft preservation techniques are becoming increasingly popular as a method to treat established graft infections. In this article we report on the current trends and techniques on the management of infections in vascular surgery. Ongoing studies are required to continue to accumulate data on the effectiveness of these techniques.

[Daptomycin for the treatment of Gram-positive microorganisms in the critically-ill patient]

INTRODUCTION

Infections caused by multiresistant Gram-positive cocci have increased among critically ill patients admitted to the intensive care unit (ICU). In the last few years, treatment of these infections has changed due to better knowledge of the limitations of glycopeptides and the introduction of novel antimicrobials, such as daptomycin.

OBJECTIVES

To describe the characteristics of daptomycin that justify its administration in critically ill patients and to present data on the use of this antibiotic in patients admitted to Spanish ICUs.

MATERIAL AND METHOD

We reviewed the literature on daptomycin to identify the characteristics that may favor clinical response in critically ill patients. To describe the indications and modalities of use in critically patients, information from the European Cubicin(®) Outcome Registry and Experience (EUCORE) database of Spanish patients admitted to the ICU was employed.

RESULTS

The following favorable conditions were identified: a) scarce systemic response, maintaining high bactericidal activity, b) scarce impact on renal function, c) no requirement for monitoring of plasma levels, d) scarce selection of resistance, and d) excellent tolerability. To assess indications and the use of this agent in the ICU, 122 patients from the EUCORE database were analyzed. The indications were bacteremias (36.2%), complicated infections of the skin and soft tissues (27.6%), and endocarditis (19%). Prominent pathogens were Staphylococcus aureus (26%), S. epidermidis (25%), and other coagulase-negative staphylococci (12%). In 85.7% of patients, treatment was administered as second-line (rescue treatment). In 65 patients (52%), a dose of 6 mg/kg/day was used, with a mean treatment duration of 10.2 days. Overall clinical efficacy was 73.7%. No adverse effects leading to treatment withdrawal were recorded and no increases in creatine phosphokinase (CPK) levels greater than 10-fold the initial values were observed.

CONCLUSIONS

Daptomycin is a novel therapeutic option to be considered in the treatment of severe infections caused by Gram-positive cocci in critically-ill patients.

Successful salvage of peritoneal catheter in unresolved methicillin-resistant staphylococcus aureus peritonitis by combination treatment with daptomycin and rifampin

Peritoneal dialysis patients are at an increased risk of Gram-positive organism infections because of disrupted skin barrier function, presence of a peritoneal catheter, and a deficient immunological system. In particular, the treatment of methicillin-resistant Staphylococcus aureus (MRSA) infections is clinically challenging. Herein, we present a case of MRSA peritonitis that showed no response to a 14-day treatment with intraperitoneal vancomycin. To overcome unresponsiveness to vancomycin, we shifted the regimen to intraperitoneal daptomycin (given every 6 h through manual peritoneal dialysate exchanges) and oral rifampin (300 mg twice daily). The peritonitis resolved without sequelae or relapse. We suggest daptomycin and rifampin as an alternative combination therapy for MRSA infections that may otherwise remain unresolved.

Daptomycin antibiotic lock therapy in a rat model of staphylococcal central venous catheter biofilm infections

Antibiotic lock therapy (ALT) is an adjunctive procedure to prevent or treat central venous catheter infections, ensuing catheter-related bacteremia, and catheter-related metastatic infections. Daptomycin is a cyclic lipopeptide that is rapidly bactericidal against methicillin-susceptible and -resistant Staphylococcus aureus. The efficacies of daptomycin against central venous catheter biofilms, catheter-related bacteremia, and catheter-related metastatic infections were evaluated by adapting a previously reported central venous catheter biofilm model in rats. Combined daptomycin ALT and systemic dosing resulted in the clearance of an established in vivo S. aureus central venous catheter biofilm after just two daily ALT treatments (30 min with daptomycin at 5 mg/ml) with concurrent systemic daptomycin dosing (40 mg/kg of body weight/day subcutaneously [s.c.]; equivalent exposure of 6 mg/kg/day in people). Daptomycin ALT solutions formulated in either saline or lactated Ringer's solution were equally fast in eradicating established in vivo methicillin-resistant Staphylococcus epidermidis (MRSE) central venous catheter biofilms. However, the lactated Ringer's formulation was superior to that of saline in sustaining the bacterial clearance of treated central venous catheters (83% versus 50%). In MRSE-infected central venous catheter studies, 3 days of daptomycin or vancomycin ALT (18 h at 5 mg/ml) with systemic s.c. dosing (40 mg/kg/day daptomycin or 100 mg/kg/day vancomycin) was equally effective 1 week posttherapy in maintaining cleared central venous catheters (90% [n = 10] versus 100% [n = 8]). These results suggest that daptomycin ALT, along with systemic dosing, could be an effective treatment option for the prevention or eradication of staphylococcal central venous catheter biofilm infections, thereby reducing the occurrence of catheter-related bacteremia or catheter-related metastatic infections.