Vancomycin for Staphylococcus aureus endocarditis in intravenous drug users

A Retrospective Study of Staphylococcus aureus Bacteremia in a Tertiary Hospital and Factors Associated with Mortality

Staphylococcus aureus bacteremia (SAB) is a severe infection frequently associated with significant morbidity and mortality. Recent studies have shown that SAB mortality has decreased during the last decades. However, about 25% of patients suffering from the disease will ultimately die. Hence, there is an urgent need for more timely and efficient treatment of patients with SAB. The aim of the present study was to retrospectively evaluate a cohort of SAB patients hospitalized in a tertiary hospital and to identify factors independently associated with mortality. All 256 SAB patients hospitalized from January 2005 to December 2021 in the University Hospital of Heraklion, Greece, were evaluated. Their median age was 72 years, while 101 (39.5%) were female. Most SAB patients were cared for in medical wards (80.5%). The infection was community-acquired in 49.5%. Among all strains 37.9% were methicillin-resistant S. aureus (MRSA), however, definite treatment with an antistaphylococcal penicillin was given only in 22% of patients. Only 14.4% of patients had a repeat blood culture after the initiation of antimicrobial treatment. Infective endocarditis was present in 8%. In-hospital mortality has reached 15.9%. Female gender, older age, higher McCabe score, previous antimicrobial use, presence of a central venous catheter, neutropenia, severe sepsis, septic shock, and MRSA SAB were positively associated with in-hospital mortality, while monomicrobial bacteremia was negatively associated. The multivariate logistic regression model identified only severe sepsis (p = 0.05, odds ratio = 12.294) and septic shock (p = 0.007, odds ratio 57.18) to be independently positively associated with in-hospital mortality. The evaluation revealed high rates of inappropriate empirical antimicrobial treatment and non-adherence to guidelines, as shown, by the lack of repeat blood cultures. These data underline the urgent need for interventions with antimicrobial stewardship, increased involvement of infectious diseases physicians, educational sessions, and creation and implementation of local guidelines for improvement of the necessary steps for timely and efficient SAB treatment. Optimization of diagnostic techniques is needed to overcome challenges such as heteroresistance that may affect treatment. Clinicians should be aware of the factors associated with mortality in patients with SAB to identify those who are at a higher risk and optimize medical management.

A Brief Review of Pharmacokinetic Assessments of Vancomycin in Special Groups of Patients with Altered Pharmacokinetic Parameters

Vancomycin is considered the drug of choice against many Gram-positive bacterial infections. Therapeutic drug monitoring (TDM) is essential to achieve an optimum clinical response and avoid vancomycin-induced adverse reactions including nephrotoxicity. Although different studies are available on vancomycin TDM, still there are controversies regarding the selection among different pharmacokinetic parameters including trough concentration, the area under the curve to minimum inhibitory concentration ratio (AUC24h/MIC), AUC of intervals, elimination constant, and vancomycin clearance. In this review, different pharmacokinetic parameters for vancomycin TDM have been discussed along with corresponding advantages and disadvantages. Also, vancomycin pharmacokinetic assessments are discussed in patients with altered pharmacokinetic parameters including those with renal and/or hepatic failure, critically ill patients, patients with burn injuries, intravenous drug users, obese and morbidly obese patients, those with cancer, patients undergoing organ transplantation, and vancomycin administration during pregnancy and lactation. An individualized dosing regimen is required to guarantee the optimum therapeutic responses and minimize adverse reactions including acute kidney injury in these special groups of patients. According to the pharmacoeconomic data on vancomycin TDM, pharmacokinetic assessments would be cost-effective in patients with altered pharmacokinetics and are associated with shorter hospitalization period, faster clinical stability status, and shorter courses of inpatient vancomycin administration.

Changing microbiological profile and antimicrobial susceptibility of the isolates obtained from patients with infective endocarditis - The time to relook into the therapeutic guidelines

The microbiological profile, associated risk factors and demographic characteristics of patients with IE has changed in the recent times. In the present study, the antibiotic susceptibility profile of 66 isolates (40 from IDU and 26 from non IDU) recovered over a period of three years from the patients with definitive diagnosis of IE along with their absolute minimum inhibitory concentrations (MIC-μg/ml) was determined as per CLSI, 2017 guidelines. Staphylococcus aureus was found to be the predominant pathogen associated with IE out of which 90.2% isolates were MRSA, although none of the isolates were found resistant to vancomycin, teicoplanin, daptomycin and linezolid. Pseudomonas aeruginosa isolates were 100% susceptible to carbapenams, however variable resistance was observed against other antimicrobials. All Enterococci were found to be 100% susceptible to linezolid and daptomycin, whereas vancomycin resistant enterococci phenotype was observed in 25% of the Enterococcal isolates. A noticeable difference in the antimicrobial susceptibility profile and their MICs were observed in the present study, as compared to published literature across the globe and within the country. However, no statistically significant difference (λ ² test, p > 0.01)in the AST pattern of isolates from IDU vs. Non IDU was observed. After reviewing the local antibiogram it seems that we need to have our own regional guidelines, which may partially replace the currently prevailing AHA/ESC guidelines.

Hospital transmission of borderline oxacillin-resistant Staphylococcus aureus evaluated by whole-genome sequencing

Introduction

Staphylococcus aureus is a major cause of hospital infections worldwide. Awareness towards methicillin-resistant S. aureus (MRSA) infections is high but attention towards borderline oxacillin-resistant S. aureus (BORSA) is limited, possibly due to an underestimated clinical relevance, presumption of low incidence and diagnostic limitations.

Gap statement

BORSA surveillance has not been routinely implemented, and thus consensus with regard to a definition and infection control measures is lacking.

Aim

Our goals were to investigate the occurrence, molecular characteristics and clinical manifestations of BORSA infections in the hospital setting.

Methodology

Following an increased incidence in 2016, BORSA cases in 2014/2016 (in our institution) were more specifically evaluated. Medical records were reviewed to investigate epidemiological links, clinical characteristics and outcomes. Resistance and virulence markers were assessed by whole genome sequencing (WGS). Conventional methods: amplified fragment length polymorphism (AFLP) ; multilocus sequence typing (MLST) and multiple locus variable-number tandem repeat analysis (MLVA) were compared with core genome MLST (cgMLST) and whole-genome single nucleotide polymorphism (wgSNP) analysis to confirm genetic clusters.

Results

From 2009 to 2013, BORSA comprised 0.1 % of all clinical S. aureus strains. In 2016, the incidence was six-fold higher in comparison to the baseline. Whole-genome SNP and cgMLST confirmed two BORSA clusters among patients with dermatological conditions. Patients with BORSA presented with skin infections, and one case developed a severe invasive infection with a fatal outcome. Infection control measures successfully prevented further transmission in both clusters. WGS findings showed that BORSA strains carried multiple resistance and virulence genes with increased pathogenic potential.

Conclusion

WGS and cgMLST effectively characterized and confirmed BORSA clusters among at-risk patients with clinical manifestations ranging from mild skin infections to life-threatening bacteraemia. Clinical awareness and active monitoring are therefore warranted for the timely implementation of infection control measures to prevent BORSA transmission in high-risk patients.

The role of chronic suppressive antibiotics therapy in superficial drive line infection relapse of left ventricular assist devices: A retrospective cohort from a tertiary care center

INTRODUCTION

Drive line infections (DLIs) are common complications of left ventricular assist devices (LVADs). Data on use of suppression antibiotic therapy are limited.

METHODS

We performed a retrospective review of 451 patients who underwent LVAD placement from January 2009 to May 2015. First superficial DLIs were included for analysis. We examined factors associated with the use of chronic suppressive antibiotics (CSAs) therapy. Cox proportional hazards models were performed to identify factors associated with DLI relapse with the same organism as the initial DLI.

RESULTS

A total of 69 patients developed a superficial DLI within a median of 195 (interquartile range [IQR] 98-348) days of LVAD insertion. The median age was 57 years, 87% were males, and 74% were White. Gram positive bacteria caused 61% of infections, with Staphylococcus aureus being the most common (35%). Forty-three (62%) patients received suppressive antibiotic therapy. Relapse DLI occurred in 29 (42%) patients. Independent risk factors for relapse infection in multivariable analysis were sepsis (aHR 5.94 [CI 1.42-24.92]), and MRSA DLI (aHR 4.19 [CI 1.37-12.79]). There was no difference in the proportion of patients with relapse among those who were treated with antibiotic suppression therapy versus not (44% vs. 38%, p = 0.64), although relapse occurred at a later time in those who received suppression (185 vs. 69 days, p < 0.01).

CONCLUSION

CSA therapy was associated with delayed time to DLI relapse but no significant difference in the proportion of patients with relapse. A prospective study is needed to examine the effect of suppression on relapse rates.

Risk Factors for Repeat Infection and Mortality After Extraction of Infected Cardiovascular Implantable Electronic Devices

OBJECTIVES

This study sought to investigate the factors associated with repeat infection following lead extraction procedures.

BACKGROUND

Although lead extraction is an essential therapy for patients with cardiovascular implantable electronic device (CIED) infection, repeat infection still occurs in some patients.

METHODS

The authors reviewed data for consecutive patients who underwent extraction of infected CIEDs from August 2003 to May 2019. Repeat infection was defined as infective endocarditis, sepsis with no alternative focus, or pocket infection after extraction of infected CIEDs.

RESULTS

Extraction of infected CIEDs was performed in 496 patients. The most commonly implicated pathogen was Staphylococcus aureus (188 patients). In 449 patients (90.5%), all leads were completely extracted using only transvenous techniques. Thirty-three patients (6.7%) underwent surgical lead extraction, and 14 (2.8%) had retained leads or lead components. After a median follow-up of 352 [40 to 1,255] days after CIED extraction, 144 patients (29.0%) died. Repeat infection occurred in 47 patients (9.5%) with the median time from the extraction to repeat infection of 103 [45 to 214] days. In multivariable analysis, presence of a left ventricular assist device, younger age at extraction, and S. aureus infection were independent predictors of repeat infection. Additionally, chronic kidney disease, congestive heart failure, presence of septic emboli, S. aureus infection, and occurrence of major complications were independent predictors of increased mortality.

CONCLUSIONS

Patients with S. aureus infection have a high risk of repeat infection and poor prognosis after CIED extraction. Repeat infection is also predicted by younger age and the presence of a left ventricular assist device, whereas mortality was predicted by congestive heart failure, chronic kidney disease, and septic emboli.

Nanotheranostics: A Possible Solution for Drug-Resistant Staphylococcus aureus and their Biofilms?

Staphylococcus aureus is a notorious pathogen that colonizes implants (orthopedic and breast implants) and wounds with a vicious resistance to antibiotic therapy. Methicillin-resistant S. aureus (MRSA) is a catastrophe mainly restricted to hospitals and emerged to community reservoirs, acquiring resistance and forming biofilms. Treating biofilms is problematic except via implant removal or wound debridement. Nanoparticles (NPs) and nanofibers could combat superbugs and biofilms and rapidly diagnose MRSA. Nanotheranostics combine diagnostics and therapeutics into a single agent. This comprehensive review is interpretative, utilizing mainly recent literature (since 2016) besides the older remarkable studies sourced via Google Scholar and PubMed. We unravel the molecular S. aureus resistance and complex biofilm. The diagnostic properties and detailed antibacterial and antibiofilm NP mechanisms are elucidated in exciting stories. We highlight the challenges of bacterial infections nanotheranostics. Finally, we discuss the literature and provide "three action appraisals". (i) The first appraisal consists of preventive actions (two wings), avoiding unnecessary hospital visits, hand hygiene, and legislations against over-the-counter antibiotics as the general preventive wing. Our second recommended preventive wing includes preventing the adverse side effects of the NPs from resistance and toxicity by establishing standard testing procedures. These standard procedures should provide breakpoints of bacteria's susceptibility to NPs and a thorough toxicological examination of every single batch of synthesized NPs. (ii) The second appraisal includes theranostic actions, using nanotheranostics to diagnose and treat MRSA, such as what we call "multifunctional theranostic nanofibers. (iii) The third action appraisal consists of collaborative actions.

Dysfunctional accessory gene regulator (agr) as a prognostic factor in invasive Staphylococcus aureus infection: a systematic review and meta-analysis

The accessory gene regulator (agr) locus of Staphylococcus aureus is a quorum-sensing virulence regulator. Although there are many studies concerning the effect of dysfunctional agr on the outcomes of S. aureus infection, there is no systematic review to date. We systematically searched for clinical studies reporting outcomes of invasive S. aureus infections and the proportion of dysfunctional agr among their causative strains, and we performed a meta-analysis to obtain estimates of the odds of outcomes of invasive S. aureus infection with dysfunctional versus functional agr. Of 289 articles identified by our research strategy, 20 studies were meta-analysed for crude analysis of the impact of dysfunctional agr on outcomes of invasive S. aureus infection. Dysfunctional agr was generally associated with unfavourable outcomes (OR 1.32, 95% CI 1.05–1.66), and the impact of dysfunctional agr on outcome was more prominent in invasive methicillin-resistant S. aureus (MRSA) infections (OR 1.54, CI 1.20–1.97). Nine studies were meta-analysed for the impact of dysfunctional agr on the 30-day mortality of invasive S. aureus infection. Invasive MRSA infection with dysfunctional agr exhibited higher 30-day mortality (OR 1.40, CI 1.03–1.90) than that with functional agr. On the other hand, invasive MSSA infection with dysfunctional agr exhibited lower 30-day mortality (OR 0.51, CI 0.27–0.95). In the post hoc subgroup analysis by the site of MRSA infection, dysfunctional agr was associated with higher 30-day mortality in MRSA pneumonia (OR 2.48, CI 1.17–5.25). The effect of dysfunctional agr on the outcome of invasive S. aureus infection may vary depending on various conditions, such as oxacillin susceptibility and the site of infection. Dysfunctional agr was generally associated with unfavourable clinical outcomes and its effect was prominent in MRSA and pneumonia. Dysfunctional agr may be applicable for outcome prediction in cases of invasive MRSA infection with hardly eradicable foci such as pneumonia.

Systematic review and meta-analysis of the efficacy and safety of vancomycin combined with β-lactam antibiotics in the treatment of methicillin-resistant Staphylococcus aureus bloodstream infections

OBJECTIVE

Vancomycin combined with β-lactams (Combo therapy) has been encouraged in the treatment of methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infections (BSIs) in recent years, but its efficacy and safety have not been systematically evaluated. This is a systematic review and meta-analysis to clarify the efficacy and safety of Combo therapy in patients with MRSA BSIs.

METHODS

Relevant articles reporting on the clinical or microbiology outcomes of Combo treatment in adult patients with MRSA bacteraemia throughout November 2019 were searched in PubMed, EMBASE and Cochrane Library databases. Summary odds ratios (ORs) or mean differences (MDs) and 95% confidence intervals (CIs) were evaluated using a fixed- or random-effects model.

RESULTS

Six articles (806 patients) consisting of one RCT and five retrospective cohort studies were included in this study. The pooled data showed that Combo therapy could significantly reduce the risk of microbiological failure (OR = 0.54, 95% CI 0.35-0.83, I² 40%, P = 0.005) and persistent bacteraemia (OR=0.48, 95% CI 0.30-0.77, I² 13%, P = 0.002), as well as shorten the duration of bacteraemia (MD = -1.06, 95% CI -1.53 to -0.60, I² 0%, P < 0.00001). In addition, it did not significantly increase the incidence of nephrotoxicity (OR = 1.17, 95% CI 0.64-2.13, I² 0%, P = 0.61). However, no significant difference was detected between the groups regarding 28/30-day mortality, MRSA-related mortality, bacteraemia relapse or length of hospitalization.

CONCLUSIONS

These results demonstrate that Combo therapy clears the pathogenic bacteria of MRSA bacteraemia but does not improve the clinical prognosis. As the sample size was small and most of the studies were retrospective cohort studies with substantial heterogeneity, there is a need for further studies encompassing large-scale multicentre RCTs to validate our results.

A review of current treatment strategies for infective endocarditis

INTRODUCTION

Infective endocarditis is one of the most difficult-to-treat infectious diseases.

AREAS COVERED

We restricted this review to the anti-infective treatment of the main bacteria responsible for infective endocarditis, i.e. staphylococci, streptococci, enterococci, and Gram-negative bacilli, including HACEK. Specific topics of major interest in treatment strategy are covered as well, including empirical treatment, oral switch, and treatment duration. We searched in the MEDLINE database to identify relevant studies, trials, reviews, or meta-analyses until May 2020.

EXPERT OPINION

The use of aminoglycosides for the treatment of endocarditis has been dramatically reduced over the last 20 years. It should be administered once daily, and no longer than 2 weeks. For staphylococcal endocarditis, recent data reinforced the role of anti-staphylococcal penicillins, for methicillin-susceptible isolates (alternative, cefazolin), and vancomycin for methicillin-resistant isolates (alternative, daptomycin). For staphylococcal prosthetic-valve endocarditis, these treatments will be reinforced by the addition of gentamicin during the first 2 weeks, and rifampin throughout the whole treatment duration, i.e. 6 weeks. The optimal duration of antibacterial treatment is 4 weeks for most native valve endocarditis, and 6 weeks for prosthetic-valve endocarditis. The oral switch is safe in patients stabilized after the initial intravenous course.

Molecular docking and inhibition profiles of some antibiotics on lactoperoxidase enzyme purified from bovine milk

Antibiotics are generally used for human and veterinary applications to preserve and to control microbial diseases. Milk has a biologically significant enzyme known as lactoperoxidase (LPO) that is a member of peroxidase family. In metabolism, LPO has ability to catalyze the transformation of thiocyanate (SCN^-) to hypothiocyanite (OSCN^-) that is an antibacterial agent and the reaction occurs with hydrogen peroxide. In this work, LPO inhibition effects of some antibiotics including cefazolin, oxytetracycline, flunixin meglumine, cefuroxime, tylosin, vancomycin, chloramphenicol and lincomycin were tested. Among the antibiotics cefazolin was indicated the strongest inhibitory efficacy. The half maximal inhibitory concentration (IC₅₀) and the inhibition constant (K_i) values of cefazolin were found as 8.19 and 34.66 µM, respectively. It was shown competitive inhibition. 5-Methyl-1,3,4-thiadiazol-2-yl moiety activity plays a key role in the inhibition mechanism of cefazolin.Communicated by Ramaswamy H. Sarma.

A chemoselective strategy for late-stage functionalization of complex small molecules with polypeptides and proteins

Conjugates between proteins and small molecules enable access to a vast chemical space that is not achievable with either type of molecule alone; however, the paucity of specific reactions capable of functionalizing proteins and natural products presents a formidable challenge for preparing conjugates. Here we report a strategy for conjugating electron-rich (hetero)arenes to polypeptides and proteins. Our bioconjugation technique exploits the electrophilic reactivity of an oxidized selenocysteine residue in polypeptides and proteins, and the electron-rich character of certain small molecules to provide bioconjugates in excellent yields under mild conditions. This conjugation chemistry enabled the synthesis of peptide-vancomycin conjugates without the prefunctionalization of vancomycin. These conjugates have an enhanced in vitro potency for resistant Gram-positive and Gram-negative pathogens. Additionally, we show that a 6 kDa affibody protein and a 150 kDa immunoglobulin-G antibody could be modified without diminishing bioactivity.

Antibiotic-mediated bacteriome depletion in ApcMin/+ mice is associated with reduction in mucus-producing goblet cells and increased colorectal cancer progression

Recent epidemiological evidence suggests that exposure to antibiotics in early‐to‐middle adulthood is associated with an increased risk of colorectal adenoma. However, mechanistic studies in established preclinical cancer to examine these claims are extremely limited. Therefore, we investigated the effect of long‐term exposure of an antibiotic cocktail composed of Vancomycin, Neomycin, and Streptomycin, on tumor development and progression in the Apc^Min/+ mouse, an established genetic model for familial adenomatous polyposis. Clinical pathologies related to tumor development as well as intestinal and colon tissue histopathology were studied at ages 8, 12, and 16 weeks of age, which correspond to the approximate ages of development of neoplasia, gut inflammation with polyposis, and cancer progression, respectively, in this animal model. We show that the antibiotics significantly increase the severity of clinical symptoms, including effects on intestinal histology and goblet cell numbers. In addition, they promote small intestinal polyposis. Finally, metagenomic analysis of fecal samples demonstrated that antibiotic exposure is associated with a significant but nonuniform depletion of the animal's natural gut flora. Overall, these findings support the premise that long‐term antibiotic exposure mediates the selected depletion of gut microbial communities and the concomitant thinning of the protective mucus layer, resulting in an increase in tumor development.

Stability of Concentrated Solution of Vancomycin Hydrochloride in Syringes for Intensive Care Units

Background

Vancomycin is increasingly administrated by continuous infusion. But the treatment of patient in intensive care need restricted volume to prevent fluid overload. The aim of the study was to evaluate the physical and chemical stability of solutions of a high concentration of vancomycin hydrochloride in 5 % glucose or 0.9 % NaCl.

Methods

Eight syringes of 50 mL, containing 41.66 mg/mL of vancomycin hydrochloride four syringes in 5 % glucose and four in 0.9 % NaCl were prepared and stored at ambient temperature during 48 h. Immediately after preparation and during 48 h, vancomycin hydrochloride concentrations were measured by a high-performance liquid chromatography (HPLC). Spectrophotometric absorbance at different wavelengths, pH measurement and microscopic observations were also performed.

Results

All solutions were physico-chemically stable during the whole period storage at ambient temperature: no color change, turbidity, precipitation or opacity, no significant pH variations or optic densities were observed in the solutions. Any crystals were seen by microscopic analysis. Solutions are considered chemically stable as the lower limit of the 95 % unilateral confidence interval on the mean remained above 90 % of the initial concentration for at least 48 h.

Conclusions

Solutions of vancomycin hydrochloride 41.66 mg/mL in syringe of 5 % glucose or 0.9 % NaCl are physically and chemically stable for at least 48 h when stored in syringes at ambient temperature.

Influence of Reported Penicillin Allergy on Mortality in MSSA Bacteremia

Background

Penicillin allergy frequently impacts antibiotic choice. As beta-lactams are superior to vancomycin in treating methicillin-susceptible Staphylococcus aureus (MSSA) bacteremia, we examined the effect of reported penicillin allergy on clinical outcomes in patients with MSSA bacteremia.

Methods

In this retrospective cohort study of adults with MSSA bacteremia admitted to a large tertiary care hospital, outcomes were examined according to reported penicillin allergy. Primary outcomes included 30-day and 90-day mortality rates. Multivariable regression models were developed to quantify the effect of reported penicillin allergy on mortality while adjusting for potential confounders.

Results

From 2010 to 2015, 318 patients with MSSA bacteremia were identified. Reported penicillin allergy had no significant effect on adjusted 30-day mortality (odds ratio [OR], 0.73; 95% confidence interval [CI], 0.29-1.84; P = .51). Patients with reported penicillin allergy were more likely to receive vancomycin (38% vs 11%, P < .01), but a large number received cefazolin regardless of reported allergy (29 of 66, 44%). Mortality rates were highest among nonallergic patients receiving vancomycin (22.6% vs 7.4% for those receiving beta-lactams regardless of reported allergy, P < .01). In multivariable analysis, beta-lactam receipt was most strongly associated with survival (OR, 0.26; 95% CI, 0.12-0.54).

Conclusions

Reported penicillin allergy had no significant effect on 30- or 90-day mortality. Non-penicillin-allergic patients receiving vancomycin for treatment of MSSA bacteremia had the highest mortality rates overall. Receipt of a beta-lactam was the strongest predictor of survival. These results underscore the importance of correct classification of patients with penicillin allergy and appropriate treatment with a beta-lactam when tolerated.

AUC/MIC Pharmacodynamic Target Is Not a Good Predictor of Vancomycin Efficacy in Methicillin-Resistant Staphylococcus aureus Experimental Endocarditis

The aim of this in vivo study was to compare the efficacy of vancomycin at standard doses (VAN-SD) to that of VAN at adjusted doses (VAN-AD) in achieving a VAN area under the curve/MIC ratio (AUC/MIC) of ≥400 against three methicillin-resistant Staphylococcus aureus (MRSA) strains with different microdilution VAN MICs in an experimental endocarditis model. The valve vegetation bacterial counts after 48 h of VAN therapy were compared, and no differences were observed between the two treatment groups for any of the three strains tested. Overall, for VAN-SD and VAN-AD, the rates of sterile vegetations were 15/45 (33.3%) and 21/49 (42.8%) (P = 0.343), while the medians (interquartile ranges [IQRs]) for log10 CFU/g of vegetation were 2 (0 to 6.9) and 2 (0 to 4.5) (P = 0.384), respectively. In conclusion, this VAN AUC/MIC pharmacodynamic target was not a good predictor of vancomycin efficacy in MRSA experimental endocarditis.

Comparison of the clinical features and outcomes of infective endocarditis between hemodialysis and non-hemodialysis patients

Hemodialysis (HD) patients are more susceptible to infective endocarditis (IE) due to the increased risk of bacterial invasion through intravascular access. However, it remains unclear whether the causative organisms and outcomes of IE in HD patients differ from those in non-HD patients. This study clarified the differences in clinical presentation and outcomes between HD and non-HD patients. At our hospital, we performed a retrospective study of 39 HD and 51 non-HD patients with echocardiography-confirmed IE between June 2000 and February 2007. No differences in sex, intravenous drug use, previous diagnosis of congestive heart failure, and previous valvular surgery were observed between these two groups. The number of patients with diabetic mellitus in these two groups was significantly different (28.2% HD vs 5.9% non-HD patients). The C-reactive protein levels in the two groups were not significantly different. By contrast, the erythrocyte sedimentation rate was significantly higher in the HD patients (HD vs non-HD: 87.2±33.32 vs 52.96±28.19). The incidence of IE involving the mitral valve (MV; 45.1%) or the aortic valve (AV; 43.1%) was similar among the non-HD patients, whereas a preference of IE involving the MV (79.5%) over the AV (15.4%) was noted among the HD patients. The HD patients had a significantly higher Staphylococcus aureus infection rate (HD: 46.2%; non-HD: 27.5%). The proportion of methicillin-resistant S. aureus (MRSA; 83.8%) infection accounting for S. aureus IE in the HD group was higher than that (28.6%) in the non-HD group. The in-hospital mortality rate did not differ between the two groups. In conclusion, compared with non-HD patients, a propensity of IE involving the MV and a higher MRSA infection rate were observed in HD patients. The in-hospital mortality rate of echocardiography-confirmed IE did not differ between the two groups.

A Putative Bacterial ABC Transporter Circumvents the Essentiality of Signal Peptidase

The type I signal peptidase of Staphylococcus aureus, SpsB, is an attractive antibacterial target because it is essential for viability and extracellularly accessible. We synthesized compound 103, a novel arylomycin-derived inhibitor of SpsB with significant potency against various clinical S. aureus strains (MIC of ~1 µg/ml). The predominant clinical strain USA300 developed spontaneous resistance to compound 103 with high frequency, resulting from single point mutations inside or immediately upstream of cro/cI, a homolog of the lambda phage transcriptional repressor cro. These cro/cI mutations led to marked (>50-fold) overexpression of three genes encoding a putative ABC transporter. Overexpression of this ABC transporter was both necessary and sufficient for resistance and, notably, circumvented the essentiality of SpsB during in vitro culture. Mutation of its predicted ATPase gene abolished resistance, suggesting a possible role for active transport; in these bacteria, resistance to compound 103 occurred with low frequency and through mutations in spsB. Bacteria overexpressing the ABC transporter and lacking SpsB were capable of secreting a subset of proteins that are normally cleaved by SpsB and instead were cleaved at a site distinct from the canonical signal peptide. These bacteria secreted reduced levels of virulence-associated proteins and were unable to establish infection in mice. This study reveals the mechanism of resistance to a novel arylomycin derivative and demonstrates that the nominal essentiality of the S. aureus signal peptidase can be circumvented by the upregulation of a putative ABC transporter in vitro but not in vivo.

The type I signal peptidase of Staphylococcus aureus (SpsB) enables the secretion of numerous proteins by cleavage of the signal peptide. We synthesized an SpsB inhibitor with potent activity against various clinical S. aureus strains. The predominant S. aureus strain USA300 develops resistance to this inhibitor by mutations in a novel transcriptional repressor (cro/cI), causing overexpression of a putative ABC transporter. This mechanism promotes the cleavage and secretion of various proteins independently of SpsB and compensates for the requirement of SpsB for viability in vitro. However, bacteria overexpressing the ABC transporter and lacking SpsB secrete reduced levels of virulence-associated proteins and are unable to infect mice. This study describes a bacterial resistance mechanism that provides novel insights into the biology of bacterial secretion.

Costs and Outcomes Among Hemodialysis-Dependent Patients With Methicillin-Resistant or Methicillin-SusceptibleStaphylococcus aureusBacteremia

Objective:

Comorbid conditions have complicated previous analyses of the consequences of methicillin resistance for costs and outcomes ofStaphylococcus aureusbacteremia. We compared costs and outcomes of methicillin resistance in patients withS. aureusbacteremia and a single chronic condition.

Design, Setting, and Patients:

We conducted a prospective cohort study of hemodialysis-dependent patients with end-stage renal disease andS. aureusbacteremia hospitalized between July 1996 and August 2001. We used propensity scores to reduce bias when comparing patients with methicillin-resistant (MRSA) and methicillin-susceptible (MSSA)S. aureusbacteremia. Outcome measures were resource use, direct medical costs, and clinical outcomes at 12 weeks after initial hospitalization.

Results:

Fifty-four patients (37.8%) had MRSA and 89 patients (62.2%) had MSSA. Compared with patients with MSSA bacteremia, patients with MRSA bacteremia were more likely to have acquired the infection while hospitalized for another condition (27.8% vs 12.4%;P= .02). To attribute all inpatient costs toS. aureusbacteremia, we limited the analysis to 105 patients admitted for suspectedS. aureusbacteremia from a community setting. Adjusted costs were higher for MRSA bacteremia for the initial hospitalization ($21,251 vs $13,978;P= .012) and after 12 weeks ($25,518 vs $17,354;P= .015). At 12 weeks, patients with MRSA bacteremia were more likely to die (adjusted odds ratio, 5.4; 95% confidence interval, 1.5 to 18.7) than were patients with MSSA bacteremia.

Conclusions:

Community-dwelling, hemodialysis-dependent patients hospitalized with MRSA bacteremia face a higher mortality risk, longer hospital stays, and higher inpatient costs than do patients with MSSA bacteremia.

Treatment of Infection and Colonization Caused by Methicillin-Resistant Staphylococcus aureus

The mechanism of methicillin resistance confers resistance to all available B-lactam antibiotics; consequently, B-lactam antibiotics have no role in therapy of methicillin-resistant Staphylococcus aureus (MRSA) infections. Vancomycin remains the drug of choice. Teicoplanin and daptomycin are two investigational antibiotics related to vancomycin in structure and in spectrum of activity. In clinical trials employing relatively low doses, neither was as effective as vancomycin. Trials at higher doses are on-going. Quinolones, ciprofloxacin in particular, have been used successfully to treat infections caused by MRSA; however, the usefulness of quinolones may be limited by the tendency of resistance to emerge during therapy. Quinolones probably should be used only in combination with another active agent, such as rifampin, when treating serious infections caused by MRSA. Other agents may be active in vitro against MRSA, but clinical data showing their effectiveness are lacking. Rifampin combination regimens appear most effectively to eradicate colonization with MRSA.

CAMERA2 - combination antibiotic therapy for methicillin-resistant Staphylococcus aureus infection: study protocol for a randomised controlled trial

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) bacteraemia is a serious infection resulting in 20-50 % 90-day mortality. The limitations of vancomycin, the current standard therapy for MRSA, make treatment difficult. The only other approved drug for treatment of MRSA bacteraemia, daptomycin, has not been shown to be superior to vancomycin. Surprisingly, there has been consistent in-vitro and in-vivo laboratory data demonstrating synergy between vancomycin or daptomycin and an anti-staphylococcal β-lactam antibiotic. There is also growing clinical data to support such combinations, including a recent pilot randomised controlled trial (RCT) that demonstrated a trend towards a reduction in the duration of bacteraemia in patients treated with vancomycin plus flucloxacillin compared to vancomycin alone. Our aim is to determine whether the addition of an anti-staphylococcal penicillin to standard therapy results in improved clinical outcomes in MRSA bacteraemia.

METHODS/DESIGN

We will perform an open-label, parallel-group, randomised (1:1) controlled trial at 29 sites in Australia, New Zealand, Singapore, and Israel. Adults (aged 18 years or older) with MRSA grown from at least one blood culture and able to be randomised within 72 hours of the index blood culture collection will be eligible for inclusion. Participants will be randomised to vancomycin or daptomycin (standard therapy) given intravenously or to standard therapy plus 7 days of an anti-staphylococcal β-lactam (flucloxacillin, cloxacillin, or cefazolin). The primary endpoint will be a composite outcome at 90 days of (1) all-cause mortality, (2) persistent bacteraemia at day 5 or beyond, (3) microbiological relapse, or (4) microbiological treatment failure. The recruitment target of 440 patients is based on an expected failure rate for the primary outcome of 30 % in the control arm and the ability to detect a clinically meaningful absolute decrease of 12.5 %, with a two-sided alpha of 0.05, a power of 80 %, and assuming 10 % of patients will not be evaluable for the primary endpoint.

DISCUSSION

Key potential advantages of adding anti-staphylococcal β-lactams to standard therapy for MRSA bacteraemia include their safety profile, low cost, and wide availability.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02365493 . Registered 24 February 2015.

Performance of processes of care and outcomes in patients with Staphylococcus aureus bacteremia

BACKGROUND

Staphylococcus aureus bacteremia (SAB) is associated with significant morbidity and mortality in hospitalized adults.

OBJECTIVE

We aimed to identify current practice patterns in the management of SAB, and to evaluate their association with clinical outcomes.

DESIGN

Retrospective cohort study.

SETTING

A 1558-bed tertiary care teaching hospital.

PATIENTS

Adult patients hospitalized between January 1, 2012 through April 30, 2013, who had at least 1 positive blood culture with S aureus.

INTERVENTION

None

MEASUREMENTS

Electronic medical records were reviewed and the processes of care in the management of SAB were identified. The main outcome was clinical failure, defined as a composite endpoint of in-hospital mortality and persistent bacteremia.

RESULTS

Two hundred fifty episodes of SAB occurred in 241 patients, and 78 (32.4%) had clinical failure. Processes of care that impacted the risk of clinical failure included: timing of follow-up blood cultures (delays of >4 days had a relative risk [RR] of 6.6; 95% confidence interval [CI]: 2.1-20.5; P = 0.001), consultation with infectious diseases specialist within 6 days from diagnosis of SAB (RR: 0.3; 95% CI: 0.1-0.9; P = 0.03), and use of β-lactams in patients with methicillin-susceptible S aureus bacteremia (RR: 0.1; 95% CI: 0.04-0.5; P = 0.002).

CONCLUSIONS

The processes of care identified in our study could serve as quality and patient safety indicators for the management of SAB.

Fosfomycin plus β-Lactams as Synergistic Bactericidal Combinations for Experimental Endocarditis Due to Methicillin-Resistant and Glycopeptide-Intermediate Staphylococcus aureus

The urgent need of effective therapies for methicillin-resistant Staphylococcus aureus (MRSA) infective endocarditis (IE) is a cause of concern. We aimed to ascertain the in vitro and in vivo activity of the older antibiotic fosfomycin combined with different beta-lactams against MRSA and glycopeptide-intermediate-resistant S. aureus (GISA) strains. Time-kill tests with 10 isolates showed that fosfomycin plus imipenem (FOF+IPM) was the most active evaluated combination. In an aortic valve IE model with two strains (MRSA-277H and GISA-ATCC 700788), the following intravenous regimens were compared: fosfomycin (2 g every 8 h [q8h]) plus imipenem (1 g q6h) or ceftriaxone (2 g q12h) (FOF+CRO) and vancomycin at a standard dose (VAN-SD) (1 g q12h) and a high dose (VAN-HD) (1 g q6h). Whereas a significant reduction of MRSA-227H load in the vegetations (veg) was observed with FOF+IPM compared with VAN-SD (0 [interquartile range [IQR], 0 to 1] versus 2 [IQR, 0 to 5.1] log CFU/g veg; P = 0.01), no statistical differences were found with VAN-HD. In addition, FOF+IPM sterilized more vegetations than VAN-SD (11/15 [73%] versus 5/16 [31%]; P = 0.02). The GISA-ATCC 700788 load in the vegetations was significantly lower after FOF+IPM or FOF+CRO treatment than with VAN-SD (2 [IQR, 0 to 2] and 0 [IQR, 0 to 2] versus 6.5 [IQR, 2 to 6.9] log CFU/g veg; P < 0.01). The number of sterilized vegetations after treatment with FOF+CRO was higher than after treatment with VAN-SD or VAN-HD (8/15 [53%] versus 4/20 [20%] or 4/20 [20%]; P = 0.03). To assess the effect of FOF+IPM on penicillin binding protein (PBP) synthesis, molecular studies were performed, with results showing that FOF+IPM treatment significantly decreased PBP1, PBP2 (but not PBP2a), and PBP3 synthesis. These results allow clinicians to consider the use of FOF+IPM or FOF+CRO to treat MRSA or GISA IE.

Discovery of an ultra-short linear antibacterial tetrapeptide with anti-MRSA activity from a structure-activity relationship study

The overuse and misuse of antibiotics has resulted in the emergence of drug-resistant pathogenic bacteria, including meticillin-resistant Staphylococcus aureus (MRSA), the primary pathogen responsible for human skin and soft-tissue infections. Antibacterial peptides are known to kill bacteria by rapidly disrupting their membranes and are deemed plausible alternatives to conventional antibiotics. One advantage of their membrane-targeting mode of action is that bacteria are unlikely to develop resistance as changing their cell membrane structure and morphology would likely involve extensive genetic mutations. However, major concerns in using peptides as antibacterial drugs include their instability towards plasma proteases, toxicity towards human cells due to their membrane-targeting mode of action and high manufacturing cost. These concerns can be mitigated by developing peptides as topical agents, by the judicial selection of amino acids and developing very short peptides respectively. In this preliminary report, we reveal a linear, non-hemolytic tetrapeptide with rapid bactericidal activity against MRSA developed from a structure-activity relationship study based on the antimicrobial hexapeptide WRWRWR-NH2. Our finding opens promising avenues for the development of ultra-short antibacterials to treat multidrug-resistant MRSA skin and soft tissue infections.

Staphylococcus aureus infections: epidemiology, pathophysiology, clinical manifestations, and management

Staphylococcus aureus is a major human pathogen that causes a wide range of clinical infections. It is a leading cause of bacteremia and infective endocarditis as well as osteoarticular, skin and soft tissue, pleuropulmonary, and device-related infections. This review comprehensively covers the epidemiology, pathophysiology, clinical manifestations, and management of each of these clinical entities. The past 2 decades have witnessed two clear shifts in the epidemiology of S. aureus infections: first, a growing number of health care-associated infections, particularly seen in infective endocarditis and prosthetic device infections, and second, an epidemic of community-associated skin and soft tissue infections driven by strains with certain virulence factors and resistance to β-lactam antibiotics. In reviewing the literature to support management strategies for these clinical manifestations, we also highlight the paucity of high-quality evidence for many key clinical questions.

A mutation of RNA polymerase β' subunit (RpoC) converts heterogeneously vancomycin-intermediate Staphylococcus aureus (hVISA) into "slow VISA"

Various mutations in the rpoB gene, which encodes the RNA polymerase β subunit, are associated with increased vancomycin (VAN) resistance in vancomycin-intermediate Staphylococcus aureus (VISA) and heterogeneously VISA (hVISA) strains. We reported that rpoB mutations are also linked to the expression of the recently found "slow VISA" (sVISA) phenotype (M. Saito, Y. Katayama, T. Hishinuma, A. Iwamoto, Y. Aiba, K Kuwahara-Arai, L. Cui, M. Matsuo, N. Aritaka, and K. Hiramatsu, Antimicrob Agents Chemother 58:5024-5035, 2014, http://dx.doi.org/10.1128/AAC.02470-13). Because RpoC and RpoB are components of RNA polymerase, we examined the effect of the rpoC(P440L) mutation on the expression of the sVISA phenotype in the Mu3fdh2*V6-5 strain (V6-5), which was derived from a previously reported hVISA strain with the VISA phenotype. V6-5 had an extremely prolonged doubling time (DT) (72 min) and high vancomycin MIC (16 mg/liter). However, the phenotype of V6-5 was unstable, and the strain frequently reverted to hVISA with concomitant loss of low growth rate, cell wall thickness, and reduced autolysis. Whole-genome sequencing of phenotypic revertant strain V6-5-L1 and comparison with V6-5 revealed a second mutation, F562L, in rpoC. Introduction of the wild-type (WT) rpoC gene using a multicopy plasmid resolved the sVISA phenotype of V6-5, indicating that the rpoC(P440L) mutant expressed the sVISA phenotype in hVISA. To investigate the mechanisms of resistance in the sVISA strain, we independently isolated an additional 10 revertants to hVISA and VISA. In subsequent whole-genome analysis, we identified compensatory mutations in the genes of three distinct functional categories: the rpoC gene itself as regulatory mutations, peptidoglycan biosynthesis genes, and relQ, which is involved in the stringent response. It appears that the rpoC(P440L) mutation causes the sVISA phenotype by augmenting cell wall peptidoglycan synthesis and through the control of the stringent response.

Diagnosis and treatment of bacteremia and endocarditis due to Staphylococcus aureus. A clinical guideline from the Spanish Society of Clinical Microbiology and Infectious Diseases (SEIMC)

Both bacteremia and infective endocarditis caused by Staphylococcus aureus are common and severe diseases. The prognosis may darken not infrequently, especially in the presence of intracardiac devices or methicillin-resistance. Indeed, the optimization of the antimicrobial therapy is a key step in the outcome of these infections. The high rates of treatment failure and the increasing interest in the influence of vancomycin susceptibility in the outcome of infections caused by both methicillin-susceptible and -resistant isolates has led to the research of novel therapeutic schemes. Specifically, the interest raised in recent years on the new antimicrobials with activity against methicillin-resistant staphylococci has been also extended to infections caused by susceptible strains, which still carry the most important burden of infection. Recent clinical and experimental research has focused in the activity of new combinations of antimicrobials, their indication and role still being debatable. Also, the impact of an appropriate empirical antimicrobial treatment has acquired relevance in recent years. Finally, it is noteworthy the impact of the implementation of a systematic bundle of measures for improving the outcome. The aim of this clinical guideline is to provide an ensemble of recommendations in order to improve the treatment and prognosis of bacteremia and infective endocarditis caused by S. aureus, in accordance to the latest evidence published.

Prophylactic antibiotic administration for post cardiothoracic surgery sternal wounds: a retrospective study

BACKGROUND

Cardiothoracic surgery sternal infections are difficult to treat situations. Until now there are no clear guidelines which or if an antibiotic could be used as prophylactic treatment.

PATIENTS AND METHODS

We collected retrospectively data from 535 patients from our hospital which underwent cardiothoracic surgery and recorded several biological parameters and technical aspects of the surgery.

RESULTS

It was observed that patients to whom vancomycin was administered had less post surgery infection than those to whom begalin was administered. Male who were treated with vancomycin it was observed that they had 1.67 chances to be treated properly than female. Patients which were hospitalized for more than 7 days before surgery had 62.6% higher chances for post surgery infection.

CONCLUSIONS

It was observed that vancomycin can be used as a prophylactic treatment for cardiothoracic surgeries acting efficiently against sternal wounds.

Association between vancomycin day 1 exposure profile and outcomes among patients with methicillin-resistant Staphylococcus aureus infective endocarditis

Given the critical importance of early appropriate therapy, a retrospective cohort (2002 to 2013) was performed at the Detroit Medical Center to evaluate the association between the day 1 vancomycin exposure profile and outcomes among patients with MRSA infective endocarditis (IE). The day 1 vancomycin area under the concentration-time curve (AUC0-24) and the minimum concentration at 24 h (Cmin 24) was estimated for each patient using the Bayesian procedure in ADAPT 5, an approach shown to accurately predict the vancomycin exposure with low bias and high precision with limited pharmacokinetic sampling. Initial MRSA isolates were collected and vancomycin MIC was determined by broth microdilution (BMD) and Etest. The primary outcome was failure, defined as persistent bacteremia (≥7 days) or 30-day attributable mortality. Classification and regression tree analysis (CART) was used to determine the vancomycin exposure variables associated with an increased probability of failure. In total, 139 patients met study criteria; 76.3% had right-sided IE, 16.5% had left-sided IE, and 7.2% had both left and right-sided IE. A total of 89/139 (64%) experienced failure by composite definition. In the CART analysis, failure was more pronounced in patients with an AUC0-24/MIC as determined by BMD of ≤600 relative to those with AUC0-24/MIC as determined by BMD of >600 (69.8% versus 54.7%, respectively, P = 0.073). In the logistic regression analysis, an AUC/MIC as determined by BMD of ≤600 (adjusted odds ratio, 2.3; 95% confidence interval, 1.01 to 5.37; P = 0.047) was independently associated with failure. Given the retrospective nature of the present study, further prospective studies are required but these data suggest that patients with an AUC0-24/MIC as determined by BMD of ≤600 present an increased risk of failure.

Monte Carlo simulation analysis of ceftobiprole, dalbavancin, daptomycin, tigecycline, linezolid and vancomycin pharmacodynamics against intensive care unit-isolated methicillin-resistant Staphylococcus aureus

The aim of the present study was to compare the potential of ceftobiprole, dalbavancin, daptomycin, tigecycline, linezolid and vancomycin to achieve their requisite pharmacokinetic/pharmacodynamic (PK/PD) targets against methicillin-resistant Staphylococcus aureus isolates collected from intensive care unit (ICU) settings. Monte Carlo simulations were carried out to simulate the PK/PD indices of the investigated antimicrobials. The probability of target attainment (PTA) was estimated at minimum inhibitory concentration values ranging from 0.03 to 32 μg/mL to define the PK/PD susceptibility breakpoints. The cumulative fraction of response (CFR) was computed using minimum inhibitory concentration data from the Canadian National Intensive Care Unit study. Analysis of the simulation results suggested the breakpoints of 4 μg/mL for ceftobiprole (500 mg/2 h t.i.d.), 0.25 μg/mL for dalbavancin (1000 mg), 0.12 μg/mL for daptomycin (4 mg/kg q.d. and 6 mg/kg q.d.) and tigecycline (50 mg b.i.d.), and 2 μg/mL for linezolid (600 mg b.i.d.) and vancomycin (1 g b.i.d. and 1.5 g b.i.d.). The estimated CFR were 100, 100, 70.6, 88.8, 96.5, 82.4, 89.4, and 98.3% for ceftobiprole, dalbavancin, daptomycin (4 mg/kg/day), daptomycin (6 mg/kg/day), linezolid, tigecycline, vancomycin (1 g b.i.d.) and vancomycin (1.5 g b.i.d.), respectively. In conclusion, ceftobiprole and dalbavancin have the highest probability of achieving their requisite PK/PD targets against methicillin-resistant Staphylococcus aureus isolated from ICU settings. The susceptibility predictions suggested a reduction of the vancomycin breakpoint to 1 μg/mL.

Impact of Methicillin-Resistant Staphylococcus aureus Prevalence among S. aureus Isolates on Surgical Site Infection Risk after Coronary Artery Bypass Surgery

Objective.

Cephalosporins are recommended for antibiotic prophylaxis to prevent cardiothoracic surgical site infections (SSIs) except in patients withβ-lactam allergy or in settings with a “high” prevalence of methicillin-resistantStaphylococcus aureus(MRSA) among S.aureusisolates (hereafter, “MRSA prevalence”); however, “high” remains undefined. We sought to identify the MRSA prevalence at which glycopeptide prophylaxis would minimize SSIs relative toβ-lactam prophylaxis.

Methods.

We developed a decision analysis model to estimate SSI likelihood when either glycopeptides orβ-lactams were used for prophylaxis in cardiothoracic surgery. Event probabilities were derived from a systematic literature review. A similar cost-minimization model was also developed.

Results.

At 0% MRSA prevalence, SSI probability was 3.64% with glycopeptide prophylaxis and 3.49% withβ-lactam prophylaxis. At MRSA prevalences of 10%, 20%, 30%, or 40%, SSI probabilities with glycopeptide prophylaxis did not change, but they were 3.98%, 4.48%, 4.97%, and 5.47% withβ-lactam prophylaxis. The threshold of MRSA prevalence at which glycopeptide prophylaxis minimized SSI probability and cost was 3%. In sensitivity analyses, variations in most model estimates only modestly affected the threshold.

Conclusion.

Glycopeptide prophylaxis minimizes the risk of SSIs and cost when MRSA prevalence exceeds 3%. At very low MRSA prevalence (between 3% and 10%), the SSI minimization provided by glycopeptide prophylaxis is small and may be within the error of the model. Given the current MRSA prevalence in most community and healthcare settings, clinicians should consider routine prophylaxis with vancomycin. Our findings may have important policy implications, as benefits in cardiothoracic surgery antibiotic prophylaxis must be weighed against the limitations of increased glycopeptide use.

Efficacy and safety of fosfomycin plus imipenem as rescue therapy for complicated bacteremia and endocarditis due to methicillin-resistant Staphylococcus aureus: a multicenter clinical trial

BACKGROUND

There is an urgent need for alternative rescue therapies in invasive infections caused by methicillin-resistant Staphylococcus aureus (MRSA). We assessed the clinical efficacy and safety of the combination of fosfomycin and imipenem as rescue therapy for MRSA infective endocarditis and complicated bacteremia.

METHODS

The trial was conducted between 2001 and 2010 in 3 Spanish hospitals. Adult patients with complicated MRSA bacteremia or endocarditis requiring rescue therapy were eligible for the study. Treatment with fosfomycin (2 g/6 hours IV) plus imipenem (1 g/6 hours IV) was started and monitored. The primary efficacy endpoints were percentage of sterile blood cultures at 72 hours and clinical success rate assessed at the test-of-cure visit (45 days after the end of therapy).

RESULTS

The combination was administered in 12 patients with endocarditis, 2 with vascular graft infection, and 2 with complicated bacteremia. Therapy had previously failed with vancomycin in 9 patients, daptomycin in 2, and sequential antibiotics in 5. Blood cultures were negative 72 hours after the first dose of the combination in all cases. The success rate was 69%, and only 1 of 5 deaths was related to the MRSA infection. Although the combination was safe in most patients (94%), a patient with liver cirrhosis died of multiorgan failure secondary to sodium overload. There were no episodes of breakthrough bacteremia or relapse.

CONCLUSIONS

Fosfomycin plus imipenem was an effective and safe combination when used as rescue therapy for complicated MRSA bloodstream infections and deserves further clinical evaluation as initial therapy in these infections.

Multi-drug-resistant Staphylococcus aureus and future chemotherapy

Staphylococcus (S.) aureus silently stays as our natural flora, and yet sometimes threatens our life as a tenacious pathogen. In addition to its ability to outwit our immune system, its multi-drug resistance phenotype makes it one of the most intractable pathogenic bacteria in the history of antibiotic chemotherapy. It conquered practically all the antibiotics that have been developed since 1940s. In 1961, the first MRSA was found among S. aureus clinical isolates. Then MRSA prevailed throughout the world as a multi-resistant hospital pathogen. In 1997, MRSA strain Mu50 with reduced susceptibility to vancomycin was isolated. Vancomycin-intermediate S. aureus (VISA), so named according to the CLSI criteria, was the product of adaptive mutation of S. aureus against vancomycin that had long been the last resort to MRSA infection. Here, we describe the genetic basis for the remarkable ability of S. aureus to acquire multi-antibiotic resistance, and propose a novel paradigm for future chemotherapy against the multi-resistant pathogens.

Vancomycin: does it still have a role as an antistaphylococcal agent?

The recognition of the shortcomings of vancomycin as an antistaphylococcal agent, together with the burgeoning availability of alternative effective antistaphylococcal antibiotics, has led to a reassessment of the role of this glycopeptide antimicrobial in clinical therapeutics. Evidence indicates that vancomycin is inferior to semisynthetic penicillins in the treatment of infections due to methicillin-susceptible Staphylococcus aureus. Additional evidence suggests that vancomycin may be inferior to some comparator agents in the treatment of infections due to methicillin-resistant S. aureus (MRSA). While high-level resistance remains rare, data from some centers suggest an evolutionary change in S. aureus, evidenced by reduced susceptibility to vancomycin. This, together with the problem of heteroresistance to vancomycin, as well as poor tissue penetration after its systemic administration, presents potential obstacles to the successful therapy of S. aureus infections with this glycopeptide. While it has been suggested that these problems may be overcome by administration of vancomycin in much higher doses, the efficacy and safety of this approach remains to be determined and will require randomized clinical trials for its demonstration. A number of novel agents with activity against MRSA have been introduced to clinical practice in the last 2 years and others are still in the investigational stage. Despite the fact that these newer agents have been compared with vancomycin in trials only designed to demonstrate noninferiority, some potential evidence of superiority over vancomycin has emerged. While the relative roles of each of these newer agents and vancomycin can only be determined definitively by performance of adequately powered randomized clinical trials, current evidence suggests that vancomycin may be an inferior therapeutic agent.

Activity of ceftaroline against Enterococcus faecium PBP5

The opportunistic human pathogen Enterococcus faecium overproduces the low-affinity PBP5. In clinical strains, mutations in PBP5 further reduce its acylation rate by β-lactams. Previous studies have reported that ceftaroline had poor inhibitory activity against β-lactam-resistant E. faecium strains. In this study, we show that ceftaroline exhibits killing activity against our laboratory-derived ampicillin-resistant E. faecium mutant that overproduces a wild-type PBP5 and that ceftaroline inactivates PBP5 much faster than benzylpenicillin and faster than ceftobiprole.

An alternate pathophysiologic paradigm of sepsis and septic shock: implications for optimizing antimicrobial therapy

The advent of modern antimicrobial therapy following the discovery of penicillin during the 1940s yielded remarkable improvements in case fatality rate of serious infections including septic shock. Since then, pathogens have continuously evolved under selective antimicrobial pressure resulting in a lack of significant improvement in clinical effectiveness in the antimicrobial therapy of septic shock despite ever more broad-spectrum and potent drugs. In addition, although substantial effort and money has been expended on the development novel non-antimicrobial therapies of sepsis in the past 30 years, clinical progress in this regard has been limited. This review explores the possibility that the current pathophysiologic paradigm of septic shock fails to appropriately consider the primacy of the microbial burden of infection as the primary driver of septic organ dysfunction. An alternate paradigm is offered that suggests that has substantial implications for optimizing antimicrobial therapy in septic shock. This model of disease progression suggests the key to significant improvement in the outcome of septic shock may lie, in great part, with improvements in delivery of existing antimicrobials and other anti-infectious strategies. Recognition of the role of delays in administration of antimicrobial therapy in the poor outcomes of septic shock is central to this effort. However, therapeutic strategies that improve the degree of antimicrobial cidality likely also have a crucial role.

Predictive factors for mortality in patients with methicillin-resistant Staphylococcus aureus bloodstream infection: impact on outcome of host, microorganism and therapy

Mortality related to methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infection (BSI) remains high, despite changes in the epidemiology. To analyze the current predictive factors for mortality we conducted a prospective study in a large cohort of patients with MRSA-BSI from 21 Spanish hospitals. Epidemiology, clinical data, therapy and outcome were recorded. All MRSA strains were analysed, including susceptibility to antibiotics and molecular characterization. Vancomycin MICs (V-MIC) were tested by the E-test and microdilution methods. Time until death was the dependent variable in a Cox regression analysis. Overall, 579 episodes were included. Acquisition was nosocomial in 59% and vascular catheter was the most frequent source (38%). A dominant PFGE genotype was found in 368 (67%) isolates, which belonged to Clonal Complex (CC)5 and carried SCCmecIV and agr2. Microdilution V-MIC50 and V-MIC90 were 0.7 and 1.0 mg/L, respectively. Initial therapy was appropriate in 66% of episodes. Overall mortality was observed in 179 (32%) episodes. The Cox-regression analysis identified age >70 years (HR 1.88), previous fatal disease (HR 2.16), Pitt score >1 (HR 3.45), high-risk source (HR 1.85) and inappropriate initial treatment (HR 1.39) as independent predictive factors for mortality. CC5 and CC22 (HR 0.52 and 0.45) were associated with significantly lower mortality rates than CC8. V-MIC ≥1.5 did not have a significant impact on mortality, regardless of the method used to assess it.

Rapid identification of Staphylococcus aureus directly from Bactec blood culture broth by the BinaxNOW S. aureus test

The BinaxNOW Staphylococcus aureus testing showed sensitivity, specificity, and positive and negative predicative values of 97.6%, 100%, 100%, and 98.4%, respectively, for identification of S. aureus from Bactec blood culture broth. Importantly, the test performed equally well on aerobic and anaerobic culture broth.

Worldwide challenges of multidrug-resistant bacteria in patients with hematologic malignancies

SUMMARY The emergence of infections due to multidrug-resistant (MDR) bacteria poses a major public health threat to all patients, but patients with hematologic malignancies are especially at risk. A common thread across all classes of bacteria is that increased reliance on and usage of broad-spectrum antibacterial agents, combined with the intrinsic ability of bacteria to develop and transmit resistance-conferring mutations, has led to the widespread dissemination of MDR organisms. In this article, we summarize the most worrisome MDR bacteria, assess their clinical impact on patients with hematologic malignancies and outline measures that are required to mitigate this impact.

Native valve right sided infective endocarditis

Right-sided infective endocarditis (RSIE) accounts for 5-10% of all cases of infective endocarditis (IE), and is predominantly encountered in the injecting drug user (IDU) population, where HIV and HCV coinfections often coexist. Staphylococcus aureus is the most common pathogen. The pathogenesis of RSIE is still not well understood. RSIE usually presents as a persistent fever with respiratory symptoms whilst signs of systemic embolisation as seen in left-sided IE are notably absent. The prompt diagnosis of RSIE thus requires a high index of suspicion. Transthoracic echocardiography (TTE) can detect the majority of RSIE, whilst transoesophageal echocardiography (TOE) can increase sensitivity. Virulence of the causative organism and vegetation size are the major determinants of prognosis. Most cases of RSIE resolve with appropriate antibiotic administration.

Controlled multicenter evaluation of a bacteriophage-based method for rapid detection of Staphylococcus aureus in positive blood cultures

Staphylococci are a frequent cause of bloodstream infections (BSIs). Appropriate antibiotic treatment for BSIs may be delayed because conventional laboratory testing methods take 48 to 72 h to identify and characterize isolates from positive blood cultures. We evaluated a novel assay based on bacteriophage amplification that identifies Staphylococcus aureus and differentiates between methicillin-susceptible and methicillin-resistant S. aureus (MSSA and MRSA, respectively) in samples taken directly from signal-positive Bactec blood culture bottles within 24 h of positive signal, with results available within 5 h. The performance of the MicroPhage KeyPath MRSA/MSSA blood culture test was compared to conventional identification and susceptibility testing methods. At four sites, we collectively tested a total of 1,165 specimens, of which 1,116 were included in our analysis. Compared to standard methods, the KeyPath MRSA/MSSA blood culture test demonstrated a sensitivity, specificity, positive predictive value, and negative predictive value of 91.8%, 98.3%, 96.3%, and 96.1%, respectively, for correctly identifying S. aureus. Of those correctly identified as S. aureus (n = 334), 99.1% were correctly categorized as either MSSA or MRSA. Analysis of a subset of the data revealed that the KeyPath MRSA/MSSA blood culture test delivered results a median of 30 h sooner than conventional methods (a median of 46.9 h versus a median of 16.9 h). Although the sensitivity of the test in detecting S. aureus-positive samples is not high, its accuracy in determining methicillin resistance and susceptibility among positives is very high. These characteristics may enable earlier implementation of appropriate antibiotic treatment for many S. aureus BSI patients.

Persistent catheter-related Staphylococcus aureus bacteremia after catheter removal and initiation of antimicrobial therapy

OBJECTIVES

Catheter-related Staphylococcus aureus bacteremia (CRSAB) occasionally persists despite catheter removal and initiation of appropriate antimicrobial therapy. The aim of this study was to determine the incidence, risk factors, and outcomes of persistent CRSAB after catheter removal and initiation of antimicrobial therapy.

METHODS

Consecutive patients with CRSAB were prospectively included from over a 41-month period. We compared the clinical features, 40 bacterial virulence genes, and outcomes between patients with persistent CRSAB (i.e., bacteremia for >3 days after catheter removal and initiation of appropriate antimicrobial therapy) and non-persistent CRSAB.

RESULTS

Among the 220 episodes of CRSAB, the catheter was kept in place in 17 (6%) and removed in 203 (94%) cases. In 43 (21%) of the 203 episodes, bacteremia persisted for >3 days after catheter removal and initiation of antimicrobial therapy. Methicillin resistance (Odds ratio [OR], 9.01; 95% confidence interval [CI], 3.05-26.61; P<0.001), non-catheter prosthetic devices (OR, 5.37; 95% CI, 1.62-17.80; P=0.006), and renal failure (OR, 3.23; 95% CI, 1.48-7.08; P=0.003) were independently associated with persistent CRSAB. Patients with persistent CRSAB were more like to experience complication than were those with non-persistent CRSAB (72% vs. 15%; P<0.001). Among all episodes due to methicillin-resistant S. aureus, persistent CRSAB isolates were associated with accessory gene regulator (agr) group II (P= .04), but presence of other bacterial virulence genes, distribution of vancomycin minimum inhibitory concentration distribution, and frequency of vancomycin heteroresistance did not differ between the groups.

CONCLUSIONS

In patients with CRSAB, bacteremia persisted in 21% of cases despite catheter removal and initiation of antimicrobial therapy. Methicillin resistance, renal failure, and non-catheter prosthetic devices were independent risk factors for persistent CRSAB, which was associated with a higher rate of complications.

Prevalence and outcomes of antimicrobial treatment for Staphylococcus aureus bacteremia in outpatients with ESRD

Staphylococcus bacteremia is a common and life-threatening medical emergency, but it is treatable with appropriate antibiotic therapy. To identify opportunities that may reduce morbidity and mortality associated with S. aureus, we analyzed data from 293,094 chronic hemodialysis outpatients to characterize practices of antibiotic selection. In the study population, the overall rate of bacteremia was 15.4 per 100 outpatient-years; the incidence rate for methicillin-sensitive (MSSA) was 2.1 per 100 outpatient-years, and the incidence rate for methicillin-resistant (MRSA) S. aureus was 1.9 per 100 outpatient-years. One week after the collection of the index blood culture, 56.1% of outpatients with MSSA bacteremia were receiving vancomycin, and 16.7% of outpatients with MSSA were receiving cefazolin. Among MSSA-bacteremic patients who did not die or get hospitalized 1 week after blood culture collection, use of cefazolin was associated with a 38% lower risk for hospitalization or death compared with vancomycin (adjusted HR=0.62, 95% CI=0.46-0.84). In conclusion, vancomycin is commonly used to treat MSSA bacteremia in outpatients receiving chronic dialysis, but there may be more risk of treatment failure than observed among those individuals who receive a β-lactam antibiotic such as cefazolin.

Infectious Disease Consultation for Staphylococcus aureus Bacteremia Improves Patient Management and Outcomes

BACKGROUND: Staphylococcus aureus bacteremia (SAB) is a common, severe infectious disease with accepted standards of care. METHODS: A retrospective cohort study of all 233 SAB cases at the Minneapolis Veterans Affairs Medical Center (MVAMC) between October 2004 and February 2008 was performed to measure the impact of Infectious Disease (ID) consultation on conformance to standards and patient outcomes. Outcomes were classified as survived without relapse, relapsed, or died without relapse. ID involvement was classified as consultation, curbside, or no involvement. RESULTS: ID involvement occurred in 179/233 cases (77%). Management conformed to accepted standards in 162/197 cases (82%) evaluable for conformance. ID involvement was associated with increased conformance in univariable analysis and multivariable analysis adjusted for propensity for ID consultation (OR 5.9, 95% CI 2.5 - 13.8). Relapse occurred in 14/156 cases (9%) in which therapy conformed to standards compared with 8/35 cases (23%) in which therapy did not conform to standards (p=0.045). Relapse was more common in older patients (OR 1.05, CI 1.01-1.09) and in cases without ID involvement (OR 3.02, CI 1.003-9.1). Death was associated with greater Charlson Index scores (OR 1.89, CI 1.4-2.5). Of 111 cases with definitely or possibly infected devices, relapse occurred in 9/92 cases (9.8%) in which the device was wholly or partially removed compared with 6/19 cases (32%) in which the device was left in place (p=0.02). CONCLUSIONS: ID involvement in SAB cases was associated with increased adherence to accepted standards and fewer relapses. ID consultation should be performed for all SAB cases.

Activity of oxacillin versus that of vancomycin against oxacillin-susceptible mecA-positive Staphylococcus aureus clinical isolates evaluated by population analyses, time-kill assays, and a murine thigh infection model

We compared the activity of dicloxacillin with that of vancomycin against 15 oxacillin-susceptible, methicillin-resistant Staphylococcus aureus (OS-MRSA) clinical isolates. By population analyses, we found that 6 OS-MRSA isolates were able to grow in the presence of up to 8 μg/ml dicloxacillin and 9 isolates were able to grow in 12 to >32 μg/ml dicloxacillin; all isolates grew in up to 2 μg/ml vancomycin. Both drugs exhibited similar bactericidal activities. In experimental infections, the therapeutic efficacy of dicloxacillin was significant (P < 0.05 versus untreated controls) in 10 OS-MRSA isolates and vancomycin was effective (P < 0.05) against 12 isolates; dicloxacillin had an efficacy that was comparable to that of vancomycin (P > 0.05) in 8 isolates. The favorable response to dicloxacillin treatment might suggest that antistaphylococcal penicillins could be used against OS-MRSA infections.