Staphylococcus aureus Bacteremia, Risk Factors, Complications, and Management

Safety and effectiveness of fifth generation cephalosporins for the treatment of methicillin-resistant staphylococcus aureus bloodstream infections: a narrative review exploring past, present, and future

INTRODUCTION

Methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infection (BSI) is a major issue in healthcare, since it is often associated with endocarditis or deep site foci. Relevant morbidity and mortality associated with MRSA-BSIs forced the development of new antibiotic strategies; in particular, this review will focus the attention on fifth-generation cephalosporins (ceftaroline/ceftobiprole), that are the only ß-lactams active against MRSA.

AREAS COVERED

The review discusses the available randomized controlled trials and real-world observational studies conducted on safety and effectiveness of ceftaroline/ceftobiprole for the treatment of MRSA-BSIs. Finally, a proposal of MRSA-BSI treatment flowchart, based on fifth-generation cephalosporins, is described.

EXPERT OPINION

The use of anti-MRSA cephalosporins is an acceptable choice either in monotherapy or combination therapy for the treatment of MRSA-BSIs due to their relevant effectiveness and safety. Particularly, their use may be advisable in combination therapy in case of severe infections (including endocarditis or persistent bacteriemia) or in monotherapy in subjects at higher risk of drugs-induced toxicity with older regimens. On the contrary, caution should be taken in case of suspected/ascertained central nervous system infections due to inconsistent data regarding penetration of these drugs in cerebrospinal fluid and brain tissues.

In silico Evaluation of a Vancomycin Dosing Guideline Among Adults with Serious Infections

BACKGROUND

This study aimed to compare the achievement of pharmacokinetic-pharmacodynamic (PK-PD) exposure targets for vancomycin using a newly developed dosing guideline with product-information-based dosing in the treatment of adult patients with serious infections.

METHODS

In silico product-information- and guideline-based dosing simulations for vancomycin were performed across a range of doses and patient characteristics, including body weight, age, and renal function at 36-48 and 96 hours, using a pharmacokinetic model derived from a seriously ill patient population. The median simulated concentration and area under the 24-hour concentration-time curve (AUC 0-24 ) were used to measure predefined therapeutic, subtherapeutic, and toxicity PK-PD targets.

RESULTS

Ninety-six dosing simulations were performed. The pooled median trough concentration target with guideline-based dosing at 36 and 96 hours was achieved in 27.1% (13/48) and 8.3% (7/48) of simulations, respectively. The pooled median AUC 0-24 /minimum inhibitory concentration ratio with guideline-based dosing at 48 and 96 hours was attained in 39.6% (19/48) and 27.1% (13/48) of simulations, respectively. Guideline-based dosing simulations yielded improved trough target attainment compared with product-information-based dosing at 36 hours and significantly less subtherapeutic drug exposure. The toxicity threshold was exceeded in 52.1% (25/48) and 0% (0/48) for guideline- and product-information-information-based dosing, respectively ( P < 0.001).

CONCLUSIONS

A Critical care vancomycin dosing guideline appeared slightly more effective than standard dosing, as per product information, in achieving PK-PD exposure associated with an increased likelihood of effectiveness. In addition, this guideline significantly reduced the risk of subtherapeutic exposure. The risk of exceeding toxicity thresholds, however, was greater with the guideline, and further investigation is suggested to improve dosing accuracy and sensitivity.

Design, Synthesis, and Biological Activity of Thioguanine-Modified Pleuromutilin Derivatives

Antibiotic overuse has caused the increasingly serious problem of bacterial drug resistance, with numerous marketed antibiotics exhibiting significantly reduced activity against drug-resistant bacteria. Therefore, there is urgent demand for the development of novel antibiotics. Pleuromutilin is a tricyclic diterpene exhibiting antibacterial activity against Gram-positive bacteria and is currently considered the most promising natural antibiotic. In this study, novel pleuromutilin derivatives were designed and synthesized by introducing thioguanine units, and their antibacterial activities against drug-resistant strains were evaluated in vitro and in vivo. Compound 6j was observed to have a rapid bactericidal effect, low cytotoxicity, and potent antibacterial activity. The in vitro results suggest that 6j has a significant therapeutic effect on local infections, and its activity is equal to that of retapamulin, an anti-Staphylococcus aureus pleuromutilin derivative.

The sound of blood: photoacoustic imaging in blood analysis

Blood analysis is a ubiquitous and critical aspect of modern medicine. Analyzing blood samples requires invasive techniques, various testing systems, and samples are limited to relatively small volumes. Photoacoustic imaging (PAI) is a novel imaging modality that utilizes non-ionizing energy that shows promise as an alternative to current methods. This paper seeks to review current applications of PAI in blood analysis for clinical use. Furthermore, we discuss obstacles to implementation and future directions to overcome these challenges. Firstly, we discuss three applications to cellular analysis of blood: sickle cell, bacteria, and circulating tumor cell detection. We then discuss applications to the analysis of blood plasma, including glucose detection and anticoagulation quantification. As such, we hope this article will serve as inspiration for PAI's potential application in blood analysis and prompt further studies to ultimately implement PAI into clinical practice.

Correlating the physico-chemical properties of two conventional glazed porcelain stoneware tiles in relation to cleanability and sanitization

Keeping surfaces clean can reduce the spread of infections. In particular, to decrease the potential for SARS CoV-2 contamination, performing disinfection of high-touching surfaces. Several ceramic tiles and porcelain stoneware tiles with antimicrobial properties are already available on the market. However, the widespread use of antimicrobial glazed stoneware tiles may require to replace the ceramic surfaces already present in many buildings. The unfeasibility of such replacement can be due to both product durability (lifetime of a tile is usually long) and/or monetary restrictions. Furthermore, as porcelain stoneware per se does not have antimicrobial activity, these materials are fabricated by adding chemical agents able to provide antimicrobial properties. This approach requires a compatibility between the antimicrobial agents and the glaze formulation, as well as a careful control of the firing cycle and the final properties of the ceramic products. It follows that the final cost of antimicrobial tiles is not competitive with that of conventional tiles. In the latter, the persistence of potential pathogens on the surfaces is a crucial problem to face: the longer a pathogen survives on a surface, the longer it may be a source of transmission and thus endanger susceptible subjects. In this work, bacteria's capacity to adhere and to be effectively removed from two conventional glazed porcelain stoneware tiles (under dirty and clean conditions) was investigated. Two different glazes were tested, one mainly glassy (glossy) and the other mainly crystalline (matt). The sanitization procedures were carried out by chemical and chemo-mechanical procedures. The results showed that chemo-mechanical sanitization was the most effective, and the best results could be obtained on the stoneware tiles coated with the mainly glassy glaze, with the lowest porosity and the lower roughness values and water contact angles, especially under clean conditions.

Staphylococcus aureus bacteremia and infective endocarditis in a patient with epidermolytic hyperkeratosis: A case report

BACKGROUND

Staphylococcus aureus bacteraemia (SAB) is among the leading causes of bacteraemia and infectious endocarditis. The frequency of infectious endocarditis (IE) among SAB patients ranges from 5% to 10%-12%. In adults, the characteristics of epidermolytic hyperkeratosis (EHK) include hyperkeratosis, erosions, and blisters. Patients with inflammatory skin diseases and some diseases involving the epidermis tend to exhibit a disturbed skin barrier and tend to have poor cell-mediated immunity.

CASE SUMMARY

We describe a case of SAB and infective endocarditis in a 43-year-old male who presented with fever of unknown origin and skin diseases. After genetic tests, the skin disease was diagnosed as EHK.

CONCLUSION

A breached skin barrier secondary to EHK, coupled with inadequate sanitation, likely provided the opportunity for bacterial seeding, leading to IE and deep-seated abscess or organ abscess. EHK may be associated with skin infection and multiple risk factors for extracutaneous infections. Patients with EHK should be treated early to minimize their consequences. If patients with EHK present with prolonged fever of unknown origin, IE and organ abscesses should be ruled out, including metastatic spreads.

Preexisting Atrial Fibrillation Associated with Higher Mortality in Patients with Methicillin-Resistant Staphylococcus aureus Bloodstream Infections: Analysis of the National Inpatient Sample

Background

The purpose of this study was to investigate the prevalence of preexisting atrial fibrillation (AF) in patients with MRSA-BSI during a three-year period and the impact of preexisting AF on MRSA-BSI outcomes.

Methods

This was a retrospective analysis performed using the National Inpatient Sample (NIS) over a three-year period (2016, 2017, 2018) for patients with MRSA-BSI as a principal diagnosis with and without preexisting AF. The primary outcome was mortality with secondary outcomes of acute coronary syndrome, cardiac arrest, cardiogenic shock, endocarditis, respiratory failure, acute kidney injury, length of stay, hospital cost, and patient charge. A univariate and multivariable logistic regression analysis estimated clinical outcomes.

Results

Preexisting AF in patients with MRSA-BSI significantly increased the primary outcome of the study, mortality (1.67% vs. 0.66%, p=0.030) with an adjusted odds ratio (AOR) of 1.98 (95% CI, 1.1–3.7). Secondary outcomes showed increased likelihood of cardiac arrest with MRSA-BSI and AF (0.48% vs. 0.2%, p=0.025) with an AOR 3.59 (CI 1.18–11.0), ACS (3.44% vs. 1.21%, p=0.008) with an AOR of 1.81 (CI 1.16–2.80), respiratory failure (8.92% vs. 4.02%, p=0.045) with an AOR 1.39 (CI 1.01–1.91), prolonged LOS (6.4 vs. 5.4 days, p=0.0001), increased hospital cost ($13,374 vs. $11,401, p=0.0001), and increased overall patient charge ($50,091 vs. $43,018, p=0.0001). Secondary outcomes that showed statistical significance included ACS (1,497 (3.44%) vs. 113 (1.21%), p=0.008) with an AOR of 1.81 (CI 1.16–2.80), cardiac arrest (209 (0.48%) vs. 19 (0.2%), p=0.025) with an AOR 3.59 (CI 1.18–11.0), and respiratory failure (3,881 (8.92%) vs. 374 (4.02%), p=0.045 with an AOR 1.39 (CI 1.01–1.91).

Conclusions

Preexisting AF is a significant risk factor for mortality in patients admitted for MRSA-BSI and increases risk for cardiac arrest, respiratory failure, and ACS. Considerations should focus on early treatment and source control, especially with AF given the mortality risk, increased hospitalization cost, and prolonged LOS.

Infección metastásica por Staphylococcus aureus en neonatos: a propósito de un caso

Metastatic infection as an infrequent complication of Staphylococcus aureus bacteremia in neonates is challenging due to the limited literature. To report the clinical case of a premature neonate who developed a metastatic infection as a complication of S. aureus bacteremia. We present the case of a premature neonate admitted to the Neonatal Intensive Care Unit, diagnosed with bacterial sepsis, neonatal respiratory distress syndrome, and involvement by premature rupture of the membrane. A patch catheter was inserted, and he was successfully treated for E. coli bacteremia. He was re-admitted for late sepsis due to infection with multi-sensitive S. aureus in a patch catheter. An abscess appears on the front of the chest due to S. aureus, confirming metastatic infection. The abscess was drained with a favorable resolution of the clinical picture. In neonates submitted to invasive procedures, it is essential to monitor the clinical evolution and early identification of metastatic infection after Staphylococcus aureus bacteremia and provide early treatment to avoid sequelae.

Native Vertebral Osteomyelitis in Patients with Staphylococcus aureus Bacteremia

BACKGROUND

The purpose of the study was to assess the epidemiology, risk factors and outcomes of native vertebral osteomyelitis (NVO) in patients with Staphylococcus aureus bacteremia (SAB).

METHODS

A retrospective institutional review was conducted at Mayo Clinic, Minnesota. Patients aged ≥ 18 years with SAB who developed NVO from January 1, 2006 to December 31, 2020 were included and 3-month follow-up data were abstracted. Data pertaining to patient demographics, risk factors and outcomes were recorded using REDCap. A 1:2 nested case-control analysis was performed, and controls were matched according to age, sex and year of SAB diagnosis.

RESULTS

A total of 103 patients had NVO. A majority (60.2%) of patients was male, with a median age of 62.0 years. Thirty-one (30.1%) cases were caused by methicillin-resistant S. aureus (MRSA). The lumbar spine was most commonly (57.6%) and the most commonly reported comorbid conditions included diabetes mellitus (36.9%) and coronary artery disease (27.2%). Mortality at three-month follow-up was 18.6%. Nested case-control analysis revealed that injection drug use (IDU) and tobacco consumption were significant risk factors associated with NVO, while chronic hemodialysis and chronic liver disease (CLD) were associated with a decreased risk of NVO.

CONCLUSIONS

Atherosclerotic vascular disease was prominent in our contemporary cohort with NVO in the setting of SAB. Diabetes mellitus, tobacco consumption, older age and male sex likely contributed to this profile. Because IDU was associated with NVO, an increased number of cases should be anticipated among patients with IDU given the ongoing opioid epidemic in the United States.

The Role of Galanin during Bacterial Infection in Larval Zebrafish

Galanin is a peptide that is conserved among different species and plays various roles in an organism, although its entire role is not completely understood. For many years, galanin has been linked mainly with the neurotransmission in the nervous system; however, recent reports underline its role in immunity. Zebrafish (Danio rerio) is an intensively developing animal model to study infectious diseases. In this study, we used larval zebrafish to determine the role of galanin in bacterial infection. We showed that knockout of galanin in zebrafish leads to a higher bacterial burden and mortality during Mycobacterium marinum and Staphylococcus aureus infection, whereas administration of a galanin analogue, NAX 5055, improves the ability of fish to control the infection caused by both pathogens. Moreover, the transcriptomics data revealed that a lower number of genes were regulated in response to mycobacterial infection in gal−/− mutants compared with their gal+/+ wild-type counterparts. We also found that galanin deficiency led to significant changes in immune-related pathways, mostly connected with cytokine and chemokine functions. The results show that galanin acts not only as a neurotransmitter but is also involved in immune response to bacterial infections, demonstrating the complexity of the neuroendocrine system and its possible connection with immunity.

Sulphonamide inhibition profile of Staphylococcus aureus β-carbonic anhydrase

This paper presents the production and kinetic and inhibitory characterisation of β-carbonic anhydrase from the opportunistic bacterium Staphylococcus aureus (SauBCA). From the eight different carbonic anhydrase (CA) families known to date, humans have only the α-form, whereas many clinically relevant pathogens have β- and/or γ-form(s). Based on this discovery, β- and γ-CAs have been introduced as promising new anti-infective targets. The results of this study revealed that recombinant SauBCA possesses significant CO₂ hydration activity with a k_cat of 1.46 × 10⁵ s^-1 and a k_cat/K_M of 2.56 × 10⁷ s^{- 1}M^-1. Its enzymatic function was inhibited by various sulphonamides in the nanomolar - micromolar range, and the K_i of acetazolamide was 628 nM. The best inhibitor was the clinically used sulfamide agent famotidine (K_i of 71 nM). The least efficient inhibitors were zonisamide and dorzolamide. Our work encourages further investigations of SauBCA in an attempt to discover novel drugs against staphylococcal infections.

Ceftriaxone as an Alternative Therapy for the Treatment of Methicillin-Susceptible Staphylococcus aureus Bacteremia after Initial Clearance of Bloodstream Infection

Introduction

Staphylococcus spp. represent the leading cause of hospital-acquired infections and second-most frequent pathogen in bloodstream infections. Methicillin-susceptible S. aureus (MSSA) comprise approximately half of all S. aureus isolates. Standard-of-care therapies (SOCTs) display high treatment success but require frequent dosing, are problematic in penicillin allergic patients, and are nephrotoxic. Ceftriaxone may represent an alternative treatment option.

Methods

Adult patients hospitalized from January 2015 through June 2016 with positive MSSA blood cultures and treated with SOCT or ceftriaxone for ≥48 hours were included. Exclusion criteria were receipt of vancomycin or concomitant systemic antimicrobials with activity against MSSA, polymicrobial infections, and pregnant patients. Additional data collected included demographics, source/site of infection, and treatment. The primary endpoint was clinical cure (normalization of white blood cell count and temperature within 7 days and clearance of bloodstream within 7 days). Readmission within 60 days, length of stay, and discharge disposition were collected.

Results

A total of 43 patients were included: 23 receiving SOCT and 20 receiving ceftriaxone group. Sixteen patients received SOCT prior to ceftriaxone while 4 patients were initiated on ceftriaxone. Clinical cure was observed in 18/23 (78%) and 10/20 (50%), respectively (P=0.052). Clinical failure was driven by leukocytosis despite clearance of their bloodstream infection in 3/23 (13%) SOCT group compared to 8/20 (40%) in the ceftriaxone group (P=0.043). Six patients (SOCT: 2, ceftriaxone: 4; p=0.669) had infection-related readmissions, and 1 death per group was observed.

Conclusion

Ceftriaxone poses a reasonable alternative to consider for MSSA bacteremia when cost and feasibility are concerns for outpatient parenteral therapy after initial clearance of bloodstream infections.

Comparison of quick SOFA and SIRS scales at the bedside of patients with Staphylococcus aureus bacteremia

Introducción:

Staphylococcus aureus es una de las principales causas de bacteriemia, adquirida en la comunidad o asociada con la atención en salud, la cual presenta un gran porcentaje de complicaciones y elevadas tasas de morbilidad y mortalidad. Los criterios SRIS (Systemic Inflammatory Response Syndrome) se han usado tradicionalmente con el fin de establecer la presencia de sepsis; sin embargo, recientemente se ha cuestionado su valor predictivo dada su baja sensibilidad y especificidad. En el 2016, apareció la escala qSOFA (quick Sequential Organ Failure Assessment), como una nueva herramienta para la evaluación rápida de las infecciones en los servicios de urgencias.

Objetivo.

Comparar las herramientas qSOFA y SRIS para la predicción de la bacteriemia por S. aureus.

Materiales y métodos.

Se hizo un estudio observacional sobre el comportamiento clínico de pacientes con bacteriemia por S. aureus para evaluar el perfil de resistencia fenotípica, algunas características sociodemográficas, clínicas y de laboratorio, las complicaciones y la mortalidad, así como los resultados de las evaluaciones con la escala qSOFA y los criterios SRIS, para establecer cuál podría predecir mejor la presencia de bacteriemia por S. aureus.

Resultados.

Se seleccionaron 26 pacientes con bacteriemia, en cuyas muestras S. aureus había sido el segundo germen más frecuentemente aislado. Se encontró una mortalidad del 50 % (13 casos) y una prevalencia del 30 % de S. aureus resistente a meticilina (SARM). Según los puntajes clínicos obtenidos, la escala qSOFA fue positiva en 30,8 % de los pacientes y los criterios SRIS lo fueron en el 92,3 %.

Discusión.

Se encontró una elevada mortalidad en la población analizada. La escala qSOFA fue menos efectiva para el diagnóstico que los criterios clásicos de reacción inflamatoria sistémica.

Antimicrobial activity and antibiotic synergy of a biphosphinic ruthenium complex against clinically relevant bacteria

The aim of this study was to investigate the antibacterial activity, antibiotic-associated synergy, and anti-biofilm activity of the ruthenium complex, cis-[RuCl₂ (dppb) (bqdi)]²⁺ (RuNN). RuNN exhibited antimicrobial activity against Gram-positive bacteria with minimum inhibitory concentration (MIC) values ranging from 15.6 to 62.5 µg ml^-1 and minimum bactericidal concentration (MBC) values ranging from 62.5 to 125 µg ml^-1. A synergistic effect against Staphylococcus spp. was observed when RuNN was combined with ampicillin, and the range of associated fractional inhibitory concentration index (FICI) values was 0.187 to 0.312. A time-kill curve indicated the bactericidal activity of RuNN in the first 1-5 h. In general, RuNN inhibited biofilm formation and disrupted mature biofilms. Furthermore, RuNN altered the cellular morphology of S. aureus biofilms. Further, RuNN did not cause hemolysis of erythrocytes. The results of this study provide evidence that RuNN is a novel therapeutic candidate to treat bacterial infections caused by Staphylococcus biofilms.

Higher Risk for All-cause Mortality of Staphylococcus aureus Bacteremia in Patients with Non-Dialysis Dependent Chronic Kidney Disease

Background

Staphylococcus aureus bacteremia (SAB) is a common and serious infection with a high mortality. Patients with chronic kidney disease (CKD) are vulnerable to SAB, but there have been few studies performed on the clinical characteristics and outcomes of SAB in CKD patients stratified by dialysis. We aimed to estimate the all-cause mortality and identify its predictors in patients with CKD.

Materials and Methods

We conducted a retrospective study on the patients with SAB hospitalized in a tertiary care center in Korea between March 2014 and December 2018. Kaplan-Meier analysis was performed to compare all-cause mortality following SAB among patients with non-dialysis dependent CKD (ND-CKD), those receiving dialysis, and those without CKD (non-CKD). The predictors of mortality among CKD patients were analyzed by Cox proportional hazards regression.

Results

As a total, 278 SAB of 43 ND-CKD (31 males), 58 dialysis (39 males), and 177 non-CKD (112 males) patients were included. The 30-day mortality was 39.5% in ND-CKD, 27.6% in dialysis, and 7.9% in non-CKD patients. The hazard ratio of all-cause mortality following SAB in ND-CKD was 2.335 (95% confidence interval, 1.203 – 4.531; P = 0.003), compared to non-CKD patients. For methicillin-resistant S. aureus bacteremia (MRSAB), the hazard ratio of all-cause mortality in ND-CKD was 2.628 (95% CI, 1.074 – 6.435; P = 0.011), compared to dialysis patients. Appropriate antibiotics <48 h was independently related to improved survival following SAB among ND-CKD (adjusted HR, 0.304; 95% CI, 0,108 – 0.857; P = 0.024) and dialysis (adjusted HR, 0.323; 95% CI, 0,116 – 0.897; P = 0.030) patients.

Conclusion

ND-CKD patients demonstrated poor outcome following SAB and administration of appropriate antibiotics within 48 h could reduce the risk for mortality.

Airborne Staphylococcus aureus in different environments-a review

The aim of the literature review was to describe the environments where the presence of airborne Staphylococcus aureus was confirmed and to catalogue the most often used methods and conditions of bioaerosol sampling to identify the bacteria. The basis for searching of studies on S. aureus in the bioaerosol in different environments was PubMed database resources from the years 1990-2019 (May). The review included studies which were carried on in selected environments: hospitals and other health care facilities, large-scale animal breeding, wastewater treatment plants, residential areas, educational institutions, and other public places. The highest concentrations and genetic diversity of identified S. aureus strains, including MRSA (methicillin-resistant S. aureus), have been shown in large-scale animal breeding. The role of the airborne transmission in dissemination of infection caused by these pathogens is empirically confirmed in environmental studies. Commonly available, well-described, and relatively inexpensive methods of sampling, identification, and subtyping guarantee a high reliability of results and allow to obtain fast and verifiable outcomes in environmental studies on air transmission routes of S. aureus strains.

Childress D, Maldonado RA. Comparison of Vancomycin Treatment Failures for Methicillin-Resistant Staphylococcus aureus Bacteremia Stratified by Minimum Inhibitory Concentration

Background: Optimal treatment of methicillin-resistant Staphylococcus aureus bacteremias (MRSABs) with vancomycin minimum inhibitory concentrations (MICs) high within the susceptible range is of concern due to the high rate of mortality and increased prevalence. Objective: The purpose of this study is to evaluate vancomycin treatment failures in patients with MRSAB stratified by vancomycin MIC. Methods: In this retrospective chart review, patients ≥19 years of age with MRSAB between July 2010 and December 2016 were included if they received intravenous vancomycin for ≥72 hours. Vancomycin treatment failures were compared between patients with vancomycin MICs of ≤1 mg/L and 2 mg/L. Vancomycin treatment failure was defined as microbiological failure at 7 days. Inpatient mortality, 30-day readmission, vancomycin-associated nephrotoxicity, and early bacteremia clearance at 48 to 96 hours were assessed as secondary endpoints. Results: Fifty-eight patients were included in the vancomycin MIC ≤1 mg/L group and 22 patients in the vancomycin MIC 2 mg/L group. No significant difference was found in vancomycin treatment failures at 7 days between groups (88% vs 91%, respectively; P = .850). At 96 hours, there was no significant difference in vancomycin treatment failures between groups (72% vs 90%, respectively; P = .127). No significant difference was found in mortality (P > .99) or 30-day readmission (P > .99). Conclusions: In this study, vancomycin treatment failures were not more prevalent in patients with vancomycin MIC of 2 mg/L at 7 days. Regardless of MIC, antibiotics should be switched to an alternative agent at 7 days for persistent bacteremia.

Epidemiology and Risk Factors for Bacteremia in Pediatric and Adolescent Patients

BACKGROUND

Epidemiology and risk factors for bacteremia in pediatric and adolescent patients have not been fully elucidated.

OBJECTIVE

The purpose of this study was to identify primary causative agents of bacteremia in pediatric and adolescent patients and associated risk factors. We hypothesized that these would be different than those seen in adults.

PATIENTS AND METHODS

This retrospective cohort, epidemiologic evaluation included patients admitted to a tertiary referral center from January 01, 2013, to December 31, 2015. Patients <18 years old with a confirmed positive blood culture were included; the first positive culture per organism per patient was analyzed. The primary outcome was to determine the most frequent causative organisms of bacteremia; the secondary outcome was an evaluation of risk factors for acquiring staphylococcal bacteremia.

RESULTS

A total of 913 isolates were evaluated, including 92 unique organisms. The most frequently identified were Staphylococcus epidermidis (238/913, 26.1%), followed by Staphylococcus aureus (136/913, 14.9%). Methicillin resistance was observed in 60.3% of S aureus. Two hundred thirty-six patients were included in the risk factor analysis. Prematurity, previous antibiotics, and intubation/ventilation were more likely associated with S epidermidis (P < .001, P < .001, and P = .032, respectively). Patients with a recent or previous hospitalization and those with dermatitis/eczema were statistically more likely to grow S aureus (P < .001, P = .029, respectively).

CONCLUSIONS

Although epidemiology of organisms associated with pediatric and adolescent bacteremia was similar to adults, risk factors were different than seen in that population. Further understanding of these risk factors may be helpful in developing preemptive infection control strategies in patients at risk.

Staphylococcus aureus Orchestrates Type 2 Airway Diseases

Staphylococcus aureus persistently colonizes the nostrils of one-third of the population but colonizes the sinus mucosa in up to 90% of patients with nasal polyps, implying a possible role in airway disease. Recent findings give new mechanistic insights into the ability of S. aureus to trigger type 2 inflammatory responses in the upper and lower airways. This novel concept of a S. aureus-driven chronic airway inflammatory disease suggests a new understanding of disease triggers. This article reviews the role of S. aureus in chronic inflammatory airway diseases and discusses possible therapeutic approaches to target S. aureus.

Prediction of methicillin-resistant Staphylococcus aureus bloodstream infection: do we need rapid diagnostic tests?

Staphylococcus aureus (SA) is the leading cause of bloodstream infection (BSI). The incidence of methicillin-resistant SA (MRSA) has decreased in France and Europe since one decade. Early and precise prediction of methicillin susceptibility is needed to improve probabilistic antibiotic therapy of MRSA-BSI. The aim of this study was to identify MRSA-BSI risk factors at admission and evaluate which patients need costly rapid diagnostic tests. A single-center retrospective descriptive study of all diagnosed SA-BSI was conducted in a French University Hospital between January 2015 and December 2016. All medical charts were reviewed. Univariate and multivariate analyses by a logistic regression model were performed on the data. We then build a prediction score of MRSA-BSI by assigning one point for each of the risk factor identified. During the study period, 151 SA-BSI were identified including 32 (21%) MRSA-BSI. In multivariate analysis, three factors were associated with MRSA-BSI: coming from long-term care facility, known previous MRSA colonization and/or infection, and chronic renal disease. Among our population, respectively, 5% and 100% had a MRSA-BSI when no or three risk factors were identified. Therefore, among the PCR performed, 43 (96%) could be avoided according to our clinical score. In our study, methicillin-susceptible SA and MRSA-BSI can be predictable by counting MRSA risk factors. This prediction rule could avoid the use of expensive rapid diagnostic tests. Prospective studies and prediction rules could help physicians to predict SA-BSI susceptibility to improve appropriate empiric therapy choice.

Curcumin nanoparticles are a promising anti-bacterial and anti-inflammatory agent for treating periprosthetic joint infections

Background

Periprosthetic joint infections (PJIs) have a high incidence of recurrence after total joint replacement and are difficult to treat by debridement or antibiotic treatment. Curcumin is a natural product with anti-inflammatory and anti-bacterial properties. The low bioactivity of curcumin in water restricts its clinical application. Curcumin nanoparticles (CURN) were developed to overcome this limitation.

Methods

In this study, the therapeutic effects of CURN and their anti-inflammatory functions were investigated in a Staphylococcus aureus biofilm-induced PJIs model.

Results

CURN first attenuated the biofilm-induced expansion of myeloid-derived suppressor cells (MDSCs) and then regulated M1- and M2-phenotypic MDSC expression. Down-regulation of cytokines and reactive oxygen species was considered as the mechanism of CURN in reversing the suppression of T cell proliferation. The recovery of bone permeative destruction demonstrated that CURN enhanced therapeutic potency of vancomycin in vivo.

Conclusion

This is the first study to demonstrate that CURN may be useful for treating PJIs.

Bacterial detection and identification from human synovial fluids on an integrated microfluidic system

An integrated microfluidic system was developed for detecting and identifying four bacteria in human joint fluid with the limit of detection as low as 100 colony forming units (CFUs) per milliliter (or 20 CFUs per reaction).

Identification of small molecule compounds active against Staphylococcus aureus and Proteus mirabilis

Staphylococcus aureus is a human pathogen rapidly becoming a serious health problem due to ease of acquiring antibiotic resistance. To help identify potential new drug candidates effective against the pathogen, a small focused library was screened for inhibition of bacterial growth against several pathogens, including S. aureus. At least one of the compounds, Compound 10, was capable of blocking bacterial growth of S. aureus in a test tube with IC₅₀ = 140 ± 30 μM. Another inhibitor, Compound 7, was bacteriostatic against S. aureus with IC₅₀ ranging from 33 to 150 μM against 3 different strains. However, only Compound 7 was bactericidal against P. mirabilis as examined by electron microscopy. Human cell line toxicity studies suggested that both compounds had small effect on cell growth at 100 μM concentration as examined by MTT assay. Analysis of compounds' structures showed lack of similarity to any known antibiotics and bacteriostatics, potentially offering the inhibitors as an alternative to existing solutions in controlling bacterial infections for selected pathogens.

Bloodstream infection caused by S. aureus in patients with cancer: a 10-year longitudinal single-center study

BACKGROUND

Staphylococcus aureus bloodstream infections (SABIs) represent a significant cause of morbidity and mortality in cancer patients. In this study, we compared infection characteristics and evaluated epidemiology and risk factors associated to SABIs and 30-day attributable mortality in cancer patients.

METHODS

Clinical and microbiological data from patients with cancer and positive blood cultures for S. aureus were retrieved during a 10-year period at an oncology reference center. Analyses were performed according to type of malignancy and infection with methicillin-resistant S. aureus (MRSA). Data was evaluated using competing risk analyses to identify risk factors associated to 30-day mortality and used to create a point system for mortality risk stratification.

RESULTS

We included 450 patients and MRSA was documented in 21.1%. Hospital-acquired infection, healthcare-associated pneumonia, and type-2 diabetes were associated to MRSA. In patients with hematologic malignancies, MRSA was more frequent if hospital-acquired, but less likely in primary bacteremia. Variables associated to mortality included abdominal source of infection, hematologic malignancy, MRSA, glucose levels > 140 mg/dL, and infectious endocarditis; catheter removal and initiation of adequate treatment within 48 h of positive blood culture were protective factors. From our designed mortality prediction scale, patients with a score > 3 had a 70.23% (95%CI 47.2-85.3%) probability of infection-related death at 30 days.

CONCLUSION

SABIs are a significant health burden for cancer patients. Risk factors for SABI-related mortality in this population are varied and impose a challenge for management to improve patient's outcomes. Risk stratification might be useful to evaluate 30-day mortality risk.

Staphylococcus aureus Bacteremia Incidence and Methicillin Resistance in Rural Thailand, 2006-2014

Staphylococcus aureus is a common cause of bloodstream infection and methicillin-resistant S. aureus (MRSA) is a growing threat worldwide. We evaluated the incidence rate of S. aureus bacteremia (SAB) and MRSA from population-based surveillance in all hospitals from two Thai provinces. Infections were classified as community-onset (CO) when blood cultures were obtained ≤ 2 days after hospital admission and as hospital-onset (HO) thereafter. The incidence rate of HO-SAB could only be calculated for 2009-2014 when hospitalization denominator data were available. Among 147,524 blood cultures, 919 SAB cases were identified. Community-onset S. aureus bacteremia incidence rate doubled from 4.4 (95% confidence interval [CI]: 3.3-5.8) in 2006 to 9.3 per 100,000 persons per year (95% CI: 7.6-11.2) in 2014. The highest CO-SAB incidence rate was among adults aged 50 years and older. Children less than 5 years old had the next highest incidence rate, with most cases occurring among neonates. During 2009-2014, there were 89 HO-SAB cases at a rate of 0.13 per 1,000 hospitalizations per year (95% CI: 0.10-0.16). Overall, MRSA prevalence among SAB cases was 10% (90/911) and constituted 7% (55/736) of CO-SAB and 20% (22/111) of HO-SAB without a clear temporal trend in incidence rate. In conclusion, CO-SAB incidence rate has increased, whereas MRSA incidence rate remained stable. The increasing CO-SAB incidence rate, especially the burden on older adults and neonates, underscores the importance of strong SAB surveillance to identify and respond to changes in bacteremia trends and antimicrobial resistance.

Biofilm production is not associated with poor clinical outcome in 485 patients with Staphylococcus aureus bacteraemia

OBJECTIVES

Staphylococcus aureus biofilm may constitute a major cause of virulence. Our main objective was to analyse whether there was an association between biofilm production and poor outcome in patients with S. aureus bacteraemia.

METHODS

We studied 485 S. aureus strains isolated from the blood of patients with bacteraemia from 2012 to 2015. We assessed in vitro biomass production using crystal violet assay and metabolic activity using tetrazolium salt assay. Strains were classified in tertile ranks as follows: low biomass producers, moderate biomass producers, high biomass producers, low metabolic activity, moderate metabolic activity and high metabolic activity. We excluded from analysis strains with moderate crystal violet and tetrazolium salt values. We defined poor outcome as fulfillment of one or more of the following conditions: 30-day attributable mortality, infective endocarditis, persistent bacteraemia and recurrent bacteraemia.

RESULTS

Outcome was poor in 199 (41.0%) of 485 S. aureus bacteraemia episodes. The distribution of poor outcome with respect to biomass production and metabolic activity was as follows: low biomass producers, 36.6% vs. high biomass producers, 43.2% (p 0.26); and low metabolic activity, 43.5% vs. high metabolic activity, 36.2% (p 0.91). The presence of methicillin-resistant S. aureus was the only characteristic that was more likely to be present in the high metabolic activity group (17.4% vs. 39.3%, p < 0.001).

CONCLUSIONS

Biofilm production, as determined by any of the methods used in the present study, is not associated with poor outcome in patients with S. aureus bacteraemia.

Incidence, prevalence, and management of MRSA bacteremia across patient populations-a review of recent developments in MRSA management and treatment

Methicillin-resistant Staphylococcus aureus (MRSA) infection is still a major global healthcare problem. Of concern is S. aureus bacteremia, which exhibits high rates of morbidity and mortality and can cause metastatic or complicated infections such as infective endocarditis or sepsis. MRSA is responsible for most global S. aureus bacteremia cases, and compared with methicillin-sensitive S. aureus, MRSA infection is associated with poorer clinical outcomes. S. aureus virulence is affected by the unique combination of toxin and immune-modulatory gene products, which may differ by geographic location and healthcare- or community-associated acquisition. Management of S. aureus bacteremia involves timely identification of the infecting strain and source of infection, proper choice of antibiotic treatment, and robust prevention strategies. Resistance and nonsusceptibility to first-line antimicrobials combined with a lack of equally effective alternatives complicates MRSA bacteremia treatment. This review describes trends in epidemiology and factors that influence the incidence of MRSA bacteremia. Current and developing diagnostic tools, treatments, and prevention strategies are also discussed.

Risk Factors for 30-Day Mortality in Patients with Methicillin-Resistant Staphylococcus aureus Bloodstream Infections

OBJECTIVES

Methicillin-resistant Staphylococcus aureus (MRSA) blood stream infections (BSI) are a major health care problem accounting for a large percentage of nosocomial infections. The aim of this study was to identify risk factors associated with 30-day mortality in patients with MRSA BSI.

METHODS

This was a retrospective study performed in Southeast Michigan. Over a 9- year period, a total of 1,168 patients were identified with MRSA BSI. Patient demographics and clinical data were retrieved and evaluated using electronic medical health records.

RESULTS

30-day mortality during the 9-year study period was 16%. Significant risk factors for 30-day mortality were age, cancer, heart disease, neurologic disease, nursing home residence and Charlson score >3 with Odds Ratio (OR) of 1.03 (CI 1.02-1.04), 2.29 (CI 1.40-3.75), 1.78 (CI 1.20-2.63), 1.65 (CI 1.08-2.25), 1.66 (CI 1.02 - 2.70) and 1.86 (CI 1.18 - 2.95) correspondingly. Diabetes mellitus, peripheral vascular disease (PVD), and readmission were protective factors for 30-day mortality with OR of 0.53 (CI 0.36-0.78), 0.46 (CI 0.26-0.84) and 0.13 (CI0.05 - 0.32) respectively.

CONCLUSIONS

Our study identified significant risk factors for 30-day mortality in patients with MRSA BSI. Interestingly, diabetes mellitus, PVD and readmission were protective effects on 30-day mortality. There was no statistically significant variability in 30-day mortality over the 9-year study period.

Bloodstream Infections

Bacteremia and sepsis are conditions associated with high mortality and are of great impact to health care operations. Among the top causes of mortality in the United States, these conditions cause over 600 fatalities each day. Empiric, broad-spectrum treatment is a common but often a costly approach that may fail to effectively target the correct microbe, may inadvertently harm patients via antimicrobial toxicity or downstream antimicrobial resistance. To meet the diagnostic challenges of bacteremia and sepsis, laboratories must understand the complexity of diagnosing and treating septic patients, in order to focus on creating algorithms that can help direct a more targeted approach to antimicrobial therapy and synergize with existing clinical practices defined in new Surviving Sepsis Guidelines. Significant advances have been made in improving blood culture media; as yet no molecular or antigen-based method has proven superior for the detection of bacteremia in terms of limit of detection. Several methods for rapid molecular identification of pathogens from blood cultures bottles are available and many more are on the diagnostic horizon. Ultimately, early intervention by molecular detection of bacteria and fungi directly from whole blood could provide the most patient benefit and contribute to tailored antibiotic coverage of the patient early on in the course of the disease. Although blood cultures remain as the best means of diagnosing bacteremia and candidemia, complementary testing with antigen tests, microbiologic investigations from other body sites, and histopathology can often aid in the diagnosis of disseminated disease, and application of emerging nucleic acid test methods and other new technology may greatly impact our ability to bacteremic and septic patients, particularly those who are immunocompromised.

Hospital-acquired Staphylococcus aureus primary bloodstream infection: A comparison of events that do and do not meet the central line-associated bloodstream infection definition

BACKGROUND

This study was done to describe the incidence and outcomes of primary hospital-acquired bloodstream infection (HABSI) secondary to Staphylococcus aureus (SA) that did and did not meet the National Healthcare Safety Network's (NHSN's) definition for central line-associated bloodstream infection (CLABSI).

METHODS

Consecutive hospitalized patients during a 48-month study period with an SA HABSI were categorized according to those who did and did not meet the NHSN's definitions for CLABSI and non-CLABSI. Primary outcomes were mortality at 30 days and 1 year. Secondary outcomes were the incidence of complicated bacteremia and the need for operative intervention secondary to the HABSI event.

RESULTS

A total of 122 episodes of primary SA HABSIs were identified: 78 (64%) were CLABSIs, and 44 (36%) were non-CLABSIs. Overall 30-day and 1-year mortality in the cohort was 21.3% and 38.5%, respectively, and did not differ significantly between the 2 groups. Complicated SA HABSI was significantly more common in the non-CLABSI group (15.9% [n = 7] vs 0% [n = 0], P ≤ .001).

CONCLUSIONS

Primary SA HABSI was associated with significant 30-day and 1-year mortality. Complications from SA non-CLABSI requiring surgical intervention were significantly more common than in those with a CLABSI event. Our findings affirm the significance of non-device-related hospital-acquired infections.

Does biomass production correlate with metabolic activity in Staphylococcus aureus?

We assessed agreement between the crystal violet binding assay and the XTT assay in the classification of biofilm production in 492 Staphylococcus aureus strains from bacteremic patients. We found that the overall correlation between the procedures was 46.5%. Biomass production and metabolic activity must be assessed simultaneously.

Efficacy of ampicillin against methicillin-resistant Staphylococcus aureus restored through synergy with branched poly(ethylenimine)

Beta-lactam antibiotics kill Staphylococcus aureus bacteria by inhibiting the function of cell-wall penicillin binding proteins (PBPs) 1 and 3. However, β-lactams are ineffective against PBP2a, used by methicillin-resistant Staphylococcus aureus (MRSA) to perform essential cell wall crosslinking functions. PBP2a requires teichoic acid to properly locate and orient the enzyme, and thus MRSA is susceptible to antibiotics that prevent teichoic acid synthesis in the bacterial cytoplasm. As an alternative, we have used branched poly(ethylenimine), BPEI, to target teichoic acid in the bacterial cell wall. The result is restoration of MRSA susceptibility to the β-lactam antibiotic ampicillin with a MIC of 1 μg/mL, superior to that of vancomycin (MIC = 3.7 μg/mL). A checkerboard assay shows synergy of BPEI and ampicillin. Nuclear magnetic resonance (NMR) data show that BPEI alters the teichoic acid chemical environment. Laser scanning confocal microscopy (LSCM) images show BPEI residing on the bacterial cell wall where teichoic acids and PBPs are located.

Mortality predictors of Staphylococcus aureus bacteremia: a prospective multicenter study

Background

Staphylococcus aureus is one of the causes of both community and healthcare-associated bacteremia. The attributable mortality of S. aureus bacteremia (SAB) is still higher and predictors for mortality and clinical outcomes of this condition are need to be clarified. In this prospective observational study, we aimed to examine the predictive factors for mortality in patients with SAB in eight Turkish tertiary care hospitals.

Methods

Adult patients with signs and symptoms of bacteremia with positive blood cultures for S. aureus were included. All data for episodes of SAB including demographics, clinical and laboratory findings, antibiotics, and outcome were recorded for a 3-year (2010–2012) period. Cox proportional hazard model with forward selection was used to assess the independent effect of risk factors on mortality. A 28-day mortality was the dependent variable in the Cox regression analysis.

Results

A total of 255 episodes of SAB were enrolled. The median age of the patients was 59 years. Fifty-five percent of the episodes were considered as primary SAB and vascular catheter was the source of 42.1 %. Healthcare associated SAB was defined in 55.7 %. Blood cultures yielded methicillin-resistant S. aureus (MRSA) as a cause of SAB in 39.2 %. Initial empirical therapy was inappropriate in 28.2 %. Although overall mortality was observed in 52 (20.4 %), 28-day mortality rate was 15.3 %. Both the numbers of initial inappropriate empirical antibiotic treatment and the median hours to start an appropriate antibiotic between the cases of fatal outcome and survivors after fever onset were found to be similar (12/39 vs 60/216 and 6 vs 12 h, respectively; p > 0.05). High Charlson comorbidity index (CCI) score (p = 0.002), MRSA (p = 0.017), intensive care unit (ICU) admission (p < 0.001) and prior exposure to antibiotics (p = 0.002) all were significantly associated with mortality. The Cox analysis defined age [Hazard Ratio (HR) 1.03; p = 0.023], ICU admission (HR 6.9; p = 0.002), and high CCI score (HR 1.32; p = 0.002) as the independent predictive factors mortality.

Conclusions

The results of this prospective study showed that age, ICU stay and high CCI score of a patient were the independent predictors of mortality and MRSA was also significantly associated with mortality in SAB.

Repurposing auranofin for the treatment of cutaneous staphylococcal infections

The scourge of multidrug-resistant bacterial infections necessitates the urgent development of novel antimicrobials to address this public health challenge. Drug repurposing is a proven strategy to discover new antimicrobial agents; given that these agents have undergone extensive toxicological and pharmacological analysis, repurposing is an effective method to reduce the time, cost and risk associated with traditional antibiotic innovation. In this study, the in vitro and in vivo antibacterial activities of an antirheumatic drug, auranofin, was investigated against multidrug-resistant Staphylococcus aureus. The results indicated that auranofin possesses potent antibacterial activity against all tested strains of S. aureus, including meticillin-resistant S. aureus (MRSA), vancomycin-intermediate S. aureus (VISA) and vancomycin-resistant S. aureus (VRSA), with minimum inhibitory concentrations (MICs) ranging from 0.0625μg/mL to 0.125μg/mL. In vivo, topical auranofin proved superior to conventional antimicrobials, including fusidic acid and mupirocin, in reducing the mean bacterial load in infected wounds in a murine model of MRSA skin infection. In addition to reducing the bacterial load, topical treatment of auranofin greatly reduced the production of inflammatory cytokines, including tumour necrosis factor-α (TNFα), interleukin-6 (IL-6), interleukin-1 beta (IL-1β) and monocyte chemoattractant protein-1 (MCP-1), in infected skin lesions. Moreover, auranofin significantly disrupted established in vitro biofilms of S. aureus and Staphylococcus epidermidis, more so than the traditional antimicrobials linezolid and vancomycin. Taken together, these results support that auranofin has potential to be repurposed as a topical antimicrobial agent for the treatment of staphylococcal skin and wound infections.

Antibacterial activity and therapeutic efficacy of Fl-P(R)P(R)P(L)-5, a cationic amphiphilic polyproline helix, in a mouse model of staphylococcal skin infection

The antibacterial activities and therapeutic efficacy of the cationic, unnatural proline-rich peptide Fl-P(R)P(R)P(L)-5 were evaluated against multidrug-resistant Staphylococcus aureus in a mouse model of skin infection. Fl-P(R)P(R)P(L)-5 showed potent activity against all clinical isolates of S. aureus tested, including methicillin- and vancomycin-resistant S. aureus (MRSA and VRSA, respectively). Fl-P(R)P(R)P(L)-5 was also superior in clearing established in vitro biofilms of S. aureus and Staphylococcus epidermidis, compared with the established antimicrobials mupirocin and vancomycin. Additionally, topical treatment of an MRSA-infected wound with Fl-P(R)P(R)P(L)-5 enhanced wound closure and significantly reduced bacterial load. Finally, 0.5% Fl-P(R)P(R)P(L)-5 significantly reduced the levels of the inflammatory cytokines tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-1 beta (IL-1β) in wounds induced by MRSA skin infection. In conclusion, the results of this study suggest the potential application of Fl-P(R)P(R)P(L)-5 in the treatment of staphylococcal skin infections.

Activity of ceftaroline and comparator agents tested against Staphylococcus aureus from patients with bloodstream infections in US medical centres (2009-13)

OBJECTIVES

The objective of this study was to evaluate the in vitro antimicrobial activity of ceftaroline and comparator agents tested against Staphylococcus aureus isolates causing bloodstream infection (BSI).

METHODS

A total of 4426 S. aureus isolates from patients with BSI were collected in 150 medical centres in the USA in 2009-13 and tested for susceptibility to ceftaroline and comparators by the CLSI broth microdilution method.

RESULTS

Overall, 45.5% of isolates were MRSA. Ceftaroline (MIC50/90, 0.25/1 mg/L) was active against 97.9% of S. aureus isolates at ≤1 mg/L (highest MIC, 2 mg/L). Daptomycin (MIC50/90, 0.25/0.5 mg/L), linezolid (MIC50/90, 1/2 mg/L) and vancomycin (MIC50/90, 1/1 mg/L) were active against ≥99.8% of isolates at the respective susceptible breakpoints. Susceptibility rates for clindamycin (MIC50/90, ≤0.25/>2 mg/L) and levofloxacin (MIC50/90, ≤0.5/>4 mg/L) were 80.8% and 59.2%, respectively. Against MSSA, ceftaroline (MIC50/90, 0.25/0.25 mg/L; 100.0% susceptible) was 16-, 4-8- and 4-fold more active in vitro (based on MIC50/90) than ceftriaxone (MIC50/90, 4/4 mg/L), linezolid (MIC50/90, 1/2 mg/L) and vancomycin (MIC50/90, 1/1 mg/L), respectively, and slightly more potent than daptomycin (MIC50/90, 0.25/0.5 mg/L). When tested against MRSA, ceftaroline was active against 95.4% and 100.0% of isolates at ≤1 and ≤2 mg/L, respectively. Moreover, ceftaroline retained significant activity against S. aureus with reduced susceptibility to vancomycin, daptomycin, clindamycin, levofloxacin and trimethoprim/sulfamethoxazole.

CONCLUSIONS

Ceftaroline demonstrated potent in vitro activity when tested against a large collection of contemporary (2009-13) S. aureus isolates causing BSI in US hospitals.

Thiol activated prodrugs of sulfur dioxide (SO2) as MRSA inhibitors

Drug resistant infections are becoming common worldwide and new strategies for drug development are necessary. Here, we report the synthesis and evaluation of 2,4-dinitrophenylsulfonamides, which are donors of sulfur dioxide (SO2), a reactive sulfur species, as methicillin-resistant Staphylococcus aureus (MRSA) inhibitors. N-(3-Methoxyphenyl)-2,4-dinitro-N-(prop-2-yn-1-yl)benzenesulfonamide (5e) was found to have excellent in vitro MRSA inhibitory potency. This compound is cell permeable and treatment of MRSA cells with 5e depleted intracellular thiols and enhanced oxidative species both results consistent with a mechanism involving thiol activation to produce SO2.

Predictors of treatment failure and mortality in native septic arthritis

The aims of this study are to analyse the characteristics of septic arthritis stratified by age and to identify the predictors of treatment failure and mortality in septic arthritis. A retrospective single-centre study was conducted in patients with native septic arthritis between 1994 and 2012. The primary outcome was treatment failure. Secondary outcomes included mortality, complications, endocarditis, bacteraemia, hospital readmission and the duration of the hospital stay. Logistic regression analyses with a propensity score were performed to identify the predictors of response and mortality. Additional analyses were performed according to age and the initial treatment (surgery or conservative). A total of 186 patients were studied. The median (interquartile range) age was 64 (46, 74) years, and the percentage of male patients was 68.9%. A logistic regression analysis showed that Staphylococcus aureus infection [OR 2.39 (1.20-4.77), p = 0.013], endocarditis [OR 4.74 (1.16-19.24), p = 0.029] and the involvement of joints difficult to access with needle drainage [OR 2.33 (1.06-5.11), p = 0.034] predict treatment failure and that age [OR 1.27 (1.07 = 1.50), p = 0.005], the leucocyte count at baseline [OR 1.01 (1.00-1.02), p = 0.023], bacteraemia [OR 27.66 (1.39-551.20), p = 0.030], diabetes mellitus [OR 15.33 (1.36-172.67), p = 0.027] and chronic renal failure [OR 81.27 (3.32-1990.20), p = 0.007] predict mortality. No significant differences in treatment failure by age were found. In septic arthritis, the predictors of mortality and the predictors of treatment failure differ. The predictors of treatment failure concern local factors and systemic complications, whereas conditions related to the host's immune competence, such as age and comorbidities that hamper the host's response, predict mortality.

Phenotypic and genotypic characterization of daptomycin-resistant methicillin-resistant Staphylococcus aureus strains: relative roles of mprF and dlt operons

Development of in vivo daptomycin resistance (DAP-R) among Staphylococcus aureus clinical isolates, in association with clinical treatment failures, has become a major therapeutic problem. This issue is especially relevant to methicillin-resistant S. aureus (MRSA) strains in the context of invasive endovascular infections. In the current study, we used three well-characterized and clinically-derived DAP-susceptible (DAP-S) vs. resistant (DAP-R) MRSA strain-pairs to elucidate potential genotypic mechanisms of the DAP-R phenotype. In comparison to the DAP-S parental strains, DAP-R isolates demonstrated (i) altered expression of two key determinants of net positive surface charge, either during exponential or stationary growth phases (i.e., dysregulation of dltA and mprF), (ii) a significant increase in the D-alanylated wall teichoic acid (WTA) content in DAP-R strains, reflecting DltA gain-in-function; (iii) heightened elaboration of lysinylated-phosphatidylglyderol (L-PG) in DAP-R strains, reflecting MprF gain-in-function; (iv) increased cell membrane (CM) fluidity, and (v) significantly reduced susceptibility to prototypic cationic host defense peptides of platelet and leukocyte origins. In the tested DAP-R strains, genes conferring positive surface charge were dysregulated, and their functionality altered. However, there were no correlations between relative surface positive charge or cell wall thickness and the observed DAP-R phenotype. Thus, charge repulsion mechanisms via altered surface charge may not be sufficient to explain the DAP-R outcome. Instead, changes in the compositional or biophysical order of the DAP CM target of such DAP-R strains (i.e., increased fluidity) may be essential to this phenotype. Taken together, DAP-R in S. aureus appears to involve multi-factorial and strain-specific adaptive mechanisms.

Oritavancin activity against Staphylococcus aureus causing invasive infections in U.S. and European hospitals: a 5-year international surveillance program

In this study, oritavancin had modal MIC, MIC50, and MIC90 values of 0.03, 0.03, and 0.06 μg/ml, respectively, against Staphylococcus aureus. Similar results (MIC50/90, 0.03/0.06 μg/ml) were observed against methicillin-resistant and -susceptible isolates and those demonstrating multidrug-resistant (MDR) and non-MDR phenotypes. When oritavancin (MIC50/90, 0.06/0.12 mg/ml) was tested against S. aureus with elevated MIC values for daptomycin (i.e., 1 to 4 mg/ml) and vancomycin (i.e., 2 mg/ml), it showed MIC results 2-fold higher than those for the more susceptible vancomycin or daptomycin counterparts (MIC50/90, 0.03/0.06 mg/ml), yet it inhibited these isolates at ≤0.25 mg/ml.