Community-associated methicillin-resistant Staphylococcus aureus bacteremia and endocarditis among HIV patients: a cohort study

Therapeutic Potential of Green Synthesized Metallic Nanoparticles against Staphylococcus aureus

BACKGROUND

The recent treatment challenges posed by the widespread emergence of pathogenic Multidrug-Resistant (MDR) bacterial strains are a cause of huge health troubles worldwide. Infections caused by MDR organisms are associated with longer period of hospitalization, increased mortality, and inflated healthcare costs. Staphylococcus aureus is one of these MDR organisms identified as an urgent threat to human health by the World Health Organization. Infections caused by S. aureus may range from simple cutaneous infestations to life threatening bacteremia. S. aureus infections get easily escalated in severely ill, hospitalized and or immunocompromised patients with incapacitated immune system. Also, in HIV-positive patients S. aureus ranks amongst one of the most common comorbidities where it can further worsen a patient's health condition. At present anti-staphylococcal therapy is reliant typically on chemotherapeutics that are gathering resistance and pose unfavorable side-effects. Thus, newer drugs are required that can bridge these shortcomings and aid effective control against S. aureus.

OBJECTIVE

In this review, we summarize drug resistance exhibited by S. aureus and lacunae in current anti-staphylococcal therapy, nanoparticles as an alternative therapeutic modality. The focus lays on various green synthesized nanoparticles, their mode of action and application as potent antibacterial compounds against S. aureus.

CONCLUSION

Use of nanoparticles as anti-bacterial drugs has gained momentum in recent past and green synthesized nanoparticles, which involves microorganisms and plants or their byproducts for synthesis of nanoparticles offer a potent, as well as environment friendly solution in warfare against MDR bacte.

Multidrug-resistant Staphylococcus aureus nasal carriage among HIV-positive outpatients in Guangzhou, China: Prevalence, risk factors, phenotypic and molecular characteristics

INTRODUCTION

Data on comprehensive characterization of multidrug-resistant (MDR) Staphylococcus aureus (S. aureus) carriage in human immunodeficiency virus (HIV)-positive patients are limited. The objective of the present study is to determine the prevalence, risk factors, phenotypic and molecular characterization of MDR S. aureus isolated from HIV-positive population.

METHODS

A cross-sectional study was conducted to determine the characteristics of MDR S. aureus nasal carriage among HIV-positive outpatients in an HIV clinic from June to August 2017. Nasal swabs and risk factor data of the enrolled HIV-positive outpatients were collected. Phenotypic and molecular characteristics of MDR and non-MDR S. aureus isolates were analyzed. Risk factors for nasal carriage with MDR S. aureus were estimated by logistic regression. The relationship between phenotypic and molecular characteristics of S. aureus isolates was assessed by the correspondence analysis.

RESULTS

Overall, 1001 HIV-positive outpatients were included. The prevalence of MDR S. aureus nasal carriage was 15.18% (152/1001), and the proportion of multidrug resistance among S. aureus isolates was 60.08% (152/253). Having a history of respiratory tract infection was the risk factor for MDR S. aureus nasal carriage (adjusted odds ratio = 1.90, 95% confidence interval: 1.25-2.89). Multidrug resistance of S. aureus isolates was in good corresponding relationships with clonal complex (CC)5, CC15, CC59 and CC398.

CONCLUSIONS

We found high burden of multidrug resistance among S. aureus isolated from HIV-positive outpatients, particularly in those who had upper respiratory tract infection. Moreover, CC59 and CC398 are highly related to multidrug resistance of S. aureus isolates.

Epidemiology and Outcomes of Bloodstream Infections in HIV-Patients during a 13-Year Period

No data on antibiotic resistance in bloodstream infection (BSI) in people living with HIV (PLWH) exist. The objective of this study was to describe BSI epidemiology in PLWH focusing on multidrug resistant (MDR) organisms. A retrospective, single-center, observational study was conducted including all positive blood isolates in PLWH from 2004 to 2017. Univariable and multivariable GEE models using binomial distribution family were created to evaluate the association between MDR and mortality risk. In total, 263 episodes (299 isolates) from 164 patients were analyzed; 126 (48%) BSI were community-acquired, 137 (52%) hospital-acquired. At diagnosis, 34.7% of the patients had virological failure, median CD4 count was 207/μL. Thirty- and 90-day mortality rates were 24.2% and 32.4%, respectively. Thirty- and 90-day mortality rates for MDR isolates were 33.3% and 46.9%, respectively (p < 0.05). Enterobacteriaceae were the most prevalent microorganisms (29.8%), followed by Coagulase-negative staphylococci (21.4%), and S. aureus (12.7%). In BSI due to MDR organisms, carbapenem-resistant K. pneumoniae and methicillin-resistant S. aureus were associated with mortality after adjustment for age, although this correlation was not confirmed after further adjustment for CD4 < 200/μL. In conclusion, BSI in PLWH is still a major problem in the combination antiretroviral treatment era and it is related to a poor viro-immunological status, posing the question of whether it should be considered as an AIDS-defining event.

Clonal clusters and virulence factors of methicillin-resistant Staphylococcus Aureus: Evidence for community-acquired methicillin-resistant Staphylococcus Aureus infiltration into hospital settings in Chennai, South India

Background and Objective

Staphylococcus aureus is one of the major pathogens of nosocomial infections as wells as community-acquired (CA) infections worldwide. So far, large-scale comprehensive molecular and epidemiological characterisation of S. aureus from very diverse settings has not been carried out in India. The objective of this study is to evaluate the molecular, epidemiological and virulence characteristics of S. aureus in both community and hospital settings in Chennai, southern India.

Methods

S. aureus isolates were obtained from four different groups (a) healthy individuals from closed community settings, (b) inpatients from hospitals, (c) outpatients from hospitals, representing isolates of hospital-community interface and (d) HIV-infected patients to define isolates associated with the immunocompromised. Antibiotic susceptibility testing, multiplex polymerase chain reactions for detection of virulence and resistance determinants, molecular typing including Staphylococcal cassette chromosome mec (SCCmec) and agr typing, were carried out. Sequencing-based typing was done using spa and multilocus sequence typing (MLST) methods. Clonal complexes (CC) of hospital and CA methicillin-resistant S. aureus (MRSA) were identified and compared for virulence and resistance.

Results and Conclusion

A total of 769 isolates of S. aureus isolates were studied. The prevalence of MRSA was found to be 7.17%, 81.67%, 58.33% and 22.85% for groups a, b, c and d, respectively. Of the four SCCmec types (I, III, IV and V) detected, SCCmec V was found to be predominant. Panton-Valentine leucocidin toxin genes were detected among MRSA isolates harbouring SCCmec IV and V. A total of 78 spa types were detected, t657 being the most prevalent. 13 MLST types belonging to 9 CC were detected. CC1 (ST-772, ST-1) and CC8 (ST238, ST368 and ST1208) were found to be predominant among MRSA. CA-MRSA isolates with SCCmec IV and V were isolated from all study groups including hospitalised patients and were found to be similar by molecular tools. This shows that CA MRSA has probably infiltrated into the hospital settings.

Protection against Staphylococcus aureus Colonization and Infection by B- and T-Cell-Mediated Mechanisms

S. aureus is a leading cause of healthcare- and community-associated bacterial infections. S. aureus causes various illnesses, including bacteremia, meningitis, endocarditis, pneumonia, osteomyelitis, sepsis, and skin and soft tissue infections. S. aureus colonizes between 20 and 80% of humans; carriers are at increased risk for infection and transmission to others. The spread of multidrug-resistant strains limits antibiotic treatment options. Vaccine development against S. aureus has been unsuccessful to date, likely due to an inadequate understanding about the mechanisms of immune defense against this pathogen. The significance of our work is in illustrating the necessity of generating multipronged B-cell, Th1-, and Th17-mediated responses to S. aureus antigens in conferring enhanced and broad protection against S. aureus invasive infection, skin and soft tissue infection, and mucosal colonization. Our work thus, provides important insights for future vaccine development against this pathogen.

Staphylococcus aureus is a major cause of morbidity and mortality worldwide. S. aureus colonizes 20 to 80% of humans at any one time and causes a variety of illnesses. Strains that are resistant to common antibiotics further complicate management. S. aureus vaccine development has been unsuccessful so far, largely due to the incomplete understanding of the mechanisms of protection against this pathogen. Here, we studied the role of different aspects of adaptive immunity induced by an S. aureus vaccine in protection against S. aureus bacteremia, dermonecrosis, skin abscess, and gastrointestinal (GI) colonization. We show that, depending on the challenge model, the contributions of vaccine-induced S. aureus-specific antibody and Th1 and Th17 responses to protection are different: antibodies play a major role in reducing mortality during S. aureus bacteremia, whereas Th1 or Th17 responses are essential for prevention of S. aureus skin abscesses and the clearance of bacteria from the GI tract. Both antibody- and T-cell-mediated mechanisms contribute to prevention of S. aureus dermonecrosis. Engagement of all three immune pathways results in the most robust protection under each pathological condition. Therefore, our results suggest that eliciting multipronged humoral and cellular responses to S. aureus antigens may be critical to achieve effective and comprehensive immune defense against this pathogen.

A New Face of Cardiac Emergencies: Human Immunodeficiency Virus-Related Cardiac Disease

The human immunodeficiency virus epidemic is a major health challenge of the twenty-first century as the transition from infectious complications to noncommunicable disease becomes more evident. These patients may present to the emergency department with a variety of cardiovascular diseases, such as acute coronary syndromes, heart failure, pericardial disease, infective endocarditis, venothromboembolism, and other conditions. Increased awareness is needed among health care professionals to enhance adequate identification and promote prompt management of these patients.

Epidemiology and management of healthcare-associated bloodstream infections in non-neutropenic immunosuppressed patients: a review of the literature

Advancements in medicine have led to a considerable increase in the proportion of patients living with severe chronic diseases, malignancies, and HIV infections. Most of these conditions are associated with acquired immune-deficient states and treatment-related immunosuppression. Although infections as a result of neutropenia have long been recognized and strategies for management were developed, non-neutropenic immunosuppression has been overlooked. Recently, community-acquired infections in patients with frequent, significant exposure to healthcare settings and procedures have been classified as 'healthcare-associated infections' since they are more similar to hospital-acquired infections. Most of the non-neutropenic immunosuppressed patients have frequent contact with the healthcare system due to their chronic and severe diseases. In this review, we focus on the healthcare-associated bloodstream infections in the most common non-neutropenic immunosuppressive states and provide an update of the recent evidence for the management of these infections.

Antibiotic-Resistant Infections and Treatment Challenges in the Immunocompromised Host

This article reviews antibiotic resistance and treatment of bacterial infections in the growing number of patients who are immunocompromised: solid organ transplant recipients, the neutropenic host, and persons with human immunodeficiency virus and AIDS. Specific mechanisms of resistance in both gram-negative and gram-positive bacteria, as well as newer treatment options are addressed elsewhere, and are only briefly discussed in the context of the immunocompromised host.

HIV and Nonischemic Heart Disease

Human immunodeficiency virus (HIV)-associated heart disease encompasses a broad spectrum of diseases. HIV infection may involve the pericardium, myocardium, coronary arteries, pulmonary vasculature, and valves, as well as the systemic vasculature. Access to combination antiretroviral therapy, as well as health resources, has had a significant influence on the prevalence and severity of the effects on each cardiac structure. Investigations over the recent past have improved our understanding of the epidemiology and pathophysiology of HIV-associated cardiovascular disease. This review will focus on our current understanding of pathogenesis and risk factors associated with HIV infection and heart disease, and it will discuss relevant advances in diagnosis and management of these conditions.

Bloodstream infections in HIV-infected patients

In the combined antiretroviral therapy era, HIV-infected patients remain a vulnerable population for the onset of bloodstream infections (BSI). Worldwide, nontyphoid salmonellae, Streptococcus pneumoniae, Escherichia coli, Staphylococcus aureus and coagulase negative staphylococci are the most important pathogens. Intravenous catheter associated infection, skin-soft tissue infection and endocarditis are associated with Gram-positive bacteremia. Among the Gram-negative, nontyphoidal Salmonella have been previously correlated to sepsis. Other causes of BSI in HIV-infected patients are mycobacteria and fungi. Mycobacteria constitute a major cause of BSI in limited resource countries. Fungal BSI are not frequent and among them Cryptococcus neoformans is the most common life-threatening infection. The degree of immunosuppression remains the key prognostic factor leading to the development of BSI.

Prevalence and risk factors of methicillin-resistant Staphylococcus aureus colonization among HIV patients in Mekelle, Northern Ethiopia

HIV-positive individuals are at higher risk of Methicillin Resistant Staphylococcus aureus (MRSA) colonization and its related infection. There is limited data in the nation on the prevalence and risk factors of MRSA colonization among HIV patients. The aim of this study was to address the existing knowledge gap. Cross sectional study was carried out from September 2014 to February 2015 in three selected health centers and one general hospital. A standardized questionnaire was developed for collection of socio-demographic and clinical data. A total of 498 Nasal and throat swabs (two for each patient) were collected from 249 patients, transported and processed using standard bacteriological procedures. Data was analyzed using Chi square (X²) test and associated risk factors were determined. P < 0.05 was considered statistically significant. Out of 249 study participants, S. aureus was isolated from 81 (32.5 %) patients, with MRSA colonization rate of 6 (2.4 %). MRSA isolates were resistant to Ciprofloxacin and trimethoprim-sulphamethoxazole (16.7 % each), clindamycin (33.3 %) and erythromycin (50 %). However, all MRSA isolates were 100 % sensitive to Amikacin. History of hospitalization, percutaneous device usage, patients with a household member’s hospitalization and low CD₄ count (<200 cells/mm³) were significantly associated with S. aureus colonization (p < 0.05).

Isolation of Methicillin-Resistant Staphylococcus aureus (MRSA) from HIV Patients Referring to HIV Referral Center, Shiraz, Iran, 2011-2012

Extension of drug resistant Staphylococcus aureus strains is one of the problems of modern society. Presence of methicillin-resistant Staphylococcus aureus (MRSA) in HIV-infected individuals is an important cause of severe infections. Therefore, the main goal of this study was to determine the prevalence rate of MRSA carriage rate among HIV patients referring to the Shiraz HIV referral center (Shiraz, Iran) during 2011-2012. Nasal swabs were obtained from HIV positive patients and were cultured on differential and selective media to isolate Staphylococcus aureus, which was confirmed by standard biochemical tests. For isolation of MRSA isolates, bacterial suspensions were cultured on Muller-Hinton Agar containing NaCl and Oxacillin. Finally, data were analyzed by the SPSS software. Of 180 HIV patients, MRSA was isolated from nasal cavity of 23 (12.8%) patients. Most of the isolates were recovered from male subjects who were under 40 years old. No variables such as skin disease, history of hospitalization or infectious disease had significant association with the MRSA colonization rate. The presence of MRSA isolates in the nasal cavity of HIV patients in such a rate warns us about the potential spreading of MRSA among HIV patients in our society and emphasizes on establishing better prevention strategies.

Daptomycin for the Treatment of Infective Endocarditis: Results from European Cubicin(®) Outcomes Registry and Experience (EU-CORE)

INTRODUCTION

The European Cubicin(®) Outcomes Registry and Experience (EU-CORE(SM)) was a retrospective, non-interventional, multicenter study which evaluated the safety and effectiveness of daptomycin therapy in patients with Gram-positive infections including infective endocarditis (IE).

METHODS

Data from the EU-CORE registry were collected for patients with IE who had received at least one dose of daptomycin between January 2006 and April 2012, across 18 countries in Europe (12), Latin America (5) and Asia (1). Clinical outcomes were assessed as success (cured or improved), failure or non-evaluable. Adverse events (AEs) were recorded during treatment and for up to 30 days post-treatment; follow-up data were collected for 2 years.

RESULTS

Of 6075 patients included in the EU-CORE registry, 610 were diagnosed with IE as primary infection; 149 (24.4%) right-sided IE (RIE), 414 (67.9%) left-sided IE (LIE), and 47 (7.7%) with both right- and left-sided IE (BRLIE). Overall clinical success was achieved in 80.0% of patients (RIE 88.6%, LIE 76.6% and BRLIE 82.9%). Success rates for methicillin-resistant Staphylococcus aureus (MRSA) infections were 90.9%, 71.7% and 66.6% in patients with RIE, LIE and BRLIE, respectively. The overall sustained clinical success rate in patients followed for up to 2 years was 86.7% (RIE 93.5%, LIE 88.3% and BRLIE 77.8%). AEs deemed possibly related to daptomycin in the investigator's opinion were reported in 2 (1.3%) RIE, 18 (4.3%) LIE and 1 (2.1%) BRLIE patients. There were 11 (1.8%) patients (2 with RIE, 8 with LIE and 1 with BRLIE) with AEs of creatine phosphokinase elevation reported as possibly related to daptomycin.

CONCLUSION

Data from this real-world clinical setting showed that daptomycin was well tolerated and effective for the treatment of LIE and BRLIE in addition to RIE caused by Gram-positive bacteria, including MRSA. Two-year follow-up data showed that a high proportion of patients had a sustained response.

Cardiovascular disease associated with human immunodeficiency virus: a review

The cardiovascular manifestations of human immunodeficiency virus (HIV) infection have changed significantly following the introduction of highly active antiretroviral therapy (HAART) regimens. On one hand, HAART has altered the course of HIV disease, with longer survival of HIV-infected patients, and cardiovascular complications of HIV infection such as myocarditis have been reduced. On the other hand, HAART is associated with an increase in the prevalence of both peripheral and coronary arterial disease. As longevity increases in HIV-infected individuals, long-term effects, such as cardiovascular disease, are emerging as leading health issues in this population. In the present review article, we discuss HIV-associated cardiovascular disease, focusing on epidemiology, etiopathogenesis, diagnosis, prognosis, management and therapy. Cardiovascular involvement in treatment-naive patients is still important in situations such as non-adherence to treatment, late initiation of treatment, and/or limited access to HAART in developing countries. We therefore describe the cardiovascular consequences in treatment-naive patients and the potential effect of antiretroviral treatment on their regression, as well as the metabolic and cardiovascular implications of HAART regimens in HIV-infected individuals.

Characteristics, causes, and outcome of 54 episodes of bloodstream infections in a cohort of HIV patients

BACKGROUND

Patients infected with human immunodeficiency virus (HIV) have an increased risk for bloodstream infections (BSIs). Published recent data on characteristics, etiology, and outcome of BSIs in HIV patients in high income countries are scarce.

METHODS

Blood cultures from 2001 to 2011 from adult HIV patients were retrieved. Blood cultures considered to be contamination based on isolates and clinical context were excluded. Clinical and microbiological characteristics of BSIs and patients were described, those of community-acquired and nosocomial episodes were compared, and risk factors for 6-month mortality were analyzed.

RESULTS

We found 54 episodes of true BSI in 46 patients. Demographics were similar to those of the source cohort of all patients followed between 2001 and 2011. In 63% there was prior AIDS, in 91% a CD4 nadir below 200/mm(3), and in 72% a latest CD4 count < 200/mm(3). In 13% of patients BSI preceded a new HIV diagnosis within 1 week. Main causative microorganisms were coagulase-negative staphylococci (26%), Streptococcus pneumoniae (20%), and Enterococcus spp. (13%). The most frequent diagnoses were pneumonia (28%) and catheter-related BSI (CRBSI) (28%); 56% of episodes were nosocomial. The 1-month mortality rate was 17%, with a cause of death apparently unrelated to the BSI in five of nine episodes. The 6-month mortality was 28%. Factors of co-morbidity or immunodeficiency other than HIV were significantly associated with 6-month mortality.

CONCLUSIONS

BSIs in HIV-infected patients occur predominantly in patients with advanced HIV infection. Community-acquired bacteremic pneumococcal pneumonia and nosocomial staphylococcal CRBSIs are the main causes. Mortality following BSI is high, and seems to be driven by underlying complicated HIV infection.

USA300 Methicillin-Resistant Staphylococcus aureus Emerging as a Cause of Bloodstream Infections at Military Medical Centers

Background.

USA300 methicillin-resistant Staphylococcus aureus (MRSA) is a common cause of skin and soft-tissue infection (SSTI) in military personnel. USA300 MRSA has emerged as an important cause of healthcare-associated bloodstream infection (BSI) in metropolitan centers.

Objective.

To determine the prevalence, risk factors, and patient outcomes associated with USA300 MRSA BSI in military tertiary medical centers.

Design.

Retrospective case-control study.

Patients.

Patients admitted during the period 2001–2009 with MRSA BSI.

Setting.

Walter Reed Army Medical Center (Washington, DC) and National Naval Medical Center (Bethesda, MD) tertiary medical centers with 500 inpatient beds combined, which provide care to active duty service members and military beneficiaries.

Methods.

After identifying patients with MRSA BSI, we collected epidemiological data from electronic medical records and characterized bacterial isolates using pulsed-field gel electrophoresis (PFGE).

Results.

A total of 245 MRSA BSI cases were identified, and 151 isolates were available for analysis. Epidemiological characteristics for the 151 patients with available isolates included the following: mean age, 61 years; male sex, 70%; white race, 62%; and combat-wounded service members, 11%. The crude in-hospital mortality rate was 17%. PFGE demonstrated that 30 (20%) of 151 MRSA BSI cases with isolates available for analysis were due to USA300, and 27 (87%) of these 30 cases were healthcare-associated infection. USA300 was associated with a significantly increasing proportion of MRSA BSI when examined over sequential time periods: 2 (4%) of 51 isolates during 2001–2003, 9 (19%) of 47 isolates during 2004–2006, and 19 (36%) of 53 isolates during 2007–2009 (P<.001).

Conclusion.

USA300 MRSA is emerging as a cause of healthcare-associated BSI in tertiary military medical centers.

Methicillin-resistant Staphylococcus aureus in HIV patients: risk factors associated with colonization and/or infection and methods for characterization of isolates - a systematic review

Staphylococcus aureus is an important cause of infections and HIV-infected individuals are frequently susceptible to this pathogen. The aim of this study was to perform a systematic review to identify both the risk factors associated with colonization/infection by methicillin-resistant S. aureus in HIV patients and the methods used for characterization of isolates. An electronic search of articles published between January 2001 and December 2013 was first conducted. Among 116 studies categorized as being at a quality level of A, B or C, only 9 studies were considered to have high methodological quality (level A). The majority of these studies were retrospective (4/9 studies). The risk factors associated with colonization/infection by S. aureus were use of antimicrobials (4/9 studies), previous hospitalization (4/9 studies) and low CD4+ T lymphocyte counts (<200 cells/μl) (3/9 studies). Culture in mannitol salt agar (3/9 studies) and the latex agglutination test (5/9 studies) were the main methods used for bacterial phenotypic identification. Genotypic profiles were accessed by pulsed-field gel electrophoresis (6/9 studies) and USA300 was the most prevalent lineage (5/9 studies). Most isolates were resistant to erythromycin (3/9 studies) and susceptible to vancomycin (4/9 studies). Ultimately, use of antimicrobials and previous hospitalization were the main risk factors for colonization/infection by methicillin-resistant S. aureus in HIV-infected individuals. However, the numbers of evaluated patients, the exclusion and inclusion criteria and the characterization of the S. aureus isolates were not uniform, which made it difficult to establish the characteristics associated with HIV patients who are colonized/infected by S. aureus.

Daptomycin experience in patients with human immunodeficiency virus and resistant gram-positive infections

OBJECTIVES

This study was conducted to evaluate the clinical experience with daptomycin in the treatment of resistant gram-positive infections (GPIs) in patients with HIV infection.

METHODS

Using a retrospective, multicenter, and observational registry study, investigators assessed outcomes following daptomycin therapy in 78 patients (62 efficacy evaluable) infected with HIV and with resistant GPIs.

RESULTS

Overall, success rates by infection type were bacteremia 91% (20 of 22), endocarditis 91% (10 of 11), and bone/joint 100% (9 of 9). Success by pathogen was 93% (39 of 42), 93% (14 of 15), and 100% (5 of 5) for methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci, and methicillin-resistant coagulase-negative staphylococci, respectively. Daptomycin appeared to be well tolerated, with 9% having an adverse event possibly related to daptomycin and 4% discontinuing daptomycin.

CONCLUSIONS

In HIV-infected patients, daptomycin appears to be a useful agent for treating resistant GPIs.

BDCA1-positive dendritic cells (DCs) represent a unique human myeloid DC subset that induces innate and adaptive immune responses to Staphylococcus aureus Infection

Staphylococcus aureus bloodstream infection (bacteremia) is a major cause of morbidity and mortality and places substantial cost burdens on health care systems. The role of peripheral blood dendritic cells (PBDCs) in the immune responses against S. aureus infection has not been well characterized. In this study, we demonstrated that BDCA1(+) myeloid DCs (mDCs) represent a unique PBDC subset that can induce immune responses against S. aureus infection. BDCA1(+) mDCs could engulf S. aureus and strongly upregulated the expression of costimulatory molecules and production of proinflammatory cytokines. Furthermore, BDCA1(+) mDCs expressed high levels of major histocompatibility complex (MHC) class I and II molecules in response to S. aureus and greatly promoted proliferation and gamma interferon (IFN-γ) production in CD4 and CD8 T cells. Moreover, BDCA1(+) mDCs expressed higher levels of Toll-like receptor 2 (TLR-2) and scavenger receptor A (SR-A) than those on CD16(+) and BDCA3(+) mDCs, and these two receptors were both required for the recognition of S. aureus and the subsequent activation of BDCA1(+) mDCs. Finally, BDCA1(+) mDC-mediated immune responses against S. aureus were dependent on MyD88 signaling pathways. These results demonstrate that human BDCA1(+) mDCs represent a unique subset of mDCs that can respond to S. aureus to undergo maturation and activation and to induce Th1 and Tc1 immune responses.

Evaluation of vancomycin population susceptibility analysis profile as a predictor of outcomes for patients with infective endocarditis due to methicillin-resistant Staphylococcus aureus

Infective endocarditis due to methicillin-resistant Staphylococcus aureus (MRSA IE) is associated with high morbidity and mortality. Vancomycin continues to be the primary treatment for this disease. The emergence of heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA), defined as a modified population analysis profile (PAP) of ≥ 0.9, may affect patient outcomes. The objective of this study was to evaluate the relationship of vancomycin subpopulation susceptibility and the clinical outcomes of MRSA IE. We conducted a retrospective cohort study of patients treated with vancomycin for MRSA IE from 2002 to 2013 at the Detroit Medical Center. A modified PAP was used to measure the vancomycin PAP MIC and the PAP-to-area under the curve (AUC) ratio. Treatment failure was defined as bacteremia for ≥ 7 days or death attributed to MRSA. Classification and regression tree (CART) analysis was used to select a failure breakpoint between the PAP-AUC ratios and the PAP MIC. A total of 202 patients were included in the study. Twenty-seven percent of the patients had left-sided IE, 19% of the strains were hVISA, and 70% of the strains were staphylococcal cassette chromosome mec element (SCCmec) type IV. Overall treatment failure was observed in 64%; 59% had persistent bacteremia, and the 30-day attributable mortality rate was 21%. The CART breakpoint between failure and success in terms of the PAP-AUC ratio was 0.9035. On logistic regression analysis, intensive care unit (ICU) admission (adjusted odds ratio [aOR], 2.8; 95% confidence interval [CI], 1.5 to 5.2) and a PAP MIC of ≥ 4 mg/liter (aOR, 3.2; 95% CI, 1.3 to 8.4) were associated with failure (P = 0.001 and 0.015, respectively). A PAP MIC of ≥ 4 mg/liter and ICU admission were significant for treatment failure for patients with MRSA IE. The PAP-AUC ratio of ≥ 0.9035 predicted failure consistent with the hVISA definition. The role of population MIC analysis in predicting outcome with MRSA infections warrants further investigation.

Outcome and reinfection after Staphylococcus aureus bacteraemia in individuals with and without HIV-1 infection: a case-control study

OBJECTIVES

Individuals infected with HIV-1 are at an increased risk of Staphylococcus aureus bacteraemia (SAB). The aim of this study was to investigate mortality rate and risk of reinfection associated with SAB in HIV-1-infected individuals compared to individuals without HIV-1 infection.

SETTING

University hospital treating a third of the estimated 5000 individuals with HIV infection in Denmark.

PARTICIPANTS

HIV-1-infected (n=82) and sex-matched and age-matched uninfected (n=163) individuals with SAB in the time period 1 January 1995 to 31 December 2010.

PRIMARY OUTCOME MEASURES

30-day and 365-day mortality rate ratio and relative risk of reinfection.

RESULTS

Individuals with HIV had an increased risk of death at day 30 (OR 11.90 (95% CI 2.15 to 65.85)) compared to individuals without HIV. Other factors associated with mortality were age, a foreign device and Pitt score. HIV-related factors did not associate to mortality. During follow-up, there were 43 episodes of reinfection; in individuals with HIV infection at an incidence rate of 7.8 (95% CI 4.7 to 10.9)/100 person-years compared with 2.2 (95% CI 1.2 to 3.2)/100 person-years for individuals without HIV. In multivariate analysis, HIV status (OR 2.91 (95% CI 1.29 to 6.58) and injection drug use (OR 3.51 (95% CI 1.06 to 11.63) were independently associated with an increased risk of reinfection.

CONCLUSIONS

HIV-1 infection is associated with an increased risk of 30-day mortality after SAB and a very high rate of reinfection. Age, a foreign device and Pitt score predicted outcome. For patients infected with HIV, neither CD4 T-lymphocyte counts nor plasma HIV RNA levels were associated with 30-day outcome.

TRIAL REGISTRATION NUMBER

The study was approved by the Danish Data Protection Agency (record no. 2007-41-1196).

Mortality among patients with methicillin-resistant Staphylococcus aureus USA300 versus non-USA300 invasive infections: a meta-analysis

BACKGROUND

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has been found to be epidemiologically and microbiologically distinct from healthcare-associated MRSA. Most CA-MRSA infections are not invasive; however, fatal outcomes have been reported among healthy people with CA-MRSA invasive infections. Epidemiological studies have attributed a major burden of CA-MRSA infections in the United States to the predominant clone USA300. We investigated the association between USA300 invasive infections and mortality by conducting a systematic review and meta-analysis of studies that reported mortality rates associated with USA300 strains.

METHODS

We searched PubMed, bibliographies of other publications, and gray literature between January 2001 and December 2013. Observational studies of patients with an invasive MRSA infection were included. The exposure of interest was presence of USA300 invasive infection. Studies were included only if they provided MRSA PFGE types and if corresponding mortality data were the measured outcome. We pooled crude odds ratios (cORs) using a random-effects model. Woolf test of homogeneity and Q and I(2) statistics were assessed.

RESULTS

Of 574 articles identified by the search strategy, 8 met the inclusion criteria. Risk of mortality was significantly lower among patients with USA300 MRSA infections (pooled cOR, 0.63 [95% confidence interval (CI)], 0.49-0.81). There was a moderate degree of heterogeneity among study results (P = .29; I(2) = 18%). Results were observed to be heterogeneous due to study design, quality of studies, and definition of mortality.

CONCLUSIONS

MRSA invasive infection with USA300 does not appear to be associated with higher mortality compared with infections due to non-USA300 strains. Nevertheless, larger well-designed studies are warranted to further evaluate this association.

Impact of community-associated methicillin resistant Staphylococcus aureus on HIV-infected patients

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has emerged as an increasingly important pathogen, causing infections in persons who have no significant healthcare exposures. Persons with human immunodeficiency virus (HIV) infection have been disproportionately affected by CA-MRSA, with increased colonization and infection documented. Several factors are likely involved in the increased CA-MRSA burden observed among HIV-infected patients, including immune factors as well as healthcare and community exposures. Proposed community exposures that have been associated with increased CA-MRSA risk include substance abuse, incarceration, geographic area of residence, and social networks. This article explores these associations and reviews the current knowledge of the epidemiology, pathogenesis, clinical manifestations, and treatment of CA-MRSA in HIV-infected persons.

Community-acquired methicillin-resistant Staphylococcus aureus: the new face of an old foe?

The burden of infections caused by community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) is increasing among different patient populations globally. As CA-MRSA has become established in healthcare facilities, the range of infections caused by them has also increased. Molecular characterization of CA-MRSA isolates obtained from different centers has revealed significant diversity in their genetic backgrounds. Although many CA-MRSA strains are still susceptible to non-β-lactam antibiotics, multiresistance to non-β-lactam agents has emerged in some clones, posing substantial problems for empirical and directed therapy of infections caused by these strains. Some CA-MRSA clones have acquired the capacity to spread locally and internationally. CA-MRSA belonging to ST80-MRSA-IV and ST30-MRSA-IV appear to be the dominant clones in the countries of the Gulf Cooperation Council (GCC). The emergence of pandemic CA-MRSA clones not only limits therapeutic options but also presents significant challenges for infection control. Continued monitoring of global epidemiology and emerging drug resistance data is critical for the effective management of these infections.

Community-associated methicillin-resistant Staphylococcus aureus endocarditis 'down under': case series and literature review

Infective endocarditis is a common complication of Staphylococcus aureus bacteraemia, but literature reports of community-associated methicillin-resistant S. aureus (CA-MRSA) endocarditis are relatively uncommon and mostly comprise intravenous drug users (IVDUs) with the USA300 strain. We report 5 cases of CA-MRSA endocarditis in previously healthy young Australian adults, 4 in IVDUs. Morbidity was high with frequent septic emboli; 3 patients required cardiac surgery and 1 patient died. Typing revealed the 2 most common Australian strains, the Panton-Valentine leukocidin (PVL)-positive ST93 (Queensland) strain and the PVL-negative ST1 (WA-MRSA-1) strain.