Clinical practice guidelines by the infectious diseases society of america for the treatment of methicillin-resistant Staphylococcus aureus infections in adults and children

Pulmonary disposition of tedizolid following administration of once-daily oral 200-milligram tedizolid phosphate in healthy adult volunteers

This study assessed the pulmonary disposition of tedizolid, an oxazolidinone, in adult volunteers receiving 200 mg of the prodrug tedizolid phosphate orally every 24 h for 3 days to steady state. Plasma samples were collected over the dosing interval, and participants were randomized to undergo bronchoalveolar lavage (BAL) at 2, 6, 12, or 24 h after the last dose. Drug concentrations in plasma, BAL fluid, and alveolar macrophages (AM) were determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS), and the urea correction method was used to calculate epithelial lining fluid (ELF) concentrations. Pharmacokinetic parameters were estimated by noncompartmental methods followed by compartmental population pharmacokinetics. Penetration was calculated as the area under the concentration-time curve during the dosing interval (AUC(0-24)) for ELF and AM relative to the free AUC(0-24) (fAUC(0-24)) in plasma. The half-life and volume of distribution in plasma were 9.23 ± 2.04 h and 108.25 ± 20.53 liters (means ± standard deviations), respectively. Total AUC(0-24) in plasma was 25.13 ± 5.78 μg · h/ml. Protein binding was 89.44% ± 1.58%, resulting in a mean fAUC(0-24) of 2.65 ± 0.72 μg · h/ml in plasma. Mean concentrations (μg/ml) at 2, 6, 12, and 24 h were 9.05 ± 3.83, 4.45 ± 2.18, 5.62 ± 1.99, and 1.33 ± 0.59 in ELF and 3.67 ± 1.02, 4.38 ± 2.18, 1.42 ± 0.63, and 1.04 ± 0.52 in AM. ELF and AM penetration ratios were 41.2 and 20.0. The mean ELF penetration ratio after population analyses was 39.7. This study demonstrates that tedizolid penetrates into ELF and AM to levels approximately 40-fold and 20-fold, respectively, higher than free-drug exposures in plasma.

The clinical significance of vancomycin minimum inhibitory concentration in Staphylococcus aureus infections: a systematic review and meta-analysis

BACKGROUND

Emerging data suggest that vancomycin may be less effective against serious methicillin-resistant Staphylococcus aureus (MRSA) infections with minimum inhibitory concentration (MIC) values at the higher end of the susceptibility range. The purpose of this review is to examine the strength of these associations.

METHODS

All relevant studies pertaining to treatment outcomes or mortality associated with vancomycin MIC were retrieved from the medical literature from January 1996 through August 2011 and analyzed according to Cochrane guidelines.

RESULTS

Of the 270 studies identified, 48 studies were reviewed, with 22 studies included in the final meta-analysis. Vancomycin MIC was significantly associated with mortality for MRSA infection irrespective of the source of infection or MIC methodology (odds ratio [OR], 1.64; 95% confidence interval [CI], 1.14-2.37; P < .01). This mortality association was predominantly driven by bloodstream infections (BSIs; OR, 1.58; 95% CI, 1.06-2.37; P = .03) and isolates with a vancomycin MIC of 2 μg/mL by Etest (OR, 1.72; 95% CI, 1.34-2.21; P < .01). Vancomycin MIC was significantly associated with treatment failure irrespective of source of infection or MIC methodology (OR, 2.69; 95% CI, 1.60-4.51; P < .01).

CONCLUSION

High vancomycin MIC was associated with a higher mortality rate in MRSA BSI. Thus, institutions should consider conducting Etest MICs on all MRSA BSI isolates. Although these data highlight concerns about vancomycin, currently, there are no data to support better survival rates with alternative antibiotics. Data are sorely needed to determine whether other agents can remedy these outcomes observed with vancomycin for MRSA infections with elevated vancomycin MIC values.

Reduced vancomycin susceptibility among clinical Staphylococcus aureus isolates ('the MIC Creep'): implications for therapy

Methicillin-resistant S. aureus (MRSA) has emerged as the most common hospital-acquired pathogen and is associated with increased morbidity and mortality compared with other strains. Vancomycin has been the cornerstone of treatment of patients with serious MRSA infections for some decades and while more than 99% of clinical S. aureus isolates remain susceptible to vancomycin, we are beginning to see strains of MRSA with reduced susceptibility. This review discusses this phenomenon, the predictors of infection with such forms of MRSA, and current and future management options.

Staphylococcal decolonisation: an effective strategy for prevention of infection?

Staphylococcus aureus decolonisation--treatment to eradicate staphylococcal carriage--is often considered as a measure to prevent S aureus infection. The most common approach to decolonisation has been intranasal application of mupirocin either alone or in combination with antiseptic soaps or systemic antimicrobial agents. Some data support the use of decolonisation in surgical patients colonised with S aureus, particularly in those undergoing cardiothoracic procedures. Although this intervention has been associated with low rates of postoperative S aureus infection, whether overall rates of infection are also decreased is unclear. Patients undergoing chronic haemodialysis or peritoneal dialysis might benefit from decolonisation, although repeated courses of treatment are needed, and the effects are modest. Eradication of meticillin-resistant S aureus (MRSA) carriage has generally been difficult, and the role of decolonisation as an MRSA infection control measure is uncertain. The efficacy of decolonisation of patients with community-associated MRSA has not been established, and the routine use of decolonisation of non-surgical patients is not supported by data.

Revisiting "older" antimicrobials in the era of multidrug resistance

Infections due to multidrug-resistant (MDR) organisms continue to increase, and the antimicrobial pipeline remains unacceptably lean. Given this challenge, it is has become necessary to use older antimicrobials for treatment of MDR pathogens despite concerns regarding toxicity and the lack of clinical efficacy data. In some cases, older antimicrobials offer potential advantages compared with new agents, including lower cost and better in vitro activity. In this review, we focus on the pharmacology, in vitro activity, and clinical experience of older agents, including colistin, minocycline, trimethoprim-sulfamethoxazole, and fosfomycin. We also discuss some new antimicrobial agents that are used to treat MDR pathogens. As MDR pathogens continue to outpace the development of new antimicrobials, it will become imperative to develop strategies regarding the optimal use of older agents in terms of monotherapy versus combination therapy, dosing regimens, and treatment of invasive infections caused by these pathogens.

Spread of epidemic MRSA-ST5-IV clone encoding PVL as a major cause of community onset staphylococcal infections in Argentinean children

BACKGROUND

Community-associated methicillin-resistant Staphylococcus aureus-(CA-MRSA) strains have emerged in Argentina. We investigated the clinical and molecular evolution of community-onset MRSA infections (CO-MRSA) in children of Córdoba, Argentina, 2005-2008. Additionally, data from 2007 were compared with the epidemiology of these infections in other regions of the country.

METHODOLOGY/PRINCIPAL FINDINGS

Two datasets were used: i) lab-based prospective surveillance of CA-MRSA isolates from 3 Córdoba pediatric hospitals-(CBAH1-H3) in 2007-2008 (compared to previously published data of 2005) and ii) a sampling of CO-MRSA from a study involving both, healthcare-associated community-onset-(HACO) infections in children with risk-factors for healthcare-associated infections-(HRFs), and CA-MRSA infections in patients without HRFs detected in multiple centers of Argentina in 2007. Molecular typing was performed on the CA-MRSA-(n: 99) isolates from the CBAH1-H3-dataset and on the HACO-MRSA-(n: 51) and CA-MRSA-(n: 213) isolates from other regions. Between 2005-2008, the annual proportion of CA-MRSA/CA-S. aureus in Córdoba hospitals increased from 25% to 49%, P<0.01. Total CA-MRSA infections increased 3.6 fold-(5.1 to 18.6 cases/100,000 annual-visits, P<0.0001), associated with an important increase of invasive CA-MRSA infections-(8.5 fold). In all regions analyzed, a single genotype prevailed in both CA-MRSA (82%) and HACO-MRSA(57%), which showed pulsed-field-gel electrophoresis-(PFGE)-type-"I", sequence-type-5-(ST5), SCCmec-type-IVa, spa-t311, and was positive for PVL. The second clone, pulsotype-N/ST30/CC30/SCCmecIVc/t019/PVL(+), accounted for 11.5% of total CA-MRSA infections. Importantly, the first 4 isolates of Argentina belonging to South American-USA300 clone-(USA300/ST8/CC8/SCCmecIVc/t008/PVL(+)/ACME(-)) were detected. We also demonstrated that a HA-MRSA clone-(pulsotype-C/ST100/CC5) caused 2% and 10% of CA-MRSA and HACO-MRSA infections respectively and was associated with a SCCmec type closely related to SCCmecIV(2B&5).

CONCLUSIONS/SIGNIFICANCE

The dissemination of epidemic MRSA clone, ST5-IV-PVL(+) was the main cause of increasing staphylococcal community-onset infections in Argentinean children (2003-2008), conversely to other countries. The predominance of this clone, which has capacity to express the h-VISA phenotype, in healthcare-associated community-onset cases suggests that it has infiltrated into hospital-settings.

[Infective endocarditis in the XXI century: epidemiological, therapeutic, and prognosis changes]

Infective endocarditis (IE) is an uncommon and severe disease. Nowadays, in developed countries, IE patients are older, usually have a degenerative heart valve disease, and up to 30% acquire this infection within the health care system. In consequence, staphylococci species are the most frequently isolated microorganisms. Antimicrobial treatment for IE has significantly changed over the last decades. In IE episodes due to Staphylococcus aureus, cloxacillin-resistance makes antimicrobial election more difficult. Other microorganisms, such as enterococci and some species of streptococci, show high rates of resistance to antimicrobial agents established in guidelines. Despite improvements in the diagnosis, and medical and surgical treatment of IE, this disease continues to be associated with high rates of in-hospital mortality. At present, due to epidemiological changes, antimicrobial prophylaxis can avoid few cases of IE. Prevention of nosocomial bacteremia, an early diagnosis of IE, prompt identification of IE patients at a higher risk of mortality, and a multidisciplinary approach of this disease could be valid strategies in order to improve the outcome of these patients.

Bacterial skin and soft tissue infections: review of the epidemiology, microbiology, aetiopathogenesis and treatment: a collaboration between dermatologists and infectivologists

Bacterial skin and soft tissues infections (SSTI) often determine acute disease and frequent emergency recovering, and they are one of the most common causes of infection among groups of different ages. Given the variable presentation of SSTI, a thorough assessment of their incidence and prevalence is difficult. The presence of patient-related (local or systemic) or environmental risk factors, along with the emergence of multi-drug resistant pathogens, can promote SSTI. These infections may present with a wide spectrum of clinical features and different severity, and can be classified according to various criteria. Many bacterial species can cause SSTI, but Gram-positive bacteria are the most frequently isolated, with a predominance of Staphylococcus aureus and Streptococcus pyogenes. The diagnosis of SSTI requires an extended clinical history, a thorough physical examination and a high index of suspicion. Early diagnosis is particularly important in complicated infections, which often require laboratory studies, diagnostic imaging and surgical exploration. SSTI management should conform to the epidemiology, the aetiology, the severity and the depth of the infection. Topical, oral or systemic antimicrobial therapy and drainage or debridement could be necessary, along with treatment of a significant underlying disease. This review discusses the epidemiology, the pathogenesis and the classification of bacterial SSTI, describes their associated risk factors and their clinical presentations. The authors provide a rational diagnostic and therapeutic approach to SSTI in respect of antibiotic resistance and currently available antimicrobial agents.

Antimicrobial de-escalation strategies in hospitalized patients with pneumonia, intra-abdominal infections, and bacteremia

Increasing numbers of serious hospital/healthcare- or community-acquired infections are caused by resistant (often multi-drug resistant) bacterial pathogens. Because delayed or ineffective initial therapy can have severe negative consequences, patients at risk for these types of infections typically receive initial empiric antibiotic therapy with a broad-spectrum regimen covering the most likely pathogens, based on local surveillance data and risk factors for infection with a resistant microorganism. While improving the likelihood of a successful outcome, use of broad-spectrum, often high-dose, empiric antimicrobial therapy also creates pressure for the selection or development of resistant microorganisms, as well as increasing costs and possibly exposing patients to adverse events or collateral damage such as Clostridium difficile-associated disease. De-escalation is a strategy that attempts to balance the competing aims of providing initial empiric therapy that is appropriate and covers the likely pathogens, and limiting antimicrobial exposure and increased risk for emergence of resistant pathogens. More specifically, the de-escalation strategy involves collection of cultures for later microbiological assessment before initiating broad-spectrum empiric therapy covering the most likely pathogens, with the intention of streamlining or de-escalating to a more narrow-spectrum antimicrobial regimen 2-3 days later if warranted by clinical status and culture results. In some cases, negative culture results and subsequent clinical review may allow for termination of initial empiric therapy. In this manner, de-escalation enables more effective targeting of the causative pathogen(s), elimination of redundant therapy, a decrease in antimicrobial pressure for emergence of resistance, and cost savings. This article examines application of the de-escalation strategy to 3 case patients, one with healthcare-associated pneumonia, another with complicated intra-abdominal infection, and a third with central line-associated bacteremia.

Methicillin-resistant Staphylococcus aureus meningitis in adults: a multicenter study of 86 cases

Methicillin-resistant Staphylococcus aureus (MRSA) meningitis is an uncommon disease, and little is known about its epidemiology, clinical features, therapy, and outcome. We performed a multicenter retrospective study of MRSA meningitis in adults. Eighty-six adult patients were included and the following data were obtained: underlying diseases, clinical presentation, analytical and microbiologic data, response to therapy, and outcome.There were 56 men (65%) and the mean age was 51.5 years; 54 of them (63%) had severe comorbidities. There were 78 cases of postoperative meningitis and 8 of spontaneous meningitis. The infection was nosocomial in 93% (80/86) of the cases. Among the 78 patients with postoperative meningitis, the most common predisposing conditions were cerebrospinal fluid (CSF) devices (74%), neurosurgery (45%), CSF leakage (17%), and head trauma (12%). Most patients had fever (89%), altered mental status (68%), headache (40%), and meningeal signs (29%). The most common CSF findings were pleocytosis (90%), elevated protein level (77%), and hypoglycorrhachia (30%). CSF Gram stain and blood cultures were positive in 49% (32/65) and 36% (16/45) of cases, respectively. An associated MRSA infection and polymicrobial meningitis appeared in 33% (28/86) and 23% (20/86) of cases, respectively. Antimicrobial therapy was given to 84 patients. Most of them received vancomycin (92%) either as monotherapy (64%) or in combination with other antibiotics (28%), for a median of 18 days. Overall 30-day mortality was 31% (27/86). Multivariate study identified 2 independent factors associated with mortality: spontaneous meningitis (odds ratio [OR], 21.4; 95% confidence interval [CI], 2.3-195.4; p = 0.007), and coma (OR, 9.7; 95% CI, 2.2-42.3; p = 0.002).In conclusion, MRSA is a relatively uncommon but serious disease. Although most cases are nosocomial infections appearing in neurosurgical patients, spontaneous meningitis may present as a community-onset infection in patients with severe comorbidities requiring frequent contact with the health care system. Most patients have a favorable response to vancomycin, but the beneficial effect of combined and intraventricular therapy, or alternative drugs, remains unclear. MRSA meningitis is associated with a high mortality, and the presence of spontaneous infection and coma are the most important prognostic factors.

New insights into meticillin-resistant Staphylococcus aureus (MRSA) pathogenesis, treatment and resistance

Meticillin-resistant Staphylococcus aureus (MRSA) remains one of the principal multiply resistant bacterial pathogens causing serious healthcare-associated and community-onset infections. This paper reviews recent studies that have elucidated the virulence strategies employed by MRSA, key clinical trials of agents used to treat serious MRSA infections, and accumulating data regarding the implications of antibacterial resistance in MRSA for clinical success during therapy. Recent pre-clinical data support a species-specific role for Panton-Valentine leukocidin in the development of acute severe S. aureus infections and have elucidated other virulence mechanisms, including novel modes of internalisation, varying post-invasion strategies (featuring both upregulation and downregulation of virulence factors) and phenotypic switching. Recent double-blind, randomised, phase III/IV clinical trials have demonstrated the efficacy of linezolid and telavancin in hospital-acquired pneumonia (HAP) and complicated skin and skin-structure infections (cSSSIs) caused by MRSA. Tigecycline was non-inferior to imipenem/cilastatin in non-ventilator-associated HAP but was inferior in ventilator-associated pneumonia and has shown a higher rate of death than comparators on meta-analysis. Ceftaroline was clinically and microbiologically non-inferior to vancomycin/aztreonam in the treatment of MRSA cSSSI. Key resistance issues include a rise in vancomycin minimum inhibitory concentrations in MRSA, reports of clonal isolates with linezolid resistance mediated by acquisition of the chloramphenicol/florfenicol resistance gene, and case reports of daptomycin resistance resulting in clinical failure. Novel antimicrobial targets must be identified with some regularity or we will face the risk of untreatable S. aureus infections.

Prior vancomycin use is a risk factor for reduced vancomycin susceptibility in methicillin-susceptible but not methicillin-resistant Staphylococcus aureus bacteremia

OBJECTIVE

Staphylococcus aureus is a cause of community- and healthcare-acquired infections and is associated with substantial morbidity, mortality, and costs. Vancomycin minimum inhibitory concentrations (MICs) among S. aureus have increased, and reduced vancomycin susceptibility (RVS) may be associated with treatment failure. We aimed to identify clinical risk factors for RVS in S. aureus bacteremia.

DESIGN

Case-control.

SETTING

Academic tertiary care medical center and affiliated urban community hospital.

PATIENTS

Cases were patients with RVS S. aureus isolates (defined as vancomycin E-test MIC >1.0 μg/mL). Controls were patients with non-RVS S. aureus isolates.

RESULTS

Of 392 subjects, 134 (34.2%) had RVS. Fifty-eight of 202 patients (28.7%) with methicillin-susceptible S. aureus (MSSA) isolates had RVS, and 76 of 190 patients (40.0%) with methicillin-resistant S. aureus (MRSA) isolates had RVS (P = .02). In unadjusted analyses, prior vancomycin use was associated with RVS (odds ratio [OR], 2.08; 95% confidence interval [CI], 1.00-4.32; P = .046). In stratified analyses, there was significant effect modification by methicillin susceptibility on the association between vancomycin use and RVS (P =.04). In multivariable analyses, after hospital of admission and prior levofloxacin use were controlled for, the association between vancomycin use and RVS was significant for patients with MSSA infection (adjusted OR, 4.02; 95% CI, 1.11-14.50) but not MRSA infection (adjusted OR, 0.87; 95% CI, 0.36-2.13).

CONCLUSIONS

A substantial proportion of patients with S. aureus bacteremia had RVS. The association between prior vancomycin use and RVS was significant for patients with MSSA infection but not MRSA infection, suggesting a complex relationship between the clinical and molecular epidemiology of RVS in S. aureus.

Cellulitis: definition, etiology, and clinical features

Cellulitis is a common condition seen by physicians. Over the past decade, skin and soft tissue infections from community-associated methicillin-resistant Staphylococcus aureus have become increasingly common. In this article, the definition, etiology, and clinical features of cellulitis are reviewed, and the importance of differentiating cellulitis from necrotizing soft tissue infections is emphasized. Empiric antimicrobial recommendations are suggested, including the most recent recommendations from the Infectious Disease Society of America.

Critically ill children during the 2009-2010 influenza pandemic in the United States

BACKGROUND

The 2009 pandemic influenza A (H1N1) (pH1N1) virus continues to circulate worldwide. Determining the roles of chronic conditions and bacterial coinfection in mortality is difficult because of the limited data for children with pH1N1-related critical illness.

METHODS

We identified children (<21 years old) with confirmed or probable pH1N1 admitted to 35 US PICUs from April 15, 2009, through April 15, 2010. We collected data on demographics, baseline health, laboratory results, treatments, and outcomes.

RESULTS

Of 838 children with pH1N1 admitted to a PICU, the median age was 6 years, 58% were male, 70% had ≥1 chronic health condition, and 88.2% received oseltamivir (5.8% started before PICU admission). Most patients had respiratory failure with 564 (67.3%) receiving mechanical ventilation; 162 (19.3%) received vasopressors, and 75 (8.9%) died. Overall, 71 (8.5%) of the patients had a presumed diagnosis of early (within 72 hours after PICU admission) Staphylococcus aureus coinfection of the lung with 48% methicillin-resistant S aureus (MRSA). In multivariable analyses, preexisting neurologic conditions or immunosuppression, encephalitis (1.7% of cases), myocarditis (1.4% of cases), early presumed MRSA lung coinfection, and female gender were mortality risk factors. Among 251 previously healthy children, only early presumed MRSA coinfection of the lung (relative risk: 8 [95% confidence interval: 3.1-20.6]; P < .0001) remained a mortality risk factor.

CONCLUSIONS

Children with preexisting neurologic conditions and immune compromise were at increased risk of pH1N1-associated death after PICU admission. Secondary complications of pH1N1, including myocarditis, encephalitis, and clinical diagnosis of early presumed MRSA coinfection of the lung, were mortality risk factors.

Antibiotic prescribing in ambulatory pediatrics in the United States

BACKGROUND

Antibiotics are commonly prescribed for children with conditions for which they provide no benefit, including viral respiratory infections. Broad-spectrum antibiotic use is increasing, which adds unnecessary cost and promotes the development of antibiotic resistance.

OBJECTIVE

To provide a nationally representative analysis of antibiotic prescribing in ambulatory pediatrics according to antibiotic classes and diagnostic categories and identify factors associated with broad-spectrum antibiotic prescribing.

PATIENTS AND METHODS

We used the National Ambulatory and National Hospital Ambulatory Medical Care surveys from 2006 to 2008, which are nationally representative samples of ambulatory care visits in the United States. We estimated the percentage of visits for patients younger than 18 years for whom antibiotics were prescribed according to antibiotic classes, those considered broad-spectrum, and diagnostic categories. We used multivariable logistic regression to identify demographic and clinical factors that were independently associated with broad-spectrum antibiotic prescribing.

RESULTS

Antibiotics were prescribed during 21% of pediatric ambulatory visits; 50% were broad-spectrum, most commonly macrolides. Respiratory conditions accounted for >70% of visits in which both antibiotics and broad-spectrum antibiotics were prescribed. Twenty-three percent of the visits in which antibiotics were prescribed were for respiratory conditions for which antibiotics are not clearly indicated, which accounts for >10 million visits annually. Factors independently associated with broad-spectrum antibiotic prescribing included respiratory conditions for which antibiotics are not indicated, younger patients, visits in the South, and private insurance.

CONCLUSIONS

Broad-spectrum antibiotic prescribing in ambulatory pediatrics is extremely common and frequently inappropriate. These findings can inform the development and implementation of antibiotic stewardship efforts in ambulatory care toward the most important geographic regions, diagnostic conditions, and patient populations.

Current concepts in antimicrobial therapy against select gram-positive organisms: methicillin-resistant Staphylococcus aureus, penicillin-resistant pneumococci, and vancomycin-resistant enterococci

Gram-positive bacteria cause a broad spectrum of disease in immunocompetent and immunocompromised hosts. Despite increasing knowledge about resistance transmission patterns and new antibiotics, these organisms continue to cause significant morbidity and mortality, especially in the health care setting. Methicillin-resistant Staphylococcus aureus poses major problems worldwide as a cause of nosocomial infection and has emerged as a cause of community-acquired infections. This change in epidemiology affects choices of empirical antibiotics for skin and skin-structure infections and community-acquired pneumonia in many settings. Throughout the world, the treatment of community-acquired pneumonia and other respiratory tract infections caused by penicillin-resistant Streptococcus pneumoniae has been complicated by resistance to β-lactam and macrolide antibacterial drugs. Vancomycin-resistant enterococci are a major cause of infection in the hospital setting and remain resistant to treatment with most standard antibiotics. Treatment of diseases caused by resistant gram-positive bacteria requires appropriate use of available antibiotics and stewardship to prolong their effectiveness. In addition, appropriate and aggressive infection control efforts are vital to help prevent the spread of resistant pathogens.

Evaluation of telavancin activity versus daptomycin and vancomycin against daptomycin-nonsusceptible Staphylococcus aureus in an in vitro pharmacokinetic/pharmacodynamic model

Daptomycin-nonsusceptible (DNS) Staphylococcus aureus strains have been reported over the last several years. Telavancin is a lipoglycopeptide with a dual mechanism of action, as it inhibits peptidoglycan polymerization/cross-linking and disrupts the membrane potential. Three clinical DNS S. aureus strains, CB1814, R6212, and SA-684, were evaluated in an in vitro pharmacokinetic/pharmacodynamic (PK/PD) model with simulated endocardial vegetations (starting inoculum, 10(8.5) CFU/g) for 120 h. Simulated regimens included telavancin at 10 mg/kg every 24 h (q24h; peak, 87.5 mg/liter; t(1/2), 7.5 h), daptomycin at 6 mg/kg q24h (peak, 95.7 mg/liter; t(1/2), 8 h), and vancomycin at 1 g q12h (peak, 30 mg/liter; t(1/2), 6 h). Differences in CFU/g between regimens at 24 through 120 h were evaluated by analysis of variance with a Tukey's post hoc test. Bactericidal activity was defined as a ≥3-log(10) CFU/g decrease in colony count from the initial inoculum. MIC values were 1, 0.25, and 0.5 mg/liter (telavancin), 4, 2, and 2 mg/liter (daptomycin), and 2, 2, and 2 mg/liter (vancomycin) for CB1814, R6212, and SA-684, respectively. Telavancin displayed bactericidal activities against R6212 (32 to 120 h; -4.31 log(10) CFU/g), SA-684 (56 to 120 h; -3.06 log(10) CFU/g), and CB1814 (48 to 120 h; -4.9 log(10) CFU/g). Daptomycin displayed initial bactericidal activity followed by regrowth with all three strains. Vancomycin did not exhibit sustained bactericidal activity against any strain. At 120 h, telavancin was significantly better at reducing colony counts than vancomycin against all three tested strains and better than daptomycin against CB1814 (P < 0.05). Telavancin displayed bactericidal activity in vitro against DNS S. aureus isolates.

Duration of antibiotic therapy for bacteremia: a systematic review and meta-analysis

Introduction

The optimal duration of antibiotic therapy for bloodstream infections is unknown. Shorter durations of therapy have been demonstrated to be as effective as longer durations for many common infections; similar findings in bacteremia could enable hospitals to reduce antibiotic utilization, adverse events, resistance and costs.

Methods

A search of the MEDLINE, EMBASE and COCHRANE databases was conducted for the years 1947-2010. Controlled trials were identified that randomized patients to shorter versus longer durations of treatment for bacteremia, or the infectious foci most commonly causing bacteremia in critically ill patients (catheter-related bloodstream infections (CRBSI), intra-abdominal infections, pneumonia, pyelonephritis and skin and soft-tissue infections (SSTI)).

Results

Twenty-four eligible trials were identified, including one trial focusing exclusively on bacteremia, zero in catheter related bloodstream infection, three in intra-abdominal infection, six in pyelonephritis, thirteen in pneumonia and one in skin and soft tissue infection. Thirteen studies reported on 227 patients with bacteremia allocated to 'shorter' or 'longer' durations of treatment. Outcome data were available for 155 bacteremic patients: neonatal bacteremia (n = 66); intra-abdominal infection (40); pyelonephritis (9); and pneumonia (40). Among bacteremic patients receiving shorter (5-7 days) versus longer (7-21 days) antibiotic therapy, no significant difference was detected with respect to rates of clinical cure (45/52 versus 47/49, risk ratio 0.88, 95% confidence interval [CI] 0.77-1.01), microbiologic cure (28/28 versus 30/32, risk ratio 1.05, 95% CI 0.91-1.21), and survival (15/17 versus 26/29, risk ratio 0.97, 95% CI 0.76-1.23).

Conclusions

No significant differences in clinical cure, microbiologic cure and survival were detected among bacteremic patients receiving shorter versus longer duration antibiotic therapy. An adequately powered randomized trial of bacteremic patients is needed to confirm these findings.

A systematic review of bacteremias in cellulitis and erysipelas

OBJECTIVES

Because of the difficulty of obtaining bacterial cultures from patients with cellulitis and erysipelas, the microbiology of these common infections remains incompletely defined. Given the emergence of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) over the past decade the proportion of infections due to S. aureus has become particularly relevant.

METHODS

OVID was used to search Medline using the focused subject headings "cellulitis", "erysipelas" and "soft tissue infections". All references that involved adult patients with cellulitis or erysipelas and reported associated bacteremias and specific pathogens were included in the review.

RESULTS

For erysipelas, 4.6% of 607 patients had positive blood cultures, of which 46% were Streptococcus pyogenes, 29% were other β-hemolytic streptococci, 14% were Staphylococcus aureus, and 11% were Gram-negative organisms. For cellulitis, 7.9% of 1578 patients had positive blood cultures of which 19% were Streptococcus pyogenes, 38% were other β-hemolytic streptococci, 14% were Staphylococcus aureus, and 28% were Gram-negative organisms.

CONCLUSIONS

Although the strength of our conclusions are somewhat limited by the heterogeneity of included cases, our results support the traditional view that cellulitis and erysipelas are primarily due to streptococcal species, with a smaller proportion due to S. aureus. Our results also argue against the current distinction between cellulitis and erysipelas in terms of the relative proportion of infections due to S. aureus.

Antibiotic therapy in neonatal and pediatric septic shock

Severe sepsis accounts for nearly 4,500 deaths (mortality rate 10%), and is responsible for nearly $2 billion annual healthcare expenditure in the United States. Early and speedy treatment of critically ill septic patients can halt or reduce the likelihood of physiologic progression to multi-system organ failure. A cornerstone of this therapeutic strategy is antibiotic administration. In this review, we discuss the empirical treatment strategies for the treatment of early and late neonatal sepsis, along with pediatric sepsis. Furthermore, we discuss the rationale that underlies the adoption of such treatment strategies. The present article also discusses the emergence of multi-drug organisms as the causative agents for sepsis, i.e. methicillin-resistant Staphylococcus aureus (MRSA), resistant enterococci and Klebsiella pneumoniae carbapenemases (KPC).

Simulated antibiotic exposures in an in vitro hollow-fiber infection model influence toxin gene expression and production in community-associated methicillin-resistant Staphylococcus aureus strain MW2

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) strain MW2 harbors a plethora of toxins to mediate its virulence. However, toxin expression and regulation with simulated clinical antimicrobial exposures are unclear. This study evaluated these relationships using an in vitro pharmacodynamic hollow-fiber infection model. Clinical doses of clindamycin, linezolid, minocycline, trimethoprim-sulfamethoxazole (SXT), and vancomycin were simulated over 72 h against MW2 in the hollow fiber model. Expression levels of lukSF-PV and enterotoxin genes sec4, sek, seq, and sel2 were quantified by real-time PCR. Panton-Valentine leukocidin (PVL) was quantified by enzyme-linked immunosorbent assay (ELISA), and cytotoxicity was determined on polymorphonuclear cells (PMNs). Vancomycin produced the maximum MW2 killing (2.53 log(10) CFU/ml) after the first dose, but the greatest sustained killing over 72 h occurred with linezolid and clindamycin. Vancomycin and minocycline induced gene upregulation from 0 to 8 h, followed by downregulation for the remaining simulation period. Clindamycin decreased gene expression in the first 24 h, followed by moderate increases (2.5-fold) thereafter. Linezolid increased gene expression 11.4- to 200.4-fold but inhibited PVL production (0.6 ± 0.3 versus 5.9 ± 0.2 μg/ml, linezolid versus control at 72 h; P < 0.05). Similar effects on PVL production occurred with clindamycin and minocycline. SXT increased PVL production at 48 h (2.8-fold) and 72 h (4.9-fold) of treatment (P < 0.05), resulting in increased PVL cytotoxicity on PMNs. Linezolid, clindamycin, and minocycline were the most effective agents on decreasing the virulence potential in CA-MRSA, notably after 8 h of treatment. SXT had minimal effects on toxin gene regulation, but it increased production and cytotoxicity of PVL toxin in the model and may enhance virulence when it is used to treat severe infections.

Innate and adaptive immune responses against Staphylococcus aureus skin infections

Staphylococcus aureus is an important human pathogen that is responsible for the vast majority of bacterial skin and soft tissue infections in humans. S. aureus can also become more invasive and cause life-threatening infections such as bacteremia, pneumonia, abscesses of various organs, meningitis, osteomyelitis, endocarditis, and sepsis. These infections represent a major public health threat due to the enormous numbers of these infections and the widespread emergence of methicillin-resistant S. aureus (MRSA) strains. MSRA is endemic in hospitals worldwide and is rapidly spreading throughout the normal human population in the community. The increasing frequency of MRSA infections has complicated treatment as these strains are more virulent and are increasingly becoming resistant to multiple different classes of antibiotics. The important role of the immune response against S. aureus infections cannot be overemphasized as humans with certain genetic and acquired immunodeficiency disorders are at an increased risk for infection. Understanding the cutaneous immune responses against S. aureus is essential as most of these infections occur or originate from a site of infection or colonization of the skin and mucosa. This review will summarize the innate immune responses against S. aureus skin infections, including antimicrobial peptides that have direct antimicrobial activity against S. aureus as well as pattern recognition receptors and proinflammatory cytokines that promote neutrophil abscess formation in the skin, which is required for bacterial clearance. Finally, we will discuss the recent discoveries involving IL-17-mediated responses, which provide a key link between cutaneous innate and adaptive immune responses against S. aureus skin infections.

Community-associated methicillin-resistant Staphylococcus aureus causing orbital cellulitis in Australian children

Community-associated methicillin-resistant Staphylococcus aureus has only emerged recently as a cause of serious ocular infections in several different countries. At a tertiary pediatric hospital in Brisbane, Australia, community-associated methicillin-resistant S. aureus orbital cellulitis was first noted in 2009. Since then, it has caused 4 of 9 such infections.

Continuous versus intermittent infusion of vancomycin for the treatment of Gram-positive infections: systematic review and meta-analysis

OBJECTIVES

To summarize available evidence on the effect of continuous infusion (CoI) of vancomycin compared with intermittent infusion (InI) in adult patients with Gram-positive infections.

METHODS

MEDLINE, EMBASE and Cochrane databases were searched. Randomized clinical trials (RCTs) and observational studies that comparatively assessed CoI and InI of vancomycin in terms of mortality, clinical cure, toxicity rates and serum drug exposure [trough concentration (C(min)) for InI and steady-state concentration (C(ss)) for CoI; area under the curve at 24 h (AUC(24)) for both] were included. Meta-analysis was conducted combining and analysing the relative risk (RR) and computing a summary RR of the effects with 95% confidence interval (CI). The standardized mean difference was calculated for continuous outcomes. The I(2) test was calculated to assess heterogeneity across studies.

RESULTS

One RCT and five observational studies were included in the analysis. Compared with InI, CoI of vancomycin was associated with a significantly lower risk of nephrotoxicity (RR 0.6, 95% CI 0.4-0.9, P = 0.02; I(2)= 0). Overall mortality was not different between the two groups (RR 1.03, 95% CI 0.7-1.6, P = 0.9; I(2)= 0).

CONCLUSIONS

Our meta-analysis suggests that administration of vancomycin for the treatment of Gram-positive infections by CoI is associated with a significantly lower risk of nephrotoxicity when compared with InI of the drug. RCTs are needed to define the impact on mortality rate and on the pharmacodynamic activity in terms of AUC/MIC ratio.

Comparative effectiveness of nafcillin or cefazolin versus vancomycin in methicillin-susceptible Staphylococcus aureus bacteremia

Background

The high prevalence of methicillin-resistant S. aureus (MRSA) has led clinicians to select antibiotics that have coverage against MRSA, usually vancomycin, for empiric therapy for suspected staphylococcal infections. Clinicians often continue vancomycin started empirically even when methicillin-susceptible S. aureus (MSSA) strains are identified by culture. However, vancomycin has been associated with poor outcomes such as nephrotoxicity, persistent bacteremia and treatment failure. The objective of this study was to compare the effectiveness of vancomycin versus the beta-lactam antibiotics nafcillin and cefazolin among patients with MSSA bacteremia. The outcome of interest for this study was 30-day in-hospital mortality.

Methods

This retrospective cohort study included all adult in-patients admitted to a tertiary-care facility between January 1, 2003 and June 30, 2007 who had a positive blood culture for MSSA and received nafcillin, cefazolin or vancomycin. Cox proportional hazard models were used to assess independent mortality hazards comparing nafcillin or cefazolin versus vancomycin. Similar methods were used to estimate the survival benefits of switching from vancomycin to nafcillin or cefazolin versus leaving patients on vancomycin. Each model included statistical adjustment using propensity scores which contained variables associated with an increased propensity to receive vancomycin.

Results

267 patients were included; 14% (38/267) received nafcillin or cefazolin, 51% (135/267) received both vancomycin and either nafcillin or cefazolin, and 35% (94/267) received vancomycin. Thirty (11%) died within 30 days. Those receiving nafcillin or cefazolin had 79% lower mortality hazards compared with those who received vancomycin alone (adjusted hazard ratio (HR): 0.21; 95% confidence interval (CI): 0.09, 0.47). Among the 122 patients who initially received vancomycin empirically, those who were switched to nafcillin or cefazolin (66/122) had 69% lower mortality hazards (adjusted HR: 0.31; 95% CI: 0.10, 0.95) compared to those who remained on vancomycin.

Conclusions

Receipt of nafcillin or cefazolin was protective against mortality compared to vancomycin even when therapy was altered after culture results identified MSSA. Convenience of vancomycin dosing may not outweigh the potential benefits of nafcillin or cefazolin in the treatment of MSSA bacteremia.

Antibacterial resistance, genes encoding toxins and genetic background among Staphylococcus aureus isolated from community-acquired skin and soft tissue infections in France: a national prospective survey

The epidemiology of staphylococcal community-acquired skin and soft tissues infections (CA-SSTIs) has changed dramatically. We described prospectively the characteristics of the Staphylococcus aureus isolated from 71 non-teaching French hospitals and implicated in CA-SSTIs: antimicrobial susceptibility (mecA polymerase chain reaction [PCR], disk diffusion method), virulence factor gene (sea, tst, pvl) prevalence and genetic background (agr allele). During November 2006, 235 strains were collected (wound infection: 51%, abscess: 21%, whitlow: 8%, diabetic foot: 7%, furunculosis: 3%). sea, tst and pvl were identified in 22.1, 13.2 and 8.9% strains, respectively. agr allele 1 was the most frequently encountered genetic background, whatever the methicillin susceptibility. Among the 34 methicillin-resistant S. aureus (MRSA, 14.5% of all S. aureus), only one strain (2.9%) harboured pvl (belonging to the European ST80 clone), four (11.8%) tst (belonging to two endemic French clones) and 18 (52.9%) sea gene (mainly the Lyon clone). According to their in vitro activity, pristinamycin or trimethoprim/sulfamethoxazole could be considered as first-choice antibiotics. To date, the international pvl-positive MRSA clones have not spread in France. MRSA strains isolated from putative CA-SSTIs exhibited a genetic and phenotypic background of hospital-acquired (HA) clones. National survey should be continued, in order to monitor the emergence of virulent clones.

Use of a simple criteria set for guiding echocardiography in nosocomial Staphylococcus aureus bacteremia

BACKGROUND

Infective endocarditis (IE) is a severe complication in patients with nosocomial Staphylococcus aureus bacteremia (SAB). We sought to develop and validate criteria to identify patients at low risk for the development of IE in whom transesophageal echocardiography (TEE) might be dispensable.

METHODS

Consecutive patients with nosocomial SAB from independent cohorts in Europe (Invasive S. aureus Infection Cohort [INSTINCT]) and North America (S. aureus Bacteremia Group [SABG]) were evaluated for the presence of clinical criteria predicting an increased risk for the development of IE (ie, prolonged bacteremia of >4 days' duration, presence of a permanent intracardiac device, hemodialysis dependency, spinal infection, and nonvertebral osteomyelitis). Patients were observed closely for clinical signs and symptoms of IE during hospitalization and a 3-month follow-up period.

RESULTS

IE was present in 13 (4.3%) of 304 patients in the INSTINCT cohort and in 40 (9.3%) of 432 patients in the SABG cohort. Within 14 days after the first positive blood culture result, echocardiography was performed in 39.8% and 57.4% of patients in the INSTINCT and SABG cohorts, respectively. In patients with IE, the most common clinical prediction criteria present were prolonged bacteremia (69.2% vs 90% for INSTINCT vs SABG, respectively) and presence of a permanent intracardiac device (53.8% vs 32.5%). In total, 13 of 13 patients in the INSTINCT cohort and 39 of 40 patients in the SABG cohort with documented IE fulfilled at least 1 criterion (sensitivity, 100% vs. 97.5%; negative predictive value, 100% vs 99.2%).

CONCLUSIONS

A simple criteria set for patients with nosocomial SAB can identify patients at low risk of IE. Patients who meet these criteria may not routinely require TEE.

Detection of Staphylococcus aureus isolates with heterogeneous intermediate-level resistance to vancomycin in the United States

The prevalence of heterogeneous intermediate-level resistance to vancomycin (hVISA) in Staphylococcus aureus was assessed by screening a large collection of recent isolates. Susceptibility testing by the Clinical and Laboratory Standards Institute broth microdilution method and the Etest GRD (glycopeptide resistance detection) method (bioMérieux) was performed on 4,210 clinically significant S. aureus isolates obtained in 2009 from 43 U.S. centers. Isolates with Etest GRD-positive results for hVISA were evaluated further by repeat GRD testing and population analysis profiling-area under the curve (PAP-AUC) analysis. No VISA (vancomycin MIC, 4 to 8 μg/ml) or vancomycin-resistant (MIC ≥ 16 μg/ml) strains were detected. The Etest GRD screen for hVISA was initially positive for 68 isolates (1.6%; all by teicoplanin MIC ≥ 8 μg/ml at 24 or 48 h). Among those 68 isolates, 45 were reproducibly GRD positive. PAP-AUC testing confirmed only 11 isolates as hVISA (all had reproducible GRD-positive results). The 11 hVISA isolates were from nine medical centers and appeared genetically diverse (ten different PFGE types). The rates of resistance (including intermediate) for hVISA were as follows: oxacillin, 82%; erythromycin, 82%; clindamycin, 73%; levofloxacin, 73%; trimethoprim-sulfamethoxazole, 9%; and daptomycin, 9%. All hVISA isolates were susceptible to linezolid, tigecycline, and ceftaroline. Our data suggest that the overall prevalence of hVISA in the United States is low (0.3%). The hVISA isolates represented 10.5% of isolates with vancomycin MICs of 2 μg/ml and 0.1% of isolates with vancomycin MICs of 1 μg/ml. The positive predictive value of GRD Etest for hVISA was 16.2% for initial screen positive and 24.4% for reproducibly positive results.

Emerging dilemmas with methicillin-resistant Staphylococcus aureus infections in children

PURPOSE OF REVIEW

There has been an increase in the incidence of methicillin-resistant Staphylococcus aureus (MRSA) infections in recent years. This article reviews the literature on three manifestations of MRSA infections in the head and neck of children: sinonasal infections, otologic infections, and neck abscesses.

RECENT FINDINGS

Historically nosocomial in origin, MRSA infections more recently are found to occur in otherwise healthy patients with no obvious risk factors. This community-acquired MRSA is known to be responsible for cutaneous abscesses in various regions of the body. Nasal carriage in healthy children is thought to account for increasing incidence of infections involving the respiratory tract as well as deep-space neck infections. Although these community-acquired strains of MRSA often retain susceptibility to nonbeta lactam antibiotics, there are reports of clindamycin resistance.

SUMMARY

There is an increase in incidence of MRSA among infections involving the head and neck in children. Vigilant monitoring of antibiotic susceptibilities is warranted as well as judicious use of culture-directed antibiotic agents in their treatment. Topical therapy may play an important role in treatment of infections involving the sinonasal tract and ear.

Prevalence, severity, and treatment of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) skin and soft tissue infections in 10 medical clinics in Texas: a South Texas Ambulatory Research Network (STARNet) study

OBJECTIVES

Quantify the prevalence, measure the severity, and describe treatment patterns in patients who present to medical clinics in Texas with community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) skin and soft-tissue infections (SSTI).

METHODS

Ten primary care clinics participated in this prospective, community-based study. Clinicians consented patients and collected clinical information, pictures, and wound swabs; data were processed centrally. MRSASelect™ was used for identification. Susceptibilities were determined via Etest®.

RESULTS

Overall, 73 of 119 (61%) patients presenting with SSTIs meeting eligibility requirements had CA-MRSA. Among these, 49% were male, 79% were Hispanic, and 30% had diabetes. Half (56%) of the lesions were ≥ 5 cm in diameter. Most patients had abscesses (82%) and many reported pain scores of ≥ 7 of 10 (67%). Many presented with erythema (85%) or drainage (56%). Most received incision and drainage plus an antibiotic (64%). Antibiotic monotherapy was frequently prescribed: trimethoprim-sulfamethoxazole (TMP-SMX) (78%), clindamycin (4%), doxycycline (2%), and mupirocin (2%). The rest received TMP-SMX in combination with other antibiotics. TMP-SMX was frequently administered as one double-strength tablet twice daily. Isolates were 93% susceptible to clindamycin and 100% susceptible to TMP-SMX, doxycycline, vancomycin, and linezolid.

CONCLUSIONS

We report a predominance of CA-MRSA SSTIs, favorable antibiotic susceptibilities, and frequent use of TMP-SMX in primary care clinics.