Costs of skin and skin structure infections due to Staphylococcus aureus: an analysis of managed-care claims

A Review of the Clinical Utilization of Oral Antibacterial Therapy in the Treatment of Bone Infections in Adults

Chronic osteomyelitis in adults is managed with prolonged courses of intravenous antibiotics in conjunction with surgical debridement of necrotic bone. Over the past 40 years, there has been no paradigm shift in this approach, as randomized controlled trials of this standard of care compared to alternatives such as prolonged oral antibiotics are scarce. However, there have been many small trials, case reports, and review papers evaluating the effectiveness of oral treatment for chronic osteomyelitis. The oral route for infections requiring prolonged treatment is intuitively and practically more favorable due to several advantages, the most important of which is the avoidance of long-term IV antimicrobial therapy with its complications, inconvenience, and cost. In this paper, we review the literature evaluating oral antibiotic therapy in the management of chronic bone infections since 1975. The majority of osteomyelitis infections are caused by Staphylococcus aureus, hence we focus on its treatment using oral antibiotics; however, we also emphasize subpopulations of patients with diabetes, implanted hardware, and with less common bacterial organisms. The primary objective of this review is to promulgate clinical recommendations on the use of oral antibiotics in bone infections in the context of initial therapy, transition from intravenous therapy, and the role of chronic suppression. The secondary objective is to summarize current knowledge of the specific oral antimicrobial agents that are commonly utilized, together with a synopsis of the available literature pertaining to their pharmacokinetic/pharmacodynamic properties and duration of therapy in bone infection.

Clinical Impact of Staphylococcus aureus Skin and Soft Tissue Infections

The pathogenic bacterium Staphylococcus aureus is the most common pathogen isolated in skin-and-soft-tissue infections (SSTIs) in the United States. Most S. aureus SSTIs are caused by the epidemic clone USA300 in the USA. These infections can be serious; in 2019, SSTIs with S. aureus were associated with an all-cause, age-standardized mortality rate of 0.5 globally. Clinical presentations of S. aureus SSTIs vary from superficial infections with local symptoms to monomicrobial necrotizing fasciitis, which can cause systemic manifestations and may lead to serious complications or death. In order to cause skin infections, S. aureus employs a host of virulence factors including cytolytic proteins, superantigenic factors, cell wall-anchored proteins, and molecules used for immune evasion. The immune response to S. aureus SSTIs involves initial responders such as keratinocytes and neutrophils, which are supported by dendritic cells and T-lymphocytes later during infection. Treatment for S. aureus SSTIs is usually oral therapy, with parenteral therapy reserved for severe presentations; it ranges from cephalosporins and penicillin agents such as oxacillin, which is generally used for methicillin-sensitive S. aureus (MSSA), to vancomycin for methicillin-resistant S. aureus (MRSA). Treatment challenges include adverse effects, risk for Clostridioides difficile infection, and potential for antibiotic resistance.

Age-based health and economic burden of skin and soft tissue infections in the United States, 2000 and 2012

OBJECTIVE

The aim of this study was to compare the incidence of skin and soft tissue infections (SSTIs) across healthcare settings and analyze direct healthcare expenditures related to SSTIs in 2000 and 2012 in the United States.

METHODS

We performed a retrospective, cross-sectional analysis of nationally representative data from the Medical Expenditure Panel Surveys. Population-based incidence rates were examined for all healthcare settings that include inpatient visits, emergency department visits and ambulatory visits for SSTIs. The direct costs of healthcare services utilization were reported. Population-based prescribing rates for each antimicrobial class during ambulatory visits were compared.

RESULTS

A total of 2.4 million patients experienced an SSTI in 2000 compared to 3.3 million in 2012 (40% increase). From 2000 to 2012, the incidence of patients with at least one hospital visit for SSTIs increased 22%, ambulatory care visits increased 30%, and emergency department visits increased 40%. The incidence of SSTIs in children and adolescents declined 50% (from 150 to 76 per 10,000 person; RR = 0.51, 95% CI: 0.38-0.67; p<0.001) whereas SSTIs in older adults (> 65 years of age) increased almost 2-fold (from 67 to 130 per 10,000 person; RR = 1.94, 95% CI: 1.44-2.61; p<0.001). The annual incidence of SSTI in adults did not change significantly from 2000 to 2012 (from 84 to 81 per 10,000 person; RR = 0.96, 95% CI: 0.71-1.31; p = 0.41). The total estimated direct healthcare costs of SSTIs increased 3-fold from $4.8 billion in 2000 to $15.0 billion in 2012, largely driven by an 8-fold increase in ambulatory expenditures for SSTIs. Total population-based antimicrobial prescription rates for SSTIs increased 4-fold from 2000 to 2012 (from 59.5 to 250.4 per 10,000 person).

CONCLUSIONS

The highest healthcare utilization for SSTI treatment occurred in the ambulatory care setting and also accounted for the largest increase in overall direct expenditures from 2000 to 2012.

Dalbavancin and Oritavancin: An Innovative Approach to the Treatment of Gram-Positive Infections

Health care-associated infections, especially those caused by multidrug-resistant gram-positive organisms, such as methicillin-resistant Staphylococcus aureus (MRSA), are a growing public health threat. In 2014, the U.S. Food and Drug Administration approved two new lipoglycopeptides, oritavancin and dalbavancin, for the treatment of acute bacterial skin and skin structure infections. The rationale for the development of these antimicrobials was partly to aid in the battle against vancomycin resistance in both Staphylococcus and Enterococcus. Considered a subclass of the glycopeptide antibiotics, the new lipoglycopeptides have similar mechanisms of action of binding to the carboxyl terminal d-alanyl-d-alanine residue of the growing peptide chains but differ from their parent glycopeptides by the addition of lipophilic tails. This addition allows for these agents to have prolonged half-lives, giving them unique dosing profiles. In addition, by concentrating at the site of action, they have increased potency against MRSA compared with vancomycin, the current mainstay of therapy. In this review, we focus on comparing and contrasting these two new agents with regard to their pharmacology, mechanisms of action, spectrum of activity, safety profiles, dosage and administration, and drug and laboratory interactions, and we review the clinical trials evaluating their use.

Ceftaroline fosamil treatment outcomes compared with standard of care among hospitalized patients with complicated skin and soft tissue infections

AIM

Compare clinical and cost outcomes associated with ceftaroline fosamil with other commonly used antibiotics in complicated skin and soft tissue infections.

METHODS

Retrospective analysis of hospital records from 2010 to 2013 in Premier's Perspective comparative database for adults with complicated skin and soft tissue infection treated with intravenous ceftaroline fosamil, vancomycin, daptomycin, linezolid or tigecycline. Length of stay, inpatient costs and mortality were compared between propensity score-matched treatment groups.

RESULTS & CONCLUSION

Compared with the other commonly used antibiotics, matched patients in the ceftaroline fosamil treatment group had an equivalent (1%) or lower (compared with linezolid, 2%) in-hospital mortality rate, and significantly lower (p < 0.001) average unadjusted and regression-adjusted length of stay and inpatient costs (savings of $3398.80 compared with daptomycin).

Resource use in patients hospitalized with complicated skin and soft tissue infections in Europe and analysis of vulnerable groups: the REACH study

BACKGROUND

Hospitalized patients with complicated skin and soft tissue infections (cSSTI) present a substantial economic burden, and resource use can vary according to the presence of comorbidities, choice of antibiotic agent, and the requirement for initial treatment modification. REACH (NCT01293435) was a retrospective, observational study aimed at collecting empirical data on current (year 2010-2011) management strategies of cSSTI in 10 European countries.

METHODS

Patients (n = 1995) were aged ≥18 years, hospitalized with a cSSTI and receiving intravenous antibiotics. Data, collected via electronic Case Report Forms, detailed patient characteristics, medical history, disease characteristics, microbiological diagnosis, disease course and outcomes, treatments before and during hospitalization, and health resource consumption.

RESULTS

For the analysis population, mean length of hospital stay (including duration of hospitalizations for patients with recurrences) was 18.5 days (median 12.0). Increased length of hospital stay was found for patients with comorbidities vs those without (mean = 19.9; [median = 14.0] days vs 13.3 [median = 8.0] days), for patients with methicillin-resistant Staphylococcus aureus compared with patients with methicillin-sensitive S. aureus (mean = 27.7 [median = 19.5] days vs 18.4 [median = 13.0] days) and for patients requiring surgery (mean = 24.4 [median = 16.0] days vs 15.0 [median = 11.0] days). Patients requiring modification of their initial antibiotic treatment had an associated increase in mean length of hospital stay of 10.9 days (median = 6.5) and additional associated hospital resource use. A multivariate analysis confirmed the association of nosocomial infections, comorbidities, directed treatment, recurrent infections, diabetes, recent surgery, and older age (≥65 years), with longer hospital stay.

CONCLUSIONS

This study provides real-life data on factors that are expected to impact length of hospital stay, to guide clinical decision-making to improve outcomes, and reduce resource use in patients with cSSTI.

Incidence and cost of hospitalizations associated with Staphylococcus aureus skin and soft tissue infections in the United States from 2001 through 2009

BACKGROUND

The emergence of community-associated methicillin-resistant Staphylococcus aureus (SA) and its role in skin and soft tissue infections (SSTIs) accentuated the role of SA-SSTIs in hospitalizations.

METHODS

We used the Nationwide Inpatient Sample and Census Bureau data to quantify population-based incidence and associated cost for SA-SSTI hospitalizations.

RESULTS

SA-SSTI associated hospitalizations increased 123% from 160,811 to 358,212 between 2001 and 2009, and they represented an increasing share of SA- hospitalizations (39% to 51%). SA-SSTI incidence (per 100,000 people) doubled from 57 in 2001 to 117 in 2009 (p<0.01). A significant increase was observed in all age groups. Adults aged 75+ years and children 0-17 years experienced the lowest (27%) and highest (305%) incidence increase, respectively. However, the oldest age group still had the highest SA-SSTI hospitalization incidence across all study years. Total annual cost of SA-SSTI hospitalizations also increased and peaked in 2008 at $4.84 billion, a 44% increase from 2001. In 2009, the average associated cost of a SA-SSTI hospitalization was $11,622 (SE=$200).

CONCLUSION

There has been an increase in the incidence and associated cost of SA-SSTI hospitalizations in U.S.A. between 2001 and 2009, with the highest incidence increase seen in children 0-17 years. However, the greatest burden was still seen in the population over 75 years. By 2009, SSTI diagnoses were present in about half of all SA-hospitalizations.

Comparative analysis of empiric antimicrobial treatments for skin and soft tissue infections in newly hospitalized patients

PURPOSE

Intravenous vancomycin is the standard empiric treatment for complicated skin and soft tissue infections (SSTIs) due to its coverage against methicillin-resistant Staphylococcus aureus (MRSA). The objective of this study was to compare the hospital length of stay (LOS) between vancomycin-treated patients and patients receiving newer anti-MRSA agents. The study also aimed to identify factors associated with therapy change in patients receiving vancomycin on admission.

METHODS

Electronic medical records were used to conduct this retrospective cohort study. The LOS was compared among 5 groups of adult patients with admission diagnoses for SSTI who were initiated on linezolid, daptomycin, ceftaroline, tigecycline, or vancomycin. Survival analysis was used to identify factors associated with therapy change from vancomycin to another study medication.

RESULTS

Vancomycin was prescribed in 1046 (92%) admissions. Although none of the between-group differences in LOS reached statistical significance, there was a trend toward shorter LOS in vancomycin-treated patients compared to linezolid-treated patients (P = .059). Coagulopathy was independently associated with increased likelihood of therapy change from vancomycin (hazard ratio = 4.71; P <.001).

CONCLUSIONS

In the treatment of SSTI, newer agents result in LOS comparable to vancomycin. In patients initiated on vancomycin, therapy change was associated with longer LOS. Coagulopathy was independently associated with increased probability of therapy change.

Economic burden of inpatient and outpatient antibiotic treatment for methicillin-resistant Staphylococcus aureus complicated skin and soft-tissue infections: a comparison of linezolid, vancomycin, and daptomycin

Background

Previous economic analyses evaluating treatment of methicillin-resistant Staphylococcus aureus (MRSA) complicated skin and soft-tissue infections (cSSTI) failed to include all direct treatment costs such as outpatient parenteral antibiotic therapy (OPAT). Our objective was to develop an economic model from a US payer perspective that includes all direct inpatient and outpatient costs incurred by patients with MRSA cSSTI receiving linezolid, vancomycin, or daptomycin.

Methods

A 4-week decision model was developed for this economic analysis. Published literature and database analyses with validation by experts provided clinical, resource use, and cost inputs on data such as efficacy rate, length of stay, adverse events, and OPAT services. Base-case analysis assumed equal efficacy and equal length of stay for treatments. We conducted several sensitivity analyses where assumptions on resource use or efficacy were varied. Costs were reported in year-end 2011 US dollars.

Results

Total treatment costs in the base-case were lower for linezolid ($10,571) than vancomycin ($11,096), and daptomycin ($13,612). Inpatient treatment costs were $740 more, but outpatient costs, $1,266 less with linezolid than vancomycin therapy due to a switch to oral linezolid when the patient was discharged. Compared with daptomycin, both inpatient and outpatient treatment costs were lower with linezolid by $87 and $2,954 respectively. In sensitivity analyses, linezolid had lower costs compared with vancomycin and daptomycin when using differential length of stay data from a clinical trial, and using success rates from a meta-analysis. In a scenario without peripherally inserted central catheter line costs, linezolid became slightly more expensive than vancomycin (by $285), but remained less costly than daptomycin (by $2,316).

Conclusion

Outpatient costs of managing MRSA cSSTI may be reduced by 30%–50% with oral linezolid compared with vancomycin or daptomycin. Results from this analysis support potential economic benefit and cost savings of using linezolid versus traditional OPAT when total inpatient and outpatient medical costs are evaluated.

Treatment failure and costs in patients with methicillin-resistant Staphylococcus aureus (MRSA) skin and soft tissue infections: a South Texas Ambulatory Research Network (STARNet) study

OBJECTIVE

To measure the incidence of treatment failure and associated costs in patients with methicillin-resistant Staphylococcus aureus skin and soft tissue infections (SSTIs).

METHODS

This was a prospective, observational study in 13 primary care clinics. Primary care providers collected clinical data, wound swabs, and 90-day follow-up information. Patients were considered to have "moderate or complicated" SSTIs if they had a lesion ≥5 cm in diameter or diabetes mellitus. Treatment failure was evaluated within 90 days of the initial visit. Cost estimates were obtained from federal sources.

RESULTS

Overall, treatment failure occurred in 21% of patients (21 of 98) at a mean additional cost of $1,933.71 per patient. In a subgroup analysis of patients who received incision and drainage, those with moderate or complicated SSTIs had higher rates of treatment failure than those with mild or uncomplicated SSTIs (36% vs. 10%; P=.04).

CONCLUSIONS

One in 5 patients presenting to a primary care clinic for a methicillin-resistant S. aureus SSTI will likely require additional interventions at an associated cost of almost $2,000 per patient. Baseline risk stratification and new treatment approaches are needed to reduce treatment failures and costs in the primary care setting.

Inhibition of toxic shock by human monoclonal antibodies against staphylococcal enterotoxin B

Background

Staphylococcus aureus is implicated in many opportunistic bacterial infections around the world. Rising antibiotic resistance and few alternative methods of treatment are just two looming problems associated with clinical management of S. aureus. Among numerous virulence factors produced by S. aureus, staphylococcal enterotoxin (SE) B is a secreted protein that binds T-cell receptor and major histocompatibility complex class II, potentially causing toxic shock mediated by pathological activation of T cells. Recombinant monoclonal antibodies that target SEB and block receptor interactions can be of therapeutic value.

Methodology/Principal Findings

The inhibitory and biophysical properties of ten human monoclonal antibodies, isolated from a recombinant library by panning against SEB vaccine (STEBVax), were examined as bivalent Fabs and native full-length IgG (Mab). The best performing Fabs had binding affinities equal to polyclonal IgG, low nanomolar IC₅₀s against SEB in cell culture assays, and protected mice from SEB-induced toxic shock. The orthologous staphylococcal proteins, SEC1 and SEC2, as well as streptococcal pyrogenic exotoxin C were recognized by several Fabs. Four Fabs against SEB, with the lowest IC₅₀s, were converted into native full-length Mabs. Although SEB-binding kinetics were identical between each Fab and respective Mab, a 250-fold greater inhibition of SEB-induced T-cell activation was observed with two Mabs.

Conclusions/Significance

Results suggest that these human monoclonal antibodies possess high affinity, target specificity, and toxin neutralization qualities essential for any therapeutic agent.

Proposed epidemiological case definition for serious skin infection in children

AIM

Researching the rising incidence of serious skin infections in children is limited by the lack of a consistent and valid case definition. We aimed to develop and evaluate a good quality case definition, for use in future research and surveillance of these infections.

METHODS

We tested the validity of the existing case definition, and then of 11 proposed alternative definitions, by assessing their screening performance when applied to a population of paediatric skin infection cases identified by a chart review of 4 years of admissions to a New Zealand hospital.

RESULTS

Previous studies have largely used definitions based on the International Classification of Diseases skin infection subchapter. This definition is highly specific (100%) but poorly sensitive (61%); it fails to capture skin infections of atypical anatomical sites, those secondary to primary skin disease and trauma, and those recorded as additional diagnoses. Including these groups produced a new case definition with 98.9% sensitivity and 98.8% specificity.

CONCLUSION

Previous analyses of serious skin infection in children have underestimated the true burden of disease. Using this proposed broader case definition should allow future researchers to produce more valid and comparable estimates of the true burden of these important and increasing infections.