Contemporary causes of skin and soft tissue infections in North America, Latin America, and Europe: Report from the SENTRY Antimicrobial Surveillance Program (1998–2004)

A fatal case of multidrug resistant acinetobacter necrotizing fasciitis: the changing scary face of nosocomial infection

Necrotizing fasciitis is an uncommon soft-tissue infection, associated with high morbidity and mortality. Early recognition and treatment are crucial for survival. Acinetobacter baumannii is rarely associated with necrotizing fasciitis. Wound infections due to A. baumannii have been described in association with severe trauma in soldiers. There are only sporadic reports of monomicrobial A. baumannii necrotizing fasciitis. We report a unique case of monomicrobial necrotizing fasciitis caused by multidrug resistant (MDR) A. baumannii, in absence of any preceding trauma, surgery, or any obvious breech in the continuity of skin or mucosa. A 48-year-old woman with history of HIV, asthma, hypertension, and tobacco and excocaine use presented with acute respiratory failure requiring mechanical ventilation. She was treated for pneumonia for 7 days and was successfully extubated. All septic work-up was negative. Two days later, she developed rapidly spreading nonblanching edema with bleb formation at the lateral aspect of right thigh. Emergent extensive debridement and fasciotomy were performed. Operative findings and histopathology were consistent with necrotizing fasciitis. Despite extensive debridement, she succumbed to septic shock in the next few hours. Blood, wound, and tissue cultures grew A. baumannii, sensitive only to amikacin and polymyxin. Histopathology was consistent with necrotizing fasciitis.

Hospitalist perspective on the treatment of skin and soft tissue infections

The prevalence of skin and soft tissue infections (SSTIs) has been increasing in the United States. These infections are associated with an increase in hospital admissions. Hospitalists play an increasingly important role in the management of these infections and need to use hospital resources efficiently and effectively. When available, observation units are useful for treating low-risk patients who do not require hospital admission. Imaging tools may help to exclude abscesses and necrotizing soft tissue infections; however, surgical exploration remains the principal means of diagnosing necrotizing soft tissue infections. The most common pathogens that cause SSTIs are streptococci and Staphylococcus aureus. Methicillin-resistant S aureus (MRSA) is a prevalent pathogen, and concerns are increasing regarding the unclear distinctions between community-acquired and hospital-acquired MRSA. Other less frequent pathogens that cause SSTIs include Enterococcus species, Escherichia coli, Klebsiella species, Enterobacter species, and Pseudomonas aeruginosa. Cephalexin and clindamycin are suitable options for infections caused by streptococcal species and methicillin-susceptible S aureus. The increasing resistance of S aureus and Streptococcus pyogenes to erythromycin limits its use in these infections, and better alternatives are available. Parenteral cefazolin, nafcillin, or oxacillin can be used in hospitalized patients with nonpurulent cellulitis caused by streptococci and methicillin-susceptible S aureus. When oral MRSA therapy is indicated, clindamycin, doxycycline, trimethoprim-sulfamethoxazole, or linezolid is appropriate. Vancomycin, linezolid, daptomycin, tigecycline, telavancin, and ceftaroline fosamil are intravenous options that should be used in MRSA infections that require patient hospitalization. In the treatment of patients with SSTIs, hospitalists are at the forefront of providing proper patient care that reduces hospital costs, duration of therapy, and therapeutic failures. This review updates guidelines on the management of SSTIs with a focus on infections caused by S aureus, particularly MRSA, and outlines the role of the hospitalist in the effective management of SSTIs.

The Antimicrobial Activity of (-)-Epigallocatehin-3-Gallate and Green Tea Extracts against Pseudomonas aeruginosa and Escherichia coli Isolated from Skin Wounds

Background

Skin infections with Gram-negative bacteria are sometimes challenging to treat, because these bacteria show multidrug resistance against commonly used antibiotics and patients with Gram-negative bacterial infection overall have deteriorated in conditions in many cases. Studies have shown that epigallocatechin gallate (EGCG) and green tea extracts (GTE) inhibit the growth of several Gram-positive bacteria species.

Objective

The purpose of this study was to investigate the minimum inhibitory concentrations (MICs) of EGCG and GTE in Pseudomonas aeruginosa and Escherichia coli, and assess the use of these chemicals as an alternative or adjunct topical antimicrobial agent against P. aeruginosa and E. coli with multidrug resistance.

Methods

The MICs of EGCG, GTE, and other tested antibiotics were measured and compared to determine the antibacterial efficacy and the differences in pattern of resistance.

Results

The P. aeruginosa and E. coli strains used in this study showed multidrug resistance. EGCG inhibited the growth of P. aeruginosa at a MIC level of 200~400 µg/ml. The MIC of GTE was a 1 : 16 dilution for P. aeruginosa. EGCG showed antimicrobial activity against E. coli at a MIC of 400 µg/ml. In the case of GTE, the MIC was a dilution between 1:8 and 1:4 for E. coli.

Conclusion

EGCG and GTE showed potential as alternative or adjunct topical antimicrobial agents for infections that are resistant to traditional antibiotic therapy.

Chinese herbal medicines for treating skin and soft-tissue infections

BACKGROUND

Skin and soft-tissue infections (SSTIs) are common infections of the epidermis, dermis or subcutaneous tissue. SSTIs range in severity from minor, self-limiting, superficial infections to deep, aggressive, gangrenous, life-threatening infections. Some classifications divide SSTIs into 'complicated' and 'uncomplicated' infections based on clinical severity. Treatments of SSTIs involves antibiotic therapy, surgical debridement or drainage, and resuscitation if required. Sometimes these treatments are limited by high treatment costs, bacterial resistance to antibiotics and side effects, therefore, many people with SSTIs are turning to Chinese herbal medicines to treat this problem.Chinese herbal medicines are natural substances that have been used for centuries in China where they are generally considered to be effective for SSTIs. Some Chinese herbal medicines have been shown to have antibacterial and anti-inflammatory properties, although a few herbal medicines have been reported to have side effects. Therefore there is a need to review the current clinical evidence systematically to inform current practice and guide future studies on Chinese herbal medicines for SSTIs.

OBJECTIVES

To evaluate the benefits and harms of Chinese herbal medicines for treating skin and soft-tissue infections (SSTIs).

SEARCH METHODS

Searches were not restricted by date, language or publication status. In July 2014 we searched the following electronic databases: the Cochrane Wounds Group Specialised Register; the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library); Ovid MEDLINE; Ovid MEDLINE (In-Process & Other Non-Indexed Citations); Ovid EMBASE; Ovid AMED (Allied and Complementary Medicine); and EBSCO CINAHL.

SELECTION CRITERIA

All randomised controlled trials (RCTs) in people with SSTIs that compared Chinese herbal medicines with another intervention or control.

DATA COLLECTION AND ANALYSIS

Two review authors screened the literature search results independently; there were no disagreements.

MAIN RESULTS

We identified no RCTs that met the inclusion criteria.

AUTHORS' CONCLUSIONS

There is currently no information available from RCTs to support or refute the use of Chinese herbal medicines in treating people with SSTIs.

The safety and efficacy of daptomycin versus other antibiotics for skin and soft-tissue infections: a meta-analysis of randomised controlled trials

OBJECTIVE

Daptomycin, a cyclic lipopeptide that exhibits rapid, concentration-dependent bactericidal activity in vitro against a broad spectrum of Gram-positive pathogens, has now, since 2003, been approved in more than 70 countries and regions to treat skin and soft-tissue infections (SSTIs). The purpose of this meta-analysis was to compare the safety and efficacy of daptomycin with other antibiotics, especially with vancomycin which has long been considered the standard therapy for complicated SSTIs.

DESIGN

Meta-analysis of randomised controlled trials (RCTs).

DATA SOURCES

We thoroughly searched PubMed, EMBASE, Cochrane Central to identify relevant RCTs. Six RCTs with a total of 1710 patients were included in this meta-analysis.

RESULTS

The results demonstrated that the efficacy of daptomycin was at par with or maybe better than other first-line antibiotics for treating SSTIs as shown by the OR for clinical success (OR=1.05, 95% CI 0.84 to 1.31, p=0.65, I(2)=0%); daptomycin versus vancomycin subgroup (OR=1.19, 95% CI 0.77 to 1.83, p=0.43, I(2)=0%); overall microbiological success (OR=1.05, 95% CI 0.61 to 1.79, p=0.86, I(2)=42%); microbiological success of daptomycin versus comparators for Staphylococcus aureus (SA, OR=1.05, 95% CI 0.61 to 2.60, p=0.53, I(2)=47%), for methicillin-resistant S. aureus (OR=0.90, 95% CI 0.77 to 1.06, p=0.20, I(2)=56%). However, daptomycin tended to have a similar treatment-related adverse events (AEs) incidence in comparison with other antibiotics (OR=1.06, 95% CI 0.71 to 1.59, p=0.76, I(2)=41%). The trend showed that daptomycin might cause less discontinuation due to AEs and death compared with other first-line antibiotics (OR=0.71, 95% CI 0.46 to 1.10, p=0.12, I(2)=11%). Significantly more patients in the daptomyicn group had creatine phosphokinase elevation than those in the control group; however, it could be reversed when the therapy ended (OR=1.95, 95% CI 1.04 to 3.65, p=0.04, I(2)=0).

CONCLUSIONS

This meta-analysis demonstrated that the safety and efficacy of daptomycin was not inferior to that of other first-line drugs, and daptomycin tended to exhibit superior efficacy when compared with vancomycin or with comparators for SA infections; nevertheless, more high-quality RCTs are needed to draw a more credible conclusion.

Susceptibility of Staphylococcus aureus to topical agents in the United States: a sentinel study

BACKGROUND

Mupirocin has been used topically for treating skin and skin structure infections and for nasal decolonization before surgical interventions. Pleuromutilin compounds, including retapamulin, provide similar treatment/interventional options. Rates of resistance of Staphylococcus aureus to mupirocin and other agents used to treat skin and skin structure infections vary between countries and medical centers, including those in the United States. These resistance rates may be associated with higher usage and/or improper epidemiologic practices.

OBJECTIVE

This study aimed to determine rates of resistance to topical and other class agents against S aureus isolates collected from SSSIs.

METHODS

Isolates were obtained from outpatients at 6 US dermatology centers in 5 states. Demographic data were collected from medical records, and each patient completed a study questionnaire on recent history of skin infections, antibiotic use, and hospitalization. Each isolate was tested against cephalothin, clindamycin, erythromycin, gentamicin, mupirocin, tetracycline, retapamulin, and trimethoprim/sulfamethoxazole.

RESULTS

Although methicillin-resistance rates varied between centers (range, 15.8%-35.5%), macrolide resistance was ~50% at all of the sites in this study. Mupirocin-resistant isolates were observed much more frequently from 1 center (33.9%), and nearly all demonstrated high-level resistance. Only 1 retapamulin-resistant isolate (0.5%) was observed, with a minimum inhibitory concentration of 16 µg/mL. The other agents had relatively low resistance rates, which varied between centers and were dependent on susceptibility to methicillin.

CONCLUSIONS

Although the rate of mupirocin-resistant S aureus isolates collected in this investigation was >10%, retapamulin resistance was infrequent. Surveillance of topical agents to determine resistance rates against targeted bacteria is necessary.

In vitro activity and in vivo animal model efficacy of IB-367 alone and in combination with imipenem and colistin against Gram-negative bacteria

The aim of our study was to evaluate the in vitro activity of IB-367 and its bactericidal effect for Pseudomonas aeruginosa and Escherichia coli, associated to a synergic study to test the antibiotic combinations between the peptide and colistin or imipenem. Minimum inhibitory concentrations (MICs), the minimum bactericidal concentrations (MBCs), the synergy test and killing study were carried out to evaluate the IB-367 activity. In the in vivo model, a wound was incised through the panniculus carnosus of BALB/c mice, and then inoculated with 5 × 107 colony-forming units of P. aeruginosa and E. coli. For each strain, the study included an infected or not infected group that did not receive any treatment, and five contaminated groups treated with local IB- 367, intraperitoneal imipenem, intraperitoneal colistin, topical IB-367 local plus intraperitoneal imipenem or intraperitoneal colistin. All isolates were inhibited by IB-367 at concentrations of 4-64 mg/l. Killing by IB-367 was shown to be very rapid: its activity on all Gram-negative bacteria was completed within a 40 min exposure period at a concentration of 2 × MIC/l. Synergy was demonstrated when IB-367 was combined with colistin or imipenem. In in vivo studies, the groups treated with topical IB-367 and intraperitoneal colistin showed the best results in terms of bacterial load inhibition either for Pseudomonas or for E. coli. The good in vitro activity and in vivo efficacy, as well as, the synergic interactions with antibiotics suggest that IB-367 is a promising candidate for potential application in the treatment of wound Gram-negative infections.

Cutaneous bacterial infections caused by Staphylococcus aureus and Streptococcus pyogenes in infants and children

Acute bacterial skin and skin structure infections (SSSIs) are among the most common bacterial infections in children. The medical burden of SSSIs, particularly abscesses, has increased nationwide since the emergence of community-acquired methicillin-resistant Staphylococcus aureus. SSSIs represent a wide spectrum of disease severity. Prompt recognition, timely institution of appropriate therapy, and judicious antimicrobial use optimize patient outcomes. For abscesses, incision and drainage are paramount and might avoid the need for antibiotic treatment in uncomplicated cases. If indicated, empiric antimicrobial therapy should target Streptococcus pyogenes for nonpurulent SSSIs, such as uncomplicated cellulitis, and S aureus for purulent SSSIs such as abscesses.

Antimicrobial activity of ceftaroline combined with avibactam tested against bacterial organisms isolated from acute bacterial skin and skin structure infections in United States medical centers (2010-2012)

Ceftaroline-avibactam and comparator agents were tested against clinical isolates collected at 174 medical centers from patients with acute bacterial skin and skin structure infection (ABSSSI) in the United States (USA) during 2010-2012. Isolates were processed at the medical centers and forwarded to a central laboratory for confirmatory identification and susceptibility testing using reference methods. Ceftaroline-avibactam was highly active against methicillin-susceptible (MIC50/90, 0.25/0.25 μg/mL) and methicillin-resistant Staphylococcus aureus (MRSA; MIC50/90, 0.5/1 μg/mL). Vancomycin, tigecycline, daptomycin, and linezolid were also active (>99.9% susceptible) against MRSA (51.4% of S. aureus), but activity against MRSA was decreased for erythromycin, levofloxacin, and clindamycin (10.8, 40.3, and 81.9% susceptible, respectively). β-Hemolytic streptococci were highly susceptible to β-lactam antimicrobials, including ceftaroline-avibactam (MIC50/90, ≤0.03/≤0.03 μg/mL). Ceftaroline-avibactam was very active against Escherichia coli and Klebsiella pneumoniae (MIC50/90, 0.03/0.06 and 0.06/0.25 μg/mL, respectively) including extended-spectrum β-lactamase (ESBL) screen-positive phenotypes (MIC50/90, 0.06/0.12 and 0.12/1 μg/mL, respectively). Susceptibility of ESBL screen-positive E. coli and K. pneumoniae was 100.0/97.9% for tigecycline and 99.2/56.1% for meropenem, respectively. Susceptibility to other agents for ESBL screen-positive E. coli and K. pneumoniae was decreased. Ceftaroline-avibactam exhibited a broad-spectrum of in vitro activity against isolates from patients in the USA with ABSSSI including MRSA, β-hemolytic streptococci, E. coli, and K. pneumoniae as well as ESBL screen-positive phenotype isolates and merits further study in clinical indications where these resistant organisms may be a concern.

Linezolid versus vancomycin for skin and soft tissue infections

BACKGROUND

The morbidity and treatment costs associated with skin and soft tissue infections (SSTIs) are high. Linezolid and vancomycin are antibiotics that are commonly used in treating skin and soft-tissue infections, specifically those infections due to methicillin-resistant Staphylococcus aureus (MRSA).

OBJECTIVES

To compare the effects and safety of linezolid and vancomycin for treating people with SSTIs.

SEARCH METHODS

In May 2013 we conducted searches of the following databases: Cochrane Wounds Group Specialised Register; The Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library); Ovid MEDLINE; Ovid MEDLINE (In-Process & Other Non-Indexed Citations); Ovid EMBASE; and EBSCO CINAHL. We also contacted manufacturers for details of unpublished and ongoing trials. We scrutinised citations within all obtained trials and major review articles to identify any additional trials.

SELECTION CRITERIA

We included all randomised controlled trials (RCTs) comparing linezolid with vancomycin in the treatment of SSTIs.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials, assessed risk of bias and extracted data. The primary outcomes were clinical cure, microbiological cure, and SSTI-related and treatment-related mortality. We performed subgroup analyses according to age, and whether the infection was due to MRSA.

MAIN RESULTS

We included nine RCTs (3144 participants). Linezolid was associated with a significantly better clinical (RR 1.09, 95% CI 1.03 to 1.16) and microbiological cure rate in adults (RR 1.08, 95% CI 1.01 to 1.16). For those infections due to MRSA, linezolid was significantly more effective than vancomycin in clinical (RR 1.09, 95% CI 1.03 to 1.17) and microbiological cure rates (RR 1.17, 95% CI 1.04 to 1.32). No RCT reported SSTI-related and treatment-related mortality. There was no significant difference in all-cause mortality between linezolid and vancomycin (RR 1.44, 95% CI 0.75 to 2.80). There were fewer incidents of red man syndrome (RR 0.04, 95% CI 0.01 to 0.29), pruritus (RR 0.36, 95% CI 0.17 to 0.75) and rash (RR 0.27, 95% CI 0.12 to 0.58) in the linezolid group compared with vancomycin, however, more people reported thrombocytopenia (RR 13.06, 95% CI 1.72 to 99.22), and nausea (RR 2.45, 95% CI 1.52 to 3.94) when treated with linezolid. It seems, from the available data, that length of stay in hospital was shorter for those in the linezolid group than the vancomycin group. The daily cost of outpatient therapy was less with oral linezolid than with intravenous vancomycin. Although inpatient treatment with linezolid cost more than inpatient treatment with vancomycin per day, the median length of hospital stay was three days shorter with linezolid. Thus, total hospital charges per patient were less with linezolid treatment than with vancomycin treatment.

AUTHORS' CONCLUSIONS

Linezolid seems to be more effective than vancomycin for treating people with SSTIs, including SSTIs caused by MRSA. The available evidence is at high risk of bias and is based on studies that were supported by the pharmaceutical company that makes linezolid. Further well-designed, independently-funded, RCTs are needed to confirm the available evidence.

Application of external drugs comprising silver compounds for the treatment of pyodermic patients

An external anti-bacterial therapy is selected for pyodermic patients empirically. Silver sulfathiazole has an evident anti-inflammatory and anti-microbial effect against a broad range of microorganisms. Goal of the study. To assess the efficacy, safety and tolerability of a cream comprising 2% silver sulfathiazole vs. 3% tetracycline ointment for the treatment of pyodermic patients. Materials and methods. The study involved 50 pyodermic patients (at the mean age of 23.5 ± 4.1 years) including 31 (62%) male and 19 (38%) female patients. The patients were divided into two groups: Group I (n = 35) used the cream comprising 2% silver sulfathiazole while Group II (n = 15) was administered 3% tetracycline ointment. All of the patients were assessed for clinical and microbiological efficacy of the therapy. Results. The average patient recovery time in Group I amounted to 8.7 ± 0.9 days and 13.1 ± 2.7 days in Group II (р < 0.01). As many as 33 patients (94.3%) achieved clinical recovery and 2 patients (5.7%) achieved improvement by Day 10 in Group I; in Group II, clinical recovery was observed in 8 patients (53.3%), improvement - in 3 patients (20%), and no effect - in 4 patients (26.7%). Conclusion. The external anti-bacterial monotherapy of pyodermic patients with the cream comprising 2% silver sulfathiazole is more efficient than treatment with 3% tetracycline ointment. High clinical and microbiological efficacy of the cream comprising 2% silver sulfathiazole makes it possible to recommend it for empirical treatment of pyodermic patients.

Efficacy of tigecycline for the treatment of complicated skin and soft-tissue infections in real-life clinical practice from five European observational studies

OBJECTIVES

Tigecycline is an approved treatment for complicated skin and soft-tissue infections (cSSTIs). The efficacy of tigecycline as monotherapy or in combination with other antibacterials in the treatment of cSSTI in routine practice is described.

PATIENTS AND METHODS

Individual patient-level data were pooled from five European observational studies (July 2006 to October 2011).

RESULTS

A total of 254 cSSTI patients who received tigecycline were included (mean age 63.2 ± 14.9 years). Of these, 34.4% were in intensive care units, 54.5% acquired their infection in hospital and 90.9% had at least one comorbidity. Infection most commonly affected the limbs (62.4%) and 43.8% of infections were classified as necrotizing. The mean Acute Physiology and Chronic Health Evaluation (APACHE) II and Sequential Organ Failure Assessment (SOFA) scores at the beginning of treatment were 15.0 ± 7.9 (n = 205) and 5.8 ± 3.9 (n = 32), respectively, indicating high disease severity. Staphylococcus aureus (52.7%), Escherichia coli (18.0%) and Enterococcus faecium (12.0%) were the most frequently isolated pathogens; 32.9% of infections were polymicrobial and 30.5% were due to resistant pathogens. Overall, 71.8% received tigecycline as monotherapy and 28.2% as combination therapy for a mean duration of 12 days. Clinical response rates at the end of treatment were 79.6% for all patients who received the standard dosage (183/230), 86.7% for patients who received tigecycline as monotherapy (143/165), 75.0% for patients with a nosocomial infection (96/128), 75.3% for patients with an APACHE II score >15 (61/81) and 58.3% for patients with a SOFA score ≥ 7 (7/12).

CONCLUSIONS

In these real-life studies, tigecycline, alone and in combination, achieved favourable clinical response rates in patients with cSSTI with a high severity of illness.

Resistance mechanisms and epidemiology of multiresistant pathogens in Europe and efficacy of tigecycline in observational studies

OBJECTIVES

Antimicrobial drug resistance is a growing problem in Europe and, even with differences in epidemiology, it is of great concern. The treatment of complicated skin and soft-tissue infections (cSSTIs) and complicated intra-abdominal infections (cIAIs) is hindered further by pathogens that are resistant to methicillin, carbapenems, third-generation cephalosporins and glycopeptides.

PATIENTS AND METHODS

An analysis of the microbiological results from five European observational studies (July 2006 to October 2011) evaluating the efficacy of tigecycline (prescribed as monotherapy or in combination with other antibacterials) for the treatment of cSSTI and cIAI is presented.

RESULTS

In total, 213 cSSTI and 623 cIAI patients were included; 34.4% and 56.6%, respectively, were critically ill in intensive care units. At baseline, at least one pathogen was isolated in 167 (78.4%) cSSTI and 464 (74.5%) cIAI patients, and 32.9% and 49.1% of infections were polymicrobial. In cSSTI, Staphylococcus aureus and Escherichia coli (52.7% and 18.0%, respectively) were the most frequently isolated pathogens, whereas in cIAI most infections were due to E. coli (41.8%), Enterococcus faecium (40.1%) and Enterococcus faecalis (21.1%). Clinical response was observed in >80% of patients with E. coli in both cIAI and cSSTI. In cSSTI patients, the clinical response rate to S. aureus was 80.8%. For cIAI, 77.4% of E. faecium and 79.5% of E. faecalis patients responded to treatment.

CONCLUSIONS

Tigecycline when given alone or in combination with other antibacterials appeared to be efficacious against multiple pathogens, affirming its role in real-life clinical practice as a broad-spectrum antibacterial for the treatment of patients with cSSTI and cIAI, including the critically ill, across Europe.

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.

Linezolid versus vancomycin for skin and soft tissue infections

BACKGROUND

The morbidity and treatment costs associated with skin and soft tissue infections (SSTIs) are high. Linezolid and vancomycin are antibiotics that are commonly used in treating skin and soft-tissue infections, specifically those infections due to methicillin-resistant Staphylococcus aureus (MRSA).

OBJECTIVES

To compare the effects and safety of linezolid and vancomycin for treating people with SSTIs.

SEARCH METHODS

In May 2013 we conducted searches of the following databases: Cochrane Wounds Group Specialised Register; The Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library); Ovid MEDLINE; Ovid MEDLINE (In-Process & Other Non-Indexed Citations); Ovid EMBASE; and EBSCO CINAHL. We also contacted manufacturers for details of unpublished and ongoing trials. We scrutinised citations within all obtained trials and major review articles to identify any additional trials.

SELECTION CRITERIA

We included all randomised controlled trials (RCTs) comparing linezolid with vancomycin in the treatment of SSTIs.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials, assessed risk of bias and extracted data. The primary outcomes were clinical cure, microbiological cure, and SSTI-related and treatment-related mortality. We performed subgroup analyses according to age, and whether the infection was due to MRSA.

MAIN RESULTS

We included nine RCTs (3144 participants). Linezolid was associated with a significantly better clinical (RR 1.09, 95% CI 1.03 to 1.16) and microbiological cure rate in adults (RR 1.08, 95% CI 1.01 to 1.16). For those infections due to MRSA, linezolid was significantly more effective than vancomycin in clinical (RR 1.09, 95% CI 1.03 to 1.17) and microbiological cure rates (RR 1.17, 95% CI 1.04 to 1.32). No RCT reported SSTI-related and treatment-related mortality. There was no significant difference in all-cause mortality between linezolid and vancomycin (RR 1.44, 95% CI 0.75 to 2.80). There were fewer incidents of red man syndrome (RR 0.04, 95% CI 0.01 to 0.29), pruritus (RR 0.36, 95% CI 0.17 to 0.75) and rash (RR 0.27, 95% CI 0.12 to 0.58) in the linezolid group compared with vancomycin, however, more people reported thrombocytopenia (RR 13.06, 95% CI 1.72 to 99.22), and nausea (RR 2.45, 95% CI 1.52 to 3.94) when treated with linezolid. It seems, from the available data, that length of stay in hospital was shorter for those in the linezolid group than the vancomycin group. The daily cost of outpatient therapy was less with oral linezolid than with intravenous vancomycin. Although inpatient treatment with linezolid cost more than inpatient treatment with vancomycin per day, the median length of hospital stay was three days shorter with linezolid. Thus, total hospital charges per patient were less with linezolid treatment than with vancomycin treatment.

AUTHORS' CONCLUSIONS

Linezolid seems to be more effective than vancomycin for treating people with SSTIs, including SSTIs caused by MRSA. The available evidence is at high risk of bias and is based on studies that were supported by the pharmaceutical company that makes linezolid. Further well-designed, independently-funded, RCTs are needed to confirm the available evidence.

Ceftaroline fosamil: a review of its use in the treatment of complicated skin and soft tissue infections and community-acquired pneumonia

Ceftaroline, the active metabolite of the prodrug ceftaroline fosamil (Zinforo, Teflaro), is an advanced-generation, parenteral cephalosporin with broad-spectrum antibacterial activity in vitro against Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA) and multidrug resistant Streptococcus pneumoniae and Gram-negative bacteria, including Haemophilus influenzae and Moraxella catarrhalis, but not Pseudomonas aeruginosa. Ceftaroline has demonstrated a low potential for the selection of resistance in vitro for drug-resistant Gram-positive organisms, including MRSA, as well as for Gram-negative respiratory pathogens. In pivotal phase III studies, intravenous ceftaroline fosamil demonstrated noninferiority to intravenous vancomycin plus aztreonam in patients hospitalized with complicated skin and soft tissue infections (cSSTIs) and intravenous ceftriaxone in patients hospitalized with community-acquired pneumonia (CAP) [Pneumonia Outcomes Research Team (PORT) risk class III or IV]; however, patients with CAP admitted to the intensive care unit were not evaluated. Ceftaroline fosamil was generally well tolerated in these trials, with an adverse event profile similar to that of other cephalosporins. Diarrhoea was the most commonly reported adverse event; however, the risk of Clostridium difficile-associated diarrhoea with ceftaroline fosamil appeared to be low. Potential limitations of the drug include the lack of an oral formulation and the requirement for twice-daily administration. Nonetheless, ceftaroline fosamil represents an attractive option (either alone or in combination with other agents) for the initial empirical treatment of patients hospitalized with cSSTIs (including those with suspected MRSA infection) or CAP (PORT risk class III or IV) who require intravenous antimicrobial therapy. As with all antibacterial agents, ceftaroline fosamil should be used in accordance with good antimicrobial stewardship.

Ceftaroline fosamil use in hospitalized patients with acute bacterial skin and skin structure infections: Budget impact analysis from a hospital perspective

PURPOSE

The budgetary impact of adding ceftaroline fosamil to a hospital formulary for the treatment of acute bacterial skin and skin structure infections (ABSSSIs) was evaluated.

METHODS

A three-year hospital budget impact model was constructed with three initial treatment options for ABSSSIs: ceftaroline fosamil, vancomycin plus aztreonam, and other vancomycin-containing regimens. The target population was hospitalized adult patients with an ABSSSI. Clinical cure rates with initial treatment were assumed to be similar to those from ceftaroline fosamil clinical trials. Patients who did not respond to initial treatment were assumed to be treated successfully with second-line antimicrobial therapy. Length of stay and cost per hospital day (by success or failure with initial treatment) were estimated based on a large database from more than 100 U.S. hospitals. Other model inputs included the annual number of ABSSSI admissions, projected annual case growth rate, proportion of ABSSSI target population receiving vancomycin-containing regimen, expected proportion of ABSSSI target population to be treated with ceftaroline fosamil, drug acquisition cost, cost of antibiotic administration, and cost of vancomycin monitoring. Sensitivity analysis using 95% confidence limits of clinical cure rates was also performed.

RESULTS

The estimated total cost of care for treating a patient with an ABSSSI was $395 lower with ceftaroline fosamil ($15,087 versus $15,482) compared with vancomycin plus aztreonam and $72 lower ($15,087 versus $15,159) compared with other vancomycin-containing regimens.

CONCLUSION

Model estimates indicated that adding ceftaroline fosamil to the hospital formulary would not have a negative effect on a hospital's budget for ABSSSI treatment.

Moxifloxacin in complicated skin and skin structure infections (cSSSIs): A prospective, international, non-interventional, observational study

Introduction

ARTOS was an international, prospective, non-interventional, non-controlled observational study designed to determine the effectiveness, safety, and tolerability of moxifloxacin under daily-life conditions in patients with complicated skin and skin structure infections (cSSSIs) treated in Europe, the Middle East, and Asia–Pacific region.

Methods

Eligible patients included males and females who were hospitalized patients or outpatients requiring antibiotic therapy for cSSSIs and for whom the treating physician had elected to begin moxifloxacin therapy in accordance with its approved indications. Patients were assessed before therapy and then at one or two follow-up visits. Effectiveness was assessed with respect to improvement and resolution of signs and symptoms of cSSSIs and safety with respect to the nature and frequency of adverse events and adverse drug reactions.

Results

A total of 6,594 patients were enrolled of whom 5,444 had data available for analysis; 4,692 patients received sequential intravenous/oral (IV/PO) moxifloxacin and 752 exclusively IV therapy. A majority of patients were aged between 40 and 79 years and had one or more comorbid conditions. Post-surgical wound infection, skin abscess, and diabetic foot infection were the cSSSIs most frequently diagnosed and treated with moxifloxacin, with almost 90% of infections rated moderate or severe. Treating physicians chose sequential moxifloxacin 400 mg for most patients, switching from IV to PO after 3–4 days. On average, treatment was maintained for 10 days. Treatment with moxifloxacin was associated with rapid relief in symptoms, with 93.2% of patients experiencing either complete resolution of symptoms or improvement at follow-up. Moxifloxacin was well tolerated with adverse drug reactions occurring in only 2% of patients.

Conclusions

This study, conducted in a ‘real-world’ setting, confirms the effectiveness and safety of moxifloxacin in the treatment of a wide spectrum of cSSSIs seen in routine clinical practice.

Incidence, microbiology, and patient characteristics of skin and soft-tissue infections in a U.S. population: a retrospective population-based study

Background

Skin and soft tissue infections (SSTIs) are commonly occurring infections with wide-ranging clinical manifestations, from mild to life-threatening. There are few population-based studies of SSTIs in the period after the rapid increase in community-acquired methicillin-resistant Staphyloccus aureus (MRSA).

Methods

We used electronic databases to describe the incidence, microbiology, and patient characteristics of clinically-diagnosed skin and soft tissue infections (SSTIs) among members of a Northern California integrated health plan. We identified demographic risk factors associated with SSTIs and MRSA infection.

Results

During the three-year study period from 2009 to 2011, 376,262 individuals experienced 471,550 SSTI episodes, of which 23% were cultured. Among cultured episodes, 54% were pathogen-positive. Staphylococcus aureus (S. aureus) was isolated in 81% of pathogen-positive specimens, of which nearly half (46%) were MRSA. The rate of clinically-diagnosed SSTIs in this population was 496 per 10,000 person-years. After adjusting for age group, gender, race/ethnicity and diabetes, Asians and Hispanics were at reduced risk of SSTIs compared to whites, while diabetics were at substantially higher risk compared to non-diabetics. There were strong age group by race/ethnicity interactions, with African Americans aged 18 to <50 years being disproportionately at risk for SSTIs compared to persons in that age group belonging to other race/ethnicity groups. Compared to Whites, S. aureus isolates of African-Americans and Hispanics were more likely to be MRSA (Odds Ratio (OR): 1.79, Confidence Interval (CI): 1.67 to 1.92, and, OR: 1.24, CI: 1.18 to 1.31, respectively), while isolates from Asians were less likely to be MRSA (OR: 0.73, CI: 0.68 to 0.78).

Conclusions

SSTIs represent a significant burden to the health care system. The majority of culture-positive SSTIs were caused by S. aureus, and almost half of the S. aureus SSTIs were methicillin-resistant. The reasons for African-Americans having a higher likelihood, and Asians a lower likelihood, for their S. aureus isolates to be methicillin-resistant, should be further investigated.

Extensive dissemination of methicillin-resistant Staphylococcus aureus (MRSA) between the hospital and the community in a country with a high prevalence of nosocomial MRSA

According to the EARS-Net surveillance data, Portugal has the highest prevalence of nosocomial methicillin-resistant Staphylococcus aureus (MRSA) in Europe, but the information on MRSA in the community is very scarce and the links between the hospital and community are not known. In this study we aimed to understand the events associated to the recent sharp increase in MRSA frequency in Portugal and to evaluate how this has shaped MRSA epidemiology in the community. With this purpose, 180 nosocomial MRSA isolates recovered from infection in two time periods and 14 MRSA isolates recovered from 89 samples of skin and soft tissue infections (SSTI) were analyzed by pulsed-field gel electrophoresis (PFGE), staphylococcal chromosome cassette mec (SCCmec) typing, spa typing and multilocus sequence typing (MLST). All isolates were also screened for the presence of Panton Valentine leukocidin (PVL) and arginine catabolic mobile element (ACME) by PCR. The results showed that ST22-IVh, accounting for 72% of the nosocomial isolates, was the major clone circulating in the hospital in 2010, having replaced two previous dominant clones in 1993, the Iberian (ST247-I) and Portuguese (ST239-III variant) clones. Moreover in 2010, three clones belonging to CC5 (ST105-II, ST125-IVc and ST5-IVc) accounted for 20% of the isolates and may represent the beginning of new waves of MRSA in this hospital. Interestingly, more than half of the MRSA isolates (8/14) causing SSTI in people attending healthcare centers in Portugal belonged to the most predominant clones found in the hospital, namely ST22-IVh (n = 4), ST5-IVc (n = 2) and ST105-II (n = 1). Other clones found included ST5-V (n = 6) and ST8-VI (n = 1). None of the MRSA isolates carried PVL and only five isolates (ST5-V-t179) carried ACME type II. The emergence and spread of EMRSA-15 may be associated to the observed increase in MRSA frequency in the hospital and the consequent spillover of MRSA into the community.

Potential role of tedizolid phosphate in the treatment of acute bacterial skin infections

Tedizolid phosphate (TR-701), a prodrug of tedizolid (TR-700), is a next-generation oxazolidinone that has shown favorable results in the treatment of acute bacterial skin and skin-structure infections in its first Phase III clinical trial. Tedizolid has high bioavailability, penetration, and tissue distribution when administered orally or intravenously. The activity of tedizolid was greater than linezolid against strains of Staphylococcus spp., Streptococcus spp., and Enterococcus spp. in vitro studies, including strains resistant to linezolid and those not susceptible to vancomycin or daptomycin. Its pharmacokinetic characteristics allow for a once-daily administration that leads to a more predictable efficacy and safety profile than those of linezolid. No hematological adverse effects have been reported associated with tedizolid when used at the therapeutic dose of 200 mg in Phase I, II, or III clinical trials of up to 3 weeks of tedizolid administration. Given that the clinical and microbiological efficacy are similar for the 200, 300, and 400 mg doses, the lowest effective dose of 200 mg once daily for 6 days was selected for Phase III studies in acute bacterial skin and skin-structure infections, providing a safe dosing regimen with low potential for development of myelosuppression. Unlike linezolid, tedizolid does not inhibit monoamine oxidase in vivo, therefore interactions with adrenergic, dopaminergic, and serotonergic drugs are not to be expected. In conclusion, tedizolid is a novel antibiotic with potent activity against Gram-positive microorganisms responsible for skin and soft tissue infections, including strains resistant to vancomycin, linezolid, and daptomycin, thus answers a growing therapeutic need.

The efficacy and safety of arbekacin and vancomycin for the treatment in skin and soft tissue MRSA infection: preliminary study

Background

Methicillin-resistant Staphylococcus aureus (MRSA) has become a one of the most important causes of nosocomial infections, and use of vancomycin for the treatment of MRSA infection has increased. Unfortunately, vancomycin-resistant enterococcus have been reported, as well as vancomycin-resistant S. aureus. Arbekacin is an antibacterial agent and belongs to the aminoglycoside family of antibiotics. It was introduced to treat MRSA infection. We studied the clinical and bacteriological efficacy and safety of arbekacin compared to vancomycin in the treatment of infections caused by MRSA.

Materials and Methods

This was a retrospective case-control study of patients who were admitted to tertiary Hospital from January 1st, 2009 to December 31st, 2010, and received the antibiotics arbekacin or vancomycin. All the skin and soft tissue MRSA infected patients who received arbekacin or vancomycin were enrolled during the study period. The bacteriological efficacy response (BER) was classified with improved and failure. The improved BER was defined as no growth of MRSA, where failure was defined as growth of MRSA, culture at the end of therapy or during treatment. Clinical efficacy response (CER) was classified as improved and failure. Improved CER was defined as resolution or reduction of the majority of signs and symptoms related to the original infection. Failure was defined as no resolution and no reduction of majority of the signs and symptoms, or worsening of one or more signs and symptoms, or new symptoms or signs associated with the original infection or a new infection.

Results

Totally, 122 patients (63/99 in arbekacin, 59/168 in vancomycin group) with skin and soft tissue infection who recieved arbekacin or vancomcyin at least 4 days were enrolled and analysed. The bacteriological efficacy response [improved, arbekacin vs vancomycin; 73.0% (46/63), 95% confidence interval (CI) 60.3 to 83.4% vs 83.1% (49/59), 95% CI 71.0 to 91.6%] and clinical efficacy response [improved, arbekacin vs vancomycin; 67.2% (41/61), 95% CI 52.0 to 76.7% vs 78.0% (46/59), 95% CI 65.3 to 87.7%] were similar between the two groups (P=0.264, 0.265). The complication rate was significantly higher in the vancomycin group [29/59(49.2%), 95% CI 35.9 to 62.5%] than arbekacin [10/63(15.9%), 95% CI 8.4 to 29.0%] (P<0.001).

Conclusions

Arbekacin could be considered as an alternative antibiotics for vancomycin in skin and soft tissue infection with MRSA. However, further prospective randomized trials are needed to confirm this finding.

Microbiology of skin and soft tissue infections in the age of community-acquired methicillin-resistant Staphylococcus aureus

The objectives of this study were to determine the etiology of skin and soft-tissue infections (SSTIs) in a general population, and to describe patient characteristics, SSTI types, frequency of microbiologic testing, and the role of methicillin-resistant Staphylococcus aureus (MRSA) over time. Using electronic databases, we identified SSTI episodes and microbiologic testing among members of a large US health plan. Between 2006 and 2009, 648699 SSTI episodes were identified, of which 23% had a specimen, of which 15% were blood. A pathogen was identified in 58% of SSTI cultures. S. aureus was the most common pathogen (80% of positive cultures). Half of S. aureus isolates were MRSA. Among cellulitis and abscess episodes with a positive blood culture, 21% were methicillin-sensitive S. aureus, 16% were MRSA, 21% were beta-hemolytic streptococci and 28% were Gram negative bacteria. Between 1998 and 2009, the percentage of SSTIs for which a culture was obtained increased from 11% to 24%. In SSTI episodes with a culture-confirmed pathogen, MRSA increased from 5% in 1998 to 9% in 2001 to 42% in 2005, decreasing to 37% in 2009. These data can inform the choice of antibiotics for treatment of SSTIs.

The efficacy and safety of linezolid and glycopeptides in the treatment of Staphylococcus aureus infections

To assess the effectiveness and safety of linezolid in comparison with glycopeptides (vancomycin and teicoplanin) for the treatment of Staphylococcus aureus infections, we conducted a meta-analysis of relevant randomized controlled trials. A thorough search of Pubmed and other databases was performed. Thirteen trials on 3863 clinically assessed patients were included. Linezolid was slightly more effective than glycopeptides in the intent-to-treat population (odds ratio [OR], 1.05; 95% confidence interval [CI], 1.01–1.10), was more effective in clinically assessed patients (OR 95% CI: 1.38, 1.17–1.64) and in all microbiologically assessed patients (OR 95% CI: 1.38, 1.15–1.65). Linezolid was associated with better treatment in skin and soft-tissue infections (SSTIs) patients (OR 95% CI: 1.61, 1.22–2.12), but not in bacteraemia (OR 95% CI: 1.24, 0.78–1.97) or pneumonia (OR 95% CI: 1.25, 0.97–1.60) patients. No difference of mortality between linezolid and glycopeptides was seen in the pooled trials (OR 95% CI: 0.98, 0.83–1.15). While linezolid was associated with more haematological (OR 95% CI: 2.23, 1.07–4.65) and gastrointestinal events (OR 95% CI: 2.34, 1.53–3.59), a significantly fewer events of skin adverse effects (OR 95% CI: 0.27, 0.16–0.46) and nephrotoxicity (OR 95% CI: 0.45, 0.28–0.72) were recorded in linezolid. Based on the analysis of the pooled data of randomized control trials, linezolid should be a better choice for treatment of patients with S. aureus infections, especially in SSTIs patients than glycopeptides. However, when physicians choose to use linezolid, risk of haematological and gastrointestinal events should be taken into account according to the characteristics of the specific patient populations.

Designing antibiotic cycling strategies by determining and understanding local adaptive landscapes

The evolution of antibiotic resistance among bacteria threatens our continued ability to treat infectious diseases. The need for sustainable strategies to cure bacterial infections has never been greater. So far, all attempts to restore susceptibility after resistance has arisen have been unsuccessful, including restrictions on prescribing [1] and antibiotic cycling [2], [3]. Part of the problem may be that those efforts have implemented different classes of unrelated antibiotics, and relied on removal of resistance by random loss of resistance genes from bacterial populations (drift). Here, we show that alternating structurally similar antibiotics can restore susceptibility to antibiotics after resistance has evolved. We found that the resistance phenotypes conferred by variant alleles of the resistance gene encoding the TEM β-lactamase (bla_TEM) varied greatly among 15 different β-lactam antibiotics. We captured those differences by characterizing complete adaptive landscapes for the resistance alleles bla_TEM-50 and bla_TEM-85, each of which differs from its ancestor bla_TEM-1 by four mutations. We identified pathways through those landscapes where selection for increased resistance moved in a repeating cycle among a limited set of alleles as antibiotics were alternated. Our results showed that susceptibility to antibiotics can be sustainably renewed by cycling structurally similar antibiotics. We anticipate that these results may provide a conceptual framework for managing antibiotic resistance. This approach may also guide sustainable cycling of the drugs used to treat malaria and HIV.

Household risk factors for colonization with multidrug-resistant Staphylococcus aureus isolates

Antimicrobial resistance, particularly in pathogens such as methicillin-resistant Staphylococcus aureus (MRSA), limits treatment options and increases healthcare costs. To understand patient risk factors, including household and animal contact, potentially associated with colonization with multidrug-resistant MRSA isolates, we performed a prospective study of case patients colonized with MRSA on admission to a rural tertiary care hospital. Patients were interviewed and antimicrobial resistance patterns were tested among isolates from admitted patients colonized with MRSA in 2009-10. Prevalence of resistance was compared by case-patient risk factors and length-of-stay outcome among 88 MRSA case patients. Results were compared to NHANES 2003-04. Overall prevalence of multidrug resistance (non-susceptibility to ≥ four antimicrobial classes) in MRSA nasal isolates was high (73%) and was associated with a 1.5-day increase in subsequent length of stay (p = 0.008). History of hospitalization within the past six months, but not antimicrobial use in the same time period, was associated with resistance patterns. Within a subset of working-age case patients without recent history of hospitalization, animal contact was potentially associated with multidrug resistance. History of hospitalization, older age, and small household size were associated with multidrug resistance in NHANES data. In conclusion, recent hospitalization of case patients was predictive of antimicrobial resistance in MRSA isolates, but novel risk factors associated with the household may be emerging in CA-MRSA case patients. Understanding drivers of antimicrobial resistance in MRSA isolates is important to hospital infection control efforts, relevant to patient outcomes and to indicators of the economic burden of antimicrobial resistance.

Methicillin-resistant Staphylococcus aureus bacterial nitric-oxide synthase affects antibiotic sensitivity and skin abscess development

Staphylococcus aureus infections present an enormous global health concern complicated by an alarming increase in antibiotic resistance. S. aureus is among the few bacterial species that express nitric-oxide synthase (bNOS) and thus can catalyze NO production from L-arginine. Here we generate an isogenic bNOS-deficient mutant in the epidemic community-acquired methicillin-resistant S. aureus (MRSA) USA300 clone to study its contribution to virulence and antibiotic susceptibility. Loss of bNOS increased MRSA susceptibility to reactive oxygen species and host cathelicidin antimicrobial peptides, which correlated with increased MRSA killing by human neutrophils and within neutrophil extracellular traps. bNOS also promoted resistance to the pharmaceutical antibiotics that act on the cell envelope such as vancomycin and daptomycin. Surprisingly, bNOS-deficient strains gained resistance to aminoglycosides, suggesting that the role of bNOS in antibiotic susceptibility is more complex than previously observed in Bacillus species. Finally, the MRSA bNOS mutant showed reduced virulence with decreased survival and smaller abscess generation in a mouse subcutaneous infection model. Together, these data indicate that bNOS contributes to MRSA innate immune and antibiotic resistance phenotypes. Future development of specific bNOS inhibitors could be an attractive option to simultaneously reduce MRSA pathology and enhance its susceptibility to commonly used antibiotics.

Fatal Escherichia coli skin and soft tissue infections in liver transplant recipients: report of three cases

Gram-negative bacilli are unusual agents of skin and soft tissue infections. Most previous cases have been reported in cirrhotic or immunocompromised patients, including a single case in a liver transplant recipient. The present report describes 3 cases of fatal skin or soft tissue infections caused by Escherichia coli that occurred in the postoperative course of liver transplantation. The 3 patients were profoundly immunosuppressed as a result of pre-transplant cirrhosis and the postoperative administration of a potent immunosuppressive therapy. Skin and soft tissue infections developed within the first week after liver transplantation, while graft liver function was satisfactory. The 3 patients presented with fever and skin lesions with or without bullae. Despite prompt appropriate antibiotic therapy and surgical debridement, the outcome was rapidly fatal (24 h on average). E. coli was isolated from subcutaneous tissues in 2 cases and from several blood cultures in the third one. The 3 isolates belonged to distinct phylogenetic groups, and did not harbor most of the virulence factors usually reported in extraintestinal pathogenic E. coli isolates. Our report suggests that E. coli can cause severe skin or soft tissue infection in the postoperative course of liver transplantation. The onset of infection is very early and the outcome is extremely poor, despite prompt adapted medical and surgical treatment. Host factors, rather than E. coli bacterial virulence potential, appear to be the major determinants of severity in these patients.

Anti-infectious and anti-inflammatory effects of peptide fragments sequentially derived from the antimicrobial peptide centrocin 1 isolated from the green sea urchin, Strongylocentrotus droebachiensis

Bacterial resistance against antibiotic treatment has become a major threat to public health. Antimicrobial peptides (AMPs) have emerged as promising alternative agents for treatment of infectious diseases. This study characterizes novel synthetic peptides sequentially derived from the AMP centrocin 1, isolated from the green sea urchin, for their applicability as anti-infective agents.

The microbicidal effect of centrocin 1 heavy chain (CEN1 HC-Br), its debrominated analogue (CEN1 HC), the C-terminal truncated variants of both peptides, i.e. CEN1 HC-Br (1–20) and CEN1 HC (1–20), as well as the cysteine to serine substituted equivalent CEN1 HC (Ser) was evaluated using minimal microbicidal concentration assay. The anti-inflammatory properties were assessed by measuring the inhibition of secretion of pro-inflammatory cytokines. All the peptides tested exhibited marked microbicidal and anti-inflammatory properties. No difference in efficacy was seen comparing CEN1 HC-Br and CEN1 HC, while the brominated variant had higher cytotoxicity. C-terminal truncation of both peptides reduced salt-tolerability of the microbicidal effect as well as anti-inflammatory actions. Also, serine substitution of cysteine residue decreased the microbicidal effect. Thus, from the peptide variants tested, CEN1 HC showed the best efficacy and safety profile. Further, CEN1 HC significantly reduced bacterial counts in two different animal models of infected wounds, while Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) failed to develop resistance against this peptide under continued selection pressure. In summary, CEN1 HC appears a promising new antimicrobial agent, and clinical studies are warranted to evaluate the applicability of this AMP for local treatment of infections in man.

Staphylococcus aureus proteases degrade lung surfactant protein A potentially impairing innate immunity of the lung

The pulmonary surfactant is a complex mixture of lipids and proteins that is important for respiratory lung functions, which also provides the first line of innate immune defense. Pulmonary surfactant protein-A (SP-A) is a major surfactant component with immune functions with importance during Staphylococcus aureus infections that has been demonstrated in numerous studies. The current study showed that S. aureus can efficiently cleave the SP-A protein using its arsenal of proteolytic enzymes. This degradation appears to be mediated by cysteine proteases, in particular staphopain A (ScpA). The staphopain-mediated proteolysis of SP-A resulted in a decrease or complete abolishment of SP-A biological activity, including the promotion of S. aureus phagocytosis by neutrophils, aggregation of Gram-negative bacteria and bacterial cell adherence to epithelium. Significantly, ScpA has also efficiently degraded SP-A in complete bronchi-alveolar lavage fluid from human lungs. This indicates that staphopain activity in the lungs is resistant to protease inhibitors, thus suggesting that SP-A can be cleaved in vivo. Collectively, this study showed that the S. aureus protease ScpA is an important virulence factor that may impair innate immunity of the lungs.

A randomized trial of tigecycline versus ampicillin-sulbactam or amoxicillin-clavulanate for the treatment of complicated skin and skin structure infections

BACKGROUND

Complicated skin and skin structure infections (cSSSIs) frequently result in hospitalization with significant morbidity and mortality.

METHODS

In this phase 3b/4 parallel, randomized, open-label, comparative study, 531 subjects with cSSSI received tigecycline (100 mg initial dose, then 50 mg intravenously every 12 hrs) or ampicillin-sulbactam 1.5-3 g IV every 6 hrs or amoxicillin-clavulanate 1.2 g IV every 6-8 hrs. Vancomycin could be added at the discretion of the investigator to the comparator arm if methicillin-resistant Staphylococcus aureus (MRSA) was confirmed or suspected within 72 hrs of enrollment. The primary endpoint was clinical response in the clinically evaluable (CE) population at the test-of-cure (TOC) visit. Microbiologic response and safety were also assessed. The modified intent-to-treat (mITT) population comprised 531 subjects (tigecycline, n = 268; comparator, n = 263) and 405 were clinically evaluable (tigecycline, n = 209; comparator, n = 196).

RESULTS

In the CE population, 162/209 (77.5%) tigecycline-treated subjects and 152/196 (77.6%) comparator-treated subjects were clinically cured (difference 0.0; 95% confidence interval [CI]: -8.7, 8.6). The eradication rates at the subject level for the microbiologically evaluable (ME) population were 79.2% in the tigecycline treatment group and 76.8% in the comparator treatment group (difference 2.4; 95% CI: -9.6, 14.4) at the TOC assessment. Nausea, vomiting, and diarrhea rates were higher in the tigecycline group.

CONCLUSIONS

Tigecycline was generally safe and effective in the treatment of cSSSIs.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00368537.

Susceptibility of important Gram-negative pathogens to tigecycline and other antibiotics in Latin America between 2004 and 2010

BACKGROUND

The Tigecycline Evaluation and Surveillance Trial (T.E.S.T.) is a global surveillance study of antimicrobial susceptibility. This study reports data from Gram-negative isolates collected from centers in Latin America between 2004 and 2010.

METHODS

Consecutive bacterial isolates were tested at each center using broth microdilution methodology as described by the Clinical Laboratory Standards Institute (CLSI). Susceptibility was determined using the CLSI interpretive criteria. For tigecycline the US Federal Drug Administration (FDA) criteria were used.

RESULTS

A total of 16 232 isolates were analyzed. Susceptibility to imipenem, meropenem, and tigecycline was >95% against both non-extended-spectrum β-lactamase (ESBL) and ESBL producing Escherichia coli. Susceptibility to amikacin was also >95% for non-ESBL E. coli. 24.3% of E. coli were ESBL producers, ranging from 11.2% (58/519) in Colombia to 40.3% (31/77) in Honduras. Greater than 90% of non-ESBL Klebsiella pneumoniae were susceptible to tigecycline, carbapenems and amikacin. 35.3% of K. pneumoniae were ESBL producers, ranging from 17.2% (36/209) in Venezuela to 73.3% (55/75) in Honduras, with only imipenem and tigecycline maintaining >90% susceptibility. Greater than 90% of Klebsiella oxytoca, Enterobacter spp., and Serratia marcescens were susceptible to amikacin, carbapenems and tigecycline. The highest rates of susceptibility against Acinetobacter baumannii were seen for minocycline (89.4%) and imipenem (62.5%), while 95.8% of the A. baumannii isolates displayed an MIC≤2 μg/mL for tigecycline.

CONCLUSIONS

In this study carbapenems and tigecycline remain active against Enterobacteriaceae and A. baumannii; however, there is cause for concern with carbapenem non-susceptible isolates reported in all countries included in this study.

The novel antimicrobial peptide PXL150 in the local treatment of skin and soft tissue infections

Dramatic increase in bacterial resistance towards conventional antibiotics emphasises the importance to identify novel, more potent antimicrobial therapies. Antimicrobial peptides (AMPs) have emerged as a promising new group to be evaluated in therapeutic intervention of infectious diseases. Here we describe a novel AMP, PXL150, which demonstrates in vitro a broad spectrum microbicidal action against both Gram-positive and Gram-negative bacteria, including resistant strains. The potent microbicidal activity and broad antibacterial spectrum of PXL150 were not associated with any hemolytic activity. Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) failed to develop resistance towards PXL150 during continued selection pressure. PXL150 caused a rapid depolarisation of cytoplasmic membrane of S. aureus, and dissipating membrane potential is likely one mechanism for PXL150 to kill its target bacteria. Studies in human cell lines indicated that PXL150 has anti-inflammatory properties, which might be of additional benefit. PXL150 demonstrated pronounced anti-infectious effect in an in vivo model of full thickness wounds infected with MRSA in rats and in an ex vivo model of pig skin infected with S. aureus. Subcutaneous or topical application of the peptide in rats did not lead to any adverse reactions. In conclusion, PXL150 may constitute a new therapeutic alternative for local treatment of infections, and further studies are warranted to evaluate the applicability of this AMP in clinical settings.

Community-acquired methicillin-resistant Staphylococcus aureus from skin and soft tissue infections (in a sample of Egyptian population): analysis of mec gene and staphylococcal cassette chromosome

BACKGROUND

Staphylococcus aureus has been recognized as an important pathogen associated with inpatients and community infections. Community-acquired methicillin-resistant S. aureus (CA-MRSA) infections commonly present as skin and soft-tissue infections (SSTIs). Treatment often includes incision and drainage with or without adjunctive antibiotics.

OBJECTIVES

This study aimed to identify CA-MRSA infections both phenotypically and genotypically, to determine their spectrum of antibiotic resistance, and to establish the best scheme for molecular distinction between hospital-acquired MRSA (HA-MRSA) and CA-MRSA by staphylococcal cassette chromosome mec (SCCmec) typing and detection of Panton Valentine leukocidin (PVL).

MATERIALS

50 swabs, from skin and soft tissue of infected lesions of outpatients attending the dermatology department of the Medical School, Alexandria University, were collected. Additionally, a nasal swab was taken from every participant.

METHODS

Collection of swabs from the infected skin and soft tissues, followed by laboratory testing to phenotypically and genotypically identify MRSA. Also, nasal swabs were taken from every patient to identify MRSA colonization.

RESULTS

Staphylococcus aureus strains were identified in 38 (76%) of the 50 clinical isolates. 18 (47.37%) out of the 38 S. aureus strains were resistant to oxacillin and cefoxitin discs, were penicillin binding protein 2a (PBP2a) producers, and were initially diagnosed as MRSA. All of the 18 strains were definitively diagnosed as MRSA by mecA gene detection using real time PCR, while only six (33.33%) strains were PVL positive. Using the sets of primers of Zhang et al.: nine (50%) out of the 18 CA-MRSA strains were SCCmec type V, and one (5.56%) was SCCmec type IVc. Then, using the set of primers by Oliveira et al., two (25%) out of the eight untypable MRSA strains were found to be SCCmec type IV, and six (75%) remained untypable.

CONCLUSIONS

CA-MRSA must be considered when treating skin and soft tissue infections, especially in developing countries. Empirical use of agents active against CA-MRSA is warranted for patients presenting with serious SSTIs.

Pilot Study with regard to the Wound Healing Activity of Protein from Calotropis procera (Ait.) R. Br

We provide the scientific basis for the use of Calotropis procera for treating skin and wound infections in traditional medicine. The aqueous extract of stem-bark of C. procera exhibited more pronounced potent antimicrobial activity. Calo-protein was purified and identified from the most-active aqueous extracts of C. procera and showed broad-spectrum activity. Calo-protein inhibited the growth of S. aureus and E. aerogenes effectively at 25 μg/ml concentration. Mice topically treated with Calo-protein revealed significant wound healing after 14 days comparable to fusidic acid (FA) as positive control. This protein was devoid of cytolytic effect even at higher concentrations on skin cells after 24 h. Further investigation of this Calo-protein of C. procera on bacterial inhibition may provide a better understanding of the scientific basis and justification for its use in traditional medicine.

Detection of P. aeruginosa harboring bla CTX-M-2, bla GES-1 and bla GES-5, bla IMP-1 and bla SPM-1 causing infections in Brazilian tertiary-care hospital

Background

Nosocomial infections caused by Pseudomonas aeruginosa presenting resistance to beta-lactam drugs are one of the most challenging targets for antimicrobial therapy, leading to substantial increase in mortality rates in hospitals worldwide. In this context, P. aeruginosa harboring acquired mechanisms of resistance, such as production of metallo-beta-lactamase (MBLs) and extended-spectrum beta-lactamases (ESBLs) have the highest clinical impact. Hence, this study was designed to investigate the presence of genes codifying for MBLs and ESBLs among carbapenem resistant P. aeruginosa isolated in a Brazilian 720-bed teaching tertiary care hospital.

Methods

Fifty-six carbapenem-resistant P. aeruginosa strains were evaluated for the presence of MBL and ESBL genes. Strains presenting MBL and/or ESBL genes were submitted to pulsed-field gel electrophoresis for genetic similarity evaluation.

Results

Despite the carbapenem resistance, genes for MBLs (bla_SPM-1 or bla_IMP-1) were detected in only 26.7% of isolates. Genes encoding ESBLs were detected in 23.2% of isolates. The bla_CTX-M-2 was the most prevalent ESBL gene (19.6%), followed by bla_GES-1 and bla_GES-5 detected in one isolate each. In all isolates presenting MBL phenotype by double-disc synergy test (DDST), the bla_SPM-1 or bla_IMP-1 genes were detected. In addition, bla_IMP-1 was also detected in three isolates which did not display any MBL phenotype. These isolates also presented the bla_CTX-M-2 gene. The co-existence of bla_CTX-M-2 with bla_IMP-1 is presently reported for the first time, as like as co-existence of bla_GES-1 with bla_IMP-1.

Conclusions

In this study MBLs production was not the major mechanism of resistance to carbapenems, suggesting the occurrence of multidrug efflux pumps, reduction in porin channels and production of other beta-lactamases. The detection of bla_CTX-M-2,bla_GES-1 and bla_GES-5 reflects the recent emergence of ESBLs among antimicrobial resistant P. aeruginosa and the extraordinary ability presented by this pathogen to acquire multiple resistance mechanisms. These findings raise the concern about the future of antimicrobial therapy and the capability of clinical laboratories to detect resistant strains, since simultaneous production of MBLs and ESBLs is known to promote further complexity in phenotypic detection. Occurrence of intra-hospital clonal dissemination enhances the necessity of better observance of infection control practices.

Serratia marcescens necrotizing fasciitis presenting as bilateral breast necrosis

Serratia marcescens is an extremely rare cause of necrotizing fasciitis. We report the first case of necrotizing fasciitis of the chest wall due to infection with S. marcescens that initially manifested as bilateral breast necrosis. The patient had a fulminant course leading to death within 72 h of presentation. Literature pertinent to S. marcescens-mediated necrotizing fasciitis is also reviewed.