General microbiology and in vitro susceptibility of anaerobes isolated from complicated skin and skin-structure infections in patients enrolled in a comparative trial of ertapenem versus piperacillin-tazobactam

Efficacy of ertapenem in severe hidradenitis suppurativa: a pilot study in a cohort of 30 consecutive patients

OBJECTIVES

Hidradenitis suppurativa (HS) is an inflammatory skin disease typically localized in the axillae and inguinal and perineal areas. In the absence of standardized medical treatment, severe HS patients present chronic suppurative lesions with polymicrobial anaerobic abscesses. Wide surgery is the cornerstone treatment of severe HS, but surgical indications are limited by the extent of lesions. Intravenous broad-spectrum antibiotics may help control HS, but their efficacy is not documented. This study was designed to assess the efficacy of a 6 week course of ertapenem (1 g daily) and of antibiotic consolidation treatments for 6 months (M6) in severe HS.

PATIENTS AND METHODS

Thirty consecutive patients with severe HS were retrospectively included in this study. The clinical severity of HS was assessed using the Sartorius score, which takes into account the number and severity of lesions.

RESULTS

The median (IQR) Sartorius score dropped from 49.5 (28-62) at baseline to 19.0 (12-28) after ertapenem (P < 10(-4)). Five patients were lost to follow-up thereafter. At M6 the Sartorius score further decreased for the 16 patients who received continuous consolidation treatments, since 59% of HS areas reached clinical remission at M6 (i.e. absence of any inflammatory symptoms, P < 10(-4)). Nine patients interrupted or received intermittent consolidation treatments due to poor observance or irregular follow-up. Their Sartorius score stopped improving or returned to baseline. No major adverse event occurred.

CONCLUSIONS

Ertapenem can dramatically improve severe HS. Consolidation treatments are needed to further improve HS and are mandatory to prevent relapses. Combined with surgery, optimized antibiotic treatments may be promising in severe HS.

Antibiotic therapy for the treatment of methicillin-resistant Staphylococcus aureus (MRSA) in non surgical wounds

BACKGROUND

Non surgical wounds include chronic ulcers (pressure or decubitus ulcers, venous ulcers, diabetic ulcers, ischaemic ulcers), burns and traumatic wounds. The prevalence of methicillin-resistant Staphylococcus aureus (MRSA) colonisation (i.e. presence of MRSA in the absence of clinical features of infection such as redness or pus discharge) or infection in chronic ulcers varies between 7% and 30%. MRSA colonisation or infection of non surgical wounds can result in MRSA bacteraemia (infection of the blood) which is associated with a 30-day mortality of about 28% to 38% and a one-year mortality of about 55%. People with non surgical wounds colonised or infected with MRSA may be reservoirs of MRSA, so it is important to treat them, however, we do not know the optimal antibiotic regimen to use in these cases.

OBJECTIVES

To compare the benefits (such as decreased mortality and improved quality of life) and harms (such as adverse events related to antibiotic use) of all antibiotic treatments in people with non surgical wounds with established colonisation or infection caused by MRSA.

SEARCH METHODS

We searched the following databases: The Cochrane Wounds Group Specialised Register (searched 13 March 2013); The Cochrane Central Register of Controlled Trials (CENTRAL) (Issue 2); Database of Abstracts of Reviews of Effects (2013, Issue 2); NHS Economic Evaluation Database (2013, Issue 2); Ovid MEDLINE (1946 to February Week 4 2013); Ovid MEDLINE (In-Process & Other Non-Indexed Citations, March 12, 2013); Ovid EMBASE (1974 to 2013 Week 10); EBSCO CINAHL (1982 to 8 March 2013).

SELECTION CRITERIA

We included only randomised controlled trials (RCTs) comparing antibiotic treatment with no antibiotic treatment or with another antibiotic regimen for the treatment of MRSA-infected non surgical wounds. We included all relevant RCTs in the analysis, irrespective of language, publication status, publication year, or sample size.

DATA COLLECTION AND ANALYSIS

Two review authors independently identified the trials, and extracted data from the trial reports. We calculated the risk ratio (RR) with 95% confidence intervals (CI) for comparing the binary outcomes between the groups and planned to calculate the mean difference (MD) with 95% CI for comparing the continuous outcomes. We planned to perform the meta-analysis using both fixed-effect and random-effects models. We performed intention-to-treat analysis whenever possible.

MAIN RESULTS

We identified three trials that met the inclusion criteria for this review. In these, a total of 47 people with MRSA-positive diabetic foot infections were randomised to six different antibiotic regimens. While these trials included 925 people with multiple pathogens, they reported the information on outcomes for people with MRSA infections separately (MRSA prevalence: 5.1%). The only outcome reported for people with MRSA infection in these trials was the eradication of MRSA. The three trials did not report the review's primary outcomes (death and quality of life) and secondary outcomes (length of hospital stay, use of healthcare resources and time to complete wound healing). Two trials reported serious adverse events in people with infection due to any type of bacteria (i.e. not just MRSA infections), so the proportion of patients with serious adverse events was not available for MRSA-infected wounds. Overall, MRSA was eradicated in 31/47 (66%) of the people included in the three trials, but there were no significant differences in the proportion of people in whom MRSA was eradicated in any of the comparisons, as shown below.1. Daptomycin compared with vancomycin or semisynthetic penicillin: RR of MRSA eradication 1.13; 95% CI 0.56 to 2.25 (14 people).2. Ertapenem compared with piperacillin/tazobactam: RR of MRSA eradication 0.71; 95% CI 0.06 to 9.10 (10 people).3. Moxifloxacin compared with piperacillin/tazobactam followed by amoxycillin/clavulanate: RR of MRSA eradication 0.87; 95% CI 0.56 to 1.36 (23 people).

AUTHORS' CONCLUSIONS

We found no trials comparing the use of antibiotics with no antibiotic for treating MRSA-colonised non-surgical wounds and therefore can draw no conclusions for this population. In the trials that compared different antibiotics for treating MRSA-infected non surgical wounds, there was no evidence that any one antibiotic was better than the others. Further well-designed RCTs are necessary.

Ceftaroline in complicated skin and skin-structure infections

Ceftaroline is an advanced-generation cephalosporin antibiotic recently approved by the US Food and Drug Administration for the treatment of complicated skin and skin-structure infections (cSSSIs). This intravenous broad-spectrum antibiotic exerts potent bactericidal activity by inhibiting bacterial cell wall synthesis. A high affinity for the penicillin-binding protein 2a (PBP2a) of methicillin-resistant Staphylococcus aureus (MRSA) makes the drug especially beneficial to patients with MRSA cSSSIs. Ceftaroline has proved in multiple well-conducted clinical trials to have an excellent safety and efficacy profile. In adjusted doses it is also recommended for patients with renal or hepatic impairment. Furthermore, the clinical effectiveness and high cure rate demonstrated by ceftaroline in cSSSIs, including those caused by MRSA and other multidrug-resistant strains, warrants its consideration as a first-line treatment option for cSSSIs. This article reviews ceftaroline and its pharmacology, efficacy, and safety data to further elucidate its role in the treatment of cSSSIs.

Spore-forming Bacilli and Clostridia in human disease

Many Gram-positive spore-forming bacteria in the Firmicute phylum are important members of the human commensal microbiota, which, in rare cases, cause opportunistic infections. Other spore-formers, however, have evolved to become dedicated pathogens that can cause a striking variety of diseases. Despite variations in disease presentation, the etiologic agent is often the spore, with bacterially produced toxins playing a central role in the pathophysiology of infection. This review will focus on the specific diseases caused by spores of the Clostridia and Bacilli.

In vitro activity of ceftaroline against 623 diverse strains of anaerobic bacteria

The in vitro activities of ceftaroline, a novel, parenteral, broad-spectrum cephalosporin, and four comparator antimicrobials were determined against anaerobic bacteria. Against Gram-positive strains, the activity of ceftaroline was similar to that of amoxicillin-clavulanate and four to eight times greater than that of ceftriaxone. Against Gram-negative organisms, ceftaroline showed good activity against beta-lactamase-negative strains but not against the members of the Bacteroides fragilis group. Ceftaroline showed potent activity against a broad spectrum of anaerobes encountered in respiratory, skin, and soft tissue infections.

Community analysis of chronic wound bacteria using 16S rRNA gene-based pyrosequencing: impact of diabetes and antibiotics on chronic wound microbiota

Background

Bacterial colonization is hypothesized to play a pathogenic role in the non-healing state of chronic wounds. We characterized wound bacteria from a cohort of chronic wound patients using a 16S rRNA gene-based pyrosequencing approach and assessed the impact of diabetes and antibiotics on chronic wound microbiota.

Methodology/Principal Findings

We prospectively enrolled 24 patients at a referral wound center in Baltimore, MD; sampled patients' wounds by curette; cultured samples under aerobic and anaerobic conditions; and pyrosequenced the 16S rRNA V3 hypervariable region. The 16S rRNA gene-based analyses revealed an average of 10 different bacterial families in wounds—approximately 4 times more than estimated by culture-based analyses. Fastidious anaerobic bacteria belonging to the Clostridiales family XI were among the most prevalent bacteria identified exclusively by 16S rRNA gene-based analyses. Community-scale analyses showed that wound microbiota from antibiotic treated patients were significantly different from untreated patients (p = 0.007) and were characterized by increased Pseudomonadaceae abundance. These analyses also revealed that antibiotic use was associated with decreased Streptococcaceae among diabetics and that Streptococcaceae was more abundant among diabetics as compared to non-diabetics.

Conclusions/Significance

The 16S rRNA gene-based analyses revealed complex bacterial communities including anaerobic bacteria that may play causative roles in the non-healing state of some chronic wounds. Our data suggest that antimicrobial therapy alters community structure—reducing some bacteria while selecting for others.

The use of ertapenem for the treatment of lower extremity infections

Lower extremity infections are a growing challenge. Moderate to severe infections are frequently polymicrobial in nature and require appropriate parenteral antibiotic therapy. Ideally, empiric treatment should be broad spectrum in coverage, simplistic in use, and economically reasonable for the patient and the health care system. This article retrospectively reviewed the outcomes of 230 patients, 159 (69.13%) of whom were diabetic, who were admitted with lower extremity infections and who were empirically treated with ertapenem. Ertapenem was well tolerated with a low adverse effect profile. We found a 79.13% rate (182 of 230 patients) of favorable outcome with this regimen, which is comparable to other published studies that have looked at the use of this agent. Ertapenem is a once-daily, broad-spectrum carbapenem antibiotic indicated for the treatment of complicated skin and skin-structure infections (cSSSI). Ertapenem is an appropriate choice for empiric antibiotic therapy of lower extremity infections.

LEVEL OF CLINICAL EVIDENCE

2.

Comparative antimicrobial susceptibility of aerobic and facultative bacteria from community-acquired bacteremia to ertapenem in Taiwan

Background

Ertapenem is a once-a-day carbapenem and has excellent activity against many gram-positive and gram-negative aerobic, facultative, and anaerobic bacteria. The susceptibility of isolates of community-acquired bacteremia to ertapenem has not been reported yet. The present study assesses the in vitro activity of ertapenem against aerobic and facultative bacterial pathogens isolated from patients with community-acquired bacteremia by determining and comparing the MICs of cefepime, cefoxitin, ceftazidime, ceftriaxone, ertapenem, piperacillin, piperacillin-tazobactam, ciprofloxacin, amikacin and gentamicin. The prevalence of extended broad spectrum β-lactamases (ESBL) producing strains of community-acquired bacteremia and their susceptibility to these antibiotics are investigated.

Methods

Aerobic and facultative bacteria isolated from blood obtained from hospitalized patients with community-acquired bacteremia within 48 hours of admission between August 1, 2004 and September 30, 2004 in Chang Gung Memorial Hospital at Keelung, Taiwan, were identified using standard procedures. Antimicrobial susceptibility was evaluated by Etest according to the standard guidelines provided by the manufacturer and document M100-S16 Performance Standards of the Clinical Laboratory of Standard Institute. Antimicrobial agents including cefepime, cefoxitin, ceftazidime, ceftriaxone, ertapenem, piperacillin, piperacillin-tazobactam, ciprofloxacin, amikacin and gentamicin were used against the bacterial isolates to test their MICs as determined by Etest. For Staphylococcus aureus isolates, MICs of oxacillin were also tested by Etest to differentiate oxacillin-sensitive and oxacillin-resistant S. aureus.

Results

Ertapenem was highly active in vitro against many aerobic and facultative bacterial pathogens commonly recovered from patients with community-acquired bacteremia (128/159, 80.5 %). Ertapenem had more potent activity than ceftriaxone, piperacillin-tazobactam, or ciprofloxacin against oxacillin-susceptible S. aureus (17/17, 100%)and was more active than any of these agents against enterobacteriaceae (82/82, 100%).

Conclusion

Based on the microbiology pattern of community-acquired bacteremia, initial empiric treatment that requires coverage of a broad spectrum of both gram-negative and gram-positive aerobic bacteria, such as ertapenem, may be justified in moderately severe cases of community-acquired bacteremia in non-immunocompromised hosts.

Piperacillin-tazobactam: a beta-lactam/beta-lactamase inhibitor combination

Piperacillin-tazobactam is a beta-lactam/beta-lactamase inhibitor combination with a broad spectrum of antibacterial activity that includes Gram-positive and -negative aerobic and anaerobic bacteria. Piperacillin-tazobactam retains its in vitro activity against broad-spectrum beta-lactamase-producing and some extended-spectrum beta-lactamase-producing Enterobacteriaceae, but not against isolates of Gram-negative bacilli harboring AmpC beta-lactamases. Piperacillin-tazobactam has recently been reformulated to include ethylenediaminetetraacetic acid and sodium citrate; this new formulation has been shown to be compatible in vitro with the two aminoglycosides, gentamicin and amikacin, allowing for simultaneous Y-site infusion, but not with tobramycin. Multicenter, randomized, double-blinded clinical trials have demonstrated piperacillin-tazobactam to be as clinically effective as relevant comparator antibiotics. Clinical trials have demonstrated piperacillin-tazobactam to be effective for the treatment of patients with intra-abdominal infections, skin and soft tissue infections, lower respiratory tract infections, complicated urinary tract infections, gynecological infections and more recently, febrile neutropenia. Piperacillin-tazobactam has an excellent safety and tolerability profile and continues to be a reliable option for the empiric treatment of moderate-to-severe infections in hospitalized patients.

Update on the treatment of diabetic foot infections

This article brings the practicing clinician up to date on the current concepts regarding the medical treatment of diabetic foot infections. Topics include a review of the Infectious Diseases Society of America Practice Guidelines for the Diagnosis and Treatment of Diabetic Foot Infections and a discussion of newer antibiotics such as linezolid, ertapenem, moxifloxacin, dalbavancin, tigecycline, ceftobiprole and iclaprim.

Ertapenem: the new carbapenem 5 years after first FDA licensing for clinical practice

Ertapenem, a parenteral broad-spectrum 1-beta-methyl-carbapenem, was licensed 5 years ago for clinical practice in the US and Europe. The substance has a good in vitro activity against many common aerobic and anaerobic Gram-positive and -negative bacteria. Its in vitro activity against Enterobacteriaceae carrying plasmid- or chromosomal-mediated beta-lactamases, including AmpC- and extended-spectrum beta-lactamases, is especially clinically significant. Advantages concerning in vitro activity and low potential for so-called 'collateral damage', and development of own resistance during therapy, as shown in several randomized, controlled clinical trials, make ertapenem an excellent treatment choice for complicated aerobic and anaerobic mix infections caused by ertapenem-sensitive bacteria. On the other hand, due to its limited activity against Acinetobacter spp., enterococci and Pseudomonas aeruginosa, it is less suitable for late-onset nosocomial infections. International guidelines recommend the initial empirical use of ertapenem for intra-abdominal infections, skin and skin-structure infections, acute pelvic infections, complicated urinary tract infections and pneumonia (both community-acquired and 'early-onset' nosocomial) in a dose of 1.0 g administered once daily. However, recent results from pharmacokinetic/pharmacodynamic modelling studies in critically ill patients with ventilator-associated pneumonia and adipose volunteers with a body mass index of > or = 20 kg/m(2) showed that the standard dose of 1.0 g/day may not provide adequate free, protein-unbound drug concentrations in plasma and organ tissues. Therefore, a shortening of the dosage interval or continuous infusion of ertapenem should be considered to ensure optimal free concentrations in these particular populations.

Evaluation of the in vitro activity of ertapenem and nine other comparator agents against 337 anaerobic bacteria

Ertapenem activity in vitro was compared with that of nine reference antibiotics against 337 anaerobes by determining minimal inhibition concentrations (MICs). Amongst 246 Gram-negative anaerobes, 4, 8, 3, 4, 7, 2 and 52 strains showed resistance to ertapenem, amoxicillin/clavulanic acid, ticarcillin/clavulanic acid, piperacillin/tazobactam, cefoxitin, imipenem and clindamycin, respectively, and all strains were inhibited by metronidazole. Ertapenem MIC(50) values were 0.5, 0.25, 0.06 and <or=0.03mg/L for the Bacteroides fragilis group, Prevotella spp., fusobacteria and Gram-positive cocci, respectively. Overall resistance rates were 2.1%, 51.3%, 2.4%, 1.2%, 1.5%, 7.1%, 0.6%, 22% and 1.5% for ertapenem, amoxicillin, amoxicillin/clavulanic acid, ticarcillin/clavulanic acid, piperacillin/tazobactam, cefoxitin, imipenem, clindamycin and metronidazole, respectively. Ertapenem showed a broad spectrum and good activity against anaerobes.

Ertapenem: a review of its use in the treatment of bacterial infections

The Group 1, 1 beta-methyl carbapenem ertapenem (Invanz) is approved for parenteral use in patients with complicated intra-abdominal infection (cIAI), community-acquired pneumonia (CAP) and acute pelvic infection caused by susceptible strains of certain designated organisms in both the US and the EU. Additional approved indications in the US include complicated skin and skin structure infection (cSSSI) and complicated urinary tract infection (cUTI). Ertapenem is approved for use in adults in both the US and the EU and in paediatric patients aged >or=3 months in the US. Ertapenem has a broad spectrum of in vitro activity against Gram-negative pathogens, including extended-spectrum beta-lactamase (ESBL)- and AmpC-producing Enterobacteriaceae, Gram-positive pathogens and anaerobic pathogens. It has similar efficacy to comparator antibacterials such as piperacillin/tazobactam in cSSSI (including diabetic foot infection), cIAI and acute pelvic infection and ceftriaxone with or without metronidazole in cIAI, cUTI and CAP. The drug has also shown efficacy in the treatment of paediatric patients with complicated community-acquired bacterial infections. Ertapenem has a convenient once-daily administration schedule and is generally well tolerated. Thus, ertapenem is an important option for the empirical treatment of complicated community-acquired bacterial infections in hospitalised patients.

Antimicrobial Management of Complicated Skin and Skin Structure Infections in the Era of Emerging Resistance

BACKGROUND

Complicated skin and skin structure infections (cSSSIs) are among the most common infections treated in the hospital setting. The mainstays of treatment continue to be antimicrobial therapy combined with appropriate surgical intervention. Due to increasing resistance among pathogens commonly implicated in cSSSIs, the objectives of this review were to describe the potential pathogens causing skin infections, the implications of resistance to currently used drug therapy, and the role of new antibiotics with activity for pathogens causing cSSSIs.

METHODS

Relevant information from the primary literature and review articles were identified through a MEDLINE search of the medical literature (1980 to the present) using the terms abscess, wound infection, skin and skin structure infection, antibiotics, resistance, quinupristin- dalfopristin, linezolid, daptomycin, tigecycline, oritavancin, and dalbavancin. Meeting posters and slides were identified from the Interscience Conference of Antimicrobial Agents and Chemotherapy (1998-2004) for supplemental data.

RESULTS

The most commonly implicated pathogens in cSSSIs include gram-positive bacteria, specifically Staphylococcus aureus. Gram-negative and mixed organisms are additionally encountered in serious cSSSI. Antimicrobial resistance among both gram-positive and gramnegative bacteria has increased significantly during the last decade, with methicillin resistance among S. aureus approaching 60% in hospitals and becoming more frequent in the community as well. As a result, resistance is the driving factor for treatment failure and rising costs for infection management. Few antimicrobial agents are available currently to treat resistant bacteria in cSSSIs; vancomycin is currently the drug of choice against resistant grampositive cocci; however, resistance to this agent has appeared in enterococci and S. aureus. Several new antibiotics such as linezolid and daptomycin are now available for the management of cSSSIs. Other agents such as tigecycline are under investigation and should be available soon to increase treatment options for cSSSIs caused by resistant bacteria.

CONCLUSIONS

Although the resistance of cSSSI pathogens is problematic, new antibiotics with broad-spectrum activity against resistant gram-positive and gram-negative bacteria are promising for the management of severe cSSSIs.

Ertapenem: review of a new carbapenem

The carbapenems are beta-lactam-type antibiotics with an exceptionally broad spectrum of activity. Ertapenem is a new carbapenem developed to address the pharmacokinetic shortcomings (short half-life) of imipenem and meropenem. Ertapenem shares similar structural features with meropenem, including its stability to dehydropeptidase-1, allowing it to be administered without a dehydropeptidase-1 inhibitor. Ertapenem, like imipenem and meropenem, demonstrates broad-spectrum antimicrobial activity against many Gram-positive and -negative aerobes and anaerobes and is resistant to nearly all beta-lactamases, including extended-spectrum beta-lactamases and AmpCs. However, it differs from both imipenem and meropenem in demonstrating limited activity against Enterococcusspp., Pseudomonasaeruginosa and other nonfermentative Gram-negative bacteria commonly associated with nosocomial infections. The extensive protein binding of ertapenem extends the half-life and allows for once-daily dosing. Prospective, multicenter, randomized, double-blind, comparative clinical studies demonstrate similar clinical efficacy of ertapenem compared with other agents. Clinical trials of complicated intra-abdominal infection, acute pelvic infection, complicated skin and soft-structure infection, community-acquired pneumonia and complicated urinary tract infections demonstrated that ertapenem has equivalent efficacy and safety compared with ceftriaxone and piperacillin/tazobactam. Ertapenem is a promising new carbapenem with excellent efficacy and safety for the treatment of a variety of community-acquired infections. It also appears to be of great value as an outpatient parenteral antimicrobial therapy.

Ertapenem: a review of its use in the management of bacterial infections

Ertapenem, a carbapenem antibacterial, has in vitro activity against many Gram- negative (including Enterobacteriaceae) and Gram-positive aerobic and anaerobic bacteria that are commonly associated with various infections.Once-daily parenteral (intravenous or intramuscular) ertapenem 1g was as effective as comparator antimicrobial agents (piperacillin/tazobactam or ceftriaxone +/- metronidazole) in patients with bacterial infections in randomised, double-blind, multicentre clinical trials. Response rates with ertapenem were 84% and 87% (combined microbiological and clinical) in patients with complicated intra-abdominal infections (CIAI), 82% (clinical) in patients with complicated skin and skin structure infections (CSSSI), 86% and 92% (microbiological) in patients with complicated urinary tract infections (CUTI), 92% (clinical) in patients with community-acquired pneumonia (CAP) associated with typical pathogens and 94% (clinical) in patients with acute pelvic infection. Respective response rates were statistically equivalent to those with comparators (81-94%). The efficacy of ertapenem was equivalent to that of piperacillin/tazobactam in patients infected with Enterobacteriaceae or anaerobes and to ceftriaxone in patients infected with Enterobacteriaceae. Ertapenem was generally well tolerated by patients with bacterial infections, with most adverse events being mild to moderate in severity. The most common ertapenem-associated adverse events were diarrhoea, infused vein complication, nausea, headache, vaginitis in females, phlebitis and/or thrombophlebitis and vomiting.

CONCLUSION

Ertapenem is a broad-spectrum parenteral antibiotic with activity against many Gram-negative (including Enterobacteriaceae) and Gram-positive aerobic and anaerobic bacteria and is suitable for once-daily administration. Ertapenem has a role in the treatment of CAP associated with typical respiratory pathogens and is of particular value in the treatment of polymicrobial infections (such as CIAI, CSSSI, CUTI and acute pelvic infections), especially where Enterobacteriaceae and anaerobic bacteria are involved.

Comparative in vitro activities of ertapenem against aerobic and facultative bacterial pathogens from patients with complicated skin and skin structure infections

This study compared the in vitro activities of ertapenem (Merck & Co., Inc.), ceftriaxone, amoxicillin-clavulanate, and piperacillin-tazobactam against 518 aerobic and facultative bacterial pathogens isolated from 340 patients with complicated skin and skin structure infections. Ciprofloxacin was also tested against Gram-negative isolates. Gram-positive cocci accounted for 68.1% of the aerobic bacteria; Staphylococcus aureus was the most common isolate (45.6%). The ertapenem MIC was < or = 2 microg/ml for 80.9% of isolates and > or = 8 microg/ml for 16.2% (including isolates of enterococci, methicillin-resistant S. aureus, Pseudomonas aeruginosa, and other nonfermentative Gram-negative bacteria). Against methicillin-susceptible S. aureus, ertapenem had the most potent activity. Ertapenem was the most active drug against Enterobacteriaceae (100% susceptible), whereas amoxicillin-clavulanate was least active (66% susceptible). Piperacillin-tazobactam was the most active drug against P. aeruginosa (100% susceptible), followed by ciprofloxacin (87% susceptible). In summary, ertapenem was highly active in vitro against many aerobic and facultative bacterial pathogens commonly recovered from patients with complicated skin and skin structure infections.