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

Clinical efficacy of oral linezolid compared with intravenous vancomycin for the treatment of methicillin-resistant Staphylococcus aureus-complicated skin and soft tissue infections: a retrospective, propensity score-matched, case-control analysis

BACKGROUND

Linezolid is 100% bioavailable in oral and intravenous formulations. In a recent prospective, randomized, open-label, comparator-controlled, multicenter, phase 4 clinical trial in adults with complicated skin and soft tissue infections (cSSTIs) caused by methicillin-resistant Staphylococcus aureus (MRSA), linezolid achieved clinical and microbiologic success comparable to appropriately dosed intravenous vancomycin. Although patients were randomly assigned to receive linezolid or vancomycin, the protocol allowed patients to start therapy using oral or intravenous linezolid on the basis of investigator discretion and patient ability to tolerate oral medication.

OBJECTIVE

The objective of this study was to assess the efficacy and tolerability of linezolid when administered orally in adults with cSSTI caused by MRSA. In this retrospective analysis, we examined data collected from the aforementioned trial to compare outcomes in patients who received either oral linezolid or intravenous vancomycin therapy.

METHODS

This study analyzed outcomes in patients who received treatment for 7 to 14 days with either oral linezolid (600 mg q12h; n = 95) or intravenous vancomycin (15 mg/kg q12h, adjusted for creatinine clearance and trough concentration; n = 210). By design, these groups were not randomized. Propensity score matching on baseline variables was used to balance these groups by identifying a comparable group of patients who received vancomycin therapy and comparing them with patients who received oral linezolid therapy. Clinical and microbiologic success rates at the end of treatment and the end of the study (EOS) were then directly compared between the groups using matched-pair logistic regression. The tolerability of the 2 treatments (within this matched group) was also described.

RESULTS

Ninety-two patients with well-matched baseline characteristics were included in each treatment group. At EOS, the odds ratio for clinical success of oral linezolid therapy vs intravenous vancomycin therapy was 4.0 (95% CI, 1.3-12.0; P = 0.01), and the odds ratio for microbiologic success at EOS was 2.7 (95% CI, 1.2-5.7; P = 0.01). Overall rates of adverse events in each group were consistent with reported safety profiles for each drug.

CONCLUSION

A favorable clinical cure rate was achieved with oral linezolid therapy when compared with intravenous vancomycin therapy in propensity score-matched patients with cSSTI proved to be caused by MRSA. ClinicalTrials.gov Identifier: NCT00087490.

Molecular and phenotypic characteristics of healthcare- and community-associated methicillin-resistant Staphylococcus aureus at a rural hospital

Background

While methicillin-resistant Staphylococcus aureus (MRSA) originally was associated with healthcare, distinct strains later emerged in patients with no prior hospital contact. The epidemiology of MRSA continues to evolve.

Methods

To characterize the current epidemiology of MRSA-colonized patients entering a hospital serving both rural and urban communities, we interviewed patients with MRSA-positive admission nasal swabs between August 2009 and March 2010. We applied hospitalization risk factor, antimicrobial resistance phenotype, and multi-locus sequence genotype (MLST) classification schemes to 94 case-patients.

Results

By MLST analysis, we identified 15 strains with two dominant clonal complexes (CCs)–CC5 (51 isolates), historically associated with hospitals, and CC8 (27 isolates), historically of community origin. Among patients with CC5 isolates, 43% reported no history of hospitalization within the past six months; for CC8, 67% reported the same. Classification by hospitalization risk factor did not correlate strongly with genotypic classification. Sensitivity of isolates to ciprofloxacin, clindamycin, or amikacin was associated with the CC8 genotype; however, among CC8 strains, 59% were resistant to ciprofloxacin, 15% to clindamycin, and 15% to amikacin.

Conclusions

Hospitalization history was not a strong surrogate for the CC5 genotype. Conversely, patients with a history of hospitalization were identified with the CC8 genotype. Although ciprofloxacin, clindamycin, and amikacin susceptibility distinguished CC8 strains, the high prevalence of ciprofloxacin resistance limited its predictive value. As CC8 strains become established in healthcare settings and CC5 strains disseminate into the community, community-associated MRSA definitions based on case-patient hospitalization history may prove less valuable in tracking community MRSA strains.

In vitro activity and microbiological efficacy of tedizolid (TR-700) against Gram-positive clinical isolates from a phase 2 study of oral tedizolid phosphate (TR-701) in patients with complicated skin and skin structure infections

Tedizolid (TR-700, formerly torezolid) is the active moiety of the prodrug tedizolid phosphate (TR-701), a next-generation oxazolidinone, with high potency against Gram-positive species, including methicillin-resistant Staphylococcus aureus (MRSA). A recently completed randomized, double-blind phase 2 trial evaluated 200, 300, or 400 mg of oral tedizolid phosphate once daily for 5 to 7 days in patients with complicated skin and skin structure infections. This report examines the in vitro activity of tedizolid and Zyvox (linezolid) against Gram-positive pathogens isolated at baseline and describes the microbiological and clinical efficacy of tedizolid. Of 196 isolates tested, 81.6% were S. aureus, and of these, 76% were MRSA. The MIC(50) and MIC(90) of tedizolid against both methicillin-susceptible S. aureus (MSSA) and MRSA were 0.25 μg/ml, compared with a MIC(50) of 1 μg/ml and MIC(90) of 2 μg/ml for linezolid. For coagulase-negative staphylococci (n = 7), viridans group streptococci (n = 15), and beta-hemolytic streptococci (n = 3), the MICs ranged from 0.03 to 0.25 μg/ml for tedizolid and from 0.12 to 1 μg/ml for linezolid. The microbiological eradication rates at the test-of-cure visit (7 to 14 days posttreatment) in the microbiologically evaluable population (n = 133) were similar in all treatment groups, with overall eradication rates of 97.7% for all pathogens, 97.9% for MRSA, and 95.7% for MSSA. The clinical cure rates for MRSA and MSSA infections were 96.9% and 95.7%, respectively, across all dose groups. This study confirms the potent in vitro activity of tedizolid against pathogenic Gram-positive cocci, including MRSA, and its 4-fold-greater potency in comparison with linezolid. All dosages of tedizolid phosphate showed excellent microbiological and clinical efficacy against MRSA and MSSA.

Life-threatening Escherichia coli cellulitis in patients with haematological malignancies

Cellulitis due to Escherichia coli is rare and usually secondary to a cutaneous portal of entry. Skin and soft tissue infections (SSTI) secondary to E. coli bacteraemia have been reported exclusively in immunodeficient patients. Here, we report two cases of serious cellulitis secondary to E. coli bacteraemia in patients with haematological malignancies. Both isolated strains belonged to phylogenetic group B2 and harboured some of the main virulence factor genes commonly found in extra-intestinal pathogenic E. coli (ExPEC), including neuC, iro and fimH. Cellulitis due to E. coli seems to be linked to the immunocompromised status of patients rather than to a highly virulent clone. Nevertheless, some of the virulence factors appear to be important because both isolates belong to phylogenetic group B2. This aetiology should be considered in SSTI in patients with haematological malignancies.

Efficacy of human simulated exposures of ceftaroline against phenotypically diverse Enterobacteriaceae isolates

Ceftaroline fosamil, a new broad-spectrum cephalosporin, exhibits potent bactericidal activity against common Gram-negative pathogens, including Enterobacteriaceae, and Gram-positive pathogens, including methicillin-resistant Staphylococcus aureus and penicillin-resistant Streptococcus pneumoniae. The purpose of this study was to evaluate the efficacy of a human simulated dose of ceftaroline fosamil against clinical Enterobacteriaceae in both neutropenic and immunocompetent mouse thigh infection models. Thirty-five Enterobacteriaceae isolates with ceftaroline MICs ranging from 0.25 to 32 μg/ml were selected for the neutropenic model, and five Escherichia coli isolates were also tested in the immunocompetent model. Two hours after inoculation, the ceftaroline fosamil human simulated regimen of 600 mg intravenously (i.v.) every 12 h was administered. The change in log(10) CFU after 24 h was compared to that in 0 h controls. The human simulated regimen produced predictable efficacy against 18 of 20 isolates with a MIC of ≤ 1 μg/ml. Similar efficacy was seen in the immunocompetent model against isolates with a MIC of ≤ 2 μg/ml, and enhanced efficacy was observed against the isolate with a MIC of 4 μg/ml. Human simulated exposures to ceftaroline fosamil at 600 mg every 12 h provided predictable efficacy against Enterobacteriaceae with MICs of ≤ 1 μg/ml and enhanced efficacy within the immunocompetent model, supporting the clinical utility of ceftaroline fosamil against these organisms.

The iron-regulated staphylococcal lipoproteins

Lipoproteins fulfill diverse roles in antibiotic resistance, adhesion, protein secretion, signaling and sensing, and many also serve as the substrate binding protein (SBP) partner to ABC transporters for the acquisition of a diverse array of nutrients including peptides, sugars, and scarcely abundant metals. In the staphylococci, the iron-regulated SBPs are significantly upregulated during iron starvation and function to sequester and deliver iron into the bacterial cell, enabling staphylococci to circumvent iron restriction imposed by the host environment. Accordingly, this subset of lipoproteins has been implicated in staphylococcal pathogenesis and virulence. Lipoproteins also activate the host innate immune response, triggered through Toll-like receptor-2 (TLR2) and, notably, the iron-regulated subset of lipoproteins are particularly immunogenic. In this review, we discuss the iron-regulated staphylococcal lipoproteins with regard to their biogenesis, substrate specificity, and impact on the host innate immune response.

Trends and characteristics of culture-confirmed Staphylococcus aureus infections in a large U.S. integrated health care organization

Infections due to Staphylococcus aureus present a significant health problem in the United States. Between 1990 and 2005, there was a dramatic increase in community-associated methicillin-resistant S. aureus (MRSA), but recent reports suggest that MRSA may be declining. We retrospectively identified S. aureus isolates (n = 133,450) that were obtained from patients in a large integrated health plan between 1 January 1998 and 31 December 2009. Trends over time in MRSA were analyzed, and demographic risk factors for MRSA versus methicillin-susceptible S. aureus (MSSA) were identified. The percentage of S. aureus isolates that were MRSA increased from 9% to 20% between 1998 and 2001 and from 25% to 49% between 2002 and 2005 and decreased from 49% to 43% between 2006 and 2009. The increase in MRSA was seen in blood and in other bacteriological specimens and occurred in all age and race/ethnicity groups, though it was most pronounced in persons aged 18 to <50 years and African-Americans. Hospital onset infections were the most likely to be MRSA (odds ratio [OR], 1.58; confidence interval [CI], 1.46 to 1.70, compared to community-associated cases), but the largest increase in MRSA was in community-associated infections. Isolates from African-Americans (OR, 1.73; CI, 1.64 to 1.82) and Hispanics (OR, 1.11; CI, 1.06 to 1.16) were more likely to be MRSA than those from whites. After substantial increases between 1998 and 2005 in the proportion of S. aureus isolates that were MRSA, the proportion decreased between 2006 and 2009. Hospital onset S. aureus infections are disproportionately MRSA, as are those among African-Americans.

Colicin insensitivity correlates with a higher prevalence of extraintestinal virulence factors among Escherichia coli isolates from skin and soft-tissue infections

Colicins are toxic proteins with a narrow killing spectrum that are produced by colicinogenic Escherichia coli strains. The aim of this study was to analyse systematically whether extra-intestinal virulence potential is linked to colicin (in)sensitivity. In total, 102 well-characterized E. coli isolates from skin and soft-tissue infections (SSTIs) were exposed to 17 single-colicin-producing strains, and the correlation between insensitivity to colicin and phylogenetic group as well as the extra-intestinal virulence potential of the SSTI strains was examined. The results showed that SSTI strains belonging to the B2 phylogenetic group were statistically significantly associated with insensitivity to at least ten colicins, and several colicin insensitivities were correlated with virulence factors. As far as is known, this is the first study to report such correlations.

Skin and soft tissue infections in patients with solid tumours

BACKGROUND

Skin and soft tissue infections (SSTIs) in cancer patients represent a diagnostic challenge, as etiologic diagnosis is often missing, and clinical assessment of severity is difficult. Few studies have described (SSTIs) in patients with solid tumours (STs).

PATIENTS AND METHODS

Records of patients with ST and SSTI, cared for at the University Hospital of Heraklion, from 2002 to 2006 were retrospectively studied. Results. A total of 81 episodes of SSTIs, occurring in 71 patients with ST, have been evaluated. Their median age was 65 years (34-82). The most common underlying malignancy was breast cancer in 17 patients (24%). Most episodes (89%) occurred in nonneutropenics. Cellulitis/erysipelas was the most common clinical presentation (56; 69%). Bacterial cultures were possible in 29 (36%) patients. All patients received antimicrobial therapy, while in 17 episodes (21%) an incision and drainage was required. Treatment failure occurred in 20 episodes (25%). Five patients (7%) died due to sepsis. None was neutropenic. Severe sepsis on admission (P = 0.002) and prior blood transfusion (P = 0.043) were independent predictors of treatment failure.

CONCLUSION

SSTIs can be life threatening among patients with ST. Early diagnosis and appropriate treatment are of the utmost importance, since sepsis was proven a significant factor of unfavourable outcome.

Clinical and bacteriological survey of diabetic foot infections in Lisbon

AIMS

An epidemiological survey of diabetic foot infections (DFIs) in Lisbon, stratifying the bacterial profile based on patient demographical data, diabetic foot characteristics (PEDIS classification), ulcer duration and antibiotic therapy.

METHODS

A transversal observational multicenter study, with clinical data collection using a structured questionnaire and microbiological products (aspirates, biopsies or swabs collected using the Levine method) of clinically infected foot ulcers of patients with diabetes mellitus (DM).

RESULTS

Forty-nine hospitalized and ambulatory patients were enrolled in this study, and 147 microbial isolates were cultured. Staphylococcus was the main genus identified, and methicillin-resistant Staphylococcus aureus (MRSA) was present in 24.5% of total cases. In the clinical samples collected from patients undergoing antibiotic therapy, 93% of the antibiotic regimens were considered inadequate based on the antibiotic susceptibility test results. The average duration of an ulcer with any isolated multi-drug resistant (MDR) organism was 29 days, and previous treatment with fluoroquinolones was statistically associated with multi-drug resistance.

CONCLUSIONS

Staphylococcus aureus was the most common cause of DFIs in our area. Prevalence and precocity of MDR organisms, namely MRSA, were high and were probably related to previous indiscriminate antibiotic use. Clinicians should avoid fluoroquinolones and more frequently consider the use of empirical anti-MRSA therapy.

A systematic review of bacteremias in cellulitis and erysipelas

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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

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

Sepsis with multiple abscesses after massive autologous fat grafting for augmentation mammoplasty: a case report

BACKGROUND

Autologous fat grafting to the breast for breast reconstruction and cosmetic breast augmentation has gained much attention recently. However, its efficacy and the severities of its associated complications are of concern. The authors experienced one case of multiple breast abscesses after augmentation mammoplasty by autologous fat grafting.

METHODS

A 42-year-old woman presented to the authors' emergency department reporting tenderness, swelling, and a sensation of heat in both breasts. The patient had undergone augmentation mammoplasty by autologous fat grafting 7 days previously. Abscess formation was suspected based on the patient's history, physical examination, laboratory findings, and image study.

RESULTS

Incision and drainage were performed immediately with the patient under general anesthesia, and 500 ml of a foul, brown, turbid, purulent fluid containing necrotic fat debris was drained from each breast. Empiric antibiotics were started on the first hospital day, and betadine and saline-irrigation were administered daily for 2 weeks. Incisions were closed on hospital day 19 when laboratory data and local infection signs had improved. At the patient's 9-month follow-up assessment, breast contours were found to be well preserved, and scarring was minimal.

CONCLUSION

Immediate complications such as edema, hematoma, and infection require serious consideration after autologous fat grafting in the breast. In particular, infection probably is the most serious complication because the volume of the fat injected is large and can induce systemic infections such as sepsis and distort the contours of the breast. To avoid such infections, systemic and multicenter studies are required to determine how fat grafting should be performed to minimize the risks of fat necrosis and infection.

Treatment of skin and soft tissue infections in the elderly: A review

BACKGROUND

Skin and soft tissue infections (SSTIs) have become the second most common type of infection among persons residing in long-term care facilities.

OBJECTIVE

The purpose of this article was to review the latest information on SSTIs among the elderly, including age-related changes, challenges, and treatment strategies in the era of emerging bacterial resistance.

METHODS

Relevant information was identified through a search of MEDLINE (1970-April 2010), International Pharmaceutical Abstracts (1970-April 2010), and Google Scholar using the terms skin and soft tissue infection, skin and skin structure infection, cellulitis, treatment guidelines, and elderly. Additional publications were found by searching the reference lists of the identified articles. Trials published since 1970 were selected for this review if they prospectively evaluated mostly adults (≥18 years of age), included >50 patients, and reported diagnostic criteria as well as clinical outcomes in patients treated for simple or complicated SSTIs.

RESULTS

Fifty-eight of 664 identified studies were selected and included in this review. A search of the literature did not identify any prospective clinical trials that were conducted exclusively in the elderly. Information on the treatment of SSTIs in the elderly was based solely on clinical studies that were conducted in adults in general. As recommended by the Infectious Diseases Society of America (IDSA) 2008 update, SSTIs should be suspected in elderly patients who have skin lesions and present with a decline in functional status, with or without fever. Patients who present with symptoms of systemic toxicity should be hospitalized for further evaluation. Current challenges in the management of SSTIs include the rapid emergence of community-acquired, methicillin-resistant Staphylococcus aureus (CA-MRSA), the emergence of macrolide-resistant streptococci within the past decade, and the lack of a reliable algorithm to differentiate potentially life-threatening SSTIs that require aggressive interventions and prompt hospitalization from those that can be managed in an outpatient setting. S aureus was the most common cause of SSTIs, being isolated in 42.8% (5015/11,723) of wounds, followed by streptococci. Common SSTIs in the elderly such as shingles, diabetic foot infections, infected pressure ulcers, and scabies, and their treatment were also discussed. Based on reviews of published trials, treatment of simple SSTIs generally consisted of administration of agents with activity against S aureus and Streptococcus species such as a penicillinase-resistant β-lactam, a first-generation cephalosporin, or clindamycin. Broadening of the antimicrobial spectrum to include gram-negative and anaerobic organisms should be implemented for complicated SSTIs such as diabetic foot infections and infected pressure ulcers. Local rates of MRSA, CA-MRSA, and macrolide-resistant streptococci should be considered when selecting empiric therapy.

CONCLUSIONS

A search of the literature did not identify any prospective clinical trials on the treatment of SSTIs in the elderly; therefore, it is recommended to follow treatment based on the current IDSA guidelines. More research and publications are needed to establish proper selection of antimicrobial agents, treatment strategies, and duration of therapy of SSTIs in the elderly population.

Multiresistant Gram-negative infections: a global perspective

PURPOSE OF REVIEW

Multiresistant Gram-negative infections are an increasing problem in hospitals and healthcare facilities worldwide. While much attention has been paid to Gram-positive pathogens such as methicillin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus lately, the importance of Gram-negative nosocomial infections has also been recognized globally.

RECENT FINDINGS

Recent reports have described the spread of carbapenemase-producing Klebsiella pneumoniae across North America. In addition, many strains of Pseudomonas and Acinetobacter in Asia are resistant to all known antibiotics. The global epidemiology of multiresistant Gram-negative pathogens seems to vary by continent. There are very few existing agents which can be used for these pathogens and there are limited options on the horizon. This limited therapeutic armamentarium has been an impetus for novel approaches including combination therapies and increased attention to infection control and prevention efforts.

SUMMARY

Clinicians need to be aware of the rising problem of resistance in nosocomial and community-acquired Gram-negative pathogens. Novel agents are urgently needed to combat these infections and innovative infection control strategies need to be devised to protect our vulnerable patients.

Telavancin Activity against gram-positive bacteria isolated from patients with skin and skin-structure infections

Telavancin is approved in the United States and Canada for the treatment of complicated skin and skin structure infections (cSSSI) in adults caused by susceptible Gram-positive organisms. The antimicrobial activity of telavancin and comparators was evaluated against 5,027 (2007-2008) Gram-positive bacteria responsible for SSSI in medical centers in Asia-Pacific, European, Latin American, and North American regions. Telavancin was active against Staphylococcus aureus (MIC₅₀(/)₉₀, 0.12/0.25 mg/l; 100.0% susceptible) and coagulase-negative staphylococci (MIC₅₀(/)₉₀, 0.12/0.25 mg/l). telavancin inhibited all Enterococcus faecalis, including four strains displaying a VanB phenotype, at ≤ 1 mg/L (MIC₅₀(/)₉₀, 0.25/0.5 mg/l), except for two isolates with a VanA phenotype (MIC, >2 mg/l). Vancomycin-susceptible and VanB vancomycin-resistant E. faecium were inhibited by telavancin at ≤ 0.25 mg/L, while this drug exhibited elevated MIC values (≥ 0.5 mg/l) against E. faecium of VanA phenotype (MIC₅₀(/)₉₀, 2/>2 mg/l). Telavancin was potent against β-haemolytic streptococci (MIC₅₀(/)₉₀, 0.03/0.12 mg/l; 100.0% susceptible) and viridans group streptococci (MIC₅₀(/)₉₀, 0.03/0.06 mg/l; 100.0% susceptible). These in vitro data document the activity of telavancin against contemporary Gram-positive isolates and support its clinical use for the treatment of cSSSI caused by the indicated pathogens.

Complicated skin and soft tissue infection

Skin and soft tissue infections (SSTIs) are common, and complicated SSTIs (cSSTIs) are the more extreme end of this clinical spectrum, encompassing a range of clinical presentations such as deep-seated infection, a requirement for surgical intervention, the presence of systemic signs of sepsis, the presence of complicating co-morbidities, accompanying neutropenia, accompanying ischaemia, tissue necrosis, burns and bites. Staphylococcus aureus is the commonest cause of SSTI across all continents, although its epidemiology in terms of causative strains and antibiotic susceptibility can no longer be predicted with accuracy. The epidemiology of community-acquired and healthcare-acquired strains is constantly shifting and this presents challenges in the choice of empirical antibiotic therapy. Toxin production, particularly with Panton-Valentine leucocidin, may complicate the presentation still further. Polymicrobial infection with Gram-positive and Gram-negative organisms and anaerobes may occur in infections approximating the rectum or genital tract and in diabetic foot infections and burns. Successful management of cSSTI involves prompt recognition, timely surgical debridement or drainage, resuscitation if required and appropriate antibiotic therapy. The mainstays of treatment are the penicillins, cephalosporins, clindamycin and co-trimoxazole. β-Lactam/β-lactamase inhibitor combinations are indicated for polymicrobial infection. A range of new agents for the treatment of methicillin-resistant S. aureus infections have compared favourably with the glycopeptides and some have distinct pharmacokinetic advantages. These include linezolid, daptomycin and tigecycline. The latter and fluoroquinolones with enhanced anti-Gram-positive activity such as moxifloxacin are better suited for polymicrobial infection.

Retrospective Analysis of Clinical and Cost Outcomes Associated with Methicillin-Resistant Staphylococcus aureus Complicated Skin and Skin Structure Infections Treated with Daptomycin, Vancomycin, or Linezolid

Objective. The objective of this analysis was to compare clinical and cost outcomes associated with patients who had suspected or documented methicillin-resistant Staphylococcus aureus (MRSA) infections treated with daptomycin, vancomycin, or linezolid in complicated skin and skin structure infections (cSSSIs). Design. This was a retrospective analysis conducted from February to June of 2007. Appropriate data was collected, collated, and subsequently evaluated with the purpose of quantifying length of stay, antibiotic therapy duration, clinical cure rates, adverse drug events, and cost of hospitalization. Results. All 82 patients included in the analysis experienced clinical cure. The duration of antibiotic therapy was similar among the three groups yet the length of hospitalization was slightly shorter in the daptomycin group. Conclusions. The incidence of resistant staphylococcal infections is increasing; therefore, judicious use of MRSA active agents is paramount. Future studies are necessary to determine if MRSA treatment options can be stratified based on the severity of the infectious process.

Surveillance of antimicrobial resistance in resource-constrained settings - experience from five pilot projects

OBJECTIVE

The rapid increase in antimicrobial resistance (AMR) among bacteria is a major public health concern. The WHO Global Strategy for Containment of Antimicrobial Resistance proposed that model systems be developed for AMR surveillance and for monitoring antimicrobial use.

METHODS

Pilot projects were established in three sites in India and two in South Africa to collect monthly AMR data on target bacteria for at least 12 months. Escherichia coli was used as the target bacterium in four sites (three in India, one in South Africa). One South African site used Streptococcus pneumoniae and Haemophilus influenzae. Each site sought to obtain at least 960 isolates per year. Resistance was determined by disc diffusion or minimum inhibitory concentration (MIC) methods.

RESULTS

Data were collected for 12 and 16 months respectively in the South African sites and for 14 months in one Indian site and 24 months in the other two. All sites found difficulty collecting the required number of isolates, with three sites failing to do so. Escherichia coli isolates were more easily obtained and two sites developed methods to increase their yield. Disc diffusion testing provided more timely and reliable AMR data than did MIC determinations. Although methodological issues limit the comparability of data, high AMR rates were observed at all five sites.

CONCLUSION

All five pilot sites provided data on AMR, but also raised several issues related to logistics of long-term surveillance in settings under resource constraints. For surveillance of AMR in such settings, E. coli is probably the best indicator bacterium.

Treatment of complicated skin and soft-tissue infections caused by resistant bacteria: value of linezolid, tigecycline, daptomycin and vancomycin

Antibiotic-resistant organisms causing both hospital- and community-acquired complicated skin and soft-tissue infections (cSSTI) are increasingly reported. A substantial medical and economical burden associated with MRSA colonisation or infection has been documented. The number of currently available appropriate antimicrobial agents is limited. Good quality randomised, controlled clinical trial data on antibiotic efficacy and safety is available for cSSTI caused by MRSA. Linezolid, tigecycline, daptomycin and vancomycin showed efficacy and safety in MRSA-caused cSSTI. None of these drugs showed significant superiority in terms of clinical cure and eradication rates.To date, linezolid offers by far the greatest number of patients included in controlled trials with a strong tendency of superiority over vancomycin in terms of eradication and clinical success.. - Tigecycline is an alternative in polymicrobial infections except by diabetic foot infections. Daptomycin might be a treatment option for cases of cSSTI with MRSA bacteremia. cSSTI caused by resistant Gram-negative bacteria are a matter of great concern. The development of new antibiotics in this area is an urgent priority to avoid the risk of a postantibiotic era with no antimicrobial treatment options. An individual approach for every single patient is mandatory to evaluate the optimal antimicrobial treatment regimen.

Role of telavancin in treatment of skin and skin structure infections

Skin and skin structure infections (SSSIs) are a common diagnosis encountered by ambulatory and inpatient practitioners across the country. As the SSSIs become more complicated, they require increased health care resources and often involve hospitalization and intravenous antimicrobials. Complicated SSSIs are caused by a variety of pathogens, including Gram-positive, Gram-negative, and anerobic bacteria. Empiric broad-spectrum antibiotic coverage is warranted, taking into account area disease-state epidemiology and antimicrobial susceptibility data. Telavancin is an antimicrobial agent with a broad Gram-positive spectrum of activity which was recently approved for the treatment of SSSIs. It may especially benefit patients with resistant organisms, such as methicillin-resistant Staphylococcus aureus. This article reviews telavancin and its pharmacology, efficacy, and safety data to enhance the practitioner’s knowledge base on the appropriateness of telavancin for the treatment of SSSIs.

Resistance and the management of complicated skin and skin structure infections: the role of ceftobiprole

Antimicrobial resistant bacteria are an increasing concern due to the resulting increase in morbidity, mortality, and health-care costs associated with the administration of inadequate or delayed antimicrobial therapy. The implications of inadequate antimicrobial therapy in complicated skin and skin structure infections (cSSSIs) have gained more attention recently, most likely due to the recent emergence of community-acquired methicillin resistant Staphylococcus aureus (MRSA) and the already high prevalence of MRSA in the nosocomial setting. Due to the continuous threat of resistance arising and the limitations of currently available agents for the treatment of cSSSIs, it is necessary to develop new antimicrobials for this indication. Ceftobiprole medocaril, the prodrug of ceftobiprole, is a parental investigational cephalosporin for the treatment of cSSSIs displaying a wide-spectrum of activity against both Gram-positive and Gram-negative species, including MRSA. Ceftobiprole displays noncomplex linear pharmacokinetics, is eliminated primarily by glomerular filtration, and distributes to extracellular fluid. Additionally, it has been shown that the extent of distribution to the site of action with regard to cSSSIs, ie, the extracellular space fluid of subcutaneous adipose tissue and skeletal muscle, is expected to be efficacious, as free concentrations meet efficacy targets for most pathogens. Similar to other beta-lactams, it displays an excellent safety and tolerability profile with the primary adverse events being dysgeusia in healthy volunteers, resulting from the conversion of the prodrug to the active, and nausea in patients. Ceftobiprole has demonstrated noninferiority in two large-scale pivotal studies comparing it to vancomycin, clinical cure rates 93.3% vs 93.5%, respectively, or vancomycin plus ceftazidime, clinical cure rates 90.5% vs 90.2%, respectively. Given the pharmacokinetic and pharmacodynamic properties, ceftobiprole is a promising new agent for the treatment of cSSSIs and has the potential to be used as a single agent for empiric treatment.

Antibiotic optimization in the difficult-to-treat patient with complicated intra-abdominal or complicated skin and skin structure infections: focus on tigecycline

Complicated intra-abdominal and skin and skin structure infections are widely varied in presentation. These infections very often lead to an increase in length of hospital stay, with a resulting increase in costs and mortality. In addition, these infections may be caused by a wide variety of bacteria and are often polymicrobial with the possibility of the presence of antimicrobial-resistant strains, such as methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci, extended-spectrum β-lactamase strains (Escherichia coli, Klebsiella pneumoniae), and K. pneumoniae carbapenemase-producing strains. In combination with patients’ immunosuppression or comorbidities, the treatment and management options for initial therapy success are few. Tigecycline, a new glycylcyline antimicrobial from the tetracycline drug class, represents a viable option for the successful treatment of these infections. It has been shown to have activity against a wide variety of bacteria, including the antimicrobial-resistant strains. As with all tetracycline drugs, it is not recommended for pregnant or nursing women. The potential side effects are those typical of tetracycline drugs: nausea, vomiting, and headaches. Drug–drug interactions are not expected, and renal function monitoring is not necessary.

Comparison of dog and rabbit plasmas in the tube coagulase test for Staphylococcus aureus

The tube coagulase test, an invaluable laboratory tool for identifying Staphylococcus aureus, is most often done using rabbit plasma. However, there is evidence that depending on the origin of the isolates, other plasmas may be superior. The current study sought to compare the utility of dog and rabbit plasma in the coagulase test for S. aureus isolated from canine (n = 28), bovine (n = 29), and human (n = 30) hosts. Overall, coagulation times were significantly faster for dog (2.38 hr) than rabbit (3.19 hr) plasma. When coagulation times were compared by isolate origin, no significant differences were found for rabbit plasma, whereas bovine isolates clotted dog plasma significantly faster (1.86 hr) than canine (2.79 hr) or human (2.38 hr) isolates. Investigators should be aware that rabbit plasma may not be the ideal coagulase-testing medium for S. aureus from all sources.

Post-surgical wound infections involving Enterobacteriaceae with reduced susceptibility to β-lactams in two Portuguese hospitals

The post-surgical period is often critical for infection acquisition. The combination of patient injury and environmental exposure through breached skin add risk to pre-existing conditions such as drug or depressed immunity. Several factors such as the period of hospital staying after surgery, base disease, age, immune system condition, hygiene policies, careless prophylactic drug administration and physical conditions of the healthcare centre may contribute to the acquisition of a nosocomial infection. A purulent wound can become complicated whenever antimicrobial therapy becomes compromised. In this pilot study, we analysed Enterobacteriaceae strains, the most significant gram-negative rods that may occur in post-surgical skin and soft tissue infections (SSTI) presenting reduced β-lactam susceptibility and those presenting extended-spectrum β-lactamases (ESBL). There is little information in our country regarding the relationship between β-lactam susceptibility, ESBL and development of resistant strains of microorganisms in SSTI. Our main results indicate Escherichia coli and Klebsiella spp. are among the most frequent enterobacteria (46% and 30% respectively) with ESBL production in 72% of Enterobacteriaceae isolates from SSTI. Moreover, coinfection occurred extensively, mainly with Pseudomonas aeruginosa and Methicillin-resistant Staphylococcus aureus (18% and 13%, respectively). These results suggest future research to explore if and how these associations are involved in the development of antibiotic resistance.

A retrospective review of clinical experience with daptomycin for a variety of wound types in a burn and wound care facility

OBJECTIVE

Daptomycin is a novel antibiotic with activity against many Gram-positive organisms that has demonstrated efficacy in the management of skin and soft tissue infections (SSTIs). However, data regarding the use of daptomycin for the management of burn wound infections are lacking. We assessed the efficacy and safety of daptomycin in the treatment of complicated skin and soft tissue infections (cSSTIs), including burn wound infections.

METHODS

We performed a retrospective review of patients receiving daptomycin for burn wound infections and other cSSTIs in a referral burn and wound treatment center.

RESULTS

Our review revealed an overall success rate (microbiological cure + clinically improved) of 99.5%, with an overall success rate of 98.5% among burn patients, specifically. The overall success rate was 100% among patients in the three other diagnosis groups (cSSTIs, chronic wounds, and other infections). A success rate of 98% was noted among the subset of patients with wounds associated with bacteremia.

CONCLUSIONS

Our study suggests that daptomycin is a safe and effective agent for the management of burn wound infections, although further study is warranted to confirm these results.

Efficient photodynamic therapy against gram-positive and gram-negative bacteria using THPTS, a cationic photosensitizer excited by infrared wavelength

The worldwide rise in the rates of antibiotic resistance of bacteria underlines the need for alternative antibacterial agents. A promising approach to kill antibiotic-resistant bacteria uses light in combination with a photosensitizer to induce a phototoxic reaction. Concentrations of 1, 10 and 100µM of tetrahydroporphyrin-tetratosylat (THPTS) and different incubation times (30, 90 and 180min) were used to measure photodynamic efficiency against two Gram-positive strains of S.aureus (MSSA and MRSA), and two Gram-negative strains of E.coli and P.aeruginosa. We found that phototoxicity of the drug is independent of the antibiotic resistance pattern when incubated in PBS for the investigated strains. Also, an incubation with 100µM THPTS followed by illumination, yielded a 6lg (≥99.999%) decrease in the viable numbers of all bacteria strains tested, indicating that the THPTS drug has a high degree of photodynamic inactivation. We then modulated incubation time, photosensitizer concentration and monitored the effect of serum on the THPTS activity. In doing so, we established the conditions to obtain the strongest bactericidal effect. Our results suggest that this new and highly pure synthetic compound should improve the efficiency of photodynamic therapy against multiresistant bacteria and has a significant potential for clinical applications in the treatment of nosocomial infections.

Antibiotic resistance of subgingival species in chronic periodontitis patients

BACKGROUND AND OBJECTIVE

The increasing rate of resistance of microorganisms to penicillin and other antibiotics has generated concern among health authorities in Latin America. The present investigation determined the in vitro susceptibility of Porphyromonas gingivalis, Fusobacterium nucleatum, black-pigmented Prevotella spp. and Aggregatibacter actinomycetemcomitans to metronidazole, amoxicillin, amoxicillin/clavulanic acid, clindamycin and moxifloxacin in patients with chronic periodontitis.

MATERIAL AND METHODS

Subgingival plaque samples from patients with periodontitis were collected and cultured on selective and nonselective culture media. The antimicrobial susceptibility of periodontopathogenic isolates was studied in chronic periodontitis patients in Colombia. Metronidazole, amoxicillin, amoxicillin/clavulanic acid, clindamycin and moxifloxacin were tested on all bacterial isolates and the percentage of resistant strains was calculated.

RESULTS

Of the 150 bacteria identified, 51 were P. gingivalis, 45 were black-pigmented Prevotella spp., 36 were F. nucleatum and 18 were A. actinomycetemcomitans. All the isolates were sensitive to amoxicillin/clavulanic acid and to moxifloxacin, but exhibited variable susceptibility patterns to the other antimicrobial agents tested.

CONCLUSION

The results of the present study suggest that periodontal microorganisms in patients with chronic periodontitis can be resistant to the antimicrobial agents commonly used in anti-infective periodontal therapy. We suggest that the indiscriminate use of antimicrobials could result in the appearance of more highly antibiotic-resistant strains of bacteria associated with periodontal diseases in our population compared with the populations of other countries.

Large screening of CA-MRSA among Staphylococcus aureus colonizing healthy young children living in two areas (urban and rural) of Portugal

BACKGROUND

The incidence of pediatric infections due to community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA), including children with no identifiable risk factors, has increased worldwide in the last decade. This suggests that healthy children may constitute a reservoir of MRSA in the community. In this study, nested within a larger one on nasopharyngeal ecology, we aimed to: (i) evaluate the prevalence of MRSA colonizing young children in Portugal; and (ii) compare results with those obtained in a study conducted a decade ago, when this prevalence was <0.5%.

METHODS

In the years 2006, 2007, and 2009, nasopharyngeal samples were obtained from 2,100 children aged up to 6 years attending day-care centers. S. aureus were isolated by routine procedures and strains were tested for susceptibility against a panel of 12 antimicrobial agents. MRSA isolates were further characterized by SmaI-PFGE profiling, MLST, spa typing, SCCmec typing, and presence of virulence factors.

RESULTS

Seventeen percent of the children carried S. aureus. Among the 365 isolates, non-susceptibility rates were 88% to penicillin, 14% to erythromycin, 6% to clindamycin, 2% to tetracycline, and <1% to oxacillin, rifampicin, ciprofloxacin, and SXT. Three MRSA strains were isolated. These had properties of CA-MRSA, such as low-level resistance to oxacillin and limited resistance to non-beta-lactams. Two CA-MRSA were related to USA700 (ST72-IV): one was ST72-IVc, spa type t148; the other was ST939-IVa (ST939 is a single locus variant (SLV) of ST72), spa type t324. The third strain was related to USA300 (ST8-IV) being characterized by ST931 (SLV of ST8)-VI, spa type t008. The three MRSA strains were PVL-negative, but all carried LukE-LukD leukocidin, hemolysins gamma, gamma variant and beta, and staphylococcal enterotoxin sel.

CONCLUSIONS

Our results, based on analysis of S. aureus isolated from nasopharyngeal samples, suggest that in Portugal the prevalence of CA-MRSA carriage in healthy young children remains extremely low favoring the exclusion of this group as a reservoir of such isolates.

Acinetobacter baumannii-associated skin and soft tissue infections: recognizing a broadening spectrum of disease

BACKGROUND

Acinetobacter baumannii is gaining importance as a cause of nosocomial infections, but its role in skin and soft tissue infection (SSTI) is not well defined. As a result of the outbreak of A. baumannii occurring in military personnel in Iraq and Afghanistan, reports of severe wound infections and SSTI caused by this pathogen are increasing in frequency.

METHODS

We describe four cases of monomicrobial and polymicrobial A. baumannii-associated necrotizing SSTI accompanied by A. baumannii bacteremia and offer a review of similar experiences published in the literature.

RESULTS

Our comparative analysis reveals four unique features associated with necrotizing SSTI associated with A. baumannii: i) Occurs in hosts with underlying comorbidities (e.g., trauma, cirrhosis); ii) is often accompanied by bacteremia; iii) multiple drug resistance and the presence of co-pathogens frequently complicated treatment (64% of cases); iv) the cases reported here and in our review required surgical debridement (84% of cases) and led to substantial mortality (approximately 30%).

CONCLUSIONS

As the prevalence of A. baumannii continues to increase in our health care system, SSTIs caused by this organism may become more common. Clinicians must be aware that the spectrum of disease caused by A. baumannii could include severe necrotizing SSTI and that vigilance for potential complications is necessary.

Molecular epidemiology of vancomycin-resistant Enterococcus faecium: a prospective, multicenter study in South American hospitals

Enterococcus faecium has emerged as an important nosocomial pathogen worldwide, and this trend has been associated with the dissemination of a genetic lineage designated clonal cluster 17 (CC17). Enterococcal isolates were collected prospectively (2006 to 2008) from 32 hospitals in Colombia, Ecuador, Perú, and Venezuela and subjected to antimicrobial susceptibility testing. Genotyping was performed with all vancomycin-resistant E. faecium (VREfm) isolates by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing. All VREfm isolates were evaluated for the presence of 16 putative virulence genes (14 fms genes, the esp gene of E. faecium [espEfm], and the hyl gene of E. faecium [hylEfm]) and plasmids carrying the fms20-fms21 (pilA), hylEfm, and vanA genes. Of 723 enterococcal isolates recovered, E. faecalis was the most common (78%). Vancomycin resistance was detected in 6% of the isolates (74% of which were E. faecium). Eleven distinct PFGE types were found among the VREfm isolates, with most belonging to sequence types 412 and 18. The ebpAEfm-ebpBEfm-ebpCEfm (pilB) and fms11-fms19-fms16 clusters were detected in all VREfm isolates from the region, whereas espEfm and hylEfm were detected in 69% and 23% of the isolates, respectively. The fms20-fms21 (pilA) cluster, which encodes a putative pilus-like protein, was found on plasmids from almost all VREfm isolates and was sometimes found to coexist with hylEfm and the vanA gene cluster. The population genetics of VREfm in South America appear to resemble those of such strains in the United States in the early years of the CC17 epidemic. The overwhelming presence of plasmids encoding putative virulence factors and vanA genes suggests that E. faecium from the CC17 genogroup may disseminate in the region in the coming years.

Trends in US hospital admissions for skin and soft tissue infections

Using data from the 2000–2004 US Healthcare Cost and Utilization Project National Inpatient Sample, we found that total hospital admissions for skin and soft tissue infections increased by 29% during 2000–2004; admissions for pneumonia were largely unchanged. These results are consistent with recent reported increases in community-associated methicillin-resistant Staphylococcus aureus infections.

Murine model of cutaneous infection with Streptococcus pyogenes

Despite the medical advances achieved during the last century to fight against bacteria, viruses, fungi and parasites, infectious diseases are still a major cause of death, disability, and social and economic upheaval for millions around the world. Challenges remain in countering microorganisms even where antibiotics and vaccines are available. Much remains to be learned about basic aspects of the host-pathogen relationship and the complexity of the immune response to infection. Animal models represent a powerful tool to dissect the host response to infection, as well as the pathogenesis of the microbe. One of the advantages of using animal models is that both genetic and environmental factors that may influence the course of an infection can be controlled, allowing a precise cause-effect analysis of the host-pathogen interactions. In addition, there are no real alternatives to whole animal models in the study of integrative physiology and dynamic pathophysiologic alterations. The use of animal models has also proven invaluable for testing the efficacy of experimental antimicrobial agents and their therapeutic regimes. The mouse model is the most widely used for many reasons, including its cost effectiveness, the high number of immunological reagents available for this species, and the relative ease of biocontainment. Mouse strains with specific properties such as transgenic mouse strains with gene insertion or targeted mutation (knock-out) are very effective tools for studying the role of specific genes controlling the immune response to infectious pathogens. Murine models will remain the most appropriate tool for evaluating new therapeutic strategies for the treatment of various diseases. The closer the model is adapted to the human disease, the more reliable will be the results.In this chapter, the experimental procedures required to establish a mouse model of cutaneous and soft tissue infection are detailed. This model has provided invaluable insights into the pathogenicity of the agent for the human host.

Comparative in vitro activity profile of oritavancin against recent gram-positive clinical isolates

Oritavancin activity was tested against 15,764 gram-positive isolates collected from 246 hospital centers in 25 countries between 2005 and 2008. Organisms were Staphylococcus aureus (n = 9,075), coagulase-negative staphylococci (n = 1,664), Enterococcus faecalis (n = 1,738), Enterococcus faecium (n = 819), Streptococcus pyogenes (n = 959), Streptococcus agalactiae (n = 415), group C, G, and F streptococci (n = 84), and Streptococcus pneumoniae (n = 1,010). Among the evaluated staphylococci, 56.7% were resistant to oxacillin. The vancomycin resistance rate among enterococci was 21.2%. Penicillin-resistant and -intermediate rates were 14.7% and 21.4%, respectively, among S. pneumoniae isolates. Among nonpneumococcal streptococci, 18.5% were nonsusceptible to erythromycin. Oritavancin showed substantial in vitro activity against all organisms tested, regardless of resistance profile. The maximum oritavancin MIC against all staphylococci tested (n = 10,739) was 4 microg/ml; the MIC(90) against S. aureus was 0.12 microg/ml. Against E. faecalis and E. faecium, oritavancin MIC(90)s were 0.06 and 0.12, respectively. Oritavancin was active against glycopeptide-resistant enterococci, including VanA strains (n = 486), with MIC(90)s of 0.25 and 1 microg/ml against VanA E. faecium and E. faecalis, respectively. Oritavancin showed potent activity against streptococci (n = 2,468); MIC(90)s for the different streptococcal species were between 0.008 and 1 microg/ml. These data are consistent with previous studies with respect to resistance rates of gram-positive isolates and demonstrate the spectrum and in vitro activity of oritavancin against a wide variety of contemporary gram-positive pathogens, regardless of resistance to currently used drugs. The data provide a foundation for interpreting oritavancin activity and potential changes in susceptibility over time once oritavancin enters into clinical use.

Susceptibility of Pseudomonas aeruginosa clinical isolates in Japan to doripenem and other antipseudomonal agents

We investigated the susceptibility of 694 Pseudomonas aeruginosa clinical isolates to nine antipseudomonal agents including doripenem. Test strains were collected from 23 Japanese medical facilities from 1992 to 2004. Doripenem showed a minimum inhibitory concentration for 90% of the organisms (MIC(90)) of 8 microg/mL, which was the lowest among the tested antipseudomonal agents. The MIC(90) of doripenem was 2-fold lower than that of meropenem, imipenem and amikacin and was > or =4-fold lower than that of piperacillin/tazobactam, ceftazidime, cefepime, ciprofloxacin and tobramycin. Amikacin showed the lowest rate of resistance against all clinical isolates (5.8%) followed by doripenem (7.1%). No remarkable changes were observed from 1992 to 2004 in the frequency of P. aeruginosa strains resistant to the tested agents, except for imipenem. Of 116 ceftazidime-resistant strains, from 44.0% to 50.8% were susceptible to the three carbapenems, but only 2.6% to cefepime. Of 138 imipenem-resistant strains, from 44.2% to 51.4% were susceptible to doripenem and both cephems, but 25.4% to meropenem. Doripenem was more active against imipenem- or ceftazidime-resistant strains than meropenem, although the activity of doripenem correlated well with that of meropenem. In conclusion, doripenem had the most potent in vitro activity against P. aeruginosa clinical isolates among the tested antibiotics. Considering the trend of antimicrobial resistance of the clinical isolates in well-focused surveillance, pseudomonal infections should be treated with appropriate chemotherapy using antimicrobial agents with potent antipseudomonal activity and low resistance rates, such as doripenem, in order to prevent the outbreak of resistant strains.

Skin and soft tissue infection: microbiology and epidemiology

Skin and soft tissue infections (SSTIs) are common and range in severity from minor, self-limiting, superficial infections to life-threatening diseases requiring all the resources of modern medicine. The classification of SSTIs can be based on the anatomical site, clinical severity or microbial cause, but some classifications divide SSTIs into complicated and uncomplicated infections. Community-acquired SSTIs are most commonly caused by staphylococci or streptococci, but almost any organism is capable of causing inflammation within soft tissue. Recent epidemiological trends have shown an increase not only in healthcare-associated meticillin-resistant Staphylococcus aureus (MRSA), but also in MRSA acquired in the community. Many of the latter strains produce exotoxins and are epidemiologically distinct from healthcare-acquired strains. Factors that may affect the microbial cause include underlying disease such as diabetes or immune dysfunction; hospital attendance, injecting drug use, travel, animal contact and environmental contamination.

Why is community-associated MRSA spreading across the world and how will it change clinical practice?

Meticillin-resistant Staphylococcus aureus (MRSA) emerged in 1960 and over the following 40 years was a problem confined largely to the healthcare setting. In the late 1990s the first US reports of so-called community-associated MRSA (CA-MRSA) infections appeared. CA-MRSA infections were defined as MRSA infections occurring in patients who had no identifiable predisposing risk factors, such as healthy children and young adults. CA-MRSA is associated with a novel genetic profile and phenotype; it is remarkably fit and capable of spreading within communities, it is virulent and is often susceptible to multiple narrow-spectrum antimicrobials other than beta-lactams. CA-MRSA infections involve predominantly skin and soft tissue; however, necrotizing pneumonia and necrotizing fasciitis have been described. At present, several reports suggest that CA-MRSA may be replacing the hospital-acquired MRSA strains (HA-MRSA), with potentially catastrophic consequences. Given the rapid spread and the high virulence of CA-MRSA, global strategies are needed. Prompt, appropriate treatment, guided by the site and type of infection and risk factors for HA-MRSA or CA-MRSA, increases the chances of a successful outcome and is urgently needed.

Evaluation of Nisin F in the Treatment of Subcutaneous Skin Infections, as Monitored by Using a Bioluminescent Strain of Staphylococcus aureus

The potential of nisin F as an antimicrobial agent in treating subcutaneous skin infections was tested in vivo by infecting C57BL/6 mice with a bioluminescent strain of Staphylococcus aureus (Xen 36). Strain Xen 36 has the luxABCDE operon located on a native plasmid. Mice were grouped into four groups: Infected with strain Xen 36 and treated with nisin F, infected with strain Xen 36 and treated with saline (placebo), not infected and treated with nisin (control) and not infected and not treated (control). The immune systems of the mice were suppressed with deksamethasone. Mice were treated with either nisin F or sterile physiological saline 24 and 48 h after infection with subcutaneously injected S. aureus Xen 36 (4 × 10(6) CFU). Histology and bioluminescent flux measurements revealed no significant difference between infected mice treated with nisin and saline, respectively. However, infected mice treated with nisin F had an increased number of polymorphonuclear cells when compared with infected mice treated with saline. Also, not infected mice treated with nisin F had an influx of polymorphonuclear cells. Nisin F is thus ineffective in combating deep dermal staphylococcal infections. The apparent immune modulation of nisin when subcutaneously injected has to be investigated.