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

Antimicrobial Blue Light Inactivation of Microbial Isolates in Biofilms

BACKGROUND AND OBJECTIVES

Biofilms cause more than 80% of infections in humans, including more than 90% of all chronic wound infections and are extremely resistant to antimicrobials and the immune system. The situation is exacerbated by the fast spreading of antimicrobial resistance, which has become one of the biggest threats to current public health. There is consequently a critical need for the development of alternative therapeutics. Antimicrobial blue light (aBL) is a light-based approach that exhibits intrinsic antimicrobial effect without the involvement of exogenous photosensitizers. In this study, we investigated the antimicrobial effect of this non-antibiotic approach against biofilms formed by microbial isolates of multidrug-resistant bacteria.

STUDY DESIGN/MATERIALS AND METHODS

Microbial isolates of Acinetobacter baumannii, Candida albicans, Escherichia coli, Enterococcus faecalis, MRSA, Neisseria gonorrhoeae, Pseudomonas aeruginosa, and Proteus mirabilis were studied. Biofilms were grown in microtiter plates for 24 or 48 hours or in the CDC biofilm reactor for 48 hours and exposed to aBL at 405 nm (60 mW/cm² , 60 or 30 minutes). The anti-biofilm activity of aBL was measured by viable counts.

RESULTS

The biofilms of A. baumannii, N. gonorrhoeae, and P. aeruginosa were the most susceptible to aBL with between 4 and 8 log₁₀ inactivation after 108 J/cm² (60 mW/cm² , 30 minutes) or 216 J/cm² (60 mW/cm² , 60 minutes) aBL were delivered in the microplates. On the contrary, the biofilms of C. albicans, E. coli, E. faecalis, and P. mirabilis were the least susceptible to aBL inactivation (-0.30, -0.24, -0.84, and -0.68 log₁₀ inactivation, respectively). The same aBL treatment in biofilms developed in the CDC biofilm reactor, caused -1.68 log₁₀ inactivation in A. baumannii and -1.74 and -1.65 log₁₀ inactivation in two different strains of P. aeruginosa.

CONCLUSIONS

aBL exhibits potential against pathogenic microorganisms and could help with the significant need for new antimicrobials in clinical practice to manage multidrug-resistant infections. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

The bactericidal effect of lysostaphin coupled with liposomal vancomycin as a dual combating system applied directly on methicillin-resistant Staphylococcus aureus infected skin wounds in mice

Background and aim

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most common causes of surgical infection, and its resistance to numerous conventional antibiotics makes treatment difficult. Although vancomycin is often an effective agent for the initial therapy of MRSA, clinical failure sometimes occurs. Therefore, there is an urgent need to develop better therapies. Here, we prepared some vancomycin-loaded nanoliposomes coupled with anti-staphylococcal protein (lysostaphin) and evaluated their in vitro and in vivo efficacy as a topical MRSA therapy.

Methods

Vancomycin was encapsulated in liposomes, and the coupling of lysostaphin with the surface of liposomes was carried out through cyanuric functional groups. The bactericidal efficacies and a full characterization were evaluated. To define different nanoliposomal–bacterium interactions and their bactericidal effect, flow cytometry was employed. Finally, in vivo, the topical antibacterial activity of each formulation was measured against surgical wound MRSA infection in a mouse model.

Results

High encapsulation and conjugation efficiency were achieved for all formulations. All the formulations showed a significant reduction in bacterial counts (p<0.05). The targeted liposomes more effectively suppress bacterial infection in vitro and in vivo relative to equivalent doses of untargeted vancomycin liposome. The flow cytometry results confirmed liposome–bacterium interactions, which increased during the incubation time. The maximum binding rate and the bactericidal effect were significantly higher in targeted liposomes (p<0.05) compared with control liposomes.

Conclusion

Our data suggest a novel nano-vehicle (lysostaphin-conjugated coupled liposomal vancomycin) which could be used as a great topical antimicrobial construct for treatment of MRSA skin infections.

Staphylococcus aureus induces COX-2-dependent proliferation and malignant transformation in oral keratinocytes

The COX-2/PGE₂ axis can play roles in mediating the progression of tumor. COX-2 induction was observed in oral cancer. In our previous study, we found Staphylococcus aureus, a pathogen prevalent in oral cancer, can activate the COX-2/PGE₂ pathway in human oral keratinocyte (HOK) cells. Here, we investigated the proliferation of HOK cells affected by COX-2 induction and the role of COX-2 induction in the malignant transformation of HOK cells. We found S. aureus was able to facilitate HOK cell proliferation through upregulating COX-2 expression. With the induction of COX-2, expression of oral cancer-associated genes cyclin D1 was upregulated and p16 was downregulated. Transcriptome analysis showed that the “NF−kappa B signaling pathway” and “TNF signaling pathway” had the highest enrichment of differentially expressed genes (DEGs) with COX-2 over-expression. Seven upregulated genes (jun, tlr4, cxcl1, lif, cxcl3, tnfrsf1β, and il1β) in these two pathways were critical for the increased proliferation of HOK cells and might be associated with COX-2. Malignant transformation of cells was evaluated by soft agar colony formation assay and S. aureus infection promoted HOK cell colony formation. These results suggest the potential of S. aureus to induce the infection-associated malignant transformation of oral epitheliums through COX-2 activation.

The optimal duration of treatment for skin and soft tissue infections and acute bacterial skin and skin structure infections

PURPOSE OF REVIEW

To summarize the current finding on SSTIs/ABSSSIs treatment duration.

RECENT FINDINGS

In 2013, the FDA approved the definition of acute bacterial skin and skin structure infections (ABSSSIs). From a clinical point of view, the new definition may present some advantages: the definition of the severity of the disease, the measurement of reduction in lesion size, and effectiveness of treatment primary endpoint at 48-72 h after treatment initiation. New therapeutic options with improved efficacy, safety, and/or pharmacodynamics are available for ABSSSIs and so far, several questions still need to be addressed for the management of these infections, including treatment duration.

SUMMARY

There is a wide variation of duration of antimicrobial treatment in skin and soft tissue infections. Plenty of published data available suggest that we should focus on the early response to shorten duration of treatment, and that the antimicrobial stewardship perspective is extremely helpful in underscoring the need for composite outcomes in clinical practice, as multiple tools are available to increase cost-efficacy, including reduction of treatment changes, early oral switch, early discharge (even from the Emergency Department), outpatient antimicrobial treatment, long-acting antibiotics, and all together, de-escalation treatment strategies.

When to switch to an oral treatment and/or to discharge a patient with skin and soft tissue infections

PURPOSE OF REVIEW

Skin and soft tissue infections prevalence is increasing and represent a frequent cause of hospital admission. New guidelines have become available in order to better define these infections and their response to antimicrobial treatment. Gram-positive bacteria, in particular Staphylococcus aureus, remain the most frequently isolated pathogens in skin and soft tissue infections. To treat complicated forms and infections caused by drug-resistant bacteria, hospital admission and administration of intravenous antibiotics are often required, impacting on healthcare costs and patients' morbidity.

RECENT FINDINGS

New therapeutic options offer efficacy against drug-resistant Gram-positive bacteria as well as potential to favor early patients' discharge, including the possibility for intravenous to oral switch and infrequent drug administration because of prolonged drug half-life. Although data from real-world studies on new antimicrobials is awaited, clinicians need clear direction on how to optimize the treatment of skin and soft tissue infections in order to avoid prolonged hospitalizations and extra costs. Early assessment of patient's clinical conditions and response to treatment appear useful in order to facilitate patients' discharge.

SUMMARY

We have reported the evidence for early intravenous to oral switch and early hospital discharge for patients with skin and soft tissue infections. New therapeutic options that represent promising tools in promoting an optimized management of these infections have also been reviewed.

The role of dalbavancin in skin and soft tissue infections

PURPOSE OF REVIEW

The increase of skin and soft tissue infections (SSTIs) represents a major concern both in community and in the hospital setting. Staphylococcus aureus is the most frequently isolated pathogen, and the rise in infections due to methicillin-resistant Staphylococcus aureus (MRSA) has been associated with inadequate antibiotic treatment and increased morbidity.

RECENT FINDINGS

A number of new antimicrobials with activity against drug-resistant Gram-positive pathogens, including MRSA, have been recently approved for the treatment of SSTIs. New lipoglycopeptides, in particular dalbavancin, are long-acting antibiotics with potential for infrequent administration, offering the possibility for outpatient treatment and early hospital discharge.

SUMMARY

Dalbavancin is a new lipoglycopeptide showing high activity against Gram-positive bacteria, including drug-resistant strains. Dalbavancin presents a distinctive pharmacokinetic profile with a terminal prolonged half-life of approximately 14 days. This characteristic allows once-weekly dosing interval, avoiding the need for daily dosing and offering an advantage over other compounds for potential use in the outpatient setting or to promote early hospital discharge. Dalbavancin has a favorable adverse effect profile and appears to be a promising new alternative for treatment of SSTIs. We have reviewed the pharmacokinetic properties of dalbavancin and the clinical evidence for its use in complicated SSTIs and other potential applications.

Hydroconductive and silver-impregnated foam dressings: a comparison

OBJECTIVE

As the number of commercially available wound dressings is increasing rapidly, it is important for clinicians to understand the strengths and limitations of each and to recognise relationships between wound type and dressing properties to obtain optimal healing results. Our aim is to test the antimicrobial activity of two dressings.

METHOD

A hydroconductive (HC) dressing and a silver-impregnated foam (SIF) dressing were compared for their potential to reduce the levels meticillin-resistant Staphylococcus aureus (MRSA). We also assessed MRSA-derived biologically active components in liquid or agar matrices, simplified models for heavily exuding or dry wounds respectively, and in an in vivo animal model with MRSA infected wounds.

RESULTS

In the agar model (dry wounds) both dressings showed a strong reduction in MRSA activities within 24 hours post-application. The antibacterial effects of the SIF dressing were more pronounced in the liquid model, however, at an increasing cytotoxic cost. In agreement with these in vitro results, assessment of dressings using an MRSA-infected wound in an rat model showed a decrease in MRSA which was significant 7 days post-burn and inoculation, with more compromised viability of MRSA. Dressings showed a similar capability to reduced and eliminate toxic shock syndrome toxin (TSST-1) at day 7 post-burn in the animal model but not at day 4, where the SIF dressing was more potent Conclusion: These results confirm the advantages of using silver in reducing bacterial load in wound treatment, except for conditions of highly exuding wounds where the cytotoxic properties of silver may offset these advantages and HC dressing use is more suitable.

Network meta-analysis and pharmacoeconomic evaluation of antibiotics for the treatment of patients infected with complicated skin and soft structure infection and hospital-acquired or ventilator-associated penumonia

Background

Infections due to methicillin-resistant Staphylococcus aureus (MRSA) cause serious health risks and significant economic burdens and the preferred drugs are still controversial.

Methods

We performed a network meta-analysis (NMA) to compare the efficacy and safety of antibiotics used to treat inpatients with complicated skin and soft structure infections (cSSSI) or hospital-acquired or ventilator-associated pneumonia (HAP/VAP). We also developed a decision tree model to assess the cost-effectiveness of antibiotics.

Results

Forty-nine randomized controlled trials met the inclusion criteria (34 for cSSSI, 15 for HAP/VAP) and compared the efficacy and safety of 16 antibiotics. For cSSSI, NMA indicated that for clinical cure, linezolid was superior than vancomycin (odds ratio (OR) 1.55, 95% confidence interval (CI) 1.19-2.02), while tedizolid (OR 1.39, CI 0.70-2.76) was similar to vancomycin. In terms of safety, there were no significant differences between any two interventions on total adverse events. Based on drug and hospital costs in America, the incremental cost-effectiveness ratios (ICERs) per life-year saved for linezolid and tedizolid compared with vancomycin were US$2833 and US$5523. For HAP/VAP, there were no significant effects either for clinical cure or for safety endpoints between linezolid and vancomycin in NMA. ICERs per life-year saved for linezolid compared with vancomycin were US$2185.

Conclusion

In these clinical trials, considering efficacy, safety, and cost-effectivenes, linezolid and tedizolid showed their superiority in MRSA cSSSI; while linezolid might be recommended to treat MRSA pneumonia. Although vancomycin was not cost-effective in pharmacoeconomic evaluation, it is still the first-line treatment for MRSA infection in the clinical practice. This study might provide new insights of therapeutic choices for patients with MRSA infections whilst awaiting the arrival of higher quality evidence.

An aryl isonitrile compound with an improved physicochemical profile that is effective in two mouse models of multidrug-resistant Staphylococcus aureus infection

OBJECTIVES

The aim of this study was to investigate the antibacterial activity of a synthetic aryl isonitrile compound (35) that was developed as part of a compound library to identify new antibacterial agents effective against methicillin-resistant Staphylococcus aureus (MRSA).

METHODS

Compound 35 was evaluated against MRSA isolates by the broth microdilution assay and for toxicity to mammalian keratinocytes using the MTS assay. A multistep resistance selection assay was conducted to investigate MRSA resistance development to 35. A Caco-2 bidirectional permeability assay was employed to evaluate the ability of 35 to permeate across the gastrointestinal tract, and compound 35 was incubated with human liver microsomes to determine susceptibility to hepatic metabolism. Finally, compound 35 was evaluated in an uncomplicated MRSA skin infection mouse model and an MRSA neutropenic thigh infection mouse model.

RESULTS

Compound 35 inhibited the growth of MRSA clinical isolates at 2-4μM and was non-toxic to human keratinocytes. No resistance formation was observed with MRSA against compound 35 after 10 serial passages. In a murine skin wound model, compound 35 significantly reduced the burden of MRSA, similar to the antibiotic fusidic acid. Compound 35 exhibited a marked improvement both in permeability and stability to hepatic metabolism (half-life >11h) relative to the first-generation lead compound. In a neutropenic thigh infection mouse model, compound 35 successfully reduced the burden of MRSA in immunocompromised mice.

CONCLUSION

In summary, compound 35 was identified as a new lead aryl isonitrile compound that warrants further investigation as a novel antibacterial agent.

Comparative In Vitro Activities of New Antibiotics for the Treatment of Skin Infections

Bacterial skin infections result in significant morbidity and have contributed to enhanced health-care resource utilization. The problem is heightened by emerging antimicrobial resistance. Multiple novel agents active against resistant pathogens that cause skin infections-including dalbavancin, tedizolid phosphate, oritavancin, and delafloxacin-have been approved over the past 5 years. Common features of these agents include gram-positive activity and favorable safety. Of these agents, delafloxacin is unique in being active against both gram-positive and gram-negative pathogens that cause skin infections, including those resistant to other antimicrobial agents. It is, therefore, an effective option for the treatment of skin infections.

Profile of a Novel Anionic Fluoroquinolone-Delafloxacin

Fluoroquinolones have been in clinical use for over 50 years with significant efficacy. However, increasing resistance and emergence of some marked adverse events have limited their usage. The most recently approved class member, delafloxacin, is the only available anionic (non-zwitterionic) fluoroquinolone. Its unique molecular structure provides improved in vitro activity against most Gram-positive pathogens, including quinolone-resistant strains, which is further enhanced at acid pH. Delafloxacin shows favorable pharmacological properties, with about 60% bioavailability after oral administration, only mild inhibition of cytochrome P450 3A, and no evidence of cardiac- or phototoxicity in healthy volunteers (tested against positive controls). Its twice daily dosing, suitability for intravenous, oral, or switch dosing, the lack of many clinically significant drug-drug interactions, and acceptable adverse event profile in registration clinical trials supports its use in the treatment of acute bacterial skin and skin structure infections, and potentially in other infections, where resistance to other agents, safety, and/or the need for early discharge is of concern.

Second-generation aryl isonitrile compounds targeting multidrug-resistant Staphylococcus aureus

Antibiotic resistance remains a major global public health threat that requires sustained discovery of novel antibacterial agents with unexploited scaffolds. Structure-activity relationship of the first-generation aryl isonitrile compounds we synthesized led to an initial lead molecule that informed the synthesis of a second-generation of aryl isonitriles. From this new series of 20 compounds, three analogues inhibited growth of methicillin-resistant Staphylococcus aureus (MRSA) (from 1 to 4 µM) and were safe to human keratinocytes. Compound 19, with an additional isonitrile group exhibited improved activity against MRSA compared to the first-generation lead compound. This compound emerged as a candidate worthy of further investigation and further reinforced the importance of the isonitrile functionality in the compounds' anti-MRSA activity. In a murine skin wound model, 19 significantly reduced the burden of MRSA, similar to the antibiotic fusidic acid. In summary, 19 was identified as a new lead aryl isonitrile compound effective against MRSA.

Plasma Activated Oil: Fast Production, Reactivity, Stability, and Wound Healing Application

The "third-generation" cooking oil based drug, named plasma activated oil (PAO), is produced in cheap olive oil by a single-step, room temperature, energy-efficient, and environment-friendly dry plasma-enabled process. The streamer-surface discharge generates abundant energetic species, atomic oxygen at the plasma-oil interface. The otherwise challenging dissociation of C═C double bonds by energetic species and oxidation by the plasma generated atomic oxygen is the key mechanism to produce the H₂O₂ active species and carboxylic acid in the PAO. It is shown that the peroxide value and acid value of PAO are 7.5 times and 57% higher than those of the traditional ozonated oil, respectively. Different from plasma activated water whose shelf life was less than 1 week, PAO could be stored at room temperature for at least 3 months, and a shelf life of up to 1 year is expected. We further reveal that the PAO can not only sterilize the wound, but also promote more release of growth factor such as VEGF and CD34; therefore, the wound healing of PAO is 28.5% faster than that of the control group.

Opportunities for antimicrobial stewardship in patients with acute bacterial skin and skin structure infections who are unsuitable for beta-lactam antibiotics: a multicenter prospective observational study

Purpose:

The objective of this prospective, observational study was to describe the treatment, severity assessment and healthcare resources required for management of patients with acute bacterial skin and skin structure infections who were unsuitable for beta-lactam antibiotic treatments.

Methods:

Patients were enrolled across five secondary care National Health Service hospitals. Eligible patients had a diagnosis of acute bacterial skin and skin structure infection and were considered unsuitable for beta-lactam antibiotics (e.g. confirmed/suspected methicillin-resistant Staphylococcus aureus, beta-lactam allergy). Data regarding diagnosis, severity of the infection, antibiotic treatment and patient management were collected.

Results:

145 patients with acute bacterial skin and skin structure infection were included; 79% (n = 115) patients received greater than two antibiotic regimens; median length of the first antibiotic regimen was 2 days (interquartile range of 1–5); median time to switch from intravenous to oral antibiotics was 4 days (interquartile range of 3–8, n = 72/107); 25% (n = 10/40) patients with Eron class 1 infection had systemic inflammatory response syndrome, suggesting they were misclassified. A higher proportion of patients with systemic inflammatory response syndrome received treatment in an inpatient setting, and their length of stay was prolonged in comparison with patients without systemic inflammatory response syndrome.

Conclusion:

There exists an urgent need for more focused antimicrobial stewardship strategies and tools for standardised clinical assessment of acute bacterial skin and skin structure infection severity in patients who are unsuitable for beta-lactam antibiotics. This will lead to optimised antimicrobial treatment strategies and ensure effective healthcare resource utilisation.

Omadacycline for Acute Bacterial Skin and Skin-Structure Infections

BACKGROUND

Acute bacterial skin and skin-structure infections are associated with substantial morbidity and health care costs. Omadacycline, an aminomethylcycline antibiotic that can be administered once daily either orally or intravenously, is active against pathogens that commonly cause such infections, including antibiotic-resistant strains.

METHODS

In this double-blind trial, we randomly assigned adults with acute bacterial skin and skin-structure infections (in a 1:1 ratio) to receive omadacycline (100 mg given intravenously every 12 hours for two doses, then 100 mg given intravenously every 24 hours) or linezolid (600 mg given intravenously every 12 hours). A transition to oral omadacycline (300 mg every 24 hours) or oral linezolid (600 mg every 12 hours) was allowed after 3 days; the total treatment duration was 7 to 14 days. The primary end point was an early clinical response at 48 to 72 hours, defined as survival with a reduction in lesion size of at least 20% without rescue antibacterial therapy. A secondary end point was an investigator-assessed clinical response at the post-treatment evaluation 7 to 14 days after the last dose, with clinical response defined as survival with resolution or improvement in signs or symptoms of infection to the extent that further antibacterial therapy was unnecessary. For both end points, the noninferiority margin was 10 percentage points.

RESULTS

In the modified intention-to-treat population, omadacycline (316 patients) was noninferior to linezolid (311 patients) with respect to early clinical response (rate of response, 84.8% and 85.5%, respectively; difference, -0.7 percentage points; 95% confidence interval [CI], -6.3 to 4.9). Omadacycline also was noninferior to linezolid with respect to investigator-assessed clinical response at the post-treatment evaluation in the modified intention-to-treat population (rate of response, 86.1% and 83.6%, respectively; difference, 2.5 percentage points; 95% CI, -3.2 to 8.2) and in the clinical per-protocol population (96.3% and 93.5%, respectively; difference, 2.8 percentage points; 95% CI, -1.0 to 6.9). In both groups, the efficacy of the trial drug was similar for methicillin-susceptible and methicillin-resistant Staphylococcus aureus infections. Adverse events were reported in 48.3% of the patients in the omadacycline group and in 45.7% of those in the linezolid group; the most frequent adverse events in both groups were gastrointestinal (in 18.0% and 15.8% of the patients in the respective groups).

CONCLUSIONS

Omadacycline was noninferior to linezolid for the treatment of acute bacterial skin and skin-structure infections and had a similar safety profile. (Funded by Paratek Pharmaceuticals; OASIS-1 ClinicalTrials.gov number, NCT02378480 .).

Economic evaluation of the treatment of Acute Bacterial Skin and Skin Structure Infections (ABSSSIs) from the national payer perspective: introduction of a new treatment to the patient journey. A simulation of three European countries

Background: The aim of this study was to develop a spending predictor model to evaluate the direct costs associated with the management of ABSSSIs from the National health-care provider's perspective of Italy, Romania, and Spain. Methodology: A decision-analytic model was developed to evaluate the diagnostic and clinical pathways of hospitalized ABSSSI patients based on scientific guidelines and real-world data. A Standard of Care (SoC) scenario was compared with a dalbavancin scenario in which the patients could be discharged early. The epidemiological and cost parameters were extrapolated from national administrative databases (i.e., hospital information system). A probabilistic sensitivity analysis (PSA) and one-way sensitivity analysis (OWA) were performed. Results: Overall, the model estimated an average annual number of patients with ABSSSIs of approximately 50,000 in Italy, Spain, and Romania. On average, the introduction of dalbavancin reduced the length of stay by 3.3 days per ABSSSI patient. From an economic perspective, dalbavancin did not incur any additional cost from the National Healthcare perspective, and the results were consistent among the countries. The PSA and OWA demonstrated the robustness of these results. Conclusion: This model represents a useful tool for policymakers by providing information regarding the economic and organizational consequences of an early discharge approach in ABSSSI management.

Comparison of the microbiological efficacy of tedizolid and linezolid in acute bacterial skin and skin structure infections: pooled data from phase 3 clinical trials

We evaluated the microbiological efficacy of tedizolid compared with that of linezolid against common and emerging pathogens using pooled data from 2 phase 3 trials (NCT01170221 and NCT01421511) in patients with acute bacterial skin and skin structure infections. Patients received tedizolid 200 mg once daily for 6 days (n = 664) or linezolid 600 mg twice daily for 10 days (n = 669). Favorable microbiological outcome in both treatment groups, defined as eradication or presumed eradication at the end of treatment and at the posttherapy evaluation, exceeded 85% for most pathogens, including methicillin-resistant Staphylococcus aureus. Favorable microbiological response was observed for staphylococci and streptococci at tedizolid minimal inhibitory concentration values ≤0.5 mg/L and 0.25 mg/L, respectively. The studies demonstrated positive microbiological outcomes against common pathogens with a 6-day, once-daily regimen of tedizolid phosphate in patients with acute bacterial skin and skin structure infections.

Aggregating resistant Staphylococcus aureus induces hypocoagulability, hyperfibrinolysis, phagocytosis, and neutrophil, monocyte, and lymphocyte binding in canine whole blood

BACKGROUND

Staphylococcus aureus is an opportunistic pathogen with the ability to form mobile planktonic aggregates during growth, in vitro. The in vivo pathophysiologic effects of S aureus aggregates on host responses are unknown. Knowledge of these could aid in combating infections.

OBJECTIVE

This study aimed to investigate the effect of increasing concentrations of two different aggregating S aureus strains on the hemostatic and inflammatory host responses in canine whole blood. The hypothesis was that aggregating bacteria would induce pronounced hemostatic and inflammatory responses.

METHODS

Citrate-stabilized whole blood from 10 healthy dogs was incubated with two strains of aggregating S aureus at three different concentrations. Each sample was analyzed using tissue factor-thromboelastography (TF-TEG) and the formed clot was investigated with electron microscopy. The plasma activated partial thromboplastin time (aPTT), prothrombin time (PT), fibrinogen, and D-dimer tests were measured. Bacteria-leukocyte binding was evaluated with flow cytometry, and neutrophil phagocytosis was assessed using light and transmission electron microscopy.

RESULTS

The highest concentration of bacteria resulted in a significantly shortened TF-TEG initiation time, decreased alpha, maximum amplitude, global strength, and increased lysis. In addition, significantly shortened PT, decreased fibrinogen, and increased D-dimers were demonstrated at the highest concentration of bacteria. Lower concentrations of bacteria showed no differences in TF-TEG when compared with controls. The findings were similar for both S aureus strains. Increased concentration-dependent binding of bacteria and leukocytes and neutrophil bacterial phagocytosis was observed.

CONCLUSIONS

Two strains of S aureus induced alterations of clot formation in concentrations where bacterial aggregates were formed. A concentration-dependent cellular inflammatory response was observed.

Use of Translational Pharmacokinetic/Pharmacodynamic Infection Models To Understand the Impact of Neutropenia on the Efficacy of Tedizolid Phosphate

Tedizolid phosphate, the prodrug of the active antibiotic tedizolid, is an oxazolidinone for the treatment of acute bacterial skin and skin structure infections. Studies in a mouse thigh infection model demonstrated that tedizolid has improved potency and pharmacokinetics/pharmacodynamics (PK/PD) compared with those of linezolid. Subsequent studies showed that the efficacy of tedizolid was enhanced in immunocompetent (IC) mice compared with neutropenic (immunosuppressed [IS]) mice, with stasis at clinically relevant doses being achieved only in the presence of granulocytes. The tedizolid label therefore contains a warning about its use in neutropenic patients. This study reevaluated the PK/PD of tedizolid and linezolid in the mouse thigh infection model in IC and IS mice using a methicillin-resistant Staphylococcus aureus (MRSA) strain (ATCC 33591) and a methicillin-susceptible S. aureus (MSSA) strain (ATCC 29213). The antistaphylococcal effect of doses ranging from 1 to 150 mg/kg of body weight tedizolid (once daily) or linezolid (twice daily) was determined at 24, 48, and 72 h after initiating treatment. In IC mice, stasis was achieved in the absence of antibiotics, and both tedizolid and linezolid reduced the burden further beyond a static effect. In IS mice, tedizolid achieved stasis against MRSA ATCC 33591 and MSSA ATCC 29213 at 72 h at a human clinical dose of 200 mg, severalfold lower than that in earlier studies. Linezolid achieved a static effect against MRSA ATCC 33591 in IS mice at a dose lower than that used clinically. This study demonstrates that, with time, both tedizolid and linezolid at clinically relevant exposures achieve stasis in neutropenic mice with an MRSA or MSSA thigh infection.

Inactivation of the exogenous fatty acid utilization pathway leads to increased resistance to unsaturated fatty acids in Staphylococcus aureus

The human pathogen Staphylococcus aureus produces saturated fatty acids, but can incorporate both exogenous saturated and unsaturated fatty acids into its lipid membrane. S. aureus encounters unsaturated fatty acids in the host skin where they serve as an innate immune defence due to their toxicity. Previously, we identified a fatty acid kinase in S. aureus that is necessary for the utilization of exogenous fatty acids. The goal of this study was to determine the effects of fatty acids on mutants deficient in the exogenous fatty acid utilization machinery. We have demonstrated that mutants lacking a functional fatty acid kinase (fakA) or both fatty acid carrier proteins (fakB1 fakB2) are more resistant to unsaturated fatty acids. Previous studies suggested a role for ammonia-producing enzymes in resistance to unsaturated fatty acids, but these enzymes do not contribute to the resistance of the fakA mutant, despite increased urease transcription and protein activity in the mutant. Additionally, while pigment is altered in mutants unable to use exogenous fatty acids, staphyloxanthin does not contribute to fatty acid resistance of an fakA mutant. Because exposure to unsaturated fatty acids probably initiates a stress response, we investigated the role of the alternative sigma factor σ^B and determined if it is necessary for the fatty acid resistance observed in the fakA mutant. Collectively, this study demonstrates that the inability to incorporate unsaturated fatty acids leads to increased resistance to those fatty acids, and that resistance requires a σ^B stress response.

Prevalence of Escherichia coli strains resistance to antibiotics in wound infections and raw milk

Antibiotic-resistant Escherichia coli strains including extended-spectrum β-lactamase (ESBL) isolates are globally widespread in medical, food, and environmental sources. Some of these strains are considered the most pathogenic bacteria in humans. The present work examined the predominance of antibiotic resistance in E. coli strains in wound infections comparing with E. coli strains isolated from a raw milk as a potential source of those strains. The wound infections included abdomen, anus, arm, back, buttock, chest, foot, hand, head, leg, lung, mouth, neck, penis, thigh, toe, and vagina infections. In total, 161 and 153 isolates identified as E. coli were obtained from wound infections and raw milk, respectively. A Vitek 2 system innovated by bioMérieux, France was applied to perform the identification and susceptibility tests. The E. coli isolates that have ability to produce ESBL were detected by an ESBL panel and NO45 card (bioMérieux). Over half of the E. coli were from abdomen, back, and buttock wound infections. More than 50%of the E. coli isolates obtained from wound infections were resistant to cefazolin, ampicillin, cefuroxime, ciprofloxacin, mezlocillin, moxifloxacin, piperacillin, and tetracycline; 70% of the isolates from wound infections and 0% of the isolates from raw milk were E. coli isolates produced ESBL. The data showed that the strains resistance to multi-antibiotic and produced ESBL are more widespread among wound infections than in raw milk.

Cubosomes for topical delivery of the antimicrobial peptide LL-37

In this study, the use of cubosomes for topical delivery of the antimicrobial peptide (AMP) LL-37 was investigated. Topical delivery of AMPs is of great interest for treatment of skin infections caused by bacteria, such as Staphylococcus aureus. AMP containing cubosomes were produced by three different preparation protocols and compared: (i) pre-loading, where LL-37 was incorporated into a liquid crystalline gel, which thereafter was dispersed into nanoparticles, (ii) post-loading, where LL-37 was let to adsorb onto pre-formed cubosomes, and (iii) hydrotrope-loading, where LL-37 was incorporated during the spontaneously formed cubosomes in an ethanol/glycerol monooleate mixture. Particle size and size distribution were analyzed using dynamic light scattering (DLS), liquid crystalline structure by small angle x-ray scattering (SAXS) and release of LL-37 by a fluorescamine assay. Proteolytic protection of LL-37 as well as bactericidal effect after enzyme exposure was investigated. The skin irritation potential of cubosomes was examined by an in vitro epidermis model. Finally, the bacterial killing property of the cubosomes was examined by an ex vivo pig skin wound infection model with Staphylococcus aureus. Data showed that a high loading of LL-37 induced formation of vesicles in case of cubosomes prepared by sonication (pre-loading). No release of LL-37 was observed from the cubosomes, indicating strong association of the peptide to the particles. Proteolysis studies showed that LL-37 was fully protected against enzymatic attacks while associated with the cubosomes, also denoting strong association of the peptide to the particles. As a consequence, bactericidal effect after enzyme exposure remained, compared to pure LL-37 which was subjected to proteolysis. No skin irritation potential of the cubosomes was found, thus enabling for topical administration. The ex vivo wound infection model showed that LL-37 in pre-loaded cubosomes killed bacteria most efficient.

Management of complicated skin and soft tissue infections with a special focus on the role of newer antibiotics

Complicated skin and soft tissue infections (cSSTIs) represent the severe form of infectious disease that involves deeper soft tissues. Involvement of methicillin-resistant Staphylococcus aureus (MRSA) further complicates cSSTI with increased hospitalization, health care costs, and overall mortality. Various international guidelines provide recommendations on the management of cSSTIs, with the inclusion of newer antibiotics. This literature-based review discusses the overall management of cSSTI, including appropriate use of antibiotics in clinical practice. Successful treatment of cSSTIs starts with early and precise diagnosis, including identification of causative pathogen and its load, determination of infection severity, associated complications, and risk factors. The current standard-of-care for cSSTIs involves incision, drainage, surgical debridement, broad-spectrum antibiotic therapy, and supportive care. In recent years, the emergence of newer antibiotics (eg, ceftaroline, tigecycline, daptomycin, linezolid, etc) has provided clinicians wider options of antimicrobial therapy. Selection of antibiotics should be based on the drug characteristics, effectiveness, safety, and treatment costs, alongside other aspects such as host factors and local multidrug resistance rates. However, larger studies on newer antibiotics are warranted to refine the decision making on the appropriate antimicrobial therapy. Local Antimicrobial Stewardship Program strategies in health care settings could guide clinicians for early initiation of specific treatments to combat region-specific antimicrobial resistance, minimize adverse effects, and to improve outcomes such as reduction in Clostridium difficile infections. These strategies involving iv-to-oral switch, de-escalation to narrow-spectrum antibiotics, and dose optimization have an impact on the overall improvement of cSSTI therapy outcomes, especially in countries like Singapore that has a high disease burden.

Prevalence of methicillin resistant Staphylococcus aureus, multidrug resistant and extended spectrum β-lactamase producing gram negative bacilli causing wound infections at a tertiary care hospital of Nepal

Background

Treatment and prevention of wound infection continues to be a challenging issue in clinical settings of Nepal especially in the context of globally growing problem of antimicrobial resistance. Study on opportunistic pathogens and sensitivity to commonly prescribed local antimicrobial agents are cardinal to reduce the disease burden of wound infections. The aim of this study was to determine the prevalence and antimicrobial susceptibility pattern of methicillin resistant Staphylococcus aureus (MRSA) and extended spectrum β-lactamase (ESBL) producing bacteria from wound infections of patients at a tertiary care hospital in Nepal.

Methods

Pus specimens were processed using standard microbiological procedures. Antimicrobial susceptibility test was performed following the modified Kirby Bauer disc diffusion technique. Clinical information of patients was obtained from preformed questionnaire and hospital record.

Results

One hundred eighty two pus specimens from wounds of different body parts: leg, hand, backside, abdominal part, foot, breast and chest, head and neck region were collected and analyzed; 113 bacterial isolates were isolated showing the overall bacterial growth rate of 62%, where the highest rate was among patients of ≤10 years age group (82.1%). A higher rate (68.5%) of bacterial isolates were from inpatients (p < 0.05). Among 116 bacterial isolates, Staphylococcus aureus was the most predominant bacteria (56.9%) followed by Escherichia coli (8.6%), coagulase negative staphylococci (7.8%), Acinetobacter spp. (5.2%), Klebsiella pneumoniae (5.2%), Pseudomonas aeruginosa (4.3%), Enterococcus spp. (4.3%), Citrobacter freundii (2.6%), Proteus vulgaris (1.6%) and P. mirabilis (0.9%). Both Gram positive (73.3%) and negative (78.8%) isolates showed high frequency of sensitive to gentamycin.

Conclusion

Among S. aureus isolates, 60.6% were MRSA strains, whereas 40% of K. pneumoniae and 33.3% of C. freundii were ESBL producing bacteria followed by E. coli (25%). It is thus paramount to address the burden of silently and speedily increasing infections caused by drug resistant strains of MRSA and ESBL in Nepal.

Structure-activity relationships of pyrazole-4-carbodithioates as antibacterials against methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of serious hospital-acquired infections and is responsible for significant morbidity and mortality in residential care facilities. New agents against MRSA are needed to combat rising resistance to current antibiotics. We recently reported 5-hydroxy-3-methyl-1-phenyl-1H-pyrazole-4-carbodithioate (HMPC) as a new bacteriostatic agent against MRSA that appears to act via a novel mechanism. Here, twenty nine analogs of HMPC were synthesized, their anti-MRSA structure-activity relationships evaluated and selectivity versus human HKC-8 cells determined. Minimum inhibitory concentrations (MIC) ranged from 0.5 to 64 μg/mL and up to 16-fold selectivity was achieved. The 4-carbodithioate function was found to be essential for activity but non-specific reactivity was ruled out as a contributor to antibacterial action. The study supports further work aimed at elucidating the molecular targets of this interesting new class of anti-MRSA agents.

Treatment Strategies for Infected Wounds

The treatment of skin wounds is a key research domain owing to the important functional and aesthetic role of this tissue. When the skin is impaired, bacteria can soon infiltrate into underlying tissues which can lead to life-threatening infections. Consequently, effective treatments are necessary to deal with such pathological conditions. Recently, wound dressings loaded with antimicrobial agents have emerged as viable options to reduce wound bacterial colonization and infection, in order to improve the healing process. In this paper, we present an overview of the most prominent antibiotic-embedded wound dressings, as well as the limitations of their use. A promising, but still an underrated group of potential antibacterial agents that can be integrated into wound dressings are natural products, especially essential oils. Some of the most commonly used essential oils against multidrug-resistant microorganisms, such as tea tree, St. John's Wort, lavender and oregano, together with their incorporation into wound dressings are presented. In addition, another natural product that exhibits encouraging antibacterial activity is honey. We highlight recent results of several studies carried out by researchers from different regions of the world on wound dressings impregnated with honey, with a special emphasis on Manuka honey. Finally, we highlight recent advances in using nanoparticles as platforms to increase the effect of pharmaceutical formulations aimed at wound healing. Silver, gold, and zinc nanoparticles alone or functionalized with diverse antimicrobial compounds have been integrated into wound dressings and demonstrated therapeutic effects on wounds.

The Staphylococcus aureus Extracellular Adherence Protein Eap Is a DNA Binding Protein Capable of Blocking Neutrophil Extracellular Trap Formation

The extracellular adherence protein (Eap) of Staphylococcus aureus is a secreted protein known to exert a number of adhesive and immunomodulatory properties. Here we describe the intrinsic DNA binding activity of this multifunctional secretory factor. By using atomic force microscopy, we provide evidence that Eap can bind and aggregate DNA. While the origin of the DNA substrate (e.g., eukaryotic, bacterial, phage, and artificial DNA) seems to not be of major importance, the DNA structure (e.g., linear or circular) plays a critical role with respect to the ability of Eap to bind and condense DNA. Further functional assays corroborated the nature of Eap as a DNA binding protein, since Eap suppressed the formation of "neutrophil extracellular traps" (NETs), composed of DNA-histone scaffolds, which are thought to function as a neutrophil-mediated extracellular trapping mechanism. The DNA binding and aggregation activity of Eap may thereby protect S. aureus against a specific anti-microbial defense reaction from the host.

Pharmacological Evaluation of Selected Medicinal Plants Used in the Management of Oral and Skin Infections in Ebem-Ohafia District, Abia State, Nigeria

Oral and skin infections contribute significantly to the global health challenges responsible for the current trend of increased morbidity and premature death. The purpose of this study was to document medicinal plants used in the management of oral and skin infections in Ebem-Ohafia Local Government Area (LGA), Abia State, and to characterize the in vitro antioxidant and antibacterial activity. The thin layer chromatography (TLC) profiling of ten of the selected folklore medicine was carried out using a various solvent system of different polarity index. The antioxidant capacity of the plant extracts was evaluated using chemical-based methods, and its antibacterial effect was investigated using disc diffusion and microdilution methods. Sixty-one plant species belonging to 26 families were discovered, and the most frequently cited species are Euphorbiaceae (18.03%), Fabaceae (11.47%), and Asteraceae (11.47%). All the plant extracts showed a promising free radical scavenging activity and efficient ferric reducing antioxidant power in a concentration-dependent manner possibly due to their richness in polyphenol with TLC profiling showing maximum three bands of phytochemicals. Also, the plant extracts exhibited a mild to weak antibacterial activity against our panel of bacterial strains having MIC values ranging from 256 to > 512 μg/ mL reflected in their zone of inhibition at 10 μg/disc. The data obtained for Breynia nivosa (BN), Eleusine indica (EI), Cassia alata (CA), Chromolaena odorata (CO), and Acalypha hispida (AH) extracts substantiate the traditional use of these herbal remedies in the region and open the possibility for the development of cheaper and affordable drugs in the treatment of oral and skin infections. Further studies are needed to identify active ingredient with strong antibacterial and antioxidant capacities along with their molecular mechanisms.

Effect of bacterial components of mixed culture supernatants of planktonic and biofilm Pseudomonas aeruginosa with commensal Escherichia coli on the neutrophil response in vitro

Pseudomonas aeruginosa (PA) responsible for acute and chronic infections often forms a well-organized bacterial population with different microbial species including commensal strains of Escherichia coli. Bacterial extracellular components of mixed culture can modulate the influence of bacteria on the neutrophil functions. The objective of this study was to compare the effect of pyocyanin, pyoverdine, LPS, exopolysaccharide of single species and mixed culture supernatants of PA strains and E. coli K12 on microbicidal, secretory activity of human neutrophils in vitro. Bacterial components of E. coli K12 in mixed supernatants with 'biofilm' PA strains (PA ATCC, PA BALG) enhanced short-term microbicidal mechanisms and inhibited neutrophil secretion delayed in time. The influence of 'planktonic' PA (PA 9-3) exometabolites in mixed culture is almost mimicked by E. coli K12 effect on functional neutrophil changes. This investigation may help to understand some of the mechanisms of neutrophil response to mixed infections of different PA with other bacteria species.

The burden of common infections in children and adolescents with diabetes mellitus: A Pediatric Health Information System study

BACKGROUND

People with diabetes mellitus (DM) have increased infection risk. The healthcare utilization of pediatric and adolescent diabetic patients with infection is not well defined. This study evaluates the number of pediatric and adolescent patients with DM that seek medical treatment for infection management and assesses its socioeconomic impact.

METHODS

A retrospective analysis was performed using the Pediatric Health Information System (PHIS) database on children and adolescents with DM who presented to the Emergency Department (ED) or were hospitalized for infection management from 2008 to 2014. The PHIS database collects admission, demographic, and economic data from 44 freestanding children's hospitals across the United States.

RESULTS

In total, 123 599 diabetic patient encounters were identified (77% type 1 DM, 23% type 2 DM). ED visits and hospitalizations for type 1 DM and type 2 DM increased throughout the study period. Total charges for these encounters were greater than $250 million dollars per year and increased each year. Infection encounters make up more than 30% of that cost while accounting for only 14% of the visits. Respiratory infections were the most common type of infection followed by skin and soft tissue infections for both ED care and inpatient hospitalizations. Patients with infections had longer hospital length of stay and higher cost per day than those without infections.

CONCLUSIONS

Children and adolescents with type 1 and type 2 DM commonly present to the ED and require hospitalization for infection evaluation and management. Encounters with infection make up a large proportion of a growing economic burden on the United States' healthcare system. As the prevalence of DM grows, this burden can be expected to become even more significant. Cost-effective strategies for the prevention of infection in pediatric patients with DM are needed.

Emerging treatment options for acute bacterial skin and skin structure infections: focus on intravenous delafloxacin

The increase in hospitalization due to acute bacterial skin and skin structure infections (ABSSSI) caused by resistant pathogens supports the need for new treatment options. Antimicrobial options for ABSSSI that provide broad-spectrum coverage, including gram-negative pathogens and multidrug-resistant gram-positive bacteria, such as methicillin-resistant Staphylococcus aureus (MRSA), are limited. Delafloxacin is a novel fluoroquinolone available as intravenous and oral formulations and is characterized by an increased efficacy in acidic environments and activity on bacterial biofilm. Delafloxacin displays enhanced in vitro activity against MRSA, and enterococci, while maintaining efficacy against gram-negative pathogens and anaerobes. Delafloxacin has been studied for the treatment of ABSSSI and respiratory infections. Phase III studies have demonstrated noninferiority of delafloxacin compared to vancomycin, linezolid, tigecycline, and the combination of vancomycin plus aztreonam in the treatment of ABSSSI. Due to its favorable pharmacokinetic characteristics, the wide spectrum of action, and the potential for sequential therapy, delafloxacin represents a promising option in the empirical and targeted treatment of ABSSSI, both in hospital- and in community-based care.

Optimizing skin and skin structure infection outcomes: considerations of cost of care

INTRODUCTION

Skin and skin structure infections (SSSIs) refer to a collection of clinical infectious syndromes involving layers of skin and associated soft tissues. Although associated with less morbidity and mortality than other common skin infections, SSSIs represent a significant increasing source of healthcare expense, with a prevalence of 500 episodes per 10,000 patient-years in the United States resulting in burdening health care systems, of approximately $6 billion annually.

AREAS COVERED

Opportunities to reduce costs of care associated with SSSI are highlighted, including transitions of care and avoiding unnecessary hospital admissions. Moreover, we reviewed new antibiotics (e.g. single dose glycopeptides), and the impact of consulting specialists in the emergency department on SSSI treatment outcomes.

EXPERT COMMENTARY

New healthcare models and payment strategies combined with new therapeutics are challenging norms of care. Newer drugs to treat skin infections can move a substantive percent of patients previously admitted to hospital care to the outpatient setting. Additionally, patients can be managed with oral or one time intravenous regimens, improving the likelihood of patient adherence and satisfaction. These variables need to be weighed against added acquisition costs and the development of thoughtful algorithms is needed to direct care and optimize treatment, cost, and patient satisfaction.

A case of methicillin-resistant Staphylococcus aureus wound infection: phylogenetic analysis to establish if nosocomial or community acquired

Methicillin‐resistant Staphylococcus aureus (MRSA) infection is rapidly increasing in both hospital and community settings. A 71‐year‐old man admitted at the Department of Orthopaedics and Trauma Surgery, University Campus Bio‐Medico of Rome, with MRSA wound infection consequent to orthopedic surgery was studied and the MRSA transmission evaluated by phylogenetic analysis.

The role of methicillin-resistant Staphylococcus aureus in skin and soft tissue infections

PURPOSE OF REVIEW

Methicillin-resistant Staphylococcus aureus (MRSA) has become a major public health issue worldwide over the last years. MRSA is frequently implicated in the development of skin and soft tissue infections, leading to significant increases in morbidity, mortality and overall healthcare costs.

RECENT FINDINGS

In order to face the threat of MRSA, major changes in clinical management of skin and soft tissue infections are required. The identification of populations at risk for the acquisition of infections due to MRSA, together with the improvement of the diagnostic techniques, is paramount. Moreover, a number of new antimicrobials with activity against MRSA have been recently developed and approved for the treatment of skin and soft tissue infections, however, the use of the new drugs in the wide clinical practice remains limited.

SUMMARY

We reviewed the current epidemiology of MRSA in skin and soft tissue infections, with particular focus on implications for clinical management. The potential role of new antibiotic options against MRSA infections is also discussed.

2018 WSES/SIS-E consensus conference: recommendations for the management of skin and soft-tissue infections

Skin and soft-tissue infections (SSTIs) encompass a variety of pathological conditions that involve the skin and underlying subcutaneous tissue, fascia, or muscle, ranging from simple superficial infections to severe necrotizing infections. SSTIs are a frequent clinical problem in surgical departments. In order to clarify key issues in the management of SSTIs, a task force of experts met in Bertinoro, Italy, on June 28, 2018, for a specialist multidisciplinary consensus conference under the auspices of the World Society of Emergency Surgery (WSES) and the Surgical Infection Society Europe (SIS-E). The multifaceted nature of these infections has led to a collaboration among general and emergency surgeons, intensivists, and infectious disease specialists, who have shared these clinical practice recommendations.

Synergistic Antimicrobial Interaction between Honey and Phage against Escherichia coli Biofilms

Chronic wounds afford a hostile environment of damaged tissues that allow bacterial proliferation and further wound colonization. Escherichia coli is among the most common colonizers of infected wounds and it is a prolific biofilm former. Living in biofilm communities, cells are protected, become more difficult to control and eradicate, and less susceptible to antibiotic therapy. This work presents insights into the proceedings triggering E. coli biofilm control with phage, honey, and their combination, achieved through standard antimicrobial activity assays, zeta potential and flow cytometry studies and further visual insights sought by scanning electron microscopy and transmission electron microscopy. Two Portuguese honeys (PF2 and U3) with different floral origin and an E. coli-specific phage (EC3a), possessing depolymerase activity, were tested against 24- and 48-h-old biofilms. Synergic and additive effects were perceived in some phage-honey experiments. Combined therapy prompted similar phenomena in biofilm cells, visualized by electron microscopy, as the individual treatments. Honey caused minor membrane perturbations to complete collapse and consequent discharge of cytoplasmic content, and phage completely destroyed cells leaving only vesicle-like structures and debris. Our experiments show that the addition of phage to low honey concentrations is advantageous, and that even fourfold diluted honey combined with phage, presents no loss of antibacterial activity toward E. coli. Portuguese honeys possess excellent antibiofilm activity and may be potential alternative therapeutic agents in biofilm-related wound infection. Furthermore, to our knowledge this is the first study that assessed the impacts of phage-honey combinations in bacterial cells. The synergistic effect obtained was shown to be promising, since the antiviral effect of honey limits the emergence of phage resistant phenotypes.

Multidrug and Mupirocin Resistance in Environmental Methicillin-Resistant Staphylococcus aureus (MRSA) Isolates from Homes of People Diagnosed with Community-Onset MRSA Infection

Patients with community-onset (CO) methicillin-resistant Staphylococcus aureus (MRSA) infections contribute to MRSA contamination of the home environment and may be reexposed to MRSA strains from this reservoir. This study evaluates One Health risk factors, which focus on the relationship between humans, animals, and the environment, for the increased prevalence of multiple antimicrobial-resistant MRSA isolates in the home environment. During a trial of patients with CO-MRSA infection, MRSA was isolated from the household environment at the baseline and 3 months later, following randomization of patients and household members to mupirocin-based decolonization therapy or an education control group. Up to two environmental MRSA isolates collected at each visit were tested. MRSA isolates were identified in 68% (65/95) of homes at the baseline (n = 104 isolates) and 51% (33/65) of homes 3 months later (n = 56 isolates). The rates of multidrug resistance (MDR) were 61% among isolates collected at the baseline and 55% among isolates collected at the visit 3 months later. At the baseline, 100% (14/14) of MRSA isolates from rural homes were MDR. While antimicrobial use by humans or pets was associated with an increased risk for the isolation of MDR MRSA from the environment, clindamycin use was not associated with an increased risk for the isolation of MDR MRSA. Incident low-level mupirocin-resistant MRSA strains were isolated at 3 months from 2 (5%) of 39 homes that were randomized to mupirocin treatment but none of the control homes. Among patients recently treated for a CO-MRSA infection, MRSA and MDR MRSA were common contaminants in the home environment. This study contributes to evidence that occupant use of antimicrobial drugs, except for clindamycin, is associated with MDR MRSA in the home environmental reservoir. (This study has been registered at ClinicalTrials.gov under registration no. NCT00966446.)IMPORTANCE MRSA is a common bacterial agent implicated in skin and soft tissue infections (SSTIs) in both community and health care settings. Patients with CO-MRSA infections contribute to environmental MRSA contamination in these settings and may be reexposed to MRSA strains from these reservoirs. People interact with natural and built environments; therefore, understanding the relationships between humans and animals as well as the characteristics of environmental reservoirs is important to advance strategies to combat antimicrobial resistance. Household interactions may influence the frequency and duration of exposure, which in turn may impact the duration of MRSA colonization or the probability for recurrent colonization and infection. Therefore, MRSA contamination of the home environment may contribute to human and animal recolonization and decolonization treatment failure. The aim of this study was to evaluate One Health risk factors that may be amenable to intervention and may influence the recovery of MDR and mupirocin resistance in CO-MRSA isolates.

Clinical and pharmacokinetic drug evaluation of delafloxacin for the treatment of acute bacterial skin and skin structure infections

INTRODUCTION

In the era of multi-drug resistant pathogens, the adequate treatment of skin and skin structure infections remains a challenge for clinicians. Delafloxacin, with its broad spectrum against Gram-positive, Gram-negative and anaerobic organisms, represents a new therapeutic option in this setting, especially when coverage of methicillin-resistant Staphylococcus aureus is required in the empirical or targeted approach. Areas covered: In this drug evaluation, the Authors have reviewed the pharmacokinetic and pharmacodynamic characteristics of delafloxacin. In addition, recent data on clinical efficacy and safety from clinical trials have been included. Expert opinion: Delafloxacin represents an attractive therapeutic option due to a broad antimicrobial and favorable pharmacokinetic and pharmacodynamic profile. Several in vitro studies have demonstrated the low potential for resistance selection if used in empirical regimens. Delafloxacin is a promising candidate for the treatment of Gram-positive infections, especially if co-infection with other pathogens is suspected. This is because of the very low MIC of the agent for Gram-positive (including MRSA) and anaerobic bacteria and because of the wide spectrum of activity against Gram-negative organisms. For these interesting microbiological and PK/PD characteristics we expect future uses of this drug in other indications such as diabetic foot infection, osteomyelitis, prosthetic joint infections, abdominal infections and central nervous system infections.

Virulence analysis of Staphylococcus aureus in a rabbit model of infected full-thickness wound under negative pressure wound therapy

The aim of this study was to evaluate the virulence of Staphylococcus aureus in a controlled animal study using the standard sterile gauze and negative pressure wound therapy (NPWT), including activation of agr, gene expression and production of virulence foctors and depth of bacterial invasion. The tissue specimens were harvested on days 0 (6 h after bacterial inoculation), 2, 4, 6, and 8 at the center of wound beds. Laser scanning confocal microscopy was performed to obtain bioluminescent images which were used to measure the depth of bacterial invasion. The agrA expression of S.aureus and the transcription and production of virulence factors including Eap, Spa and α-toxin were significantly different. The bacterial invasion depth was significantly less with effect of NPWT. The markedly different activation of quorum sensing systems that enable cell-to-cell communication and regulation of numerous colonization and virulence factors result in distinct gene expression and pathogenicity over time in different microenvironment. Thus, the agr system represents a fundamental regulatory paradigm that can encompass different adaptive strategies and accommodate horizontally acquired virulence determinants.

Genomic epidemiology of methicillin-susceptible Staphylococcus aureus across colonisation and skin and soft tissue infection

OBJECTIVES

Staphylococcus aureus skin and soft tissue infection (Sa-SSTI) places a significant burden on healthcare systems. New Zealand has a high incidence of Sa-SSTI, and here most morbidity is caused by a polyclonal methicillin-susceptible (MSSA) bacterial population. However, MSSA also colonise asymptomatically the cornified epithelia of approximately 20% of the population, and their divide between commensalism and pathogenicity is poorly understood. We aimed to see whether MSSA are genetically differentiated across colonisation and SSTI; and given the close interactions between people and pets, whether strains isolated from pets differ from human strains.

METHODS

We compared the genomes of contemporaneous colonisation and clinical MSSA isolates obtained in New Zealand from humans and pets.

RESULTS

Core and accessory genome comparisons revealed a homogeneous bacterial population across colonisation, disease, humans, and pets. The rate of MSSA colonisation in dogs was comparatively low (5.4%).

CONCLUSIONS

In New Zealand, most Sa-SSTI morbidity is caused by a random sample of the colonising MSSA population, consistent with the opportunistic infection model rather than the paradigm distinguishing strains according to their pathogenicity. Thus, studies of the factors determining colonisation and immune-escape may be more beneficial than comparative virulence studies. Contact with house-hold pets may pose low zoonotic risk.

The mythos of laudable pus along with an explanation for its origin

The presence of pus is one of the most easily recognizable signs of an infection. However, for several centuries suppuration, known as ‘laudable pus,’ was believed to be a sign of a healthy, healing wound. This historical misconception can be explained by the difference in the presentation of a necrotizing soft tissue infection versus other more common skin and soft tissue infections. Chronic wound infections, due to pyogenic bacteria, typically produce large amounts of thick, whitish-yellow pus. On the other hand, necrotizing soft tissue infections, despite their severe mortality and morbidity, are devoid of pus in the traditional sense. What the ancient medical observers recognized was the fact that pus is not characteristic of this subset of incredibly severe infections. This is an important distinction to remember when evaluating an infection, even today.

Minimally Invasive Incision and Drainage Technique in the Treatment of Simple Subcutaneous Abscess in Adults

A minimally invasive (MI) approach using small incisions and vessel loops for drainage of simple perianal abscesses has been described in the pediatric population with decreased postoperative pain and comparable results to the traditional incision and drainage (I&D). The hypothesis was MI I&D will yield similar outcomes in adults. Patients who underwent I&D of perianal abscesses at an urban hospital from January 2008 to December 2015 were identified by Current Procedural Terminology code. Patients below 18 years of age, with inflammatory bowel diseases, or fistulae were excluded. Recurrences, readmissions, operative time, length of stay, complications, and costs were compared. There were 47 traditional and 96 MI I&D with no significant differences in demographics, average body mass index, and abscess size. No significant differences were noted in recurrences, readmissions, length of stay, operative time, or costs (P > 0.05). Postoperative complications occurred more frequently in the traditional group (P < 0.01) with a lower rate of follow-up (P < 0.05). MI I&D for simple anal abscesses in adults is associated with better compliance and fewer complications than the traditional approach. Although further studies are needed to determine if MI I&D confers superiority, this approach should be considered as first-line treatment for uncomplicated perirectal abscesses in adults.