Clinical outcomes in patients with critical limb-threatening ischemia and infected ulcers following endovascular therapy are pathogen dependent: A single-center experience from 2012 to 2021

BACKGROUND

Patients with critical limb-threatening ischemia (CLTI) and infected leg ulcers are at risk of amputation and postinterventional sepsis.

METHODS

This retrospective, single-center study included patients with CLTI and infected leg ulcers who underwent endovascular treatment (EVT) between 2012 and 2021.

RESULTS

The study included 712 patients, 286 (40.2%) of whom underwent amputation (minor, n = 212; major, n = 74). Gram-negative bacteria (GNB) were significantly more prevalent in amputees (36.4% vs 30.9%, p < 0.05). Patients with gram-positive bacteria (GPB) had a 4-year freedom from any amputation rate of 72% (95% CI 64-81%) compared to 52% (95% CI 42-66%) in patients with GNB identification (p < 0.05). Cox proportional regression analysis showed that GNB, male sex, mean Wound, Ischemia, and foot Infection (WIfI) score, diabetes mellitus, and end-stage renal disease were independently and positively associated with amputation (p < 0.05). The mean WIfI score and end-stage renal disease were independently and positively associated with death from any cause (p < 0.05). Staphylococcus aureus or GNB, end-stage renal disease, and diabetes mellitus were independent risk factors for sepsis after EVT (p < 0.05). Inpatient-administered antibiotic regimes had significantly higher microbiological activity in cases of GPB identification compared to GNB identification (28% vs 9%, p < 0.05).

CONCLUSION

Although the isolation of both GNB and S. aureus is a risk factor for sepsis following EVT, the isolation of GNB is independently associated with higher rates of amputation, demonstrating the importance of identifying pathogens to recognize patients at high risk.

Tissue Penetration of Antimicrobials in Intensive Care Unit Patients: A Systematic Review-Part II

In patients that are admitted to intensive care units (ICUs), the clinical outcome of severe infections depends on several factors, as well as the early administration of chemotherapies and comorbidities. Antimicrobials may be used in off-label regimens to maximize the probability of therapeutic concentrations within infected tissues and to prevent the selection of resistant clones. Interestingly, the literature clearly shows that the rate of tissue penetration is variable among antibacterial drugs, and the correlation between plasma and tissue concentrations may be inconstant. The present review harvests data about tissue penetration of antibacterial drugs in ICU patients, limiting the search to those drugs that mainly act as protein synthesis inhibitors and disrupting DNA structure and function. As expected, fluoroquinolones, macrolides, linezolid, and tigecycline have an excellent diffusion into epithelial lining fluid. That high penetration is fundamental for the therapy of ventilator and healthcare-associated pneumonia. Some drugs also display a high penetration rate within cerebrospinal fluid, while other agents diffuse into the skin and soft tissues. Further studies are needed to improve our knowledge about drug tissue penetration, especially in the presence of factors that may affect drug pharmacokinetics.

Antimicrobial Stewardship Programs: A Review of Strategies to Avoid Polymyxins and Carbapenems Misuse in Low Middle-Income Countries

Antibiotics misuse and overuse are concerning issues worldwide, especially in low middle-income countries. These practices contribute to the increasing rates of antimicrobial resistance. One efficient strategy to avoid them is antimicrobial stewardship programs. In this review, we focus on the possible approaches to spare the prescription of polymyxins and carbapenems for the treatment of Acinetobacter baumannii, carbapenem-resistant Enterobacterales, and Pseudomonas aeruginosas infections. Additionally, we highlight how to implement cumulative antibiograms and biomarkers to a sooner de-escalation of antibiotics.

Antibiotics in Necrotizing Soft Tissue Infections

Necrotizing soft tissue infections (NSTIs) are rare life-threatening bacterial infections characterized by an extensive necrosis of skin and subcutaneous tissues. Initial urgent management of NSTIs relies on broad-spectrum antibiotic therapy, rapid surgical debridement of all infected tissues and, when present, treatment of associated organ failures in the intensive care unit. Antibiotic therapy for NSTI patients faces several challenges and should (1) carry broad-spectrum activity against gram-positive and gram-negative pathogens because of frequent polymicrobial infections, considering extended coverage for multidrug resistance in selected cases. In practice, a broad-spectrum beta-lactam antibiotic (e.g., piperacillin-tazobactam) is the mainstay of empirical therapy; (2) decrease toxin production, typically using a clindamycin combination, mainly in proven or suspected group A streptococcus infections; and (3) achieve the best possible tissue diffusion with regards to impaired regional perfusion, tissue necrosis, and pharmacokinetic and pharmacodynamic alterations. The best duration of antibiotic treatment has not been well established and is generally comprised between 7 and 15 days. This article reviews the currently available knowledge regarding antibiotic use in NSTIs.

Cotrimoxazole and clindamycin in skin and soft tissue infections

PURPOSE OF REVIEW

The aim of this study was to present recent microbiological, experimental, clinical and tolerance data for cotrimoxazole and clindamycin in the specific field of skin and soft tissue infections (SSTIs).

RECENT FINDINGS

Staphylococcus aureus and streptococci remain the leading cause of SSTIs. Cotrimoxazole is a good anti-Gram-positive agent with preserved activity against methicillin-susceptible and methicillin-resistant S. aureus (MRSA) and streptococci. Although clindamycin has good methicillin-susceptible S. aureus activity, a growing number of resistant MRSA and streptococci have been reported. Strong experimental data support the antitoxin activity of clindamycin, but clinical observations remain scarce. Several recent randomized trials involving cotrimoxazole and/or clindamycin demonstrate the efficacy and tolerance of both drugs. The oral formulation of both drugs may facilitate the implementation of early switch and early discharge protocols in clinical practice.

SUMMARY

Recent publications demonstrate that cotrimoxazole and clindamycin remain reliable and realistic therapeutic approaches for SSTIs.

LC-MS/MS method for nine different antibiotics

BACKGROUND AND AIMS

TDM of antibiotics can bring benefits to patients and healthcare systems by providing better treatment and saving healthcare resources. We aimed to develop a multi-analyte method for several diverse antibiotics using LC-MS/MS.

MATERIALS AND METHODS

Sample preparation consisted of protein precipitation with methanol, dilution and online extraction using a Turboflow Cyclone column. Separation was performed on a Synergi 4 µm Max RP column and deuterated forms of three antibiotics were used as internal standards.

RESULTS

We present a LC-MS/MS method for the quantitative determination of nine antibiotics, including five cephalosporins, the carbapenem ertapenem, the fluoroquinolone ciprofloxacin as well as the combination drug trimethoprim-sulfamethoxazole from plasma. Additionally, unbound ertapenem and cefazolin were analyzed in plasma water after ultrafiltration using plasma calibrators. Results from routine TDM show the applicability of the method.

CONCLUSION

The presented method is precise and accurate and was introduced in a university hospital, permitting fast TDM of all nine analytes. It was also used in a clinical study for measuring cefazolin free and total concentrations.

Efficacy of cotrimoxazole (Sulfamethoxazole-Trimethoprim) as a salvage therapy for the treatment of bone and joint infections (BJIs)

INTRODUCTION

Cotrimoxazole (Sulfamethoxazole-Trimethoprim, SXT) has interesting characteristics for the treatment of bone and joint infection (BJI): a broad spectrum of activity with adequate bone diffusion and oral and intravenous formulations. However, its efficacy and safety in BJIs are poorly documented and its use remains limited.

METHODS

We conducted a retrospective study in 2 reference centers for BJIs from 2013 to 2018 among patients treated with SXT for a BJI. Data were collected from patient's medical charts. Outcomes and adverse events were evaluated at day (D)7, D45 and D90.

RESULTS

We analyzed 51 patients with a mean age of 60 ± 20 (SD) years of which 76% presented with an orthopedic device infection (ODI). Gram-negative bacilli (GNB) were involved in 47% of BJIs (n = 24). Moreover, they were often polymicrobial infections (41%). Doses of SXT ranged from 800/160mg bid (61%; n = 31) to 800/160mg tid (39%; n = 20). Median SXT treatment duration was 45 days (IQR 40-45). SXT was part of a dual therapy in 84% of patients (n = 43), associated mainly with fluoroquinolones (n = 17) or rifampicin (n = 14). Outcome was favorable at D7 in 98% (n = 50), at D45 in 88.2% (n = 45) and at D90 in 78.4% (n = 40). The second agent combined with SXT was not an independent factor of favorable outcome (p = 0.97). Adverse events were reported in 8% (n = 4) of patients, with a median of 21 days (IQR 20-30) from SXT initiation and led to discontinuation (n = 3).

CONCLUSION

SXT appears to be effective for treatment of BJIs as a salvage therapy, even in GNB or polymicrobial infection, including ODI. Further data are needed to confirm SXT efficacy as an alternative oral regimen in BJIs.

Antibiotic exposure at the site of infection: principles and assessment of tissue penetration

Introduction: Since the majority of bacterial infections occur at sites outside the bloodstream, antibiotic tissue concentrations are of significant relevance to optimize treatment. The aim of this review is to aid the clinician in choosing optimal regimens for the treatment of extravascular infections. Areas covered: We discuss the principles of antibiotic tissue penetration and assess different approaches to obtain data on this subject. Finally, we present tissue penetration data for several relevant groups of antibiotic agents in a number of extravascular sites. Data were obtained from an extensive literature search in PubMed until February 2019. Expert opinion: There is still a long way to go before reliable information about tissue penetration of antibiotics is sufficiently available to serve as a basis for the design of optimal strategies for drug and dose selection. At this moment, there is a lack of robust data on tissue penetration, where both the sampling and measurement techniques as well as the relationship between tissue concentrations and clinical outcome of antibiotic treatment have to be better defined.

Diabetic Foot Infection: Causative Pathogens and Empiric Antibiotherapy Considerations—The Experience of a Tertiary Center

Most moderate-to-severe diabetic foot infections (DFIs) require hospitalization with urgent surgical approach and administration of empiric antibiotherapy. To ensure optimal antibiotic coverage, regular microbiological background updates are imperative. The purpose is to characterize the microbiological profile and the antibiotic sensitivity pattern of the DFI causative pathogens isolated within a specialized DFI unit of a tertiary hospital, in order to establish evidence-based policies regarding empirical antibiotic use. A cross-sectional study was conducted. Microbiological cultures and corresponding antibiotic sensitivity tests collected from moderate-to-severe DFIs as a first approach to the hospitalized patient were retrieved and analyzed during a 12-month period. Two groups were analyzed: inpatients that had been previously followed at the diabetic foot clinic of the hospital and inpatients without a previous contact with the hospital services. A total of 125 isolates obtained from 87 patients were deemed for analysis. Globally, a predominance of Gram-positive bacteria was observed (60%). Staphylococcus aureus was the most common pathogen. The global ratio of methicillin-sensitive S aureus to methicillin-resistant S aureus (MRSA) was 1.3:1, with similar findings in both groups. According to the antibiotic sensitivity test results, and within the recommended empiric antibiotic regimens for DFI, piperacillin/tazobactam seems to be the most suitable option. Gram-positive bacteria prevail as the main isolates in DFIs. Screening for MRSA-specific risk factors is mandatory. When going for a first empiric therapy, piperacillin/tazobactam is recommended in this institution, and an anti-MRSA agent should be added early, if necessary. We encourage continuous monitoring for the bacterial prevalence in Portuguese diabetic foot centers as it is paramount for the decision making regarding DFI protocols.

Clinical Determinants of Target Non-Attainment of Linezolid in Plasma and Interstitial Space Fluid: A Pooled Population Pharmacokinetic Analysis with Focus on Critically Ill Patients

OBJECTIVES

We aimed to assess linezolid pharmacokinetics in the plasma and interstitial space fluid (ISF) of patients with sepsis, diabetic foot infections or cystic fibrosis and healthy volunteers. The impacts of joint characteristics and disease on plasma and target-site exposure were to be identified together with the benefit of dose intensification in critically ill patients.

METHODS

Rich plasma (n = 1598) and ISF concentrations in subcutaneous adipose (n = 1430) and muscle tissue (n = 1089) measured by microdialysis were pooled from three clinical trials with 51 individuals receiving 600 mg of intravenous and oral linezolid. All data were analysed simultaneously by a population approach also considering methodological aspects of microdialysis. The impact of covariates on the attainment of the pharmacokinetic/pharmacodynamic targets, AUC/MIC = 100 (area under the concentration-time curve/minimum inhibitory concentration) and fT_>MIC = 99 % (time that unbound concentrations exceed the MIC), was assessed by deterministic and Monte Carlo simulations.

RESULTS

A two-compartment pharmacokinetic model with nonlinear elimination and tissue distribution factors accounting for differences between plasma and ISF concentrations adequately predicted all measurements. Clearance (CL) was highest in septic patients (11.2 L/h vs. CL_Healthy/CL_{Cystic fibrosis}/CL_Diabetic = 7.67/6.87/6.35 L/h). Penetration into subcutaneous adipose ISF was lowest in diabetic patients (-34.9 % compared with healthy volunteers). Creatinine clearance and total body weight further impacted linezolid exposure. To achieve timely efficacious therapy, front-loaded dosing and continuous infusion seemed beneficial in septic patients.

CONCLUSIONS

Our analysis suggests that after standard linezolid doses, particularly patients with sepsis and conserved renal function are at risk of not attaining pharmacokinetic/pharmacodynamic targets and would benefit from initial dose intensification.

Top 10 Myths Regarding the Diagnosis and Treatment of Cellulitis

BACKGROUND

Cellulitis is commonly treated in the emergency department (ED). Patients who present with cellulitis incur significant health care costs and may be overtreated with antibiotics. The accurate diagnosis and treatment of cellulitis plays an important role in cost-effective, high-quality medical care, as well as appropriate antibiotic utilization.

OBJECTIVE

We aim to describe common fallacies regarding cellulitis. We present 10 myths that result in misdiagnosis, overtreatment, or inappropriate empiric management of cellulitis. Clinical presentation, including swelling and redness, is explored in depth, along with incidence of community-acquired methicillin-resistance Staphylococcus aureus, management of tick bites, and effective antibiotic therapy for cellulitis.

DISCUSSION

Patients are often treated for cellulitis unnecessarily or inappropriately. Awareness of these myths will help guide providers in clinical decision making in order to effectively tailor treatment for these infections.

CONCLUSIONS

Cellulitis is not as simple as it might seem, and is commonly misdiagnosed in the ED. Noninfectious causes of local symptoms, including lymphedema, venous stasis, and deep vein thrombosis need to be considered. Cellulitis should be treated with empiric antimicrobial therapy based on patient risk factors and regional susceptibility patterns. This review will assist providers in managing cellulitis and avoiding treatment errors that lead to high costs, unwanted side effects for patients, and overuse of antibiotics.

Development of a Novel Collagen Wound Model To Simulate the Activity and Distribution of Antimicrobials in Soft Tissue during Diabetic Foot Infection

Diabetes has major implications for public health, with diabetic foot ulcers (DFUs) being responsible for significant morbidity and mortality. A key factor in the development of nonhealing ulcers is infection, which often leads to the development of biofilm, gangrene, and amputation. A novel approach to treating DFUs is the local release of antibiotics from calcium sulfate beads. We have developed a novel model system to study and compare the release and efficacy of antibiotics released locally, using collagen as a substrate for biofilm growth and incorporating serum to mimic the biochemical complexity of the wound environment. We found that our soft-tissue model supports the growth of a robust Pseudomonas aeruginosa biofilm, and that this was completely eradicated by the introduction of calcium sulfate beads loaded with tobramycin or gentamicin. The model also enabled us to measure the concentration of these antibiotics at different distances from the beads and in simulated wound fluid bathing the collagen matrix. We additionally found that a multidrug-resistant Staphylococcus aureus biofilm, nonsusceptible to antibiotics, nonetheless showed an almost 1-log drop in viable counts when exposed to calcium sulfate beads combined with antibiotics. Together, these data suggest that locally applied antibiotics combined with calcium sulfate provide surprising efficacy in diabetic foot infections and offer an effective alternative approach to infection management. Our study additionally establishes our new system as a biochemically and histologically relevant model that may be used to study the effectiveness of a range of therapies locally or systemically for infected DFUs.

Nocardia Arthritis: 3 Cases and Literature Review

Nocardia are Gram-positive filamentous bacteria responsible for infections ranging from opportunistic life-threatening disseminated diseases to chronic skin and soft-tissue infections.Even if virtually all organs can be infected, articular involvement is rare. Therefore, we report 3 recent cases and performed a literature review of cases of Nocardia arthritis in order to describe clinical features, therapeutic challenges, and outcome of these patients.Among 34 patients (31 in the literature plus our 3 cases), 21 (62%) were due to hematogenous dissemination, 9 (26%) were due to direct bacterial inoculation through the skin, and in 4 cases, the mechanism of infection was unknown. Four out of these 34 cases occurred on prosthetic joints.Whereas hematogenous infections mostly occurred in immunocompromised hosts (17 of 21, 81%), direct inoculation was mostly seen in immunocompetent patients.Eighty-two percent of patients (28 out of 34) received trimethoprim-sulfamethoxazole-containing regimens and median antibiotic treatment duration was 24 weeks (range, 12-120) for hematogenous infections and 12 weeks (range, 6-24) for direct inoculations. Outcome was favorable in 27 cases despite unsystematic surgical management (17 cases) without sequelae in 70% of the cases.Nocardia arthritis is rare but its management is complex and should rely on a combined approach with rheumatologist, infectious diseases expert, and surgeon.

Simultaneous determination of trimethoprim and sulfamethoxazole in dried plasma and urine spots

BACKGROUND

Trimethoprim-sulfamethoxazole (TMP-SMX) is an antimicrobial drug combination commonly prescribed in children and adults. The study objectives were to validate and apply an HPLC-MS/MS method to quantify TMP-SMX in dried plasma spots (DPS) and dried urine spots (DUS), and perform a comparability analysis with liquid matrices.

RESULTS

For TMP the validated range was 100-50,000 ng/ml for DPS and 500-250,000 ng/ml for DUS; for SMX, the validated range was 1000-500,000 ng/ml for both DPS and DUS. Good agreement was noted between DPS/DUS and liquid plasma and urine samples for TMP, while only modest agreement was observed for SMX in both matrices.

CONCLUSION

A precise, accurate and reproducible method was developed to quantify TMP-SMX in DPS and DUS samples.

Anti-alpha-toxin monoclonal antibody and antibiotic combination therapy improves disease outcome and accelerates healing in a Staphylococcus aureus dermonecrosis model

Alpha-toxin (AT) is a major virulence determinant in Staphylococcus aureus skin and soft tissue infection models. We previously demonstrated that prophylactic administration of 2A3, an AT-neutralizing monoclonal antibody (MAb), prevents S. aureus disease in a mouse dermonecrosis model by neutralizing AT-mediated tissue necrosis and immune evasion. In the present study, MEDI4893*, an affinity-optimized version of 2A3, was characterized for therapeutic activity in the dermonecrosis model as a single agent and in combination with two frontline antibiotics, vancomycin and linezolid. MEDI4893* postinfection therapy was found to exhibit a therapeutic treatment window similar to that for linezolid but longer than that for vancomycin. Additionally, when combined with either vancomycin or linezolid, MEDI4893* resulted in reduced tissue damage, increased neutrophil and macrophage infiltration and abscess formation, and accelerated healing relative to those with the antibiotic monotherapies. These data suggest that AT neutralization with a potent MAb holds promise for both prophylaxis and adjunctive therapy with antibiotics and may be a valuable addition to currently available options for the treatment of S. aureus skin and soft tissue infections.