[Systemic therapy with antibiotics. Overview of important antibiotics in dermatology]

Calculated initial parenteral treatment of bacterial infections: Skin and soft tissue infections

This is the ninth chapter of the guideline "Calculated Parenteral Initial Therapy of Adult Bacterial Disorders - Update 2018" in the 2nd updated version. The German guideline by the Paul-Ehrlich-Gesellschaft für Chemotherapie e.V. (PEG) has been translated to address an international audience. The chapter contains the first German S2k guidelines for bacterial skin and soft tissue infections. They encompass recommendations on diagnosis and treatment of the defined entities erysipelas (caused by beta-hämolytic streptococci), limited superficial cellulitis (S. aureus), severe cellulitis, abscess, complicated skin and soft tissue infections, infections of feet in diabetic patients ("diabetic foot"), necrotizing soft tissue infection and bite injuries.

S2k guidelines for skin and soft tissue infections Excerpts from the S2k guidelines for "calculated initial parenteral treatment of bacterial infections in adults - update 2018"

These first German S2k guidelines for bacterial skin and soft tissue infections were developed as one chapter of the recommendations for "calculated initial parenteral treatment of bacterial infections" issued under the auspices of the Paul-Ehrlich Society, of which the main part is presented here. Well-calculated antibiotic therapies require precise diagnostic criteria. Erysipelas is defined as non-purulent infection considered to be caused by beta-hemolytic strepto-cocci. It is diagnosed clinically by its bright-red erythema and early fever or chills at disease onset. Penicillin is the treatment of choice. Limited soft tissue infection (cellulitis) is usually caused by Staphylococcus (S.) aureus, frequently originates from chronic wounds and presents with a more violaceous-red hue and only rarely with initial fever or chills. Treatment consists of first- or second--generation cephalosporins or flucloxacillin (IV). Severe cellulitis is a purulent, partially necrotic infection which extends through tissue boundaries to fascias and requires surgical management in addition to antibiotics. Moreover, it frequently fulfills the criteria for "complicated soft tissue infections", as previously defined by the Food and Drug Administration for use in clinical trials (they include comorbidities such as uncontrolled diabetes, peripheral artery disease, neutropenia). It requires antibiotics which besides S. aureus target anaerobic and/or gramnegative bacteria. The rare so-called necrotizing skin and soft tissue infections represent a distinct entity. They are characterized by rapid, life-threatening progression due to special bacterial toxins that cause ischemic necrosis and shock and need rapid and thorough debridement in addition to appropriate antibiotics. For cutaneous abscesses the first-line treatment is adequate drainage. Additional antibiotic therapy is required only under certain circumstances (e.g., involvement of the face, hands, or anogenital region, or if drainage is somehow complicated). The present guidelines also contain consensus-based recommendations for higher doses of antibiotics than those approved or usually given in clinical trials. The goal is to deliver rational antibiotic treatment that is both effective and well-tolerated and that exerts no unnecessary selection pressure in terms of multidrug resistance.

Frequent bacterial skin and soft tissue infections: diagnostic signs and treatment

Skin and soft tissue infections rank among the most frequent infections worldwide. Classic erysipelas is defined as a non-purulent infection by beta-hemolytic streptococci. The typical signs are tender, warm, bright erythema with tongue-like extensions and early systemic symptoms such as fever or at least chills. Erysipelas always and best responds to penicillin. Limited soft tissue infection or limited cellulitis are the terms we have introduced for infections frequently caused by S. aureus and often originating from chronic wounds or acute trauma. Clinically, they are marked by tender, erythematous swelling which, unlike erysipelas, exhibit a darker red hue and is not always accompanied by fever or chills at onset. Severe cellulitis is a purulent, partially necrotic infection extending to the fascia, with general symptoms of infection, requiring surgical management in addition to antibiotics. It often fulfils criteria of so-called complicated soft tissue infections according to the definition of the FDA, due to their frequent association with e.g. severe diabetes mellitus, peripheral arterial occlusive disease or severe immunosuppression. In contrast, the rare necrotizing skin and soft tissue infections represent a distinct entity, characterized by rapid progression to ischemic necroses and shock due to special bacterial toxins. Limited cellulitis should be treated with cephalosporins group 1 or 2, or, when S.aureus is the isolated or highly likely causative agent, isoxazolyl-penicillins (exploiting their minimal selection pressure on other bacteria). For severe cellulitis, initial antibiotic treatment (mostly iv) includes - depending on the location - agents also active against gram-negative and/or anaerobic bacteria. (e.g. clindamycine, aminopeniclilline with inhibitors of betalaktamase, fluochinolons, cephalosporines group 4). For cutaneous abscesses, drainage presents the therapy of choice. Only under certain conditions additional antibiotic therapy is required. Adherence to the diagnostic criteria and to evidence-based or consensus-derived treatment recommendations as presented herein should allow for an antibiotic therapy with a good balance of efficacy, tolerability by patients and low selection pressure for highly resistant bacteria.

Diverse virulent pneumophages infect Streptococcus mitis

Streptococcus mitis has emerged as one of the leading causes of bacterial endocarditis and is related to Streptococcus pneumoniae. Antibiotic resistance has also increased among strains of S. mitis and S. pneumoniae. Phages are being reinvestigated as alternatives to antibiotics for managing infections. In this study, the two virulent phages Cp-1 (Podoviridae) and Dp-1 (Siphoviridae), previously isolated from S. pneumoniae, were found to also infect S. mitis. Microbiological assays showed that both pneumophages could not only replicate in S. mitis but also produced more visible plaques on this host. However, the burst size and phage adsorption data were lower in S. mitis as compared to S. pneumoniae. A comparison of the genomes of each phage grown on both hosts produced identical nucleotide sequences, confirming that the same phages infect both bacterial species. We also discovered that the genomic sequence of podophage Cp-1 of the Félix d'Hérelle collection is different than the previously reported sequence and thus renamed SOCP.