What Is New in the Management of Skin and Soft Tissue Infections in 2016?

Garyphallia Poulakou; Efthymia Giannitsioti; Sotirios Tsiodras

Disclosures

Curr Opin Infect Dis. 2017;30(2):158-171. 

In This Article

Classification and Epidemiology

There are several classification approaches of SSTIs in the literature, with none of them being universally adopted. Two comprehensive definitions proposed by the Infectious Diseases Society of America, namely uSSTIs and complicated SSTIs (cSSTIs) and based on the extent of the infection and the need for surgical intervention, are shown in Table 1.[7,9,10] A breakthrough in the regulatory procedures of new antibacterials for SSTIs has been accomplished with the introduction of the definition of Acute Bacterial Skin and Soft Structure Infection (ABSSSI) by the Food and Drug Administration in 2013.[10] ABSSSI is defined as a bacterial infection of the skin with a lesion size area of at least 75 cm2, with variable clinical presentations presented in Table 1. In addition, a new primary endpoint was introduced, referred to as early assessment of clinical response: at least 20% reduction in lesion size at 48–72 h compared with baseline. The traditional response at test of cure (7th–10th day) was then proposed as secondary endpoint.[10]

An important contemporary study from United States explored incidence of SSTIs between 2005 and 2010, using ambulatory and inpatient data of more than 48 million persons-years aged 0–64 years from the HealthCore Integrated Research Database. SSTI incidence, with peak at the age of 45–64 years, was approximately 4.8 SSTIs per 100 person years and remained stable through the observed period, being, however, almost two-fold of that of urinary tract infections and 10-fold of that of pneumonia. Most SSTIs (95%) were treated in the ambulatory setting, the majority (57.3%) being classified as abscesses or cellulitis, with complications rates (i.e. sepsis, bacteremia, osteomyelitis, myositis and gangrene) of 0.93 and 16.92% for ambulatory and hospitalized patients, respectively.[11] Therefore, the increasing trends in the incidence of SSTIs observed in the onset of the new millennium,[2–4] mainly driven by the emergence of CA-MRSA seem to have reached a plateau, at least in United States.

In Europe, data from the European Centre for Disease Prevention and Control estimated that 4% of all healthcare-acquired infections (HAIs) reported between 2011 and 2012 were SSTIs, with surgical-site infections being the second most frequently reported HAI (19.6%).[12] Incidence of MRSA infections in Europe shows significant country variation ranging from 0.9% (Netherlands) to 56.0% (Romania). An overall decreasing trend has been recorded, with population-weighted mean percentage for MRSA declining from 18.6% in 2011 to 17.4% in 2014.[13] An important epidemiologic study highlighted the differences between European and US CA-MRSA epidemiology, indicating highly diverse distribution of Methicillin-sensitive Staphylococcus aureus (MSSA) and MRSA clones with no predominant circulating clone, no archetypical USA300 CA-MRSA clone and Panton–Valentine Leucocidine production in 24.9% of isolates.[14]

The most frequently isolated gram-positive pathogens in SSTIs are S. aureus (including MRSA), followed by β-hemolytic streptococci; other streptococci, enterococci and gram-negative bacteria may also be involved.[10,15,16] Depending on the clinical setting, polymicrobial infections may be encountered (Table 2).[1,9,16] An outbreak of type emm59 invasive group A Streptococcus (iGAS) disease was recognized in 2008 in Northwestern Ontario, Canada; illicit drug use, alcohol abuse, homelessness and hepatitis C infection were elucidated as predisposing conditions.[17] Mycobacteria although rare should be considered in certain epidemiological scenarios; Mycobacterium abscessus is being increasingly reported after aesthetic surgery particularly in the context of medical tourism, whereas Mycobacterium marinum can infect fish market workers.[18,19] International travel has been recognized as an important factor for severe MRSA SSTI; imported MDR S. aureus had 1; 10 probability of inadequate initial treatment. A recent study highlights the considerations posed by cross-border transmission in returnees and the need for management algorithms to increase likelihood of appropriate empirical treatment.[20]

HIV infection, was shown as a strong predisposion for relapsing SSTIs in one-third of patients within 1 year in a recent cohort study; specific risk factors of this population included nonhepatitis liver disease, intravenous catheter presence, a history of Intravenous drug use (IVDU) and non-African-American race, but not low CD4+ cell count.[21] Furthermore, opioid-related SSTI in United States increased two-fold from 4 to 9 per 100,000 between 1993 and 2010, mostly affecting ages between 20 and 40 years and in parallel with yearly increase in price-per-gram-pure heroin.[22]

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