Bacterial Skin Infections
Bacterial skin infections are usually caused by Staphylococcus aureus, but a range of other bacteria can also infect the skin (Rajan 2012). The rising prevalence of antibiotic-resistant bacterial strains, including methicillin-resistant Staphylococcus aureus (MRSA), poses a serious treatment challenge (Hartman-Adams 2014; McClain 2016).
Impetigo is a skin infection that causes small pimple-like red sores, which may rupture and form a crust. The rash may itch, but scratching can spread the infection (NLM 2017a). Impetigo is usually caused byStaphylococcus aureus or, less commonly, Streptococcus pyogenes, or both (Stevens 2016). These bacteria are frequent colonizers of healthy skin but can cause infection in susceptible skin. Impetigo is often a complication of insect bites, allergic skin reactions, and other types of skin infections. Other conditions that increase susceptibility are skin trauma, hot and humid climate, poor hygiene, malnutrition, diabetes, and other health problems (Hartman-Adams 2014).
Because of impetigo’s contagious nature, hygienic practices including hand washing, regular bathing, avoiding contact with other infected people, and prompt cleaning of minor skin injuries are important for preventing the spread of infection (Hartman-Adams 2014).
Folliculitis, Furuncles, and Carbuncles
Folliculitis is a superficial infection of the hair follicles, usually caused by Staphylococcus aureus. If the infection spreads to the tissue surrounding the hair follicle, it forms a pocket known as a furuncle, or a boil. A carbuncle is formed when these pockets of infection coalesce into a larger connected area of infection. Regular applications of warm compresses may promote drainage of furuncles, but larger and deeper infections may require incision and drainage (Cevasco 2010; Rajan 2012).
Erysipelas and Cellulitis
Erysipelas is an infection that involves the superficial skin layer and lymph vessels, while cellulitis involves rapidly-spreading infection and inflammation of the skin and subcutaneous tissues. These infections are usually caused by Streptococcus pyogenes or Staphylococcus aureus and can be complications of traumatic injuries, burns, surgery, injection drug use, and other skin diseases and infections (Stevens 2016; Badour 2017).
Conventional Treatment of Bacterial Skin Infections
The global emergence of antibiotic-resistant bacteria over the last two decades makes the treatment of bacterial skin infections ever more difficult, and strategies to reduce antibiotic use in dermatology are needed (Colsky 1998; Chon 2012; Bangert 2012). Nevertheless, the mainstays of conventional treatment for bacterial skin infections are topical and oral antibiotics. Intravenous antibiotics may be necessary to control severe spreading infections (Cevasco 2010; Rajan 2012).
Newer antibiotic agents with low levels of known resistance and efficacy against MRSA and other treatment-resistant strains are currently being developed and tested; however, the expense of these new medications can be a deterrent (McClain 2016).
Integrative Treatment of Bacterial Skin Infections
Of all tissues in the body, the skin has the third-highest abundance of zinc (Ogawa 2016). Zinc is useful in an array of infectious skin disorders due to its important roles in immune activity and wound healing (Gupta 2014). Chronic zinc deficiency is associated with increased susceptibility to skin infections (Bae 2010; Gupta 2014; Livingstone 2015).
In laboratory studies, zinc has demonstrated antibacterial activity against Staphylococcus aureus and Streptococcus pyogenes, the major causes of impetigo, erysipelas, and folliculitis (Chen 2016; Ong 2014; Ong 2015). Newer topical zinc oxide preparations using nanoparticle technologies have shown potential in combatting Staphylococcus aureus, including MRSA (Ansari 2012; Mohandas 2015; Pati 2014; Dizaj 2014). The use of nanoparticle-based systems in dermatology has emerged in recent years as a growing research area and a promising therapeutic approach (Desmet 2017; DeLouise 2012). Nanoparticle use in dermatology faces many unanswered questions and therapeutic challenges, including toxicological and environmental safety considerations, which need to be addressed in future, much-needed studies (DeLouise 2012; Papakostas 2011).
Vitamin D is an important factor in skin barrier function (Piotrowska 2016). Vitamin D is involved in the production of antimicrobial peptides in the skin that help protect against cutaneous infections (Muehleisen 2012). Subjects with MRSA infections were found in one study to have lower vitamin D levels than subjects without MRSA infections (Thomason 2015). Several studies have noted a relationship between low vitamin D levels and nasal colonization with Staphylococcus aureus, including MRSA, which increases the risk of skin and soft tissue infections (Matheson 2010; Olsen 2012; Singh, Johnson 2016). In a controlled clinical trial, a reduction in nasal Staphylococcus aureus colonization was seen in 24 participants with atopic dermatitis who were treated with 2000 IU per day of oral vitamin D, potentially reducing their risk of secondary bacterial skin infections (Udompataikul 2015).
Garlic’s (Allium sativum) broad antimicrobial properties give it a potential role in skin infection prevention and treatment. In one laboratory study, allicin (an active constituent of garlic) was effective at clearing all tested strains of MRSA, including those that were resistant to the antibiotic mupirocin (Bactroban), which is used to treat MRSA (Cutler 2004). In another laboratory study, garlic oil was found to inhibit immune-evading strategies by bacteria that frequently cause infections in burn patients (Nidadavolu 2012). In one small clinical trial, supplemental garlic extract increased circulation in the small blood vessels of the skin in ten healthy volunteers (Wohlrab 2000). Although this study did not examine effects on immune parameters or infection risk, better circulation in the skin may enhance the ability of immune cells to reach sites of infection to combat pathogens.
Given the increasing presence of treatment-resistant infectious microbes, evidence supporting the role of probiotics in preventing and treating skin infections is especially welcome (Wong 2013; Hafez 2013). Several probiotic bacteria have been shown to inhibit the growth of Staphylococcus aureus strains, including MRSA (Hafez 2013; Sikorska 2013). The subcutaneous injection of Lactobacillus plantarum prevented infections and promoted healing in burn wounds in laboratory mice (Valdez 2005), and its local application on the burn wound was beneficial in a clinical study of human burn patients (Peral 2009). Another probiotic strain, Lactobacillus reuteri, protected skin cells from the harmful effects of Staphylococcus aureus in a laboratory study (Prince 2012). Intriguing new research has highlighted the potential role of probiotics in the gut to promote skin immunity through the interconnectivity of the gut and skin immune systems. Immune cells in the gut called dendritic cells can modulate the systemic immune response to food-based antigens, which may influence skin issues related to food sensitivities or allergies (Friedrich 2017). More research in this area is needed to determine which probiotics may benefit skin conditions.
Honey’s broad antimicrobial and wound-healing actions are well established. It has been used historically as a topical treatment for non-healing wounds and ulcers, boils, and various skin infections, and its benefits have been attributed to its acidity, hydrogen peroxide content, nutrient and antioxidant content, and immune-modulating activity (Al-Waili 2011). Honey collected from different parts of the world has demonstrated antibacterial actions against both hospital-acquired and community-acquired MRSA cultures (Maeda 2008). In laboratory studies, New Zealand manuka honey worked synergistically with antibiotics to clear certain strains of Staphylococcus aureus, including MRSA (Liu 2014; Muller 2013). In a clinical trial, children with bacterial abscesses related to a condition called pyomyositis were treated with surgery and oral antibiotics; following surgery, their wounds were packed with gauze soaked with either honey or a commonly used antiseptic. Those treated with honey had faster wound-healing and shorter hospital stays (Okeniyi 2005). In a case report, topical honey effectively cleared a MRSA skin infection in an immunosuppressed patient (Natarajan 2001).
Topical Essential Oils
Essential oils have well known antimicrobial properties. Tea tree oil, the essential oil of Melaleuca alternifolia, has demonstrated antibacterial effects in laboratory research against bacteria involved in skin conditions, such as Streptococcus pyogenes (Tsao 2010), Staphylococcus aureus, and MRSA (Loughlin 2008; Halcon 2004; Brady 2006). In a clinical trial involving 224 hospitalized patients, a regimen using tea tree oil, as a 10% cream and 5% body wash, was more effective than a standard antibiotic regimen for clearing MRSA from the skin (Dryden 2004). Of note, tea tree oil may cause an allergenic reaction in some people, so should be used judiciously by those who have not used it before (Christoffers 2014). If you suspect you are prone to react to tea tree oil, your dermatologist may be able to perform a skin patch test for confirmation (Rutherford 2007). Other essential oils exhibiting antibacterial effects against skin-relevant bacteria include orange and coriander oils (Casetti 2012; Muthaiyan 2012).
Vitamin C plays an important role in the synthesis of collagen (a structural protein found in skin and other connective tissues) and skin healing (Moores 2013; Telang 2013). It has shown antibacterial activity against Staphylococcus aureus (Kallio 2012), and a study that enrolled human participants with recurrent furuncles and decreased neutrophil function found that taking 1 gram oral vitamin C daily for 4‒6 weeks significantly improved the function of the participants’ neutrophils (Levy 1996).
Tea (Camellia sinensis) leaves are a source of polyphenolic compounds, including catechins, which have anti-microbial and immune-stimulating properties (Rosen 2012). A laboratory study showed that green tea extract and epigallocatechin gallate (EGCG), a primary active constituent of green tea, inhibited the growth of multidrug-resistant bacteria that can infect the skin. The researchers concluded that green tea extract and EGCG may have potential as adjunct topical antimicrobial treatments for skin infections caused by drug-resistant bacteria (Jeon 2014). In a controlled trial, a topical lotion made with black tea extract was comparable to antibiotics in treating impetigo (Sharquie 2000).