Impetigo is a common superficial bacterial infection most often seen in children. There are two forms of impetigo non-bullous and bullous. The non-bullous form is the most common (70%) and generally affect children between two and five years, while those under the age of two are more affected by the bullous form.3

Fusidic acid acts by inhibition of bacterial protein synthesis by preventing translocation of the elongation factor G from the ribosome.

The non-bullous form presents with an erosion (sore), cluster of erosions, or small vesicles or pustules that have an adherent or oozing honey-yellow crust. The bullous form of impetigo presents as a large thin-walled bulla (2cm to 5cm) containing serous yellow fluid. It often ruptures leaving a complete or partially denuded area with a ring or arc of remaining bulla.2,3

Lesions can develop anywhere on the body but are most common on the face. It is a self-limiting, non-scarring condition, which usually resolves in two to three weeks without treatment.3

Complications are uncommon. However, untreated individuals remain infectious. To prevent outbreaks, children should not attend school or other childcare institutions until lesions are crusted and healed, or for 48 hours after commencing treatment. Good hygiene measures (eg washing hands regularly and using separate towels) help prevent spread of impetigo to other areas of the body and to other people.3

  • Folliculitis is caused by bacterial infection of the superficial or deep hair follicle. However, this condition may also be caused by fungal species, viruses and can even be non-infectious in nature. Several of the causative agents of folliculitis are listed below and include:4
  • Superficial bacterial folliculitis: the most common form of folliculitis, this particular condition is usually caused by the bacteria S. aureus. It should be noted that both the methicillin-sensitive and methicillin-resistant forms of this bacteria can cause folliculitis.
  • Gram-negative bacterial folliculitis: commonly referred to as ‘hot tub’ folliculitis, this condition results from the bacteria pseudomonas aeruginosa. It typically arises after exposure to contaminated water from either an improperly treated swimming pool or hot tub. Other bacteria that may cause this condition include Klebsiella and Enterobacter. Folliculitis from these bacteria commonly arises after long-term use of oral antibiotics.
  • Pityrosporum folliculitis: this particular form of folliculitis is fungal, caused by the Malassezia species of fungi such as Malassezia furfur. Typically found in adolescence secondary to increased activity of their sebaceous glands and is commonly found in a cape-like distribution over the patient’s shoulders, back, and neck. Clinical suspicion of this condition should arise in patients diagnosed with acne that has failed to respond or even worsened, after antibiotic treatment.
  • Viral folliculitis: most commonly caused by herpes virus it could also be caused by Molluscum contagiosum, but this is far rarer. Folliculitis due to herpes virus presents in much the same way as bacterial folliculitis with the exception that papulovesicles and/or plaques are usually present and not pustules. Another key to the diagnosis of this condition is that lesions typically appear in either groups or clusters.
  • Demodex folliculitis: a type of folliculitis caused by the mite Demodex folliculorum. this particular type of folliculitis is controversial as the Demodex mite normally presents in the pilonidal sebaceous area of the skin. Estimates are that 80% to 90% of all humans may carry this mite.
  • Eosinophilic folliculitis: this particular brand of folliculitis is found predominantly in those with advanced HIV or those with low CD4 counts. Although a non-HIV variation of this condition has been seen as a rare side effect in patients undergoing chemotherapy. While the exact aetiology of this condition is unknown, studies suggest it could result from inflammatory disease secondary to immune dysregulation and that there may be an associated underlying infection. Most commonly, this condition presents as erythematous and urticarial follicular papules, usually on the scalp, face, and neck with rare pustules.

Oral or topical antibiotics?

According to current recommendations, topical antibiotics are only recommended in cases of mild to moderate or superficial infections. Patients with severe disease who are systemically unwell will require assessment in hospital for monitoring and intravenous antibiotics.5

Fusidic acid and mupirocin are two of the most commonly used antibiotics for the treatment and eradication of skin infection. Topicals antibacterials are eminently suitable for targeted drug delivery by taking the drug directly to the site of action, thus ensuring excellent bioavailability of antimicrobials at the infected tissue. The other advantages of topical usage of antimicrobials are the small amounts of drugs used, low cost, and non-interference with intestinal microbial flora.1

Treating impetigo

Therapy depends on the extent and site of the lesions and on the presence of systemic symptoms. The practical clinical recommendations suggest topical antibiotic therapy for localised lesions and systemic therapy with oral antibiotics in cases of extensive injury, failure, or inability to perform topical therapy.5

Topical treatments are likely to cause fewer side effects, and applying a cream is usually straightforward for localised impetigo. Palatability and frequency of dosing of oral antibiotic liquids can be challenging in young children.3

In widespread non-bullous impetigo, clinicians should choose either a topical or oral antibiotic treatment after considering the distribution of the lesions and the wishes of the patient or parent/carer. Whether topical or oral treatment is used, a five-day course should be prescribed. This can be increased to seven days based on clinical judgement, depending on the severity and number of lesions.3

Fusidic acid is one of the most frequently prescribed topical agents for the treatment of impetigo. It acts against gram-positive bacteria such as Staphylococcus species and Corynebacterium species.1 The 2020 National Institute of Health Care and Excellence impetigo guidance recommends fusidic acid as first-line topical antibacterial treatment.6

Folliculitis

Without treatment, bacterial folliculitis may progress to hard and painful lumps filled with pus, known as boils. Various interventions have been suggested for treating folliculitis and boils, including local application of moist heat, phototherapy, antiseptic agents, antibiotics alone, or combination therapy.7

Local moist heat around 38°C to 40°C applied for 15 to 20 minutes may increase local blood flow, may establish drainage, and has proved helpful in the treatment of newly emerged folliculitis or boils.7

Topical antibiotics such as fusidic acid 2% cream twice daily may be used in treating folliculitis or boils when the number of lesions is limited, or they may be used in combination with other interventions. Systemic antibiotics may be used for treating folliculitis and boils, especially when systemic symptoms such as fever, lymphadenitis, or cellulitis appear.7

Recommended treatment include:8

  • Mild, superficial folliculitis may resolve without treatment
  • Consider treating nasal carriage of S. aureus with topical Fucidin® in those with recurrent folliculitis
  • Topical antiseptics such as triclosan, clorhexidine or povidone-iodine may be used to treat and prevent superficial folliculitis
  • For deeper folliculitis, topical or oral antibiotics are usually required
  • In severe or recurrent cases, antibiotic therapy may be required for four to six weeks
  • Other antibiotics may be used depending on culture results and the degree of clinical suspicion of alternative causative organisms – eg pseudomonal folliculitis responds to oral ciprofloxacin.
  • Gram-negative folliculitis can be treated for severe acne, with isotretinoin but the use of isotretinoin is associated with major side effects, including birth defects
  • Fungal infections are usually treated with topical azoles
  • Aciclovir or similar agents can be used to treat herpetic folliculitis.

Why fusidic acid is the first-choice option in the treatment of skin infections

Fusidic acid is an antibiotic derived from the fungus Fusidium coccineum. Fusidic acid acts by inhibition of bacterial protein synthesis by preventing translocation of the elongation factor G from the ribosome. Fusidic acid has a steroid-like structure without the unwanted side effects of steroid.1

Pharmacokinetic and pharmacodynamic studies have shown that, contrary to other topical antibiotics such as gentamicin or mupirocin, fusidic acid reaches high antimicrobial concentration at deep skin layers after topical application either on intact or damaged epidermis.9

Several randomised controlled trials demonstrated that fusidic acid, in its various topical formulations, is very effective in treating skin infections, given its high bactericidal activity against S. aureus (including strains resistant to penicillin, methicillin, ampicillin, cloxacillin), S. epidermidis, Streptococcus pyogenes, Propionibacterium acnes, Corinebatteria, Clostridia.9

Additionally, fusidic acid presents a low risk of resistance even in methicillin-resistant S. aureus strains, a common pathogen implied in the aetiology of skin infections.9

Studies using either fusidic acid cream or ointment have shown that there is fast and effective healing of skin infections. Studies in mainly primary skin infections, such as impetigo, abscesses/boils, folliculitis, and paronychia, and including a few cases of infected wounds and other secondary infections, have demonstrated response rates of between 86% and 100%, with treatment duration or mean healing time varying between four and 7.1 days.10

A study examining the clinical efficacy of topical fusidic acid ointment applied once daily compared with that of three oral antibiotics given for five days: 150mg clindamycin, 250mg flucloxacillin or 250mg of erythromycin four times daily plus placebo ointment. A total of 90 patients with skin infections including infected wounds, paronychia, and abscesses/boils, were included. The mean healing time in patients receiving oral antibiotics was grouped and compared with that in patients using the fusidic acid ointment. A significantly more rapid healing time in soft tissue infections was shown for fusidic acid ointment compared with the oral antibiotics (7.1 days vs. 9.7 days).10

A double-blind three-arm comparative study compared the effects of fusidic acid ointment plus placebo amoxicillin, placebo fusidic acid ointment plus amoxicillin, or fusidic acid ointment plus amoxicillin in 90 patients in the treatment of furuncles, carbuncles, impetigo, and infected wounds.10

Fusidic acid ointment was as effective as amoxicillin, and there was no further improvement in clinical outcomes when the treatments were used in combination. Fusidic acid ointment is as effective as mupirocin ointment but has superior patient acceptability.10

In a study involving 354 patients with primary or secondary skin infections, randomised participants to receive either mupirocin or fusidic acid three times daily for up to seven days. There was no difference between the two preparations in outcome in either primary or secondary infections.10

However, adverse events were reported in 1% of the fusidic acid ointment group, compared with 7.4% of those using mupirocin ointment. The greasy, messy, or sticky nature of mupirocin ointment accounted for the majority of complaints.10

Such a feature makes fusidic acid particularly useful in the management of these medical conditions. Finally, possibly due to its large steric effect, fusidic acid has proved a very low risk of contact sensitisation. Overall, data on fusidic acid efficacy, safety, sensitisation potential, resistance profile and spectrum selectivity make it a first-choice option in the treatment of primary and secondary skin infection.9

REFERENCES:
  1. Bandyopadhyay D. Topical Antibacterials in Dermatology. Indian J Dermatol, 2021.
  2. Stulberg DL, Pendrod MA and Blatn RA. Common Bacterial Skin Infections. American Family Physician, 2002.
  3. Ward C. Infective skin conditions: when is it appropriate to prescribe an antibiotic? Guidelines in Practice, 2020. https://www.guidelinesinpractice.co.uk/skin-and-wound-care/infective-skin-conditions-when-is-it-appropriate-to-prescribe-an-antibiotic/455426.article.
  4. Winters RD and Mitchell M. Folliculitis. StatPearls (Internet), 2020.
  5. Sukumaran V and Senanayake S. Bacterial skin and soft tissue infections. Australian Prescriber, 2016.
  6. NICE (2020). Impetigo: antimicrobial prescribing. https://www.nice.org.uk/guidance/ng153/resources/impetigo-antimicrobial-prescribing-pdf-66141838603717.
  7. Lin H-S, Lin P-T, Tsai Y-S, et al. Interventions for bacterial folliculitis and boils (furuncles and carbuncles). Cochrane Database Syst Rev, 2018.
  8. Knott L and Huins H. Folliculitis. https://patient.info/doctor/folliculitis-pro#nav-4
  9. Bonamonte D, Fortina AB, Neri L, Patrizi A. Fusidic acid in skin infections and infected atopic eczema. G Ital Dermatol Venereol, 2014.
  10. Long B. Fusidic acid in skin and soft-tissue infections. Acta Derm Venereol, 2008.