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Introduction Primary bacterial skin infections are sometimes viewed as mere nuisance conditions relative to other graver infectious diseases. However, recognition of these infections is important given their high prevalence, particularly in low-income contexts, and because most can be resolved with appropriate treatment, to the significant benefit Dr Francois de Goede of personal and public health.¹ Bacterial skin infections are classified according to Dermatologist the extent to which the penetrates into the subcutaneous tissue, and Panorama Medical Centre, whether associated structures such as hair follicles and lymphatics are affected.² Cape Town They are broadly grouped into skin and soft tissue infections, and acute bacterial skin and skin structure infections. This article focuses on three of the most common and relatively superficial of the former: , and the minor skin known as furuncles and .

KEY MESSAGES

• Recognition of primary bacterial skin infections is important given their high prevalence and mostly good response to treatment High prevalence and moderate morbidity • Impetigo, folliculitis, furuncles and carbuncles are among the most common skin infections of primary bacterial seen in clinical practice infections warrants • aureus and pyogenes are the main causative agents their being made a public health • Primary infections are generally mild and treated with topical ; more severe cases require oral antibiotics priority • Carbuncles and larger furuncles usually require

• Bacterial culture swabs should be done for persistent or recurrent infections

• Management of bacterial skin infections has become more challenging because of growing resistance

• The high prevalence and moderate morbidity of primary bacterial infections warrants their being made a public health priority.

Recognising impetigo Impetigo is a contagious, superficial skin caused, for example, by cuts, abra- infection caused primarily by Staphylococcus sions, or sores, are aureus or . It does vulnerable to secondary infection.³ This article was made possible not extend beyond the , and the Impetigo is classically divided into two by an unrestricted educational associated lesions do not form ulcers or types: nonbullous and bullous. grant from Adcock Ingram, which had no control over leave when they heal.² Nonbullous impetigo accounts for content. Primary infection can take hold via around 70% of cases, and is more conta- direct invasion of normal unbroken skin, gious than the bullous form.4 It is usually or when the integrity of the skin’s natu- caused by S aureus, but sometimes by S ral defence barrier is breached. Existing pyogenes or by both agents together.² It

Adcock Ingram Derm.indd 1 2018/01/29 3:55 PM SEPTEMBER 2019 I 1 Primary bacterial skin infections

tends to affect exposed areas such as the exfoliative toxin associated with certain face, hands and feet. The initial lesions strains of S aureus. may are small clusters of vesicles or pustules. sometimes also affect the oral mucosa, When these rupture, the discharged and in infants extensive lesions may be forms a -yellow crust that adheres accompanied by systemic symptoms such to the ’s moist, erythematous base. as and diarrhoea. Bullous impetigo Mild regional enlargement of the lymph is more likely to cause pain or discomfort nodes may be present. Nonbullous impe- than nonbullous impetigo.4 tigo is generally self-limiting and can be is a form of impetigo in which expected to resolve in around two weeks.4 infection penetrates into the , caus- Bullous impetigo, caused by S aureus ing necrotic shallow ulcers with thick, alone, is considered to be less conta- brown-black crusts that appear ‘punched Impetigo is the most gious than nonbullous impetigo. It most out’ when crusted or purulent matter is common childhood frequently affects the face, hands, feet, removed. It occurs most commonly on : it is armpits, torso or perianal area. Lesions the lower limbs in debilitated or elderly estimated that over typically are thin-walled, transparent ves- patients.² 162 million children icles that increase rapidly in size to form Patients with impetigo may complain large , or bullae, containing a clear of itchiness and should be advised against in the world have yellow fluid that becomes darker and touching or scratching the lesions as this the condition at any cloudy. When a lesion ruptures it devel- can spread the infection. one time ops a brown, varnish-like crust due to an Ph.wittaya.Shutterstock. https://en.wikipedia.org/wiki/Bullous_impetigo

Nonbullous impetigo Bullous imeptigo after rupture of bullae

Impetigo prevalence, risk factors and social impact

Impetigo is the most common childhood through systemic conditions (e.g. HIV skin infection: it is estimated that over infection, , or hepatitis), 162 million children in the world have or who are receiving immunosuppressant the condition at any one time − predomi- treatment, are also more vulnerable to nantly in low- and low- to middle-income bacterial infection.¹ countries and in underprivileged commu- Impetigo and folliculitis tend to recur nities within high-income countries. The and persist in patients with HIV dis- EARN FREE peak incidence is seen in children between ease, especially in children. HIV-positive CPD POINTS two and five years old, with a drop-off as patients have increased rates of S aureus age increases. A systematic review of the colonisation, and in cases of advanced Join our CPD community at global epidemiology of impetigo found HIV/AIDS it is not uncommon for this to the median prevalence to be 12.3% in chil- lead to and deep tissue infection.6 www.denovomedica.com dren and 4.9% in adults.5 Despite the high prevalence of impetigo Risk factors include hot, humid cli- and other primary infections, these often and start to earn today! mates; lower socioeconomic status; poor go under-recognised, especially in the hygiene; household overcrowding; and developing world, and the associated bur- chronic staphylococcal or streptococcal den of disease is frequently under-appre- infection of the upper respiratory tract.5 ciated. In resource-poor communities Patients who are elderly or debilitated impetigo has a significant negative impact

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on well-being, and represents a high cost dermatological condition with potential to families in terms of treatment expenses lifelong consequences if left untreated. and missed school days. Especially when Given its high prevalence and moderate impetigo occurs as a secondary infec- morbidity, impetigo (as well as the other tion in conjunction with scabies lesions, primary skin infections) deserves more it is considered to be a major childhood attention as a public health priority.5

Treatment of impetigo Diagnosis of impetigo is usually based second-line options. With , on patient history and recognition of the irritation at the application site is the characteristic lesions. Only in cases of most common adverse effect. persistent or recurrent impetigo is it nec- contains polyethylene glycol which is essary to have cultures done of the lesions potentially nephrotoxic when absorbed (to identify methicillin-resistant S aureus, from broken skin; caution is therefore or MRSA) and the nose (to identify a advised when using it in patients with causative nasopharyngeal reservoir of S renal impairment.² aureus).4 Systemic antibiotics are appropriate Mild, localised impetigo is typically for more severe or widespread impetigo treated with a topical antibiotic (Table infection, and for ecthyma. First-line oral 1). To increase the ’s efficacy, antibiotics include , erythro- before applying it to the affected areas mycin or clarithromycin. Flucloxacillin these may be soaked and carefully washed is a semi-synthetic penicillin that is well with soap and water to remove crusted absorbed; the main potential side-effects material.² are gastrointestinal (nausea, vomit- While MRSA usually Impetigo responds well to , ing and diarrhoea) and dermatological the recommended first-line topical anti- hypersensitivity reactions such as . causes mild skin biotic for this infection. Fusidic acid is belongs to the macrolide infections, these applied as a 2% cream 3-4 times daily until class of antibiotics that is unrelated to can become more the lesions resolve, which can be expected penicillins, making it suitable for use severe, and it may in around seven days. It is active against in patients who have penicillin allergy. infect other parts of most Gram-positive , especially Common side-effects may include nau- Staphylococcus species, and has no sig- sea, vomiting and diarrhoea, and skin the body such as the nificant side-effects; hypersensitivity reac- reactions such as rash and urticaria. lungs, urinary tract tions may occur in rare cases.² Clarithromycin has a similar action to or bloodstream Retapamulin and mupirocin are erythromycin but may be better tolerated.²

MRSA as a cause of impetigo and other primary skin infections

MRSA, which can be hospital or com- only and their use should not exceed 10 munity acquired, has become increasingly days.8 common as a cause of impetigo, in par- Initial empirical therapy for MRSA is ticular the nonbullous form. It may also not recommended unless there is sound be implicated in folliculitis and related clinical evidence as motivation (e.g. con- skin abscesses. tact with another documented case or While MRSA usually causes mild exposure to a documented outbreak). skin infections, these can become more While antibacterials such as , severe, and it may infect other parts of the trimethoprim/sulfamethoxazole and dox- body such as the lungs, urinary tract or ycycline are effective against most strains bloodstream.7 of community-associated MRSA, treat- Given that the emergence of resistant ment regimens will be determined by local S aureus has been reported following pro- patterns of MRSA prevalence and resist- longed use of topical antibiotics for skin ance, and should be informed by culture conditions, it is recommended that these and sensitivity test results.8 are reserved for mild, localised infections

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Recognising folliculitis

Bacterial folliculitis is a primary skin Folliculitis is usually caused by S aureus, infection that causes of but is occasionally linked to other organ- the hair follicles. It presents as superficial isms such as , pustules or nodules surrounding the fol- which is associated with inadequately licle, typically on areas of moist, hairy treated water in spas or jacuzzis. Lesions skin, such as the beard region, armpits from this type of ‘hot tub’ folliculitis are or buttocks. Infected hairs can easily fall most likely to be found on the torso.² out or be removed, but new pustules often Perspiration, trauma, friction and develop. The condition tends to cause occlusion of the skin may all render it mild pain or irritation and itching. more susceptible to developing folliculitis.9 David Pereiras.Shutterstock.

Folliculitis Prevalence of folliculitis There are no reliable figures for com- practice. Superficial folliculitis occurs in munity prevalence of folliculitis, or the both sexes and all races. It tends to occur related condition of furunculosis, but more often in adults, probably because both are well recognised nonetheless as there is more terminal hair growth than being commonly encountered in clinical in children.

Treatment of folliculitis Folliculitis is usually diagnosed through In recalcitrant or recurrent cases of fol- EARN FREE clinical examination; microbiological test- liculitis, the pustules are cultured to test CPD POINTS ing is not routinely done.9 Clindamycin or for resistant strains of S aureus, and a a benzoyl peroxide wash may be helpful for nasal culture is done to check for the pres- Join our CPD community at superficial folliculitis, but stubborn cases ence of chronic nasal infection.9 will probably require a topical antibiotic ‘Hot tub’ folliculitis caused by P aer- www.denovomedica.com such as fusidic acid cream (Table 1).² uginosa generally resolves spontaneously As with impetigo, widespread or severe without treatment, but proper chlorina- and start to earn today! cases of folliculitis usually require sys- tion of the source water must be ensured temic therapy with an oral antibacterial to avoid recurrences and new cases of such as flucloxacillin. Erythromycin or infection.9 clarithromycin are options where patients are allergic to penicillin.²

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Recognising furuncles and carbuncles

Furuncles and carbuncles are types of follicles. Carbuncles tend to form on the skin abscesses that may develop from back, thighs or nape of the neck, and may superficial folliculitis if infection pen- be accompanied by systemic symptoms etrates deeper down towards the subcuta- such as fever and .² neous tissue. Furuncles and carbuncles may affect A furuncle, or , involves the base of healthy young people but tend to occur the and some surrounding tis- more often in patients who are obese, sue. It is a firm, tender, inflamed immunocompromised or elderly, or who that usually ruptures spontaneously to have diabetes or are otherwise debilitated. discharge bloody pus and necrotic tissue. Other predisposing factors include hot, Furuncles are more likely to occur on the humid climates; skin or nasal bacterial face, neck, buttocks, armpits and breasts. colonisation; occlusion of the skin (e.g. They cause discomfort and may even be by treatments such as topical corticos- painful.² teroids for other dermatological condi- A is the term for a cluster tions) and abnormal follicular anatomy of adjacent furuncles that have merged. such as comedones. Clusters of cases Abscesses (relatively smaller and more may be reported in the community where superficial than subcutaneous abscesses) people are living in unhygienic, crowded may form within the carbuncle, discharg- conditions, or among close contacts of an ing pus to the skin surface along hair infected patient.9 Mariyana M.Shutterstock. Andriano.cz.Shutterstock.

Furuncle Carbuncle Treatment of furuncles and carbuncles Furuncles and smaller carbuncles often Furuncles and carbuncles that persist drain spontaneously or when drainage is or recur despite prophylactic antibiotic facilitated by the application of a warm therapy may be caused by S aureus strains compress. In cases where there is a single that produce Panton-Valentine leukoci- small lesion under 5mm in diameter, anti- din (PVL) toxin. PVL-associated S aureus biotics are not deemed necessary.9 may be sensitive or resistant to methicillin Larger nodules must usually be incised or flucloxacillin. In such cases, cultures to allow for drainage and any dead tis- should be done, and an infectious dis- sue should be surgically removed. Often ease specialist consulted as to appropriate an oral antibiotic such as flucloxacillin is ongoing management of the infection.² also required. Erythromycin as a first-line Recurrence of furuncles can be avoided option and clarithromycin as a second- by washing the skin with liquid soap con- line option are suitable for use in patients taining chlorhexidine gluconate with iso- with penicillin allergy. propyl alcohol or 2-3% chloroxylenol,

SEPTEMBER 2019 I 5 Primary bacterial skin infections

This CPD-accredited report was and by prescribing maintenance antibi- receive treatment for any predisposing compiled by Olivia Rose-Innes on otics over 1-2 months. Patients who are factors such as obesity, nasal carriage of behalf of deNovo Medica. prone to developing furuncles should also S aureus or MRSA colonisation.9

Table 1.Treatment regimen for impetigo, folliculitis, furuncles and carbuncles2

Infection Bacterium Severity Treatment

Nonbullous S aureus alone Mild cases Topical antibiotic impetigo S pyogenes alone 1st line: fusidic acid 2% cream 3-4x Both S aureus and daily up to 10 days S pyogenes 2nd line: retapamulin 2x daily for 5 days or mupirocin 3x daily for 7 days

Bullous S aureus Severe cases Oral antibiotic: impetigo Flucloxacillin 500mg every 6 hours, or Erythromycin 250-500mg every 6 hrs, or Clarithromycin 250-500mg every 12 hrs

Folliculitis S aureus Mild cases Topical antibiotic: Clindamycin 1% lotion 7-10 days, or EARN FREE Benzoyl peroxide 5% wash 5-7 days CPD POINTS Recalcitrant cases Fusidic acid

Are you a member of Severe cases Oral antibiotic: Flucloxacillin 500mg every 6 hours, or Southern Africa’s leading Erythromycin 250-500mg every 6 hrs, or digital Continuing Clarithromycin 250-500mg every 12 hrs Professional Development Furuncles and S aureus Mild cases (lesion <5mm) No treatment needed website earning FREE CPD carbuncles points with access Severe cases (lesion >5mm) Incision and drainage plus oral antibiotic: to best practice content? Flucloxacillin 500mg every 6 hours, or Erythromycin 250-500mg every 6 hrs, or Only a few clicks and you can Clarithromycin 250-500mg every 12 hrs register to start earning today

Visit References www.denovomedica.com Click on reference to access the scientific article 1. Hay R, Bendeck S, Chen S, et al. Skin diseases. In: 5. Bowen A, Mahé A, Hay R, et al. The global epidemiology For all Southern African Disease Control Priorities in Developing Countries. of impetigo: a systematic review of the population healthcare professionals 2nd edition. New York: The World Bank and Oxford prevalence of impetigo and . PLoS ONE 2015; University Press, 2006. 10(8): e0136789. 2. Ni Riain U. Recommended management of common 6. Schwartz R. Cutaneous manifestations of HIV, 2018. bacterial skin infections. Prescriber 2013; 24(23-24): 7. Moran G, Amii R, Abrahamian F, et al. Methicillin- 15-25. resistant in community-acquired 3. Moulin F, Quinet B, Raymond J, et al. Managing children skin infections. Emerg Infect Dis 2005; 11(6): 928-930. skin and soft tissue infections. Arch Pediatr 2008; 15(2): 8. Public Health England. Management of infections: S62-S67. guidance for primary care. November 2012. Find us at 4. Cole C, Gazewood J. Diagnosis and treatment of 9. Damian Dhar A. Overview of bacterial skin infections, impetigo. Am Fam Physician 2007; 75(6): 859-864. DeNovo Medica 2017.

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