Introduction

Definition of impetigo

Impetigo is a highly contagious bacterial infection of the superficial layer of the skin. It is characterised by the formation of blisters, which leave a golden-brown crust after bursting.¹

It is most common amongst young children, and usually responds well to treatment with hydrogen peroxide cream or antibiotics (fusidic acid or mupirocin topically) or flucloxacillin (clarithromycin or erythromycin orally).^2,3

Overview of impetigo complications 

Complications are rare with impetigo as it usually responds well to treatment and clears out within a week, however, complications may still arise due to absence or failure of treatment.

These complications include the spread of the infection to healthy skin or the occurrence of secondary infections in other areas of the body, such as the deep layers of skin, lymph nodes, or the bloodstream.¹

Understanding impetigo complications 

Impetigo is caused by bacteria that exist on healthy human skin. It results from infection caused by either Staphylococcus aureus or Streptococcus pyogenes (group A streptococcus).⁴

Spread of infection

Skin infections

Impetigo is a contagious condition and is transmitted through direct contact. This can also be in the form of autoinoculation, where the person would spread the infection to healthy skin through contact or scratching of the sores. These new infections can appear around the initial affected area or in other parts of the skin.⁵

Lymph node infections

Bacteria may penetrate from the skin into the lymphatic vessels and trigger an immune response leading to the infection of lymph nodes. Depending on where the impetigo lesions are on the body, the lymph nodes closest to this location will appear red and swollen as a result of inflammation. This may be accompanied by fever, tiredness and nausea or vomiting.

Secondary infections

Cellulitis

Cellulitis occurs when the deep layers of the skin become infected. It usually arises after the integrity of the skin has been compromised and is followed by entry of bacteria. The species implicated in impetigo are common causative agents for cellulitis.⁶

Ecthyma 

This is a serious form of impetigo, commonly observed on the legs and buttocks of young children. It is sometimes referred to as deep impetigo.⁷

In ecthyma, the lesions occur deeper into the skin and progress into well-defined black ulcers, subject to scarring after healing.⁸

Osteomyelitis 

Osteomyelitis is the term that describes bone infections. As with previous secondary infections, the bacteria may reach the bone tissue and cause an infection within it. Symptoms may include fever and fatigue accompanied by pain in the bone.

Bone infections require a lengthy treatment period of 4 to 6 weeks using intravenous antibiotics. In more serious cases, surgery may be necessary to remove parts of the bone.⁹

Systemic complications

Post-streptococcal glomerulonephritis

Post-streptococcal glomerulonephritis (PSGN) is an inflammatory condition of the kidneys caused by a delayed immune response to an initial infection, impetigo in this case, which may sometimes lead to kidney damage. It occurs 1-2 weeks after impetigo resolves and its main symptoms are increased blood pressure, swelling of the face and extremities, and changes in urine.¹⁰

Urine becomes dark in colour and its frequency and output are low. Urinalysis may reveal the presence of blood and protein.¹⁰

Sepsis

Sepsis is a serious and life-threatening condition in which an exaggerated immune response causes the body to injure and shutdown its organs. In the case of impetigo, bacteria from the skin can make its way into the bloodstream. The immune system may get overwhelmed by fighting this infection and causes inflammation in different parts of the body.¹¹ If not recognised on time, this reaction can trigger a cascade of issues from shock to organ failure and eventually death.¹¹

Signs to look out for include any confusion accompanied by breathlessness and clamminess. The individual might experience a feeling of impending doom. Urgent help should be sought if any of the above symptoms are spotted.¹¹

Risk factors

The presence of any of the following factors may increase an individual's risk of experiencing complications:⁵

• Any condition that facilitates the entry of bacteria into the skin, such as cuts or burns
• Living in humid areas
• Inadequate personal hygiene
• Being in close contact with someone who has impetigo
• Being immunocompromised
• Presence of comorbidities such as diabetes
• Babies under 1 year of age

Guidelines for seeking medical help

Any individual with impetigo should monitor their symptoms closely. This means keeping an eye on the shape and colour of the skin lesions.

If the sores continue to spread in the affected area or appear anywhere else in the body, despite undergoing treatment, medical help should be sought to assess the situation and adjust the treatment accordingly.

Patients should also report if they have developed a fever or are feeling unwell as this could indicate the presence of another infection.

Diagnosis and treatment

Medical examination

Diagnosis involves carrying out physical assessments and laboratory tests.

Physical assessment is conducted by observing whether pre-existing lesions have worsened and are not responding to treatment, or whether new ones have appeared either in the same area or elsewhere in the body.¹

Swabs are taken from the skin and sent for microbiological testing to identify the causative organisms. This allows the physician to tailor the treatment accordingly through the use of narrow-spectrum antibiotics which target the exact species and reduce the risk of antibacterial resistance.¹

Certain laboratory tests may be needed to confirm the diagnosis of some complications. These include carrying out a full blood count, a white blood cell count, or a urinalysis. Urea and creatinine levels are measured and used to assess kidney function if PSGN is suspected.¹⁰

Treatment options

The choice of treatment is based on the nature and severity of the complications arising from impetigo. In general, antibiotics are used either topically or orally depending on the location of the infection. In case of PSGN and sepsis, supportive treatment will also be offered for any accompanying symptom. 

The following summarises recommended therapy by case:

• Impetigo (spread of infection): If the infection is not cleared despite the use of first line topical or oral antibiotics, a sample should be collected from the sores and sent for microbiological testing to identify which bacterial strains are responsible. This will allow the physician to switch to a narrow-spectrum antibiotic that is specifically active against these organisms.³ 
• Cellulitis: Oral antibiotics such as flucloxacillin or clarithromycin are offered. Co-amoxiclav should be used if the infection has developed near the nose or eyes.⁶
• Ecthyma: the treatment options for ecthyma are the same used in impetigo. This means the use of the topical antibiotics fusidic acid or mupirocin, replaced by flucloxacillin or clarithromycin orally if the topical agents do not work.⁷
• Osteomyelitis: Flucloxacillin or clindamycin are used for a period of 6 weeks. Fusidic acid or rifampicin may be added for the first 2 weeks.⁹
• Post-streptococcal glomerulonephritis: In addition to antibiotics (penicillin or erythromycin), patients might receive diuretics to reduce the swelling and fluid buildup. If blood pressure is high, special measures such as reducing fluid and salt intake should be tried before introducing any medication, such as calcium channel blockers.¹²
• Sepsis: sepsis requires emergency hospital admission where the patient would receive broad spectrum antibiotics along with oxygen and IV fluids. Microbial cultures will be sent for identification to allow the clinicians to adjust the antibacterial therapy.¹¹

Prevention strategies

In order to reduce the incidence of complications following impetigo, individuals are advised to seek medical help once the infection occurs. This is important as it allows the physician to make a suitable diagnosis and ensure an adequate treatment is received promptly. 

If antibiotics are prescribed, the instructions must be followed properly, and the full course must be completed to reduce the risk of treatment failure and antimicrobial resistance.

Proper hygiene measures should also be maintained at all times by washing hands with soap more often and keeping the infection site clean. Sores should not be scratched or picked at any time as this increases the chance of bacteria reaching the deeper layers of the skin and causing more serious secondary infections.

Since impetigo is a highly contagious condition, care must be exerted when being around someone infected. Sharing towels and personal items must be avoided at all times to stop the infection from spreading to others.

Summary

Impetigo is a fairly common infection that usually heals if the treatment regime is followed and the full course of antibiotics completed. However, there are instances where the treatment fails and leads to the spread of the initial infection or the occurrence of secondary infections. Individuals should monitor the lesions and seek medical help if the condition is not improving or seems to be getting worse. Any new symptoms, such as fever and malaise should also be reported. If sepsis is suspected, emergency care should be sought as soon as possible as early medical intervention improves the clinical outcomes and reduces the risk of death.

Preventive measures reduce the incidence of complications. Maintaining good personal hygiene and caring for the wound properly are strongly advised. Care must be exercised when being around someone who has impetigo since it is highly contagious, and, thus, sharing of personal items should be avoided.