Orbital cellulitis is an emergency that may be life-threatening if it spreads to the intracranial space. It is an infection of the soft tissues of the orbit posterior to the orbital septum, usually caused by organisms originating in the upper respiratory tract or skin and although it can occur at any age, it is more common in the paediatric population [1,2,3]. CT imaging of the head is almost always indicated following empiric antimicrobial therapy due to the difficulty in clinically excluding the presence of a subperiosteal or orbital abscess [4]. Antimicrobial therapy is effective management in most patients, with source control requiring surgical intervention [2, 5].

There is significant variation in the antibiotic choice used to treat orbital cellulitis [1]. The largest complete data set of treatment outcomes of children diagnosed with orbital cellulitis included 1828 children reporting over 200 different variations of antibiotics used [6]. We searched local, national and international guidelines for the first-line management of orbital cellulitis in a patient without a penicillin allergy or suspected methicillin-resistant Staphylococcus aureus (MRSA) (Table 1). We identify variation in guidance for antimicrobial choice, dose and duration, highlighting the need for consistent UK recommendations for the treatment of orbital cellulitis.

Table 1 Orbital cellulitis guidelines.
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Antimicrobial choice

Empiric antimicrobial therapy should cover the most common causative organisms, including Streptococcus spp., Staphylococcus aureus and in older children, polymicrobial infections with aerobic and anaerobic bacteria [1,2,3]. In areas with low rates of MRSA, such as the UK [7], intravenous co-amoxiclav is a single-drug therapy that provides adequate aerobic and upper respiratory tract anaerobic cover [1]. For infections with risk of intracranial spread, empiric antibiotics with high central nervous system penetration are required. Ceftriaxone (or cefotaxime in indicated groups) [8] provides aerobic cover, with good penetration of the blood–brain barrier; it should be used with metronidazole, which provides good anaerobic cover. In cases of suspected MRSA, a combination of a third-generation cephalosporin (e.g. ceftriaxone) with vancomycin may be indicated. Immunocompromised patients have greater risk of atypical infection and antimicrobial choice should be discussed closely with infectious disease specialists or microbiologists. In the UK there is significant variation in empiric antibiotic choice (and route of administration) between local NHS Trusts, national guidance and international standards (Table 1).

Dosing

Antibiotic dosing is more complex in paediatric patients than adults, with careful consideration needed with the safety profile of the antibiotic, pharmacodynamics between the drug and bacteria and the differences in pharmacokinetics between adults and children. A recent study identified marked heterogeneity in widely used paediatric antibiotic formularies in middle and high-income countries for commonly prescribed antibiotics, including those used to treat orbital cellulitis (Table 2) [9]. As well as variation between these guidelines, there are also differences between some local NHS Trust dosing recommendations (where available) and British National Formulary for children recommendations. Correct dosing for paediatric patients is essential to effective treatment of infection, avoiding toxicity and reducing the risk of antimicrobial resistance.

Table 2 Paediatric antimicrobial dosing guidelines.
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Duration

Like other serious infections, intravenous antibiotics can be stepped down to an oral regimen when there are signs of improvement in orbital cellulitis. Oral antibiotics should continue for the shortest effective duration to reduce the risk of antimicrobial resistance and adverse events. Local NHS Trust guidelines vary in total treatment duration, including both intravenous and oral antibiotics, from no specific time frame to up to 21 days (Table 1). McMullan et al. [10] recently reviewed the evidence to provide the shortest safe duration of antibiotic therapy to treat a range of paediatric infections, recommending a total duration of 7–10 days for orbital cellulitis.

Recommendations

We have identified significant national variation in antimicrobial choice, dose, total duration and when to step down from intravenous to oral antibiotics to provide the shortest effective duration of therapy for the first-line treatment of orbital cellulitis in children. This level of variation is hard to justify. Never has there been more emphasis on the threat antimicrobial resistance poses to the future of healthcare and the importance of antimicrobial stewardship. To achieve the WHO’s Global Action Plan on Antimicrobial Resistance there must be efforts to optimise antibiotic use [11]. The variations identified here highlight the need for consensus-based UK guidelines for the treatment of paediatric infections such as orbital cellulitis, with an optimal antibiotic, dose and duration, as outlined above. This is being addressed through collaboration between the British Society for Antimicrobial Chemotherapy, Royal College of Paediatrics and Child Health, ENT UK and the Royal College of Ophthalmologists paediatrics sub-committee.