Ordering and interpreting ear swabs in otitis externa Carl Llor,1 Cliodna A M McNulty,2 Christopher C Butler1 3 1
Institute of Primary Care and Public Health, School of Medicine, Cardiff University, Cardiff CF14 4XN, UK 2 Public Health England Primary Care Unit, Microbiology Department, Gloucestershire Royal Hospital, Gloucester, UK 3 Department of Primary Care Health Sciences, Oxford University, Oxford, UK Correspondence to: C Llor [email protected]
Cite this as: BMJ 2014;349:g5259 doi: 10.1136/bmj.g5259
This series of occasional articles provides an update on the best use of key diagnostic tests in the initial investigation of common or important clinical presentations. The series advisers are Steve Atkin, professor of medicine, Weill Cornell Medical College Qatar; and Eric Kilpatrick, honorary professor, department of clinical biochemistry, Hull Royal Infirmary, Hull York Medical School. To suggest a topic for this series, please email us at [email protected]
An otherwise healthy 25 year old woman was initially treated by her general practitioner with a 10 day course of topical antibiotic and steroid eardrops for unilateral ear fullness and pain, which was diagnosed as otitis externa. She consults again seven days later because of ongoing ear pain, discharge, and reduced hearing, despite having used the ear drops as prescribed. She has not been feverish. On examination, her left pinna is tender and her ear canal is diffusely swollen and erythematous, with a grey exudate dotted with dark debris.
What is the next investigation? This patient’s symptoms have not improved after initial treatment. Her GP still considers this to be otitis externa, so decides to prescribe an oral non-steroidal anti-inflammatory drug and take a swab from the discharge in the ear canal. Is this the best course of action? When should ear swabs not be used? No randomised trial has evaluated different ear canal swabbing strategies in otitis externa, and guidelines based on expert opinion recommend empirical antimicrobial eardrops without swabbing in uncomplicated otitis externa—that is, otitis externa without immunosuppression or high temperature.1 Empirical treatment Although there are no trials of oral versus topical antibiotics as initial empirical treatment, consensus recommendations favour topical drugs alone for uncomplicated otitis externa.1 However, observational studies have found that inappropriate antimicrobial treatment for otitis externa is common, and that oral antibiotics are prescribed by GPs to 25-45% of patients with this condition.2 3 Topical antibiotics are also
LEARNING POINTS Investigations are rarely useful in a first episode of uncomplicated otitis externa. Ear swabs are not recommended. First line empirical treatment includes topical 2% acetic acid, with antimicrobial eardrops, such as an aminoglycoside (if the tympanic membrane is intact), as second line. Aural toilet and analgesia may also be indicated Consider swabbing the ear canal for culture to identify likely pathogens and susceptibilities in the following circumstances only: ––The condition does not improve after initial empirical topical treatment ––Otitis externa is recurrent or chronic ––After ear surgery ––Topical treatment cannot be delivered effectively ––There is suspicion that the infection has extended beyond the external auditory canal ––The condition is severe enough to require systemic antibiotic treatment The most common infective causes of otitis externa are Pseudomonas aeruginosa and Staphylococcus aureus, both of which are covered by acetic acid or aminoglycoside drops Avoid targeting antimicrobial treatment to common commensal organisms of the ear canal Direct treatment of polymicrobial infections to those pathogens most likely to cause severe otitis externa (S aureus, Streptococcus pyogenes, Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis)
the treatment of choice for acute otitis media with discharge and acute tympanostomy tube otorrhoea.4 It is sometimes difficult to distinguish otitis externa from otitis media with discharge when there is discharge and swelling in the canal, but visualisation of an intact tympanic membrane rules out otitis media. A seven to 10 day course of topical antibacterial eardrops, with or without topical steroids, is more effective than placebo.5 Meta-analysis of two randomised placebo controlled trials found that only two patients need to be treated with topical antimicrobials to achieve one additional cure.5 Effective topical treatments include antiseptics (acetic acid, boric acid) and antibacterials, with or without steroids. There were no meaningful differences in clinical outcomes assessed at one week between treatment classes (antiseptics v antibiotics) or types of antibiotic (quinolones v non-quinolone antibiotics) in otitis externa.5 Guidelines from Public Health England recommend 2% acetic acid spray for seven days as first line empirical treatment because this covers most of the common bacterial and fungal causes. Aminoglycosides with steroid drops are recommended as second line (table).6 Whereas topical antibiotics have fewer side effects than systemic antibacterial agents, topical aminoglycosides cause local hypersensitivity in about 15% of cases.7 They can also be ototoxic, so are contraindicated if perforation of the tympanic membrane cannot be ruled out on examination. Quinolone eardrops are more effective than placebo or antiseptics for chronic suppurative otitis media.8 Most people feel better within the first 48-72 hours of starting topical treatment, but complete recovery can take up to two weeks.1 Pain relief is an essential component of managing otitis externa, and paracetamol or non-steroidal anti-inflammatory drugs are usually effective. Effective communication with patients is a necessary part of maximising adherence to topical treatment. Only 40% of patients who instil eardrops for themselves do so as recommended during the first three days.9 Encourage patients to instil drops while they recline, with the affected ear facing upward and remaining so for at least three minutes. Gentle to and fro movement of the pinna is often necessary to eliminate trapped air and ensure exposure of the drops to the entire canal. Adherence is generally better when someone other than the patient applies the drops.1 GPs may consider referring patients with large amounts of debris or discharge, because removal under an operating microscope may reduce the microbial load and improve exposure to topical drugs. However, no randomised controlled trial has evaluated the benefits of aural toilet in otitis externa.5
When should an ear swab be taken in suspected otitis externa? It is appropriate to take an ear swab in suspected otitis externa in the following situations: • If symptoms do not improve within two weeks of starting empirical topical treatment: Treatment should
the bmj | 13 September 2014
EDUCATION PRACTICE thebmj.com Previous articles in this series ЖЖDiagnosis of immediate food allergy (BMJ 2014;349:g3695) ЖЖInvestigation of suspected urinary tract infection in older people (BMJ 2014;349:g4070) ЖЖInvestigating hypophosphataemia (BMJ 2014;348:g3172) ЖЖInterpreting raised serum prolactin results (BMJ 2014;348:g3207) ЖЖUsing haemoglobin A1c to diagnose type 2 diabetes or to identify people at high risk of diabetes (BMJ 2014;348:g2867)
Organisms that commonly cause otitis externa and recommended clinicians’ responses Type of organism
Recommended clinicians’ responses according to culture result
Common commensals of the ear canal
Coagulase negative staphylococci (Staphylococcus epidermidis, S auricularis), coryneforms (diphtheroids), enterococci, Proteus spp Pseudomonas aeruginosa, non-group A streptococci, fungi (aspergillus, candida), anaerobes (Propionibacterium acnes, peptostreptococcus, clostridium), coliform species
No treatment needed
Uncommon constituents of normal flora in the ear canal that can rarely cause severe disease
Uncommon constituents of the normal flora of the ear canal that can cause severe disease
Staphylococcus aureus, Streptococcus pyogenes, Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis
be considered a failure if symptoms persist beyond two weeks. GPs should first consider suboptimal administration of topical treatment. They should also check for ongoing risk factors such as use of hearing aids or ear plugs, lack of adherence to preventive measures such as avoiding water entering the ear canal, contact dermatitis, a retained foreign body, and self instrumentation trauma (for example, use of cotton buds). Other possible differential diagnoses include cancer, malignant otitis externa, and underlying canal cholesteatoma. Cholesteatoma, which is usually painless but may produce a sense of ear fullness, should be referred to a specialist • If topical treatment cannot be delivered effectively: A culture result may help guide the choice of oral antibiotic treatment • Recurrent otitis externa, chronic otitis, and infections after aural surgery: Roughly one in five patients will have a recurrence of otitis externa within a year. Otitis externa is classified as chronic when symptoms have lasted longer than three months. Uncommon organisms, such as anaerobes and fungi, are more often isolated in recurrent episodes • When malignant otitis externa is suspected: Clinicians must consider this diagnosis in any case of otitis externa that is refractory to well conducted topical treatment, mainly in patients with altered host defences, immunosuppression, uncontrolled diabetes, Symptoms of malignant otitis externa Suspect malignant otitis externa if the patient does not improve with well administered topical treatment, has refractory purulent otorrhoea, and also has: • Extension of the infection beyond the external ear canal • Intense otalgia that worsens at night • Immunosuppression • Diabetes • Fever and malaise • Headache • Temporal mandibular joint pain • Trismus • Osteomyelitis of the skull base • Cranial nerve palsy (mainly of the facial nerve) • Granulation tissue on the floor of the ear canal
Pseudomonas, non-group A streptococci, anaerobes, and coliforms can usually be treated with topical antiseptics alone (acetic acid), with aminoglycosides as second line therapy (if the tympanic membrane is intact), unless the infection is severe. Antiseptics are also recommended for fungal infections, with topical antifungals, such as imidazoles (clotrimazole, miconazole) or tolnaftate as second line therapy, unless the infection is severe. Consider systemic treatment (based on susceptibilities reported) if the infection is severe Topical antibiotics, such as aminoglycosides (if the tympanic membrane is intact), polymyxin B, or quinolones (ciprofloxacin or ofloxacin), are often recommended unless infection is severe. Consider systemic treatment (based on susceptibilities reported) if the infection is severe
or a history of local radiotherapy, and in those who feel ill. This rare but severe infection is most commonly caused by pseudomonas (box). It requires urgent culture of the discharge, prompt referral for initial inpatient parenteral antibiotic treatment,10 and diagnostic confirmation by computed tomography or magnetic resonance imaging, which delineates subtle changes in bone density and establishes the extent of soft tissue swelling.
How should ear swabs be taken, processed, and interpreted? A swab of pus or fluid from the ear canal should be placed in Amies transport medium with charcoal, transported in a sealed plastic bag, and processed as soon as possible using direct microscopic examination and culture for bacteria and fungi.11 Identifying possible pathogens Cultures may simply reflect commensal or bystander colonising organisms, and this should be taken into account when interpreting the results (table), because these supposed infections should not be treated.12 13 The most common causes of otitis externa are Pseudomonas aeruginosa (prevalence of 20-60%) and Staphylococcus aureus (prevalence of 10-70%).14 15 Pathogens commonly responsible for otitis media—Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis—are not part of the normal flora of the external canal when the tympanic membrane is intact. Polymicrobial infections are found in about a third of otitis externa cases.1 Treatment of these infections should focus on those pathogens most likely to cause severe disease (table 1).13 Bacterial resistance Resistance of pseudomonas to polymyxin B, aminoglycosides, and ciprofloxacin and of S aureus to aminoglycosides is less than 2% in the United Kingdom,14 possibly because aural tissue concentrations are higher for topical antibacterials than for systemic antibiotics.1 However, unless the infection is severe, these infections can be treated effectively with antiseptics alone.6 Conservative use of oral antibiotics for otitis externa is important because of increasing antimicrobial resistance. Moreover, many oral antibiotics prescribed by GPs for ear discharge are ineffective against P aeruginosa 13 September 2014 | the bmj
EDUCATION PRACTICE and S aureus. Ear swab culture results should guide choice of oral antibiotic class for otitis externa. The Health Protection Agency (now Public Health England) microbiology laboratory use group recommends reporting antibiotic susceptibility testing to common topical antimicrobials in addition to susceptibilities to commonly used oral antibiotics.13
government funded Wales School of Primary Care Research and has received grants from several publicly funded research granted bodies as well as honorariums for participation in workshops. Provenance and peer review: Commissioned; externally peer reviewed. Patient consent: Patient consent not required (patient anonymised, dead, or hypothetical).
Outcome Our patient’s clinical picture did not suggest malignant otitis externa. The swab culture showed a polymicrobial infection that included coagulase negative staphylococci and diphtheroids, with a predominant growth of Aspergillus niger. However, antimicrobial susceptibility was not reported. Otomycosis is an underdiagnosed problem, especially in recurrent otitis externa, and it often follows the use of topical antibiotics with steroids for acute otitis externa. Guidelines recommend aural toilet, acidifying local agents, or topical antifungals such as clotrimazole containing eardrops, which are safe, even in patients with a perforated eardrum.14 An antifungal susceptibility profile was not necessary because antifungal resistance is rare, and most infections are mild and respond well to topical antifungal eardrops. The laboratory also did not report susceptibility of commensals because this does not help to guide treatment.
Contributions: All three authors helped prepare the manuscript. CCB is guarantor. Competing interests: CL has received research grants from the European Commission (Sixth and Seventh Programme Frameworks), Catalan Society of Family Medicine, and Instituto de Salud Carlos III. CAMMcN has no conflicts to declare. She has spoken at antimicrobial resistance symposiums sponsored by public bodies and one by bioMerieux but received no payment. She leads the development of national Public Health England antibiotic guidance for GPs, which covers otitis media and otitis externa. She has received grants from several publicly funded research bodies. CCB is director of the Welsh
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Rosenfeld RM, Schwartz SR, Cannon CR, Roland PS, Simon GR, Kumar KA, et al. Clinical practice guideline: acute otitis externa. Otolaryngol Head Neck Surg 2014;150(1 suppl):S1-24. Collier SA, Hlavsa MC, Piercefield EW, Beach MJ. Antimicrobial and analgesic prescribing patterns for acute otitis externa, 2004-2010. Otolaryngol Head Neck Surg 2013;148:128-34. Pabla L, Jindal M, Latif K. The management of otitis externa in UK general practice. Eur Arch Otorhinolaryngol 2012;269:753-6. Van Dongen TM, van der Heijden GJ, Venekamp RP, Rovers MM, Schilder AG. A trial of treatment for acute otorrhea in children with tympanostomy tubes. N Engl J Med 2014;370:723-33. Kaushik V, Malik T, Saeed SR. Interventions for acute otitis externa. Cochrane Database Syst Rev 2010;1:CD004740. Public Health England (HPA). Management of infection guidance for primary care for consultation and local adaptation. 2013. www.hpa.org. uk/Topics/InfectiousDiseases/InfectionsAZ/PrimaryCareGuidance/. Smith IM, Keay DG, Buxton PK. Contact hypersensitivity in patients with chronic otitis externa. Clin Otolaryngol Allied Sci 1990;15:155-8. Macfayden CA, Acuin JM, Gamble CL. Topical antibiotics without steroids for chronically discharging ears with underlying eardrum perforations. Cochrane Database Syst Rev 2005;4:CD004618. England RJ, Homer JJ, Jasser P, Wilde AD. Accuracy of patient selfmedication with topical eardrops. J Laryngol Otol 2000;114:24-5. Guevara N, Mahdyoun P, Pulcini C, Raffaelli C, Gahide I, Castillo L. Initial management of necrotizing external otitis. Errors to avoid. Eur Ann Otorhinolaryngol Head Neck Dis 2013;130:115-21. Health Protection Agency. B 1: Investigation of ear swabs and associated specimens. UK standards for microbiology investigations. 2012. www. hpa.org.uk/SMI/pdf. Stroman DW, Roland PS, Dohar J, Burt W. Microbiology of normal external auditory canal. Laryngoscope 2001;111:2054-9. Geyer H, Howell-Jones R, Cunningham R, McNulty C. Consensus of microbiology reporting of ear swab results to primary care clinicians in patients with otitis externa. Br J Biomed Sci 2011;68:174-80. Ninkovic G, Dullo V, Saunders NC. Microbiology of otitis externa in secondary care in the United Kingdom and antimicrobial sensitivity. Auris Nasus Larynx 2008;35:480-4. Roland PS, Stroman DW. Microbiology of acute otitis externa. Laryngoscope 2002;112:1166-77.
Breast lumps M Twoon,1 N Y B Ng,1 S E Thomson2 1
University of Aberdeen, Aberdeen, Scotland 2 Plastic and Reconstructive Surgery Unit, Aberdeen Royal Infirmary, Aberdeen, Scotland Correspondence to: [email protected]
Cite this as: BMJ 2014;349:g5275 doi: 10.1136/bmj.g5275
This is part of a series of occasional articles on common problems in primary care. The BMJ welcomes contributions from GPs
A 35 year old woman presents with a 1 cm hard lump in the upper outer quadrant of her right breast. She first noticed this when she was in the shower three months ago. She is worried that the lump might be malignant.
What you should cover Breast lumps are common and have a variety of causes. Although most lumps are not malignant, any abnormal changes to the breasts need to be reviewed as soon as possible. Refer patients to a breast clinic where triple assessment can be performed and the lump fully investigated. It is often difficult to make a definitive diagnosis on clinical history and examination alone. Many patients who are referred for specialist assessment will be found not to have cancer. Examination Undertake a clinical breast examination, with consent and chaperone. People have different techniques and, although the following technique is recommended, it is by no means the only acceptable one.
• Compare both sides, and include all four quadrants,
the retro-areolar area, and axillary tail. Examine the axilla and supraclavicular areas for lymphadenopathy. • Note the location of lump; its consistency; tethering to overlying or underlying structures; and associated features of lymphadenopathy, skin changes (such as peau d’orange—skin with an “orange peel” appearance owing to invasion of the lymphatics by tumour cells, which causes obstruction and oedema), or nipple discharge. I • f nipple discharge is clearly evident send a sample for microbiology and cytology. • An eczematous rash might represent Paget’s disease of the nipple and underlying cancer. Compare both nipples for evidence of eczema or Paget’s disease. Eczema tends to be bilateral with marked itching. Furthermore, there tends to be a history of atopy and areas of eczema on multiple sites of the body. Paget’s disease tends to be unilateral with associated bleeding and nipple erosion.
the bmj | 13 September 2014
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