Microbiology of Peritonsillar Abscess Aspirates A retrospective audit of the past two years in a teaching hospital A Bartlett 1, AJ Plant 2, T Malik 1 1 ENT Department, Derriford Hospital, Plymouth 2 Department of Medical Microbiology, Derriford Hospital, Plymouth Introduction A peritonsillar abscess is a complication of supparative tonsillitis in which pus accumulates between the capsule of the palatine tonsil and the superior pharyngeal constrictor muscle. Typically patients present with unilateral sore throat associated with fevers, trismus and dehydration. It is a common ENT emergency, with a risk of airway obstruction if infection spreads into the deep neck spaces. The condition most commonly affects adults aged 20 to 39 years, and if it occurs for the first time in the older patient, underlying malignancy must be considered. It has been suggested that the incidence of peritonsillar abscess is increasing in the UK, possibly as a result of a reduction in the number of tonsillectomies being performed and in antimicrobial prescribing by general practitioners. 1 Figure 1: Clinical photograph showing right peritonsillar abscess, also known as quinsy. Pus has collected in the peritonsillar space, causing palatal swelling, and uvula deviation away from the affected side. There is also pooling of saliva demonstrating difficulty swallowing. Unlike the patient in this photograph, many patients have significant trismus, causing a “hot potato” voice and making examination of the oropharynx difficult. Background Microbiology: The commonest organisms accounting for monomicrobial infections are Group A streptococcus and Fusobacterium necrophorum, however the majority are polymicrobial containing common oropharyngeal microflora. 2 Pathogenesis: Disruption of the oropharyngeal host-commensal relationship leads to localised tissue invasion resulting in peritonsillar abscess formation. 2 There are currently two hypotheses that explain the pathogenesis of this event. The first is that it is a complication of acute supparative tonsillitis. 2 The second suggests that abscess formation occurs due to blockages in the minor salivary glands on the soft palate (Weber glands) that normally help to maintain the peritonsillar niche. Infection of these glands or poor oropharyngeal hygiene could lead to scarring and reduced salivary flow, providing an opportunity for peritonsillar invasion and infection. 3 Management: Suspicion of peritonsillar abscess requires urgent review by an ENT specialist. Diagnosis is clinical or by attempted needle aspiration in which pus is obtained. Although a CT scan will demonstrate the presence of a peritonsillar abscess, it is not usually required and should be reserved for patients with suspected deep neck space infection. 1 Generally, patients require admission to hospital until they are able to eat and drink normally. A combination of benzylpenicillin and metronidazole given intravenously will be effective against aerobic and anaerobic bacteria in the majority of cases. 1 In patients with a penicillin allergy, clindamycin may be used as an alternative. Although there are no national guidelines on the management of this condition, surveys have demonstrated that most ENT departments perform either incision and drainage or needle aspiration in addition to appropriate antimicrobials. 4 Complications: Although most patients make an uneventful recovery, serious complications can occur. These include recollection, spread into the deep neck spaces, and spontaneous abscess rupture leading to aspiration of pus. Literature Several studies have suggested that routine culture and sensitivity of peritonsillar abscess aspirate does not affect management. 1,5 It has only been recommended for patients with risk factors for more complex infection, such as diabetic or otherwise immunocompromised patients or those with recurrent collections. 1,5,6 In a telephone survey of 86 ENT departments across the UK, 67% said they routinely culture peritonsillar abscess aspirate, however only 28% of these are routinely followed-up. 7 References 1.Powell J &Wilson JA. An evidence-based review of peritonsillar abscess. Clin. Otolaryngol 2012; 37: Powell EL et al. A review of the pathogenesis of adult peritonsillar abscess: time for a re-evaluation. Journal of Antimicrobial Chemotherapy 2013; 68: Passy V. Pathogenesis of peritonsillar abscess. Laryngoscope 1994; 104: Mehanna HM et al. National audit of the management of peritonsillar abscess. Postgrad Med J 2002; 78: Repanos C et al. Role of microbiological studies in the management of peritonsillar abscess. JLO 2009; 123: Cherukuri S & Benninger MS. Use of Bacteriologic Studies in the Outpatient Management of Peritonsillar Abscess. Laryngoscope 2002; 112: Nelson TG, Hayat T, Jones H, Weller MR (2000) Use of bacteriologic studies in the management of peritonsillar abscess. Clinical Otolaryngology 34;88-89 Aim To review the last two years of peritonsillar abscess aspirates to determine whether our practice is in accordance with current literature. Methods Cultures from peritonsillar abscesses were retrospectively identified during the defined 2 year audit period using the Trust’s laboratory information management system (iLab). Search criteria to obtain the appropriate specimens included any sample labelled as “pus” or “aspirate” from the department of ENT surgery. These were then filtered by site: either “peritonsillar abscess” or “quinsy” – according to the attached request card associated with the specimen. Data on the final culture and outcome of antimicrobial sensitivity testing was then compiled as it would have been authorised to the requesting clinician at the time. A review of each patient’s discharge summary and laboratory results was then performed, and data collected to ascertain patient demographics, co-morbidities, management, length of hospital stay and outcomes. Indications for culture of peritonsillar abscess aspirates (Audit standard): 1.Recurrent collection 2.Suspicion of deep neck space infection 3.Immunocompromised patient AntimicrobialNumber of patients Benzylpenicillin and metronidazole12 Co-amoxiclav1 Clindamycin (penicillin allergy)2 Erythromycin and metronidazole (penicillin allergy) 1 OrganismNumber of cultures (%) β-haemolytic streptococci +/- mixed anaerobes 6 (35%) Commensals5 (29%) α-haemolytic streptococci +/- mixed anaerobes 2 (12% No growth2 (12%) Mixed anaerobes1 (6%) F. necrophorum1 (6%) Table 1: Antimicrobial choice. All 16 patients were commenced on empirical antimicrobial treatment as well as being treated by abscess drainage. Table 2: Culture results. Of the 17 samples, 10 had sensitivity testing. All organisms were sensitive to either penicillin, metronidazole or clindamycin. Outcomes In all cases, organisms cultured were sensitive to the empirical antimicrobials. The average length of stay was 1.76 days, with a range of one to five days. One patient required re-admission due to a re-accumulation of the abscess 24 hours after discharge. Aspirate samples were sent for culture and sensitivities on both occasions, and cultured β-haemolytic streptococci sensitive to penicillin. Benzylpenicillin and metronidazole were commenced empirically and continued in this patient, and therefore culture results did not result in a change of management, although they would have been useful to guide antimicrobial treatment since re-collection had occurred. Discussion The above results demonstrate that 10% of cases of peritonsillar abscess had pus sent for routine cultures over the past two years. In a previous review of 577 patients treated for peritonsillar abscess over a 10 year period in southwest England, 20% had pus sent for cultures. 5 There was no particular reason documented for the culture request in these patients, and none were immunocompromised. 5 The authors suggested that this decision may be based on personal experience and preference of the treating clinician. 5 In our study, none of the patients were elderly or immunocompromised, i.e. none of the patients had risk factors for unusual, severe or resistant infection. Only one patient (16%) had a recurrent collection i.e. a valid reason for aspiration according to current literature. Only 3 out of 16 patients were admitted for more than 48 hours, meaning that culture and sensitivity results were unlikely to be available prior to discharge. Benzylpenicillin and metronidazole are commonly used, and will be effective in most cases since the common causative organisms are β-haemolytic streptococci and anaerobes, as demonstrated above. Since the cost of performing culture and sensitivity testing is £10.55 per sample in our trust, had pus cultures been requested in every patient diagnosed with peritonsillar abscess over the past two years, a cost of £ would have been incurred. Conclusions Although there are no national guidelines on the management of this condition, surveys have demonstrated that most ENT departments perform either incision and drainage or aspiration plus antimicrobial treatment (Mehanna et al. 2002, Nelson et al. 2009). This concurs with our routine management of peritonsillar abscess. There is no suggestion however that routine culture of the aspirated pus is clinically useful in uncomplicated cases. It is possible that rare complications could be missed if routine cultures are not sent, however it appears that in the majority of cases results are not available before patient discharge and therefore are not having an effect on patient management. Results Over a two year period between June 2012 and June 2014, 170 patients had peritonsillar abscess coded as their primary diagnosis at a single tertiary ENT centre (average of 7 cases per month). Following a search of the Trust’s laboratory information system, 17 peritonsillar aspirate samples from 16 patients were identified over the same time period. Patient demographics: Aspirate samples were sent from seven women and nine men, with an average age of 27 years (range years). All patients were generally fit and well. Thirteen had no significant past medical history recorded, whereas three patients had a history of asthma as their only co-morbidity.