Objective. To examine whether Gram staining can influence the choice of antibiotic for the treatment of peritonsillar abscess. Methods. Between 2005 and 2009, a total of 57 cases of peritonsillar abscess were analyzed with regard to cultured bacteria and Gram staining. Results. Only aerobes were cultured in 16% of cases, and only anaerobes were cultured in 51% of cases. Mixed growth of aerobes and anaerobes was observed in 21% of cases. The cultured bacteria were mainly aerobic Streptococcus, anaerobic Gram-positive cocci, and anaerobic Gram-negative rods. Phagocytosis of bacteria on Gram staining was observed in 9 cases. The bacteria cultured from these cases were aerobic Streptococcus, anaerobic Gram-positive cocci, and anaerobic Gram-negative rods. The sensitivity of Gram staining for the Gram-positive cocci and Gram-negative rods was 90% and 64%, respectively. The specificity of Gram staining for the Gram-positive cocci and Gram-negative rods was 62% and 76%, respectively. Most of the Gram-positive cocci were sensitive to penicillin, but some of anaerobic Gram-negative rods were resistant to penicillin. Conclusion. When Gram staining shows only Gram-positive cocci, penicillin is the treatment of choice. In other cases, antibiotics effective for the penicillin-resistant organisms should be used. 1. Introduction Peritonsillar abscess is a localized accumulation of pus within the peritonsillar tissues, which usually results from acute tonsillitis and subsequent peritonsillar cellulitis. This disease is one of the most commonly encountered conditions in ear, nose, and throat (ENT) emergencies. It is characterized by sore throat, trismus, muffed voice, dehydration, dysphagia, and intense pain. Therefore, admission to the hospital is required for some patients with peritonsillar abscess. Intensive therapy may be required in some cases because it may lead to fatal complications, such as deep neck abscess and descending necrotizing mediastinitis . The treatment for peritonsillar abscess involves 2 steps: one is the removal of pus and the other is antibiotic therapy. For effective antibiotic therapy, we usually send the aspirates of the peritonsillar abscess for Gram staining and culture. However, previous reports have denied the effectiveness of bacteriologic studies [2–4]. The aim of this study was to examine the efficacy of bacteriological studies of the peritonsillar abscess, with focus on the Gram-staining characteristics of the bacteria, and determine the value of this method in clinical practice. 2. Materials and Methods A retrospective study was
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