Discussion
In the review of the literature to date, no significant clinical harm has been reported using oral formulations of phenoxymethyl penicillin alone as part of peritonsillar abscess incision and drainage interventions in the treatment of peritonsillar abscess. Specifically, here, the studies focussed on the clinical outcomes rather than the microbiology findings.  We have not focussed the polymicrobial nature of pus samples from quinsy and antibiotic administration.  This is because ultimately resolution of symptoms and clinical cure is the priority in these patients.
All studies advocated the use of either needle aspiration or incision and drainage as the source control measure in addition to the appropriate administration of antibiotics, and this is a well-documented treatment in the literature.25 It is the general consensus that antibiotics alone are not appropriate for the treatment of peritonsillar abscess, and the literature has shown no difference in effectiveness between needle aspiration vs incision.4What differed between the studies reviewed, was the use of aspiration or incision and drainage. Turner et al 1986 performed daily aspiration or incision and drainage for up to 10 days or until no more pus was drained. At the end of the 10 days, patients in both groups were deemed completely treated, and no recurrence was demonstrated. In contrast Wiksten et al 2016 performed needle aspiration on day one and then monitored for signs of recurrence within a 56-day window. One could argue daily drainage is eliminating the risk of any potential recurrence from sub-therapeutic antibiotic therapy, and therefore it is hard to assess accurately the effect of the antibiotic.
This systematic review is a useful addition to the literature in the context of rationalising antimicrobial choice that provides effective clinical cure without unnecessarily broadening the antimicrobial spectrum of activity. In the context of increasing burden of antimicrobial resistance26, the current evidence (such as it is) suggests that addition of a second agent specifically targeting anaerobes (Metronidazole) and other pathogens (Sulbactam-Ampicillin) does not provide additional clinical benefit. Further optimisation of therapy to improve clinical efficacy and lessen impact on resident flora from single agent oral phenoxymethyl penicillin may be considered in context of optimising dose, frequency and duration. Furthermore all three studies used a 10 day treatment duration for which evidence is lacking. In line with other specialties reviewing the use of shorter duration of antimicrobials whilst maintain clinical efficacy, it would be appropriate to consider shorter courses in the light of improvements in clinical signs and symptoms and effective surgical drainage.
When analysing potential benefit of the addition of metronidazole to penicillin for the treatment of peritonsillar abscess, another important factor to consider is cost. A typical course of oral  metronidazole is 400mg three times a day for seven days, with a cost of around £2.17 in the NHS.28 The current evidence does not support the routine use of metronidazole (or second agent) in the routine management of quinsy, therefore there is the potential for cost saving if only single therapy penicillin is prescribed.