S. aureus and K. pneumoniae on the Surface and within Core of Tonsils in Adults with Recurrent Tonsillitis.

Background and Objectives: Recurrent tonsillitis is an infection of the palatine tonsils. Samples for microbiological testing are usually obtained from the inflamed surface of the tonsils. Colonizing the surface bacteria does not always correlate with pathogens causing recurrent tonsillitis and there is no consensus or this in research studies. The aim of the study was to compare whether Staphylococcus aureus (S. aureus) and Klebsiella pneumoniae (K. pneumoniae) differ when isolated from the tonsillar surface or tonsillar crypts in patients with recurrent tonsillitis. Materials and Methods: a case series study was conducted at a tertiary referral center among 25 patients diagnosed with recurrent tonsillitis. An evaluation of S. aureus and K. pneumoniae incidence, biofilm formation and antibacterial susceptibility was performed. Results: There was a statistically significant association between surface and punch biopsy samples for S. aureus (Fisher's Exact test p = 0.004) and K. pneumoniae (Fisher's Exact test p < 0.001). A McNemar test did not reveal a statistically significant association. Although the antibacterial resistance profile was not broad, five out of nine S. aureus isolates were biofilm producers and four out of five K. pneumoniae isolates were biofilm producers. Conclusions: Surface and core cultures of tonsils are comparable with a differing incidence between the surface and the punch biopsy cultures for S. aureus and K. pneumoniae. A larger quantity of bacteria exist in surface samples suggesting that a biopsy sample may be less challenging in evaluating recurrent tonsillitis. We recommend that antibacterial susceptibility results are considered alongside the biofilm-forming potential of isolated bacteria.