Role of Bacterial Biofilm in Refractory Post Tympanostomy Tube Otorrhea

Abstract

Background/Aim: Bacterial biofilm formation has been implicated in the high rate of refractory otorrhea after tympanostomy tube (TT) insertion. The aim of the work was to assess the role of bacterial biofilm in refractory posttympanostomy tube otorrhea (PTTO) and to determine the types of bacteria that grow on the surface of the TT and their pattern of antibiotic susceptibility. Subjects & Methods: The study was carried out on 40 patients (22 males and 18 females) with TT insertion for treatment of secretory otitis media. Their ages were ranged from 5-13 years with mean of 9.2 ± 2.19 years. Patients are followed up with continuous ENT examination for about 12 months after the TT insertion and then patients were classified into two groups: group1(n=24): the patients not developed PTTO and group 2 (n=16): the patients developed PTTO. Patients of group 2 were treated with local ear drops of antibiotic /corticosteroid combination (ciprocort). According to the results after treatment, group 2 was classified into two subgroups: group 2a (n=4): patients responded to treatment and group 2b (n=12): patients not responded to treatment. From each patient of group 2b, a swab was taken from the external canal and examined bacteriologically and the TT was removed and examined for detection of the bacterial biofilm by two methods (semiquantitative culture and Acridine Orange (AO) staining).The organisms isolated from tube culture were identified by the standard bacteriological methods, tested for antibiotic sensitivity and examined for slime (biofilm) production by two methods: Congo red agar (CRA) plate method and tube method. Results: There were no significant differences between the studied groups as regard age or sex distribution of the patients (P>0.05). Out of the 12 cases of PTTO, only 9 were positive by tube culture and S.aureus was the most frequently isolated organism (55.6%) followed by P.aeuroginosa (44.4%). 60% of the isolated S.aureus and 50% of the isolated P.aeuroginosa were multidrug resistant against most antibiotics used. When comparing AO staining with the semiquantitative tube culture, the AO staining had poor sensitivity and specificity (77.8 % and 66.7 % respectively). Only 8 out of 9 isolated strains were biofilm producer as detected by CRA method whereas only 7 were positive as detected by tube method. There was a very good agreement between the two methods.