Microbiology of acute otitis media with a tympanostomy tube

Abstract

Objectives: The first large case series of acute otitis media through tympanostomy tubes (TT) is presented. Methods: Over 1000 specimens obtained from over 800 children with draining tympanostomies were evaluated prior to treatment. An additional 30 specimens from treatment failures were also examined. All samples were taken from the orifice of the TT. Organisms were characterized phenotypically and genotypically (DNA ribotyping) to the subspecies level. Results: Positive cultures were recovered from 84% of subjects overall but there was great seasonal variation. The “No growth” rate was 4.5% in the summer but 34% in the winter; 95% of recovered organisms were bacterial. The most common organisms, in descending order, were: S pneumo, S aureus, P aerug, H flu, and S epiderm. Of 30 isolated from treatment failures, DNA ribotyping demonstrated that in 13 cases the original organism persisted; the remaining treatment failures were due to reinfection. The susceptibility of pretreatment isolates did not predict treatment failure and there was no change in susceptibility profile during treatment. Conclusions: (1) The distribution of bacterial pathogens was significantly different from that seen in AOM with an intact TM. (2) Systemic antibiotics used to treat AOM with an intact TM are frequently inappropriate. (3) The higher rate of “no growth” in winter suggests a possible role for “nonbacterial” AOM during this season (4) The incidence of recovery of fungal organisms is higher than anticipated and raises concern about the utility of antibacterial therapy in these cases. (5) There is no evidence that resistance follows topical treatment.