Acute mastoiditis. Influence of antibiotic treatment on the bacterial spectrum.

The work was undertaken to investigate the spectrum of bacteria responsible for acute mastoiditis and to find out whether it is affected by intake of antibiotics prior to surgical treatment. The records were reviewed of 22 children with acute mastoiditis in whom mastoidectomy had been performed and bacterial cultures obtained. Eleven of the patients had had antibiotic treatment prior to admission (9 penicillin V and 2 erythromycin). Streptococcus pneumoniae was found in 8 of the purulent discharges: Haemophilus influenzae, Streptococcus beta-hemolyticus and Staphylococcus aureus in 2 each; Proteus mirabilis, Pseudomonas pyocyaneus and a Bacteroides strain in 1 each, while five discharges-all from patients pretreated with antibiotics-yielded no growth. None of the 9 patients pretreated with penicillin V provided pure cultures of pneumococci or beta-hemolytic streptococci, while one or the other of these species was found in 8 of the 11 untreated patients. Gram-negative bacteria were found both among those with and those without antibiotic pretreatment. The data indicate that pneumococci and beta-hemolytic streptococci are more likely to cause mastoiditis than are the other pathogens found in acute otitis media, and that, when drained at operation, purulent discharges are often found to have been sterilized by the pre-operative antibiotic treatment.