3.4 Microbiology
MEF cultures were obtained from all 33 patients (Table 3) and 16 (48.5%) were positive. Fusobacterium necrophorum was the most commonly isolated pathogen (6 patients, 18.2% of all patients), being isolated more frequently in the MCG (5/16, 31.25%) vs . SCG (1/17, 5.9%, P = 0.058. F. necrophorum counted for 6/16 (37.5%) of positive MEF cultures, 5/7 (71.5%) in the MCG vs. 1/9 (11.1 %) in the SCG, P = 0.013.
Streptococcus pneumoniae , either as a single pathogen or in mixed cultures was isolated in 5/9 (55.5%) patients from the SCG and in 0/7 patients from the MCG (P = 0.017). Four out of five (80%) S. pneumoniae isolates were susceptible to penicillin, and all five were susceptible to ceftriaxone.
Two patients had positive mastoid cultures (both of them with the growth of F. necrophorum) reported from the operating theater, while the MEF cultures of these two patients were negative. Two additional patients had a similar pathogen (Streptococcus pyogenes ) isolated from the mastoid and MEF cultures; 14 additional mastoid cultures were reported sterile at the surgery.
When including the mastoid with the MEF cultures, a total of 18 (54.5%) cultures were positive. F. necrophorum counted for 8/18 (44.5%) of total positive cultures, 7/9 (77.8%) in the MCG vs . 1/9 (11.1 %) in the SCG, P = 0.004. Including mastoid positive cultures,Streptococcus pneumoniae was reported more frequently in the SCG, 5/9 (55.5%) vs. 0/9 in the MCG, P = 0.008.