Ecological effects of penicillin prophylaxis in orthognatic surgery.

A study was conducted to evaluate 2 prophylactic penicillin regimens in 18 patients undergoing orthognathic surgery. The effects on the oral microflora were also studied. All patients received 3 g benzyl-penicillin as infusion from the beginning of operation and then 3 g every 6th hour during 24 h. One group of 9 patients then received 1 g phenoxymethylpenicillin as oral suspension twice daily for 6 days postoperatively. The second group of 9 patients received no further penicillin. One infection occurred in this second group, but the patient was cured with metronidazole. 7 of the 9 patients who received penicillin for 1 week, showed pronounced decreases in the number of streptococci and micrococci. In the 9 other patients who received only benzylpenicillin for one day, much smaller changes in the aerobic microflora were observed. Colonization with different enterococci, enterobacteria or yeasts was greater in the group receiving 1-week treatment. No major differences between the 2 groups of patients, concerning the impact on the anaerobic microflora were observed. The results indicate that benzylpenicillin is still a suitable prophylactic antibiotic in maxillofacial surgery. Extension of the antibiotic coverage to 1 week is doubtful because of the increased ecological risks. The clinical significance of anaerobes was obvious, as one postoperative infection occurred caused by an anaerobic micro-organism.