The clinical relevance of microbiologic testing: A comparative analysis ofmicrobiologic samples secured from the same sites and cultured in two independent laboratories

A field study using five different private periodontal practices was conduc ted; it compared two microbiologic culture samples simultaneously secured f rom the same sites within 23 individual patients and submitted for bacteria l identification and antibiotic sensitivity testing to two separate laborat ories. The results from the two laboratories were often different. In no in stance did both laboratories agree on the presence of identical bacterial s pecies. When only bacteria above threshold levels were compared, agreement was found in only nine of 23 cases. When examining antibiotic sensitivity, using 100% kill of all tested pathogens as the ideal, agreement between the two laboratories was poor. The laboratories agreed on the use of amoxicill in 17% of the time, tetracycline 26% of the time, and metronidazole 48% of the time. The use of amoxicillin and metronidazole in combination yielded a 78% agreement when the results of both laboratories were combined, it woul d appear from the data that the empirical use of amoxicillin-metronidazole combination therapy may be more clinically sound and cost effective than cu lturing and antibiotic selection based on the results of culture from any s ingle microbiologic testing laboratory.