MOLECULAR HYBRIDIZATION VERSUS ISOELECTRIC-FOCUSING TO DETERMINE TEM-TYPE BETA-LACTAMASES IN GRAM-NEGATIVE BACTERIA

Isoelectric focusing and moecular hybridization with a TEM DNA probe were used to screen for TEM .beta.-lactamase in 328 bacterial isolates representing 11 gram-negative genera. The TEM enzyme was detected in 50% of isolates, and nine additional types of .beta.-lactamase could be identified in 36.9% of isolates. The TEM gene was detected in 53.6% of isolates. The results obtained by both methods were concordant in 92.7% of the entire sample. In situ colony hybridization with a specific probe therefore appears to be a convenient method to screen rapidly for the presence of homologous genetic sequences among a large number of isolates. Positive hybridization was observed for 16 isolates in which no TEM .beta.-lactamase detected by isoelectric focusing. The significance of this hybridization remains to be determined.