Morphological Effects of β-lactam Antibiotics on the Leptospira Cells

The morphological effects of β-lactam antibiotics, such as cefmetazole (CMZ), cephalexin (CEX) and penicillin-G (PC-G), on the cells of Leptospira canicola were investigated under electron microscopy. The efficacious concentrations of the antibiotics were decided to be 0.1μg/ml and 1.0μg/ml of CMZ, 1.0μg/ml and 10.0μg/ml of CEX, and 0.1u and 1.0u/ml of PC-G, respectively. Specimens were prepared from the cultures of leptospira cells with mass inoculation in Korthof's media, is containing the drugs with above concentrations, and incubated at 30℃ for 12 and 48hrs (CEX exceptional, for 4 days). The former incubation time corresponds to the logarithmic phase and the latter to the reducing phase on the growth curves. No remarkable difference could be observed in the morphological effects of cells among these drugs, however, much differences in the damages could be seen between two incubation times. The most definite effects were the subterminal ghost formation at one pole of the main body and appearance of the spherical body (SB) of swelling type in the 12 hours incubation. Formation of the whole cell ghost and of SB (of rolling type) could be seen in the 48 hours incubation. Through the process of these two different times of incubation, several types of intermediate form of SB were seen. From these morphological effects by the treatment of the antibiotics, the fundamental organization of the main body of leptospira cell and the formation process of SB with several types were discussed.