To assess the bacteriaantibiotic interactions in patients with postoperative wound infections, a simple electrophoretic test was performed. To estimate the effectiveness of the antibiotic therapy and to prepare 3-day profiles of bacteria quantity in biological samples, CE was used. As our team demonstrated earlier, the method is easy and fast, sample pretreatment is not necessary, and it is characterized by high selectivity. Finally, the statistically optimal and significant results of the CZE test analysis for detection of Escherichia coli cells was established for migration time lower than 3.5 min. The obtained sensitivity and specificity amounted to 89.5 and 100%, respectively. It is the first application of CZE in the study of medical therapy.