Reactivity of Neutrophil-Like HL-60 Cells towards Persistent Forms of Escherichia coli

The aim was to study the reactivity of neutrophil-like HL-60 cells towards native E. coli and E. coli persisters by measuring the intensity of their respiratory burst. Materials and Methods. Persistent forms (persisters) of E. coli were obtained by sequential incubation of bacteria in solutions of 3-chlorophenylhydrazone carbonyl cyanide ( CCCP) and ciprofloxacin. Differentiated cells of the HL-60 line (ATCC CCL-240) were used as neutrophil-like cells. The reactive respiratory burst of neutrophil-like cells in response to native E. coli or E. coli persisters was evaluated by measuring fluorescence of the oxidized form of Amplex Red using an Infinite M200 microplate reader. Results. The number of viable E. coli before and after incubation with the CCCP and ciprofloxacin was approximately the same, thus confirming the presence of persistent forms of E. coli. Native E. coli cells caused a statistically significant increase in respiratory burst of neutrophil-like cells reaching 14 +/- 4% of the positive control values (in the negative control, the values were 6 +/- 3%). The respiratory burst intensity of neutrophil-like cells mixed with E. coli persisters was significantly higher than that observed with native E. coli, and accounted for 42 +/- 7% of the positive control. Conclusion. Persists of E. coli can stimulate the respiratory metabolism of phagocytic neutrophil-like cells of the HL-60 line. The ability of these persisters to induce a respiratory burst of neutrophils is significantly greater than that of native E. coli bacteria.