Impact of Ciprofloxacin and Chloramphenicol on the Lipid Bilayer of Staphylococcus aureus: Changes in Membrane Potential

Table 1

Parameters obtained from the ANS binding studies in 𝑆.𝑎𝑢𝑟𝑒𝑢𝑠 ATCC 29213 and clinical strain S.  aureus.

	𝐹max	𝐾𝑑	n	Ψ (mV)	ΔΨ (mV)
S. aureus ATCC 29213 sensitive to CIP and CMP
Control without antibiotic	143	251	603028	−306	—
Ciprofloxacin 256 μg/mL	70	927	52983	−406	−100
Chloramphenicol 4 μg/mL	62	846	48332	−331	−25
Clinical strain S. aureus  resistant to CIP
Control without antibiotic	77	902	45110	−287	—
Ciprofloxacin 256 μg/mL	77	937	46865	−302	−15

𝐹_max is the fluorescence intensity (related to the maximum concentration of bound ANS), n is the number of binding sites of ANS to the membrane, 𝐾_𝑑 is the dissociation constant, Ψ is the potential at the surface of the membrane and ΔΨ is the change in surface potential of the membrane in the control without antibiotic.