Roles of divalent cations and pH in mechanism of action of nitroxoline against Escherichia coli strains

Abstract

The antibacterial activity of nitroxoline (NIT), an antibiotic used in the treatment of acute or recurrent urinary tract infections caused by Escherichia coli, is decreased in the presence of Mg 2؉ and Mn 2؉ but not Ca 2؉ . In order to elucidate the interaction between this drug and the divalent cations, spectrophotometric studies based on the natural absorption of the nitroxoline moiety were conducted. In the presence of the divalent metal ions, a shift in the NIT A 448 suggested the formation of drug-ion complexes, for which the stability followed the order Mn 2؉ > Mg 2؉ > Ca 2؉. A clear correlation was found between the chelating property and antibacterial activity of NIT; both were pH dependent. A convenient colorimetric method for the determination of NIT uptake by bacterial cells was also developed. Uptake was energy independent and showed biphasic kinetics: a rapid association with cells and then a slower increase in cell-associated NIT which reached a plateau. NIT uptake was reduced in the presence of magnesium. The implications of metal ion complexation and pH on the clinical efficacy of NIT are discussed.Nitroxoline (NIT), or 5-nitro-8-hydroxyquinoline, is an antibiotic which does not belong to any known antimicrobial class. This drug is used in France in the treatment of acute or recurrent urinary tract infections (UTIs) (14, 26) since it shows bacteriostatic activity against Escherichia coli strains frequently encountered in UTIs. On the other hand, the pharmacokinetics of NIT in plasma and urine are well established (4). NIT also possesses fungistatic activity (11) and bactericidal properties against Mycoplasma spp. (7).Recent studies have shown an inhibition of adherence of uropathogenic E. coli to uroepithelial cells (27) and urinary catheters (8) at sub-MICs of NIT. In order to explain this activity Bourlioux et al. (9) proposed that NIT promotes a disorganization of the bacterial outer membrane resulting from the chelation by NIT of the divalent ions Mg 2ϩ and Ca 2ϩ . The same investigators observed a decrease in the antibacterial activity of NIT on E. coli in the presence of some divalent metal ions (9). It is interesting to note that 8-hydroxyquinoline (oxine) and its derivatives have been reported to complex with metal ions (23, 37).To acquire further information on the mechanism of action of NIT and the behavior of the molecule toward the bacterial envelope, the interaction between NIT and some divalent metal ions was spectrophotometrically examined by using the absorption properties of the molecule in the visible region. In addition, microbiological investigations were carried out to determine the role of these ions and the pH in the antibacterial activity of NIT. The uptake of NIT by E. coli was also studied. MATERIALS AND METHODSBacterial strains and culture conditions. Three strains of E. coli were studied. Strains J96 and AL46 were isolated from patients with UTIs. J96 is a standard strain, frequently used in bacterial adherence assays, expressing type 1 and P fimbriae (24); the AL...

Urinary Concentrations and Antibacterial Activities of Nitroxoline at 250 Milligrams versus Trimethoprim at 200 Milligrams against Uropathogens in Healthy Volunteers

“…A higher AUBT 24 in acidic urine for NTX was demonstrated only for E. coli ATCC 25922. The finding of more-pronounced antibacterial activity in an acidic environment for NTX was also shown in other investigations (18). Therefore, there should be a call for pH measurement if NTX is to be employed, or an acidifying agent may be added to NTX treatment to improve antibacterial activity.…”

“…Its antimicrobial efficacy is based on its ability to chelate divalent cations (18). Although it has been in clinical use for many years, no increase in resistance has been observed for Escherichia coli, the most frequent uropathogen (19).…”

The Urinary Antibiotic 5-Nitro-8-Hydroxyquinoline (Nitroxoline) Reduces the Formation and Induces the Dispersal of Pseudomonas aeruginosa Biofilms by Chelation of Iron and Zinc

“…Currently, attempts are under way to identify therapeutically applicable compounds that would show strong chelating properties without concomitant immunogenicity or toxicity (1,18,19). The antimicrobial effects of the urinary antibiotic nitroxoline have long been known to depend on its ability to chelate bivalent and trivalent cations (9,20). We thus examined the influence of nitroxoline on biofilm formation by the well-established laboratory model strain PAO1 and by three clinical P. aeruginosa aeruginosa isolates from different sources (see Table 1 for a description of strains).…”

Substituted oxines inhibit endothelial cell proliferation and angiogenesis

“…Nitroxoline is known to form a chelate with Mn 2+ (21 μM 5 + 10 mM MnCl 2 was used in this study; bathochromic and hypsochromic shifts were seen, λ max = 448 nm shifted to 430 nm), 24 and we also observed a measurable shift even at 10 μM (both 5 and MnCl 2 ). However, under the same conditions CoCl 2 caused a huge hypochromicity coupled with a bathochromic shift (450 nm to 435 nm).…”

“…The metal chelation property is thought to be the underlying cause for the bioactivity of cloxyquin and clioquinol, and it has been shown that nitroxoline shares that feature to manifest its antibacterial activity. 24 Herein, we report the structure–activity relationship (SAR) studies of the two oxines we identified as hits in the HTS by obtaining and evaluating different analogs through either purchasing from commercial source or synthesizing in-house. We characterized each analog in HUVEC proliferation assay using [ 3 H]-thymidine incorporation, and enzymatic assays with MetAP1 and MetAP2.…”