Effects of changes in pH, medium, and inoculum size on the in vitro activity of amifloxacin against urinary isolates of Staphylococcus saprophyticus and Escherichia coli

Iravani, Abdollah; Welty, G. S.; Newton, Bruce R.; Richard, George A.

doi:10.1128/aac.27.4.449

Cited by 17 publications

(13 citation statements)

References 7 publications

(2 reference statements)

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“…On the other hand, the frequency of spontaneous mutants resistant to amifloxacin was about 10-8/CFU. Amifloxacin is a fluoroquinolone and has a broad spectrum and potent activities that are almost comparable to those of norfloxacin and ofloxacin (1,4,(14)(15)(16).…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

In vitro activity of amifloxacin against outer membrane mutants of the family Enterobacteriaceae and frequency of spontaneous resistance

Watanabe¹,

Inoue²,

Mitsuhashi³

1989

Antimicrob Agents Chemother

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Amifloxacin showed potent inhibitory activity against DNA gyrase of Escherichia coli. The difference in the susceptibilities of lipopolysaccharide-deficient Salmonella typhimurium mutants and their parent strain was less than twofold, and the difference in the susceptibilities of porin-deficient E. coli mutants and their parent strain was less than twofold. There was cross resistance among the quinolone group of agents; however, the decrease in MIC for norB mutants was slightly lower than that of other fluoroquinolones. Cell lysis was induced with combined treatment of amifloxacin and sodium dodecyl sulfate in E. coli. The frequency of mutants spontaneously resistant to amifloxacin was extremely low in all species tested.

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Section: Resultsmentioning

confidence: 99%

“…To investigate the mode of action of the fluoroquinolone amifloxacin (1,14), inhibitory activity against E. coli DNA gyrase, activity against the outer membrane mutants of E. coli and Salmonella typhimurium, and frequency of spontaneous resistance were determined in this study.…”

mentioning

confidence: 99%

In vitro activity of amifloxacin against outer membrane mutants of the family Enterobacteriaceae and frequency of spontaneous resistance

Watanabe¹,

Inoue²,

Mitsuhashi³

1989

Antimicrob Agents Chemother

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“…These observations provided evidence for the relationship between the chelating property, which is a function of pH, and the antibacterial activity of NIT and are in agreement with our earlier hypothesis suggesting that the efficacy of NIT is likely to be associated with its physicochemical property. Ample examples in the literature of antibiotics with a pH-dependent activity (3,25,28,41) and of the combined antagonistic effects of metal ions and pH (6,21) are available. FIG.…”

Section: Discussionmentioning

confidence: 99%

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

Pelletier

Prognon

Bourlioux

1995

Antimicrob Agents Chemother

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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...

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“…For enoxacin, Mueller-Hinton, nutrient, and brain heart infusion media were similar (51, 100). For amifloxacin, up to threefold differences were found comparing Mueller-Hinton, brain heart infusion, thioglycolate, and tryptic soy broths (381 159,192,206,207,216,257,263,273,285,295,297,316,327,331,372,393,405,407,409,415,419,471,497,518,597,646,654,748,754,795,803,804,807,818,821,849,878); ofloxacin (92, 133,149,159,179,285,297,327,393,416,435,524,…”

Section: Factors Affecting Susceptibility and Additional Effects Of Qmentioning

confidence: 99%

Fluoroquinolone antimicrobial agents

1989

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The fluoroquinolones, a new class of potent orally absorbed antimicrobial agents, are reviewed, considering structure, mechanisms of action and resistance, spectrum, variables affecting activity in vitro, pharmacokinetic properties, clinical efficacy, emergence of resistance, and tolerability. The primary bacterial target is the enzyme deoxyribonucleic acid gyrase. Bacterial resistance occurs by chromosomal mutations altering deoxyribonucleic acid gyrase and decreasing drug permeation. The drugs are bactericidal and potent in vitro against members of the family Enterobacteriaceae, Haemophilus spp., and Neisseria spp., have good activity against Pseudomonas aeruginosa and staphylococci, and (with several exceptions) are less potent against streptococci and have fair to poor activity against anaerobic species. Potency in vitro decreases in the presence of low pH, magnesium ions, or urine but is little affected by different media, increased inoculum, or serum. The effects of the drugs in combination with a beta-lactam or aminoglycoside are often additive, occasionally synergistic, and rarely antagonistic. The agents are orally absorbed, require at most twice-daily dosing, and achieve high concentrations in urine, feces, and kidney and good concentrations in lung, bone, prostate, and other tissues. The drugs are efficacious in treatment of a variety of bacterial infections, including uncomplicated and complicated urinary tract infections, bacterial gastroenteritis, and gonorrhea, and show promise for therapy of prostatitis, respiratory tract infections, osteomyelitis, and cutaneous infections, particularly when caused by aerobic gram-negative bacilli. Fluoroquinolones have also proved to be efficacious for prophylaxis against travelers' diarrhea and infection with gram-negative bacilli in neutropenic patients. The drugs are effective in eliminating carriage of Neisseria meningitidis. Patient tolerability appears acceptable, with gastrointestinal or central nervous system toxicities occurring most commonly, but only rarely necessitating discontinuance of therapy. In 17 of 18 prospective, randomized, double-blind comparisons with another agent or placebo, fluoroquinolones were tolerated as well as or better than the comparison regimen. Bacterial resistance has been uncommonly documented but occurs, most notably with P. aeruginosa and Staphylococcus aureus and occasionally other species for which the therapeutic ratio is less favorable. Fluoroquinolones offer an efficacious, well-tolerated, and cost-effective alternative to parenteral therapies of selected infections.

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Effects of changes in pH, medium, and inoculum size on the in vitro activity of amifloxacin against urinary isolates of Staphylococcus saprophyticus and Escherichia coli

Cited by 17 publications

References 7 publications

In vitro activity of amifloxacin against outer membrane mutants of the family Enterobacteriaceae and frequency of spontaneous resistance

In vitro activity of amifloxacin against outer membrane mutants of the family Enterobacteriaceae and frequency of spontaneous resistance

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

Fluoroquinolone antimicrobial agents

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