Bioactivity of Isostructural Hydrogen Bonding Frameworks Built from Pipemidic Acid Metal Complexes

We report herein three novel complexes whose design was based on the approach that consists of combining commercially available antibiotics with metals to attain different physicochemical properties and promote antimicrobial activity. Thus, new isostructural three-dimensional (3D) hydrogen bonding frameworks of pipemidic acid with manganese (II), zinc (II) and calcium (II) have been synthesised by mechanochemistry and are stable under shelf conditions. Notably, the antimicrobial activity of the compounds is maintained or even increased; in particular, the activity of the complexes is augmented against Escherichia coli, a representative of Gram-negative bacteria that have emerged as a major concern in drug resistance. Moreover, the synthesised compounds display similar general toxicity (Artemia salina model) levels to the original antibiotic, pipemidic acid. The increased antibacterial activity of the synthesised compounds, together with their appropriate toxicity levels, are promising outcomes.

A New Approach for Improving the Antibacterial and Tumor Cytotoxic Activities of Pipemidic Acid by Including It in Trimethyl-β-cyclodextrin

Pipemidic acid (HPPA) is a quinolone antibacterial agent used mostly to treat gram-negative infections of the urinary tract, but its therapeutic use is limited because of its low solubility. Thus, to improve drug solubility, natural cyclodextrins (CDs) are used for their ability of including guest molecules within their cavities. The aim of this work was to evaluate the antibacterial activity and the preliminary anticancer activity of HPPA included into Heptakis (2,3,6-tri-O-methyl)-β-cyclodextrin (TRIMEB) as a possible approach for a new innovative formulation. The inclusion complex of HPPA with TRIMEB was prepared in solid state by the kneading method and confirmed by FT-IR and powered X-ray diffraction. The association in aqueous solutions of pipemidic acid with TRIMEB was investigated by UV-Vis spectroscopy. Job's plots have been drawn by UV-visible spectroscopy to confirm the 1:1 stoichiometry of the host⁻guest assembly. The antibacterial activity of HPPA, TRIMEB and of their complex was tested on Escherichia coli, Pseudomonas aeruginosa, and Staphilococcus aureus. The complex was able to increase 47.36% of the median antibacterial activity of the free HPPA against E. coli (IC50 = 249 µM vs. 473 µM). Furthermore, these samples were tested on HepG-2 and MCF-7. After 72 h, the median tumoral cytotoxicity exerted by the complex was increased by 78.08% and 94.27% for HepG-2 and MCF-7 respectively, showing a stronger bioactivity of the complex than the single HAPPA.

Synthesis and in vitro antimicrobial activity screening of new pipemidic acid derivatives

This article describes the synthesis and antimicrobial activity evaluation of new pipemidic acid derivatives. New compounds were obtained on the basis of Mannich reaction of 4,5-disubstituted 1,2,4-triazole-3-thiones with pipemidic acid. Antimicrobial tests revealed high antibacterial activity of obtained derivatives. Gram-negative rods belonging to Enterobacteriaceae family were particularly most sensitive to new pipemidic acid derivatives. Synthesized compounds exhibited very strong activity towards Proteus mirabilis ATCC 12453, Salmonella typhimurium ATCC 14028 and Escherichia coli ATCC 25922. The minimum inhibitory concentrations of new pipemidic acid derivatives which inhibited the growth of these bacteria were 0.98-7.81 µg/ml, 0.98-7.81 µg/ml and 0.98-3.91 µg/ml, respectively. The antibacterial activity of newly synthesized pipemidic acid derivatives in many cases was far better than the activity of substances used as positive controls (nitrofurantoin, cefuroxime, ampicillin and pipemidic acid).

T cell-mediated hypersensitivity to quinolones: mechanisms and cross-reactivity

BACKGROUND

Quinolones are widely used, broad spectrum antibiotics that can induce immediate- and delayed-type hypersensitivity reactions, presumably either IgE or T cell mediated, in about 2-3% of treated patients.

OBJECTIVE

To better understand how T cells interact with quinolones, we analysed six patients with delayed hypersensitivity reactions to ciprofloxacin (CPFX), norfloxacin (NRFX) or moxifloxacin (MXFX).

METHODS

We confirmed the involvement of T cells in vivo by patch test and in vitro by means of the lymphocyte proliferation test (LTT). The nature of the drug-T cell interaction as well as the cross-reactivity with other quinolones were investigated through the generation and analysis (flow cytometry and proliferation assays) of quinolone-specific T cell clones (TCC).

RESULTS

The LTT confirmed the involvement of T cells because peripheral blood mononuclear cells (PBMC) mounted an enhanced in vitro proliferative response to CPFX and/or NRFX or MXFX in all patients. Patch tests were positive after 24 and 48 h in three out of the six patients. From two patients, CPFX- and MXFX-specific CD4(+)/CD8(+) T cell receptor (TCR) alphabeta(+) TCC were generated to investigate the nature of the drug-T cell interaction as well as the cross-reactivity with other quinolones. The use of eight different quinolones as antigens (Ag) revealed three patterns of cross-reactivity: clones exclusively reacting with the eliciting drug, clones with a limited cross-reactivity and clones showing a broad cross-reactivity. The TCC recognized quinolones directly without need of processing and without covalent association with the major histocompatability complex (MHC)-peptide complex, as glutaraldehyde-fixed Ag-presenting cells (APC) could present the drug and washing quinolone-pulsed APC removed the drug, abrogating the reactivity of quinolone-specific TCC.

CONCLUSION

Our data show that T cells are involved in delayed immune reactions to quinolones and that cross-reactivity among the different quinolones is frequent.

[Study on the molecular mechanism of quinolone resistance in Shigellae spp]

OBJECTIVE

To study the resistance and its mechanism of Shigellae spp. to quinolones.

METHODS

Seventy-three clinical isolates were collected. Susceptibility tests of pipemidic adcid (PI), ofloxacin (OFL), norfloxacin (NOR), and ciprofloxacin (CIP) were performed in all clinical isolates and Shigella 51573. The N-terminal coding region of gyrA and parC were amplified by polymerase chain reaction (PCR) respectively. Restriction fragment length polymorphism (RFLP) was applied to all PCR procucts of gyrA and parC, and single strand conformational polymorphism analysis (SSCP) was also applied to PCR procucts of parC.

RESULTS

The resistance rates for all the Shigella spp. to PI, CIP, NOR and OFL were 79.5%, 60.3%, 41.1% and 36.9%. Sixty-seven strains (91.8%) were quinolone-reduced-sensitive isolates, in which 61 strains (91%) were found carrying mutations in gyrA with 5 strains (7.5%) found carrying mutations in parC. No mutation was found in 6 quinolone-sensitive isolates or Shigella 51573.

CONCLUSION

The Shigella spp. had high resistance rates to quinolones. The target gene mutations which were mainly found in gyrA and secondarily in parC, played an important role in the quinolone-resistance in Shigella spp.

Structural features of piperazinyl-linked ciprofloxacin dimers required for activity against drug-resistant strains of Staphylococcus aureus

We previously demonstrated that piperazinyl-linked fluoroquinolone dimers possess potent antibacterial activity against drug-resistant strains of Staphylococcus aureus. In this study, we report the preparation and evaluation of a series of incomplete dimers toward ascertaining structural features of piperazinyl-linked ciprofloxacin dimers that render these agents refractory to fluoroquinolone-resistance mechanisms in Staphylococcus aureus.

Synthesis, characterization, and antibacterial activities of some rare Earth metal complexes of pipemidic acid

Eight new solid complexes of pipemidic acid (PPA) with trichlorizated rare earth metals LaCl(3), CeCl(3), PrCl(3), NdCl(3), SmCl(3), TbCl(3), DyCl(3), and YCl(3) have been synthesized. The complexes were characterized by elemental analyses, IR, NMR, and molar conductance measurements. The general formulas of the complexes are [M(PPA)(4)]Cl(3) (M=Ce(III), Pr(III), Nd(III), Sm(III), Tb(III), Dy(III), Y(III)), and [La(PPA)(4)Cl]Cl(2). At the same time, the antibacterial activities of PPA and four of its complexes were tested. The results show that PPA and its complexes all have inhibitory action against bacteria of Escherichia coli, Bacillus subtilis, Streptococcus pneumoniae, and Pseudomonas aeruginosa but not Staphylococcus aureus. We compared their antibacterial activities and found that the antibacterial activity of [La(PPA)(4)Cl]Cl(2) against S. pneumoniae is much stronger than that of PPA and the other complexes.

[Quinolone-resistant Escherichia coli in the health area of a 650-bed hospital]

Report of a retrospective study to evaluate susceptibility of Escherichia coli to quinolones covering the March-December 1992 interval. During this time, intra and extra-hospital strains were indistinctly studied in patients with urinary infections seen in a health district serving a total of 200.000 inhabitants. Resistance to Pipemidic acid, Norfloxacin and Ciprofloxacin was evaluated. The values found were 14.8% resistance to Pipemidic acid, 11.1% to Norfloxacin and 8.5% to Ciprofloxacin. It seems necessary to develop and apply methods addressed to minimize the appearance of quinolone resistance, which should be implemented in order to preserve the usefulness of these drugs.

Biotransformation of methylxanthines in mammalian cell lines genetically engineered for expression of single cytochrome P450 isoforms. Allocation of metabolic pathways to isoforms and inhibitory effects of quinolones

V79 Chinese hamster cells genetically engineered for stable expression of single forms of rat cytochromes P450IA1, P450IA2, P450IIB1, human P450IA2, and rat liver epithelial cells expressing murine P450IA2 were used to allocate metabolic pathways of methylxanthines to specific isoforms and to test the suitability of such cell lines for investigations on drug interactions occurring at the cytochrome expressed. The cell lines were exposed to caffeine and/or theophylline and concentrations of metabolites formed in the medium were determined by HPLC. Caffeine was metabolized by human, rat and murine P450IA2, resulting in the formation of four primary demethylated and hydroxylated metabolites. However, there were differences in the relative amounts of the metabolites. The human and the mouse P450IA2 isoforms predominantly mediated 3-demethylation of caffeine. The rat cytochrome P450IA2 mediated both 3-demethylation and 1-demethylation of caffeine to a similar extent. The results support the hypothesis that caffeine plasma clearance is a specific in vivo probe for determining human P450IA2 activity. Addition of the quinolone antibiotic agents pipemidic acid or pefloxacin, both known to inhibit caffeine metabolism in vivo and in human liver microsomes, reduced formation rates of all metabolites of caffeine in cells expressing rat and human P450IA2. Theophylline was mainly metabolized via 8-hydroxylation. All cell lines tested were able to carry out this reaction, with highest activities in cell lines expressing rat or human P450IA2, or rat P450IA1.

Ten-year survey of quinolone resistance in Escherichia coli causing urinary tract infections

In a ten-year survey (1983-1992) of quinolone resistance in Escherichia coli causing urinary tract infections in a general practice patient population, 9,934 strains were tested. Resistance increased remarkably from 1989 onwards. The rate of resistance to pipemidic acid was < or = 6% before 1989 and 18% in 1992; the rate of resistance to ciprofloxacin (MIC > or = 4 mg/l) was 0.8% in 1989 and 7.1% in 1992. Although the consumption of older quinolones decreased the total consumption of quinolones increased yearly.

Pyrimidines as the chemotherapeutic drugs

Investigations on new chemotherapeutic drugs have attracted a worldwide interest during the past few years. The pyrimidine derivatives possessing such the activity have a considerable pharmaceutical significance. The works on these compounds are led in various directions, but a particular importance have modifications of the drug Trimetoprime as well as syntheses of new pipemidic acid derivatives and pyrimidines with the amide group.

Effects of quinolone carboxylic acid derivatives on GABAA receptor-mediated stimulation of gastric acid secretion and intestinal motility

The present study investigates the effects of some quinolone carboxylic acid derivatives on GABAA receptor-mediated excitatory responses in gastrointestinal preparations in vivo and in vitro. In stomach-perfused rats, norfloxacin, nalidixic and pipemidic acid dose dependently antagonized acid hypersecretion induced by muscimol. Under the same conditions, the quinolone derivatives failed to modify acid hypersecretion evoked by 2-deoxy-D-glucose. In the isolated guinea-pig ileum, norfloxacin, nalidixic and pipemidic acid antagonized muscimol-elicited contractions in a non-competitive manner. In contrast, these drugs did not influence ileal cholinergic contractions evoked by transmural electrical stimulation or by exogenous acetylcholine. Taken together, these results suggest that the quinolone derivatives tested act as antagonists at both central and peripheral GABAA receptors. In addition, GABAA-mediated gastrointestinal responses might represent a simple and reliable method to assay the GABAA receptor antagonist properties of new quinolone derivatives.

Pharmacokinetic determination of relative potency of quinolone inhibition of caffeine disposition

Quinolone is reported to interact with caffeine, often resulting in an increase both in the plasma half-life and AUC, a decrease in total plasma clearance, and little change in the absorption rate constant and maximum plasma level. These complex changes in the pharmacokinetics of caffeine were analyzed experimentally and from published reports in order to determine the nature of the interaction, which is thought to be due to inhibition of caffeine metabolism by quinolones. A simple pharmacokinetic model for the caffeine-quinolone interaction was developed, which provides a unified method for evaluation and comparison of the effect of quinolones on the disposition of caffeine. The model is applicable to other methylxanthines, such as theophylline. The relative potency of the interactions of quinolones with caffeine in humans has been established as enoxacin (100), pipemidic acid (29), ciprofloxacin (11), norfloxacin (9) and ofloxacin (0).

Reversible suppression by nalidixic acid of anchorage-independent growth of mouse cells transformed by 3-methylcholanthrene or an activated c-Ha-ras gene

Effects of nalidixic acid and its derivatives were investigated on mouse cells transformed by methylcholanthrene or an activated c-Ha-ras oncogene. Our findings were as follows. Nalidixic acid preferentially suppressed growth in soft agar of transformed Balb/3T3 mouse cells induced by methylcholanthrene. The suppressive effect of nalidixic acid on growth in soft agar was reversible. Nalidixic acid reversibly reduced saturation density of these transformed cells. Oxolinic acid and pipemidic acid, which are derivatives of nalidixic acid, were less effective than nalidixic acid in suppressing growth in soft agar. Nalidixic acid suppressed growth in soft agar of NIH/3T3 mouse cells transformed by an activated c-Ha-ras, without affecting the amount of ras p21 proteins as detected by an immunoblotting analysis using a monoclonal antibody. These results show that nalidixic acid reversibly suppressed the expression of transformed phenotypes that were already being expressed.

Interaction of quinolones with the theophylline metabolism in man: investigations with lomefloxacin and pipemidic acid

The single-dose pharmacokinetics of theophylline alone and at the end of a five-day treatment period with a new difluorinated quinolone antibacterial, lomefloxacin (400 mg/d) and pipemidic acid (400 mg b.i.d.) were investigated in 12 healthy male volunteers. Concentration of theophylline and its metabolites 1-methylxanthine, 1-methyluric acid, 1.3-dimethyluric acid and 3-methylxanthine were determined in plasma, and (except 1-methyluric acid) in urine by HPLC separation. The elimination half-life of theophylline before quinolone treatment was 5.7 +/- 2.0 h and did not change significantly under coadministration of lomefloxacin (6.2 +/- 2.0 h), whereas with pipemidic acid a marked prolongation (10.8 +/- 2.3 h) occurred. Results without and during coadministration of lomefloxacin showed no detectable 1-methylxanthine in plasma. With pipemidic acid, 1-methylxanthine was observed in the plasma and 1-methyluric acid and 3-methylxanthine were not detected. Lomefloxacin showed only a slight alteration in the metabolite formation of theophylline, whereas pipemidic acid induced marked changes. In contrast to pipemidic acid, no metabolic interaction would be expected under concomitant use of lomefloxacin and theophylline within the recommended dose range for both drugs.

The bactericidal effect on Pseudomonas strains of adriamycin associated with quinolones

The in vitro antibacterial activity of quinolone compounds was assessed on strains of Pseudomonas aeruginosa isolated from clinical infections. The bactericidal effect of quinolones was high and their respective antibacterial properties with adriamycin remained unimpaired on strains both sensitive and resistant to betalactam and aminoglycoside antibiotics. The cytotoxic effect of the combination of adriamycin and quinolones was determined in cultured P388 leukemia cells: no interference with the cytotoxic activity of adriamycin was observed.

Effect of quinolones on caffeine disposition

Six healthy volunteers received a single caffeine dose after pretreatment with norfloxacin, pipemidic acid, or placebo in a crossover, randomized, single-blind clinical trial. Quinolones altered the pharmacokinetics of caffeine, with a significant increase in the AUCs and a decrease in plasma clearance. The elimination half-life increased significantly with pipemidic acid. The apparent volume of distribution, mean renal clearance, and time to reach maximum caffeine concentrations remained unaltered. There was a decline in caffeine metabolite levels in the 24-hour urine samples for both quinolone treatments, suggesting that pipemidic acid and, to a lesser degree, norfloxacin inhibit metabolism of the N-demethylation pathways of caffeine. The practical consequence of this observation could be caffeine accumulation during repeated intake of coffee. In two additional healthy volunteers under a controlled multiple-dose regimen of caffeine ingestion, administration of pipemidic acid for 2 days caused a fourfold increase in the plasma concentrations of caffeine.

In vitro activity of pefloxacin compared with five other quinolones on nalidixic acid-resistant proteae species

The in vitro activity of pefloxacin, a new fluoroquinolone, was compared with that of 5 other quinolone compounds (nalidixic and pipemidic acids, norfloxacin, ciprofloxacin, and ofloxacin) against 416 strains of Proteae spp. isolated from urine specimens of hospitalized patients with acute urinary tract infections (UTI). Ciprofloxacin was the most active agent. Norfloxacin, ofloxacin, and pefloxacin were similarly active against Proteus strains (MIC90 = 0.39 microgram/ml). Against Providencia spp. pefloxacin and norfloxacin showed similar activity (MIC90 = 3.12 micrograms/ml). There is minimal discrepancy between minimum inhibitory concentrations and minimum bactericidal concentrations exhibited by the quinolones for all urinary tract pathogens tested. Our in vitro studies indicate that pefloxacin is an active antimicrobial agent and suggest that it will prove useful in the treatment of complicated urinary tract infections due to nalidixic acid-resistant Proteae spp.

[Corynebacterium group D2. Clinical study, biochemical identification and antibiotic sensitivity]

The comparative study of 44 isolates of Corynebacterium group D2, from urine, most frequently, shows the pathogenic role of these bacteria in urinary tract infection, with or without urinary stones. These microorganisms have an opportunistic behaviour in other non-urinary sites, and become pathogen in immunosuppressed conditions. The rapid tests as urease, glucose acidification, nitrate reductase, associated with multiple resistance to antibiotics (beta-lactams and aminosides) identify easily Corynebacterium group D2, from 48 h cultures under CO2 conditions. The results of MIC determination of 10 antibiotics, show the high activity (100% sensitivity) of vancomycin and pristinamycin, with MIC modes, respectively, 0.5 and 0.03 mg/l. These antibiotics are the most useful for the treatment of non-urinary infections. Among quinolones, the most active agents are ciprofloxacin and ofloxacin (MIC modes: 4 and 2 mg/l), so these antimicrobials could be used for the treatment of urinary tract infections caused by Corynebacterium group D2.

[Evolution from 1976 to 1986 of bacterial prevalence and sensitivity to urinary antibiotics of bacteria isolated from urine cultures at a city microbiology laboratory]

The evolution of the prevalence of the bacterial strains isolated from UTI cases (bacteriuria greater than or equal to 10(5)/ml has been studied over a 11 year-period from 1976 to 1986, in a clinical practice microbiological laboratory from a rural area. E. coli was the overall most frequently isolated species, followed by P. mirabilis (74.4% and 11.2% respectively), by the Klebsiella-Enterobacter group (4.8%), and staphylococci (represented by coagulase negative staphylococci) (4.9%). The relative frequency of the different species has been relatively stable year after year during the considered period. The evolution of the resistance to 4 antibiotics has been studied species by species and year after year for the Gram negative bacilli: a definite evolution towards resistance has been noted for ampicillin until 1985, followed by a decrease in 1986. The same tendency, although less pronounced, has been noted for cotrimoxazole. The frequency of the resistance to nalidixic acid has slightly increased from 1976 to 1986 (1.9% to 6.5%), as well as to pipemidic acid from (0% to 4%). The quinolones stand in 1987 as a good first line treatment of UTI in community, and especially in rural areas, and the role of the clinical practice microbiological laboratory for the epidemiological surveillance has to be stressed.

Antibacterial activity in human urine of fosfomycin trometamol in an in vitro model of the urinary bladder

The urinary concentrations of fosfomycin trometamol, norfloxacin, pipemidic acid and cotrimoxazole were studied at various times after oral administration of drugs in healthy volunteers. Using the same urine, the bactericidal activity of four antimicrobial agents against Escherichia coli, Proteus mirabilis and Klebsiella pneumoniae in an in vitro model simulating the treatment of bacterial cystitis was also evaluated. The results obtained show that very high concentrations of the drugs were achieved in urine particularly after the oral administration of the fosfomycin trometamol. In the bladder model bactericidal activity of fosfomycin trometamol, norfloxacin and pipemidic acid were higher than that of cotrimoxazole; no resistant mutants to drugs were selected over a period of 24 h.

4-quinolones inhibit biotransformation of caffeine

The pharmacokinetics of caffeine, including formation of its major metabolite paraxanthine in plasma, has been investigated in 12 healthy males (age 20-40 years) alone and during co-administration of the 4-quinolones ofloxacin, norfloxacin, pipemidic acid, ciprofloxacin, and enoxacin; ciprofloxacin and enoxacin were given in 3 different dose levels. The naphthyridine derivative enoxacin and the pyrido-pyrimidine derivative pipemidic acid had caused marked inhibition of caffeine and paraxanthine metabolism, whereas the genuine quinolone derivatives norfloxacin and ciprofloxacin had little effect, and the pyrido-benzoxacine derivative ofloxacin had no detectable effect. The different molecular and spatial structures of the compounds appear to be responsible for the differences in inhibitory potency.

New synthetic quinolone antibacterial agents and serum concentration of theophylline

The effect of pipemidic acid and five new synthetic antibacterial agents--norfloxacin, enoxacin, ofloxacin, ciprofloxacin, and pefloxacin--on the serum level of theophylline was studied in healthy male adult volunteers after concomitant oral administration of these agents with a slow release preparation of theophylline. The results indicated that enoxacin, ciprofloxacin, and pipemidic acid might decrease the clearance of theophylline in the liver, and the attention should be paid in clinical use when enoxacin or pipemidic acid is coadministered with theophylline.

In vitro and in vivo activity of NY-198, a new difluorinated quinolone

NY-198 [1-ethyl-6,8-difluoro-1,4-dihydro-7-(3-methyl-1-piperazinyl)-4-oxo-3- quinolinecarboxylic acid hydrochloride] is a new difluorinated quinolone characterized by the presence of a C-methyl group at the 3 position of the piperazine moiety. It has a broad antibacterial spectrum. The in vitro antibacterial activity of NY-198 was almost the same as those of ofloxacin and norfloxacin, but far exceeded that of pipemidic acid. NY-198 was more active than norfloxacin against Pseudomonas maltophilia, Acinetobacter calcoaceticus, and anaerobic microorganisms. Cross resistance was not observed between NY-198 and various antibiotics including methicillin, gentamicin, and ampicillin. NY-198 had bactericidal activity at the MIC or slightly higher than the MIC. It showed excellent antibacterial activity against various systemic infections in mice. After oral administration, NY-198 was two times more active than or as active as ofloxacin and two to four times more active than norfloxacin.

[Modulation by quinolones of the in vitro proliferative response of splenic cells of the mouse and IL 1 production]

Besides their antibacterial activity, antibiotics can modulate immune response. In this work, we studied the effects of 6 quinolones (nalidixic and pipemidic acid, pefloxacin, norfloxacin, ofloxacin, ciprofloxacin) on Con A or LPS induced mitogenic response in mice. Data presented here show that pefloxacin and ofloxacin enhanced Con A (1 microgram/ml) induced proliferative response when used at low concentrations (0.1 microgram/ml and 1 microgram/ml). In the same conditions LPS induced response was not modified. When used at high concentrations (greater than 25 micrograms/ml), inhibition of both LPS and Con A induced responses was observed. Con A induced response needs interaction between macrophages and T lymphocytes. So, we investigated whether quinolones could act on interleukin 1 (IL 1) production by macrophages. Our results showed that pefloxacin and ofloxacin, used at low concentrations, enhanced LPS induced IL 1 production by macrophages.

[Study of the sensitivity to pipemidic acid, pefloxacin and norfloxacin of 444 bacterial strains isolated at a general hospital]

After one year of use of pefloxacin in the intensive care unit, medicine unit and surgery unit and the following recent commercialization without prescription of norfloxacin, we studied for a period of two months (april and may 1986) the susceptibility to pipemidic acid, to pefloxacin and norfloxacin of 444 bacteria strains isolated obtained from clinical specimens. The antibiotic susceptibility is determined by disk diffusion test. We obtained the following results: susceptible methicillin Staphylococcus aureus (SMSA 63 strains): 85.7% PEFS, 11.1% PEFI, 79.4% NORS, 15.9% NORI, resistant methicillin Staphylococcus aureus (RMSA 36 strains): 33.3% PEFS, 2.9% PEFI, 41.6% NORS, 0% NORI; Escherichia coli, Proteus mirabilis, Klebsiella pneumoniae (252 strains): 94% PIPS, 94.8% PEFS, 97.2% NORS; Enterobacter, Proteus indol (+), Providencia and Citrobacter (33 strains): 72.7% PIPS, 72.7% PEFS, 84.8% NORS; Pseudomonas aeruginosa (53 strains): 32% PEFS, 47.2% PEFI, 90.6% NORS, 5.6% NORI; Acinetobacter (7 strains): 57.2% PEFS, 42.8% PEFI, 42.8% NORS, 28.6% NORI. Norfloxacin in active in vitro against the majority of the P. aeruginosa isolated. We found an important methicillin and pefloxacin resistance among the Staphylococcus aureus isolated: 36 strains RMSA (36.4% out of Staphylococcus aureus) and 23 strains RMSA PEFR (63.8% out of RMSA). These later strains were isolated in eight different units mainly in visceral surgery unit and geriatric units but not in intensive care unit. After an epidemiologic study and the following recommendations to physicians and nurses: treatment by pefloxacin should be used only after bacteriological results and associated with an other antibiotic, the handwashing should be frequent and regular to prevent the spread of infection, four months later we isolated 26 strains of RMSA with 7 RMSA PEF (26.9%).2$

Ability of ciprofloxacin but not pipemidic acid to differentiate all three biovariants of Mycobacterium fortuitum from Mycobacterium chelonae

When tested against 312 clinical isolates of rapidly growing mycobacteria, the quinolone pipemidic acid correctly separated Mycobacterium chelonae (M. chelonei) from Mycobacterium fortuitum biovar fortuitum but not from biovar peregrinum or the third biovar complex. The new 4-quinolone ciprofloxacin correctly separated all three biovars of M. fortuitum from M. chelonae and appears to provide a better taxonomic test.

Microbiological basis for the use of fosfomycin trometamol as single-dose therapy for simple cystitis

Fosfomycin trometamol (FOT), a new soluble salt of fosfomycin, was developed especially for single-dose treatment in uncomplicated urinary tract infections. In this study, the minimum inhibitory concentrations (MICs) of FOT were measured both in nutrient broth and human urine and compared with calcium fosfomycin, pipemidic acid and cotrimoxazole. A total of 300 bacterial strains of different species from recent urinary infections were studied. Staphylococcus aureus showed the lowest MIC (0.38 micrograms/ml) and Pseudomonas spp. the highest (50 micrograms/ml) with fosfomycin salts in nutrient broth. The MIC of fosfomycin resulted in being higher than those for pipemidic acid and cotrimoxazole against Escherichia coli and Proteus rettgeri and lower for all the other species considered. The MIC values increased about ten times when urine was used as medium. No differences were observed between the two fosfomycin salts. The fosfomycin concentrations of 137-1500 micrograms/ml, easily obtained in urine of healthy adult subjects after a single dose of FOT (3g of fosfomycin), were able to kill all the strains, with the exception of Streptococcus faecalis. The bacterial adhesion of a resistant microorganism (P. aeruginosa) to the cells of the urinary tract, showed a 50% reduction after FOT treatment.

Influence of ofloxacin, norfloxacin, nalidixic acid, pyromidic acid and pipemidic acid on human gamma-interferon production and blastogenesis

Several new quinolone derivatives were investigated for their influence on human lymphocyte blastogenesis and gamma-interferon production following concanavalin A stimulation. All the antimicrobials induced inhibition of lymphocyte DNA synthesis. The gamma-interferon measurements showed that nalidixic acid and norfloxacin have a negative influence on lymphokine production and release.

[In vitro activity of new quinolones against nonfermenters and references to sensitivity tests]

Studies of cross resistance between norfloxacin, ofloxacin, enoxacin and ciprofloxacin using 599 strains of non-fermentative gram-negative rods (297 Pseudomonas spp. and 302 Acinetobacter spp.) resulted in nearly identical minimal inhibitory concentrations of norfloxacin and enoxacin Comparing MIC values, in most ofloxacin was one to four dilution steps superior to enoxacin, and ciprofloxacin was one to four dilution steps superior to ofloxacin. There was not much difference in MICs when species were studied in more detail. In some instances susceptibility testing with more than one new quinolone may be necessary, and evaluation criteria are given.

Norfloxacin versus pipemidic acid in complicated urinary tract infections due to susceptible pathogens: a comparative clinical trial

Norfloxacin (NOR) was compared to pipemidic acid (PA) in complicated urinary tract infections (UTIs) caused by pathogens susceptible to both agents to evaluate the antibacterial activity of the new 4-quinolone derivative. Sixty-five patients were randomly allocated to receive NOR or PA, 400 mg bid for 7 days, and the results evaluated for treatment efficacy at 5 weeks after completion of therapy. Overall microbiological cure was significantly greater in NOR-treated patients, as 19 of 26 were cured (73%), compared to only 16 of 39 (41%) in the PA group (p less than 0.05). Failures and relapses, considered together, were significantly (p less than 0.05) less frequent in patients treated with NOR (4/26) than in those receiving PA (18/39). Clinical response was strictly related to microbiological outcome: NOR had a broader antibacterial spectrum than PA and in this study seemed to be more efficacious in the treatment of complicated UTIs caused only by bacteria susceptible to both agents. This may be related to greater antibacterial activity and/or tissue penetration by NOR, which is thus to be preferred, according to the results of our study, in the treatment of complicated UTIs.

[Synergism of ciprofloxacin with beta-lactam antibiotics, gentamicin, minocycline and pipemidic acid]

Studies on the Synergism of Ciprofloxacin with beta-Lactam Antibiotics, Gentamicin, Minocycline and Pipemidic Acid. Using Escherichia coli, Klebsiella pneumoniae/Klebsiella oxytoca, Pseudomonas aeruginosa and Staphylococcus aureus strains, we examined a possible influence of pipemidic acid, minocycline, gentamicin, cefazolin, mezlocillin and ampicillin on the antibiotic activity of ciprofloxacin. We found in all bacterial species synergistic influence by pipemidic acid. When ciprofloxacin was combined with gentamicin, synergism was observed in E. coli and in K. pneumoniae/oxytoca, additive effects in P. aeruginosa and S. aureus. In combination with minocycline we demonstrated synergism in S. aureus only. In all other bacterial species and antibiotic combinations we found neither synergism nor antagonism.

[In vitro comparative activity of norfloxacin in the comparison of pathogenic bacteria of the urinary tract]

In this study 411 bacterial isolates from clinical urinary tract infections against some quinolones, azthreonam and trimethoprim + sulfamethoxazole combination were tested. Bactericidal kinetics of norfloxacin , cinoxacin and azthreonam against E. coli ATCC 25922 was determined. Both MICs values and bactericidal activities have shown that fluoroquinolones are more active against all Gram-positive and Gram-negative bacteria tested than the other drugs.

Ofloxacin: antibacterial activity, induction of resistance and killing curves

The antibacterial activity of ofloxacin was compared to that of nalidixic acid, norfloxacin and against various strains. This new quinolone was about 100 times more active than nalidixic acid, and pipemidic acid and generally 2 to 4 fold more active than norfloxacin and pefloxacin except against Pseudomonas aeruginosa. The increase of resistance to ofloxacin, norfloxacin and pefloxacin seems to plateau, usually at about 16 times the initial MIC. The bactericidal activity of ofloxacin also appeared quickly and more rapidly than that of norfloxacin.

[Comparative activity of norfloxacin and other chemotherapeutic agents on the adhesion of bacteria of the uro-vaginal tract to uroepithelial cells]

A number of bacterial strains (Escherichia coli, Proteus mirabilis and streptococci), obtained from patients with urinary infections, or from vaginal tampons, were assayed in order to evaluate their ability to adhere to uroepithelial cells. We employed, at a comparative purpose, two different methods to eliminate unattached bacteria: the centrifugation technique and the filtration technique. The effect of the pretreatment with subinhibitory concentrations of three chemotherapeutics widely employed in the urological practice (norfloxacin, pipemidic acid and co-trimoxazole) was determined on the strains which demonstrated a good rate of attachment. Growth in the presence of any of the three drugs decreased the adhesive properties of the microorganisms, reducing both the haemagglutination and the yeast aggregation titers of Gram-negative bacteria as well as their adhesiveness. Norfloxacin proved to be the most effective drug in affecting the pathogenicity characteristics of the assayed strains in comparison with the other two chemotherapeutics tested, even if they were also moderately able to inhibit the adhesiveness of the same strains.

Occurrence of gram negative bacteria in midstream bladder urine and their sensitivity to quinoline derivatives

326 gram negative bacteria have been isolated and quantitative bacteria counts performed from midstream urine of as many patients affected with symptomatic and non symptomatic urinary tract infections. Susceptibility of bacteria to four quinoline derivatives (Norfloxacin, Oxolinic acid, Pipemidic acid and Nalidixic acid) was studied determining the minimal inhibitory concentrations (MICs) of each drug by a miniaturized dilution broth method. The frequency of bacterial species isolated, the frequency of symptoms and the frequency of bacterial counts were studied to establish a possible relationship between these data. It has been observed that patients affected with pyuria without any other subjective symptoms demonstrate a colony count ranging between less than 10(4) and greater than 10(5) bacterial/ml of urine and these bacteriuria were determined by several different bacterial species. E. coli was much more frequently responsible for low or high count bacterial infections of the urinary tract than other species. In fact E. coli was detected in 64.4% of patients, P. mirabilis in 15.9%, E. agglomerans in 5.2%, P. aeruginosa in 4.9. Other species were detected in much lower percentages. Norfloxacin proved to be the most effective drug in vitro, out of those under examination. Its MIC50 never exceeded 8 mcg/ml even against Pseudomonas and Serratia strains, which were resistant to all the other antimicrobial agents.

[Evaluation of the in vitro activity of enoxacin on bacterial strains recently isolated in a hospital milieu]

The in vitro activity of enoxacin, a new quinolone derivative, was tested against 2180 bacterial strains, recently clinically isolated, by measuring the minimum inhibitory concentrations. Comparisons were made with other drugs (flumequine, oxolinic acid, pipemidic acid) widely utilized for the treatment of urinary tract infections. Enoxacin showed the highest activity against all the tested strains, with a geometrical mean of MICs (MG) of 0.39 micrograms/ml and a MIC 50 and MIC 90 of 0.25 and 4 micrograms/ml, respectively.

In vitro activity of the newer quinolones compared with the classic ones and tobramycin

The halogenated substitution of quinolone derivatives has given rise to a new group of substances called newer quinolones, which possess extraordinary antibacterial activity in vitro. The aim of our study was to compare the effect of the newer quinolones ciprofloxacin (CIP), norfloxacin (NOR) and enoxacin (ENO) with that of the classical ones nalidixic acid (NA), oxolinic acid (OX) and pipemidic acid (PIP) and with a widely-used aminoglycoside tobramycin (TBR). This was tested on 2,263 strains from clinical isolations. Evaluating the effect of the least active substances as a unit, we generally found the MIC90s to be of the following order: (Formula: see text). The remaining groups among the antibiotics studied are ordered identically, the most potent being the newer quinolones in the following order: CIP is at least four times superior to NOR, which in turn is at least twice as effective as ENO for gram-positive organisms, but only 1.2 times for gram-negative bacilli.

[Comparison of the in vitro activity of 6 quinolones on Pseudomonas sp]

Activity of six quinolones (nalidixic acid, pipemidic acid, oxolinic acid, pefloxacin, ofloxacin and norfloxacin) against one-hundred and ten Pseudomonas strains was studied in vitro. Five species of Pseudomonas were represented, i.e. aeruginosa, maltophilia, cepacia, stutzeri and paucimobilis. Isolates came from two Paris hospitals. Minimal inhibitory concentrations (MICs) were determined using gelose dilution according to WHO recommendations (Mueller Hinton medium, multiple inoculator, controlled inoculum). Modal CMIs classify activities of the six tested quinolones against P. aeruginosa in the following order: nalidixic acid: 64 mg/l; pipemidic acid: 16-32 mg/l; oxolinic acid: 16 mg/l; pefloxacin: 2 mg/l; ofloxacin: 2 mg/l; norfloxacin: 1 mg/l. The other Pseudomonas species exhibit a variety of resistance phenotypes which are described in detail. High CMIs are found for certain P. aeruginosa strains. Two of these, i.e. DL 55 and DL 59, are highly resistant to all the tested quinolones. Their pattern of resistance is comparable to that of a mutant, PAO 38-02, obtained in vitro in the presence of pefloxacin. This fact suggests that quinolones may induce in vivo selection of resistant P. aeruginosa mutants.

Cross resistance of quinolone derivatives in gram-negative bacteria

A total of 127 Gram-negative bacteria resistant to nalidixic acid were isolated from as many patients affected by urinary tract infections and hospitalized in the first Clinic of Infectious Diseases, University of Naples. Enterobacteria were identified by Enterotube system (Roche) and API 20 system (Ayerst). Non-fermentative bacteria were identified by OXI/FERM system (Roche). The following bacteria were collected: Escherichia coli 50, Proteus spp. 35, Enterobacter agglomerans 12, Serratia sp. 5, Pseudomonas aeruginosa 25. The in vitro antibacterial activity of nalidixic acid and three other quinoline derivatives (pipemidic acid, oxolinic acid and ciprofloxacin) were studied by determining the MICs by a miniaturized dilution broth method. The MICs were compared to evaluate the eventual cross resistance to the drugs under examination within each bacterial species. The results showed that 23% of bacteria were resistant to nalidixic acid, pipemidic acid and oxolinic acid; 49.6% to nalidixic and pipemidic acid and 0.7% to nalidixic acid and oxolinic acid. On the other hand none of the bacteria were resistant to ciprofloxacin. The last showed very low MICs against all the bacteria under examination, including Pseudomonas and Serratia. The high antibacterial activity of ciprofloxacin even against bacteria highly resistant to the other quinolines could be due to a greater affinity of the target sites or to the better permeability of resistant strains to the newer drug or because it is unaffected until now by mutations of genes responsible for cross resistance.

Incomplete cross-resistance of nalidixic and pipemidic acid-resistant variants of Serratia marcescens against ciprofloxacin, enoxacin, and norfloxacin

Spontaneous and selected variants of Serratia marcescens with resistance against chloramphenicol, cotrimoxazole, nalidixic acid, and pipemidic acid, revealed moderately reduced susceptibility for enoxacin and norfloxacin, and slightly diminished susceptibility for ciprofloxacin. Therefore, urinary tract infections due to S. marcescens strains showing this nonspecific resistance mechanism still might be amenable to judicious chemotherapy with these three novel bacterial DNA gyrase inhibitors, particularly ciprofloxacin.

Intraphagocytic bactericidal activity of bacterial DNA gyrase inhibitors against Serratia marcescens

Addition of phenylbutazone (2 mg/ml) to 55 vol% of fresh defibrinated human blood permitted leukocytic ingestion of Serratia marcescens bacteria, but blocked phagocytic killing activity. The group A (phage tail) bacteriocin bA+ 16 served to kill extraphagocytic test bacteria. Five bacterial DNA gyrase inhibitors (ciprofloxacin, enoxacin, norfloxacin, nalidixic acid and pipemidic acid) revealed intraphagocytic bactericidal activity against ingested S. marcescens bacteria of three test strains; the extent of intraphagocytic activity of these drugs approximated that of rifampin. Following combination with unmodified defibrinated human blood (55 vol%), ciprofloxacin, enoxacin, norfloxacin and pipemidic acid yielded additive effects against 3 assay strains of S. marcescens and Escherichia coli strain ATCC 25922; nalidixic acid was inferior in this regard. These data might guide chemotherapy of parenchymatous urinary tract infections.

In vitro activities of ciprofloxacin, norfloxacin, pipemidic acid, cinoxacin, and nalidixic acid against Chlamydia trachomatis

The in vitro activities of five quinolinecarboxylic acids against two laboratory strains of Chlamydia trachomatis were compared. The minimal inhibitory concentrations of nalidixic acid, cinoxacin, and pipemidic acid were all greater than or equal to 50 micrograms/ml; the activity of norfloxacin was intermediate (minimal inhibitory concentration, 8 to 16 micrograms/ml). Ciprofloxacin was the most active of these drugs (minimal inhibitory concentration, 0.5 to 1 microgram/ml).

Selective decontamination of the digestive tract by pipemidic acid

The possible use of pipemidic acid for preventing infections in granulocytopenic patients by selective elimination of the gram-negative rods from the digestive tract was evaluated. Fecal samples were collected before, during, and after therapy from 23 adults who were undergoing treatment of urinary tract infections with pipemidic acid at a dosage of 200 mg orally four times daily for 10 days. The concentration of pipemidic acid in the majority of the stool samples tested was 220 to 600 micrograms/g. However, in 19% of the samples collected on day 5, the concentration was below the detection limit (23 micrograms/ml). Approximately 90% of the fecal samples collected during or shortly after therapy were negative for members of the family Enterobacteriaceae. Resistance of the gastrointestinal tract against colonization by microorganisms from the environment (so-called colonization resistance) remained unimpaired, as measured by the absence of beta-aspartylglycine in the stool.