Fluoroquinolone antimicrobial agents

Effects of ciprofloxacin and enrofloxacin on zoxazolamine kinetics, plasma concentration and sleeping times in mice

The treatment of CD1 male mice with either ciprofloxacin (CP) or enrofloxacin (EF) prior to zoxazolamine (ZX) administration increased the mean ZX sleeping times to, respectively, 162 and 156% of the control (ZX alone). At the end of the sleeping time, the mean ZX plasma concentration in controls was 27.2 micrograms/ml and was not different in EF- or CP-treated groups (87% and 95% of controls, respectively). The animals coadministered with CP or EF and ZX eliminated the latter more slowly than the controls. The estimated zero-time drug concentration of the disposition curves of both the CP- and EF-treated groups as well as the apparent half-life of elimination and apparent overall rate of elimination of the CP-treated group were different from the control values.

Activity of topoisomerase inhibitors against Pneumocystis carinii in vitro and in an inoculated mouse model

Five topoisomerase II inhibitors (amsacrine [m-AMSA], two epipodophyllotoxins, and two quinolones) and the alkaloid camptothecin (a topoisomerase I inhibitor) were evaluated to assess their activities against Pneumocystis carinii. In vitro, both etoposide (VP-16) and teniposide (VM-26) at 1 microgram/ml suppressed P. carinii growth. Amsacrine was toxic to P. carinii and to the feeder cells in vitro. Camptothecin suppressed the growth of P. carinii in vitro only at 100 micrograms/ml. Studies in immunosuppressed mice demonstrated the efficacy of teniposide against P. carinii pneumonia, but successful administration of teniposide was schedule dependent with significant toxicity at therapeutic dosages.

In vitro and in vivo antibacterial activities of E-4868, a new fluoroquinolone with a 7-azetidin ring substituent

E-4868, (-)-7-[3-(R)-amino-2-(S)-methyl-1-azetidinyl]-1-(2,4- difluorophenyl)-1,4-dihydro-6-fluoro-4-oxo-3-quinolinecarboxylic acid, is a new fluoroquinolone with an azetidine moiety at the 7 position. The in vitro activity of E-4868 has been compared with those of ciprofloxacin, ofloxacin, and fleroxacin, while the activity of ciprofloxacin was used as reference for in vivo studies. The MICs of E-4868 for 90% of the isolates tested (MIC90s) were 0.06 to 0.5 microgram/ml against gram-positive organisms, including Staphylococcus, Streptococcus, and Enterococcus spp. In general, the in vitro potency of E-4868 against gram-positive bacteria was higher than those of all of the other fluoroquinolones tested. MIC90s against members of the family Enterobacteriaceae between 0.03 and 1 microgram/ml were observed, with the exception of those against Serratia marcescens and Providencia spp., and a MIC90 of 2 micrograms/ml against Pseudomonas aeruginosa was obtained. E-4868 inhibited 90% of the Clostridium spp. and Bacteroides spp. at 2 micrograms/ml and was twofold more active than ciprofloxacin. An increase in the Mg2+ concentration from 1 to 10 mM increased the MIC between two and three times. Human urine caused a significant decrease in activity of E-4868, which was more pronounced at pH 5.5 than at pH 7.2. The presence of serum also decreased the activity of E-4868. Fifty percent effective dose (ED50) values against experimental Escherichia coli HM-42 infections in mice were 3.9 mg/kg of body weight with E-4868 and 3.5 mg/kg of body weight with ciprofloxacin. Corresponding ED50 values against P. aeruginosa HS-116 were 93.2 and 107.8 mg/kg, respectively, and those against Staphylococcus aureus HS-93 were 6.5 and 44.6 mg/kg, respectively. In experimental infections with Streptococcus pneumoniae 84551, the ED50 value of E-4868 was 154.4 mg/kg, while ciprofloxacin proved totally inactive at a dose of 400 mg/kg. When E-4868 was administered orally at a dose of 50 mg/kg in mice, the area under the concentration-time curve (0 to 4 h) value was 28.4 microgram . h/ml, while an area under the concentration-time curve value of 2.3 microgram . h/ml was observed for ciprofloxacin at the same dose. In these studies, levels of the two agents in blood 1 h postadministration were 7.6 and 1.2 microgram/ml, respectively.

Cloning and nucleotide sequence of the Campylobacter jejuni gyrA gene and characterization of quinolone resistance mutations

The gyrA gene of Campylobacter jejuni UA580, which encodes the A subunit of DNA gyrase, was cloned and its nucleotide sequence was determined. An open reading frame of 2,589 nucleotides was identified, which could code for a polypeptide of 863 amino acids with a M(r) of 97 kDa. Both the nucleotide sequence and the putative amino acid sequence show ca. 50% identity with those of other gyrA genes from gram-positive and gram-negative bacteria. The locations of the gyrA gene on genome maps of both C. jejuni UA580 and Campylobacter coli UA417 were determined. Six nalidixic acid-resistant isolates of C. jejuni were shown to carry mutations in gyrA. Three clinical isolates had Thr-86-to-Ile substitutions. Three laboratory mutants had substitutions of Thr-86 to Ile, Asp-90 to Ala, and Ala-70 to Thr, respectively. The mutation at Thr-86, which is homologous to Ser-83 in Escherichia coli, was associated with high-level resistance to ciprofloxacin in C. jejuni.

Mechanisms of action of cephalosporin 3'-quinolone esters, carbamates, and tertiary amines in Escherichia coli

Cephalosporin 3'-quinolone esters, carbamates, and tertiary amines are potent antibiotics whose antibacterial activities reflect the action of both the beta-lactam and the quinolone components. The biological properties of representative compounds from each class were compared in Escherichia coli. All compounds bound to the essential PBP 3, inhibited DNA gyrase, and caused filamentation in growing cells. To distinguish between cephalosporin- and quinolone-induced filaments, nucleoid segregation was also examined, as quinolones disrupt nucleoid segregation while the beta-lactams do not (N. H. Georgopapadakou and A. Bertasso, Antimicrob. Agents Chemother. 35:2645-2648, 1991). The cephalosporin quinolone esters Ro 23-9424 and Ro 24-6392, at concentrations causing filamentation in E. coli ATCC 25922, did not affect nucleoid segregation after 1 h of incubation (cephalosporin response) but did not affect it after 2 h (quinolone response), indicating the release of free quinolone. Accordingly, only the quinolone response was produced in a strain possessing TEM-3, an expanded-spectrum beta-lactamase. The cephalosporin carbamate Ro 24-4383 and the tertiary amine Ro 24-8138 produced a quinolone response in E. coli ATCC 25922, though they produced a cephalosporin response in a quinolone-resistant strain. Carbamate and tertiary amine linkages are chemically more stable than the ester linkage, and both cephalosporin 3'-quinolone carbamates and tertiary amines are more potent inhibitors of DNA gyrase than are the corresponding esters. The results suggest that, while intact cephalosporin 3'-quinolone esters act as cephalosporins, carbamates and amines may possess both cephalosporin and quinolone activity in the intact molecule.

Treating acute urinary tract infections. An RCT of 3-day versus 7-day norfloxacin

A randomized, controlled trial was carried out to compare two courses of treatment in women with acute urinary tract infection in general practice. The 3-day course of treatment was found to be as effective as, and cheaper than, the 7-day therapy.

Rufloxacin once daily versus ofloxacin twice daily for treatment of complicated cystitis and upper urinary tract infections. Italian Multicentre UTI Rufloxacin Group

The efficacy and safety of rufloxacin once daily was compared with that of ofloxacin b.i.d. for therapy of complicated cystitis and upper urinary tract infections. Eighty-three patients were randomly assigned to receive rufloxacin as a loading dose of 400 mg on the first day, followed by 200 mg s.i.d., and 80 received ofloxacin 300 mg b.i.d. Both agents were administered orally for a median duration of eight days. Bacterial elimination rates after treatment were 90% for rufloxacin and 81% for ofloxacin. Half of the treatment failures occurred in patients with infections caused by uropathogens that became either less sensitive or resistant to the quinolones being studied. At a two-week follow-up, recurrences had not occurred in any of the rufloxacin patients and had occurred in 17% of the ofloxacin patients. Minor adverse reactions were reported by 12 and 13 patients, respectively. Rufloxacin once daily is as effective as ofloxacin b.i.d. for the treatment of complicated cystitis and upper urinary tract infections.

CI-990 (PD 131112): A new quinolone prodrug

In vitro susceptibility of 1021 strains of recent clinical isolates was determined against the new fluoroquinolone CI-990 (PD 131112) and compared with CI-960, ciprofloxacin, fleroxacin, lomefloxacin, norfloxacin, perfloxacin, sparfloxacin, and temafloxacin. The minimum inhibitory concentrations (MIC) of CI-990 in mg/L required for >90% isolates were 0.03-0.5 for members of Enterobacteriaceae, 0.12-2.0 for Pseudomonas aeruginosa, 0.03-1.0 for Aeromonas hydrophilia, 1.0-2.0 for Acinetobacter calcoaceticus, 0.5-2.0 for Brucella melitensis, 0.06-1.0 for staphylococci, and 1.0-2.0 for enterococci. Its antibacterial activity was comparable or superior to other fluroquinolones tested against most gram-negative and gram-positive bacteria, including enterococci.

In vitro antimicrobial activity of CP-99,219, a novel azabicyclo-naphthyridone

CP-99,219 is a trifluoronaphthyridone with significant antibacterial activity that includes the family Enterobacteriaceae (MICs for 90% of the strains tested [MIC90s], < or = 0.015 to 0.5 micrograms/ml), Moraxella catarrhalis, Haemophilus influenzae, and gonococci (MICs, < or = 0.015 micrograms/ml). Legionella spp. were also CP-99,219 susceptible, with MICs of 0.008 to 0.12 micrograms/ml. CP-99,219 demonstrated activity greater than that of ciprofloxacin, ofloxacin, or enoxacin against Pseudomonas aeruginosa (MIC90, 1 microgram/ml), Xanthomonas maltophilia (MIC90, 2 micrograms/ml), Staphylococcus haemolyticus (MIC90, 0.5 micrograms/ml), Enterococcus faecalis (MIC90, 1 microgram/ml), and pneumococci (MIC90, 0.12 micrograms/ml). Numerous ciprofloxacin-resistant isolates were susceptible to CP-99,219, a new compound showing potential value for further in vivo trials.

Increased resistance to quinolone in Catalonia, Spain

From 1989 to 1991, the level of resistance to ciprofloxacin in our hospital increased from 0.47% to 6.7% in opportunistic Enterobacteriaceae, from 9.9% to 16% in Pseudomonas aeruginosa and from 8.27% to 31.8% in Campylobacter jejuni-coli. We also observed an increase in quinolone consumption from 1.1 in 1989 to 1.5 defined daily doses per 1000 inhabitants per day in 1991.

Rat cytomegalovirus-induced pneumonitis after allogeneic bone marrow transplantation: effective treatment with (S)-1-(3-hydroxy-2-phosphonyl-methoxypropyl)cytosine

Two antiviral compounds, (S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine (HPMPC) and 9-(1,3-dihydroxy-2-propoxymethyl)guanine (DHPG), were evaluated for their effects on rat cytomegalovirus (RCMV)-induced interstitial pneumonitis after allogeneic bone marrow transplantation (BMTx). Eight-week-old Brown Norway rats immunosuppressed by a lethal dose of total body irradiation were inoculated with RCMV and received allogeneic bone marrow cells from Lewis rats. Animals were treated with either HPMPC (20 mg/kg of body weight as a single dose) or DHPG (20 mg/kg as two daily doses for 5 days). The effect of antiviral therapy was monitored by measuring RCMV titers in different organs and the histopathologic changes in lungs at 8 to 10 days postinfection. In RCMV-infected allogeneic BMTx recipients, severe diffuse thickening of alveolar septa (6.02 microns) with a diffuse infiltration of mononuclear cells occurred, whereas in the noninfected allogeneic BMTx recipients, the septal width was on the order of 2 microns (P < 0.01). Treatment with DHPG (20 mg/kg in two daily doses for 5 days) resulted in a decrease in virus titers (log10 PFU per gram of tissue) in lungs and spleens from 3.81 +/- 0.34 and 4.29 +/- 1.07 (untreated animals) to 1.26 +/- 0.53 and 3.22 +/- 0.27 (treated animals), respectively. Treatment with HPMPC (20 mg/kg as a single dose) resulted in a complete reduction of virus titers in all organs to below the detection level (P < 0.01). Furthermore, antiviral treatment resulted in a reduction of the alveolar septal width from 6.02 +/- 1.59 microns (untreated animals) to 4.67 +/- 1.70 and 3.32 +/- 0.63 microns after DHPG and HPMPC treatment, respectively. Treatment with HPMPC (20 mg/kg as a single dose) resulted in a complete reduction of virus titers in all organs to below the detection level (P <0.01). Furthermore, antiviral treatment resulted in a reduction of the alveolar septal width from 6.02 +/- 1.59 micrometre (untreated animals) to 4.67 +/- 0.63 micrometre after DHPG and HPMPC treatment, respectively. Furthermore, the influx of mononuclear cells in the alveolar septa was significantly impaired after treatment with HPMPC (P <0.01). We conclude that in the described rat model, HPMPC is highly effective in suppressing RCMV-induced interstitial pneumonitis after allogeneic BMTx.

Molecular epidemiology and antimicrobial susceptibility testing. Testing of quinolone-resistant Staphylococcus aureus strains isolated in Brazil

An outbreak of 20 oxacillin-resistant Staphylococcus aureus (ORSA) bloodstream infections (BSIs) was detected in the intensive care unit (ICU) at Hospital Sao Paulo, Brazil. In a surveillance study, 10% of ICU personnel were defined as chronic nasal carriers of ORSA. Thirteen BSIs and five nasal isolates were available for phage typing, restriction endonuclease analysis of plasmid (REAP) and chromosomal DNA hybridized with 32P rRNA gene probe. Susceptibility testing against select antimicrobial agents, including 11 quinolones, six glycopeptides, and five topical agents, was performed by broth microdilution and the disk diffusion tests. Ten of the 13 BSI isolates and four of the five nasal strains were oxacillin and quinolone resistant. The new fluoroquinolones CI-960 and WIN57273, the glycopeptides, and the topical agents ramoplanin, bacitracin, mupirocin, and novobiocin were most active. Fourteen strains, 12 BSI isolates, and three nasal isolates showed the same REAP profile. Moreover, the same REAP and chromosomal profile was detected in at least nine BSI isolates and in two nasal isolates. These strains were nontypable by phage typing. We concluded that nosocomial cross-transmission of a single, multiresistant strain of S. aureus occurred and that the epidemic reservoir was nasal carriage by ICU personnel.

The epidemiology of bacterial resistance to quinolones

The new fluoroquinolones have been in use for nearly 10 years in the treatment of community- and nosocomially-acquired infections. Resistant clones may be selected during therapy and disseminate if favourable epidemiological conditions prevail. Resistance to the fluoroquinolones is still rare in common pathogens with 97 to 100% of strains remaining susceptible. Resistance has been reported in methicillin-susceptible Staphylococcus aureus, Campylobacter jejuni/coli, Salmonella, Shigella and Escherichia coli. Among nosocomial pathogens, the incidence of fluoroquinolone resistance varies between bacterial species, countries and periods of study, and is dependent on local epidemiological factors and antibiotic policies. The highest incidence of resistance is observed in Serratia and Acinetobacter spp., and particularly in methicillin-resistant S. aureus. Surveillance programmes are needed to follow up trends in resistance to the fluoroquinolones and their possible association with clinical failures.

Fluoroquinolones in the treatment of cystic fibrosis

Cystic fibrosis patients suffer from recurrent and chronic lung infections mainly caused by Staphylococcus aureus, Haemophilus influenzae and Pseudomonas aeruginosa. The fluoroquinolones, notably ciprofloxacin and ofloxacin, represent an important addition to the therapy of P. aeruginosa infections. They offer the possibility of effective oral treatment for early colonisation as well as chronic infections, even in children. They are associated with only few and mild adverse effects. Development of resistance represents an increasing problem.

Quinolones in sexually transmitted diseases

The role of quinolones in the treatment of sexually transmitted diseases is assessed. Little is known of their activity against Treponema pallidum. These compounds are all highly active against Neisseria gonorrhoeae, and have produced good in vivo results with a single dose. Only the more recent compounds show useful antichlamydial activity in vitro. Clinical trials with ofloxacin demonstrate the efficacy of a single daily dose for 7 days for chlamydial genital infection in men and women. Results for treatment of bacterial vaginosis have so far been disappointing. Ciprofloxacin and fleroxacin are effective for chancroid. The potential for treating pelvic inflammatory disease with new quinolones is discussed.

In vitro activity of nine fluoroquinolone antibiotics against 200 strains of enterococci

The in vitro activity of nine fluoroquinolones against 200 recent clinical isolates of enterococci was evaluated. The relative activity was WIN57273 > sparfloxacin > ciprofloxacin, temafloxacin > ofloxacin > fleroxacin, lomefloxacin, norfloxacin > enoxacin. Susceptibility to gentamicin or streptomycin did not influence the activity of the fluoroquinolones.

Antimicrobial susceptibility patterns of common and unusual species of enterococci causing infections in the United States. Enterococcal Study Group

We collected 705 isolates of enterococci (1 per patient) from cultures of a variety of anatomic sites from patients at eight tertiary-care hospitals in six geographic regions of the United States. A total of 632 (90%) Enterococcus faecalis, 58 (8%) E. faecium, 5 E. gallinarum, 4 E. avium, 3 E. casseliflavus, 1 E. raffinosus, and 1 E. hirae isolate and 1 biochemical variant of E. faecalis were identified; 606 (86%) of these isolates were associated with clinical infections. The most common sites of isolation were the urinary tract (402 [57%]), nonsurgical wounds (94 [13%]), the bloodstream (74 [10%]), and surgical wounds (62 [9%]). High-level resistance to gentamicin or streptomycin or both was detected in 265 (38%) of the isolates. We identified two E. faecalis isolates resistant to vancomycin (MICs, 32 and 128 micrograms/ml) and 11 beta-lactamase-producing E. faecalis isolates. E. faecium isolates were significantly more resistant than E. faecalis isolates to penicillin, ampicillin, piperacillin, imipenem, and ciprofloxacin (P less than 0.001). The MICs for the 15 non-E. faecalis, non-E. faecium enterococci indicated variable resistance to ciprofloxacin and the penicillins. Antimicrobial susceptibility patterns vary among species of enterococci, and these organisms, while commonly resistant to high-level aminoglycosides, can also acquire resistance to vancomycin or the ability to produce beta-lactamase. Because of these diverse antimicrobial resistance mechanisms, successful treatment and control of enterococcal infections with current antimicrobial agents are becoming increasingly difficult.

In vitro activity of CP-74667 compared with four other fluoroquinolones

CP-74667 is a new, novel C-7 diazabicyclo-fluoroquinolone. Its spectrum of activity includes the Enterobacteriaceae, most nonenteric Gram-negative bacilli, and Gram-positive cocci. Particularly high activity was demonstrated against Xanthomonas maltophilia (MIC50, 1 microgram/ml), Staphylococcus spp. (MIC50s, 0.06-0.12 micrograms/ml) and enterococci (MIC50s, 0.5-4 micrograms/ml). Several staphylococci resistant to ciprofloxacin had potentially susceptible range MICs for CP-74667, for example, less than or equal to 2 micrograms/ml. Fluoroquinolones with this C-7 modification appear promising and worthy of continued pharmaceutical investigation.

Quinolone accumulation in Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus

The accumulation of quinolones by Escherichia coli JF568, Pseudomonas aeruginosa PAO1, and Staphylococcus aureus ATCC 29213 was measured by a modified fluorometric assay (J. S. Chapman and N. H. Georgopapadakou, Antimicrob. Agents Chemother. 33:27-29, 1989). The quinolones examined were fleroxacin, pefloxacin, norfloxacin, difloxacin, A56620, ciprofloxacin, ofloxacin, and Ro 09-1168. In all three organisms, uptake was complete in less than 5 min and was proportional to extracellular quinolone concentrations between 2 and 50 micrograms/ml, which is consistent with simple diffusion. Washing cells with quinolone-free buffer decreased accumulation by up to 70% in E. coli and P. aeruginosa but not in S. aureus. Similarly, incubation with the uncouplers 2,4-dinitrophenol and carbonyl cyanide m-chlorophenylhydrazone increased accumulation up to fourfold in E. coli and P. aeruginosa, though not in S. aureus, suggesting endogenous, energy-dependent efflux. High quinolone hydrophobicity was generally associated with decreased accumulation in E. coli and P. aeruginosa (except in the case of pefloxacin) but was associated with increased accumulation in S. aureus (except in the case of difloxacin). Ciprofloxacin had the highest accumulation in E. coli and P. aeruginosa, while pefloxacin had the highest accumulation in S. aureus.

Ofloxacin, a new broad-spectrum fluoroquinolone. Results from a Multicenter, National Comparative Activity Surveillance Study. The Ofloxacin Surveillance Group

Ofloxacin, a newer broad-spectrum fluoroquinolone, was evaluated against 6967 clinical isolates in a multicenter surveillance trial using a standardized disk diffusion method. Thirty-five geographically diverse laboratories contributed zone diameter results for two (ofloxacin and ciprofloxacin) to five (ofloxacin, ciprofloxacin, ampicillin, cefaclor, and cefixime) antimicrobial agents, depending on the site of infection. Ofloxacin was determined to have the widest spectrum of activity and potential empiric use (90.6%, range 87.1%-92.2%) for respiratory tract, urinary tract, and cutaneous infections. The spectrum was superior to ciprofloxacin (average 85.3% versus three sites), ampicillin (35.5%, respiratory tract), cefaclor (60.5%, respiratory tract), cefixime (60.9%, respiratory tract), and norfloxacin (87.3%, urinary tract). Strains resistant to ofloxacin (35 isolates, 0.5%) were confirmed by reference laboratory tests and cross resistance was observed among several current and investigational fluoroquinolone agents. The species most often found to be fluoroquinolone resistant among the Enterobacteriaceae were Klebsiella pneumoniae, Serratia marcescens, and Providencia spp. Monitoring for increasing fluoroquinolone resistance should be considered as greater use of drugs in this class develops. By these cited statistics, ofloxacin appears to have a broad and balanced spectrum of potential use, particularly against Gram-positive pathogens.

The use of oral fluoroquinolones in nursing home patients

The approach to management of patients with presumed infection in the nursing home is influenced by the limited availability of diagnostic tests and support staff. Although antibiotics are most often prescribed in the absence of laboratory data, many studies indicate that empirical therapy for nursing home infections is relatively successful. With the scrutiny on containment of healthcare costs, therapy of nursing home patients has been changing and will continue to shift toward treatment within nursing homes without transfer to a hospital. Better oral antimicrobial agents with a wide spectrum of activity, such as the fluoroquinolones, will play a major role in the treatment of many infections acquired in the nursing home. Because of the favourable characteristics of the fluoroquinolone agents, they should be useful for elderly patients who develop infections in nursing homes. They have excellent in vitro activity against Gram-negative bacteria which are often multidrug-resistant and are common in nursing home patients. Studies indicate that absorption of orally administered fluoroquinolones is very efficient in the elderly and these drugs are well tolerated. Numerous clinical trials have documented good efficacy of the fluoroquinolones in the treatment of elderly patients for the most common infections in the nursing home, including urinary tract infections, respiratory tract infections and skin infections.

Comparative in vitro activity of PD 127391, a new fluoroquinolone agent, against susceptible and resistant clinical isolates of gram-positive cocci

We examined the in vitro activity of PD 127391, an investigational fluoroquinolone antibacterial agent, against staphylococci (including methicillin-resistant Staphylococcus aureus), enterococci (including beta-lactamase-producing and highly gentamicin-resistant isolates), and streptococci. The compound was active against all organisms tested and compared favorably with antimicrobial agents routinely used to treat infections with these organisms. On the basis of MICs for 90% of the strains tested, PD 127391 was 32-fold more active against all staphylococci, 16-fold more active against methicillin-resistant S. aureus, 8-fold more active against all streptococci, and 4-fold more active against all enterococci than ciprofloxacin. PD 127391 was shown to be more active than sparfloxacin, which in turn was shown to be more active than ciprofloxacin, against these gram-positive cocci. PD 127391 shows promise for the treatment of infections with gram-positive cocci, including organisms which are resistant to other commonly used antimicrobial agents.

A double-blind study of two dosage regimens of lomefloxacin in bacteriologically proven exacerbations of chronic bronchitis of gram-negative etiology

Lomefloxacin has been shown to produce high and sustained concentrations in serum and bronchial mucosa after once-daily administration. This study was designed to assess whether a dose response exists for 400 mg lomefloxacin given once daily or twice daily for 10 days in the treatment of acute bacterial exacerbations of chronic bronchitis of gram-negative etiology. A total of 100 adult patients with acute exacerbations of chronic bronchitis were enrolled at 10 study sites in Germany. Patients with confirmed bacterial pathogens in the baseline sputum culture (once-daily group n = 49, twice-daily group n = 47) were eligible for analysis of bacteriologic and clinical efficacy. The eradication rates for the most frequently isolated baseline pathogens, Haemophilus influenzae, Pseudomonas aeruginosa, and Klebsiella pneumoniae, were at least 75% for both treatment regimens. Overall, once-daily treatment eradicated baseline pathogens in 42 of 49 (85.7%) patients, while twice-daily treatment eradicated pathogens in 43 of 47 (91.5%). This difference was not statistically significant (p = 0.226). Clinically, 47 of 49 (95.9%) patients in the once-daily group and 46 of 47 (97.9%) in the twice-daily group were cured or improved (p = 0.307). Both regimens were well tolerated; there were no differences in the incidence (six patients in each group), types, or severity of adverse events, nor was there clinical evidence of theophylline interaction. The results of this study demonstrate that once-daily treatment with 400 mg lomefloxacin is as effective as twice-daily dosing with 400 mg in patients with acute bacterial exacerbations of chronic bronchitis.

Lomefloxacin: microbiologic assessment and unique properties

In comparative studies, lomefloxacin, a new difluorinated quinolone, exhibits broad antibacterial activity in vitro, similar or superior to that of other quinolones (enoxacin, ofloxacin, pipemidic acid, nalidixic acid, and norfloxacin) but less than that of ciprofloxacin. Lomefloxacin inhibited Neisseria gonorrhoeae, Moraxella (Branhamella) catarrhalis, Haemophilus influenzae, Pseudomonas aeruginosa, Staphylococcus aureus, and the majority of aerobic gram-negative rods, including nosocomial isolates, at concentrations readily achievable in biologic fluids and tissues. Lomefloxacin was less active against obligate anaerobes and streptococci. Organisms resistant to methicillin, penicillin, or the aminoglycosides were susceptible to lomefloxacin. No significant lomefloxacin resistance was identified in 18 countries in which in vitro studies were conducted, with the exception of a small number of strains tested in France. The frequency with which spontaneous single-step resistance to lomefloxacin develops in vitro is low.

Safety and efficacy of lomefloxacin versus cefaclor in the treatment of acute exacerbations of chronic bronchitis

In two multicenter trials, lomefloxacin and cefaclor were compared as treatments for acute bacterial exacerbations of chronic bronchitis. In total, 522 adult outpatients were enrolled at 50 centers in the United States. Patients were randomized to treatment groups receiving either 400 mg lomefloxacin orally once daily (n = 259) or 250 mg cefaclor every 8 hours (n = 263) for 7-10 days. Both groups were comparable in terms of age, severity of exacerbation, smoking history, theophylline use, and baseline pathogens. The most common baseline pathogens were Haemophilus influenzae, found in 32% of patients in the lomefloxacin group and in 29% in the cefaclor group, Pseudomonas aeruginosa (13% and 16%, respectively), Moraxella (Branhamella) catarrhalis (12% and 13%), and Streptococcus pneumoniae (10% in both groups). Bacterial eradication rates 1-4 days after the completion of treatment for all patients with baseline pathogens were 81.8% in the lomefloxacin group and 62.7% in the cefaclor group (p less than 0.001). Clinical success (disappearance or improvement of presenting signs and symptoms) was noted in 80.0% of patients in the lomefloxacin group and 64.7% in the cefaclor group (p = 0.002). Eradication rates for the subgroup of patients who had pathogens susceptible in vitro to both study drugs and who completed treatment were 97.1% for lomefloxacin and 84.6% for cefaclor (p = 0.002). Clinical success rates in this subgroup were 92.4% for lomefloxacin and 90.1 for cefaclor (p = 0.585). Treatment-related adverse events were reported for 7% of patients in the lomefloxacin group and 5% in the cefaclor group. The most common adverse events in both groups were nausea and diarrhea. Six patients were withdrawn from treatment with lomefloxacin and four from the cefaclor group because of adverse events. There was no clinical or laboratory evidence of theophylline interaction with either treatment. Once-daily oral administration of 400 mg lomefloxacin was an effective, well-tolerated alternative to 250 mg of cefaclor three times daily in the treatment of acute exacerbations of chronic bronchitis.

Efficacy and safety of temafloxacin versus those of amoxicillin in hospitalized adults with community-acquired pneumonia

Temafloxacin, a new fluoroquinolone, was compared with amoxicillin in the treatment of adult hospitalized patients with community-acquired pneumonia. In this double-blind, multicenter study, patients were randomly assigned to treatment with temafloxacin at 600 mg twice daily (n = 125) or amoxicillin at 500 mg three times daily (n = 121); the average duration of treatment was 10 days. Clinical recovery rates were similar for patients treated with temafloxacin and amoxicillin (89 and 85%), as were bacterial eradication rates (99 and 97%). This was also true for subgroups of patients with pneumococcal pneumonia (n = 100), nonpneumococcal pneumonia (n = 122), or atypical pneumonia (n = 12). Outcomes for temafloxacin- and amoxicillin-treated patients were also similar in terms of defervescence, improvement in leukocytosis, and radiographic evidence of infection. The frequency and severity of adverse events were similar in both groups, consisting primarily of digestive disorders and skin manifestations. We conclude that temafloxacin may be recommended as an alternative antibacterial drug for patients with suspected pneumococcal pneumonia who fail to respond to benzylpenicillin or amoxicillin when the incidence of multiresistant pneumococcal strains is low. In countries where the incidence of these strains is high, temafloxacin may also be recommended.

In vitro activity of OPC-17116 compared to other broad-spectrum fluoroquinolones

The in vitro activity of OPC-17116 was compared to that of five similar fluoroquinolones (ciprofloxacin, enoxacin, norfloxacin, ofloxacin and temafloxacin). A total of 700 isolates from recent cases of clinical bacteremia were tested. Fifty additional stock strains with well-characterized resistance mechanisms were also processed. The minimal concentrations inhibiting 90% of strains (MIC90) of Enterobacteriaceae species were for OPC-17116 0.015-0.5 micrograms/ml and for ciprofloxacin 0.015-0.25 micrograms/ml. Moraxella catarrhalis, Haemophilus influenzae and Neisseria gonorrhoeae were very susceptible to OPC-17116 (MIC90 0.015 micrograms/ml) thus being fourfold more active than ciprofloxacin. For all beta-hemolytic streptococci and pneumococci OPC-17116 MICs were less than or equal to 0.5 micrograms/ml. The most resistant enteric bacilli were among the Citrobacter freundii and Providencia rettgeri strains (MIC90 0.5 micrograms/ml). Pseudomonas aeruginosa strains were comparably susceptible to OPC-17116 (MIC90 0.5 micrograms/ml). Low pH and CO2 incubation had an adverse effect on OPC-17116 MICs, and resistance development was documented among current clinical isolates of staphylococci, pseudomonas and some Enterobacteriaceae.

Synergism of trimethoprim and ciprofloxacin in vitro against clinical bacterial isolates

For the first time, the effects of combinations of trimethoprim and a fluoroquinolone (ciprofloxacin) against gram-positive and gram-negative bacterial isolates were evaluated in vitro. Synergism was found in 31% (fractional inhibitory concentration, FIC) and 33% (fractional bactericidal concentration, FBC) of 121 clinical isolates of various bacterial strains, most often in Escherichia coli, staphylococci, and enterococci. Antagonism occurred in 1% (FIC) and 3% (FBC). The combination of trimethoprim and ciprofloxacin merits further evaluation for potential usefulness as a clinical regimen.

Penetration of ciprofloxacin into human peritoneal tissue following a single oral dose of 750 milligrams

The penetration of ciprofloxacin into the peritoneal tissue was studied in 10 patients after a single oral dose of 750 mg given 5.6 hours (mean) before elective laparotomy. The mean tissue level was 0.29 micrograms/ml (range, 0.082 to 0.96 micrograms/ml) while the mean concomitant serum level was 1.3 micrograms/g (range, 0.52 to 2.57 micrograms/g). The achieved concentrations are above the minimum inhibitory concentrations (MICs) of ciprofloxacin for most gram-negative bacteria commonly involved in intra-abdominal infections.

Fleroxacin clinical pharmacokinetics

Fleroxacin is a new member of the class of fluoroquinolones. The drug has good activity (i.e. minimum inhibitory concentrations at less than 2 mg/L against 90% of strains) against a wide range of Gram-positive and Gram-negative bacteria. High performance liquid chromatography is used to determine concentrations of fleroxacin and its metabolites in biological fluids. Absorption of orally ingested drug is rapid as the peak plasma concentration of approximately 5 mg/L is reached in 1 to 2h after a single dose of 400mg. The systemic availability is close to 100%. Fleroxacin is poorly bound to plasma proteins (23%) and exhibits excellent tissue distribution. Renal clearance accounts for 60 to 70% of elimination. The drug is metabolised to form antimicrobially active N-demethyl-fleroxacin and inactive N-oxide-fleroxacin. In multiple dose studies the accumulation ratio of a once-daily dosage regimen is about 1.3, as predicted from the elimination half-life of 10 to 12h. Compared with ciprofloxacin, fleroxacin has a greater systemic availability and a longer half-life. Fleroxacin concentrations are higher in elderly patients, but further studies are needed to establish whether a dosage reduction should be recommended for this age group. In patients with renal disease dosage adjustment is recommended since a decreased renal clearance of fleroxacin leads to a significant prolongation of the elimination half-life. Fleroxacin is only poorly eliminated by peritoneal dialysis or haemodialysis. The most important drug-drug interaction is a decrease in systemic availability of fleroxacin after ingestion of aluminium- or magnesium-containing antacids. There is no evidence of a significant interaction between fleroxacin and theophylline. Only limited data are available on adverse reactions of fleroxacin. The most important adverse effects appear to be photosensitivity and a dose-dependent incidence of central nervous system reactions including sleep disorders.

Epidemiologic typing of Staphylococcus aureus by DNA restriction fragment length polymorphisms of rRNA genes: elucidation of the clonal nature of a group of bacteriophage-nontypeable, ciprofloxacin-resistant, methicillin-susceptible S. aureus isolates

Analysis of DNA restriction fragment length polymorphisms of rRNA genes (ribotyping) was employed to assist in the epidemiologic investigation of the emergence and spread of ciprofloxacin-resistant Staphylococcus aureus at the Atlanta VA Medical Center because many isolates of interest were nontypeable by phages and harbored few plasmids useful as strain markers. Chromosomal DNAs of selected S. aureus isolates were digested initially with 20 different restriction enzymes. EcoRI appeared to give the best discrimination of hybridization banding patterns (ribotypes) and was used with all study isolates. Overall, 15 different ribotypes were seen among the 50 S. aureus isolates studied (7 ribotypes among 13 methicillin-susceptible S. aureus [MSSA] isolates and 9 ribotypes among 37 methicillin-resistant S. aureus [MRSA] isolates). Seven of eight ciprofloxacin-resistant MSSA (CR-MSSA) patient isolates had identical antibiograms, were nontypeable by phages, and had a single 22-MDa plasmid. Six of these seven CR-MSSA isolates had an identical ribotype pattern. Ribotyping distinguished this CR-MSSA strain or clone from MRSA and other MSSA isolates, including nontypeable isolates that contained a 22-MDa plasmid. Five ciprofloxacin-susceptible MSSA isolates studied had five ribotypes; one pattern was identical to the CR-MSSA clone. Twenty-three CR-MRSA isolates recovered from the Atlanta VA Medical Center had four different ribotypes. Ribotyping proved to be a useful molecular epidemiologic tool in the study of S. aureus because it differentiated isolates which were indistinguishable by more traditional methods. In addition, this technique demonstrated that at our institution, ciprofloxacin resistance emerged in multiple strains of MRSA, as opposed to primarily a single strain or clone of MSSA.

Safety and pharmacokinetics of multiple doses of intravenous ofloxacin in healthy volunteers

The safety and pharmacokinetics of ofloxacin in 48 healthy male volunteers were studied in a two-center, randomized, double-blind, placebo-controlled study. Ofloxacin (200 or 400 mg) or placebo was administered as 1-h infusions every 12 h for 7 days. Plasma ofloxacin concentrations were measured by high-performance liquid chromatography. Mean harmonic half-lives ranged from 4.28 to 4.98 h in the 200-mg dosing group and from 5.06 to 6.67 h in the 400-mg dosing group. Intragroup comparisons of trough plasma concentration-versus-time data from study days 2 through 7 revealed that steady state was achieved by day 2 of both multiple-dose regimens. Intergroup comparisons of mean harmonic half-lives, the areas under the concentration-time curve from 0 to 12 and 0 to 60 h, clearance, and apparent volume of distribution (area method) revealed that the pharmacokinetics of ofloxacin are dose independent. Both ofloxacin dosage regimens appeared to be reasonably well tolerated. The two dosage regimens of ofloxacin, 200 or 400 mg every 12 h, appear to be safe and provide serum drug concentrations in excess of the MICs for most susceptible pathogens over the entire dosing interval.

Induction of calf thymus topoisomerase II-mediated DNA breakage by the antibacterial isothiazoloquinolones A-65281 and A-65282

A number of quinolones and related antibacterial compounds were screened for activity against calf thymus topoisomerase II by using the P4 unknotting and DNA breakage assays. Several compounds from different structural classes which inhibited DNA unknotting with 50% inhibitory concentrations ranging from 8 to 25 micrograms/ml were identified. Two experimental isothiazoloquinolones from this group, designated A-65281 and A-65282, were also found to induce considerable DNA breakage mediated by calf thymus topoisomerase II, with 32P-end-labeled pBR322 as the substrate. These compounds were nearly as potent as teniposide, with DNA breakage activity evident at concentrations as low as 4 micrograms/ml. However, some differences in DNA cleavage patterns from those with teniposide were evident. These studies have thus identified a new class of agents which have activity against both bacterial and eukaryotic type II topoisomerases. The implications of these data for the selectivity of topoisomerase-directed compounds and the potential toxicity of such compounds developed as antibacterial agents are discussed.

Penetration of temafloxacin into body tissues and fluids

The new fluoroquinolone antimicrobial temafloxacin shows good penetration into a range of body tissues and fluids, after single or repeated oral administration to healthy volunteers and patients undergoing various procedures. Temafloxacin concentrations in respiratory tissues and fluids, nasal secretions, tonsils, prostate, semen, bone and blister fluid were similar to, or greater than, concurrent serum concentrations. Penetration into sinus secretions and cerebrospinal fluid is less marked; nevertheless, temafloxacin concentrations of approximately 2.4 and 1 mg/L, respectively, were achieved. Concentrations of temafloxacin observed in these tissues and fluids exceed the minimum concentrations required to eradicate the majority of bacterial pathogens associated with respiratory infections, tonsillitis, sinusitis, prostatitis, bone infections and meningitis. Since elimination of temafloxacin occurs by the renal route, high concentrations of the drug are also found in the urine. Biliary excretion of temafloxacin accounts for about 3% and leads to high biliary concentrations of the drug.

The quinolones. An overview of their pharmacology

The fluoroquinolones represent a relatively new class of antibiotics with outstanding therapeutic potential, attributable to their broad spectrum of antimicrobial activity and favourable tissue distribution. They are highly active against most Gram-negative pathogens, as well as Staphylococcus aureus and coagulase-negative staphylococci. In addition, the fluoroquinolones have useful pharmacokinetic properties: they are orally active, and their lipophilicity and low degree of plasma protein binding allow for excellent tissue penetration and concentrations, as reflected in their particularly large apparent volumes of distribution. Infections due to aerobic Gram-negative pathogens are considered those most susceptible to the quinolones. Disease indications in which these agents appear to offer the greatest therapeutic advantage over currently available alternatives include the following: complicated urinary tract infections (particularly those caused by Pseudomonas aeruginosa or resistant Gram-negative microorganisms); suspected bacterial gastroenteritis; eradication of Salmonella typhi from the faeces in known carriers; P. aeruginosa-associated respiratory exacerbation in patients with cystic fibrosis; and chronic Gram-negative bacterial osteomyelitis. Direct comparisons of the various quinolones are too limited to date to provide clear therapeutic options. Nevertheless, this class of compounds is likely to play a major role in providing effective oral therapy for conditions that have previously required prolonged parenteral treatment.

Pharmacodynamics and pharmacokinetics of antibiotics with special reference to the fluoroquinolones

The pharmacodynamic and pharmacokinetic properties of antibiotics have received increased attention in recent years, leading to optimization of dosage regimens. In view of these characteristics, certain fluoroquinolones may prove advantageous compared with other antimicrobials for treatment of selected infections. Several new fluoroquinolone antimicrobial agents have potency equal to or greater than that of beta-lactam antibiotics against gram-negative aerobic bacilli, including Pseudomonas aeruginosa. In vitro bactericidal activity of these compounds is more rapid than that of the beta-lactams, often resembling that for the aminoglycosides. Like the aminoglycosides, but in contrast to the beta-lactams, fluoroquinolones exert a significant in vitro postantibiotic effect against some strains of P. aeruginosa and Enterobacteriaceae. However, unlike many beta-lactam and aminoglycoside antimicrobial agents that have similar in vitro activity, fluoroquinolones are often effective both after oral and parenteral administration. Important pharmacokinetic properties of fluoroquinolones include differences in the extent and variability in oral absorption and clearance, which determine the extent of in vivo exposure to drug. Drugs and dosage regimens that result in a high degree of exposure, particularly high peak levels of drug, may be preferable because of a greater extent of bacterial killing and less selection of drug-resistant bacteria.

Comparison of organ-specific toxicity of temafloxacin in animals and humans

This article summarizes animal studies conducted to determine the toxic and mutagenic potential of temafloxacin. The four target tissues of potential concern with fluoroquinolone use are the kidney, the eye, the weight-bearing joints of young animals, and the central nervous system. Based on the results of these studies in rats and dogs, it appears unlikely that crystalluria or nephrotoxicity will occur in humans who receive temafloxacin. Pre-marketing clinical trials in humans (n = 5,308) correlate well with chronic toxicity animal studies, reporting no crystalluria or clinically significant nephrotoxicity. Reversible electroretinographic (ERG) changes in dog studies were demonstrated only with the administration of high temafloxacin dosages. A Phase I study evaluating the safety of temafloxacin at 600 mg b.i.d. for 14 days in human subjects reported no significant changes in ophthalmologic parameters. Evidence of cartilaginous joint damage was observed in puppies receiving oral temafloxacin, in young dogs receiving intravenous temafloxacin, and in a single dog receiving a lethal dosage in a dose range-finding study. However, these toxic findings were not evident in any dogs in the subacute or chronic oral toxicity studies or in a longer duration intravenous study. Although limited evidence would suggest that young children may not be at risk, thorough clinical investigations of quinolones in these patients have only recently been initiated. Signs of central nervous system toxicity caused by temafloxacin were absent in two rodent studies, during which clonic convulsions were induced by concomitant use of fenbufen plus enoxacin or ciprofloxacin, and in human subjects evaluated by positron emission tomography. Temafloxacin, contrary to most other quinolones, was considered nonmutagenic in all mutagenicity tests conducted. In reproductive studies, temafloxacin was not uniquely toxic to the developing conceptus in the laboratory rat, mouse, rabbit, or primate. Based on these animal studies, temafloxacin appears to be non-mutagenic and to have a low potential for producing renal or ocular toxicity; however, like other quinolones, it should not be routinely used in children or pregnant women because of evidence of cartilage damage reported in young dogs. Premarketing clinical trials to date confirm the safety of temafloxacin use in adults.