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

Trovafloxacin enhances the inflammatory response to a Gram-negative or a Gram-positive bacterial stimulus, resulting in neutrophil-dependent liver injury in mice

Trovafloxacin (TVX), a fluoroquinolone antibiotic, has been strongly linked with several cases of idiosyncratic hepatotoxicity in humans. Previous studies showed that a modest inflammatory stress induced by a Gram-negative bacterial stimulus [i.e., lipopolysaccharide (LPS)] rendered nontoxic doses of TVX hepatotoxic in mice. This study compared the interaction of TVX with Gram-negative and Gram-positive stimuli. Mice were given TVX 3 h before LPS (Gram-negative stimulus) or a peptidoglycan-lipoteichoic acid (PGN-LTA) mixture isolated from Staphylococcus aureus (Gram-positive stimulus). Administration of TVX, LPS, or PGN-LTA alone was nonhepatotoxic. However, TVX administration before PGN-LTA or LPS resulted in significant liver injury that occurred with similar time courses. TVX/PGN-LTA-induced hepatocellular necrosis was primarily localized to centrilobular regions, whereas that caused by TVX/LPS was predominantly midzonal. Administration of either LPS or PGN-LTA alone led to increased plasma concentrations of several cytokines and chemokines at a time near the onset of liver injury. TVX administration before LPS enhanced the concentrations of all of these cytokines, whereas TVX treatment before PGN-LTA increased all of the cytokines except tumor necrosis factor (TNF)-alpha and interferon-gamma. Liver injury was reduced in TVX/LPS- and TVX/PGN-LTA-treated mice given an antibody to CD18 and also in mice deficient in neutrophil [polymorphonuclear neutrophil (PMN)] elastase. Hepatic PMN accumulation and TNF-alpha production after TVX/PGN-LTA-, but not after TVX/LPS-coexposure, was CD18-dependent. In summary, TVX significantly enhanced the murine inflammatory response to either a Gram-negative or a Gram-positive stimulus and caused hepatotoxicity that developed similarly and was dependent on PMN activation in mice but that differed in lesion location and cytokine profile.

Quinolones in 2005: an update

Quinolones are one of the largest classes of antimicrobial agents used worldwide. This review considers the quinolones that are available currently and used widely in Europe (norfoxacin, ciprofloxacin, ofloxacin, levofloxacin and moxifloxacin) within their historical perspective, while trying to position them in the context of recent and possible future advances based on an understanding of: (1) their chemical structures and how these impact on activity and toxicity; (2) resistance mechanisms (mutations in target genes, efflux pumps); (3) their pharmacodynamic properties (AUC/MIC and Cmax/MIC ratios; mutant prevention concentration and mutant selection window); and (4) epidemiological considerations (risk of emergence of resistance, clonal spread). Their main indications are examined in relation to their advantages and drawbacks. Overall, it is concluded that these important agents should be used in an educated fashion, based on a careful balance between their ease of use and efficacy vs. the risk of emerging resistance and toxicity. However, there is now substantial evidence to support use of the most potent drug at the appropriate dose whenever this is required.

A novel antibacterial 8-chloroquinolone with a distorted orientation of the N1-(5-amino-2,4-difluorophenyl) group

Fluoroquinolones represent a major class of antibacterial agents with great therapeutic potential. In this study, we designed m-aminophenyl groups as novel N-1 substituents of naphthyridones and quinolones. Among newly synthesized compounds, 7-(3-aminoazetidin-1-yl)-1-(5-amino-2,4-difluorophenyl)-8-chloro-6-fluoro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (4) has extremely potent antibacterial activities against Gram (+) as well as Gram (-) bacteria. This compound is significantly more potent than trovafloxacin against clinical isolates: 30 times against Streptococcus pneumoniae and 128 times against methicillin resistant Staphylococcus aureus. The structure-activity relationship (SAR) study revealed that a limited combination of 1-(5-amino-2,4-difluorophenyl) group, 7-(azetidin-1-yl) group, and 8-Cl atom (or Br atom or Me group) gave potent antibacterial activity. An X-ray crystallographic study of a 7-(3-ethylaminoazetidin-1-yl)-8-chloro derivative demonstrated that the N-1 aromatic group was remarkably distorted out of the core quinolone plane by steric repulsion between the C-8 Cl atom and the N-1 substituent. Furthermore, a molecular modeling study of 4 and its analogues demonstrated that a highly distorted orientation was induced by a steric hindrance of the C-8 substituent, such as Cl, Br, or a methyl group. Thus, their highly strained conformation should be a key factor for the potent antibacterial activity.

Community-acquired lower respiratory tract infections: etiology and treatment

The current therapy for community-acquired lower respiratory tract infections is often empiric, usually involving administration of a beta-lactam or macrolide. However, the increasing prevalence of antibiotic resistance in frequently isolated respiratory tract pathogens has complicated the antimicrobial selection process. This review will discuss the incidence of various respiratory pathogens, as well as update the clinician on the various antimicrobial alternatives available, with particular emphasis on the role of the newer fluoroquinolones in the treatment of acute exacerbations of chronic bronchitis and community-acquired pneumonia.

Antibacterial activities and pharmacokinetics of E-4767 and E-5065, two new 8-chlorofluoroquinolones with a 7-azetidin ring substituent

E-4767 [(-)-7-[3-(R)-amino-2-(S)-methyl-1-azetidinyl]-8-chloro-1-cyclopropyl-1,4-dihydro-6-fluoro-4-oxo-3-quinolinecarboxylic acid] and E-5065 [(-)-7-(3-amino-1-azetidinyl)-8-chloro-1-cyclopropyl-1,4-dihydro-6-fluoro-4-oxo-3-quinolinecarboxylic acid] are two new chlorofluoroquinolones with an azetidine moiety at position 7. Their in vitro activities were evaluated in comparison with those of ciprofloxacin, ofloxacin, fleroxacin, and tosufloxacin, while ciprofloxacin was used as a reference for in vivo studies. Against gram-positive organisms, E-4767 and E-5065 were, in general, eight- and fourfold more active than tosufloxacin, which is the most potent of the reference compounds. E-4767 and E-5065 were also more potent than the reference compounds against all species of enteric bacteria tested. The MICs of E-4767 and E-5065 at which 90% of the isolates tested were inhibited (MIC(90)s) were 0.007 to 0.5 microg/ml and 0.03 to 2 microg/ml, respectively, for gram-positive organisms and <or=0.003 to 0.06 microg/ml and 0.007 to 0.12 microg/ml, respectively, for members of the family Enterobacteriaceae except Serratia marcescens and Providencia spp. (MIC(90)s of E-4767 and E-5065 for these species were <or=0.5 microg/ml and <or=2 microg/ml, respectively). For Pseudomonas aeruginosa both compounds had a MIC(90) of 0.5 microg/ml. E-4767 and E-5065 were 356- and 32-fold more potent than ciprofloxacin against Bacteroides spp., and their MIC(90)s for Clostridium spp. were 0.25 and 0.5 microg/ml, respectively. Both products showed a remarkable reduction of activity when the pH was below 4.8 and, in general, were less active in the presence of 5 or 10 mM Mg(2+). The presence of horse serum or human urine (pH 7.2) decreased the activity of E-4767 and E-5065 only two- to fourfold more than the activity observed in broth. After an oral dose of 50 mg/kg of body weight, the maximum levels in serum (the maximum concentration of drug in serum was reached 30 min postadministration) of E-4767 and E-5065 were approximately threefold higher than that of ciprofloxacin. The area under the concentration-time curve from 0 to 4 h for ciprofloxacin was about two- and fourfold lower than that for E-4767 and E-5065, respectively. These two new chlorofluoroquinolones were as effective as or more effective than ciprofloxacin against all experimental infections evaluated, not only against gram-negative bacteria, such as Escherichia coli or P. aeruginosa, but also against gram-positive pathogens, such as Staphylococcus aureus or Streptococcus pneumoniae. E-4767 was the most effective compound, with a 50% effective dose (ED(50)) of <or=17 mg/kg for all strains tested except ciprofloxacin-resistant S. aureus strains. The ED(50) of E-4767 for these strains was <or=47.5 mg/kg. Against gram-positive experimental infections, the ED(50) values of E-4767 were 3- to 14-fold lower than those of E-5065 and up to 25 times lower than those of ciprofloxacin.

Comparative in vitro bacteriostatic and bactericidal activity of trovafloxacin, levofloxacin and moxifloxacin against clinical and environmental isolates of Legionella spp

The susceptibility of 140 Legionella spp isolates (106 clinical and 34 environmental isolates) to trovafloxacin (TRFX), levofloxacin (LEVX), moxifloxacin (MOFX), ciprofloxacin (CIPX), ofloxacin (OFLX), erythromycin (ERY), azithromycin (AZI) and rifampicin (RIF) was studied using a standard microdilution method and buffered yeast extract broth (BYE) supplemented with 0.1% alpha-ketoglutarate. The post-antibiotic effects (PAEs) of the study drugs against 10 clinical isolates of Legionella pneumophila sg.1 were compared. The MIC inhibiting 90% of strains tested on BYEalpha broth were 0.008, 0.016, 0.016, 0.06, 0.125, 0.5, 0.5, and 0.004 mg/l for TRFX, LEVX, MOXX, CIP, OFLX, ERY, AZI, and RIF, respectively. The MBC/MIC ratios ranged from one to eight depending on the antibiotic tested: TRFX [1x-2 x MIC], LEVX, MOFX, CIPX and OFLX [1x-4 x MIC], RIF [2x-4 x MIC], ERY and AZI [2x-8 x MIC]. TRFX, RIF, LEVX, MOFX, CIPX, OFLX, ERY and AZI showed similar activity against Legionella species other than L. pneumophila. One-hour exposures to the study antimicrobial agents at a concentration of 4 x MIC resulted in PAEs as follows (average in hours): TRFX: 2.68 h; RIF: 2.63 h; CIPX: 2.62 h; MOFX: 2.56 h; LEVX: 2.41 h; OFLX: 2.25 h; AZI: 1.65 h; and ERY: 1.54 h. In conclusion, our in vitro data confirm that trovafloxacin, levofloxacin, moxifloxacin and rifampicin have excellent bacteriostatic and bactericidal activity against Legionella spp and show significant post-antibiotic effect.

Pharmacokinetics of a fluoronaphthyridone, trovafloxacin (CP 99,219), in infants and children following administration of a single intravenous dose of alatrofloxacin

The pharmacokinetics of trovafloxacin following administration of a single intravenous dose of alatrofloxacin, equivalent to 4 mg of trovafloxacin per kg of body weight, were determined in 6 infants (ages 3 to 12 months) and 14 children (ages, 2 to 12 years). There was rapid conversion of alatrofloxacin to trovafloxacin, with an average +/- standard deviation (SD) peak trovafloxacin concentration determined at the end of the infusion of 4.3 +/- 1.4 microg/ml. The primary pharmacokinetic parameters (average +/- SD) analyzed were volume of distribution at steady state (1.6 +/- 0.6 liters/kg), clearance (151 +/- 82 ml/h/kg), and half-life (9.8 +/- 2.9 h). The drug was well tolerated by all children. There were no age-related differences in any of the pharmacokinetic parameters studied. Less than 5% of the administered dose was excreted in the urine over 24 h. On the basis of the mean area under the concentration-time curve of 30.5 +/- 10.1 microg. h/ml and the susceptibility (< or =0.5 microg/ml) of common pediatric bacterial pathogens to trovafloxacin, dosing of 4 mg/kg/day once or twice daily should be appropriate.

Calibration of the disk diffusion test for trovafloxacin susceptibility testing of four anaerobic species

OBJECTIVES

To study trovafloxacin susceptibility among clinical isolates of four anaerobic bacterial species using minimum inhibitory concentrations (MIC) determinations, E test assays and disk diffusion test results and to calibrate the disk diffusion method for these species using single strain regression analysis (SRA).

METHODS

One-hundred and eighty-seven clinical isolates of four anaerobic bacterial species were included. Trovafloxacin MIC determinations were performed using the agar dilution technique and MIC estimations using the E test. The disk diffusion test was performed according to Swedish Reference Group for Antibiotics standardization. NCCLS limits for susceptibility categories were applied. SRA was performed using 1, 3, 10, 30, and 100 microg trovafloxacin disk contents and ATCC control strains. The regression lines obtained permitted the calculation of zone equivalents to MIC limits as well as an evaluation of various disk potencies.

RESULTS

Trovafloxacin susceptibility (S + I) was noted in 98.9, 100, 100, and 97% of Bacteroides fragilis, Bacteroides thetaiotaomicron, Clostridium perfringens, and Peptostreptococcus magnus strains, respectively, as judged by MIC determinations. Agar dilution and E test estimations gave the same results, but E test values were consistently lower than MIC values by the reference method. Regression lines calculated for the four species using SRA showed different equation constants indicating species-related differences. Interpretive zone diameter breakpoints were calculated for the four species and used for the interpretation of susceptibility.

CONCLUSIONS

The disk diffusion test was successfully calibrated for trovafloxacin susceptibility testing of four anaerobic species using single strain regression analysis, SRA. There was a good agreement between the results of MIC-tests and disk testing. Interpretive errors of type I are prone to occur among Bacteroides isolates and might require species-related MIC limits. SRA calculations permitted the testing of the effect of different disk potencies on inhibition zones produced at the interpretive MIC limits. Criteria for the selection of a minimal disk content showed that 5 microg trovafloxacin is sufficient, but a 10 microg disk will safeguard against residual laboratory variation without producing too large inhibition zones for very susceptible strains.

A comparison of the photosensitizing potential of trovafloxacin with that of other quinolones in healthy subjects

Treatment with some quinolones is associated with an abnormal skin reaction following exposure to sunlight (photosensitivity). The objective of the current study was to compare the photosensitizing potential of a new quinolone, trovafloxacin, with that of ciprofloxacin, lomefloxacin and placebo. Forty-eight healthy males (age range 19-45 years) were randomized to receive a 7 day course of treatment with: (i) trovafloxacin 200 mg od; (ii) ciprofloxacin 500 mg bd; (iii) lomefloxacin 400 mg od; or (iv) placebo bd. Minimal erythema doses (MEDs) were assessed using a monochromator at baseline and on day 5 of treatment, for wavelengths of 305 +/- 5, 335 +/- 30, 365 +/- 30, 400 +/- 30 and 430 +/- 30 nm; 335 +/- 30 and 365 +/- 30 nm are within the UVA range. Immediate reaction MEDs were similar in all treatment groups. However, between baseline and day 5, the mean decreases in delayed-reaction MED (24 h) at 335 +/- 30 nm were only 18.99% for trovafloxacin versus placebo (P = 0.1267), compared with 53.77% (P 0.0001) and 64.13% (P 0.0001) for ciprofloxacin and lomefloxacin, respectively. Similarly, at 365 +/- 30 nm, trovafloxacin produced the smallest reduction in delayed MED versus placebo (43.66%), compared with ciprofloxacin (61.53%) and lomefloxacin (75.81%). These differences between trovafloxacin and ciprofloxacin and lomefloxacin were significant at both 335 +/- 30 and 365 +/- 30 nm (P 0.029). All MED values returned to baseline levels within 2 days of drug cessation. These results show that trovafloxacin has significantly less photosensitizing potential than either ciprofloxacin or lomefloxacin. This photosensitivity appears to be induced only by wavelengths in the UVA region, is maximal at 24 h and is a short-term effect.

Plasmid curing effect of trovafloxacin

The effect of sub-inhibitory concentrations of trovafloxacin, a recently developed fluoroquinolone molecule, on the capability of Escherichia coli cells to maintain three different types of plasmids has been investigated by a number of approaches, including the quantification of the loss of plasmid-borne functions and of plasmid DNA by quantitative PCR. The results obtained demonstrate that at concentrations ranging from the MIC to 1/8 of the MIC, trovafloxacin induces a clear, albeit incomplete, 'episome-curing' effect which was observed with plasmids differing in copy number, size and nature of the replication origin of the episome. This effect was most likely not due to an alteration of DNA supercoiling.

Trovafloxacin susceptibility of aerobic clinical bacterial isolates from Sweden

Trovafloxacin susceptibility was studied in aerobic clinical isolates of bacterial pathogens from 5 microbiology laboratories in Sweden. Trovafloxacin and ciprofloxacin minimum inhibitory concentration (MIC) determinations were performed on 474 clinical isolates. Disk diffusion tests using trovafloxacin and ciprofloxacin 10 microg disks were performed on a total of 7142 clinical isolates (trovafloxacin). Susceptibility interpretations for trovafloxacin and ciprofloxacin were determined from MIC values and disk diffusion tests using species-related MIC-limits and zone diameter breakpoints. Eight of 12 gram-positive species groups were fully susceptible to trovafloxacin as judged by MIC tests. Trovafloxacin gave MIC50 values of 0.032 mg/l for S. aureus, 1.0 mg/l for MRSA, 0.064 mg/l for coagulase negative staphylococci, 1.0 mg/l for MRSE, 0.064 mg/l for S. saprophyticus, 0.125 mg/l for group A and group B streptococci, 0.064 mg/l for group C and G streptococci and S. pneumoniae, 0.25 mg/l for E. faecalis, and 16.0 mg/l for E. faecium. These MIC values were 4-16-fold lower than those of ciprofloxacin. Both MIC and disk tests showed similar levels of susceptibility among gram-negative isolates for trovafloxacin and ciprofloxacin. For most gram-negative species the trovafloxacin MIC50 values were similar to or slightly higher than those for ciprofloxacin. Trovafloxacin MIC values were much lower for Acinetobacter strains, but higher for P. mirabilis compared with ciprofloxacin. The favourable susceptibility levels of Swedish aerobic pathogens to trovafloxacin emphasize the potential of this drug for the treatment of serious infections.

Calibration of disk diffusion antibiotic susceptibility testing: species-related trovafloxacin interpretive zone breakpoints and selection of disk potency

International comparisons of antibiotic susceptibility require the use of common minimum inhibitory concentration (MIC) limits. Disk diffusion test results are not directly suitable for such comparisons, since different standards are often used and zone breakpoints issued might reflect different MIC limits. We have used single strain regression analysis (SRA) for the calibration of the disk test, both according to species and individual laboratory, and for quality control of trovafloxacin disk diffusion tests in 5 laboratories in Sweden. Preliminary controls using histogram analysis including subtraction histograms of reference strains revealed marked differences between different laboratories. SRA was performed on 4 reference strains, S. aureus, E. faecalis, E. coli and P. aeruginosa, using disks containing 1, 3, 10, 30 and 100 microg trovafloxacin. The results using SRA showed a difference between laboratories using Biodisk PDM medium, which produced smaller zones, and those using Oxoid IsoSensitest. Species-related regression lines for laboratories using either medium were calculated and corresponding interpretive zone breakpoints determined for MIC limits. Rational criteria for the selection of a suitable disk content of an antibiotic were also defined and applied to trovafloxacin. The 10 microg disk selected by NCCLS (National Committee for Clinical Laboratory Standards) proved optimal.

Trovafloxacin concentrations in airway fluids of patients with severe community-acquired pneumonia

The penetration of trovafloxacin (TVA), 200 mg once daily, into the airways of 17 patients with severe pneumonia was studied. The mean (standard deviations are given in parentheses) steady-state TVA concentrations, 2 h after the last intake, were 3.1 (0.3) mg/liter in induced sputum (n = 8), 3.2 (1.1) mg/liter in bronchial secretions (n = 9), 3.2 (0.9) mg/liter in bronchoalveolar lavage fluid (n = 10), and 4.9 (1.4) mg/liter in epithelial lining fluid (n = 11).

Recent progress in novel macrolides, quinolones, and 2-pyridones to overcome bacterial resistance

Macrolides, such as clarithromycin and azithromycin, having good activity against pathogens such as Legionella, Chlamydia, Campylobacter spp, Branhamella spp, Pasteurella multocida and streptococci, have gained wide acceptance for the treatment of both upper and lower respiratory tracts, as well as cutaneous infections. Emergence of bacterial resistance, particularly in gram-positive bacteria, has been observed. Macrolide-resistant Streptococcus pneumoniae and S. pyogenes are found in France and many other countries, resulting in failure of therapy for pneumonia, pharyngitis, and skin infection. RU 004, HMR 3647, and TE 802 were reported to be active against these resistant strains. Research at Abbott produced several macrolide derivatives in the anhydrolide, tricyclic and tetracyclic ketolides as well as 6-O-alkyl ketolides series having potent activity against macrolide resistant S. pyogenes and S. pneumoniae. Research on streptogramins to overcome bacterial resistance in gram-positive bacteria has produced interesting compounds. Another class of antibacterial agent called quinolones is useful for the treatment of bacterial infections of respiratory tract, urinary tract, skin and soft tissues, as well as sexually transmitted diseases. Ciprofloxacin, the market leader, however, has low potency against anaerobes. Bacterial resistance ( such as Pseudomonas aeruginosa and methicillin- resistant Staphylococcus aureus ) to ciprofloxacin is increasing rapidly. Many quinolone compounds are being synthesized to address these drawbacks. The new quinolones currently under development are characterized by enhanced activities against streptococci, staphylococci, enterococci, and anaerobes. This presentation reviews the current research in the identification of agents to overcome the macrolide and quinolone resistance.

Double-blind comparison of trovafloxacin and doxycycline in the treatment of uncomplicated Chlamydial urethritis and cervicitis. Trovafloxacin Chlamydial Urethritis/Cervicitis Study Group

BACKGROUND

Chlamydia trachomatis is among the most common sexually transmitted bacteria worldwide. With excellent activity against C. trachomatis and Neisseria gonorrhoeae and prolonged elimination half-life allowing once-daily dosage, the fluoroquinolone trovafloxacin has potential advantages in the treatment of uncomplicated chlamydial infection.

GOAL OF THIS STUDY

This study compared the efficacy of trovafloxacin with that of doxycycline for the treatment of uncomplicated chlamydial infection.

STUDY DESIGN

In a double-blind, multicenter trial, trovafloxacin 200 mg was administered once daily for 5 days and doxycycline 100 mg was administered twice daily for 7 days to patients with uncomplicated chlamydial urethritis or cervicitis. Follow-up visits were conducted 10, 21, and 35 days after enrollment.

RESULTS

Of the 970 patients (403 men, 567 women) observed, 511 were microbiologically evaluable and 360 were clinically evaluable. C. trachomatis eradication rates in the trovafloxacin and doxycycline groups were equivalent in women (95% and 97%, respectively), but not in men (89% and 99%). Similarly, rates of clinical success (cure plus improvement) demonstrated equivalence of trovafloxacin and doxycycline in women (96% and 94%), but not in men (94% and 100%). The most frequent treatment-related adverse events were dizziness, nausea, and headache in patients given trovafloxacin, and nausea, vomiting, and headache in patients given doxycycline. Treatment-related discontinuations were comparable between the drug groups.

CONCLUSION

Trovafloxacin given once daily for 5 days was clinically and bacteriologically equivalent to doxycycline given twice daily for 7 days in women with uncomplicated chlamydial cervicitis. This equivalence was not demonstrated in men with uncomplicated chlamydial urethritis.

Antimicrobial activity evaluations of gatifloxacin, a new fluoroquinolone: contemporary pathogen results from a global antimicrobial resistance surveillance program (SENTRY, 1997)

OBJECTIVE: To investigate the in vitro potency and spectrum of activity of gatifloxacin and five comparator fluoroquinolones tested against over 23 000 clinical isolates from diverse geographic and clinical sources in the Americas. METHODS: Gram-negative, Gram-positive and fastidious bacterial isolates were tested against gatifloxacin, ciprofloxacin, levofloxacin, ofloxacin, sparfloxacin and trovafloxacin using broth microdilution methods recommended by the National Committee for Clinical Laboratory Standards (NCCLS). RESULTS: Gatifloxacin demonstrated a potency and spectrum very similar to those of other new fluoroquinolones such as levofloxacin, sparfloxacin, and trovafloxacin. Gatifloxacin was particularly active against the Enterobacteriaceae (94.8% susceptible at </=2 mg/L), Acinetobacter spp. (77.2%), Stenotrophomonas maltophilia (75.1%), Streptococcus pneumoniae (99.8%), other Streptococcus spp. (>/=98.9%), and various Staphylococcus spp. (79.2-100.0%). Trovafloxacin was the most similar comparison drug overall. CONCLUSIONS: These results indicate a potential therapeutic role for gatifloxacin that would widen the potency or spectrum of fluoroquinolones, particularly against Gram-positive species, when considering its favorable bioavailability.

Comparative efficacies of levofloxacin and ciprofloxacin against Streptococcus pneumoniae in a mouse model of experimental septicaemia

The in vivo efficacies of levofloxacin and ciprofloxacin were compared against three clinical isolates of Streptococcus pneumoniae, using a mouse protection model. Two strains (SP 22 and SP 28) were penicillin-sensitive while one strain (SP 46) was penicillin-resistant. Each strain had identical susceptibility to both drugs. Using mice with renal impairment induced by uranyl nitrate injection, the elimination half-life of each antibiotic was prolonged to approximate human pharmacokinetic profiles of the drugs. The dosing regimen of each drug that yielded serum levels in mice which mimic human therapeutic concentrations of the drugs, were designed. One hour after intraperitoneal inoculation with minimum lethal dose of each strain, either levofloxacin at a dosing regimen of 10.6 mg/kg every 8 h or ciprofloxacin at 9.5 mg/kg every 8 h was subcutaneously administered for a total of six or 15 doses. In treatment, monitored daily for 5-8 days, levofloxacin resulted in higher survival compared with ciprofloxacin for the three strains. For example, percent survival following levofloxacin treatment recorded at day 4 postinfection with SP 22, SP 28 and SP 46 were 41, 90 and 30%, respectively, while the corresponding values after ciprofloxacin treatment were 27, 75 and 16%, respectively. However, statistical analysis did not reveal a significant difference (p > 0.05). The lack of significant difference observed in the efficacies of both drugs reflected the comparability of their 24-h AUC/MIC ratios. It is suggested that, with some strains of S. pneumoniae, the efficacy of levofloxacin may be equivalent to that of ciprofloxacin in the treatment of systemic pneumococcal infections caused by susceptible strains of the organism.

Selection of resistant variants of respiratory pathogens by quinolones

Quinolones are widely used in the treatment of respiratory tract infections. However, some disquiet has been expressed over using quinolones for community-acquired pneumonia since their activity is generally rather poor against Streptococcus pneumoniae. In addition, it is known that resistant variants emerge at a fairly high frequency during exposure of Enterobacteriaceae to quinolones; if this also occurred during quinolone treatment of community-acquired pneumonia it could lead to an increased risk of clinical failure. We therefore determined the selection rate of quinolone-resistant variants for six strains of S. pneumoniae, Haemophilus influenzae and Moraxella catarrhalis with nalidixic acid (except for S. pneumoniae), ciprofloxacin, ofloxacin and levofloxacin. We were only able to select resistant variants at low frequency from two of the six strains of S. pneumoniae with ciprofloxacin: no resistant variants were selected by either ofloxacin or levofloxacin. Variants of H. influenzae and M. catarrhalis with decreased susceptibility to quinolones were produced both with more strains and with a greater frequency; however, these variants still remained susceptible according to the NCCLS guidelines. Our study suggests that resistant variants of S. pneumoniae are relatively unlikely to occur in individuals treated with fluoroquinolones especially if they are given quinolones with enhanced anti-gram-positive activity compared to ciprofloxacin.

Trovafloxacin in combination with vancomycin against penicillin-resistant pneumococci in the rabbit meningitis model

Trovafloxacin, a new fluoroquinolone, produced bactericidal activity (-0.33 +/- 0.13 delta log10 CFU/ml.h; intravenously [i.v.] administered dose, 15 mg/kg) comparable to that of vancomycin (-0.39 +/- 0.18 delta log10 CFU/ml.h; i.v. admininistered dose, 20 mg/kg) in the treatment of experimental meningitis in rabbits due to a pneumococcal strain highly resistant to penicillin (MIC of penicillin G, 4 micrograms/ml). The combination of both drugs significantly increased (P < 0.05) the killing rate (-0.60 +/- 0.23 delta log10 CFU/ml.h) compared to that produced by either monotherapy. These results were also confirmed in vitro.

Epidemiologic trends in nosocomial and community-acquired infections due to antibiotic-resistant gram-positive bacteria: the role of streptogramins and other newer compounds

The Gram-positive cocci have clearly re-emerged as important pathogens world-wide in the past two decades. Staphylococci, including the coagulase-negative staphylococci and Staphylococcus aureus, and the enterococci account for approximately one-third of all blood stream infections and as much as 50% of nosocomial blood stream infections. Although Streptococcus pneumoniae is often considered a community-acquired pathogen, it is also an important cause of nosocomial infection. The hallmark of these Gram-positive pathogens is increasing resistance to available antimicrobial agents. Of particular note is resistance to glycopeptides (vancomycin and teicoplanin), aminoglycosides (high-level), and penicillins among the enterococci (especially E. faecium), resistance to penicillinase-resistant penicillins (oxacillin and methicillin) and fluoroquinolones (ciprofloxacin and ofloxacin) among staphylococci, and resistance to penicillin, other beta-lactams and macrolides among the pneumococci. The recent detection of decreased susceptibility to vancomycin among S. aureus is also quite ominous. In many instances the ability of the clinical laboratory to accurately characterize these resistant isolates is suboptimal, further compounding the problem. Increased understanding of resistance mechanisms and correlations of resistance genes with the phenotypic expression of resistance has allowed for modifications and improvements of reference susceptibility tests and interpretive breakpoints. New compounds for effective therapy of infection with multi-resistant Gram-positive species are clearly needed. To this end, the streptogramin combination, quinupristin/dalfopristin, has demonstrated significant activity against oxacillin-resistant staphylococci, penicillin-resistant streptococci, and vancomycin-resistant E. faecium. Other candidate drugs including Gram-positive active fluoroquinolones (clinafloxacin, grepafloxacin, moxifloxacin, gatifloxacin, and trovafloxacin) and novel compounds such as the everninomicin derivatives (SCH27899), ketolides, and oxazolidinones (linezolid) have been shown to be active against these organisms and are under rapid clinical development.

Trovafloxacin: a new fluoroquinolone

OBJECTIVE

To review the pharmacology, antimicrobial activity, pharmacokinetics, clinical efficacy, and safety of trovafloxacin.

DATA SOURCES

A MEDLINE search (January 1966-April 1998) was conducted for relevant literature using the terms CP-99,219, CP-116,519, trovafloxacin, and alatrofloxacin. Abstracts published by the American Society of Microbiology during 1995-1997 meetings were also reviewed.

STUDY SELECTION AND DATA EXTRACTION

All in vitro, animal, and human studies were reviewed for the antimicrobial activity, pharmacokinetics, efficacy, and safety of trovafloxacin.

DATA SYNTHESIS

Trovafloxacin is a new fluoroquinolone with enhanced activity against gram-positive and anaerobic microorganisms. The oral bioavailability under fasting conditions is approximately 88%. The elimination half-life of trovafloxacin is approximately 10 hours. Less than 10% of trovafloxacin is eliminated unchanged in the urine. Trovafloxacin is effective in the treatment of community-acquired pneumonia and nosocomial pneumonia with cure rates of > 90% and 77%, respectively. Trovafloxacin is comparable with ceftriaxone in the treatment of meningococcal meningitis in children; each produces a cure rate of approximately 90%. In treatment of uncomplicated urinary tract infection, both ciprofloxacin and trovafloxacin achieve an eradication rate of > or = 93%. Trovafloxacin is similar to ofloxacin in the treatment of urogenital Chlamydia trachomatis and acute exacerbations of chronic bronchitis, with clinical success in 97% of patients with each drug. The common adverse effects of trovafloxacin include dizziness, headache, and gastrointestinal intolerance.

CONCLUSIONS

The advantages of once-daily dosing and enhanced activity of trovafloxacin against gram-positive and anaerobic organisms may expand its use over available fluoroquinolones. Further studies are needed to define its role in the treatment of various infectious diseases.

Pharmacodynamics and microbiology of trovafloxacin in animal models of surgical infection

Trovafloxacin provides broad in vitro and in vivo coverage of the aerobic and anaerobic pathogens found frequently in surgical infections. In vitro susceptibility testing indicated that trovafloxacin inhibited gram-positive staphylococci and enterococci, numerous gram-negative organisms, including Escherichia coli, and anaerobic pathogens, such as Bacteroides fragilis. Trovafloxacin protected mice from lethal infections induced by gram-negative or gram-positive organisms, even when these organisms were inoculated in combination with B. fragilis. Trovafloxacin protected rats in models of intra-abdominal sepsis induced by inoculation with E. coli and B. fragilis or with multiple aerobic and anaerobic pathogens. In these experimental models, trovafloxacin protected rats from lethal infection, reduced intra-abdominal abscess formation, and inhibited bacterial growth. Drug concentrations were greater in intra-abdominal abscesses than in serum, reflecting the good tissue penetration of trovafloxacin. These results indicate that trovafloxacin may be effective in prophylaxis and treatment of mixed infections in surgical patients.

Overview of quinolones in the treatment and prevention of surgical infection

Postoperative infection remains a complication of surgical procedures, resulting in increased morbidity, mortality, and cost. The frequent polymicrobial etiology and emerging patterns of resistance continue to compromise cure rates. Although quinolones have many attractive properties for the surgical setting, combination therapy is routinely indicated for appropriate coverage. Advanced-generation quinolones, such as trovafloxacin, offer an increased antimicrobial spectrum, including activity against important surgical pathogens, and longer elimination half-lives. These newer agents may be used intravenously or orally as once-daily single-agent therapy for surgical prophylaxis, and in place of combination therapy for complex intra-abdominal and pelvic infections.

The bioavailability of nasogastric versus tablet-form oral trovafloxacin in healthy subjects

BACKGROUND

Patients in the hospital, as well as those in home care settings, often require nutritional supplementation with enteral feeding solutions. In addition, patients with serious infections who are clinically unstable often cannot maintain adequate intake by mouth and may require an alternative to oral antibiotic administration. However, delivery of crushed oral formulations of drugs via nasogastric tubes is often carried out without adequate bioavailability data, and this method of administration may not always be equivalent to oral drug delivery.

METHODS

In an open-label, randomized, four-period, four-treatment, cross-over study, 24 healthy volunteers were given one dose of each of the following treatments, with a 7-day wash-out between dosing periods: Treatment A: two 100-mg trovafloxacin tablets given orally with 240 mL water; Treatment B: two crushed 100-mg trovafloxacin tablets suspended in water and administered through a nasogastric tube into the stomach; Treatment C: two crushed 100-mg trovafloxacin tablets suspended in water and administered through a nasogastric tube into the duodenum; or Treatment D: two crushed 100-mg trovafloxacin tablets suspended in water and given through a nasogastric tube into the stomach concomitantly with an enteral feeding solution (240 mL full-strength Osmolite).

RESULTS

Pharmacokinetic analyses showed that the bioavailability of trovafloxacin after administration of crushed tablets into the stomach with or without concomitant enteral feeding was not significantly different from that of the orally administered whole tablets: the 90% confidence limits of the area under the concentration-time curve (AUC(0-infinity)) for Treatment B versus Treatment A (91.3%, 109.5%) and Treatment D versus Treatment A (91.6%, 109.9%) were well within the bioequivalence criteria of 80% to 125%. Results of analysis of variance (ANOVA) indicated no significant sequence, period, or treatment-by-period interaction effects. Administration of trovafloxacin into the duodenum (Treatment C) resulted in reduced systemic exposure to trovafloxacin, with a 31% decrease in AUC(0-infinity) and a 30% decrease in peak serum concentration (Cmax) compared to oral administration. Time to peak serum concentration (Tmax) was 1.7 hours after oral administration of trovafloxacin and 1.1 hours after administration directly into the stomach or duodenum through a nasogastric tube in the absence of concomitant enteral feeding. All four treatments were well tolerated; no participant discontinued the study due to adverse events and no serious adverse events were reported.

CONCLUSIONS

These results showed that administration of crushed trovafloxacin tablets through a nasogastric tube into the stomach, with or without concomitant enteral feeding, achieves absorption and tolerability comparable to those of orally administered trovafloxacin tablets.

Comparative in-vitro activities of trovafloxacin, ciproflaxacin, ofloxacin, and broad-spectrum beta-lactams against aerobe blood culture isolates

The in vitro activity of trovafloxacin, a new fluoroquinolone, was compared with that of ciprofloxacin, ofloxacin, fleroxacin, ceftazidime, piperacillin/tazobactam, and meropenem against 613 consecutively recovered blood isolates from recently hospitalized patients. Susceptibility testing was performed by agar dilution according to NCCLS guidelines. Test strains included Acinetobacter species (n = 26), Escherichia coli (n = 137), Enterobacter species (n = 27), Klebsiella species (n = 42), Proteus species (n = 16), Pseudomonas aeruginosa (n = 28), Serratia marcescens (n = 13), Stenotrophomonas maltophilia (n = 7), enterococci (n = 54), coagulase-negative staphylococci (n = 38), Staphylococcus aureus (n = 137), Streptococcus pneumoniae (n = 27), beta-haemolytic streptococci (n = 13), and viridans group streptococci (n = 48). The overall respective MICs at which 50% and 90% of isolates were inhibited (MIC50s and MIC90s) were as follows: trovafloxacin, 0.06 and 1 mg/l; ciprofloxacin, 0.25 and 4 mg/l; ofloxacin, 0.5 and 4 mg/l; fleroxacin, 0.5 and 16 mg/l; ceftazidime, 2 and 128 mg/l; piperacillin/tazobactam, 2 and 8 mg/l; meropenem, 0.06 and 4 mg/l. For the quinolones, the rank order of activity against gram-negative microorganisms was ciprofloxacin > trovafloxacin > ofloxacin = fleroxacin, against gram-positive organisms, trovafloxacin > ciprofloxacin = ofloxacin > fleroxacin. Data obtained showed the similar activity of trovafloxacin and ciprofloxacin against gram-negative pathogens and the superior activity of trovafloxacin against gram-positive bacteria thus making it a potential candidate for the empiric treatment of patients with suspected bacteremia and sepsis.

Pharmacokinetics and metabolism of single oral doses of trovafloxacin

Trovafloxacin, a new fluoronaphthyridone derivative related to fluoroquinolone antimicrobial drugs, has demonstrated the following characteristics: significant gram-positive and gram-negative activity; significant activity against anaerobes and atypical respiratory pathogens; approximately 11-hour elimination half-life, permitting once-daily administration; and good tissue penetration. Because <10% of an orally administered dose is recovered in urine as unchanged drug, the predominant route of trovafloxacin elimination appears to be nonrenal. The two studies described in this review examined the metabolism and excretion of trovafloxacin and compared the time course and concentrations of trovafloxacin and its metabolites in bile to those in serum. In the first study, four healthy male volunteers received a single, oral 200-mg dose of radiolabeled trovafloxacin. In the second study, three patients with indwelling nasobiliary tubes received a single 200-mg dose of trovafloxacin. Samples of blood, urine, bile, and feces were collected. Trovafloxacin in urine and serum was analyzed by high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection and in bile by HPLC-mass spectroscopy (MS). Levels of the N-acetyl metabolite in bile were determined by HPLC/UV/MS. Metabolites in serum, urine, and feces were determined by reverse-phase HPLC/MS, and radioactivity in these samples was assayed by liquid scintillation counting. In the first study, 63.3% and 23.1% of total radioactivity were recovered in feces and urine, respectively, with most of the radioactivity in urine in the form of the ester glucuronide metabolite (12.8%) and unchanged trovafloxacin (5.9%). Unchanged drug, the N-acetyl metabolite, and the N-sulfate of trovafloxacin accounted for 43.2%, 9.2%, and 3.9%, respectively, of the radioactivity in feces. In the second study, biliary trovafloxacin concentrations were highest between 1.5 and 10 hours postdose, and the maximum concentrations ranged from 18.9 to 37.9 microg/mL. The mean bile:serum ratio of trovafloxacin was 14.9, and the biliary concentration of parent drug was higher than that of its N-acetyl metabolite. In both studies, trovafloxacin was well tolerated, with no discontinuations due to adverse events. The pharmacokinetic profile of trovafloxacin in serum was consistent in healthy subjects and in individuals who had undergone recent hepatobiliary surgery. Trovafloxacin is metabolized primarily by the liver, through phase II metabolism (glucuronidation 13.2%, N-acetylation 10.4%, and N-sulfoconjugation 4.1%); minimal oxidative metabolism was detected. Renal elimination accounted for <10% of the administered dose. The high bile to serum ratio and higher trovafloxacin concentrations relative to metabolite concentrations are consistent with nonrenal elimination. These pharmacokinetic and pharmacodynamic results, together with a broad antimicrobial spectrum, long 11-hour elimination half-life, and low drug-interaction potential, suggest that trovafloxacin may be particularly appropriate for use in the surgical setting.

Concentrations of trovafloxacin in colonic tissue and peritoneal fluid after intravenous infusion of the prodrug alatrofloxacin in patients undergoing colorectal surgery

BACKGROUND

Trovafloxacin is a new fourth-generation fluoroquinolone whose pharmacokinetics and in vitro activity suggest that it is well suited for antibiotic prophylaxis in elective colorectal surgery. Alatrofloxacin is a prodrug that is rapidly hydrolyzed to trovafloxacin in the body.

METHODS

Twelve patients received a single dose of alatrofloxacin equivalent to 200 mg trovafloxacin by intravenous infusion over 1 hour. Surgery was started at various time points relative to infusion time to allow determination of trovafloxacin concentrations in serum, colonic tissue, and peritoneal fluid as a function of time.

RESULTS

The concentration in the earliest colonic tissue sample (1.4 hours after dosing) was 1.4 microg/g. The maximum colonic tissue concentration was 2.8 microg/g in a sample taken 2 hours after dosing. Colonic tissue/serum concentration ratios in samples taken 2-10 hours after the end of infusion ranged from 0.8 to 1.47. Concentrations of trovafloxacin in peritoneal fluid ranged from below the level of quantitation to 2.1 microg/mL at the time of colonic tissue sampling and from below the level of quantitation to 2.5 microg/mL at the time of wound closure. Alatrofloxacin was well tolerated.

CONCLUSIONS

After a single intravenous dose of alatrofloxacin equivalent to 200 mg trovafloxacin, trovafloxacin is distributed rapidly into colonic tissue and peritoneal fluids. Tissue concentrations approximate serum concentrations and decline in parallel for up to 10 hours after dosing.

Oral trovafloxacin compared with intravenous cefoxitin in the prevention of bacterial infection after elective vaginal or abdominal hysterectomy for nonmalignant disease. Trovafloxacin Surgical Group

BACKGROUND

Trovafloxacin is a new fourth-generation fluoroquinolone whose pharmacokinetics and in vitro activity suggest that it is well suited for antibiotic prophylaxis in elective hysterectomy.

METHODS

In a randomized, double-blind, multicenter study, parallel groups of women 18 years of age or older received either 200 mg trovafloxacin by mouth and intravenous (i.v.) placebo or 2 g cefoxitin by i.v. infusion and placebo by mouth before elective vaginal or abdominal hysterectomy for nonmalignant disease.

RESULTS

In the 103 and 97 patients in the trovafloxacin and cefoxitin groups, respectively, who were evaluable for efficacy, the prophylactic success rates at hospital discharge (96% in both groups) and 30 +/- 6 days after hysterectomy (88% and 91% in the trovafloxacin and cefoxitin groups, respectively) were statistically equivalent. Both antibiotics were well tolerated.

CONCLUSION

A single oral 200 mg dose of trovafloxacin is as effective and safe as a standard cefoxitin parenteral regimen in the prevention of primary bacterial infection after elective vaginal or abdominal hysterectomy for nonmalignant disease.

Double-blind comparison of single-dose alatrofloxacin and cefotetan as prophylaxis of infection following elective colorectal surgery. Trovafloxacin Surgical Group

BACKGROUND

Alatrofloxacin, the prodrug of trovafloxacin, is a novel fluoroquinolone antimicrobial agent with a broad spectrum, including activity against gram-positive and gram-negative aerobes and anaerobes. Its pharmacokinetic properties (long half-life, excellent tissue distribution, and good safety profile) suggest a role in surgical prophylaxis. This prospective, multicenter, double-blind trial compared alatrofloxacin with cefotetan, an approved drug for surgical prophylaxis, in reducing postoperative infections.

METHODS

The efficacy and safety of a single 200-mg intravenous dose of alatrofloxacin were compared to a single 2-g intravenous dose of cefotetan in 492 patients undergoing elective colorectal surgery. The efficacy of alatrofloxacin as a prophylaxis for wound, intra-abdominal, or remote-site postoperative infectious complications was compared with cefotetan in 317 clinically evaluable patients; 161 received alatrofloxacin and 156 received cefotetan. The patients were monitored for infections and safety for 30 days postoperatively.

RESULTS

No statistically significant between-treatment difference was detected in successful clinical response rates at the end of the study (72% for each group). The incidence of primary wound infections at the time of hospital discharge was also similar: 21% in patients treated with alatrofloxacin and 18% in those treated with cefotetan. Safety, established by the incidence of adverse events, did not differ statistically between the groups.

CONCLUSIONS

A single intravenous dose of alatrofloxacin given within 4 hours prior to surgery was as effective as an intravenous dose of cefotetan in the prevention of postoperative infectious complications in patients undergoing elective colorectal surgery. The safety profiles of the two medications were similar.

Community-acquired pneumonia

This seminar reviews the aetiology, clinical presentation, approach to diagnosis, and management of immunocompetent adults with community-acquired pneumonia (CAP). Pneumonia is a common clinical entity, particularly among the elderly. A thorough understanding of the epidemiology and microbiology of CAP is essential for appropriate diagnosis and management. Although the microbiology of CAP has remained relatively stable over the last decade, there is new information on the incidence of atypical pathogens, particularly in patients not admitted to hospital, and new information on the incidence of pathogens in cases of severe CAP and in CAP in the elderly. Recent studies have provided new data on risk factors for mortality in CAP, which can assist the clinician in decisions about the need for hospital admission. The emergence of antimicrobial resistance in Streptococcus pneumoniae, the organism responsible for most cases of CAP, has greatly affected the approach to therapy, especially in those patients who are treated empirically. Guidelines for the therapy of CAP have been published by the American Thoracic Society, the British Thoracic Society, and, most recently, the Infectious Diseases Society of America. These guidelines differ in their emphasis on empirical versus pathogenic-specific management.

Comparative antimicrobial activity of trovafloxacin tested against 3049 Streptococcus pneumoniae isolates from the 1997-1998 respiratory infection season

Trovafloxacin is a new fluorinated naphthyridone having expanded activity against Gram-positive and anaerobic pathogens compared with ciprofloxacin or levofloxacin or ofloxacin. A multicenter in vitro trial (201 sites) was initiated in late 1997 to study the comparative activity of trovafloxacin against Streptococcus pneumoniae strains during the recently completed respiratory disease season. Each laboratory was asked to test 20 to 30 recent isolates (3049 strains) by the Etest (AB BIODISK, Solna, Sweden) method with observed phenotypes with elevated trovafloxacin results (MIC, > 1 microgram/mL) confirmed by the monitor laboratory (University of Iowa College of Medicine). Approximately one-third (34.0%) of isolates were penicillin nonsusceptible (12.8% high-level resistance at > or = 2 micrograms/mL). Also 20.4% and 4.5% of strains were resistant to macrolides (erythromycin) and ceftriaxone, respectively. The macrolide resistance rate was lowered to 16.8% when the adverse effect of CO2 incubation was considered. Only 0.3% of S. pneumoniae were vancomycin-nonsusceptible using the current National Committee for Clinical Laboratory Standards breakpoint (< or = 1 microgram/mL) with nearly all results were at 1.5 micrograms/mL. Trovafloxacin (MIC50 and MIC90, 0.094 and 0.19 microgram/mL, respectively) was eight fold more potent than levofloxacin (MIC90, 0.75 and 1.5 micrograms/mL), and fewer strains (0.10%) were discovered with high-level resistance (MIC, > or = 8 micrograms/mL). The four resistant isolates from different states had alterations in both par C and gyr A. Trovafloxacin had the best potency observed against contemporary pneumococcal isolates, and has a spectrum (> 99.8% susceptible) for an orally administered agent that was comparable to the tested parenteral glycopeptide, vancomycin (> 99.7%). Blood and spinal-fluid culture isolates were generally more susceptible to penicillin (74.4 to 75.6%), other beta-lactams, and erythromycin (84.4%); throat and sputum isolates were significantly more resistant (p < 0.01). Increases in resistance among S. pneumoniae strains to beta-lactams and erythromycin were documented in all geographic regions monitored, other resistances also continue to evolve, and high-level fluoroquinolone resistance remains very rare.

In vitro activity of quinupristin/dalfopristin and newer quinolones combined with gentamicin against resistant isolates of Enterococcus faecalis and Enterococcus faecium

In a study designed to obtain data on compounds active against enterococci, the minimum inhibitory concentrations (MICs) of quinupristin/dalfopristin (RP 59500) and the novel quinolones DU-6859a, trovafloxacin, levofloxacin, and sparfloxacin were determined for 122 Enterococcus faecalis and seven Enterococcus faecium isolates. In addition, 15 Enterococcus faecalis isolates resistant to gentamicin, DU-6859a, and trovafloxacin were exposed over time to combinations of DU-6859a plus gentamicin and trovafloxacin plus gentamicin. DU-6859a and trovafloxacin were found to be the most active compounds against Enterococcus faecalis and DU-6859a and RP 59500 against Enterococcus faecium. Synergy between either DU-6859a or trovafloxacin and gentamicin was observed with 27 to 35% of the isolates. It is concluded that DU-6859a and trovafloxacin are very potent against enterococci, especially when combined with gentamicin.

Treatment of experimental Staphylococcus epidermidis endophthalmitis with oral trovafloxacin

PURPOSE

To investigate the ocular pharmacokinetics and efficacy of oral trovafloxacin, a novel fluoroquinolone antibiotic, in Staphylococcus epidermidis endophthalmitis.

METHODS

Albino rabbits (n = 20) were infected with an intravitreal inoculum of S epidermidis (1.0 x 10(8) colony-forming units [CFU/0.1 ml) and 24 hours later received a single oral dose of trovafloxacin (250 mg/kg). Serum and intraocular samples from infected and control (noninfected) eyes were obtained up to 24 hours after antibiotic administration for measurement of trovafloxacin levels. A second group of rabbits (n = 72) was infected intraocularly and randomized 24 hours later to oral trovafloxacin (250 mg/kg twice a day) for 6 days or no treatment (control). Treatment efficacy was assessed by vitreous culture, clinical examination, and histopathology.

RESULTS

Following a single dose of trovafloxacin, maximal vitreous levels were achieved at 8 hours in infected eyes, with a penetration ratio of 36%. Vitreous levels were greater than 15 times the minimum inhibitory concentration of the strain employed. In animals with established endophthalmitis, treated eyes were sterilized after 5 days (P = .0495) compared with control eyes, which autosterilized at 14 days. Clinical and histologic examination revealed significant amelioration of anterior segment inflammation in treated eyes, although severe destruction of posterior segment structures occurred in both groups after 6 days of therapy.

CONCLUSIONS

These data support trovafloxacin as a potential oral agent for treatment or prophylaxis of S epidermidis endophthalmitis, although retinal alterations that occur over the period required for vitreous sterilization suggest that it will not replace intravitreal therapy in established endophthalmitis.

Pharmacokinetics of [18F]trovafloxacin in healthy human subjects studied with positron emission tomography

Tissue pharmacokinetics of trovafloxacin, a new broad-spectrum fluoroquinolone antimicrobial agent, were measured by positron emission tomography (PET) with [18F]trovafloxacin in 16 healthy volunteers (12 men and 4 women). Each subject received a single oral dose of trovafloxacin (200 mg) daily beginning 5 to 8 days before the PET measurements. Approximately 2 h after the final oral dose, the subject was positioned in the gantry of the PET camera, and 1 h later 10 to 20 mCi of [18F]trovafloxacin was infused intravenously over 1 to 2 min. Serial PET images and blood samples were collected for 6 to 8 h, starting at the initiation of the infusion. Drug concentrations were expressed as the percentage of injected dose per gram, and absolute concentrations were estimated by assuming complete absorption of the final oral dose. In most tissues, there was rapid accumulation of the radiolabeled drug, with high levels achieved within 10 min after tracer infusion. Peak concentrations of more than five times the MIC at which 90% of the isolates are inhibited (MIC90) for most members of Enterobacteriaceae and anaerobes (>10-fold for most organisms) were achieved in virtually all tissues, and the concentrations remained above this level for more than 6 to 8 h. Particularly high peak concentrations (micrograms per gram; mean +/- standard error of the mean [SEM]) were achieved in the liver (35.06 +/- 5.89), pancreas (32.36 +/- 20. 18), kidney (27.20 +/- 10.68), lung (22.51 +/- 7.11), and spleen (21. 77 +/- 11.33). Plateau concentrations (measured at 2 to 8 h; micrograms per gram; mean +/- SEM) were 3.25 +/- 0.43 in the myocardium, 7.23 +/- 0.95 in the lung, 11.29 +/- 0.75 in the liver, 9.50 +/- 2.72 in the pancreas, 4.74 +/- 0.54 in the spleen, 1.32 +/- 0.09 in the bowel, 4.42 +/- 0.32 in the kidney, 1.51 +/- 0.15 in the bone, 2.46 +/- 0.17 in the muscle, 4.94 +/- 1.17 in the prostate, and 3.27 +/- 0.49 in the uterus. In the brain, the concentrations (peak, approximately 2.63 +/- 1.49 microg/g; plateau, approximately 0.91 +/- 0.15 microg/g) exceeded the MIC90s for such common causes of central nervous system infections as Streptococcus pneumoniae (MIC90, <0.2 microg/ml), Neisseria meningitidis (MIC90, <0.008 microg/ml), and Haemophilus influenzae (MIC90, <0.03 microg/ml). These PET results suggest that trovafloxacin will be useful in the treatment of a broad range of infections at diverse anatomic sites.

Hepatobiliary elimination of trovafloxacin and metabolites following single oral doses in healthy volunteers

Trovafloxacin, a fluoronaphthyridone derivative related to fluoroquinolones, has significant activity against gram-negative and gram-positive pathogens, including penicillin-resistant Streptococcus pneumoniae, anaerobes and atypical organisms, good tissue penetration and a long elimination half-life. Following oral administration, less than 10% of the dose is renally eliminated as unchanged drug. Hepatobiliary elimination of trovafloxacin was examined by comparing the time course and bile and serum concentrations of trovafloxacin and its metabolites following oral administration to three patients with in-dwelling nasobiliary catheters or T-tubes. Following a single 200 mg oral dose, the mean maximum plasma trovafloxacin concentration was 2.0+/-0.4 mg/l, the area under the concentration-time curve 22.0+/-5.5 mg x h/l and the elimination half-life 8.5 h. Values in bile for the same subjects were 27.8+/-9.6 mg/l, 327.7+/-142.9 mg x h/l and 10.7 h. Corresponding values for the N-acetyl metabolite in bile were 3.8+/-3.4 mg/l, 35.3+/-29.8 mg x h/l and 8.3 h. The mean bile : serum ratio of trovafloxacin was 14:9 and consistent with biliary elimination. Serum concentrations of trovafloxacin in this study were similar to those reported in healthy volunteers. Bile concentrations of trovafloxacin substantially exceeded those of the N-acetyl metabolite, suggesting efficient clearance of the metabolite or that hepatic metabolism of trovafloxacin is not extensive.

Trovafloxacin versus high-dose amoxicillin (1 g three times daily) in the treatment of community-acquired bacterial pneumonia

Once-daily trovafloxacin 200 mg was compared with high-dose amoxicillin, 1 g three times daily, given for 7 to 10 days. At end of treatment (day 10), the response was clinically successful (cure + improvement) in 93% of 152 clinically evaluable trovafloxacin patients and in 89% of 160 amoxicillin patients. At study end (day 35), respective rates were 91% and 81% (95% confidence interval: 1.6, 17.6; P=0.01). In evaluable patients with positive baseline radiographs, 93% of trovafloxacin and 88% of amoxicillin patients demonstrated radiological resolution at end of treatment. Streptococcus pneumoniae and Haemophilus influenzae eradication rates were comparable at end of treatment in both treatment groups, but at study end Streptococcus pneumoniae eradication rates were higher in trovafloxacin patients (100% vs 81%). At study end, all four trovafloxacin patients with baseline penicillin-resistant Streptococcus pneumoniae were clinically cured with pathogen eradication, whereas two of five amoxicillin patients with baseline penicillin-resistant Streptococcus pneumoniae were clinical failures with pathogen persistence. For patients in whom no pathogen was identified, trovafloxacin was significantly more effective at end of treatment (P=0.096) and study end (P=0.013). Treatment-related adverse events were comparable; the most common were headache, vomiting and dizziness in trovafloxacin patients, and diarrhoea. headache and abdominal pain in amoxicillin patients.

Single- and multiple-dose administration, dosing regimens, and pharmacokinetics of trovafloxacin and alatrofloxacin in humans

A simplified dosing algorithm for trovafloxacin was evaluated following a single-dose infusion of alatrofloxacin at trovafloxacin equivalent doses of 30, 100, 200, 300 and 400 mg (57 subjects), and multiple doses of 200, 300 and 400 mg (30 subjects). Maximum serum concentration and area under the concentration-time curve for trovafloxacin increased with dose. Trovafloxacin clearance (82-85 ml x h/kg) and volume of distribution (1.3-1.6 l/kg) were independent of dose. Infusion of alatrofloxacin at a trovafloxacin equivalent dose of 300 mg at 1, 2 or 3 mg/ml over 1 h did not alter the pharmacokinetics of trovafloxacin. A plot of the weight-adjusted dose of trovafloxacin in individual subjects against the maximum serum concentration following single and multiple dosing, indicated that the maximum serum concentration increased 1 microg/ml for each 1 mg/kg of trovafloxacin administered. Thus, a prior knowledge of the desired serum concentration will permit appropriate dosing without the use of complex nomograms in patients with normal hepatic function.

Bacteriological activity of trovafloxacin, a new quinolone, against respiratory tract pathogens

The use of established fluoroquinolones, such as ciprofloxacin and ofloxacin, as empirical therapy for the treatment of moderate-to-severe respiratory tract infections is limited by their poor activity against gram-positive and atypical pathogens. Data from in vitro susceptibility studies and in vivo animal protection models suggest that the new fluoroquinolone, trovafloxacin, compared with ciprofloxacin and ofloxacin offers equivalent activity against gram-negative pathogens and improved activity against gram-positive pathogens. In particular, susceptibility data indicate that trovafloxacin is at least 16-fold more potent than either ciprofloxacin or ofloxacin against penicillin-susceptible and penicillin-resistant strains of Streptococcus pneumoniae. Other susceptible pathogens include Streptococcus pyogenes, vancomycin-susceptible Enterococcus faecalis and the atypical respiratory pathogens Legionella pneumophila, Mycoplasma pneumoniae and Chlamydia pneumoniae. In vivo studies involving models of protection against acute systemic infection and pneumococcal pneumonia in mice, and Legionnaires' disease in guinea pigs, indicate that the antibacterial spectrum observed for trovafloxacin in vitro extends to the in vivo setting. Together, these findings suggest that trovafloxacin may offer clinical efficacy against respiratory pathogens superior to that of ciprofloxacin and of ofloxacin, and may find a useful role as empiric therapy in both the community and hospital setting.

Comparison of in vitro activity of trovafloxacin against gram-positive and gram-negative organisms with quinolones and beta-lactam antimicrobial agents

The in vitro activity of trovafloxacin against 721 Gram-negative and 498 Gram-positive organisms was determined by the standard microdilution broth method using commercially prepared frozen microtiter plates. The activity of trovafloxacin was compared to ofloxacin, ciprofloxacin, amoxicillin/clavulanate, ampicillin/sulbactam (1:1), piperacillin/tazobactam, ceftriaxone, and imipenem. Trovafloxacin had equal or greater activity compared with the other agents tested against Citrobacter diversus, Enterobacter aerogenes, Enterobacter cloacae, Escherichia coli, Haemophilus influenzae, Stenotrophomonas maltophilia, Serratia marcescens, staphylococci, Streptococcus pneumoniae, Streptococcus pyogenes, Streptococcus viridans, group G streptococci, Enterococcus faecalis, and E. faecium. The reliability of the commercially prepared plates for testing the in vitro activity of the quinolones was evaluated by comparing identical isolates also tested by broth microdilution using laboratory prepared plates. The commercially prepared plates generally correlated, within one- to twofold dilutions, with the laboratory prepared plates. There was, however, a large discrepancy obtained when testing Enterobacter agglomerans and E. cloacae, where the commercially prepared plates yielded a significantly higher MIC90 value.

Quality control limits for dilution and disk diffusion susceptibility tests of trovafloxacin against eight quality control strains

A 10-laboratory collaborative effort was designed to generate data to propose quality control limits for susceptibility tests of trovafloxacin. Broth microdilution, agar dilution, and disk diffusion tests were evaluated with eight different control strains. All tests were reproducible, and control limits are proposed.

Comparative activity of ciprofloxacin, ofloxacin, levofloxacin, and erythromycin against Legionella species by broth microdilution and intracellular susceptibility testing in HL-60 cells

Animal lung macrophages or human peripheral blood mononuclear cells have been used for testing intracellular activity of anti-Legionella antibiotics; such studies are labor intensive such that comparative antibiotic studies for the many Legionella species are few. We evaluated a human monocyte cell line (HL-60) as an alternative model. HL-60 (1.5 x 10(6) cells/well) was differentiated into adherent cell and infected with 1.5 x 10(7) CFU of Legionella pneumophilia (L. pneumophilia). Erythromycin and quinolones, ciprofloxacin, ofloxacin, and levofloxacin were added to cells at 1 and 8 x MIC. Percent (%) inhibition ratios equal to total L. pneumophila with agent divided by L. pneumophila without agent x 100 were determined at 48 h; lower ratios implied greater potency. By broth dilution in buffered yeast extract broth, the most potent agents against L. pneumophila were (MIC): ciprofloxacin (0.015-0.03), ofloxacin (0.015-0.03), levofloxacin (0.015-0.03), erythromycin (0.125-1.0 microgram/mL). In the intracellular model, the most potent inhibitors of L. pneumophila multiplication at 8 x MIC were (in order of potency) levofloxacin (24.2%), ciprofloxacin (30.6%), ofloxacin (37.1%), and erythromycin (55.0%). All the quinolones were highly active and significantly more potent against L. micdadei and L. bozemanii when compared to L. pneumophila.

Randomized trial of trovafloxacin and ofloxacin for single-dose therapy of gonorrhea. Trovafloxacin Gonorrhea Study Group

PURPOSE

To compare trovafloxacin, a new quinolone antibiotic with enhanced activity against Neisseria gonorrhoeae, with ofloxacin as single-dose oral therapy for uncomplicated gonococcal urethritis or cervicitis.

PATIENTS AND METHODS

In this multicenter, double-blind trial, 625 patients (270 men, 355 women) with uncomplicated gonococcal urethritis or cervicitis received one 100-mg tablet of trovafloxacin or two 200-mg capsules of ofloxacin as a single dose under direct supervision.

RESULTS

Single-dose oral therapy with trovafloxacin was equivalent both bacteriologically and clinically to ofloxacin. Among evaluable patients, N gonorrhoeae was eradicated in 99% of trovafloxacin recipients and in 98% of ofloxacin recipients. Each treatment was well tolerated; vaginitis was the most frequently observed side effect (4% trovafloxacin, 7% ofloxacin).

CONCLUSION

Based on the results presented here, trovafloxacin is a promising agent for single-dose therapy of uncomplicated gonorrhea.

Treatment of enterococcal pyelonephritis with trovafloxacin and rifampin: in vitro-in vivo contrast

The in vitro bactericidal interaction of trovafloxacin and rifampin against Enterococcus spp. has indicated that antagonism occurs between these two antimicrobial agents. This drug combination was examined in vivo in rats with experimental pyelonephritis. The rats received trovafloxacin, rifampin, or both drugs. On the basis of the mean log10 CFU of Enterococcus faecalis from the kidneys, there was no evidence that trovafloxacin and rifampin were antagonistic in vivo.