Single-dose pharmacokinetics and penetration of BMS 284756 into an inflammatory exudate

The Drug-Specific Propensity Regarding the Acquisition of Fluoroquinolone Resistance in Escherichia coli: An in vitro Challenge and DNA Mutation Analysis

Objective

Many fluoroquinolones, such as ciprofloxacin, are used clinically. We investigated the relationship between resistance acquisition and exposure duration in each drug through the exposure of fluoroquinolone to Escherichia coli clinical isolates in vitro.

Methods

Eleven E. coli clinical isolates were exposed to each fluoroquinolone, ie, ciprofloxacin, levofloxacin, sitafloxacin, garenoxacin, and lascufloxacin, with the concentration of the mutant selection window for 5 days; these procedures were repeated 5-times. In addition, the DNA sequence in the quinolone-resistance determining region (QRDR) and the expression level in the drug efflux pump acrA were analyzed to determine the resistance mechanism.

Results

Although resistant strains were not detected after 5 to 10 days of exposure to fluoroquinolone, after 25 days of exposure to ciprofloxacin and levofloxacin, 100% and 45% of isolates acquired resistance, respectively. Due to 25 days of exposure to sitafloxacin, garenoxacin, and lascufloxacin, MIC measurement was elevated 2- to 4096-fold for those of the parental strain, and the cross-resistance rate to levofloxacin was 72%, 54%, and 27%, respectively. In strains with high fluoroquinolone resistance, acrA overexpression was observed in addition to QRDR mutation.

Conclusion

In our findings, fluoroquinolone resistance was not observed in the E. coli strain after 5- to 10-days of exposure. However, resistance acquisition was detected frequently after 15- to 25-days of exposure. Among fluoroquinolones, lascufloxacn had the least impact on the resistance acquisition in E. coli.

Pharmacokinetics and Pharmacodynamics of the New Quinolones

In this review, the authors describe the pharmacokinetic (PK) and pharmacodynamic (PD) characteristics of the new quinolones (levofloxacin, gatifloxacin, moxifloxacin, gemifloxacin, and garenoxacin) and discuss their implications on adequate therapy of patients with respiratory infections. The newer quinolones display excellent bioavailability and have longer serum half-lives than ciprofloxacin. In addition, they have the ability to concentrate in respiratory tract tissues and fluids at levels that exceed serum-drug concentrations. Also, the newer quinolones exhibit broad-spectrum activity against both susceptible and resistant organisms. Those favorable PK/PD properties make the new quinolones an attractive therapeutic alternative to traditional agents for common respiratory infections. Understanding the PK/PD of quinolone antibiotics can facilitate selection of optimal regimens to hasten response, prevent treatment failures, and minimize the development of resistance.

A Review of New Fluoroquinolones : Focus on their Use in Respiratory Tract Infections

The new respiratory fluoroquinolones (gatifloxacin, gemifloxacin, levofloxacin, moxifloxacin, and on the horizon, garenoxacin) offer many improved qualities over older agents such as ciprofloxacin. These include retaining excellent activity against Gram-negative bacilli, with improved Gram-positive activity (including Streptococcus pneumoniae and Staphylococcus aureus). In addition, gatifloxacin, moxifloxacin and garenoxacin all demonstrate increased anaerobic activity (including activity against Bacteroides fragilis). The new fluoroquinolones possess greater bioavailability and longer serum half-lives compared with ciprofloxacin. The new fluoroquinolones allow for once-daily administration, which may improve patient adherence. The high bioavailability allows for rapid step down from intravenous administration to oral therapy, minimizing unnecessary hospitalization, which may decrease costs and improve quality of life of patients. Clinical trials involving the treatment of community-acquired respiratory infections (acute exacerbations of chronic bronchitis, acute sinusitis, and community-acquired pneumonia) demonstrate high bacterial eradication rates and clinical cure rates. In the treatment of community-acquired respiratory tract infections, the various new fluoroquinolones appear to be comparable to each other, but may be more effective than macrolide or cephalosporin-based regimens. However, additional data are required before it can be emphatically stated that the new fluoroquinolones as a class are responsible for better outcomes than comparators in community-acquired respiratory infections. Gemifloxacin (except for higher rates of hypersensitivity), levofloxacin, and moxifloxacin have relatively mild adverse effects that are more or less comparable to ciprofloxacin. In our opinion, gatifloxacin should not be used, due to glucose alterations which may be serious. Although all new fluoroquinolones react with metal ion-containing drugs (antacids), other drug interactions are relatively mild compared with ciprofloxacin. The new fluoroquinolones gatifloxacin, gemifloxacin, levofloxacin, and moxifloxacin have much to offer in terms of bacterial eradication, including activity against resistant respiratory pathogens such as penicillin-resistant, macrolide-resistant, and multidrug-resistant S. pneumoniae. However, ciprofloxacin-resistant organisms, including ciprofloxacin-resistant S. pneumoniae, are becoming more prevalent, thus prudent use must be exercised when prescribing these valuable agents.

Effects of Lactoferrin on IL-6 Production by Peritoneal and Alveolar Cells in Cyclophosphamide-Treated Mice

Previous studies have shown that oral treatment with lactoferrin (LF) restores the immune response in cyclophosphamide (CP) immunocompromised mice. The aim of the present investigation was to determine the regulatory ability of LF on the production of interleukin 6 (IL-6) in peritoneal and alveolar cells, derived from CP-treated mice. CBA mice were injected with a single, intraperitoneal (i.p.) dose of CP (350 mg/kg body weight) followed by LF administered in drinking water (0.5% solution) for 21 days. The control counterparts were given water. Peritoneal and alveolar cells were isolated from mice and the production of IL-6, both spontaneous and lipopolysaccharide (LPS) induced, was determined in 24h cell cultures using a bioassay. The results showed increased production of IL-6 in both CP-treated mice and in mice given, in addition, LF. The administration of LF alone led also to an increase in IL-6 production by the cell cultures. Intravenous (i.v.) administration of LPS resulted in a significant increase in IL-6 serum levels in CP and CP/LF but not in LF-treated mice. Analysis of cell type composition in the peritoneal cavity revealed a strong increase in mastocyte and neutrophil content in CP and CP/LF-treated groups. Our findings suggest that enhanced IL-6 production in CP and CP/LF-treated mice may contribute to reconstitution of immune system function in immunocompromised mice.

Penetration of garenoxacin into lung tissues and bone in subjects undergoing lung biopsy or resection

OBJECTIVE

Concentrations of garenoxacin in plasma and samples of lung parenchyma, bronchial mucosa, and bone were determined following single-dose administration.

RESEARCH DESIGN AND METHODS

Open-label, non-randomized study in which subjects undergoing invasive lung biopsy or resection were given a single 600-mg oral dose of garenoxacin. Lung parenchyma, and, if possible, bronchial mucosa and bone (i.e., flat bone with sinus mucosa or long bone from the lower legs) samples and corresponding plasma samples were obtained 2-4, 4-6, 10-12, or 20-24 h post-dose. Garenoxacin concentrations were measured using validated liquid chromatography with dual mass spectrometry. Safety was also assessed.

RESULTS

Twenty-seven subjects enrolled and completed the study. Garenoxacin plasma concentrations (mean +/- standard deviation) during the 24-h period ranged from 1.9 +/- 1 to 7.4 +/- 3 mug/mL. Garenoxacin concentrations in lung tissue (15.2 +/- 9 mug/g) peaked at 4-6 h and decreased to 3.7 +/- 3 mug/g at 20-24 h. Mean ratios between bronchial mucosa and plasma ranged from 0.82 to 0.99 over a 24-h period. At 12 h, the mean ratio between bone and plasma was 0.56. Garenoxacin concentrations in lung tissue exceeded the MIC(90) for common respiratory pathogens by at least 61-fold. Garenoxacin was safe and well tolerated. Forty-five adverse events were reported by 26 subjects; none were determined to be attributable to garenoxacin by the investigators. Most of the adverse events were mild to moderate in severity.

CONCLUSIONS

Garenoxacin achieved 24-h concentrations in pulmonary tissues that exceeded the MIC(90) for common respiratory pathogens. A controlled study involving a larger number of lung and bone tissue samples is needed to further confirm these findings.

Activity of garenoxacin, an investigational des-F(6)-quinolone, tested against pathogens from community-acquired respiratory tract infections, including those with elevated or resistant-level fluoroquinolone MIC values

Garenoxacin, a novel des-F(6)-quinolone, was tested against 40423 pathogenic isolates associated with community-acquired respiratory tract infections (CA-RTIs). The strains included Streptococcus pneumoniae (18887), Haemophilus influenzae (15555), and Moraxella catarrhalis (5981), each isolated from a significant infection monitored by the SENTRY Antimicrobial Surveillance Program (1999-2005; North America, Latin America, and Europe). All tests were performed by reference broth microdilution methods for garenoxacin and 19 comparison agents. The garenoxacin MIC(90) and percentage (%) of strains inhibited at < or =1 microg/mL (proposed susceptible breakpoint) were S. pneumoniae (0.06 microg/mL, >99.9% susceptible), H. influenzae (< or =0.03 microg/mL, >99.9%), and M. catarrhalis (< or =0.03 microg/mL, 100.0%). The garenoxacin potency versus the pneumococci was 16- to 32-fold greater than levofloxacin or ciprofloxacin and 2-fold superior to moxifloxacin (MIC(90), 0.12 microg/mL). Resistances to other classes of antimicrobials did not adversely influence garenoxacin MIC results. Ciprofloxacin- or levofloxacin-resistant (MIC, > or =4 microg/mL) S. pneumoniae had higher garenoxacin MIC(90) values (1 microg/mL), but 90.6% to 97.5% of strains remained susceptible. Strains of all 3 monitored pathogens with mutations in the quinolone resistance determining region (QRDR) had higher garenoxacin MIC results, with > or =3 to 4 QRDR mutations required to elevate garenoxacin MIC values to > or =2 microg/mL. In conclusion, garenoxacin possesses a potent activity against pneumococci, H. influenzae, and M. catarrhalis strains worldwide, at a level significantly greater than the available tested agents in the fluoroquinolone class (ciprofloxacin, levofloxacin, and moxifloxacin). Only 13 and 4 isolates (0.07% and 0.03%) of S. pneumoniae and H. influenzae, respectively, had a garenoxacin MIC at > or =2 microg/mL, thus, making this new "respiratory antipneumococcal" quinolone an attractive candidate for the therapy of contemporary CA-RTI (bronchitis, pneumonia, and sinusitis).

Acyclovir concentrations in the skin of humans after a single oral dose assessed by in vivo cutaneous microdialysis

BACKGROUND/PURPOSE

Acyclovir is a synthetic deoxyguanosine analogue used in the treatment of certain viral diseases. This drug is effective primarily against Herpes simplex virus, Varicella zoster virus and to a lesser extent against Epstein-Barr virus and cytomegalovirus. The aim of the study was to determine the acyclovir concentrations in plasma and skin (cutaneous microdialysate) and to compare its penetration into real (skin) and theoretical peripheral compartment after administration of a single 0.4 g oral dose.

METHODS

To evaluate the skin concentrations of the examined agent in 10 healthy male volunteers linear microdialysis probes with 2 kDa molecular-weight cut-off were inserted intradermally and were perfused with Ringer solution up to 6 h after drug ingestion.

RESULTS

The mean maximum acyclovir concentrations in the plasma, skin and theoretical peripheral compartment were 3.16+/-0.86, 0.94+/-0.34 and 1.85+/-0.69 micromol/L, respectively, and were achieved after 1.6+/-0.4, 2.4+/-0.3 and 3.7+/-0.7 h. The degree of penetration into the real (skin) and theoretical peripheral compartment was 0.36+/-0.15 and 0.74+/-0.12, respectively, and the differences were statistically significant. Similarly, also, the maximum concentration, time to maximum concentration and area under the concentration-time curve differed significantly between the plasma and skin as well as between the skin and the theoretical peripheral compartment.

CONCLUSIONS

In selected cases skin concentrations should be determined rather than those in blood plasma when studying the distribution of orally administered drugs. Evaluation of acyclovir concentrations in the skin cannot be replaced by the calculation of the theoretical peripheral compartment.

Investigational new drugs for the treatment of resistant pneumococcal infections

Antibiotic resistance in Streptococcus pneumoniae is not only increasing with penicillin but also with other antimicrobial classes including the macrolides, tetracyclines and sulfonamides. This trend with antibiotic resistance has highlighted the need for the further development of new anti-infectives for the treatment of pneumococcal infections, particularly against multi-drug resistant pneumococci. Several new drugs with anti-pneumococcal activity are at various stages of development and will be discussed in this review. Two new cephalosporins with activity against S. pneumoniae include ceftobiprole and RWJ-54428. Faropenem is in a new class of beta-lactam antibiotics called the penems. Structurally, the penems are a hybrid between the penicillins and cephalosporins. Sitafloxacin and garenoxacin are two new quinolones that are likely to have a role in treating pneumococcal infections. Oritavancin and dalbavancin are glycopeptides with activity against methicillin-resistant S. aureus and vancomycin-resistant Enterococcus spp. as well as multi-drug resistant pneumococci. Tigecycline is the first drug in a new class of anti-infectives called the glycycyclines that has activity against penicillin-resistant pneumococci.

Guide to selection of fluoroquinolones in patients with lower respiratory tract infections

Newer fluoroquinolones such as levofloxacin, moxifloxacin, gatifloxacin and gemifloxacin have several attributes that make them excellent choices for the therapy of lower respiratory tract infections. In particular, they have excellent intrinsic activity against Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis and the atypical respiratory pathogens. Fluoroquinolones may be used as monotherapy to treat high-risk patients with acute exacerbation of chronic bronchitis, and for patients with community-acquired pneumonia requiring hospitalisation, but not admission to intensive care. Overall, the newer fluoroquinolones often achieve clinical cure rates in > or =90% of these patients. However, rates may be lower in hospital-acquired pneumonia, and this infection should be treated on the basis of anticipated organisms and evaluation of risk factors for specific pathogens such as Pseudomonas aeruginosa. In this setting, an antipseudomonal fluoroquinolone may be used in combination with an antipseudomonalbeta-lactam. Concerns are now being raised about the widespread use, and possibly misuse, of fluoroquinolones and the emergence of resistance among S. pneumoniae, Enterobacteriaceae and P. aeruginosa. A number of pharmacokinetic parameters such as the peak concentration of the antibacterial after a dose (C(max)), and the 24-hour area under the concentration-time curve (AUC24) and their relationship to pharmacodynamic parameters such as the minimum inhibitory and the mutant prevention concentrations (MIC and MPC, respectively) have been proposed to predict the effect of fluoroquinolones on bacterial killing and the emergence of resistance. Higher C(max)/MIC or AUC24/MIC and C(max)/MPC or AUC24/MPC ratios, either as a result of dose administration or the susceptibility of the organism, may lead to a better clinical outcome and decrease the emergence of resistance, respectively. Pharmacokinetic profiles that are optimised to target low-level resistant minor subpopulations of bacteria that often exist in infections may help preserve fluoroquinolones as a class. To this end, optimising the AUC24/MPC or C(max)/MPC ratios is important, particularly against S. pneumoniae, in the setting of lower respiratory tract infections. Agents such as moxifloxacin and gemifloxacin with high ratios against this organism are preferred, and agents such as ciprofloxacin with low ratios should be avoided. For agents such as levofloxacin and gatifloxacin, with intermediate ratios against S. pneumoniae, it may be worthwhile considering alternative dose administration strategies, such as using higher dosages, to eradicate low-level resistant variants. This must, of course, be balanced against the potential of toxicity. Innovative approaches to the use of fluoroquinolones are worth testing in further in vitro experiments as well as in clinical trials.

Antimicrobial activities of garenoxacin (BMS 284756) against Asia-Pacific region clinical isolates from the SENTRY program, 1999 to 2001

Between 1999 and 2001, 16,731 isolates from the Asia-Pacific Region were tested in the SENTRY Program for susceptibility to six fluoroquinolones including garenoxacin. Garenoxacin was four- to eightfold less active against Enterobacteriaceae than ciprofloxacin, although both drugs inhibited similar percentages at 1 microg/ml. Garenoxacin was more active against gram-positive species than all other fluoroquinolones except gemifloxacin. For Staphylococcus aureus, oxacillin resistance was high in many participating countries (Japan, 67%; Taiwan, 60%; Hong Kong, 55%; Singapore, 52%), with corresponding high levels of ciprofloxacin resistance (57 to 99%) in oxacillin-resistant S. aureus (ORSA). Of the ciprofloxacin-resistant ORSA isolates, the garenoxacin MIC was >4 microg/ml for only 9% of them. For Streptococcus pneumoniae, penicillin nonsusceptibility and macrolide resistance were high in many countries. No relationship was seen between penicillin and garenoxacin susceptibility, with all isolates being susceptible at <2 microg/ml. There was, however, a partial correlation between ciprofloxacin and garenoxacin MICs. For ciprofloxacin-resistant isolates for which garenoxacin MICs were 0.25 to 1 microg/liter, mutations in both the ParC and GyrA regions of the quinolone resistance-determining region could be demonstrated. No mutations conferring high-level resistance were detected. Garenoxacin shows useful activity against a wide range of organisms from the Asia-Pacific region. In particular, it has good activity against S. aureus and S. pneumoniae, although there is evidence that low-level resistance is present in those organisms with ciprofloxacin resistance.

In vitro activities of garenoxacin (BMS-284756) against Streptococcus pneumoniae, viridans group streptococci, and Enterococcus faecalis compared to those of six other quinolones

The activity of garenoxacin, a new quinolone, was determined in comparison with other quinolones against different strains of S. pneumoniae, viridans group streptococci (VGS), and Enterococcus faecalis. Strains were quinolone-susceptible clinical isolates and quinolone-resistant strains with defined mechanisms of resistance obtained from either clinical isolates or derivatives of S. pneumoniae R6. Clinical quinolone-susceptible strains of S. pneumoniae, VGS and E. faecalis showed garenoxacin MICs within a range of 0.03 microg/ml to 0.25 micro g/ml. Garenoxacin MICs increased two- to eightfold when one mutation was present in the ParC quinolone resistance-determining region (QRDR), fourfold when one mutation was present in the GyrA QRDR (S. pneumoniae), 8- to 64-fold when two or three mutations were associated in ParC and GyrA QRDR, and 2,048-fold when two mutations were present in both the GyrA and ParC QRDRs (Streptococcus pneumoniae). Increased active efflux had a moderate effect on garenoxacin MICs for S. pneumoniae and VGS. Against S. pneumoniae, garenoxacin behaved like moxifloxacin and sparfloxacin, being more affected by a single gyrA mutation than by a single parC mutation. Although garenoxacin was generally two- to fourfold more active than moxifloxacin against the different wild-type or mutant strains of S. pneumoniae, VGS, and E. faecalis, it was two- to fourfold less active than gemifloxacin. At four times the respective MIC for each strain, the bactericidal effect of garenoxacin, observed at 6 h for S. pneumoniae and at 24 h for S. oralis and E. faecalis, was not influenced by the presence of mutation either in the ParC or in both the ParC and GyrA QRDRs.

Efficacy of garenoxacin in treatment of experimental endocarditis due to Staphylococcus aureus or viridans group streptococci

The activity of garenoxacin was investigated in rats with experimental endocarditis due to staphylococci and viridans group streptococci (VGS). The staphylococci tested comprised one ciprofloxacin-susceptible and methicillin-susceptible Staphylococcus aureus (MSSA) isolate (isolate 1112), one ciprofloxacin-susceptible but methicillin-resistant S. aureus (MRSA) isolate (isolate P8), and one ciprofloxacin-resistant mutant (grlA) of P8 (isolate P8-4). The VGS tested comprised one penicillin-susceptible isolate and one penicillin-resistant isolate (Streptococcus oralis 226 and Streptococcus mitis 531, respectively). To simulate the kinetics of drugs in humans, rats were infused intravenously with garenoxacin every 24 h (peak and trough levels in serum, 6.1 and 1.0 mg/liter, respectively; area under the concentration-time curve [AUC], 63.4 mg. h/liter) or levofloxacin every 12 h (peak and trough levels in serum, 7.3 and 1.5 mg/liter, respectively; AUC, 55.6 mg. h/liter) for 3 or 5 days. Flucloxacillin, vancomycin, and ceftriaxone were used as control drugs. Garenoxacin, levofloxacin, flucloxacillin, and vancomycin sterilized >/=70% of the vegetations infected with both ciprofloxacin-susceptible staphylococcal isolates (P < 0.05 versus the results for the controls). Garenoxacin and vancomycin also sterilized 70% of the vegetations infected with ciprofloxacin-resistant MRSA isolate P8-4, whereas treatment with levofloxacin failed against this organism (cure rate, 0%; P < 0.05 versus the results obtained with the comparator drugs). Garenoxacin did not select for resistant derivatives in vivo. In contrast, levofloxacin selected for resistant variants in four of six rats infected with MRSA isolate P8-4. Garenoxacin sterilized 90% of the vegetations infected with both penicillin-susceptible and penicillin-resistant isolates of VGS. Levofloxacin sterilized only 22 and 40% of the vegetations infected with penicillin-susceptible S. oralis 226 and penicillin-resistant S. mitis 531, respectively. Ceftriaxone sterilized only 40% of those infected with penicillin-resistant S. mitis 531 (P < 0.05 versus the results obtained with garenoxacin). No quinolone-resistant VGS were detected. In all the experiments successful quinolone treatment was predicted by specific pharmacodynamic criteria (D. R. Andes and W. A. Craig, Clin. Infect. Dis. 27:47-50, 1998). The fact that the activity of garenoxacin was equal or superior to those of the standard comparators against staphylococci and VGS indicates that it is a potential alternative for the treatment of infections caused by such bacteria.

Emergence of levofloxacin-resistant pneumococci in immunocompromised adults after therapy for community-acquired pneumonia

We describe 4 patients infected with levofloxacin-resistant pneumococci after therapy for community-acquired pneumonia (CAP). The 4 patients had 15 episodes of CAP; Streptococcus pneumoniae was isolated from blood or sputum samples obtained during 14 of the episodes. The underlying medical condition was Bruton agammaglobulinemia in 3 patients and chronic lymphoid leukemia in the other. The initial episode of CAP in each patient was due to a levofloxacin-susceptible strain. One of 4 reinfections and 5 of 6 relapses were due to levofloxacin-resistant strains. All of these strains had amino acid substitutions in the quinolone-resistance-determining region of the genes parC and gyrA. The time between episodes of pneumonia varied from 1 to 4 months. In immunocompromised patients with suspected or proven pneumococcal infection, it may be prudent not to use fluoroquinolone monotherapy empirically when the patient has a history of fluoroquinolone therapy in at least the past 4 months.

In vitro antibacterial activity and pharmacodynamics of new quinolones

This synopsis of published literature summarises data on the in vitro antibacterial activity and pharmacodynamics of fluoroquinolones. Data were compiled for ciprofloxacin, levofloxcin, moxifloxacin, gatifloxacin, grepafloxacin, gemifloxacin, trovafloxacin, sitafloxacin and garenoxacin. All of these quinolones are almost equipotent against gram-negative bacteria but demonstrate improved activity against gram-positive species. The new quinolones are uniformly active against gram-positive species except Streptococcus pneumoniae; against which gemifloxacin, sitafloxacin and garenoxacin are one to two dilution steps more active than moxifloxacin. All of the new quinolones except gemifloxacin demonstrate enhanced activity against anaerobes. Since all the new quinolones show similar activity against the major respiratory tract pathogens except Streptococcus pneumoniae and members of the family Enterobacteriaceae, their pharmacokinetics and pharmacodynamics will be clinically relevant differentiators and determinants of their overall activity and efficacy. In vitro simulations of serum concentrations revealed that (i). gemifloxacin and levofloxacin were significantly and gatifloxacin moderately less active than moxifloxacin against Streptococcus pneumoniae and Staphylococcus aureus, and (ii). resistant subpopulations emerged following exposure to levofloxacin and gatifloxacin (gemifloxacin not yet published) but not to moxifloxacin. The emergence of resistance is a function of drug concentrations achievable in vivo and the susceptibility pattern of the target organisms. Therefore, the use of less potent fluoroquinolones with borderline or even suboptimal pharmacokinetic/pharmacodynamic surrogate parameters will inadvertently foster the development of class resistance. Drugs with the most favourable pharmacokinetic/pharmacodynamic characteristics should be used as first-line agents in order to preserve the potential of this drug class and, most importantly, to provide the patient with an optimally effective regimen.

Postantibiotic effects of garenoxacin (BMS-284756) against 12 gram-positive or -negative organisms

Conventional in vitro methods were used to determine the postantibiotic effects (PAEs), sub-MIC effects (SMEs), and postantibiotic sub-MIC effects (PA-SMEs) of garenoxacin for a range of organisms. The mean PAEs of garenoxacin for pneumococci, staphylococci, and enterococci were 0.3 to 2.2 h. For Escherichia coli and Pseudomonas aeruginosa, the PAEs were 0.9 to 1.6 h. The mean PA-SMEs (0.4 times the MIC) for pneumococci, staphylococci, and enterococci were 3.0 to >10 h, 1.8 to >10.7 h, and 5.8 h, respectively, while those for E. coli and P. aeruginosa were 7.6 and 4.4 h, respectively.

Actividad in vitro comparativa de garenoxacino (BMS-284756). Programa SENTRY España (1999-2000)

INTRODUCTION

To evaluate the in vitro activity of the new des-fluoro quinolone, garenoxacin (BMS-284756), compared to activities of ciprofloxacin, levofloxacin, and gatifloxacin in clinical isolates recovered over 1999 and 2000 within the SENTRY antimicrobial surveillance program.

METHODS

Quinolone-MICs were performed using the standard NCCLS microdilution technique in 2599 isolates recovered from Hospital Ramón y Cajal (Madrid), Virgen Macarena (Sevilla), and Bellvitge (Barcelona).

RESULTS

The modal MIC range value exhibited by garenoxacin ( < or = 0.03-0.12 mg/L) for Enterobacteriaceae was similar to that of the other quinolones tested. A total of 70% of Pseudomonas aeruginosa isolates were susceptible to garenoxacin and 85% to ciprofloxacin and levofloxacin. Garenoxacin exhibited the highest activity in Staphylococcus aureus, including both methicillin-susceptible and -resistant isolates, with MIC90 values of < or = 0.03 and 2 mg/L, respectively. All Streptococcus pneumoniae isolates were susceptible to garenoxacin, regardless of their penicillin susceptibility status; in terms of MIC90, garenoxacin was 16 times more active than ciprofloxacin and levofloxacin and 4-8 times more active than gatifloxacin. All 6 ciprofloxacin-resistant S. pneumoniae strains showed garenoxacin MIC values ranging from < or = 0.03 to 0.5 mg/L. In Haemophilus influenzae and Moraxella catarrhalis, garenoxacin displayed excellent in vitro activity (MIC < or = 0.06 mg/L), similar to that of the other quinolones tested.

CONCLUSIONS

Garenoxacin activity was similar to the activity of other quinolones in Enterobacteriaceae, but was lower in P. aeruginosa. Garenoxacin activity was clearly higher than that of other quinolones in gram-positive isolates, including methicillin-resistant S. aureus and S. pneumoniae with reduced penicillin susceptibility.

Geographic variations in garenoxacin (BMS284756) activity tested against pathogens associated with skin and soft tissue infections: report from the SENTRY Antimicrobial Surveillance Program (2000)

The antimicrobial activity of garenoxacin, a des-(6)F quinolone (formally BMS284756 and T-3811), was evaluated against 2,537 skin and soft tissue infection (SSTI) isolates from the SENTRY Antimicrobial Surveillance Program. Strains isolated in 2000 from Europe, North and Latin America were tested at a central laboratory using reference broth microdilution methods. The rank order of the seven most frequent SSTI pathogens was: Staphylococcus aureus (39.9%), Pseudomonas aeruginosa (12.1%), Escherichia coli (9.7%), Enterococcus spp. (7.7%), Klebsiella spp. (5.8%), Enterobacter spp. (5.6%) and coagulase-negative staphylococci (CoNS; 4.2%). Garenoxacin exhibited a four-fold greater activity (MIC(90), 0.06 microg/ml) compared to levofloxacin (MIC(90), 0.25 microg/ml) against oxacillin-susceptible S. aureus; and oxacillin-resistant staphylococci were more susceptible to garenoxacin (>/=90.5%) at </=4 microg/ml than ciprofloxacin or levofloxacin. Enterococcus spp. were more susceptible to garenoxacin and gatifloxacin (MIC(50), 0.5 microg/ml) than ciprofloxacin or levofloxacin (MIC(50), 2 microg/ml). All tested quinolones inhibited 64.7 to 69.7% of P. aeruginosa isolates, and the rank order of potency slightly favored ciprofloxacin (MIC(50), </=0.25 microg/ml). Similar susceptibility rates for the four quinolones were observed against E. coli (85.8-87.0%), Enterobacter spp. (90.8-94.3%) and Klebsiella spp. (89.8-95.2%) with the greatest levels of resistance recorded in Latin America for E. coli and Enterobacter spp. The occurrence of extended spectrum beta-lactamase-producing isolates (predominantly K. pneumoniae) was documented in all three monitored regions (Latin America > Europe > North America). Continued development of garenoxacin as a treatment of pathogens that commonly cause SSTIs appears to be warranted.