Levofloxacin in vitro activity: results from an international comparative study with ofloxacin and ciprofloxacin

Global prevalence and antibiotic resistance in clinical isolates of Stenotrophomonas maltophilia: a systematic review and meta-analysis

Introduction

Stenotrophomonas maltophilia is a little-known environmental opportunistic bacterium that can cause broad-spectrum infections. Despite the importance of this bacterium as an emerging drug-resistant opportunistic pathogen, a comprehensive analysis of its prevalence and resistance to antibiotics has not yet been conducted.

Methods

A systematic search was performed using four electronic databases (MEDLINE via PubMed, Embase, Scopus, and Web of Science) up to October 2019. Out of 6,770 records, 179 were documented in the current meta-analysis according to our inclusion and exclusion criteria, and 95 studies were enrolled in the meta-analysis.

Results

Present analysis revealed that the global pooled prevalence of S. maltophilia was 5.3 % [95% CI, 4.1-6.7%], with a higher prevalence in the Western Pacific Region [10.5%; 95% CI, 5.7-18.6%] and a lower prevalence in the American regions [4.3%; 95% CI, 3.2-5.7%]. Based on our meta-analysis, the highest antibiotic resistance rate was against cefuroxime [99.1%; 95% CI, 97.3-99.7%], while the lowest resistance was correlated with minocycline [4·8%; 95% CI, 2.6-8.8%].

Discussion

The results of this study indicated that the prevalence of S. maltophilia infections has been increasing over time. A comparison of the antibiotic resistance of S. maltophilia before and after 2010 suggested there was an increasing trend in the resistance to some antibiotics, such as tigecycline and ticarcillin-clavulanic acid. However, trimethoprim-sulfamethoxazole is still considered an effective antibiotic for treating S. maltophilia infections.

Development of hemiacetal esterified levofloxacin to prevent chelation with metal-containing drugs

OBJECTIVES

To avoid the chelate formation between levofloxacin (LVFX) and aluminium hydroxide in gastrointestinal tract, an ethoxycarbonyl 1-ethyl hemiacetal ester of levofloxacin (LVFX-EHE) was synthesised as a prodrug.

METHODS

The effects of aluminium hydroxide on the bioavailability of LVFX following oral administration of LVFX-EHE were investigated in rats. Furthermore, the effects of aluminium hydroxide on small intestinal absorption of LVFX and LVFX-EHE when subjected to a hydrolysis experiment using in situ everted gut sac were investigated, and the minimal inhibitory concentrations (MICs) of LVFX and LVFX-EHE for various intestinal bacteria were measured.

KEY FINDINGS

When LVFX-EHE was co-administered with and without aluminium hydroxide, the AUC_{0-4 h} values of LVFX hydrolysed from LVFX-EHE were similar to that of LVFX alone. In everted gut sac experiments, LVFX-EHE was efficiently absorbed even in the presence of aluminium ions after 1 h of incubation, whereas the absorption of LVFX decreased significantly in the presence of aluminium ions. MIC values of LVFX-EHE were far higher than LVFX.

CONCLUSIONS

This study suggests the benefit of ethoxycarbonyl 1-ethyl hemiacetal esterification of the carboxyl group of new quinolone as a prodrug which is able to avoid chelate formation.

Comparison of Levofloxacin and Cefotaxime Combined With Ofloxacin for ICU Patients With Community-Acquired Pneumonia Who Do Not Require Vasopressors

STUDY OBJECTIVES

To evaluate the efficacy and tolerability of levofloxacin (L) as monotherapy in patients with severe community-acquired pneumonia (CAP) in comparison with therapy using a combination of cefotaxime (C) plus ofloxacin (O).

DESIGN

Prospective, randomized 1:1, comparative, open, parallel-group study.

SETTING

Multinational study with 149 sites.

PATIENTS

A total of 398 randomized patients who had been admitted to the ICU with severe CAP without shock, including 308 patients in a modified intent-to-treat population and 271 patients in the per-protocol (PP) population (L group, 139 patients; C + O group, 132 patients).

INTERVENTIONS

Therapy with levofloxacin (500 mg IV, q12h) vs therapy with a C + O combination (C, 1g IV, q8h; O, 200 mg IV, q12h) for 10 to 14 days.

MEASUREMENTS AND RESULTS

The main end point was the clinical efficacy at the end of treatment (ie, the test-of-cure [TOC] visit). The statistical hypothesis was the noninferiority of L therapy to C + O therapy with a 2.5% alpha risk (unilateral) and a 15% maximum set difference. At the TOC visit, a clinical success was observed in 79.1% of patients (L group) and 79.5% of patients (C + O group) in the PP population (difference, -0.4%; 95% confidence interval [CI], -10.79 to 9.97% without adjustment for simplified acute physiology score [SAPS] II at inclusion; difference, -0.3%; 95% CI, -10.13 to 9.58% with adjustment for SAPS II). A satisfactory bacteriologic response was present in 73.7% of L group patients and 77.5% of C + O group patients, including responses of 75.7% and 70.3%, respectively, in the L group and C + O group in the Streptococcus pneumoniae-documented population. In the safety analysis, 20 patients in the L group (10.3%) and 16 patients in the C + O group (8.0%) experienced at least one adverse event that was considered to be treatment-related.

CONCLUSION

L therapy was at least as effective as the combination therapy of C + O in the treatment of a subset of patients with CAP requiring ICU admission. This conclusion cannot be extrapolated to patients requiring mechanical ventilation or vasopressors (ie, those patients in shock).

A study on the toxicity of intravitreal levofloxacin in rabbits

PURPOSE

To investigate the retinal toxicity of different doses of intravitreal injections of levofloxacin in a rabbit model, which is the levorotatory component of ofloxacin and approximately twice as potent as ofloxacin and highly active in vitro against gram-positive and -negative bacteria, and anaerobic bacteria including many ocular pathogens.

METHODS

Sixteen albino rabbits were used in this study, and divided four groups. Levofloxacin in doses of 50, 100, 250 and 500 microg was injected into the midvitreous of rabbit's left eyes. The other eye served as a control and received normal saline solution. Indirect ophthalmoscopy, electroretinography (ERG) and light microscopy were used for retinal toxicity of levofloxacin. ERGs were recorded before injection and at 1(st) day, 1(st), 2(nd) and 4(th) weeks. At the end of follow-up period, the rabbits were killed and the eyes were enucleated for histologic evaluation.

RESULTS

Intravitreal injections of 50, 100, 250 and 500 microg levofloxacin did not cause any deterioration of the a-wave, b-wave or oscillatory potentials of ERG throughout the follow-up period of 4 weeks. No evidence of retinal toxicity was observed by indirect ophthalmoscopy and light microscopy in any case.

CONCLUSIONS

In therapeutic doses of 500 microg or less, intravitreal levofloxacin does not have retinal toxicity in rabbit eyes and this dose was well above the MIC(90) values of ocular pathogens that cause endophthalmitis. If future studies in other species confirm our findings, intravitreal levofloxacin may be a potentially important drug in the treatment and prevention of clinical bacterial endophthalmitis.

Comparison of Etest, agar dilution, broth microdilution and disk diffusion methods for testing in vitro activity of levofloxacin against Staphylococcus spp. isolated from neutropenic cancer patients

The susceptibility to levofloxacin of 194 consecutive staphylococcal (45 Staphylococcus aureus and 149 coagulase-negative staphylococci) isolates from neutropenic patients was determined by Etest and the results compared with those obtained using NCCLS-methods (broth microdilution, agar dilution and disk diffusion). Overall agreement at +/- 1log(2) dilution for Etest compared with broth microdilution and agar dilution was 99.0 and 83.5%, respectively. The Etest category agreement with broth microdilution and disk diffusion was 95.9 and 89.7%, respectively. Comparison of categories with Etest and agar dilution method gave only 67.0% absolute categorical agreement, with 29.9% minor errors and 10.7% major errors. No very major errors occurred by the four methods tested. Our results show that Etest is a valid alternative to the reference NCCLS-methods for monitoring the clinical usefulness of levofloxacin against staphylococci isolates from neutropenic patients.

Susceptibility to fluoroquinolones among commonly isolated Gram-negative bacilli in 2000: TRUST and TSN data for the United States. Tracking Resistance in the United States Today. The Surveillance Network

From January to May 2000, as part of the Tracking Resistance in the United States Today (TRUST) surveillance initiative, clinical isolates of Enterobacteriaceae (n=2519) and non-fermentative Gram-negatives (n=580) were prospectively collected from 26 hospital laboratories across the United States. Isolates were tested for susceptibility to three fluoroquinolones (ciprofloxacin, levofloxacin, gatifloxacin) and seven other agents. In addition, data for the same period were collected from The Surveillance Network (TSN) Database-USA, an electronic surveillance network that receives data from more than 200 laboratories in the US. Both surveillance methods produced similar results. Against isolates of Enterobacteriaceae, imipenem was the most active agent, followed by the fluoroquinolones; > or = 86.7% of isolates of all species of Enterobacteriaceae except Providencia spp. were susceptible to fluoroquinolones by TRUST and TSN surveillance. TRUST identified differences in susceptibility to the three fluoroquinolones of > or = 2% for Citrobacter spp., Enterobacter cloacae, Proteus mirabilis and Serratia marcescens. Isolates of P. mirabilis were considerably more susceptible to levofloxacin (94.0%) than to ciprofloxacin (87.7%) and gatifloxacin (87.7%). Other results from TRUST included Pseudomonas aeruginosa being slightly more susceptible to ciprofloxacin (73.5%) and levofloxacin (73.0%) than gatifloxacin (71.0%). Imipenem was the only compound with significant activity (95.1% susceptible, TRUST; 87.4% susceptible, TSN) against Acinetobacter baumannii, but it was inactive against Stenotrophomonas maltophilia. S. maltophilia isolates were more susceptible to levofloxacin and gatifloxacin (77.7-79.8%) than ciprofloxacin (29.7-33.0%). Against 513 urinary isolates of Escherichia coli in TRUST, levofloxacin, gatifloxacin and ciprofloxacin were equipotent. Age and gender had no clear effect on the activity of levofloxacin, ciprofloxacin or gatifloxacin. Similar results for all three fluoroquinolones were seen in outpatients and inpatients. TRUST and TSN data indicated that resistance rates had not changed appreciably for any compound studied since a similar study conducted in 1999. TRUST centralized in vitro and electronic (TSN) surveillance methods provided an effective strategy for monitoring trends in resistance.

Levofloxacin in the empirical treatment of patients with suspected bacteraemia/sepsis: comparison with imipenem/cilastatin in an open, randomized trial

An open, randomized, multinational, multicentre study was conducted to compare the efficacy, safety and tolerability of levofloxacin 500 mg twice daily with imipenem/cilastatin 1 g iv three-times daily in the treatment of hospitalized adult patients with clinically suspected bacteraemia/ sepsis. Levofloxacin patients could change from iv to oral administration after a minimum of 48 h iv treatment if clinical signs and symptoms of sepsis had improved. The primary efficacy analysis was based on the clinical and bacteriological response at clinical endpoint. A total of 503 patients were randomized and 499 included in the intent-to-treat population. The per-protocol population comprised 287 patients with bacteriologically proven infection. Clinical cure rates at clinical endpoint in the intent-to-treat population and per-protocol population were 77% (184/239) and 89% (125/140), respectively, for levofloxacin and 68% (178/260) and 85% (125/147), respectively, for imipenem/cilastatin. At follow-up, the cure rates in the per-protocol population were 84% for levofloxacin and 69% for imipenem/cilastatin. The 95% confidence interval for both populations showed that levofloxacin was as effective as imipenem/cilastatin. A satisfactory bacteriological response was obtained in 87% (96/110) of levofloxacin patients and 84% (97/116) of imipenem/cilastatin patients at clinical endpoint. Adverse events possibly related to the study drug were reported in 74 (31%) levofloxacin patients and 79 (30%) imipenem/cilastatin patients. There were no clinically appreciable differences between the treatment groups. Levofloxacin 500 mg twice daily, either iv or as sequential iv/oral therapy, was as effective and well tolerated as imipenem/cilastatin 1 g iv three-times daily in the treatment of hospitalized patients with suspected bacteraemia/sepsis.

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.

Levofloxacin versus cefuroxime axetil in the treatment of acute exacerbation of chronic bronchitis: results of a randomized, double-blind study

A randomized, double-blind, double-dummy, three-arm parallel design, multicentre study was conducted among adult patients with acute exacerbation of chronic bronchitis (AECB) in order to compare the efficacy and safety of two different doses of levofloxacin with cefuroxime axetil. A total of 832 patients were randomized to receive oral levofloxacin (250 mg od or 500 mg od) or oral cefuroxime axetil (250 mg bd) for 7-10 days. The primary efficacy analysis was based on the clinical response in patients with bacteriologically confirmed AECB, determined 5-14 days after the end of therapy (per-protocol population). Of 839 patients enrolled (at 71 centres in 14 countries), seven were not treated, giving an intention-to-treat (ITT) population of 832. In total, 281 patients received levofloxacin 250 mg, 280 received levofloxacin 500 mg and 271 received cefuroxime axetil. The cure rates in the ITT population were: levofloxacin 250 mg, 70% (196/281); levofloxacin 500 mg, 70% (195/280); cefuroxime axetil, 61% (166/271); those in the per-protocol population were: 78% (121/156), 79% (108/137) and 66% (88/134), respectively. Both doses of levofloxacin were at least as effective as cefuroxime axetil and were active against the main pathogens of clinical relevance (Haemophilus influenzae, Streptococcus pneumoniae and Moraxella catarrhalis). All three treatment regimens were equally well tolerated. In conclusion, the results show that levofloxacin (250 mg and 500 mg) od is effective and well tolerated in the treatment of AECB in adult patients.

Italian survey on comparative levofloxacin susceptibility in 334 clinical isolates of Pseudomonas aeruginosa

A national survey on susceptibility patterns of 334 Pseudomonas aeruginosa isolates from intensive care units and hematology and oncology wards from 13 Italian hospitals compared the in vitro activity of levofloxacin, an injectable oral fluoroquinolone, to those of ciprofloxacin, ofloxacin, ceftazidime, imipenem, amikacin, and gentamicin. Amikacin and imipenem had the best susceptibility profiles. The activity of levofloxacin was superior to those of the other quinolones and was comparable to that of ceftazidime. The effect of levofloxacin in vitro on P. aeruginosa clinical isolates suggests that further clinical investigations are warranted.

The bactericidal activity of levofloxacin against ampicillin-resistant and ampicillin-susceptible Haemophilus influenzae in comparison with ofloxacin, ciprofloxacin and sparfloxacin

The bactericidal activity of levofloxacin against four Haemophilus influenzae clinical isolates (two ampicillin-resistant and two susceptible) was compared with that of ofloxacin, ciprofloxacin and sparfloxacin at concentrations simulating the peak serum concentrations obtained with the recommended oral doses. Bactericidal activity was assessed using time-kill curves and minimum kill-time values. Both concentrations of levofloxacin rapidly killed all the study strains, with mean kill times of 4 h and no viable bacteria remaining after 18-h exposure. The bactericidal activities of levofloxacin, ofloxacin and sparfloxacin were similar. The minimum kill-times for both concentrations of ciprofloxacin were 28-35% longer than those of levofloxacin. These results support the use of levofloxacin for H. influenzae infections, including ampicillin-resistant strains.

Levofloxacin. Its use in infections of the respiratory tract, skin, soft tissues and urinary tract

Levofloxacin, the optically pure levorotatory isomer of ofloxacin, is a fluoroquinolone antibacterial agent. Like other fluoroquinolones, it acts on bacterial topoisomerase and has activity against a broad range of Gram-positive and Gram-negative organisms. Levofloxacin also appears to have improved activity against Streptococcus pneumoniae compared with ciprofloxacin or ofloxacin. Levofloxacin distributes well and achieves high levels in excess of plasma concentrations in many tissues (e.g., lung, skin, prostate). High oral bioavailability allows switching from intravenous to oral therapy without dosage adjustment. In patients with mild to severe community-acquired pneumonia receiving treatment for 7 to 14 days, oral levofloxacin was similar in efficacy to amoxicillin/clavulanic acid, and intravenous and/or oral levofloxacin was superior to intravenous ceftriaxone and/or oral cefuroxime axetil. With levofloxacin use, clinical success (clinical cure or improvement) rates were 87 to 96% and bacteriological eradication rates were 87 to 100%. In the 5- to 10-day treatment of acute exacerbations of chronic bronchitis, oral levofloxacin was similar in efficacy to oral cefuroxime axetil or cefaclor. Levofloxacin resulted in clinical success in 78 to 94.6% of patients and bacteriological eradication in 77 to 97%. Oral levofloxacin was also similar in efficacy to amoxicillin/clavulanic acid or oral clarithromycin in patients with acute maxillary sinusitis treated for 7 to 14 days. Equivalence between 7- to 10-day therapy with oral levofloxacin and ciprofloxacin was seen in patients with uncomplicated skin and soft tissue infections. Clinical success was seen in 97.8 and 96.1% of levofloxacin recipients and bacteriological eradication in 97.5 and 93.2%. Complicated urinary tract infections, including pyelonephritis, responded similarly well to oral levofloxacin or ciprofloxacin for 10 days or lomefloxacin for 14 days. Clinical success and bacteriological eradication rates with levofloxacin occurred in 92 to 93.3% and 93.6 to 94.7% of patients.

CONCLUSIONS

Levofloxacin can be administered in a once-daily regimen as an alternative to other fluoroquinolones in the treatment of infections of the urinary tract, skin and soft tissues. Its more interesting use is as an alternative to established treatments of respiratory tract infections. S. pneumoniae appears to be more susceptible to levofloxacin than to ciprofloxacin or ofloxacin. Other newer fluoroquinolone agents that also have enhanced in vitro antipneumococcal activity may not share the well established tolerability profile of levofloxacin, which also appears to improve on that of some older fluoroquinolones.

Successful treatment of murine listeriosis and salmonellosis with levofloxacin

Levofloxacin (L-ofloxacin) is a fluoroquinolone derivative. It is the active substance contained in ofloxacin with a broad spectrum of antibacterial activity against both Gram-negative and Gram-positive bacteria. In this work we examined the activity of levofloxacin against the facultative intracellular bacteria Listeria monocytogenes and Salmonella typhimurium in vitro, in tissue culture and in animal models of infection. The minimum inhibitory concentrations (MICs) MIC90 for Salmonella enterica and L. monocytogenes were 0.078 mg/l and 4 mg/l, respectively. Levofloxacin was bactericidal against L. monocytogenes and S. typhimurium because 8 x MIC killed 90% of the initial inoculum of L. monocytogenes EGD and S. typhimurium LT2 within 4 hours and 3 hours, respectively. Levofloxacin was more effective than ampicillin against L. monocytogenes EGD infecting tissue culture cells. Also in tissue culture cells infected with S. typhimurium LT2, levofloxacin was slightly more effective than ciprofloxacin. In animal models of infection, levofloxacin was as potent as the reference substances. In conclusion, levofloxacin is a candidate for the treatment of infections caused by facultative intracellular Gram-positive and Gram-negative bacteria.

Bactericidal effects of levofloxacin in comparison with those of ciprofloxacin and sparfloxacin

OBJECTIVE: To investigate and compare the in vitro activity of levofloxacin with the activities of ciprofloxacin and sparfloxacin. METHODS: The following experiments were performed: (1) comparative studies of the rate of killing by the three quinolones of different strains of Streptococcus pneumoniae at a concentration corresponding to the 1-h serum level following a 500-mg dose in humans; (2) comparative studies of the rate of killing by levofloxacin and ciprofloxacin of different strains of Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa at the same concentrations as above; (3) comparative studies of the rate of killing by levofloxacin at four different concentrations of reference and clinical strains of Streptococcus pneumoniae, Staphylococcus aureus, E. coli and P. aeruginosa. RESULTS: Levofloxacin exhibited statistically significantly higher bactericidal activity than sparfloxacin after 2 and/or 3 h against all strains of Streptococcus pneumoniae. Compared to ciprofloxacin, levofloxacin showed a statistically significantly higher bactericidal activity after 2 and/or 3 h against all strains of Streptococcus pneumoniae except the one resistant to both penicillin and cefotaxime. No differences in killing rate between levofloxacin and ciprofloxacin were seen against Staphylococcus aureus, E. coli and P. aeruginosa, with almost complete killing after 3 h of the P. aeruginosa strains and after 6 h for the E. coli strains. No concentration-dependent killing was seen at concentrations above 4xMIC of levofloxacin against Staphyloccus aureus, E. coli and P. aeruginosa. CONCLUSION: Levofloxacin was shown to be active against both Gram-positive and Gram-negative bacteria. In terms of MIC values, ciprofloxacin was the most active drug against the Gram-negative organisms, and sparfloxacin against the strains of Streptococcus pneumoniae, but levofloxacin exhibited a similar or even better bactericidal activity against the investigated strains compared with the other two fluoroquinolones when killing curves were compared.

In vivo efficacies of levofloxacin and ciprofloxacin in acute murine hematogenous pyelonephritis induced by methicillin-susceptible and-resistant Staphylococcus aureus strains

Levofloxacin, the active L-isomer of ofloxacin, has demonstrated strong activity against Staphylococcus aureus both in vitro and in vivo. In a murine model of hematogenous pyelonephritis, the in vivo efficacies of levofloxacin and ciprofloxacin were evaluated against two methicillin-susceptible and two methicillin-resistant S. aureus strains. All four isolates had virtually identical susceptibilities to levofloxacin and ciprofloxacin. Pyelonephritis was induced in carrageenan-primed mice by an intravenous injection of 0.5 ml of 10(7) CFU of methicillin-susceptible S. aureus isolates per ml or 10(8) CFU of methicillin-resistant S. aureus isolates per ml. At 1 h postinfection, the mice were treated orally with levofloxacin or ciprofloxacin once a day or twice a day (total daily dose of 20 to 160 mg/kg of body weight) for 4 days. Mice were euthanized 24 h after the final treatment, and the kidneys were excised and weighed. The kidneys were prepared for histological examination or were homogenized to determine the numbers of CFU per gram of tissue quantitatively. The reduction in the mean log10 number of CFU per gram as a function of total daily dose was recorded. A dose-response analysis showed that levofloxacin was superior to ciprofloxacin for all four isolates at any dose or regimen tested, independent of the methicillin susceptibility of the isolates. By using an inverse prediction technique, the equivalent effective doses of levofloxacin (once a day) were less than those of ciprofloxacin (twice a day) by 5.2 and 3.2 times, respectively, for methicillin-susceptible S. aureus 9039 and 3087. For methicillin-resistant S. aureus 667 and 2878, the equivalent effective doses of levofloxacin (once a day) were less than those of ciprofloxacin (twice a day) by 4.1 and 6.4 times, respectively. In a separate study, histological examination of all infected, untreated mice showed moderate to marked hematogenous pyelonephritis. Levofloxacin-treated mice (40 mg/kg once a day) showed no evidence of pyelonephritis in the kidneys, whereas the kidneys of mice treated with the same dose of ciprofloxacin showed only a reduction in the severity of the lesions. Treatment with ciprofloxacin (80 mg/kg twice a day) demonstrated a histology comparable to that of treatment with levofloxacin (40 mg/kg once a day). Levofloxacin (40 mg/kg once a day) reduced the log10 numbers of CFU per gram by 5 log10; however, ciprofloxacin (80 mg/kg twice a day) reduced the numbers of CFU per gram by only 3 log10. In the present murine model of pyelonephritis, levofloxacin was superior to ciprofloxacin in preventing pyelonephritis and eradicating S. aureus.

Prevalence of resistance to three fluoroquinolones: assessment of levofloxacin disk test error rates and surrogate predictors of levofloxacin susceptibility. AST Surveillance Group

More than 3,000 consecutive clinical bacterial isolates from 10 U.S. medical centers were subjected to standard broth microdilution and disk diffusion tests to determine their susceptibilities to levofloxacin, ofloxacin, D-ofloxacin, and ciprofloxacin. Levofloxacin was confirmed to be twice as active as ofloxacin and to have activity comparable to that of ciprofloxacin, with minor variations in activity against some species. The prevalence of resistant isolates was 7.1% to levofloxacin, 9.3% to ciprofloxacin, and 11.2% to ofloxacin. The susceptibilities of some species to the quinolones were less than those reported in previous studies. Pseudomonas aeruginosa isolates had the greatest variability in their susceptibilities to the three drugs between the participating centers. Two proposed zone size breakpoints for levofloxacin disk tests yielded similar low error rates. Ofloxacin and ciprofloxacin susceptibility test results correlated reasonably well with those of levofloxacin and could be used as surrogate indicators of levofloxacin susceptibility, but that resulted in some serious errors, and thus, direct testing of levofloxacin susceptibility is preferable. Replicate testing of standard quality control strains confirmed the established and proposed quality control parameters for all three quinolones tested.