Multicenter in vitro evaluation of lomefloxacin (NY-198, SC-47111), including tests against nearly 7,000 bacterial isolates and preliminary recommendations for susceptibility testing

Total Synthesis of C-8 Hydroxyl Substituted Lomefloxacin as the Photolysis Impurity

Objective:

Photochemical decomposition of lomefloxacin (Lom) is supposed to result in the generation of C-8 substituted impurity and accompanied fluoride. The existence and amount of C-8 hydroxyl substituted Lom could be proposed as the marker to the stability and process consistency. The specific C-8 hydroxyl substituent impurity (1-ethyl-6-fluoro-8-hydroxy-7-(3-methylpiperazin-1-yl )-4-oxo-1,4-dihydroquinoline-3-carboxylic acid) was designed and synthesized to be available.

Method:

2,4,5-trifluoro-3-methoxybenzoic acid as the initial reactant was subjected to a series of seven-step reactions, such as acylation, condensation with trans N,N-dimethylamino ethyl acrylate, N-ethylation, cyclization, hydrolysis, condensation with piperazine and acidification. The resultant substance was then purified using HPLC and C18 solid-phase extraction. The structure of C-8 hydroxyl substituted Lom was identified with 1H-NMR, 13C-NMR and HRMS spectroscopes, as well as the purity was determined by HPLC.

Conclusion:

C-8 hydroxyl substituted Lom was successfully synthesized and purified with purity more than 96%. This photolysis impurity offers an alternative for not only further generic Lom active pharmaceutical ingredient development involved in quality control and consistency evaluation, but also research for the mechanism underlying Lom-induced photosensitivity.

Comparative quantification of the in vitro activity of veterinary fluoroquinolones

The aim of this study was to compare the in vitro antimicrobial activity of the veterinary fluoroquinolones against a panel of recently isolated porcine and bovine bacterial pathogens. The study used enrofloxacin as a benchmark against which other agents were compared, being the most common fluoroquinolone used in treatment of bovine and porcine infections. The activity of ciprofloxacin was also assessed as it is the main metabolite of enrofloxacin in cattle. Enrofloxacin and ciprofloxacin generally showed higher antibacterial activity, in terms of MIC(50) values, for most pathogen species when compared with marbofloxacin, difloxacin, danofloxacin and norfloxacin. Ciprofloxacin showed significantly greater in vitro antibacterial activity than enrofloxacin against M. haemolytica, P. multocida and E. coli, whereas enrofloxacin showed greater activity than ciprofloxacin against S. aureus. Marbofloxacin was significantly more active than enrofloxacin against M. haemolytica, E. coli and B. bronchiseptica but less active against P. multocida, S. aureus, coagulase negative Staphylococci, S. dysgalactiae, S. uberis, A. pleuropneumoniae and S. suis. Danofloxacin was significantly less active than enrofloxacin against P. multocida, E. coli, S. uberis, A. pleuropneumoniae and S. suis. Enrofloxacin and its metabolite ciprofloxacin showed the highest in vitro activities against most bovine pathogens tested and the porcine pathogens also showed a high degree of sensitivity to enrofloxacin. These data facilitate further pharmacokinetic/pharmacodynamic comparison of fluoroquinolones currently used in veterinary medicine.

Modeling approach to diameter breakpoint determination

In determining zone diameter breakpoints, the error-rate bounded method focuses directly on the observed discrepancy percentages (very major, major, and minor). These percentages, however, are quite variable due to the number of isolates investigated, the drug-specific relationship between MIC and zone diameter, the location of the isolates relative to the MIC intermediate zone, and the inherent variability of each test. To overcome potential sampling problems, a hierarchical model is proposed which explicitly accounts for each of these factors and probabilities from this model are used to determine diameter breakpoints. A simulation study is performed to demonstrate the improved consistency of this model-based procedure. Application to three published scatterplots demonstrate its interpretability advantages.

Topical lomefloxacin 0.3% twice daily versus tobramycin 0.3% in acute bacterial conjunctivitis: A multicenter double-blind phase III study

AIMS/BACKGROUND

To evaluate in a double-masked comparative, prospective, randomized multicenter trial the efficacy of lomefloxacin 0.3% eye drops twice daily and of tobramycin eye drops 4 times daily in patients with acute bacterial conjunctivitis.

METHODS

Ninety-nine subjects were enrolled: 50 were treated with lomefloxacin 0.3% eye drops twice daily and 49 with tobramycin 0.3% eye drops 4 times daily. In all patients, conjunctival swabbing and assessment of objective signs and of subjective symptoms were performed.

RESULTS

There was no statistical difference for any individual sign or symptom or for the sum score of either key or other signs and symptoms at any of the examination days. The sum score of both key and other signs and symptoms decreased in both groups at day 3-4 as compared to baseline values (p < 0.0001). The decrease in both these scores continued significantly from day 3-4 to day 7-8 (p < 0.05) and was similar in the two treatment groups (p > 0.4). The lowest resistance rate was seen in lomefloxacin (3.5%) and in neomycin (7.0%), while tobramycin showed resistance in 10 out of 88 resistance strains (11.4%).

CONCLUSION

Both lomefloxacin 0.3% twice daily and tobramycin 0.3% administered 4 times daily were well tolerated and showed a high degree of clinical and microbiological efficacy in the treatment of acute bacterial conjunctivitis. Lomefloxacin caused less resistance than other antibiotics evaluated.

Topical lomefloxacin twice daily compared with fucidic acid in acute bacterial conjunctivitis

Forty-five patients with presumed acute bacterial conjunctivitis were treated in an investigator-masked randomized multicenter study with either lomefloxacin 0.3% or fucidic acid 1% eye drops twice daily. Clinical signs and symptoms were rated by slit-lamp examination and conjunctival swab cultures were performed to evaluate clinical and microbiological efficacy. A total of 57 ocular isolates were tested for susceptibility to nine antibiotics. A significant decrease in clinical symptomatology was achieved by both treatments with a gradual improvement over the treatment period of 7-9 days. Bacteriological recovery was frequently achieved already at the first control visit (day 3-5), but the recovery rate was statistically significant (p = 0.014) only in the lomefloxacin group. The relatively high in vitro resistance rate (46%) to fucidic acid was not reflected by lower clinical efficacy. Two unrelated adverse events (one in each treatment group) and minimal local intolerance problems were observed in both treatment groups. A significantly higher incidence of burning sensation was observed with fucidic acid than with lomefloxacin (p < 0.01). All four treatment failures in the study occurred in the fucidic acid group. Lomefloxacin 0.3% ophthalmic solution demonstrated a high efficacy and good tolerance in the management of acute bacterial conjunctivitis.

Update of lomefloxacin in vitro activity and spectrum. A multicenter trial testing contemporary pathogens following Food and Drug Administration validation guidelines. Lomefloxacin Activity Study Group

The United States Food and Drug Administration recently recommended that the antimicrobial product package insert (PPI) subsection on microbiology be annually validated with regard to the compound's spectrum and potency. To address this request, a nine-laboratory trial was organized to test (two methods) lomefloxacin, a newer fluoroquinolone, and nine comparison drugs against PPI-listed pathogens (1934 strains). A broad geographic sampling (nine medical centers) was achieved, and lomefloxacin was determined to be active [minimum inhibitory concentration (MICs), < or = 2 micrograms/ml for > or = 90% of strains] for all PPI-listed species except Pseudomonas aeruginosa, Citrobacter freundii, and Providencia rettgeri (42%-87% inhibited). Comparison fluoroquinolones also had a similarly compromised spectrum of activity against these species. Additional organism species, including Neisseria gonorrhoeae, N. meningitidis, Salmonella enteriditis, and Shigella species, should be added to the lomefloxacin PPI (MIC90s, 0.03-0.25 microgram/ml) following data generated in this study. These in vitro results indicate that lomefloxacin remains active against the vast majority of clinically "indicated" species, and that it has a spectrum compatible with other marketed fluoroquinolones for these tested pathogens, monitored in 1994.

In vitro and in vivo evaluations of A-80556, a new fluoroquinolone

A-80556 is a novel fluoroquinolone with potent antibacterial activity against gram-positive, gram-negative, and anaerobic organisms. A-80556 was more active than ciprofloxacin, ofloxacin, lomefloxacin, and sparfloxacin against gram-positive bacteria. A-80556 was particularly active against Staphylococcus aureus (MIC for 90% of isolates [MIC90], 0.12 microgram/ml, relative to fluoroquinolone-susceptible strains) and Streptococcus pneumoniae (MIC90, 0.12 microgram/ml). A-80556 was also the most active of the quinolones tested against ciprofloxacin-resistant S. aureus, with an MIC90 of 4.0 micrograms/ml; that of ciprofloxacin was > 128 micrograms/ml. However, the significance of this activity is not known. A-80556 was slightly less active against Escherichia coli (MIC90, 0.06 microgram/ml) and other enteric organisms than ciprofloxacin (MIC90 for E. coli, < or = 0.03 microgram/ml). A-80556 was slightly less active against Pseudomonas aeruginosa (MIC90, 4.0 micrograms/ml) than ciprofloxacin (MIC90, 2.0 micrograms/ml) and more active against Acinetobacter spp. (respective MIC90s, 0.12 and 0.5 microgram/ml). A-80556 was also the most active compound against anaerobes. Against Bacteroides fragilis, the MIC90 of A-80556 was 2.0 micrograms/ml; that of ciprofloxacin was 16 micrograms/ml. The in vivo efficacy of A-80556 in experimental models with both gram-positive and gram-negative infections was consistent with the in vitro activity and pharmacokinetics and oral absorption in mice.

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

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

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

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

Antimicrobial activities of two investigational fluoroquinolones (CI-960 and E4695) against over 100 Legionella sp. isolates

The antimicrobial activities of two investigational fluoroquinolones (CI-960 and E4695) were compared with those of five similar compounds and four comparison drugs against 103 strains of Legionella pneumophila and five other Legionella species type strains. When concentrations inhibiting 90% of strains tested (MIC90s) for L. pneumophila were determined, CI-960 and temafloxacin emerged as the most active (0.015 microgram/ml) and were followed in potency by E4695 (0.03 microgram/ml). This activity was two- to fourfold greater than that of the reference drug, ciprofloxacin, and approached that of rifampin (MIC90, 0.008 microgram/ml). All fluoroquinolones studied were more active than erythromycin (MIC90, 0.5 microgram/ml). These two investigational fluoroquinolones appear well suited for further in vivo study of legionellosis therapy.

Antibacterial activity of fluoroquinolones local clinical isolates from a referral center in Riyadh

A total of 1,034 clinical isolates from a tertiary care center were tested against six fluoroquinolones, namely norfloxacin, ciprofloxacin, lomefloxacin, sparfloxacin, temafloxacin, and CI-960. Bacteria tested consisted of 579 strains of Enterobacteriaceae, 98 pseudomonads, 51 Acinetebacter, 56 enterococci and 250 isolates of staphylococci. All six fluoroquinolones showed excellent in vitro activity inhibiting >90% of Escherichia coli at an MIC of < 0.03-0.5 mg/L, Klebsiella pneumoniae at 0.12-2.0 mg/L, Enterobacter at 0.12-2.0 mg/L, Serratia marcescens at 0.12-2.0 mg/L, Pseumodonas aeruginosa at 0.5-2.0 mg/L, Staphylococcus aureus at < 0.03-1.0 mg/L, and coagulase negative staphylococci at an MIC of 0.12-2.0 mg/L Xanthomonas maltophilia showed some resistance to norfloxacin, ciprofloxacin, lomefloxacin and temafloxacin, but was inhibited by sparfloxacin and CI-960. A majority of isolates of enterococci were resistant to norfloxacin, ciprofloxacin, lomefloxacin, and CI-960, but sparfloxacin and temafloxacin inhibited 92% and 82% of these strains, respectively.

Interpretive criteria for susceptibility testing of CI-960 (PD127391, AM-1091), fleroxacin, lomefloxacin, and temafloxacin against Neisseria gonorrhoeae, including drug stability in GC agar medium

CI-960, fleroxacin, lomefloxacin, and temafloxacin were tested against over 100 strains of Neisseria gonorrhoeae. Each organism was tested in triplicate by using agar dilution and disk diffusion methods recommended by the National Committee for Clinical Laboratory Standards. CI-960 was the most potent compound, with a MIC against 90% of the strains tested of 0.008 microgram/ml, and the least active was fleroxacin (MIC against 90% of strains, 0.12 microgram/ml). Only the susceptible interpretive category was recommended for the CI-960 tests as follows: 5-micrograms disk, greater than or equal to 39 mm (MIC correlate, less than or equal to 0.12 microgram/ml). Three interpretive categories were proposed for the other fluoroquinolones as follows: fleroxacin, 5-micrograms disk susceptible at greater than or equal to 33 mm (MIC correlate, less than or equal to 0.25 microgram/ml), intermediate at 28 to 32 mm (MIC correlate, 0.5 microgram/ml), and resistant at less than or equal to 27 mm (MIC correlate, greater than 0.5 microgram/ml); lomefloxacin, 10-micrograms disk susceptible at greater than or equal to 35 mm (MIC correlate, less than or equal to 0.12 microgram/ml), intermediate at 28 to 34 mm (MIC correlates, 0.25 to 0.5 microgram/ml), and resistant at less than or equal to 27 mm (MIC correlate, greater than 0.5 microgram/ml); and temafloxacin, 5-micrograms disk susceptible at greater than or equal to 36 mm (MIC correlate, less than or equal to 0.06 microgram/ml), intermediate at 28 to 35 mm (MIC correlates 0.12 to 0.25 microgram/ml), and resistant at less than or equal to 27 mm (greater than 0.25 microgram/ml). Interpretive agreement between disk diffusion results and the MICs was 100% for each agent, with the exception of lomefloxacin, which had a 0.9% minor error. All drugs were stable in GC agar medium for at least 21 days when stored at 2 to 5 degrees C.

Fluoroquinolone (Lomefloxacin) International Surveillance Trial: a report of 30 months of monitoring in vitro activity

The antimicrobial activity and spectrum of lomefloxacin were assessed by standardized disk diffusion methods in 36 countries. More than 500,000 facultative organisms were tested during the first 30 months of a 3-year monitoring interval. Lomefloxacin demonstrated inhibition (zones greater than or equal to 19 mm) of greater than 90% of Enterobacteriaceae, greater than 99% of Moraxella (Branhamella) catarrhalis, greater than 98% of Haemophilus spp., and 91% of Staphylococcus aureus strains. Pseudomonas spp., especially Pseudomonas aeruginosa (18% resistance), were considered moderately susceptible, as were most strains of streptococci and enterococci. Some variation of national/regional fluoroquinolone resistance rates was observed, using lomefloxacin as an index or indicator drug, with the highest numbers of resistant strains being isolated in France. However, these data demonstrated a wide spectrum of lomefloxacin activity in all nations monitored.

Lomefloxacin: microbiologic assessment and unique properties

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

Interpretive criteria and quality control guidelines for lomefloxacin and meropenem in susceptibility tests of Haemophilus influenzae using Haemophilus test medium

Lomefloxacin and meropenem were tested in a multilaboratory study to establish susceptibility testing interpretive criteria and quality control (QC) guidelines for Haemophilus influenzae using Haemophilus test medium (HTM). Interpretive criteria were established by using triplicate testing of 102 representative H. influenzae strains. Only a susceptible category was proposed for lomefloxacin (greater than or equal to 22 mm and less than or equal to 2 micrograms/ml) and meropenem (greater than or equal to 13 mm and less than or equal to 4 micrograms/ml) due to the lack of resistant isolates. QC range for H. Influenzae ATCC 49247 were established using multiple HTM agar and broth base lots, three disk lots for each drug, and a number of test replicates consistent with the National Committee for Clinical Laboratory Standards M23-T guideline.

Lomefloxacin. A review of its antibacterial activity, pharmacokinetic properties and therapeutic use

The antibacterial efficacy of oral lomefloxacin has been investigated in a wide variety of infections, including respiratory and uncomplicated and complicated urinary tract infections, obstetric, gynaecological, joint, skin, oral, ear, nose, throat and eye infections. It has also been used as an otic solution in patients with otitis media and as an ophthalmic solution in the treatment of eye infections. In clinical trials its efficacy is equivalent to that of other quinolones and it is at least as effective as other antibacterial drugs ordinarily used in these infections. Lomefloxacin offers certain advantages compared with other quinolone antibacterial drugs in that it may be conveniently administered once daily and theophylline dosage adjustment does not appear to be necessary in patients receiving this bronchodilator concomitantly. Thus, orally administered lomefloxacin should prove a useful broad spectrum antibacterial drug for a wide variety of clinical infections.

In vitro antimicrobial activity of sparfloxacin (AT-4140, CI-978, PD 131501) compared with numerous other quinolone compounds

Sparfloxacin (AT-4140, CI-978, PD 131501) was tested against over 800 recent bacteremic strains and compared with ciprofloxacin and six other fluoroquinolones. The 90% minimum inhibitory concentration (MIC90) ranges for the Enterobacteriaceae species were (a) sparfloxacin, 0.03-1 microgram/ml and (b) ciprofloxacin, 0.015-0.25 microgram/ml. Moraxella catarrhalis, Haemophilus influenzae, and Neisseria gonorrhoeae were very susceptible to sparfloxacin (MIC90s, 0.004- less than or equal to 0.03 microgram/ml) and the other comparison drugs. Staphylococcus aureas and other staphylococci were generally susceptible to the tested fluoroquinolones but very susceptible to sparfloxacin and WIN 57273. All beta-hemolytic streptococci, enterococci, and pneumococci had sparfloxacin MICs of less than or equal to 1 microgram/ml. Sparfloxacin was quite active against anaerobic bacteria including Bacteroides fragilis gr. and Gram-positive strains (MIC90s, less than or equal to 2 micrograms/ml). The most resistant enteric bacilli were among Serratia marcescens and the Proteae, especially the Providencia spp. (two- to eightfold higher MICs). Pseudomonas aeruginosa strains were also susceptible to sparfloxacin (MIC90, 2 micrograms/ml). Magnesium ions, CO2 incubation, and low pH had some adverse effect on sparfloxacin MICs, and resistance development was documented among current clinical isolates of staphylococci, pseudomonas, and some enteric species.

Pharmacokinetics of quinolones: newer aspects

Differences in pharmacokinetic properties are emerging as important determinants in distinguishing among clinical uses of individual new quinolone antimicrobial agents. Selected data on pharmacokinetics, new pharmacokinetic studies, and pharmacodynamics are reviewed, with reference to norfloxacin, ciprofloxacin, ofloxacin, pefloxacin, enoxacin, fleroxacin, lomefloxacin, and other new quinolones. Considering pharmacokinetics, oral bioavailability is excellent (greater than 95%) for most quinolones. Differences in peak serum concentrations and beta-half-lives of elimination exist, however, and are reflected in up to ten-fold differences in values of the area under the curve of serum concentration versus time for administration of similar drug doses. As suggested by high apparent volumes of distribution and low binding to serum proteins, penetration into many body tissues and fluids is favorable. Considering new findings, orally administered ciprofloxacin has been found to be absorbed primarily in the duodenum and jejunum. Studies also suggest this drug to be cleared by transepithelial elimination into the bowel lumen as well as by the renal route. Oral bioavailability of quinolones has been demonstrated to be in general good in ill as well as healthy subjects but is reduced on co-administration with magnesium- and aluminum-containing acids, sucralfate (which contains aluminum), or ferrous sulfate. Pharmacodynamic parameters, such as the relationship of serum concentrations and drug potency in vitro to clinical response and suppression of bacterial resistance, have been little studied and merit further investigation.

Use of antimicrobial susceptibility testing for epidemiology and the selection of oral, parenteral and topical regimens for control of CAPD-associated Staphylococcus aureus infection

Staphylococcus aureus is an important cause of peritonitis in patients undergoing continuous ambulatory peritoneal dialysis (CAPD). Using standard broth microdilution and disk diffusion methodology, we evaluated the in vitro activity of selected antimicrobial agents against S. aureus strains isolated from CAPD patients to assess candidate regimens for 1) topical agent control of colonization, 2) oral chemotherapy of CAPD infectious complications, and 3) parenteral treatment of serious CAPD-associated staphylococcal infections. A total of 34 isolates (31 patients) of S. aureus were available for testing, including 29 isolates (29 patients) from pericatheter skin, four isolates (four patients) from the nares, and one isolate from an episode of peritonitis. Six of the isolates were oxacillin-resistant (ORSA). The antimicrobial agents tested by broth microdilution included 17 different quinolones, 10 cephalosporins, six glycopeptides, two aminoglycosides, and imipenem. A total of eight potential topical agents, including the antistaphylococcal agent mupirocin, were tested by disk diffusion. All of the quinolones, with the exception of nalidixic acid (MIC90 greater than 16 micrograms/ml), had excellent activity against both ORSA and oxacillin-susceptible S. aureus (OSSA) with the most active agent being WIN57273 (MIC90 less than or equal to 0.015 microgram/ml). Imipenem and the cephalosporins, with the exception of cefixime, ceftazidime, and E-1040, possessed good activity against OSSA. None of the beta-lactam agents tested were active against ORSA. Likewise, the aminoglycosides, amikacin and gentamicin, exhibited good activity against OSSA strains but no activity against ORSA strains. All glycopeptides tested demonstrated excellent activity against ORSA strains. Of the topical antimicrobial agents tested only bacitracin, mupirocin, and nitrofurantoin were active against all OSSA and ORSA strains tested.(ABSTRACT TRUNCATED AT 250 WORDS)

In vitro evaluation of WIN 57273, a new broad-spectrum fluoroquinolone

WIN 57273 is a new fluoroquinolone that has an expanded spectrum of activity against Staphylococcus spp. (MIC for 90% of isolates [MIC90], 0.008 microgram/ml), Enterococcus faecalis (MIC90, 0.06 microgram/ml), Bacillus spp. (MIC90, 0.03 micrograms/ml), Listeria monocytogenes (MIC90, 0.06 microgram/ml), Streptococcus spp. (MIC90, 0.03 microgram/ml), and Bacteroides fragilis group strains (MIC90, 0.5 microgram/ml). Like other fluoroquinolone compounds, WIN 57273 was active against members of the family Enterobacteriaceae (97% of strains inhibited by less than or equal to 2 micrograms/ml), Haemophilus, Branhamella, and Neisseria strains (100% susceptible), Acinetobacter spp. (100% susceptible), and Pseudomonas aeruginosa (68% susceptible). We observed that WIN 57273 was very active against cephalosporin- or aminoglycoside-resistant gram-negative strains but shared cross-resistance with other fluoroquinolones. Increasing inoculum concentrations had minimal effects on WIN 57273 MICs, and the drug was considered to be bactericidal based on reference MBC and kill curve analyses. Unlike most previously studied drugs in this class, WIN 57273 had increased activity (three- to fourfold) at low pH. Rates of mutation to WIN 57273 resistance at eight times its MIC were in the range of 5.6 x 10(-8) to greater than 1.4 x 10(-9). This new compound possesses a wide potential spectrum of use, and it should be evaluated further by in vitro and in vivo studies.

Lomefloxacin (SC-47111 or NY-198). Comparative antimicrobial activity against 2002 clinical isolates from hospitals in Mexico City

A new difluorinated quinolone, lomefloxacin, was shown to have potent in vitro activity against a broad spectrum of bacteria, including multiresistant strains isolated from patients with severe infections in three hospitals in Mexico City. Whereas its activity was comparable to that of another fluoroquinolone (enoxacin), the pharmacokinetic advantages offered by lomefloxacin may be a significant benefit in clinical use.

Statistical criteria for selecting quality control limits for broth microdilution susceptibility tests with 39 different antimicrobial agents. Collaborative Antimicrobial Susceptibility Testing Group

Multilaboratory studies have been carried out to establish quality control limits for broth microdilution susceptibility tests with 39 different antimicrobial agents and four different control strains. For each drug-microorganism combination, 100 MIC values were recorded (20 from each of five laboratories). An acceptable range of MICs was defined as values that included greater than 95% of those 100 MICs. In a series of consecutive tests, less than or equal to 5% of the MIC values might be expected to be one doubling dilution interval above or below the limits defined in that way: at least 95% of those MIC determinations should be within the narrow control limits. The 39 antimicrobial agents provided 111 drug-microorganism combinations for which usable quality control limits could be defined. The greater than 95% rule yielded a narrow range (including only two dilution steps) with 58 of the 111 control limits, and 53 control limits permitted a more traditional three-dilution step range of MICs.

Lomefloxacin, a new fluoroquinolone. Studies on in vitro antimicrobial spectrum, potency, and development of resistance

Lomefloxacin (NY-198; SC-47111), a potent new difluoroquinolone, was studied to compare its in vitro activity with that of other antimicrobials against 2194 clinical isolates. Lomefloxacin showed excellent inhibitory and bactericidal activity against strains of Enterobacteriaceae and inhibited greater than 99% of the isolates at a concentration of 4 micrograms/ml or less. Lomefloxacin exhibited good-to-moderate activity against strains of Acinetobacter (MIC90 4 micrograms/ml) and Pseudomonas aeruginosa (MIC90 8 micrograms/ml), but poor activity for Pseudomonas cepacia (MIC90 greater than 16 micrograms/ml). Staphylococcus aureus, and Staphylococcus epidermidis isolates, both oxacillin-susceptible and -resistant strains, were susceptible (MIC90 1 micrograms/ml) to lomefloxacin and the other fluoroquinolones. Strains of Haemophilus influenzae, (MIC90 less than or equal to 0.13 micrograms/ml) Neisseria gonorrhoeae (MIC90 less than or equal to 0.03 micrograms/ml), and Branhamella catarrhalis (MIC90 less than or equal to 0.03 micrograms/ml) were highly susceptible to lomefloxacin. Streptococcal isolates, especially viridans streptococci, were considerably less susceptible to the fluoroquinolones. Overall, lomefloxacin had comparable activity to norfloxacin, fleroxacin, and ofloxacin, and against many facultative anaerobes lomefloxacin was more active than imipenem, cefotaxime, ceftazidime, ticarcillin/clavulanic acid, aztreonam, trimethoprim/sulfamethoxazole and gentamicin. Development of resistance to lomefloxacin by spontaneous mutation was low and comparable to that of other fluoroquinolones. Growth in subinhibitory concentrations resulted in increased resistance to fluoroquinolones for selected test strains.