The in-vitro activities of enoxacin and ofloxacin compared with that of ciprofloxacin

Availability of 0.3% ofloxacin ointment and solution in human conjunctiva and aqueous humor

Ofloxacin 0.3% ophthalmic solution or ointment was administered preoperatively to 13 patients undergoing cataract surgery. Mean drug concentrations in conjunctival biopsies were 2.62 and 6.55 micrograms/gm and in aqueous humor samples were 0.36 micrograms/mL and 0.43 micrograms/mL, for ointment and solution respectively. Mean conjunctival concentrations of ofloxacin achieved MIC90 values for 419 gram-positive and gram-negative organisms previously analyzed.

Topical ofloxacin compared with gentamicin in the treatment of external ocular infection. Ofloxacin Study Group

In a double-masked, randomised, controlled study the effectiveness and safety of 0.3% ofloxacin solution were compared with those of 0.3% gentamicin ophthalmic solution in treating external bacterial ocular infections. The clinical improvement rate for patients treated with ofloxacin was 98% (51/52) and 92% (48/52) for those treated with gentamicin. Microbiological improvement was achieved in 78% (40/51) of the ofloxacin patients, compared with 67% (35/52) of the gentamicin group. Ofloxacin treatment eradicated or controlled 85% (86/101) of the Gram positive and 89% (17/19) of the Gram negative organisms cultured, compared with 83% (103/124) and 78% (29/37), respectively, after gentamicin treatment. None of these differences were statistically significant. The incidence of adverse effects attributable to ofloxacin treatment (3.2%) was less than that reported for gentamicin (7.1%). Ofloxacin proved to be an effective, safe, and comfortable therapy for external bacterial ocular infection.

High-pressure liquid chromatography and microbiological assay of serum ofloxacin levels in adults receiving intravenous and oral therapy for skin infections

Thirty-two adults hospitalized with skin and skin structure infections received intravenous ofloxacin followed by oral ofloxacin. The standard treatment was 400 mg every 12 h. One patient with renal failure received 400 mg every 24 h. Serum ofloxacin levels were measured (1.5 h postdose and 1 h predose) during intravenous (32 patients) and oral (30 patients) therapy. Levels were assayed by high-pressure liquid chromatography (HPLC) and microbiological assay (MBA). Mean levels +/- standard deviation (in micrograms per milliliter) when measured by MBA after intravenous dosing were (postdose versus predose) 6.23 +/- 2.49 versus 2.42 +/- 1.56, and those after oral dosing were 6.17 +/- 3.25 versus 3.49 +/- 2.77. When measured by HPLC, mean levels +/- standard deviation after intravenous dosing were 5.81 +/- 2.08 versus 2.14 +/- 1.26 and those after oral dosing were 5.63 +/- 2.92 versus 3.41 +/- 2.98. There were no significant differences between levels achieved with oral or intravenous dosing when measured by either MBA or HPLC. Levels in serum did not correlate with side effects. The MICs for 50 and 90% of the 40 aerobic pathogens isolated from 21 patients were 0.5 and 2.0 micrograms/ml, respectively. Cure or improvement was achieved in 30 patients. Intravenous and oral administration of ofloxacin yielded similar levels in serum which were safe and effective in the therapy of skin infections in adult patients.

Susceptibility of anaerobic bacteria isolated from intra-abdominal infections to ofloxacin and interaction of ofloxacin with metronidazole

The in vitro activities of ofloxacin alone and in combination with metronidazole against 177 anaerobic bacteria isolated from intra-abdominal infections, as determined by broth microdilution, showed that some Bacteroides fragilis strains were susceptible and that most other B. fragilis group species strains were resistant to ofloxacin. Isolates of other anaerobic species and genera, including those causing female genital tract disease, were generally susceptible to ofloxacin. Ofloxacin in combination with metronidazole usually showed an additive or indifferent interaction but no antagonism.

Oral ofloxacin therapy of infections due to multiply-resistant bacteria

We determined the efficacy and safety of orally administered ofloxacin, 400 mg twice daily, in the treatment of infections due to multiply-resistant bacteria. Patients (n = 99) were treated for 84 infections in 82 patients evaluable for efficacy with a bacteriologic response of 71%. Organisms treated included Pseudomonas aeruginosa (39), Staphylococcus aureus (11), Serratia marcescens (9), Enterobacter species (7), five each of Escherichia coli, Citrobacter, Salmonella, Klebsiella, and other organisms. The overall clinical responses was 89%: 28 (90%) of 16 osteomyelitis, 10 (83%) of 12 urinary tract infections, and three of three bacteremias. Insomnia occurred in 27% and responded to dose reduction. Resistance of P. aeruginosa to ofloxacin developed in 15% of isolates. No hepatic, renal, or hematologic toxicity developed in spite of long therapy, 283 days. Ofloxacin was an effective therapy for lower respiratory, urinary, bone, and soft tissue infections due to multiply-resistant Gram-negative bacteria and is effective for selected Staphylococcus aureus infections.

Species identification and antibiotic susceptibility testing of enterococci isolated from hospitalized patients

A total of 236 enterococci from hospitalized patients were identified to the species level, and their susceptibilities to 11 antibiotics were determined. Overall, 195 (82.6%) and 38 (16.1%) isolates were identified as Enterococcus faecalis and E. faecium, respectively, but the species distribution as determined from blood culture isolates differed markedly. A total of 27 (63.2%) E. faecium isolates, but no E. faecalis strains, were ampicillin resistant (MIC, greater than 8 micrograms/ml). High-level gentamicin resistance (MIC, greater than 500 micrograms/ml) was found in 8.2% of E. faecalis isolates but was not seen in other species.

Pleural penetration of ciprofloxacin in patients with empyema thoracis

We evaluated the pharmacokinetics of a single 200-mg dose of ciprofloxacin, administered as a 30-minute infusion, into pleural exudate in five elderly patients with empyema thoracis. Ciprofloxacin was measured by HPLC and the pharmacokinetic parameters were determined by noncompartmental methods. Mean peak serum levels 30 minutes after administration were 1.98 +/- 0.07 mg/L. Terminal serum half-lives ranged from 3.9 to 5.1 h. Mean concentrations of ciprofloxacin in pleural exudate were 1.44 +/- 0.42 mg/L at a mean time of 4.5 +/- 2.5 h. After this time, the pleural exudate level exceeded the corresponding serum twofold to tenfold. The mean percentage penetration into the inflammatory compartment was approximately 210 percent. Our data suggested that ciprofloxacin penetrates well into the pleural fluid of patients with empyema thoracis. The concentrations achieved were well above the MIC90 of most pathogens normally found in patients with empyema thoracis for a period of approximately 12 h.

Comparative in-vitro activity of fourteen antibiotics against clinical isolates of enterococci

The in-vitro antibacterial activities of fourteen antimicrobial agents, including ampicillin, amikacin, Augmentin, ceftazidime, cefotaxime, ceftriaxone, ciprofloxacin, erythromycin, gentamicin, penicillin G, piperacillin, rifampicin, streptomycin and vancomycin, were compared against 195 enterococcal strains isolated from clinical specimens received at the King Abdulaziz University Hospital in Saudi Arabia. The antibacterial susceptibility was determined by the minimal inhibitory concentration (MIC) using an agar dilution method. Ampicillin, Augmentin and vancomycin exhibited the greatest activity, inhibiting 90% of the tested strains (MIC90) at 2 micrograms/ml, followed by penicillin G and piperacillin with MIC90 of 4 micrograms/ml. Erythromycin, third generation cephalosporins, aminoglycosides and rifampicin, on the other hand, had poor activity against enterococci with MIC90s well above the obtainable serum concentrations. The clinical implications of resistance to aminoglycosides and the alternative antimicrobial therapy in serious enterococcal infections are discussed in the text.

Oral ciprofloxacin for treatment of acute bacterial pharyngotonsillitis

The clinical efficacy and tolerability of ciprofloxacin orally administered at the dosage of 250 mg twice a day was evaluated in 25 patients affected by acute bacterial pharyngotonsillitis. All patients were non-responders to previous conventional antibiotic therapies due to in vitro resistance of the responsible bacteria, or possibly the low antibiotic concentration at the infection site. None of the patients had infections caused by group A beta-haemolyticus streptococcus. Treatment with ciprofloxacin lasted for 5-10 days (mean 6.7). A favorable clinical response was observed in 92% of patients (15 resolutions and 7 improvements) at the end of the therapy and two weeks later (follow-up). One patient was not evaluable because of the unfortunate onset of glossitis that caused the interruption of the treatment. No other side-effects were recorded in the other 24 patients. The bacteriological response was excellent: 83% bacteriological eradication, 13% persistence and super-infection in only one patient (4%). Ciprofloxacin administered orally at low dosages is highly effective in the treatment of bacterial pharyngotonsillitis and is also well tolerated.

Ofloxacin: a review

Ofloxacin is a new fluorinated quinolone antibiotic with a broad spectrum of activity against a variety of gram-positive and -negative bacteria including Enterobacteriaceae, Pseudomonas aeruginosa, and methicillin-resistant Staphylococcus aureus. In addition, ofloxacin has significant activity against Neisseria gonorrhoeae, Chlamydia trachomatis, and Mycobacterium tuberculosis and this may give rise to new indications for the class of quinolone antibiotics. Clinical trials to date have demonstrated the efficacy of ofloxacin in the treatment of lower respiratory tract infections, urinary tract infections, and sexually transmitted diseases. Adverse effects to ofloxacin are usually mild and include gastrointestinal, central nervous system, and hypersensitivity reactions. Significant drug interactions with ofloxacin have not been reported.

The comparative in vitro activity of ofloxacin and selected ophthalmic antimicrobial agents against ocular bacterial isolates

The in vitro activity of ofloxacin, a new fluoroquinolone anti-infective agent, was evaluated against 419 ocular bacterial isolates of 55 species to determine its potential as a topical agent for the treatment of ocular infections. Other agents tested in this study, in which a modified tube-dilution procedure was used, include norfloxacin, gentamicin, tobramycin, chloramphenicol, and polymyxin B. Ofloxacin demonstrated good to excellent activity against a variety of gram-positive and gram-negative pathogens. The minimum inhibitory concentration against 90% of all bacterial strains tested (MIC90) of ofloxacin was 0.5 microgram/ml for Staphylococcus aureus and S. epidermidis, 2 micrograms/ml for Streptococcus pneumoniae, and 4 micrograms/ml for Pseudomonas aeruginosa. These species were more susceptible to ofloxacin than to any of the nonquinolones tested. The MIC90 of ofloxacin was lower than that of norfloxacin, another quinolone, against S. aureus, S. epidermidis, and St. pneumoniae and equal to that of norfloxacin against P. aeruginosa. Because of its broad spectrum of activity and excellent in vitro activity, we concluded that ofloxacin has the potential for development into a superior topical treatment for ocular infection.

Fluoroquinolone antimicrobial agents

The fluoroquinolones, a new class of potent orally absorbed antimicrobial agents, are reviewed, considering structure, mechanisms of action and resistance, spectrum, variables affecting activity in vitro, pharmacokinetic properties, clinical efficacy, emergence of resistance, and tolerability. The primary bacterial target is the enzyme deoxyribonucleic acid gyrase. Bacterial resistance occurs by chromosomal mutations altering deoxyribonucleic acid gyrase and decreasing drug permeation. The drugs are bactericidal and potent in vitro against members of the family Enterobacteriaceae, Haemophilus spp., and Neisseria spp., have good activity against Pseudomonas aeruginosa and staphylococci, and (with several exceptions) are less potent against streptococci and have fair to poor activity against anaerobic species. Potency in vitro decreases in the presence of low pH, magnesium ions, or urine but is little affected by different media, increased inoculum, or serum. The effects of the drugs in combination with a beta-lactam or aminoglycoside are often additive, occasionally synergistic, and rarely antagonistic. The agents are orally absorbed, require at most twice-daily dosing, and achieve high concentrations in urine, feces, and kidney and good concentrations in lung, bone, prostate, and other tissues. The drugs are efficacious in treatment of a variety of bacterial infections, including uncomplicated and complicated urinary tract infections, bacterial gastroenteritis, and gonorrhea, and show promise for therapy of prostatitis, respiratory tract infections, osteomyelitis, and cutaneous infections, particularly when caused by aerobic gram-negative bacilli. Fluoroquinolones have also proved to be efficacious for prophylaxis against travelers' diarrhea and infection with gram-negative bacilli in neutropenic patients. The drugs are effective in eliminating carriage of Neisseria meningitidis. Patient tolerability appears acceptable, with gastrointestinal or central nervous system toxicities occurring most commonly, but only rarely necessitating discontinuance of therapy. In 17 of 18 prospective, randomized, double-blind comparisons with another agent or placebo, fluoroquinolones were tolerated as well as or better than the comparison regimen. Bacterial resistance has been uncommonly documented but occurs, most notably with P. aeruginosa and Staphylococcus aureus and occasionally other species for which the therapeutic ratio is less favorable. Fluoroquinolones offer an efficacious, well-tolerated, and cost-effective alternative to parenteral therapies of selected infections.

The effect of ofloxacin on experimental periodontitis in hamsters infected with Actinomyces viscosus ATCC 15987

Syrian hamsters were infected with Actinomyces viscosus ATCC 15987 by inoculation into the oral cavity to induce experimental periodontitis. The effect of an antibiotic, ofloxacin (OFLX), on the experimental periodontitis was examined. In Group A, OFLX gel was applied daily to the gingival mucosa, 2 weeks after bacterial inoculation. Groups B and C were an infected control and a noninfected control, respectively. The hamsters in these three groups were fed a powdered high-sucrose diet. The hamsters in Group D, also a noninfected group, were fed an ordinary solid diet. Salivary occult blood test, evaluation of gingival and plaque index, measurement of alveolar bone loss, bacterial examination, and histological observation were performed 11 weeks after infection. Group B exhibited significantly higher levels of gingival index, plaque index, and alveolar bone loss than the noninfected controls. Severe inflammation of the gingivae, formation of gingival pockets, migration of many inflammatory cells, and obvious bone loss were also observed in Group B. However, these inflammatory changes were milder in Group A, which was treated with OFLX.

Ofloxacin: in vitro activity against recently isolated gram-negative bacterial strains

The activity of ofloxacin was determined against 117 Enterobacteriaceae, 13 Acinetobacter var, anitratus, 124 Pseudomonas aeruginosa in comparison with other antibiotics. Its activity was very high: against Enterobacteriaceae the minimum inhibitory concentration (MIC)50 was 0.125 micrograms/ml, the MIC90 1 micrograms/ml, and the geometric mean (GM) was 0.4 micrograms/ml against Acinetobacter var. anitratus the MIC50 1 micrograms/ml, MIC90 4 micrograms/ml, GM 1.7 micrograms/ml. Unlike other authors we found that the activity of ofloxacin was influenced by the selection of P. aeruginosa resistant to carbenicillin and gentamicin.

In vitro activities of PD 117,596 and reference antibiotics against 448 clinical bacterial strains

The in vitro activity of PD 117,596, a new fluoroquinolone antibiotic, was tested against 448 bacterial isolates (15 genera) by agar dilution (inoculum, 10(4) CFU per spot). The activity of PD 117,596 was compared with that of 15 antibiotics against 327 gram-negative strains and with that of 8 other antibiotics against 121 gram-positive strains. PD 117,596 demonstrated the best activity against Klebsiella spp., Enterobacter spp., Acinetobacter spp., Serratia marcescens, and Branhamella catarrhalis (MICs for 90% of the isolates [MIC90S], 0.008 to 0.25 microgram/ml). PD 117,596 (MIC90, 0.25 microgram/ml) was at least twofold more active than ciprofloxacin against Pseudomonas aeruginosa and Pseudomonas spp. PD 117,596 and ciprofloxacin were similar in activity against Escherichia coli, Proteus mirabilis, Haemophilus influenzae, H. parainfluenzae, Neisseria gonorrhoeae, Legionella pneumophila, and Campylobacter jejuni (MIC90, 0.002 to 0.125 microgram/ml). PD 117,596 was more active than ciprofloxacin against streptococcal groups A, B, C, and G, S. pneumoniae, and enterococci (MIC90S, 0.06 to 0.125 microgram/ml). Against Staphylococcus aureus, including methicillin-resistant isolates, PD 117,596 (MIC90S, 0.03 to 0.06 microgram/ml) was 4- to 16-fold more active than ciprofloxacin and was most active against Corynebacterium spp. PD 117,596 appears to be the most active fluoroquinolone to date, with excellent activity against gram-positive bacteria and enhanced activity against gram-negative aerobic-facultative bacteria.

Ofloxacin: its pharmacology, pharmacokinetics, and potential for clinical application

Ofloxacin is a 4-quinolone antibiotic with rapid bactericidal activity against a wide variety of organisms. Its proposed mechanism of activity is interference with DNA gyrase, an enzyme essential for the replication of bacterial DNA. In vitro activity of ofloxacin includes a variety of aerobic and anaerobic bacteria. Enteric gram-negative bacilli and cocci are generally sensitive to ofloxacin; nonaeruginosa strains of Pseudomonas are less so. Numerous bacterial pathogens of the gastrointestinal tract are also sensitive to the drug. Although its MIC values for gram-positive aerobic organisms are generally higher, ofloxacin's bactericidal activity against these organisms is considered by some to be adequate, and superior to that of most other fluoroquinolones. Ofloxacin is well absorbed after oral administration. Wide tissue and body fluid distribution is demonstrated. Urinary excretion is thought to be the primary route of elimination, with 80% of the dose recovered in the urine within 24 hours. The serum half-life ranges between 2.9 and 9 hours in a dose-dependent manner. Only modest accumulation is reported after multiple-dose administration. Clinical trials using daily dosages of 100-800 mg/day in single or divided doses have been reported in the treatment of a variety of conditions such as skin and soft tissue infections, tonsillitis, sexually transmitted disease, respiratory tract infections, cystitis, and complicated and uncomplicated urinary tract infections. English reports of these trials, however, are generally limited to abstract form, making evaluation of trial design difficult. Side effects most frequently encountered include gastrointestinal and central nervous system reactions.

Pharmacokinetics of ofloxacin after parenteral and oral administration

In 10 volunteers, the pharmacokinetics of ofloxacin [HOE 280, DL 8280; (+/-)-9-fluoro-2,3-dihydro-3-methyl-10-(4-methyl-1-piperazinyl)-7-oxo-7H -pyrido-[1,2,3-de] [1,4]benzoxacine-6-carboxylic acid] was determined after administration of 25, 50, 100, and 200 mg intravenously (30-min infusion) as well as 200 and 400 mg orally. Concentrations in serum and urine were measured by high-pressure liquid chromatography. Concentrations in serum following different parenteral ofloxacin dosages demonstrated dose dependency with long biological half-lives of 231 to 267 min. Pharmacokinetic parameters were calculated on the basis of open two- and three-compartment models, which yielded nearly identical results. High volumes of distribution (1.2 to 1.4 liters/kg of body weight) suggested effective diffusion into the extravascular space. High total and renal clearances indicated primarily renal excretion with additional elimination pathways, such as tubular secretion and extrarenal elimination. After oral administration, absorption was excellent, and the absolute bioavailability following 200 mg of ofloxacin could be calculated at greater than 0.95. Maximal concentrations in serum were attained 1.2 to 1.9 h after dosing; areas under the curve increased in proportion to dose between 200 and 400 mg of oral ofloxacin. The amount of known metabolites (demethyl and N-oxide compounds) excreted in urine reached only 4.3% (intravenously) and 4.0% (orally). Transient headaches in some volunteers were the only side effects registered.

Identification of Streptococcus faecalis and Streptococcus faecium and susceptibility studies with newly developed antimicrobial agents

Identification and susceptibility studies were performed on 301 blood and urine Streptococcus faecalis and Streptococcus faecium isolates. Strep Trio-Tubes S4, S5, and S3 (Carr-Scarborough Microbiologicals, Inc.) were compared with conventional methods for accuracy and rapidity. Of 282 isolates identified as S. faecalis, 98% were identified by species in 4 h with Trio-Tubes; the same percentage of isolates analyzed by conventional methods were identified in 24 h. All 14 S. faecium isolates (approximately 5% of the total number of isolates) were identified by Trio-Tubes in 24 h. In vitro MIC susceptibility testing of the isolates was performed by the Dynatech 2000 microdilution technique (Dynatech Laboratories, Inc.). Several newly developed antimicrobial agents, including imipenem (a carbapenem) and some of the quinolone drugs, i.e., CI-934, ciprofloxacin, A-56619, A-56620, amifloxacin, norfloxacin, and enoxacin, were tested, as were ampicillin, erythromycin, and vancomycin. Both ampicillin and vancomycin showed good activity against S. faecalis, with MICs for 90% of isolates tested (MIC90S) of 1 and 2 micrograms/ml, respectively; with S. faecium, ampicillin exhibited an MIC90 of 16 micrograms/ml and vancomycin exhibited an MIC90 of 2 micrograms/ml. Of the newer antimicrobial agents, imipenem and CI-934 exhibited the greatest activity against S. faecalis strains, with MIC90S of 2 and 0.5 micrograms/ml, respectively. MBCs against the isolates were determined with CI-934, with 90% of S. faecalis strains showing MBCs of 1 microgram/ml or less.

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

Ofloxacin is one of a new generation of fluorinated quinolones structurally related to nalidixic acid. It is an orally administered broad spectrum antibacterial drug active against most Gram-negative bacteria, many Gram-positive bacteria and some anaerobes. Ciprofloxacin is the only other quinolone with superior in vitro antibacterial activity. However, the pharmacokinetic profile of ofloxacin is superior to that of ciprofloxacin, with more rapid absorption and a peak serum concentration several times higher. Moreover, ofloxacin achieves high concentrations in most tissues and body fluids. The results of clinical trials with ofloxacin have confirmed the potential for use in a wide range of infections, which was indicated by its in vitro antibacterial and pharmacokinetic profiles. It has proven effective against a high percentage of infections caused by Gram-negative organisms, slightly less effective against Gram-positive infections, and effective against some anaerobic infections. Clinical efficacy has also been confirmed in a variety of systemic infections as well as in acute and chronic urinary tract infections, and ofloxacin has generally appeared to be at least as effective as alternative orally administered antibacterial drugs. Ofloxacin is well tolerated and, although experience with the drug in clinical practice to date is limited, bacterial resistance does not appear to develop readily. Thus, ofloxacin is an orally active drug which offers a valuable alternative to other broad spectrum antibacterial drugs.

Review of the 4-quinolones

Improvements in antimicrobial activity and pharmacokinetics have moved the 4-quinolones into the forefront of antibiotic research. The 4-quinolones are analogues of nalidixic acid, and there are presently at least six agents in this group under investigation in the United States. It is difficult to generalize their clinical usefulness, since these agents exhibit different pharmacokinetic profiles, antimicrobial activity (with varied minimum inhibitory concentrations among similar organisms), and dosage regimens. The 4-quinolones are potential therapeutic alternatives for infections caused by a variety of organisms. They include: Neisseria gonorrhoeae; Pseudomonas aeruginosa; Haemophilus influenzae; Staphylococcus aureus; common enteric pathogens (salmonella, shigella, campylobacter, etc); and intracellular bacteria (legionella, chlamydia, mycobacteria, etc). Clinical efficacy has been demonstrated in urinary tract infections, respiratory tract infections, and sexually transmitted diseases. Future studies will undoubtedly demonstrate effectiveness in numerous additional infectious processes. The purpose of this article is to compare the 4-quinolones in regards to pharmacokinetics and spectrum of activity and review the clinical studies involving these agents.

In vitro and in vivo activity of ciprofloxacin against enterococci isolated from patients with infective endocarditis

In vitro activity of ciprofloxacin against 27 strains of enterococci was inoculum dependent. Using inocula of 10(5) to 10(6) or 10(7) to 10(8) CFU of enterococci per ml, the MICs for 50 and 90% of strains tested increased from 1 to greater than or equal to 128 micrograms of ciprofloxacin per ml with the higher inoculum compared with the lower inoculum. The MBC for 50% of strains tested increased from 2 to greater than 128 micrograms/ml and the MBC for 90% of strains tested increased from 8 to greater than 128 micrograms of ciprofloxacin per ml with the lower and higher inocula, respectively. The combination of penicillin-gentamicin was more effective in vitro than the combination of ciprofloxacin-gentamicin against the low or high inoculum of enterococci. Using two strains of enterococci, we studied the efficacy of ciprofloxacin in the treatment of enterococcal experimental endocarditis in rabbits. Ciprofloxacin used alone or combined with gentamicin was significantly less effective (P less than 0.01) than procaine penicillin alone or procaine penicillin combined with gentamicin for the treatment of enterococcal experimental endocarditis. The combination of ciprofloxacin-procaine penicillin was not a more effective therapy than procaine penicillin alone.

Serum bactericidal activity of ciprofloxacin and ofloxacin in volunteers

The serum bactericidal activity of two newer quinolones, ciprofloxacin and ofloxacin, against 206 clinical bacterial isolates was determined in six male volunteers after oral administration of either 500 mg of ciprofloxacin or 200 mg of ofloxacin respectively. The highest bactericidal titers were achieved against Enterobacteriaceae 1 h after ciprofloxacin administration, ranging from 1:121 for indole-positive Proteus species to 1:30 for Serratia spp. Ofloxacin generated lower titers, ranging from 1:14 for indole-positive Proteus spp. to 1:2.5 for Enterobacter spp. Only low serum bactericidal titers were found for Pseudomonas aeruginosa, Acinetobacter spp. and gram-positive cocci. It is concluded that the activity of orally administered ciprofloxacin is superior to that of orally administered ofloxacin in the serum bactericidal test.

Penetration of ofloxacin into bronchial secretions

The penetration of ofloxacin into bronchial secretions was evaluated in 16 patients after administration of a single oral dose of ofloxacin 400mg. Bronchial secretions were aspirated at bronchoscopy after 1 to 6 hours and serum was collected simultaneously. Ofloxacin concentrations were measured by a microbiological assay method. Considerable individual variations in serum and bronchial aspirate concentrations were recorded: bronchial aspirate concentrations varied between 1.1 mg/L and 4.5 mg/L but exceeded 1.5 mg/L in 14 of 16 patients between 1 and 6 hours. The ratio between simultaneous mean bronchial aspirate and serum concentrations ranged between 0.53 in the second hour and 0.92 in the fourth hour. It is likely that inhibitory activity will be sustained over at least 6 hours against most potential respiratory pathogens including Haemophilus influenzae, Branhamella catarrhalis, Gram-negative bacilli, Staphylococcus aureus, Legionella pneumophila and Mycoplasma pneumoniae. Streptococcus pneumoniae and Pseudomonas aeruginosa may have minimal inhibitory concentration (MIC) values lower than ofloxacin concentrations achieved in bronchial secretions, although some isolates are less sensitive. Clinical studies should establish the relevance of pharmacokinetic data to respiratory infections caused by organisms of borderline susceptibility.

In vitro susceptibility of Acinetobacter species to various antimicrobial agents

The in vitro activity of 18 antimicrobial agents against 40 clinical isolates each of Acinetobacter calcoaceticus subsp. anitratum and Acinetobacter lwoffi was studied. Most of the newer 4-quinolone derivatives were extremely active against these organisms. Newer beta-lactam agents, such as cefpirome, BMY 28142, and BRL 36650, were also extremely active, inhibiting all strains at clinically achievable levels. Most agents were two- to fourfold more active against A. lwoffi.

In vitro activity of difloxacin hydrochloride (A-56619), A-56620, and cefixime (CL 284,635; FK 027) against selected genital pathogens

Management of sexually transmitted diseases is facilitated by having antimicrobial agents with activity against all of the major genital pathogens. Newer quinolones show promise of being active against Neisseria gonorrhoeae and Chlamydia trachomatis. Two quinolones, difloxacin (A-56619) and A-56620, and an oral cephalosporin, cefixime (CL 284,635; FK 027), were evaluated in vitro. All three were highly active against 400 isolates of N. gonorrhoeae, including penicillinase-producing N. gonorrhoeae, N. gonorrhoeae with chromosomally mediated resistance, and isolates with penicillin MICs of less than 1 microgram/ml. Susceptibilities to one antimicrobial agent were usually strongly correlated with susceptibilities to the other antimicrobial agents evaluated, but isolates with increasing resistance to beta-lactams were least likely to show increasing resistance to quinolones. Difloxacin and, to a lesser extent, A-56620 were active against all 10 strains of C. trachomatis, and both had moderate activity against over 200 strains of Gardnerella vaginalis. Based on in vitro activity, difloxacin and A-56620 merit in vivo assessment for management of both C. trachomatis and N. gonorrhoeae infections, and cefixime shows considerable promise for treatment of N. gonorrhoeae infections.

In vitro studies of S-25930 and S-25932, two new 4-quinolones

The in vitro activity of S-25930 and S-25932 was compared with that of ciprofloxacin, norfloxacin and nalidixic acid against 740 clinical isolates. The data indicate that S-25930 was more active against Enterobacteriaceae than S-25932 and the latter was more active against gram-positive species. A study of clinical isolates resistant to chemically non-related classes of antibiotics revealed no cross-resistance. Nalidixic acid resistant Enterobacteriaceae showed an eight-fold decrease in susceptibility to the new agents. The killing kinetics of both compounds were good, S-25932 having an optimal bactericidal effect at a concentration of 0.5 mg/l. The data suggests that both agents are effective broad spectrum antibiotics.

In vitro susceptibility of aerobic gram-negative blood culture isolates to oxolinic acid, norfloxacin, ciprofloxacin, enoxacin, pefloxacin, ofloxacin and oxo-enoxacin

100 gram-negative strains isolated from blood cultures were selected for the evaluation of the in vitro activity of oxolinic acid, norfloxacin, ciprofloxacin, enoxacin, pefloxacin, ofloxacin and oxo-enoxacin. Ciprofloxacin showed the highest intrinsic activity. Oxo-enoxacin, the major metabolite of enoxacin, was 10-15-fold less active than enoxacin. Against Enterobacteriaceae and Vibrionaceae, all fluorinated quinolones except norfloxacin were equally effective, while against non-fermenters, ciprofloxacin and ofloxacin demonstrated greater activity than the others. Resistance to oxolinic acid had a detrimental effect on susceptibility to the new fluorinated quinolones.

In vitro activity of CI-934, a new quinolone, compared with that of other quinolones and other antimicrobial agents

The in vitro activity of CI-934, a new 4-quinolone, was determined against gram-positive and gram-negative bacteria. The MICs for 90% of the isolates tested were 0.25 microgram/ml for Streptococcus pneumoniae, 0.5 microgram/ml for Streptococcus faecalis, 0.25 microgram/ml for staphylococci, including methicillin-resistant strains, and less than or equal to 1.0 microgram/ml for Escherichia coli, Salmonella and Shigella spp., Klebsiella spp., Proteus spp., and Citrobacter spp. CI-934 had activity superior to that of other quinolones against streptococci by four- to eightfold. Against members of the family Enterobacteriaceae, ciprofloxacin was 2- to 18-fold more active; ofloxacin and norfloxacin were twofold more active or similar to CI-934. CI-934 inhibited ampicillin-cephalothin-resistant urinary isolates of E. coli, Klebsiella pneumoniae, and Proteus mirabilis and cefoxatime-resistant Acinetobacter spp., Citrobacter freundii, Enterobacter cloacae, Proteus vulgaris, and Morganella morganii. The medium, inoculum size, and oxygen concentration, as well as the addition of serum, had not major effect on the activity of CI-934. Magnesium at a concentration of 9 mM increased MICs and MBCs four- to eightfold, and testing at pH 6 increased MICs as much as 32- to 64-fold for some organisms in comparison with MICs at pH 7. The frequency of spontaneous mutation to resistance was comparable to that for other new quinolones, but resistant isolates could be selected by repeated subculture.

Comparative evaluation of ciprofloxacin, enoxacin, and ofloxacin in experimental Pseudomonas aeruginosa pneumonia

The therapeutic activity of ciprofloxacin, enoxacin, and ofloxacin was evaluated in guinea pigs with acute and chronic experimental Pseudomonas aeruginosa pneumonia. Intratracheal instillations of P. aeruginosa resulted in fatal pneumonia in all untreated animals within 36 h. Among treatment groups (80 mg/kg [body weight] per day), cumulative survival rates were: 47%, ciprofloxacin; 55%, enoxacin; and 42%, ofloxacin. These rates were not significantly different. Intrapulmonary killing of P. aeruginosa was equivalent 3 h after a single dose of ciprofloxacin or ofloxacin (20 mg/kg) or enoxacin (40 mg/kg). The combination of ciprofloxacin with azlocillin, ceftazidime, or tobramycin did not increase the efficacy of intrapulmonary killing of P. aeruginosa over that of ciprofloxacin alone. A chronic, nonfatal bronchopneumonia was induced in guinea pigs by intratracheal instillation of microscopic agar beads impregnated with a mucoid strain of P. aeruginosa. Compared with no treatment, ciprofloxacin and enoxacin produced greater than or equal to 99.9% intrapulmonary killing, and ofloxacin sterilized the lungs completely, after 4 days of treatment. In no quinolone-treated animal did resistant strains of P. aeruginosa emerge during 4-day treatment periods. In further studies with the chronic model, oral and parenteral ciprofloxacin treatment were found to be equivalent in efficacy. We conclude that several quinolone derivatives may be effective for the treatment of P. aeruginosa pneumonia and that combinations of quinolones with beta-lactams or aminoglycosides may not increase efficacy against P. aeruginosa pneumonia.