Quinolone antimicrobial agents: adverse effects and bacterial resistance

Pyrrolopyrimidine inhibitors of DNA gyrase B (GyrB) and topoisomerase IV (ParE). Part I: Structure guided discovery and optimization of dual targeting agents with potent, broad-spectrum enzymatic activity

The bacterial topoisomerases DNA gyrase (GyrB) and topoisomerase IV (ParE) are essential enzymes that control the topological state of DNA during replication. The high degree of conservation in the ATP-binding pockets of these enzymes make them appealing targets for broad-spectrum inhibitor development. A pyrrolopyrimidine scaffold was identified from a pharmacophore-based fragment screen with optimization potential. Structural characterization of inhibitor complexes conducted using selected GyrB/ParE orthologs aided in the identification of important steric, dynamic and compositional differences in the ATP-binding pockets of the targets, enabling the design of highly potent pyrrolopyrimidine inhibitors with broad enzymatic spectrum and dual targeting activity.

Safety of antibiotic drugs in food animals: comparison of findings from preapproval studies and postapproval experience in the United States with safety information in published literature

Antibiotics are among the most widely prescribed drugs and are generally considered safe for the target species. However, their use has been associated with various adverse toxic effects in target animals, such as allergic reactions, gastrointestinal signs, cardiovascular effects, hypoglycemia, hepatic/renal toxicity, thrombocytopenia, and anaphylaxis. This article provides a qualitative summary of the adverse events observed in target animals during the evaluation of antibiotics by the Food and Drug Administration during both preapproval and postapproval periods. As there is a marked scarcity of published data on safety of antibiotics in food animals, more research is needed in this area.

In vitro activity of fleroxacin against multiresistant gram-negative bacilli isolated from patients with nosocomial infections

In order to evaluate the in vitro activity of fleroxacin against nosocomial gram-negative organisms, 263 multiresistant gram-negative bacilli (203 Enterobacteriaceae and 60 non-fermenting gram-negative bacilli) were isolated from adult patients with nosocomial infections. The different patterns of resistance to eight different antimicrobial agents (ampicillin, carbenicillin, piperacillin, cephalothin, cefamandole, ceftazidime, gentamicin and amikacin) were determined by minimum inhibitory concentration (MIC), using the agar dilution method. The most prevalent multiresistant species isolated were Klebsiella pneumoniae (28.9%), Escherichia coli (24%) and Pseudomonas aeruginosa (12.2%). All these bacterial strains showed three to five resistance patterns to at least three different antibiotics. Resistance to ceftazidime was observed in at least one of the resistance patterns of isolated bacteria. The activity of fleroxacin against multiresistant enteric bacteria was excellent; these strains showed a susceptibility of 79-100%. The susceptibility of P. aeruginosa to antipseudomonal agents was low; however, the activity of fleroxacin against these strains was higher than 60% (MIC < or = 2 microg/ ml), broadly comparable with ciprofloxacin. The resistance to fluoroquinolones detected in this study was no cause for alarm (3%). Consequently, fleroxacin maintains a remarkable activity against Enterobacteriaceae and remains highly active against other gram-negative bacilli. Nevertheless, actions directed at preventing or limiting resistance will be crucial to maintain the viability of fluoroquinolones as important therapeutic agents.

Ciprofloxacin as antipseudomonal treatment in patients with cystic fibrosis

OBJECTIVE

The efficacy and safety of oral ciprofloxacin as a maintenance antipseudomonal therapy were evaluated in 44 patients with cystic fibrosis who had completed a 14-day regimen of intensive hospital therapy with intravenous ceftazidime and amikacin, supplemented by amikacin inhalation therapy.

METHODS

Twenty-one patients were randomly assigned to oral ciprofloxacin alone (Group I) and 23 received ciprofloxacin plus inhaled amikacin (Group II).

RESULTS

Negative sputum cultures were achieved in 34 patients (77%) at the end of intensive therapy (19 Group I and 15 Group II) and were sustained after 3 months of maintenance therapy in 5 of the 19 responders in Group I (26%) and in 8 of the 15 responders in Group II (53%). Resistance to ciprofloxacin was found in 7 of 31 (23%) sputum isolates at the end of ciprofloxacin therapy. During maintenance therapy, continued improvement in clinical symptoms was observed in 14 patients in both treatment groups; 6 in each group had further improvements whereas only 4 patients were clinical failures. There was no correlation between clinical outcome and either elimination of Pseudomonas aeruginosa from sputum culture or development of ciprofloxacin resistance. Both maintenance regimens were well-tolerated by this population of patients which included 28 children younger than 15 years of age. There were no severe or serious adverse events, no signs of quinolone-related arthropathy and no growth impairment.

CONCLUSION

Ciprofloxacin was efficacious, safe and well-tolerated as maintenance antipseudomonal therapy in cystic fibrosis patients. These results suggest further evaluation of ciprofloxacin as an oral maintenance therapy is warranted.

Use of fluoroquinolones as prophylactic agents in patients with neutropenia

BACKGROUND

The use of fluorinated quinolone antibiotics to selectively decontaminate the gastrointestinal tract is a reasonable alternative to prevent infection in neutropenic patients. The fluoroquinolones represent ideal antibiotics with which to achieve the principles of selective decontamination by allowing colonization of anaerobes to inhibit the adherence, colonization and proliferation of potentially pathogenic aerobic flora.

OBJECTIVE

This report describes the prophylactic use of fluoroquinolones in neutropenic patients.

RESULTS

The majority of studies of fluoroquinolone prophylaxis in neutropenic patients have shown a reduction in documented Gram-negative bacterial infections. However, Gram-positive infections, particularly those with viridans streptococci, present a major impediment to the use of single agent prophylaxis with a quinolone.

CONCLUSION

Prophylaxis with fluoroquinolones in neutropenic patients was found to be advantageous, but it must be balanced against the risk of Gram-positive infections and the potential for antibiotic resistance.

The effects of ciprofloxacin on human chondrocytes in cell culture

Ciprofloxacin is a highly potent antibacterial agent that is used extensively in bone and joint infections. Because of reports of potential chondro-toxicity in animals, the effects of this drug on cells derived from human cartilage were tested in liquid micromass and agarose gel cultures. An inhibition of cell proliferation as indicated by a decrease in [3H]-thymidine uptake and bromodeoxyuridine labeling at ciprofloxacin concentrations of 0.5 and 50 mg/l was found which corresponded to the therapeutic and toxic serum levels. There was no effect on proteoglycan synthesis as indicated by 35SO4 incorporation. Immunocytochemistry showed no changes in morphology or staining patterns for type-I procollagen, type-II collagen, keratan sulfate and unsulfated chondroitin. Because the amount of inhibition of DNA synthesis varied with different ciprofloxacin concentrations, this data suggests that this agent has a differential effect on newly differentiating cells and might be the basis for contraindication in pediatric patients.

A randomised, multinational study with sequential therapy comparing ciprofloxacin twice daily and ofloxacin once daily

In a multinational, open, randomised, controlled clinical study, 474 hospitalised patients with moderate or severe infections were treated with sequential regimens of ofloxacin or ciprofloxacin. Ofloxacin 400 mg once daily or ciprofloxacin 200 mg twice daily were given intravenously for at least 3 days followed by oral treatment with ofloxacin 400 mg once daily or ciprofloxacin 500 mg twice daily. Overall cure rates of 86.8% (85.7%) in the ofloxacin group and 89.6 (89.5%) in the ciprofloxacin group were achieved in the intention-to-treat analysis (per protocol analysis). The overall bacteriological response rate (ofloxacin 89.5%, ciprofloxacin 89.0%) was comparable to the clinical cure rate. Both drugs were well tolerated and adverse events were rarely observed. It is concluded that ofloxacin and ciprofloxacin can be used successfully in the treatment of hospitalised patients with aerobic gram-positive and gram-negative infections. Ofloxacin has the advantage of a once-daily regimen, compared to the twice-daily regimen with ciprofloxacin.

Multicenter in vitro comparative study of fluoroquinolones against 25,129 gram-positive and gram-negative clinical isolates

In vitro activities of fleroxacin, ciprofloxacin, ofloxacin, and lomefloxacin were evaluated against 25,129 fresh bacterial isolates from 51 US hospital or medical center laboratories, beginning in October of 1990. Susceptibility rates were > or = 85% against most species of Gram-negative bacteria. Notable exceptions were Pseudomonas, Acinetobacter, Xanthomonas, and Providencia. The study drugs displayed similar activity against most Gram-negative species. At least 90% of oxacillin-susceptible staphylococci were susceptible but, of oxacillin-resistant strains, only approximately 60% of Staphylococcus epidermidis and 25% of Staphylococcus aureus were susceptible to the quinolones tested. Staphylococcus saprophyticus strains were less susceptible to fleroxacin (42%) than to the other compounds (79%-97%). Ofloxacin and ciprofloxacin were more active against streptococci, and none of the compounds demonstrated appreciable activity against enterococci. Thus, the spectra of activity of fluoroquinolones illustrate that they remain effective agents for the treatment of many types of infections caused by Gram-negative pathogens.

Fluoroquinolones in paediatrics--1995

The fluoroquinolones are characterised by a broad spectrum of antibacterial activity that includes many Mycobacterium, Chlamydia, Legionella, and Mycoplasma species as well as many multiply-resistant bacterial strains, good oral bioavailability, extensive tissue penetration, low protein binding and long elimination half-lives. Numerous clinical trials have shown that these compounds are effective and well tolerated in the treatment of adult patients with various infections, including urinary tract, respiratory tract, skin and soft tissue, bone and joint, and gynaecological infections, sexually transmitted diseases, infectious diarrhoea, infections in immunocompromised patients, and in surgical prophylaxis. Thus, there is increasing pressure to use this class of drugs in paediatric patients. However, concerns regarding adverse effects, particularly cartilage toxicity, have restricted development of the fluoroquinolone compounds for use in this population. Potential indications include Pseudomonas infections (mainly exacerbations of cystic fibrosis), urinary tract, gastrointestinal and central nervous system infections, infections in immunocompromised patients, certain otorhinolaryngological infections and infections caused by multiply-resistant pathogens. To date, clinical experience gained with fluoroquinolones in paediatric infections, which has been mainly on a compassionate-use basis, indicates that well-designed formal studies should be conducted to fully assess the efficacy and tolerability of these agents in specific indications in children.

Multicenter in vitro comparative study of fluoroquinolones after four years of widespread clinical use

In vitro activities of ciprofloxacin, fleroxacin, lomefloxacin, ofloxacin, and seven other oral antimicrobials including amoxicillin-clavulanic acid (A/C), oxacillin, cefaclor, cefixime, cefuroxime, erythromycin, and trimethoprim-sulfamethoxazole (T/S) were evaluated against 1708 fresh bacterial isolates from four hospital laboratories approximately 4 years after the introduction of ciprofloxacin. T/S and ofloxacin had the lowest MIC90s and greatest percentage of susceptible strains overall, followed by the other three quinolones. Quinolones were the most active drugs tested against Gram-negative bacteria, with little variation in the activity among the four compounds against most species. Quinolone resistance was detected to some degree in the majority of Gram-negative species tested, with Pseudomonas, Acinetobacter, Xanthomonas, and Providencia demonstrating the highest percentage of resistant strains. Ofloxacin and ciprofloxacin were relatively more active against Gram-positive bacteria than were fleroxacin and lomefloxacin, but T/S and A/C had more susceptible strains than any of the quinolones. Oxacillin-resistant staphylococci, enterococci, and streptococci exhibited the least quinolone susceptibility. This study showed that while resistance is developing among several previously susceptible bacterial species, quinolones remain important alternatives for the oral treatment of many types of infections. Actions to prevent or limit resistance will be important to maintain the viability of the quinolones as therapeutic agents in both hospital and community environments.

Multiple-dose pharmacokinetics of sparfloxacin and its influence on fecal flora

In a randomized, double-blind, placebo-controlled, multiple-dose pharmacokinetic study, the safety and effect on intestinal flora of sparfloxacin (SPX) were determined in 12 healthy male volunteers (8 received SPX and 4 received a placebo). Following fasting and oral administration of 400 mg on day 1 and 200 mg on days 2 to 8, concentrations of the free drug in serum, urine, and feces were measured by high-performance liquid chromatography; serum and urine were also evaluated by a microbiological assay. All results, except those for renal excretion, exclude the glucuroconjugate metabolite. A mean peak concentration in serum (400-mg dose) of 0.56 +/- 0.13 mg/liter was measured 3.52 +/- 0.98 h after administration. Pharmacokinetic parameters (measured by high-performance liquid chromatography) were based on an open, one-compartment model and resulted in the following day 1 (calculated for the 200-mg dose), day 4 (recalculated for a single dose), and day 8 values (mean +/- standard deviation): area under the curve, 16.4 +/- 2.3 (day 1) and 18.3 +/- 5.1 (day 4) mg.h/liter; elimination half-life, 18.3 +/- 3.9 h; steady-state volume of distribution, 4.7 +/- 1.4 (day 1) and 4.3 +/- 1.2 (day 8) liters/kg; apparent total clearance, 201 +/- 31 (day 1) and 190 +/- 51 (day 4) ml/min; renal clearance, 19.1 +/- 5.8 (day 1) and 23.2 +/- 19.4 (day 4) ml/min. Recovery in urine on day 1 was 5.89% +/- 1.4% of the dose in 24 h for the parent compound and 18.4% +/- 6.8% for the SPX glucuronide.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

The quinolones. An overview of their pharmacology

The fluoroquinolones represent a relatively new class of antibiotics with outstanding therapeutic potential, attributable to their broad spectrum of antimicrobial activity and favourable tissue distribution. They are highly active against most Gram-negative pathogens, as well as Staphylococcus aureus and coagulase-negative staphylococci. In addition, the fluoroquinolones have useful pharmacokinetic properties: they are orally active, and their lipophilicity and low degree of plasma protein binding allow for excellent tissue penetration and concentrations, as reflected in their particularly large apparent volumes of distribution. Infections due to aerobic Gram-negative pathogens are considered those most susceptible to the quinolones. Disease indications in which these agents appear to offer the greatest therapeutic advantage over currently available alternatives include the following: complicated urinary tract infections (particularly those caused by Pseudomonas aeruginosa or resistant Gram-negative microorganisms); suspected bacterial gastroenteritis; eradication of Salmonella typhi from the faeces in known carriers; P. aeruginosa-associated respiratory exacerbation in patients with cystic fibrosis; and chronic Gram-negative bacterial osteomyelitis. Direct comparisons of the various quinolones are too limited to date to provide clear therapeutic options. Nevertheless, this class of compounds is likely to play a major role in providing effective oral therapy for conditions that have previously required prolonged parenteral treatment.

The effect of ofloxacin and ciprofloxacin on pentylenetetrazol-induced convulsions in mice

There have been several reports that convulsions, although rare, occur in patients who received fluoroquinolones. In this study, conducted for the evaluation of the convulsant action of fluoroquinolones, the effect of ofloxacin and ciprofloxacin on pentylenetetrazol-induced convulsions were investigated in mice. Mice were pretreated intraperitoneally (IP) with saline, ofloxacin (20 or 80 mg/kg) or ciprofloxacin (20 or 80 mg/kg) 30 minutes before subcutaneous (SC) administration of pentylenetetrazol (40 or 60 mg/kg). In another experiment, diazepam (5 mg/kg) was injected (IP) in mice alone or in combination with ofloxacin (80 mg/kg) 30 minutes before pentylenetetrazol (40 mg/kg) administration (SC). In each experiment mice were observed over the following hour for the incidence and onset of clonic convulsions. Results showed that both doses of ofloxacin increased the incidence of clonic convulsions induced by 40 mg/kg pentylenetetrazol. This effect, however was only significant in the higher dose and inhibited by diazepam. On the other hand, a similar proconvulsant effect by ciprofloxacin could not be demonstrated.

Accidental overdose of intravenous ofloxacin with benign outcome

A patient accidentally received approximately 3 g of ofloxacin intravenously. She experienced only moderately severe central nervous system symptoms, which resolved within 9 h. The peak serum ofloxacin level was 39.3 micrograms/ml, approximately seven times the usual peak level. Ofloxacin may possess a considerable safety margin in humans.

Use of quinolones in pediatrics

Compared to nalidixic acid, the new quinolones possess an enlarged antimicrobial spectrum, greatly enhanced bactericidal activity, and substantial pharmacokinetic advantages. Because their activity against streptococci is limited the quinolones presently available will never be included in routine regimens for children. Moreover, adequate pharmacokinetic studies are still lacking in pediatrics, and potential drug toxicity warrants further long-term monitoring. Nevertheless, various studies strongly suggest that there is no quinolone-induced cartilage toxicity in humans, and the results of published clinical trials with fluoroquinolones in pediatric patients show promising efficacy and safety. From a review of the available data it is concluded that use of the quinolones in children should be limited to specific infections which are usually caused by Pseudomonas aeruginosa, Staphylococcus aureus or Staphylococcus epidermidis, and are complicated by underlying pathologic or special conditions such as cystic fibrosis or urologic abnormality. In each case, careful monitoring to determine efficacy, potential adverse effects including drug-drug interaction and toxicity, and any emergence of bacterial resistance is mandatory.

Fluoroquinolones in the treatment of cystic fibrosis: a critical appraisal

While the appropriate usage of antibiotics in cystic fibrosis patients is still a matter of debate, the introduction of oral antipseudomonal antibiotics such as fluoroquinolones represents an eagerly awaited addition to the therapeutic armamentarium. Ciprofloxacin is the single agent most often studied and used in this population for treatment of pulmonary exacerbations. Altered pharmacokinetics of fluoroquinolones have been described in cystic fibrosis patients as for other drugs, and a higher dosage than usual is recommended. Open clinical trials have shown good efficacy of ciprofloxacin in acute infection. A few comparative trials have demonstrated that ciprofloxacin is as effective clinically as conventional intravenous agents. As with other agents, a lack of correlation between clinical improvement and bacteriologic evaluation has been observed. Ciprofloxacin (and possibly ofloxacin) are considered useful alternatives to parenteral agents in therapy of cystic fibrosis patients older than 18 years of age with exacerbations of pulmonary infection. Intermittent therapy with ciprofloxacin alternating with other conventional treatment appears to be a rational approach; clinical trials evaluating the alternation of fluoroquinolones with intravenous anti-pseudomonal therapy are necessary. Considering the potential for emergence of resistance and the not completely elucidated implication of increasing MICs during ciprofloxacin therapy, the duration of treatment should be limited to 2 to 4 weeks. In older children (12 to 18 years old), ciprofloxacin provides an alternative to intravenous agents when clinically justifiable. In view of the possibility of fluoroquinolone associated-arthropathy in younger children, ciprofloxacin should be used judiciously when no alternative agents are available or in life-threatening situations.

Ofloxacin versus trimethoprim-sulfamethoxazole for prevention of infection in patients with acute leukemia and granulocytopenia

In a prospective randomized study we evaluated the efficacy and safety of oral ofloxacin (dosage: 200 mg three times daily) versus trimethoprim-sulfamethoxazole (dosage: 960 mg three times daily) as antibacterial prophylaxis in 128 patients with acute leukemia who received aggressive cytotoxic chemotherapy and were granulocytopenic for a median duration of 30 days. Fewer patients receiving ofloxacin were colonized by Enterobacteriaceae (13% versus 90%, p less than 0.001) and Pseudomonas aeruginosa (3% versus 14%, p = 0.025), and developed gram-negative bacterial infection (4% versus 26%, p = 0.002), whereas the incidence of gram-positive bacterial (19% versus 22%) and fungal (7% versus 14%) infections was similar in both groups. Ofloxacin was significantly better tolerated than trimethoprim-sulfamethoxazole, and shortened the duration of fever (p = 0.02) and of parenteral antimicrobial therapy for presumed or documented acquired infection (p = 0.01). Ofloxacin appears to be a safe, effective, well-tolerated alternative to trimethoprim-sulfamethoxazole for preventing gram-negative infection in acute leukemia, but more effective prophylaxis of gram-positive infections is still needed.

[Comparison of the adverse effect profile of different substances such as penicillins, tetracyclines, sulfonamides and quinolones]

The penicillins, the tetracyclines and the sulfonamides have often been used in the last few decades in spite of their well-known side effects. Hypersensitivity reactions to penicillins are among the most important adverse reactions in these antibiotics; in every case a careful medical history has to be taken before a new course of penicillin treatment. The use of tetracyclines in women during the last six months of pregnancy or in children under the age of eight years is contraindicated. Patients with severe blood, kidney or liver disease should not be treated with sulfonamides. Toxic reactions to penicillin even with convulsions may occur in patients with renal insufficiency if the dosage is not adapted. The fluoroquinolones do not seem to have greater risks regarding adverse reactions than the historical compounds mentioned. Neurotoxicity is an important problem. Mild reactions are reported with incidences under 2%; severe neurotoxic side effects that require interruption of therapy are rare. Psychotic reactions, hallucinations, depressions and grand mal convulsions also belong to this category. Other side effects (skin, GI-tract) are no more frequent than with the classical antibiotics. In patients with renal insufficiency the dosage of ofloxacin has to be adapted. The cartilage lesions which are seen in juvenile rats and dogs raise the question whether or not the cases of arthralgia during therapy with older quinolones as well as under treatment with fluoroquinolones have a causal relationship. Up to date quinolones should not be prescribed in children and young adults except in cases with cystic fibrosis. The development of resistance has not been a significant problem so far.(ABSTRACT TRUNCATED AT 250 WORDS)