RO 23-9424, a new cephalosporin 3'-quinolone: in-vitro antimicrobial activity and tentative disc diffusion interpretive criteria

Zidovudine-β-Lactam Pronucleoside Strategy for Selective Delivery into Gram-Negative Bacteria Triggered by β-Lactamases

Addressing antibacterial resistance is a major concern of the modern world. The development of new approaches to meet this deadly threat is a critical priority. In this article, we investigate a new approach to negate bacterial resistance: exploit the β-lactam bond cleavage by β-lactamases to selectively trigger antibacterial prodrugs into the bacterial periplasm. Indeed, multidrug-resistant Gram-negative pathogens commonly produce several β-lactamases that are able to inactivate β-lactam antibiotics, our most reliable and widely used therapeutic option. The chemical structure of these prodrugs is based on a monobactam promoiety, covalently attached to the active antibacterial substance, zidovudine (AZT). We describe the synthesis of 10 prodrug analogues (5a-h) in four to nine steps and their biological activity. Selective enzymatic activation by a panel of β-lactamases is demonstrated, and subsequent structure-activity relationships are discussed. The best compounds are further evaluated for their activity on both laboratory strains and clinical isolates, preliminary stability, and toxicity.

4-Quinolone derivatives and their activities against Gram positive pathogens

Gram-positive bacteria are responsible for a broad range of infectious diseases, and the emergency and wide spread of drug-resistant Gram-positive pathogens including MRSA and MRSE has caused great concern throughout the world. 4-Quinolones which are exemplified by fluoroquinolones are mainstays of chemotherapy against various bacterial infections including Gram-positive pathogen infections, and their value and role in the treatment of bacterial infections continues to expand. However, the resistance of Gram-positive organisms to 4-quinolones develops rapidly and spreads widely, making them more and more ineffective. To overcome the resistance and reduce the toxicity, numerous of 4-quinolone derivatives were synthesized and screened for their in vitro and in vivo activities against Gram-positive pathogens, and some of them exhibited excellent potency. This review aims to outlines the recent advances made towards the discovery of 4-quinolone-based derivatives as anti-Gram-positive pathogens agents and the critical aspects of design as well as the structure-activity relationship of these derivatives. The enriched SAR paves the way to the further rational development of 4-quinolones with a unique mechanism of action different from that of the currently used drugs to overcome the resistance, well-tolerated and low toxic profiles.

Multi-targeting by monotherapeutic antibacterials

Antibacterial discovery research has been driven, medically, commercially and intellectually, by the need for new therapeutics that are not subject to the resistance mechanisms that have evolved to combat previous generations of antibacterial agents. This need has often been equated with the identification and exploitation of novel targets. But efforts towards discovery and development of inhibitors of novel targets have proved frustrating. It might be that the 'good old targets' are qualitatively different from the crop of all possible novel targets. What has been learned from existing targets that can be applied to the quest for new antibacterials?

Comparison of amoxicillin with alternative agents for the treatment of acute otitis media in children

Expert panels have recommended high-dose amoxicillin (80-90 mg/kg/day) as the therapy of choice for uncomplicated acute otitis media in children. This recommendation is based primarily on pharmacokinetic data predicting bacteriologic cure of most middle ear infections by using amoxicillin at the recommended dosage. However, comparisons of aminopenicillin-containing regimens with alternative treatments, particularly azithromycin, have not consistently demonstrated superiority of the former, even in recent trials with stringent designs. Moreover, amoxicillin exposure may perturb nasopharyngeal colonization more profoundly than do alternative agents. These perturbations may theoretically promote the dissemination of beta-lactam-resistant pneumococci in the community more than other drugs approved for use in otitis media. Such findings suggest that several factors should be considered when choosing an agent to treat otitis media and that reexamination of high-dose amoxicillin as the superior first-line agent for this condition might be warranted.

Dual beta-lactam-fluoroquinolone compounds: a novel approach to antibacterial treatment

Codrugs comprise a beta-lactam-fluoroquinolone antibacterial hybrid. These new agents have been developed with the aim of enhancing the antibacterial spectrum of current therapies, overcoming intrinsic and acquired resistance, and diminishing severe side-effects. A few compounds, including Ro 23-9424, have entered Phase I clinical trials. Furthermore, a series of oral codrugs have been synthesised, although clear oral bioavailability has not yet been demonstrated. New drugs are urgently needed to treat Gram-positive resistant bacteria.

A multicenter, open label trial of azithromycin for the treatment of children with acute otitis media

OBJECTIVE

In this multicenter, open label trial the investigators evaluated the efficacy and safety of azithromycin suspension administered once daily for 5 days for the treatment of clinically and bacteriologically established acute otitis media.

METHODS

Two hundred eligible children with acute otitis media from 10 US centers were treated with 10 mg/kg of azithromycin oral suspension on Day 1, followed by 5 mg/kg once daily for the next 4 days. Tympanocentesis and subsequent culture of middle ear effusion were performed at baseline. Clinical efficacy was evaluated on Days 6, 11 and 30.

RESULTS

Analysis of clinical efficacy in evaluable patients 11 days after the initiation of therapy showed that the rate of satisfactory responses (cured or improved) ranged from 79.6 to 82.4% in patients infected with Streptococcus pneumoniae, Haemophilus influenzae, or Moraxella catarrhalis. Satisfactory clinical response at Day 30 was reported in 70% of evaluable patients, and eradication of S. pneumoniae, H. influenzae and M. catarrhalis was presumed in 64 to 73%. Relapses occurred in 14% of the evaluable patients. Among the treated patients 8.5% reported mild or moderate side effects.

CONCLUSION

Azithromycin is an effective, safe and well-tolerated treatment for children with acute otitis media.

A multicenter, double blind comparison of azithromycin and amoxicillin/ clavulanate for the treatment of acute otitis media in children

OBJECTIVE

To compare the efficacy and safety of azithromycin and amoxicillin/clavulanate in pediatric acute otitis media.

METHODS

Investigators from 12 US centers recruited 677 children. In a randomized, double blind, double dummy fashion, participants received either azithromycin suspension (n = 341) once daily for 5 days or amoxicillin/clavulanate suspension (n = 336) in three divided doses daily for 10 days.

RESULTS

Among evaluable patients satisfactory clinical response rates (cured and improved) measured 11 days after therapy began were 87.5% in the azithromycin group and 87.9% in the amoxicillin/clavulanate group; corresponding rates at 30 days were 73.5% in the azithromycin and 71.2% in the amoxicillin/clavulanate groups. Relapse rates were comparable for the treatment groups. Treatment-related side effects, primarily gastrointestinal, were reported significantly less frequently with azithromycin (8.8%) than with amoxicillin/clavulanate (30.8%) (P < 0.0001). Two (0.6%) azithromycin patients and 12 (3.6%) amoxicillin/ clavulanate patients discontinued therapy because of treatment-related side effects (P < 0.006 between groups).

CONCLUSIONS

In these children with acute otitis media, azithromycin given once daily for 5 days and amoxicillin/clavulanate given three times daily for 10 days had similar efficacy; however, azithromycin was significantly better tolerated.

A multicenter, randomized, open label comparison of azithromycin and amoxicillin/clavulanate in acute otitis media among children attending day care or school

OBJECTIVE

This multicenter, randomized, open label study compared the efficacy and safety of azithromycin and amoxicillin/clavulanate for the treatment of acute otitis media among children who were attending a day-care facility or school.

METHODS

Eligible children with acute otitis media from 21 US centers were randomized to treatment with 10 mg/kg of azithromycin oral suspension on Day 1, followed by 5 mg/kg once daily for the next 4 days or approximately 40 mg/kg/day of amoxicillin/clavulanate suspension in 3 divided doses for 10 days. Clinical efficacy was evaluated on Days 14, 30 and 45. Acceptance and convenience of the medications were assessed on Day 14 by parent interviews with a standardized questionnaire.

RESULTS

Of the 263 children enrolled in the study, 233 were evaluable at the primary evaluation 45 days after the start of treatment. Satisfactory clinical response rates (cure, delayed cure and improvement) were 60.5% in patients treated with azithromycin and 64.9% in patients treated with amoxicillin/clavulanate. Satisfactory clinical response rates at secondary evaluations were also comparable: 92.2% vs. 90.0% at Day 14 and 66.7% vs. 72.7% at Day 30 in patients treated with azithromycin and amoxicillin/clavulanate, respectively. No significant differences in treatment failures, relapses or recurrences were noted with either medication. Azithromycin was significantly better tolerated and caused fewer treatment-related adverse events (7.2%) than amoxicillin/clavulanate (17.1%) (P < 0.001). In response to the interview and questionnaire, parents of children treated with azithromycin noted less need for special arrangements to give medication (2.0% vs. 14.9%). Children liked the taste of azithromycin (89.2%) and did not have to be forced to take the medication (2.4%). Parents of children receiving amoxicillin/clavulanate noted that 61.8% liked the medication and 19.4% of children had to be forced to take it.

CONCLUSIONS

This study demonstrates that azithromycin was comparable to amoxicillin/clavulanate in achieving satisfactory clinical response rates in children with acute otitis media attending day care or school. Azithromycin was significantly better tolerated than amoxicillin/ clavulanate. Parents considered azithromycin to be significantly more convenient to administer and more acceptable to children.