Tigecycline: a single antibiotic for polymicrobial infections.
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Biomedical subjects
Publications and source records attributed to George A Pankey.
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New antimicrobial agents are urgently needed for clinical use due to the increasing prevalence and spread of multidrug-resistant bacteria that are commonly responsible for serious and life-threatening diseases. The need to develop new agents that effectively overcome existing mechanisms of resistance displayed by bacteria resistant to currently available drugs has become paramount. Tigecycline, the first in a new class of antimicrobials, the glycylcyclines, is an analogue of minocycline with additional properties that negate most mechanisms mediating resistance to the tetracyclines. In vitro testing has revealed that tigecycline has activity against vancomycin-resistant enterococci, methicillin-resistant Staphylococcus aureus, penicillin-resistant Streptococcus pneumoniae and many species of multidrug-resistant Gram-negative bacteria, although resistance to tigecycline by Pseudomonas aeruginosa and reduced susceptibility among Proteus species do occur. Tigecycline is being evaluated in multicentre Phase III clinical trials for therapy of many serious and life-threatening infections in which multidrug-resistant bacterial organisms may be found. Tigecycline appears to hold promise as a novel expanded spectrum antibiotic.
Multidrug-resistant Pseudomonas aeruginosa with combined decreased susceptibility to ceftazidime, ciprofloxacin, imipenem, and piperacillin is increasingly being found as a cause of nosocomial infections. It is important to look for combinations of drugs that might be synergistic. Ciprofloxacin resistance by P. aeruginosa is mediated in part by an efflux pump mechanism. Gatifloxacin, an 8-methoxyfluoroquinolone, inhibits a staphylococcal efflux pump. An earlier in vitro study using an Etest synergy method and time-kill assay suggested synergy of ciprofloxacin and gatifloxacin against P. aeruginosa. Synergy testing was performed by Etest and time-kill assay for 31 clinically unique, plasmid DNA distinct, U.S. P. aeruginosa isolates. Etest MICs for ciprofloxacin were 4 to >32 microg/ml, and for gatifloxacin they were >32 microg/ml. Ciprofloxacin plus gatifloxacin showed synergy by the Etest method for 6 (19%) of the 31 P. aeruginosa isolates using a summation fractional inhibitory concentration of < or = 0.5 for synergy. Synergy was demonstrated for 13/31 (42%) of isolates by time-kill assay. No antagonism was detected. The remaining isolates were indifferent to the combination. The Etest method and time-kill assay were 65% (20/31) concordant. The mechanism of the in vitro synergy may include P. aeruginosa ciprofloxacin efflux pump inhibition by gatifloxacin.
BACKGROUND: Although a considerable amount of research has gone into the study of the role of bactericidal versus bacteriostatic antimicrobial agents in the treatment of different infectious diseases, there is no accepted standard of practice. METHODS: A panel of infectious diseases specialists reviewed the available literature to try to define specific recommendations for clinical practice. RESULTS: In infections of the central nervous system, the rapidity with which the organism is killed may be an important determinant, because of the serious damage that may occur during these clinical situations. The failure of bacteriostatic antibiotics to adequately treat endocarditis is well documented, both in human studies and in animal models. CONCLUSION: The bulk of the evidence supports the concept that, in treating endocarditis and meningitis, it is important to use antibacterial agents with in vitro bactericidal activity. This conclusion is based on both human and animal data. The data to support bactericidal drugs' superiority to bacteriostatic drugs do not exist for most other clinical situations, and animal models do not support this concept in some situations. Clinicians should be aware that drugs that are bacteriostatic for one organism may in fact be bactericidal for another organism or another strain of the same organism.
OBJECTIVE: We sought to evaluate gatifloxacin in adults with acute uncomplicated bacterial rhinosinusitis. STUDY DESIGN: TeqCES was an open-label, multicenter, noncomparative study of the safety and efficacy of gatifloxacin. More than 11,000 adult patients with acute uncomplicated rhinosinusitis received gatifloxacin 400 mg once daily for 10 days. RESULTS: Moraxella catarrhalis (91% beta-lactamase producers), Haemophilus influenzae (28% beta-lactamase producers), Streptococcus pneumoniae (18% intermediately resistant and 14% fully resistant to penicillin), and Staphylococcus aureus were the predominant pathogens isolated from purulent nasal discharge. More than 99% of rhinosinusitis pathogens isolated from the nasopharynx of patients meeting the clinical criteria for rhinosinusitis were susceptible to gatifloxacin. Among 10,353 patients whose clinical response could be determined, 91.6% were cured. Clinical cure rates exceeded 90% for the major pathogens. Gatifloxacin was well tolerated; drug-related adverse events that occurred in 1% or more of patients were nausea (4.4%), dizziness (1.8%), diarrhea (1.4%), and headache (1.0%). CONCLUSION: Gatifloxacin is effective for patients with acute bacterial rhinosinusitis in the community.