RESUMO
Fusidic acid is an antibiotic active against staphylococci and other bacterial pathogens. It is used in the treatment of staphylococcal infections usually in combination with other antibacterial agents. Reports of the clinical effects of antimicrobial combinations containing fusidic acid have been somewhat inconsistent. The aim of this study was to investigate the in vitro antagonism of fusidic acid and quinolones. Twenty-six staphylococci strains isolated from various clinical samples were tested. After detecting the diameter of the zone of inhibition around fusidic acid, levofloxacin, ciprofloxacin, ofloxacin and moxifloxacin for each strain, in vitro antagonism between fusidic acid and each quinolone was investigated using disk approximation. In all 26 strains, quinolones and fusidic acid were antagonist in vitro. The reason for this antagonistic effect and its clinical implications are not known. However, care should be exercised in prescribing quinolones and fusidic acid in combination.
Assuntos
Antibacterianos/administração & dosagem , Antibacterianos/antagonistas & inibidores , Anti-Infecciosos/administração & dosagem , Compostos Aza , Fluoroquinolonas , Ácido Fusídico/administração & dosagem , Ácido Fusídico/antagonistas & inibidores , Quinolinas , Staphylococcus/efeitos dos fármacos , Ciprofloxacina/administração & dosagem , Humanos , Técnicas In Vitro , Levofloxacino , Testes de Sensibilidade Microbiana , Moxifloxacina , Ofloxacino/administração & dosagem , Infecções Estafilocócicas/tratamento farmacológico , Infecções Estafilocócicas/microbiologia , Staphylococcus/isolamento & purificaçãoAssuntos
Ácido Fusídico/antagonistas & inibidores , Inibidores da Protease de HIV/farmacologia , Fígado/efeitos dos fármacos , Ritonavir/farmacologia , Saquinavir/farmacologia , Adulto , Interações Medicamentosas , Quimioterapia Combinada , Ácido Fusídico/metabolismo , Infecções por HIV/tratamento farmacológico , Humanos , Icterícia/induzido quimicamente , Fígado/metabolismo , Testes de Função Hepática , MasculinoRESUMO
A routine laboratory disk susceptibility testing of a resistant Staphylococcus aureus strain showed that around the ciprofloxacin disk, placed by chance in proximity to a fusidic acid disk, the inhibition zone was truncated. Follow-up of this observation by a planned disk approximation method showed that there is a real antagonism between these two antibacterial agents. The antagonism was observed while testing S. aureus isolates including the standard ATCC 25923 strain, with Bacillus subtilis ATCC 6633 spores and also with a mutant Escherichia coli made fusidic acid susceptible. The antagonistic property was found structure-specific, only associated with those fluoroquinolones containing the cyclopropyl substituent at the N1-position: ciprofloxacin, enrofloxacin, sparfloxacin and WIN 57273. Fluoroquinolones without this substituent such as enoxacin, norfloxacin, pefloxacin and ofloxacin were not antagonized by fusidic acid, the steroidal Gram-positive active antibiotic.
Assuntos
Ciprofloxacina/antagonistas & inibidores , Ácido Fusídico/antagonistas & inibidores , Anti-Infecciosos/farmacologia , Ciprofloxacina/farmacologia , Antagonismo de Drogas , Ácido Fusídico/farmacologia , Testes de Sensibilidade Microbiana , Relação Estrutura-AtividadeRESUMO
Four of 22 specimens of human pus inactivated up to 90% of added penicillin within one hour in vitro. Ampicillin and cephaloridine were also inactivated, but streptomycin and fusidic acid were not. The effect was not related to the protein content of the pus, nor to its pH value. Microbes that may produce beta-lactamase in small quantities were isolated from three of the four specimens, but the enzyme was not detected in the pus by physical methods nor by microbiological inhibition assay. The inactivating effect was shown to be a property of the solid portion of the pus, and was absent from the filtrate. We suggest that the effect may be an intrinsic property of the host, which should be investigated further as it has important implications for clinical practice.