Synergy and antagonism of fluoroquinolones with other classes of antimicrobial agents

In an attempt to overcome some of the gaps in their antibacterial spectrum, e.g. some Gram-positive bacteria (notably streptococci and Streptococcus pneumoniae) and anaerobes, the fluoroquinolones have been combined with other bactericidal and bacteriostatic agents. In general, the fluoroquinolones rarely show either synergy or antagonism when used in combination with other antimicrobial agents against most bacteria. Therefore, in infections where the fluoroquinolones do not provide cover against all potential organisms, combined treatment with an appropriate agent may be considered. Current data suggest that the fluoroquinolones are not antagonistic with beta-lactams, macrolides, clindamycin and the imidazoles. Aminoglycosides in combination with the fluoroquinolones do not show synergy. Antipseudomonal penicillins, ceftazidime or imipenem in combination with the fluoroquinolones are synergistic and may be useful for treating infections in immunocompromised patients. Rifampicin in combination with a fluoroquinolone for the treatment of staphylococcal endocarditis or osteomyelitis may be useful, although in vitro and in vivo results do not always coincide.