There is a paucity of information regarding antimicrobial agents that are suitable to treat severe infections caused by multidrug-resistant Campylobacter spp. Our aim was to identify agents that are potentially effective against multiresistant Campylobacter strains. The in vitro activities of 20 antimicrobial agents against 238 Campylobacter strains were analyzed by determining MICs by the agar plate dilution method or the Etest. These strains were selected from 1,808 Campylobacter isolates collected from Finnish patients between 2003 and 2005 and screened for macrolide susceptibility by using the disk diffusion test. The 238 strains consisted of 183 strains with erythromycin inhibition zone diameters of <23 mm and 55 strains with inhibition zone diameters of >23 mm. Of the 238 Campylobacter strains, 19 were resistant to erythromycin by MIC determinations (MIC > 16 g/ml). Given that the resistant strains were identified among the collection of 1,808 isolates, the frequency of erythromycin resistance was 1.1%. All erythromycin-resistant strains were multidrug resistant, with 18 (94.7%) of them being resistant to ciprofloxacin (MIC > 4 g/ml). The percentages of resistance to tetracycline and amoxicillin-clavulanic acid (coamoxiclav) were 73.7% and 31.6%, respectively. All macrolide-resistant strains were susceptible to imipenem, meropenem, and tigecycline. Ten (52.6%) multiresistant strains were identified as being Campylobacter jejuni strains, and 9 (47.4%) were identified as being C. coli strains. These data demonstrate that the incidence of macrolide resistance was low but that the macrolide-resistant Campylobacter strains were uniformly multidrug resistant. In addition to the carbapenems, tigecycline was also highly effective against these multidrug-resistant Campylobacter strains in vitro. Its efficacy for the treatment of human campylobacteriosis should be evaluated in clinical trials.Campylobacteriosis is usually a mild and self-limiting disease requiring no antimicrobial treatment (3, 5). Only rarely is it associated with extraintestinal manifestations, e.g., septicemia, skin and soft tissue infection, infective endocarditis, or meningitis (3). These infections usually require treatment with intravenous antimicrobial agents (3). Infections of immunocompromised patients and pregnant women as well as very young and very old patients or those with persisting symptoms (Ͼ1 week) also require antimicrobial treatment (3). Guillain-Barré syndrome and reactive arthritis are major postinfectious complications of campylobacteriosis (3,24,26).For many years, macrolides and fluoroquinolones have been the first-and second-choice alternatives for the antimicrobial treatment of campylobacter enteritis. Since the late 1980s, however, the emergence of resistance to these antimicrobial groups has complicated the treatment of this disease (1). For example, in Thailand, the rate of resistance to the fluoroquinolones has been up to 80% (8, 14). In Finland, the rate of fluoroquinolone resistance increased between 1995 and 2000 f...