[Bacteriostatic and bactericidal activity, resistance and tolerance of 16 strains of thermophilic Campylobacter to 12 antibiotic drugs]. / Attività batteriostatica e battericida, resistenza e tolleranza di 16 ceppi di Campylobacter termofilo verso 12 chemio-antibiotici.

ABSTRACT

The majority of gastrointestinal infections due to "thermophilic" Campylobacter is self limiting and does not need antibiotic treatment. Anyhow there are some serious cases (sepsis, persistent and relapsing gastroenteritis, severe immunodeficient patients) which require appropriate therapy. The susceptibility of 15 strains of Campylobacter jejuni and of 1 strain of C. coli, isolated from patients with acute gastroenteritis, has been studied against 12 antibiotics with the broth microdilution method at two different inocula (10(3)-10(4) CFU/ml and 10(7)-10(8) CFU/ml), and with the standard agar disk diffusion test, modified to allow sensitivity testing of Campylobacter. For each antibiotic, the geometric mean of MIC and of MBC and the concentrations of the various drugs needed for inhibition and killing of 50 and 90% of the strains (MIC-MBC50 and MIC-MBC90 respectively) have been calculated. Finally the percentage of resistant strains and the percentage of tolerant strains (ratio MBC/MIC greater than or equal to 32) at low and high inoculum was determined. Erythromycin and aminoglycosides resulted the most active antibiotics against Campylobacter, being bactericidal as well as bacteriostatic at both low and high inoculum. Among the beta-lactams, cefotaxime was the most active, followed by piperacillin and ampicillin. Ceftazidime, aztreonam and rifampin were inactive. Ciprofloxacin, cotrimoxazole and tetracyclines showed some activity against Campylobacter at low inoculum. The agar disk diffusion method cannot be used for the "routinary" assay of susceptibility of Campylobacter, because it is a "naggy" microaerophilic organism.