Advancement of Dairying in Austria (ADDA): Mastitis in dairy cows – milk sample testing, antibiotic use and antimicrobial resistance

Abstract

The recommended antimicrobial agents for treatment or chemoprophylaxis of pertussis are erythromycin, azithromycin and clarithromycin.Trimethoprim-sulfamethoxasole (cotrimoxazole) can also be used. We tested the susceptibility to first-line and alternative antibiotics of 135 Bordetella pertussis (B. pertussis) strains recovered from patients with whooping cough through national pertussis surveillance in the Czech Republic (CR) in 1967 -2015. Isolates of B. pertussis were divided according to the year of isolation into 3 periods: from the years 1967 to 1999 (42 strains), 2004 -2010 (43 strains) and 2011 -2015 (50 strains).Methods & Materials: The minimal inhibitory concentrations (MICs) of erythromycin, clarithromycin, azithromycin, ciprofloxacin, and co-trimoxazole were tested by the reference agar dilution method on Bordet-Gengou agar with 15% defibrinated sheep blood.Results: Individual MICs of antibiotics were nearly identical in all three time periods. Each of the 135 study strains of B. pertussis was inhibited by two concentrations of erythromycin and azithromycin (0.06 and 0.12 mg/l) with the exception of one strain. All strains were inhibited by three concentrations of clarithromycin (0.03, 0.06, and 0.12 mg/l). All study strains were inhibited by a single concentration of ciprofloxacin (0.06 mg/l) and three concentrations of co-trimoxazole (0.12, 0.25 mg/l and 0.5 mg/l). Conclusion:The MICs of antibiotics were in the narow range of two to three low concetrations in all three time periods. The group of 135 Czech strains of B. pertussis appears to be homogeneous in terms of the MICs of the antibiotics tested, with two to three low concentrations being effective against all strains. To be inhibited, no strain required a higher concentration of erythromycin, clarithromycin, azithromycin, ciprofloxacin, or co-trimoxazole. No changes were observed in the MICs range of individual antibiotics during the period of 55 years.