SUSCEPTIBILITY OF ANIMAL ISOLATES OF PASTEURELLA MULTOCIDA TO OFLOXACIN AND COMMONLY USED ANTIMICROBIAL AGENTS

Abstract

The susceptibility of Pasteurella nzultocida isolates from animals (mainly from porcine pneumonic lung) to ofloxacin (OFLX) and 17 other commonly used antibacterial agents was determined. The results were as follows.(1) All of the 37 isolates were highly susceptible to OFLX (MIC: 0.025-0.1μg/ml), followed by trimethoprim (TMP), oxolinic acid (OXA), ampicillin (ABPC), chloramphenicol (CP), and thiamphenicol (TP)(MIC: 0.1-0.8μg/ml). The susceptibility ofthe isolates to a combination product of sulfamethoxazole (SMX)-TMP (20: 1), doxycycline (DOXY), oxytetracycline (OTC), and tiamulin (TML) was moderate (MIC: 0.8-6. 25μg/ml). The isolates showed relatively low susceptibility (MIC: 12.5-50μg/ml) to streptomycin (SM), kanamycin (KM), spectinomycin (SPCM) and tylosin (TS). SMX showed the lowest activity against the isolates (MIC: 25-200μg/ml).(2) A total of 13 (35.1%) isolates were resistant to SMX, SM, ABPC or DOXY OTC. Several different resistance patterns were found. Isolates resistant only to SMX were most frequent (8 isolates), followed by those resistant to the combination of SMX and SM, ABPC, or TC (5 isolates). Those resistant isolates were susceptible to OFLX as well as the other isolates.(3) The susceptibility of the 76 isolates to OFLX and the 4 other pyridonecarboxylic acid derivatives was determined. The highest distribution of MIC of OFLX, norfloxacin (NFLX), OXA, nalidixic acid (NA), or pipemidic acid (PPA) was observed at 0.05μg/ml, 0.1%mu;g/ml, 0.8μg/ml, or 1.56μg/ml, respectively.