2000, Number 2
Vet Mex 2000; 31 (2)
Drug resistance and sensitivity in Pasteurella haemolytica, P. multocida and Haemophilus somnus isolated from dairy calves in Tijuana in the state of Baja California in Mexico
Pijoan AP, Aguilar RF
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ABSTRACTThe frequency of resistance or sensitivity in vitro to different antibiotics was studied in 34 strains of Pasteurella multocida, 31 of P. haemolytica and 11 of Haemophilus somnus, obtained from pneumonic lungs of dairy calves from Tijuana and Rosarito in the state of Baja California in Mexico from January 1996 to March 1997. Sensitivity or resistance of the isolates was determined by using the standard disk diffusion susceptibility test. Each strain was tested with 17 antimicrobial agents. A very high prevalence (› 90%) of resistance was found in Pasteurella spp when tested against kanamycin and lincomycin. In addition to the resistance showed to these antibiotics, P. haemolytica also presented a high prevalence (› 80%) of resistance to penicillin and streptomycin, and H. somnus to penicillin, streptomycin and ampicillin. Furthermore, over 20% of isolates were resistant to recently released antibiotics such as tilmicosin and fluorfenicol. In contrast, all strains studied were sensitive to cefotaxime, and over 87% of all strains analyzed were sensitive to mezlociline or cefalexime. These results show the need for local veterinarians and producers to be more responsible in the use of antibiotics in the treatment of pneumonia in calves, and the growing danger of the dissemination of strains of Pasteurella spp or H. somnus resistant to most antimicrobials which could complicate in the future the treatment of pneumonia in these animals.