Ceftiofur is a third generation cephalosporin, an antimicrobial
that is structurally related to penicillin, which has a -lactam
ring that obstructs bacterial cell wall formation and has been
approved for use in feed animals in the United States. The blacmy
gene is responsible for encoding the enzyme cephalomycinasecodes,
which reduces susceptibility to first, second and third generation
cephalosporins. Organisms that possess the blacmy genes
not only had resistance to antimicrobials commonly used on the
farm, like ceftiofur, but also showed a resistance within the penicillin
class of antimicrobials commonly used to treat people
(Bogaerts et al., 2011; Johnson et al., 2010). Mohamed et al. (2014)
isolated 309 Salmonella Typhimurium and S. Kentucky strains from
chicken carcasses during pre- and post-chill tank poultry processing
and tested these isolates for resistance to ceftiofur. Of those 309
isolates, 145 isolates were positive for blacmy genes. Theoretically, if
an individual were to become infected with a bacterial isolate that
harbored the blacmy gene, treatments with penicillin and/or ceftiofur
class of antimicrobials with -lactam rings could prove
to be less effective.