Abstract
The aim of this study was to determine the antimicrobial resistance patterns of
Salmonella
strains isolated from slaughter-age pigs and environmental samples collected at modern swine raising facilities
in Brazil. Seventeen isolates of six serotypes of
Salmonella enterica
subsp.
enterica
were isolated out of 1,026 collected samples:
Salmonella
Typhimurium (1),
Salmonella
Agona
(5),
Salmonella
Sandiego (5),
Salmonella
Rissen (1),
Salmonella
Senftenberg (4), and
Salmonella
Javiana (1). Resistance patterns were determined to extended-spectrum penicillin
(ampicillin), broad-spectrum cephalosporins (cefotaxime and ceftriaxone), aminoglycosides (streptomycin, neomycin, gentamicin, amikacin, and tobramycin), narrow-spectrum quinolone (nalidixic acid), broad-spectrum
quinolone (ciprofloxacin and norfloxacin), tetracycline, trimethoprim, and chloramphenicol. Antimicrobial resistance patterns varied among serotypes, but isolates from a single serotype consistently showed
the same resistance profile. All isolates were resistant to tetracycline, streptomycin, and nalidixic acid. One isolate,
Salmonella
Rissen, was also resistant to cefotaxime and tobramycin. All serotypes
were susceptible to ceftriaxone, norfloxacin, ciprofloxacin, ampicillin, gentamicin, and chloramphenicol. The high resistance to tetracycline and streptomycin may be linked to their common use as therapeutic
drugs on the tested farms. No relation was seen between nalidixic acid and fluoroquinolone resistance.