PREVALENCE OF SALMONELLA IN RAW MEAT USED IN DIETS OF RACING GREYHOUNDS

One hundred twelve samples of commercial raw meat used in greyhound diets were collected and cultured for Salmonella using standard procedures. Fifty (44.64%) of these samples were positive for Salmonella. Salmonella typhimurium was the most frequently isolated serovar (48%), followed by S. newport (12.76%), S. agona (8.5 1%), and S. muenster (6.38%). The remaining 10 serovars recovered in this study represented 27.59% of the total Salmonella isolates. In addition, the meat samples were screened for Salmonella using a commercial DNA probe. Of the 106 samples tested, 70 (66.03%) were positive for Salmonella, which indicated that the DNA probe assay was more sensitive than the culture method for screening of Salmonella in raw meat. Antimicrobial susceptibility testing revealed that most of the Salmonella isolates were sensitive to a variety of antimicrobials, particularly amikacin and apramycin, and resistant to some others, such as clindamycin, erythromycin, penicillin, and sulfadimethoxine. The cumulative percentages of susceptibility (MIC50 and MIC90) of the Salmonella isolates were also determined. Most isolates were susceptible (MIC90) to low concentrations of gentamicin (2.0 mug/ml), imipenem (less-than-or-equal-to 0.25 mug/ml), and ciprofloxacin (less-than-or-equal-to 5 mug/ml). Marked resistance was found with the other antimicrobial agents. However, the high MIC values found for these isolates would not be achievable in vivo with the normal recommended doses of antimicrobial agents, so their use would not be beneficial. Numerous plasmid patterns were found in 17 randomly selected Salmonella isolates. Eight of the 17 isolates had 2-7 plasmids ranging from 2.4 to 15 kilobases in size. Eight isolates also exhibited large plasmids in the range of 50-60 and 95-105 kilobases. Large plasmids migrated above the chromosal DNA. Six isolates did not demonstrate any visible plasmids.