Quantification, Serovars, and Antibiotic Resistance of Salmonella Isolated from Retail Raw Chicken Meat in Vietnam

The objectives of this study were to quantify Salmonella counts on retail raw poultry meat in Vietnam and to phenotypically characterize (serovars and antibiotic resistance) the isolates. A total of 300 chicken carcasses were collected from two cities and two provinces in Vietnam. Salmonella counts on the samples were determined according to the most-probable-number (MPN) method of the U.S. Department of Agriculture, Food Safety and Inspection Service (USDA-FSIS). A total of 457 isolates were serotyped and tested for antibiotic susceptibility. Overall, 48.7% of chicken samples were Salmonella positive with a count of 2.0 log MPN per carcass. There were no significant differences (P > 0.05) in log MPN per carcass by the study variables (market type, storage condition, and chicken production system). There was a significant difference (P < 0.05) in Salmonella-positive prevalence by chicken production system. Among the 22 Salmonella serovars identified, Albany was the most frequent (34.1%), followed by Agona (15.5%) and Dabou (8.8%). Resistance to at least one antibiotic was common (i.e., 73.3%), with high resistance to tetracycline (59.1%) and ampicillin (41.6%). Resistance to three antibiotics was the most frequently found multidrug resistance profile (17.7%, n = 81); the profile that was resistant to the highest number of drugs was resistant to nine antibiotics (0.7%, n = 3). Only Salmonella Albany posed phenotypic resistance to ceftriaxone (a drug of choice to treat severe cases of salmonellosis). The data revealed that, whereas Salmonella prevalence on raw poultry was high (48.7%), counts were low, which suggests that the exposure risk to Salmonella is low. However, improper storage of raw chicken meat and cross-contamination may increase Salmonella cell counts and pose a greater risk for infection. These data may be helpful in developing risk assessment models and preventing the transmission of foodborne Salmonella from poultry to humans in Vietnam.