Salmonella spp. are among the most common foodborne pathogens, and increase in the occurrence of antimicrobial drug-resistant Salmonella poses a severe risk to public health. The main objective of this study was to determine changes in Salmonella prevalence and their antimicrobial resistance on poultry farms following recommendations to changes in biosecurity practices. Four poultry farms were sampled by collecting cloacal swabs, drag swabs, and litter samples prior to recommended biosecurity changes (March-April) and post recommendations (October-November). Prevalence of Salmonella was 3 to 4% during pre-recommendations, while the prevalence was higher (P > 0.05), ranging from 5 to 14% during post recommendations. Higher Salmonella prevalence was observed for pre- and post-recommendation phases by sample type in cloacal and drag samples -5% for farm 1, drag swab -6% on farm 2, cloacal swab -6% for farm 3, and drag swab -17% on farm 4. The PCR confirmed Salmonella were serotyped and tested for antimicrobial resistance. Six serotypes of Salmonella were identified with S. Enteritidis (52%) being the most prevalent, followed by S. Berta (38%), S. Mbandaka (7%), S. Typhimurium (2%), S. Kentucky (0.4%), and S. Tennessee (0.4%). A total of 7% isolates exhibited resistance to at least one of the 8 antimicrobials. Higher resistance was observed for tetracycline, streptomycin, and nalidixic acid. A single isolate of S. Mbandaka exhibited multidrug resistance to tetracycline, amoxicillin/clavulanic acid, and ampicillin. Based on these prevalence results, it can be inferred that, irrespective of implementation of improved biosecurity practices, seasonal variation can cause changes in the prevalence of Salmonella on the farms. Resistance to clinically important antimicrobials used to treat salmonellosis is a concern to public health.
Salmonella is one of the top causes for bacterial foodborne infections in the United States, emphasizing the importance of controlling this pathogen for protecting public health. Poultry and poultry products are commonly associated with Salmonella, and interventions during production and processing are necessary to manage the risk of infection due to consumption of poultry products. In recent times, the demand for organic and antibiotic-free poultry has increased owing to consumer perceptions and concerns of increasing prevalence of antimicrobial-resistant (AMR) pathogens. However, the microbiological effect of these management practices is not clear. This study was conducted to determine the difference in the AMR of Salmonella isolated from poultry processed conventionally and organically. Fecal samples, carcass rinses, and environmental samples were collected over 1 year and analyzed for the prevalence of Salmonella and AMR. Results of this experiment showed that organic chickens were associated with statistically higher levels of Salmonella during early processing steps. However, no difference in Salmonella prevalence was observed between organic and conventional carcasses postchill. In addition, for most antimicrobial agents tested, prevalence of AMR Salmonella in conventional processing was lower in this study than was reported by the National Antimicrobial Resistance Monitoring System for chickens at slaughter. These observations indicate that organic methods may introduce greater risk of Salmonella contamination; however, proper interventions during processing can abate this risk. In addition, this study supports the assertion that raising chickens without the use of antibiotics may result in lower prevalence of AMR Salmonella. HIGHLIGHTS
Decimal reduction time ( D-value) was calculated for six non-O157 Shiga toxin-producing Escherichia coli (STEC) in a laboratory medium and ground beef. For the laboratory medium, an overnight culture of each strain of STEC was divided into 10-mL sample bags and heated in a water bath for a specific time on the basis of the temperatures. Survival curves were generated by plotting the surviving bacterial population against time, and a linear-log primary model was used to estimate the D-values from survival curves. The z-values (the temperature raised to reduce the D-value by one-tenth) were calculated by plotting the log D-values against temperature. Similarly, for ground beef, six fat contents, 5, 10, 15, 20, 25, and 30% of ground beef were formulated for this study. Inoculated meat was divided into 5-g pouches and submerged in a water bath set at specific temperatures (55, 60, 65, 68, and 71.1°C). The average D-value for these strains in a laboratory medium was 17.96 min at 55°C, which reduced significantly ( P < 0.05) to 1.58 min at 60°C, and then further reduced ( P < 0.05) to 0.46 min at 65°C. In ground beef, a negative correlation ( P < 0.05) between fat content of ground beef and D-values was observed at 55°C. However, at temperatures greater than 60°C, there was no impact ( P > 0.05) of fat content of ground beef on the thermal resistance of non-O157 STECs. Irrespective of the fat content of ground beef, the D-values ranged from 15.93 to 11.69, 1.15 to 1.12, and 0.14 to 0.09 min and 0.05 at 55, 60, 65, and 68°C, respectively. The data generated from this study can be helpful for the meat industry to develop predictive models for thermal inactivation of non-O157 STECs in ground beef with varying fat content.
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