A Preliminary Study on the Presence of Salmonella in Lymph Nodes of Sows at Processing Plants in the United States

Prevalence and antimicrobial susceptibility of Salmonella enteritidis and Salmonella typhimurium isolated from hen eggs and quail eggs in Karaj, Iran

BACKGROUND AND AIM

Different Salmonella serotypes are considered one of the most important food pathogens in the world. Poultry meat and eggs are the primary carriers of Salmonella in human populations. This study aimed to estimate the Salmonella enteritidis and Salmonella typhimurium contamination rates of retail hen and quail eggs in Karaj, Iran. Moreover, the antimicrobial resistance patterns of the strains were evaluated, and the efficiency of the standard culture method and multiplex polymerase chain reaction (m-PCR) were compared.

MATERIALS AND METHODS

In this descriptive cross-sectional study over 1 year (Jan-Dec 2022), 150 commercial and 150 backyard hen eggs and 300 commercial quail eggs, without cracks and fractures, were collected randomly from best selling groceries in Karaj city. All samples were examined for Salmonella contamination independently by standard culture and m-PCR approaches. A standard disc diffusion method was employed to assess the antimicrobial susceptibility of the strains against 18 antimicrobial agents.

RESULTS

Out of 300 examined eggs, 2 S. enteritidis strains were isolated from the shell of backyard hen eggs. The same serotype was also detected in the contents of one of these two eggs. One S. typhimurium was isolated from the shell of a commercial hen egg. Overall, the Salmonella contamination of the shell and contents was 1% and 0.3%, respectively. Salmonella was not isolated from the eggshells or the contents of the quail eggs. There was complete agreement between the results of m-PCR and the standard culture methods. Among the 18 tested antibiotics, the highest resistance was recorded for colistin (100%), followed by nalidixic acid (75%).

CONCLUSION

As most Salmonella spp. are associated with human food poisoning, continuous surveillance is required to effectively reduce the risk posed by contaminated poultry eggs. Furthermore, mandatory monitoring of antimicrobial use on Iranian poultry farms is recommended.

Salmonella assessment along the Spanish food chain: Likelihood of Salmonella occurrence in poultry and pig products is maintained across the food chain stages

Salmonellosis is one of the most important foodborne diseases worldwide, including the European Union. Despite the One Health approach measures for risk assessment and risk management implemented by the European Union, the occurrence of disease and disease outbreaks remains high (e.g. 694 outbreaks were reported in 2020), highlighting the need of new assessment methods. Herein we applied machine learning using the random forests method to evaluate and identify key points regarding the occurrence of Salmonella sp. along the Spanish food chain during 2015-2020, using data provided by the Spanish Agency for Food Safety and Nutrition. We compared the role of the three categorical variables [product (20 categories), region (18 categories) and stage (11 categories)]. Salmonella presence was influenced by the three explanatory variables considered: first by product, followed by region and stage. The most determinant product for Salmonella probability was 'meat', while the most important stage was 'slaughterhouse'. Specifically, the highest values were found in pig and poultry meats. In these products, the Salmonella probability was high at the early and final stages of the food chain, although not at intermediate stages. The presence of Salmonella in the final stages (retail) of the food chain is of concern, as it can cause human cases of salmonellosis, including outbreaks. This study demonstrates the utility of the random forest method to identify key points and evaluate the control efforts. We recommend improving the surveillance and control measures, especially in the product and stages pointed out by our analysis, and enhancing the data collection harmonization among the different autonomous communities.

Rapid Quantitative Method Development for Beef and Pork Lymph Nodes Using BAX® System Real Time Salmonella Assay

The goal of this study was to develop a rapid RT-PCR enumeration method for Salmonella in pork and beef lymph nodes (LNs) utilizing BAX^®-System-SalQuant^® as well as to assess the performance of the methodology in comparison with existing ones. For study one: PCR curve development, pork, and beef LNs (n = 64) were trimmed, sterilized, pulverized, spiked with 0.00 to 5.00 Log CFU/LN using Salmonella Typhimurium, and then homogenized with BAX-MP media. Samples were incubated at 42 °C and tested at several time points using the BAX^®-System-RT-PCR Assay for Salmonella. Cycle-Threshold values from the BAX^®-System, for each Salmonella concentration were recorded and utilized for statistical analysis. For study two: Method comparison; additional pork and beef LNs (n = 52) were spiked and enumerated by (1) 3M™EB-Petrifilm™ + XLD-replica plate, (2) BAX^®-System-SalQuant^®, and (3) MPN. Linear-fit equations for LNs were estimated with recovery times of 6 h and a limit of quantification (LOQ) of 10 CFU/LN. Slopes and intercepts for LNs using BAX^®-System-SalQuant^® when compared with MPN were not significantly different (p < 0.05), while the same parameters for 3M™EB-Petrifilm™ + XLD-replica plate were significantly different (p > 0.05). The results support the capability of BAX^®-System-SalQuant^® to enumerate Salmonella in pork and beef LNs. This development adds support to the use of PCR-based quantification methodologies for pathogen loads in meat products.

Prevalence and Antimicrobial Resistance of Nontyphoidal Salmonella enterica from Head Meat and Trim for Ground Product at Pork Processing Facilities

ABSTRACT

Pork head meat may harbor Salmonella and contaminate other carcass by-products during harvest and fabrication. A large pork processing plant in the United States was sampled bimonthly for 11 months to determine the concentration, prevalence, seasonality, serotype diversity, and antimicrobial susceptibility of Salmonella enterica isolated from cheek meat and head trim of swine carcasses. Each collection consisted of 25 samples on two consecutive days in the morning and afternoon shifts, for a total of 100 cheek meat and 100 head trim samples each month. Tissues were cultured for Salmonella by using restrictive media and enrichment techniques, and a subset of isolates was serotyped, analyzed for antimicrobial susceptibility, and genome sequenced. Salmonella postenrichment prevalence did not differ (P = 0.20) between cheek meat (63%) and head trim (66%). Postenrichment prevalence differed (P < 0.05) by month (January, 94%; March, 80%; May, 54%; July, 59%; September, 47%; and November, 55%) and by processing shift (morning, 68%; afternoon, 62%). The subset (n = 618) of isolates selected for serotyping yielded 21 distinct serotypes: Typhimurium (49%), Infantis (10%), Heidelberg (8%), I 4,[5],12:i:- (8%), and 17 other types (≤5%). In total, 407 multidrug-resistant (MDR; resistance to three or more antibiotic classes) isolates were identified. There were 120 isolates that exhibited the penta-resistant ACSSuT phenotype. In addition, 113 isolates exhibited decreased susceptibility to ciprofloxacin (MIC ≥ 0.12 μg/mL). Resistance genes blaCARB, blaSHV, blaTEM, aac(6')-Ib-cr,qnrB, sul2, and dfrA were expressed in numerous MDR Salmonella isolates. The data herein suggest that pork products from the head, compared with data reported for carcasses, may have a relatively high prevalence of Salmonella with diverse serotypes and MDR.

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