Recombinant Salmonella typhi OMP

The lesser mealworms (Alphitobius diaperinus) constitute a common cosmopolitan pest in poultry flocks and may colonize the litter in adult and larval forms. Previous studies have documented their potential as carriers of enteric pathogens. In this context,S. entericaconstitutes a prioritized zoonotic agent in the poultry industry due to the sanitary risks and economic losses associated with its presence. The aim of this study is to describe the presence ofS. entericastrains in larval and adult forms ofA. diaperinuscollected from poultry litter belonging to industrial farms located in the central zone of Chile. A total of 403 specimens (203 adults and 200 larvae) were sampled from three farms and 25 flocks. For bacteriological isolation, beetles were processed to differentiate external and internal contamination. Then, isolates were serotyped according to the Kauffman-White scheme and antimicrobial resistance phenotypes were determined using the disk diffusion method. Gene sequences from the megaplasmid pESI were identified through a PCR based test. These procedures led to the detection of 15S. entericaisolates, belonging to serotypes Infantis (14) and Livingstone (1), from both adults (6) and larval (9) specimens, with a similar external (7) and internal (8) distribution. Furthermore, allS. Infantis isolates showed antimicrobial resistance and evidence of megaplasmid pESI carriage, with all possessing multidrug-resistant phenotypes. Our results confirm thatA. diaperinusconstitutes a potential reservoir of zoonoticSalmonellastrains of sanitary and economic concern for the industry and for public health.

Dairy products have been implicated in foodborne infections caused by different bacterial pathogens. Among them, Listeria monocytogenes is of particular concern due to its ubiquity, resistance to sanitation processes and high mortality rates resulting from infection. These issues make the development of novel methods for the rapid detection of this bacterium of high interest. The evaluation of a novel multiplex real-time Recombinase Polymerase Amplification method including an internal amplification control is reported in the present work. The method performance was compared to that of the European reference method (ISO 11290-1) for the detection of the species in samples from 40 commercial products, including 14 UHT milk samples, 16 hard cheese samples, 6 infant dairy preparation samples and 4 fresh cheese samples. A limit of detection below 10 cfu/25 g or mL sample was achieved, and values higher than 90% were obtained for relative sensitivity, specificity, accuracy, positive and negative predictive values and the index (kappa) of concordance. Analysis was achieved within one working day, compared to the six days required using the ISO method. Moreover, slight modification of the ISO 11290-1 method to include secondary enrichment in half Fraser broth resulted in the confirmation of all positive samples.