Salmonella enterica 13,23:i:- in a UK Broiler Hatchery: A Longitudinal Case Study of the Distribution of Resident Contamination and Its Control

Hatcheries potentially can disseminate Salmonella through poultry production chains. This study describes the investigation and control of persistent Salmonella enterica serovar 13,23:i:- in a UK broiler hatchery. Over four years from 2015 to 2019, a broiler hatchery was sampled intensively seven times, yielding Salmonella from 361 of 2645 samples. The findings assisted biosecurity advice and the targeting both of cleaning and disinfection (C&D) and subsequent sampling rounds. Additional sampling was conducted to assess C&D and monitor antimicrobial resistance, and also among all the supplying breeder flocks. The large majority of the isolates were Salmonella 13,23:i:- and the degree of contamination increased along the process pathway. The egg areas and the setter incubators were the least contaminated, whilst the hatcher cabinets, the chick handling areas, and the waste and external areas yielded Salmonella most frequently. The likely resident serovar 13,23:i:- was not eradicated during this study, but diligent management and C&D enhancements and targeting, plus effective biosecurity, were eventually followed by a substantial reduction in Salmonella contamination. The percentage of positive samples per visit reduced to 2.3% from a mid-study peak of 23%. The antimicrobial resistance was varied, infrequent (detected in 4% of tested isolates), and did not show longitudinal trends. This study shows that long-term Salmonella hatchery contamination may be susceptible to targeted interventions, as informed by repeated sampling, provided that biosecurity is of a high standard and C&D (including biofilm disruption) has been optimised. Importantly, it also illustrates the long timescale over which interventions may be required to reduce resident Salmonella contamination.