Biofilm formation ability of Campylobacter jejuni isolated from commercial broiler processing plants

Salmonella is a leading bacterial cause of foodborne illness, with ~17% of salmonellosis cases attributed to broilers. Conventional Salmonella isolation procedures involve characterizing a single colony per positive sample. As such, these methods favor the most abundant serovar found in a sample, potentially allowing other serovars to remain undetected. CRISPR-SeroSeq is a novel, high-resolution sequencing approach that can detect and quantify the relative frequency of multiple serovars present in a sample. This study sought to determine how processing interventions influence serovar population dynamics by comparing Salmonella incidence between broiler carcasses at hot rehang and post-chill. We utilized deep serotyping by CRISPR-SeroSeq to analyze paired rehang and post-chill samples, and additional rehang samples without a Salmonella-positive post-chill pair. These samples were collected from broiler processing plants across the United States from August to November 2022. Multiple serovars were detected in 45.3% (24/53) of the samples. The most abundant serovars identified in rehangs (n=41) were Kentucky (78.0%; 32/41), Infantis (34.1%; 14/41), and Typhimurium (22.0%; 9/41). Alternatively, post-chill samples (n=12) contained predominantly Kentucky (91.7%; 11/12). These data demonstrate that processing interventions are effective as sample complexity was reduced in nearly all post-chill samples. Serovars matched between rehang and post-chill carcasses in 50% (6/12) samples, plus they partially matched in an additional 25% (3/12) samples. Deep serotyping was performed on both RV and TT selective enrichment cultures. Statistical analysis comparing serovar populations between the culture types showed that 83.0% (44/53) and 86.8% (46/53) had good matches between the two media, using Bray-Curtis and Jaccard metrics, respectively. This analysis improves our understanding of Salmonella dynamics during processing, which could guide the development of serovar-specific interventions.

Key Words: Salmonella, Food Safety, CRISPR-SeroSeq, Processing, Broiler.