Campylobacter jejuni has been identified as the leading cause of acute bacterial diarrhea in the United States, yet compared with other enteric pathogens, considerably less is understood concerning the virulence factors of this human pathogen. A random in vivo transposon mutagenesis system was recently developed for the purpose of creating a library of C. jejuni transformants. A total of 1,065 C. jejuni transposon mutants were screened for their ability to swarm on motility agar plates and autoagglutinate in liquid cultures; 28 mutants were subsequently identified. The transposon insertion sites were obtained by using random-primed PCR, and the putative genes responsible for these phenotypes were identified. Of these mutants, all 28 were found to have diminished motility (0 to 86% that of the control). Seventeen motility mutants had insertions in genes with strong homology to functionally known motility and chemotaxis genes; however, 11 insertions were in genes of unknown function. Twenty motility mutants were unable to autoagglutinate, suggesting that the expression of flagella is correlated with autoagglutination (AAG). However, four mutants expressed wild-type levels of surface FlaA, as indicated by Western blot analysis, yet were unable to autoagglutinate (Cj1318, Cj1333, Cj1340c, and Cj1062). These results suggest that FlaA is necessary but not sufficient to mediate the AAG phenotype. Furthermore, two of the four AAG mutants (Cj1333 and Cj1062) were unable to invade INT-407 intestinal epithelial cells, as determined by a gentamicin treatment assay. These data identify novel genes important for motility, chemotaxis, and AAG and demonstrate their potential role in virulence.

Updates to the food categorization scheme and new methods for assigning implicated foods to specific food categories can help increase the number of outbreaks attributed to a single food category. The increased specificity of food categories in this scheme may help improve source attribution analyses, eventually leading to improved foodborne illness source attribution estimates and enhanced food safety and regulatory efforts.

Our findings do not warrant rejecting the hypothesis that outbreak and sporadic illnesses are similar. Comparing Sporadic and Outbreak Foodborne Illness

Genetic studies of Campylobacter jejuni have been limited due to the lack of a transposon mutagenesis method. Here, we describe a novel technique for random transposon mutagenesis using amariner-based transposon into C. jejuni strain 480. Insertions were random, as demonstrated by Southern blot analysis and insertional junction sequencing. We have demonstrated, for the first time, random in vivo transposon mutagenesis of C. jejuni.

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