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The adhesin pertactin (Prn) is one of the major virulence factors of Bordetella pertussis, the etiological agent of whooping cough. However, a significant prevalence of Prn-deficient (Prn-) B. pertussis was observed in Japan. The Prn- isolate was first discovered in 1997, and 33 (27%) Prn- isolates were identified among 121 B. pertussis isolates collected from 1990 to 2009. Sequence analysis revealed that all the Prn- isolates harbor exclusively the vaccine-type prn1 allele and that loss of Prn expression is caused by 2 different mutations: an 84-bp deletion of the prn signal sequence (prn1ΔSS, n = 24) and an IS481 insertion in prn1 (prn1::IS481, n = 9). The frequency of Prn- isolates, notably those harboring prn1ΔSS, significantly increased since the early 2000s, and Prn- isolates were subsequently found nationwide. Multilocus variable-number tandem repeat analysis (MLVA) revealed that 24 (73%) of 33 Prn- isolates belong to MLVA-186, and 6 and 3 Prn- isolates belong to MLVA-194 and MLVA-226, respectively. The 3 MLVA types are phylogenetically closely related, suggesting that the 2 Prn- clinical strains (harboring prn1ΔSS and prn1::IS481) have clonally expanded in Japan. Growth competition assays in vitro also demonstrated that Prn- isolates have a higher growth potential than the Prn+ back-mutants from which they were derived. Our observations suggested that human host factors (genetic factors and immune status) that select for Prn- strains have arisen and that Prn expression is not essential for fitness under these conditions. [ABSTRACT FROM AUTHOR]

Streptococcus parauberis is an important bacterial fish pathogen that causes streptococcosis in a variety of fish species including the olive flounder. Despite its importance in the aquaculture industry, little is known about the survival strategy of S. parauberis in the host. Therefore, the objective of this study was to produce genome-wide transcriptome data and identify key factors for the survival of S. parauberis SPOF3K in its host. To this end, S. parauberis SPOF3K was incubated in olive flounder serum and nutrient-enriched media as a control. Although S. parauberis SPOF3K proliferated in both culture conditions, the transcriptomic patterns of the two groups were very different. Interestingly, the expression levels of genes responsible for the replication of an S. parauberis plasmid in the presence of olive flounder serum were higher than those in the absence of olive flounder serum, indicating that this plasmid may play an important role in the survival and proliferation of S. parauberis in the host. Several ATP-binding cassette transporters known to transport organic substrates (e.g., biotin and osmoprotectants) that are vital for bacterial survival in the host were significantly up-regulated in S. parauberis cultured in serum. In addition, groEL, dnaK operon, and members of the clp protease family, which are known to play important roles in response to various stressors, were up-regulated in S. parauberis incubated in serum, thus limiting damage and facilitating cellular recovery. Moreover, important virulence factors including the hyaluronic acid capsule (has operon), sortase A (srtA), C5a peptidase (scp), and peptidoglycan O-acetyltransferase (oatA) were significantly upregulated in S. paraubers in serum. These results indicate that S. paraubers can resist and evade the humoral immune responses of fish. The transcriptomic data obtained in this study provide a better understanding of the mode of action of S. parauberis in fish. [ABSTRACT FROM AUTHOR]