Delineation of Aeromonas hydrophila Pathotypes by Dectection of Putative Virulence Factors using Polymerase Chain Reaction and Nematode Challenge Assay

Aeromonas hydrophila is a Gram-negative, bacterial pathogen of humans and other vertebrates. To delineate pathotypes, the genomes of twenty-eight Aeromonas isolates were screened by PCR to determine the presence of virulence factors including: aerolysin (aerA), cytotoxic enterotoxin (act), hemolysin (ahh1), elastase (ahyB), enolase (eno), S-layer protein (ahsA), serine protease (ser), Type IV Aeromonas pilus (tapA), lipase (lip), and Type Three Secretion System (T3SS) components (aopB, ascV). Genes for ahh1, lip, ser, and ahyB were present in all 28 strains tested, others genes varied. The tapA gene encoding a type IV pilus was absent in all 28 isolates screened. After the presence or absence of these genes was determined, corresponding activity was determined using phenotypic assays. Analysis of the data defined 11 different pathotypes based on the genotypic and phenotypic profiles with the largest cluster being ahh1+, ahyB+, lip+, ser+, act+, aerA+, eno-, aopB-, ascV-, ahsA-, and tapA-. Representatives of the pathotype groups were used in a nematode challenge assay and a cell culture assay to assess the importance of virulence factors in their pathogenicity and their cytotoxicity, respectively. All Aeromonas strains tested, with the exception of A. hydrophila ML09-119, showed significantly greater lethality compared to the E. coli negative control in the nematode challenge, yet only A. hydrophila 1127 was significantly more lethal than the positive control Pseudomonas aeruginosa PAO1. Variation in lethality between A. hydrophila strains suggests that C. elegans is a suitable model for studying pathogenic mechanisms and elucidating the combination of factors that define highly virulent strains

T. John Metz

Metz was a building consultant and was invited to evaluate the IWU library at Myers\u27 request based on Metz\u27s work building Carleton\u27s library. He recalls that Myers and Dean Hurwitz had come from institutions with significantly different libraries. He believes faculty were worried about Myers\u27 presidency because he brought in the U-Haul collection. He recalls the visit being different from other experiences because the librarians were acting more as teaching faculty than as career librarians. Metz speaks of the difficulties librarians in many institutions experience with faculty wanting grad school research-type collections and of the unsuitability of that material in an undergraduate collection. He believes Myers thought more like a collector than from the standpoint of focused collection development needs. Metz knew one Carleton faculty member who served as interim president who was a book lover and who also intervened with donors as Myers did