Pasteurella testudinis sp. nov.: A Parasite of Desert Tortoises (Gopherus agassizi)

Abstract

A bacterium isolated from desert tortoises fits the major criteria for inclusion in the genus Pasteurella (gram-negative, nonmotile, pleomorphic rods that are facultatively anaerobic, fermentative in their attack on various carbohydrates and catalase, nitratase and oxidase positive). Tests performed for identifying this organism to the species level produced results that fit none of the currently accepted Pasteurella spp. This organism did not hydrolyze urea but did produce indole from tryptophan, hydrolyze o-nitrophenyl-.beta.-D-galactopyranoside and lyse sheep erythrocytes in agar. It fermented a variety of carbohydrates, producing acetic, lactic, propionic and succinic acids as a result of glucose fermentation. All strains were highly susceptible to ampicillin (.ltoreq. 1 .mu.g/ml); the susceptibilities to tetracycline, streptomycin and sulfonamides were variable. Serological tests revealed antigenic heterogeneity and suggested the presence of heat-extractable surface antigens in some strains. Mice succumbed to intranasal and i.p. inoculations of large numbers of some of the strains. The guanine-plus-cytosine content of the DNA was between 46-47 mol%. The Analytab Products API 20E bacterial identification system could not identify some strains of this organism. Other strains were identified as P. multocida or Aeromonas hydrophila at probability levels ranging from 1:69 to 1: > 106. Species status is proposed for these isolates under the name P. testudinis sp. nov. The type strain of this species is strain UCD 90-23-79n (= ATCC 33688).