CHARACTERIZATION OF MESOPHILIC AEROMONAS FROM CLINICAL SPECIMENS BY COMPUTERIZED ANALYSIS OF SDS-PAGE PROTEIN PROFILES AND BY ENZYMATIC-ACTIVITY

Mesophilic Aeromonas (Aeromonas hydrophila, Aeromonas sobria, Aeromona s caviae) have recently been considered important aetiological agents of human diseases, mainly gastrointestinal infections. Although severa l findings have pointed out the significance of this group of microorg anisms as enteric pathogens and suggested the presence of virulence fa ctors, epidemiological and clinical studies are limited by the difficu lty of correctly identifying mesophilic Aeromonas at the species level . SDS-PAGE of radiolabelled total protein profiles and bacterial enzym atic activities were used to type 31 clinical isolates (6 A. hydrophil a, 7 A. sobria and 18 A, caviae) from patients with gastroenteritis an d from healthy controls. Analysis of SDS-PAGE protein patterns, reinfo rced by the UPGMA-grouping system (AMBIS software) provided a good cha racterization of A. caviae strains as a homogeneous group of microorga nisms, possessing significant differences from the other two species o f mesophilic Aeromonas, in good agreement with biochemical and enzymat ic tests. Data obtained in analyzing A. sobria protein profiles clearl y showed two groups, with a correlation coefficient (CC) 0.70, which i n our experience is a doubtful value for assigning two strains to the same species. Strains biochemically identified as A. hydrophila showed a CC = 0.64, which is equally not acceptable for species assignment. Inter-species comparisen highlighted this heterogeneity, showing two m ixed subgroups, both containing strains that were assigned to A, sobri a and A, hydrophila species on the basis of biochemical features. The taxonomy of A. hydrophila and A. sobria species should be further inve stigated because of their relevance in human pathology: SDS-PAGE and c omputer assisted numerical analysis of their protein profiles might re present a useful tool when supported by other data on virulence factor s, epidemiological and clinical conditions.