Distribution of virulence factors and molecular fingerprinting of Aeromonas species isolates from water and clinical samples: suggestive evidence of water-to-human transmission.

A total of 227 isolates of Aeromonas obtained from different geographical locations in the United States and different parts of the world, including 28 reference strains, were analyzed to determine the presence of various virulence factors. These isolates were also fingerprinted using biochemical identification and pulse-field gel electrophoresis (PFGE). Of these 227 isolates, 199 that were collected from water and clinical samples belonged to three major groups or complexes, namely, the A. hydrophila group, the A. caviae-A. media group, and the A. veronii-A. sobria group, based on biochemical profiles, and they had various pulsotypes. When virulence factor activities were examined, Aeromonas isolates obtained from clinical sources had higher cytotoxic activities than isolates obtained from water sources for all three Aeromonas species groups. Likewise, the production of quorum-sensing signaling molecules, such as N-acyl homoserine lactone, was greater in clinical isolates than in isolates from water for the A. caviae-A. media and A. hydrophila groups. Based on colony blot DNA hybridization, the heat-labile cytotonic enterotoxin gene and the DNA adenosine methyltransferase gene were more prevalent in clinical isolates than in water isolates for all three Aeromonas groups. Using colony blot DNA hybridization and PFGE, we obtained three sets of water and clinical isolates that had the same virulence signature and had indistinguishable PFGE patterns. In addition, all of these isolates belonged to the A. caviae-A. media group. The findings of the present study provide the first suggestive evidence of successful colonization and infection by particular strains of certain Aeromonas species after transmission from water to humans.

Quality of Packaged Ice Purchased at Retail Establishments in Iowa.

The quality of packaged ice sold in retail establishments is not uniformly regulated, and its cleanliness and safety have not been recently evaluated. This investigation examined the physical, chemical, and microbiological characteristics of 18 brands of packaged ice purchased at Iowa stores. Twenty-two ice samples were melted under controlled conditions and portions were analyzed for selected analytes established as primary and secondary drinking water standards by the U.S. Environmental Protection Agency. Only one sample exceeded a primary health standard under the Safe Drinking Water Act, and that sample contained Klebsiella pneumoniae , a member of the total coliform group of bacteria. Several samples of ice manufactured in convenience stores had heterotrophic plate counts which exceeded the recommendation (<500 CFU/ml) established by the Packaged Ice Association, and none of the manufacturers met the minimum package labeling recommendations of that organization. Ice produced in convenience stores was of consistently poorer microbiological quality than ice produced by major commercial manufacturers. While ice consumption does not represent an immediate threat to personal or public health, the potential for disease transmission exists in an industry which is voluntarily self-regulated.