Geographical structure and host specificity in bacteria and the implications for tracing the source of coliform contamination

Abstract

OverviewThis mini-review presents the results of recent studies examining the extent to which among-population variation accounts for the genetic diversity of Escherichia coli and other members of the Enterobacteriaceae. The available population genetic data for E. coli are discussed in relation to an issue perceived to be of public health importance -the coliform contamination of water and efforts to trace the source of such contamination. For E. coli, the data suggest that geographical structure or host specificity accounts for little of the observed genetic diversity. Furthermore, the evidence indicates that there is little temporal stability in the clonal composition of E. coli populations. Consequently, most of the assumptions implicit in any programme attempting to identify the source of coliform contamination that focuses on commensal isolates of E. coli appear to be invalid. Other species of enteric bacteria appear to exhibit greater host specificity and geographical structure. The results of recent studies concerning the distribution of virulence factors among the clonal lineages of E. coli are highlighted and discussed in regard to alternative strategies for tracing the source of coliform contamination.

Protozoan predation, diversifying selection, and the evolution of antigenic diversity in Salmonella

“…For diversifying selection to provide an explanation for serovar-host specificity, both bacterial prey and their protozoan predators must be stably and differentially distributed between host species. Differential distribution of bacteria among hosts, i.e., the nonuniform abundance of different genotypes among different environments, has been convincingly demonstrated for Salmonella (36,57), E. coli (58)(59)(60), Enterococcus (61,62), and Bacteroides (62). Our preliminary data suggest similar results for protozoa, i.e., Naegleria polyphaga was found preferentially in carnivorous metamorphosing Rana catasbiena, whereas Hartmanella was found in herbivorous tadpoles (randomization test, P Ͻ 0.023).…”

Temporal variations in patterns ofEscherichia colistrain diversity and antimicrobial resistance in the migrant Egyptian vulture

“…E. coli showed a much greater geographical effect in non-domesticated, resident wild species relative to isolates in humans suggesting that differential movement patterns influence E. coli strains that predominate in a species [3]. Similarly, in wild species, E. coli exhibit very strong geographic effects, which is likely due to a combination of host taxonomy, diet and climate [2,13,14,15]. Phylogeny of E. coli of wild birds varied concomitant to exposure to humans and human-associated vertebrates such as domestic fowl underscoring the influence of anthropogenic components [5,10].…”

Anticancer Agents from Non-Edible Parts of Theobroma cacao

“…The presence of various phytochemicals active compounds identified are known to have beneficial importance in medicinal properties especially useful in pharmaceutical and therapeutic activities. Plant based natural compounds can be obtained from any part of the tree such barks, leaves, roots, flowers, fruits, seeds and others [31,32]. This important information on phytochemical screening will be helpful as a primary platform for further study on pharmacological aspect in cocoa leaf extract.…”