ETEC is an underrecognized but extremely important cause of diarrhea in the developing world where there is inadequate clean water and poor sanitation. It is the most frequent bacterial cause of diarrhea in children and adults living in these areas and also the most common cause of traveler's diarrhea. ETEC diarrhea is most frequently seen in children, suggesting that a protective immune response occurs with age. The pathogenesis of ETEC-induced diarrhea is similar to that of cholera and includes the production of enterotoxins and colonization factors. The clinical symptoms of ETEC infection can range from mild diarrhea to a severe cholera-like syndrome. The effective treatment of ETEC diarrhea by rehydration is similar to treatment for cholera, but antibiotics are not used routinely for treatment except in traveler's diarrhea. The frequency and characterization of ETEC on a worldwide scale are inadequate because of the difficulty in recognizing the organisms; no simple diagnostic tests are presently available. Protection strategies, as for other enteric infections, include improvements in hygiene and development of effective vaccines. Increases in antimicrobial resistance will dictate the drugs used for the treatment of traveler's diarrhea. Efforts need to be made to improve our understanding of the worldwide importance of ETEC.

https://cmr.asm.org/content/cmr/18/3/465.full.pdf

Enterotoxigenic escherichia coli in developing countries: epidemiology, microbiology, clinical features, treatment, and prevention

https://www.scielo.br/pdf/bjm/v47s1/1517-8382-bjm-47-s1-0003.pdf

Diarrheagenic Escherichia coli.

Enterotoxigenic Escherichia coli (ETEC) is a leading cause of infectious diarrhea worldwide. Four categories of antigens have been commonly studied: O serogroup, H serogroup, colonization factor antigens (CFA), and toxins. A database has been complied from published reports of nearly 1,000 ETEC isolates from 18 locations and analyzed to determine the occurrence, distribution, and associations of O serogroup, H serogroup, CFA, and toxin type. Tables listing the associations of antigens are presented. This analysis documents the widespread nature and variety of ETEC. Even the most common combination of antigens, O6:H16 CFA/II LTST, accounted for only 11% of the ETEC isolates in the database. It was isolated from 12 locations. Many phenotypes occurred only once. CFA detection based on enzyme-linked antibodies with polyclonal sera is suggested as the preferred assay. A combination of CFA and toxin-based antigens is suggested as the most practical vaccine.

https://cmr.asm.org/content/cmr/10/4/569.full.pdf

Occurrence, distribution, and associations of O and H serogroups, colonization factor antigens, and toxins of enterotoxigenic Escherichia coli.

Publisher Summary Among the protozoa of the Trypanosomatidae family, a large number of species represent agents of diseases, such as Chagas' disease. This chapter reviews some aspects of the cell biology of Trypanosoma cruzi, giving emphasis to those aspects related to the ultrastructure of pathogenic protozoa. Protozoa of the Trypanosomatidae family show, during their, life cycle, several forms which can be easily identified by light microscopy in Giemsa-stained preparations. The chapter also explains the life cycle of T. cruzi. In the life cycle of T. cruzi, there are forms which are able to divide. There is one form, considered to be highly differentiated and responsible for the infectivity of these protozoa, which does not divide. It is highlighted that the trypomastigote form can transform into a rounded form which possesses a free flagellum. This form, which appears in the stomach, is able to transform into either short epimastigotes that start a process of multiplication in the intestinum or into long epimastigotes which move to the more posterior region of the digestive tract of the bug. Cell surface is also emphasized in the chapter.

Cell Biology of Trypanosoma cruzi

Publisher Summary This chapter deals with population genetics of microorganisms, focusing on medically important parasitic protozoa and fungal organisms. It presents comparisons of parasitic protozoa and fungal organisms with population genetics of bacteria. The need to analyze a data in population genetic is crucial and increases proportionally with the scale of time and space considered. The risk that gene exchange interferes with genotype stability is especially great in the genera having a well-known sexual cycle. The risk of sex interfering with the stability of the genotype cannot be ruled out for any microbe, without careful population genetic analysis. Time scale is a central problem in selecting the appropriate marker with a level of resolution. Progress in theoretical interpretation of genetic data depends upon the possibilities of building bridges between previously separate lines of research studying different kinds of microbe. The development of the comparative population genetics makes it possible: (1) to strain typing so that it becomes a really routine and reliable epidemiological tool, (2) to improve and codify microbial taxonomy, and (3) to address the linked central questions which are unanswered.

Population genetics of parasitic protozoa and other microorganisms

The genetic diversity of 47 enterotoxigenic Escherichia coli (ETEC) strains of serotypes O6:H16, O27:H7, O29:H21, O128ac:H12, and O153:H45, previously isolated from diarrheic patients in Brazil over a period of 15 years, was investigated by random amplification of polymorphic DNA (RAPD). Informative band arrays were obtained with three 10-mer primers with G+C contents of 50, 60, and 70%. Based on the combination of the band profiles generated by the three primers 22 RAPD types were detected, and 5 major clonal clusters, each one with at least 80% identical bands, were established. The clonal clusters corresponded to strains having the same serotype which, in most cases, also had the same virulence factors (colonization factors and toxin types) and outer membrane protein and lipopolysaccharide sodium dodecyl sulfate-polyacrylamide gel electrophoresis profiles. The results suggested a correlation between phenotypic properties and genetic relatedness of ETEC isolates of human origin and indicated that a reduced number of clonally related strains are found in areas of ETEC endemicity in Brazil. Moreover, the RAPD technique revealed intraserotype-specific variations, undetectable by the combination of several phenotypic typing methods, among the ETEC strains analyzed. These results show that RAPD typing represents a useful tool for population genetics as well as for epidemiological studies of ETEC.

Random amplification of polymorphic DNA reveals serotype-specific clonal clusters among enterotoxigenic Escherichia coli strains isolated from humans.

Characterization of enterotoxigenic Escherichia coli by random amplification of polymorphic DNA

Reversible Changes in the Isoenzyme Electrophoretic Mobility Pattern and Infectivity in Clones of Trypanosoma cruzi

Herpetomonas samuelpessoai: role of subpellicular microtubules in shape transitions of trypanosomatids.

A Salmonella agona strain has caused a hospital outbreak of gastroenteritis in a pediatric unit in Rio de Janeiro. It bears two plasmids, a small (6.5 MDa molecular weight) plasmid coding for type B colicin production and a larger one (36 MDa molecular weight) determining resistance to ampicillin, gentamicin, kanamycin and trimethoprim-sulphamethoxazole. The R-plasmid, but not the Col-plasmid, is self-transferable to a Escherichia coli recipient strain. Curing for the R-plasmid was achieved by treatment with 0.05% SDS followed by incubation at 44 degrees C. It has not been possible to cure the S. agona strain for its Col-plasmid.

/pdf/identification-of-multiple-resistance-r-and-colicinogeny-col-z1e9ctgzfi.pdf

D. F. De Almeida

Papers

Random amplification of polymorphic DNA reveals serotype-specific clonal clusters among enterotoxigenic Escherichia coli strains isolated from humans.

Characterization of enterotoxigenic Escherichia coli by random amplification of polymorphic DNA

Reversible Changes in the Isoenzyme Electrophoretic Mobility Pattern and Infectivity in Clones of Trypanosoma cruzi

Herpetomonas samuelpessoai: role of subpellicular microtubules in shape transitions of trypanosomatids.

Identification of multiple-resistance (R) and colicinogeny (Col) plasmids in an epidemic Salmonella agona serotype in Rio de Janeiro