Marlene Braide Serafim

Incidência de escherichia coli enterotoxigênica (ETEC), rotavirus e Clostridium perfringens de casos de diarréia em crianças, na região de Campinas, SP, Brasil

Foi realizada uma pesquisa na regiao de Campinas, SP, Brasil, sobre a presenca de Escherichia coli enterotoxigenica (ETEC), rotavirus e Clostridium perfringens enterotoxigenico em fezes diarreicas de criancas com ate 2 anos de idade. Dos 132 especimens fecais examinados quanto a presenca de ETEC 27 (20,45%) foram positivos. Destes foram isoladas 41 amostras de ETEC, das quais 40 produziram apenas a enterotoxina termolabil (LT) detectada pelo teste de imuno hemolise radial modifi cado. Entre as 183 amostras de fezes examinadas para rotavirus, 29 (15,84%) foram positivas pelas tecnicas de eletroforese em gel de poliacrilamida (PAGE) e ensaio imunoenzimatico (EIE), sendo que destas, 15 (51,7% ) foram provenientes de materiais coletados nos meses de inverno. Todas as amostras pertenciam ao grupo A e, atraves da tecnica de PAGE, pode-se observar que o tipo eletroforetico mais frequente (9 amostras) foi designado Ib, IIc, Illb, IVa, de acordo com a classificacao por nos adotada. Apenas 113 amostras de fezes foram examinadas para a presenca de C. perfringens enterotoxigenico. Para a deteccao da enterotoxina nos sobrenadantes das culturas foram utilizadas as tecnicas de hemaglutinacao passiva reversa e inoculacao intravenosa em camundongos, sendo encontradas 12 (10,61%) amostras entero-toxigenicas. Diante destes resultados e chamada a atencao sobre o valor apenas relativo de uma coprocultura convencional para fins de diagnostico, ressaltando-se a importância da criacao de metodos simplificados que favorecam a deteccao e identificacao dos grupos de agentes enteropatogenicos estudados na presente pesquisa.

Stability of thermolabile (LT) enterotoxin produced from enterotoxigenicEscherichia coli strains maintained in vitro

The stability of thermolabile (LT) enterotoxin in 26 strains of porcine enterotoxigenicEscherichia coli (PETEC) belonging to serogroups 08 and 0149 was assayed by the passive immune hemolysis (PIH) test, over a period of 9 months at −70°C. It was found that the percentage of LT+ colonies (% LT+) and the mean value of hemoglobin release (¯XHb), could predict a change from LT+ to LT−.

Use of an indirect haemagglutination test, for the detection of Clostridium perfringens type A enterotoxin

An indirect haemagglutination (IH) test is described for the detection of Clostridium perfringens type A enterotoxin, produced by strains isolated from human cases of food poisoning and from contaminated food. Though no strict relationship could be observed between titers in the IH test and the time it took mice to die from the intravenous inoculation of mice (IIM test), results of the supernatants examined by both methods demonstrated that the IH test was more sensitive than the IIM one. No unspecific reaction was obtained in the IH with a negative control and the inhibitions of the IH and IIM tests by specific antiserum against C. perfringens enterotoxin showed that the IH test is very specific. The IH assay is recommended for its sensitivity and easy performance by less-equipped laboratories, by these and other data.

Evaluation of the Biken test to detect heat-labile (LT) enterotoxin produced by porcine and human Escherichia coli strains.

Fifty-seven strains of enterotoxigenic Escherichia coli isolated from humans and pigs and producing thermolabile (LT) enterotoxin were used to ascertain the efficiency of the Biken test compared to the passive immune haemolysis test (PIH), considered as very sensitive for detecting that enterotoxin. The two assays were carried out using anti-porcine (anti-LTp), anti-human (anti-LTh), anti-cholera toxin (anti-CT) and anti-choleragenoid (anti-Cg) antisera. Our results showed that the Biken test was very irregular, with many false-negative results. Positive results (ranging from 78.9 to 22.8) were dependent upon the antiserum used. Conversely, the PIH test was much more efficient in the detection of LT, since 100% of the LT+ strains were positive in this test whatever the antiserum used.