Abstract
EAggEC have been associated with persistent diarrhea in children, yet little is known about virulence factors. Aim. We assayed for enterotoxic activity in culture filtrates(CF) of EAggEC strains.
Methods. CF from 17-2 (a prototype Chilean EAggEC), 8 other EAggEC strains and E. coli HB101 were added to stripped rabbit ileal mucosa(RIM) mounted in Ussing chambers(UCs). CFs were also tested by E. coli STa ELISA and suckling mouse assay (SMA). EAggEC colonies were hybridized under low stringency to STh and STp DNA probes.
Results. Addition of 17-2 CF to the RIM in UCs caused a greater rise in short circuit current (ΔIsc=55.2 ± 5.3 uAmp/cm2)(Mean ± SE) than that seen in HB101 control (ΔIsc=16.8 ± 3.0 uAmp/cm2) (p < 0.001). This activity on Isc was 1)65% stable after heating (15 m at 65°C); 2)localized to the 2-5 kDa MW size range; and 3) reproduced with CF from HB101 transformed with 17-2 plasmid. Compared to ΔIsc response to 8-Br-cGMP on negative control tissue ( ΔIsc=123.4 ± 7.9 uAmp/cm2), the ΔIsc to 8-Br-cGMP added to tissue pretreated with 17-2 CF (87.55 ± 8.2 uAmp/cm2)was significantly less (p < 0.01), while the additive effect of 17-2 CF and 8-Br-cGMP (ΔIsc=142.8 ± 9.1 uAmp/cm2) was not significantly different (p>0.05). <10 kDa CF fractions from 6/8 other EAggEC strains screened in UCs gave ΔIsc responses similar to 17-2. The 17-2 CF activity was 1)non-neutralizable with polyclonal anti-STa in UCs; 2)non-reactive by STa ELISA; and 3)negative in SMA. Also, EAggEC colonies did not hybridize with STh or STp DNA probes.
Conclusions. EAggEC strain 17-2 produces an extracellular, low MW, partially heat stable moiety which gives an electrical response in vitro consistent with an enterotoxic effect. This putative EAggEC heat stable enterotoxin (EAST) appears to be plasmid-mediated, not genetically or immunologically cross-reactive with E. coli STa, and may act via cGMP as intracellular mediator.
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Savarino, S., Fasano, A., Robertson, D. et al. DESCRIPTION OF A PUTATIVE ENTEROTOXIN PRODUCED BY ENTEROAGGREGAT1VE ESCHERICHIA COLI (EAggEC). Pediatr Res 27, 531 (1990). https://doi.org/10.1203/00006450-199005000-00036
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DOI: https://doi.org/10.1203/00006450-199005000-00036
