Evidence for bacteria-independent hatching of Trichuris muris eggs

Abstract

Hatching of infective larvae from embryonated eggs in the intestine is an essential first step in Trichuris infections. There are three isolates of the murine parasitic nematode Trichuris muris: E, E-J (the E isolate maintained in Japan), and S. Incubation of T. muris embryonated eggs with the intestinal bacteria Escherichia coli and Staphylococcus aureus induced in vitro hatching of the eggs, but Enterococcus faecalis failed to induce hatching. Bacteria-induced in vitro hatching of embryonated eggs occurred in the E and E-J isolates, whereas the S isolate was unresponsive to bacteria. T. muris worms recovered from infected mice showed no significant difference between the E-J and S isolates in their infectivity to susceptible B10.BR mice (P>0.05). In vivo hatching of embryonated eggs occurred at 30 min post-infection in the upper and lower halves of the small intestine of ddY mice infected with the E-J or S isolates, and on average, 65% of embryonated eggs recovered from the upper half of the small intestine were hatched in both the E-J and S isolates. In comparison with Enterococcus, the bacteria E. coli and S. aureus represent relatively minor components of the flora of the upper half of the small intestine of mice. These observations point to the possibility that bacteria-independent hatching might also occur in vivo, at least for the S isolate, and imply the existence of a very different system of induction of hatching in vivo.

Helminth Infections and Gut Microbiota: The Futuristic Study of Pathogen Virulence and Gut Ecosystem

“…The experiments showed that E. coli and S. aureus could induce the hatching of E and E-J T. muris eggs under in vitro conditions while E. faecalis could not stimulate the same. Under the same conditions the S isolates were found to be unresponsive to bacterial stimulation [31]. It was also experimentally demonstrated that the egg hatching was suppressed (in E and E-J isolates) when the experiments were carried out in presence of an antibiotic (kanamycin) or when the bacteria used in the experiments were previously incubated at 4°C or fixed with formaldehyde [31].…”

“…Under the same conditions the S isolates were found to be unresponsive to bacterial stimulation [31]. It was also experimentally demonstrated that the egg hatching was suppressed (in E and E-J isolates) when the experiments were carried out in presence of an antibiotic (kanamycin) or when the bacteria used in the experiments were previously incubated at 4°C or fixed with formaldehyde [31]. However, differences in infectivity of E-J and S isolates were not observed [31].…”

“…Koyama [31] went a step further and performed the hatching experiments with all the three available isolates of T. muris eggs [E, E-J and S]. The bacteria used in the experiments were E. coli, S. aureus and Enterococcus faecalis.…”

“…It was also experimentally demonstrated that the egg hatching was suppressed (in E and E-J isolates) when the experiments were carried out in presence of an antibiotic (kanamycin) or when the bacteria used in the experiments were previously incubated at 4°C or fixed with formaldehyde [31]. However, differences in infectivity of E-J and S isolates were not observed [31]. From these experiments Koyama [31] concluded that: a) there must be some bacteriaindependent in vivo hatching mechanism besides a bacteria-dependant one, b) the bacteria must be viable to bring about the hatching and c) the bacteria-mediated hatching of the helminths eggs was needed only for establishment of initial infection.…”

“…From these experiments Koyama [31] concluded that: a) there must be some bacteriaindependent in vivo hatching mechanism besides a bacteria-dependant one, b) the bacteria must be viable to bring about the hatching and c) the bacteria-mediated hatching of the helminths eggs was needed only for establishment of initial infection. The eggs after ingestion passes from the stomach to the upper part of the small intestine (by peristalsis) where the hatching takes place in about 30 minutes post infection [31]. However, this part of the small intestine harbours less of E. coli and S. aureus and more of yeasts, Lactobacillus and Enterococcus [32].…”