CHARACTERISTICS OF INVASION OF HEP-2 CELLS BY PROVIDENCIA-ALCALIFACIENS

Previous studies with three isolates from diarrhoeal stools suggested that Providencia alcalifaciens is an invasive enteric pathogen that al so causes actin condensation in infected cells. These findings were ex tended in the present study with a further 14 diarrhoeal stool isolate s of P. alcalifaciens and HEp-2 cell monolayers for invasion assays. S tudies on invasion characteristics with two selected isolates suggeste d that P. alcalifaciens required prior growth at 37 degrees C for bett er invasion. Invasion and actin condensation were inhibited by an agen t that inhibits microfilament formation, but not by agents that inhibi t receptor-mediated endocytosis, microtubule formation, endosome acidi fication or receptor recycling. In time-course assays with HEp-2 cell monolayers maintained in medium containing gentamicin, P. alcalifacien s showed a small degree of multiplication after invasion of the cells, but viable bacteria could not be recovered over a 24-h period althoug h the integrity of the cell monolayer was preserved during this period .