In an attempt to elucidate the virulence factors and the pathogenic mechani
sms of Providencia alcalifaciens, 36 isolates identified in 1994-1995 in Re
cife city, Brazil were analysed by PCR to investigate the presence of DNA s
equences homologous to virulence genes described in other invasive enteroba
cteria, as well as their ability to invade HeLa cells, their plasmid profil
es and antibiotic resistance patterns. The genetic diversity of the isolate
s was also analysed by RAPD-PCR. pile homologous sequences of virulence gen
es were observed with any of the P. alcalifaciens isolates studied. Ten iso
lates had no plasmid and 26 harboured one-to-Eve plasmids of 147-<6.9 kb. I
nvasion of HeLa cells was observed in only 10 isolates. No correlation betw
een the plasmid content of the strains, their invasion of HeLa cells or the
ir resistance to antimicrobial drugs could be established. The isolates cou
ld be distributed into 10 genotypic groups by RAPD-PCR. Considering the gen
otypic profile and ability to invade HeLa cells, 7 of the 10 invasive isola
tes belonged to the same genotypic group. The presence of invasive isolates
in the same or a related genotypic group suggests the existence of a clona
l lineage responsible for the invasiveness.