PHAGE TYPES AND RIBOTYPES OF SALMONELLA-ENTERITIDIS IN SOUTHERN ITALY

Differently from other European countries, Southern Italy was affected by a considerable increase in human infections due to Salmonella ente rica subsp. enterica serovar Enteritidis (S. Enteritidis) only after 1 990. On the present investigation, two groups of S. Enteritidis strain s isolated during the low-incidence period 1980-1984 and the epidemic period 1990-1993, respectively, have been submitted to phage-typing an d ribotyping in order to ascertain whether the epidemic increase was d etermined by the spread of a foreign bacterial clone or not. Among the 150 isolates relative to the aforesaid two periods, 12 different phag e types (PTs) were observed. PT4 was the most common phage type among the strains isolated in 1980-1984 (61%) as well as in those of the epi demic period 1990-1993 (72%). PT8 was the second most frequent (33%) p hage type in 1980-1984. It was substituted by PT1 (19%) in the 1990-19 93 period. Analysis of rDNA patterns obtained after Hinc II digestions and Ercherichia coli rRNA hybridizations showed 8 different patterns, A to H. The great majority of the strains studied (140 isolates, 93%) belonged to the ribotype A, showing a similar frequency both in 1980- 1984 (36 of 39, 92%) and in 1990-1993 (104 of 111, 94%). The predomina nce of PT4 and ribotype A among both preepidemic and epidemic strains is in agreement with the hypothesis that host genetic diversity declin e and modern farming practices in the poultry industry have facilitate d a widespread dissemination of preexisting endemic strains. This hypo thesis urges to plan new strategies in preventing S. Enteritidis infec tions.