Changing clonal patterns of Salmonella enteritidis in Maryland: evaluation of strains isolated between 1985 and 1990.
We examined isolates from 203 sporadic and outbreak-associated Salmonella enteritidis cases occurring in Maryland between 1985 and 1990. Plasmid profiles were determined for all isolates; 52 isolates were phage typed. Ten plasmid profiles were identified. A single profile (consisting of a single ca. 55-kb plasmid) emerged as the predominant profile in Maryland during the study period. This profile (which was closely associated with phage type 8) accounted for 86% of a group of isolates from sporadic cases in 1988 and 1989, compared with 43% of the 1985 isolates. Strains with this profile were identified in four of nine outbreaks, including one of three outbreaks in which eggs were implicated as a vehicle. While plasmid profiles and phage typing appear to provide complementary means of identifying specific strains of S. enteritidis, the emergence of what appears to be a single predominant clone has reduced the discriminant ability of both typing systems. The factors be a single predominant clone has reduced the discriminant ability of both typing systems. The factors contributing to the emergence of this one clone are still not well understood.
Morris
J G
JG
Department of Medicine, University of Maryland School of Medicine, Baltimore.
Dwyer
D M
DM
Hoge
C W
CW
Stubbs
A D
AD
Tilghman
D
D
Groves
C
C
Israel
E
E
Libonati
J P
JP
D001434:Bacteriophage Typing; D006801:Humans; D008396:Maryland; D010957:Plasmids; D012477:Salmonella enteritidis / Q000145:classification / Q000235:genetics / Q000302:isolation & purification*; D013997:Time Factors