Lysine decarboxylase-negative Salmonella enterica serovar enteritidis: antibiotic susceptibility, phage and PFGE typing.
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One hundred twenty Salmonella Enteritidis isolates collected from 1992 to 2005 in Nagasaki prefecture (65 isolates from 40 outbreak cases, 44 from sporadic diarrhea patients, and 11 from chicken-related products) were investigated by their antibiotic susceptibility profiles, phage typing, and pulsed-field gel electrophoresis (PFGE) typing. Out of them, 18 were identified as lysine decarboxylase (LDC)-negative isolates, and 15 showed resistance toward streptomycin. Based on the PFGE typing, the isolates were classified into five clusters by UPGMA clustering method. Three LDC-negative isolates belonged to cluster A and were of phage type (PT) 4 and isolated between 2000 and 2004. Other 15 LDC-negative isolates belonged to cluster E. They were PT1, reacted but did not conform (RDNC), or untypable and were isolated between 2001 and 2004. LDC-negative isolates of the cluster A differed from LDC-negative isolates of the cluster E in antibiotic susceptibility profiles, phage typing, and PFGE typing. LDC-negative isolates of the cluster E were isolated after 2001 in Nagasaki prefecture.