USE OF PHAGE TYPING COMBINED WITH PULSED-FIELD GEL ELECTROPHORESIS AND POLYERASE CHAIN REACTION IN CHARACTERIZATION OF HUMAN SALMONELLA ENTERITIDIS ISOLATES

Abstract

Phage typing (PT) combined with pulsed-field gel electrophoresis (PFGE) and Polymerase chain reaction (PCR) analysis methods, using 3 kinds of primers ( ERIC, SERE, RAPD) was used in order to characterize human isolates of Salmonella Enteritidis strains. Thirty-six epidemiologically unrelated isolates from outbreaks of foodborne gastroenteritis were studied. Analysis with Xba I, Bln I and Spe I enzymes showed that Xba I gave the highest index of discrimination among strains. Molecular typing by PCR methods was not able to differentiate the isolates belonging to different phage types. We identified eight phage types, with a predominance of PT 8 (42% of isolates). Three PFGE pattern types were obtained with Xba I restriction endonuclease enzyme among the unrelated isolates. The establishment of a highly reliable and discriminatory method for epidemiologic analysis is necessary in order to trace the sources of specific pathogens and, consequently, to control and prevent the spread of epidemic Salmonella Enteritidis isolates to humans. It is concluded that PFGE, in combination with phage typing, represents a suitable tool for the epidemiological typing of Salmonella Enteritidis strains which could be used for investigations or surveillance of the international spread of these clones