Plasmid profile analysis and antibiotic resistance of Salmonella strains from clinical isolates in Cluj-Napoca.

Resistance patterns, plasmid profiles and the genetic resistance determinants were investigated in 38 isolates of Salmonella enterica serotype Typhimurium and 19 isolates of Salmonella enterica serovar Enteritidis derived from children hospitalized in two clinics in Cluj-Napoca, during the period of 1995-1997. Incidence of plasmid and antibiotic resistance was very high in Salmonella typhimurium isolates. All strains were resistant to almost all antibiotics tested but susceptible to the third generation cephalosporines and fluoroquinolones. We identified three resistance patterns and six plasmid profiles. Each plasmid profile was characterized by the presence of two large plasmids of 150-180 Kbp. Approximately 60% of strains harbored three or four small plasmids of 1.3 to 9.5 Kbp. The plasmids of 8.5 Kbp encoded resistance to beta-lactam antibiotics and were non-conjugative. The other small plasmids were cryptic and also non-conjugative. Salmonella enteritidis isolates were susceptible to many antibiotics, except Tetracycline and Trimethoprim-Sulfamethoxazole. We identified three different resistance patterns but nine plasmid profiles. All plasmid profiles were characterized by the presence of a large plasmid (> 100 Kbp). The number and the diversity of small plasmids were higher than in S. typhimurium strains. There was no parallelism between resistance and plasmid profile: for the same resistance pattern a number of two or three plasmid profiles were found. Our conclusions are that Salmonella typhimurium strains were multiresistant to antibiotics and that many genetically different strains of Salmonella typhimurium and Salmonella enteritidis were responsible for gastroenteritis in children from Cluj County. The increasing antibiotic resistance highlights the need for more refined methods in genetic and epidemiological characterization of bacteria involved in gastrointestinal infections.