Jpn. J. Infect. Dis., 56, 65-67, 2003

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Short Communication

R-Factor in Salmonella enterica Serovar Typhi: Transfer to and Acquisition from Escherichia coli

Shyamapada Mandal*, Manisha Deb Mandal and Nishith Kumar Pal

Department of Bacteriology and Serology, Calcutta School of Tropical Medicine, Kolkata 700 073, India

(Received December 10, 2002. Accepted March 28, 2003)

SUMMARY: Blood culture isolates of Salmonella enterica serovar Typhi showing high degrees of resistance to ampicillin, chloramphenicol, cotrimoxazole and tetracycline (ACCoT-resistance) transferred their full resistance phenotype to antibiotic-sensitive S. enterica serovar Typhi strains through the primary recipient Escherichia coli C600. Transfer frequencies were 0.80 x 10^-5 and 0.80 x 10^-6, respectively, in the primary and secondary transfer experiments. The Escherichia coli isolates from urinary tract infection cases showing high minimum inhibitory concentration values (mg/ml) to A (2,000-5,000), C (2,000-5,000), Co (250-1,200), and T (500-2,000) also transferred ACCoT-resistance to the antibiotic-sensitive S. enterica serovar Typhi and then to E. coli C600 with transfer frequencies 0.61 x 10^-6 and 0.98 x 10^-5, respectively. Curing experiments revealed the loss of ACCoT-resistance from the original and the transconjugant S. enterica serovar Typhi strains. Results suggest that R-factor from other enteric bacteria is acquired by S. enterica serovar Typhi, and that it (R-factor) is unstable in nature.

*Corresponding author: Mailing address: Department of Bacteriology and Serology, Calcutta School of Tropical Medicine, C.R. Avenue, Kolkata-700 073, India. E-mail: samtropmed@rediffmail.com

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