R-Factor in Salmonella enterica serovar typhi: transfer to and acquisition from Escherichia coli.
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 (microg/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.
Mandal
Shyamapada
S
Department of Bacteriology and Serology, Calcutta School of Tropical Medicine, Kolkata 700 073, India. samtropmed@rediffmail.com
Mandal
Manisha Deb
MD
Pal
Nishith Kumar
NK
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D024881:Drug Resistance, Bacterial; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics*; D022761:Gene Transfer, Horizontal; D008826:Microbial Sensitivity Tests; D012485:Salmonella typhi / Q000187:drug effects / Q000235:genetics*; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics*; D014170:Transformation, Genetic
D000900:Anti-Bacterial Agents; C006094:R388; D013762:Tetrahydrofolate Dehydrogenase