Do temperature-sensitive auxotrophs of Escherichia coli have special virulence?

To determine whether temperature (42 degrees C)-sensitive auxotrophs of Escherichia coli have special virulence properties (W. D. Welch, D. Kitts, H. S. Moyed, and L. D. Thrupp, J. Clin. Microbiol. 13:606-608, 1981), we examined 301 strains isolated from patients with bacteremia or acute cystitis and from the stools of healthy subjects. Of these strains, 49.5% grew at 42 degrees C without supplements, 39.2% required a nutritional supplement, and 11.3% failed to grow even with selected nutrients. Nicotinamide restored growth for 35.2% of strains at either 37 or 42 degrees C. Some of strains required methionine, glutamic, aspartic, and amino acid mixtures or NaCl for growth at 42 degrees C. Temperature-sensitive strains were significantly more abundant in isolates from blood and urine than in stool, but temperature-sensitive auxotrophs were isolated at about the same frequency from each site. There were no discernible clonal patterns, by serotype, among of the nicotinamide-requiring temperature-sensitive auxotrophs. Resistance to trimethoprim-sulfamethoxazole was associated with ability to grow at 42 degrees C. This was not observed with any other antimicrobial drug. Temperature-sensitive strains are a heterogenous group. The relationship of temperature-sensitive auxotrophy to virulence is uncertain.