Altered hemolysin production in urine-grown uroisolates of Escherichia coli

Fifteen uroisolates of E. coli were studied for both cell-free and cell-bound hemolysin production. Estimations were done in Trypticase soy broth (TSB, providing iron-replete medium) TSB + 2,2'-bipyridine (providing experimentally created iron-depleted conditions) and pooled normal human urine (providing natural iron-depleted growth medium). In TSB 40% of strains showed no detectable cell-free hemolysin, they were able to produce it in the presence of 2,2'-bipyridine and more so when grown in urine. The cell-bound hemolysin was produced by all the strains in TSB, but in the presence of 2,2'-bipyridine and urine an insignificant increase was observed. All the strains when given 2nd and 3rd passage in urine, were found to elaborate significantly more cell-free as well as cell-bound hemolysin.