Studies on the origin of the  -haemolysin produced by Escherichia coli

Abstract

THE cell-free haemolysin produced by growing certain strains of Escherichia coli on meat-broth medium was originally described by Lovell and Rees (1960) and has been termed a-haemolysin by Smith (1963). Since there have been a number of reports describing other filterable haemolysins (Snyder and Koch, 1966;Walton and Smith, 1969;Muranyi and Juhasz, 1971;Rennie and Arbuthnott, 1971) which might be confused with the a-haemolysin studied in these experiments, the properties that distinguish a-haemolysin from the others produced by E. coli are summarised here. A second type of filterable cell-free haemolysin, first described by Snyder and Koch (1966), differs from a-haemolysin in that it is produced on chemically defined media and is thermostable at 56°C. It is produced later in the growth phase than is a-haemolysin and its appearance is accompanied by a fall in the pH of the culture. A similar type of haemolysin, described by Rennie and Arbuthnott (1971), is produced on chemically defined medium in the presence of various carbohdyrates. It is possible that the haemolytic effects described in both of these reports may be due to the lytic effect of organic acids formed from the carbohydrates in the culture medium, as reported in related studies by Muranyi and Juhasz (1971).Walton and Smith (1969) have described a third type of filterable haemolysin, which they termed y. This haemolysin is found in mutants resistant to nalidixic acid and either its production or its release appears to be affected by nalidixic acid.The fourth haemolysin produced by E. coli is the cell-associated or /3-haemolysin. 8-Haemolytic activity has not been dissociated from intact cells and appears to be dependent on cellular metabolism (Smith, 1963; Short and Kurtz, 1971).It is not possible to determine which of these four types of haemolysin are produced by various strains of E. coli on the basis of the appearance of colonies on blood agar plates, since both a-and p-haemolysin-producing strains give rise to a clear zone of haemolysis (Smith, 1963). Smith found that 53-76% of the faecal samples from healthy pigs, sheep, and oxen contained haemolytic E. coli. He found that 63-92% of the haemolytic strains

Production and properties of haemolysins from clinical isolates of the Proteeae

“…The haemolytic activity of E. coli strains is generally calcium dependent (Bamforth and Dudgeon, 1952;Snyder and Zwadyk, 1969;Short and Kurtz, 1971 ; and heat labile (Love11 and Rees, 1960;Smith, 1963;Snyder and Koch, 1966;Jorgensen et al, 1976). Since, however, the heat lability of the haemolysin is influenced by calcium-being more stable in its absence (Snyder and Koch, 1966)-it is easy to understand why the calciumindependent haemolysin of Proteus spp.…”

Virulence factors in Escherichia coli urinary tract infection

“…Hemolytic activity is maximal in the supernatants of log-phase cultures of hemolytic strains (e.g., 2 to 2.5 at 37°C) and declines as cultures enter stationary phase (233), despite continued production of hemolysin protein (591). Hemolytic activity in culture supernatants is labile, decaying at a rate proportional to the temperature (233,442,497); this lability is not due to degradation of hemolysin (37), despite the sensitivity of hemolysin to proteases (442,489).…”

“…Although cell-bound (beta) hemolysins and secreted hemolysins other than alpha hemolysin have been described (22,233,497,591,593), their prevalence and clinical significance are unknown. This discussion is limited to alpha hemolysin.…”

Haemolysis by urinary Escherichia coli and virulence in mice

“…Four different haemolysins have been described (Jorgensen et al, 1976), and the most important types produced by E. coli are a and /3…”