No abstract

No abstract

Some properties of the cell-free and cell-associated hemolysins of Escherichia coli were studied. Several strains of E. coli that were isolated from intestines of pigs with edema disease produce large quantities of cell-free hemolysin when grown in the presence of an extract of meat. The component of meat that stimulates production of cell-free hemolysin is not extracted by lipid solvents and is not dialyzable. The cell-free hemolysin is an acidic substance that occurs in two forms. It is inactivated by trypsin but not by lecithinase, lysozyme, ribonuclease, or deoxyribonuclease, shows optimum activity between pH 7 and 8, and requires calcium ion for activity. It does not appear to be an enzyme. The kinetics of the lytic reaction are most consistent with the hypothesis that one molecule of cell-free hemolysin is sufficient to lyse one erythrocyte and that it is inactivated in the lytic reaction. The cell-free hemolysin does not sufficiently damage the cell during the prelytic period to cause lysis after the hemolysin-calcium-erythrocyte complex has been disrupted. The cell-associated hemolysin was not separated from the cell by autolysis, freezing, sonic treatment, or treatment with trypsin or lysozyme. It appears to be closely associated with the metabolic status of the cell. Organisms that are highly hemolytic under usual conditions of assay immediately lose most of their hemolytic capability in the presence of sodium cyanide, streptomycin, nalidixic acid, and rifampin.

The name "Campylobacter hyointestinalis" sp. nov. is proposed for a Campylobacter species that was isolated from the intestines of pigs with proliferative enteritis. "C. hyointestinalis" is also found in the feces of cattle and has been isolated from the intestine of a hamster. "C. hyointestinalis" is distinguished from previously described catalase-positive Campylobacter species by colony morphology, ability to produce H2S in triple sugar iron agar, ability to grow anaerobically in 0.1% trimethylamine N-oxide hydrochloride, resistance to nalidixic acid, susceptibility to cephalothin and metronidazole, and hydrogenase activity. Sixteen "C. hyointestinalis" strains were highly related (.76%) by DNA-DNA hybridization (hydroxyapatite method, 50 and 65°C). Other Campylobacter species were <30% related to "C. hyointestinalis." The type strain of "C. hyointestinalis" is designated 80-4577-4 (=ATCC 35217), and its DNA has a guanine-plus-cytosine content of 36 mol%.

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