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About 25 Streptococcus bovis bacteriophages were isolated from abattoir wastes, bovine rumen fluid, and lysogenic strains of S. bovis. Eight phages were selected and characterized by morphology, stability, rate of adsorption, single-step growth curve, serum neutralization, and antigenic relationship. Two distinct morphological phage types were found, one of which has not been previously reported for group D streptococci.
Twenty-six adults with Streptococcus bovis endocarditis and ten with bacteremia alone were studied to determine possible portals of entry. Of 36 patients (17 with endocarditis, eight with bacteremia alone), 25 had gastrointestinal lesions or manipulation. In 22, the gastrointestinal tract appeared to be the source of S bovis bacteremia. Four patients had either carcinoma of the colon (two) or potentially malignant villous adenomas (two) when first seen because of S bovis bacteremia. None of these, nor two other patients with benign colonic polyps, had bowel-related symptoms or signs prior to admission. Since S bovis is a normal intestinal tract inhabitant, bacteremia may frequently be associated with bowel lesions. Streptococcus bovis bacteremia may provide an early clue to the presence of serious and clinically unexpected gastrointestinal disease. Gastrointestinal tract evaluation should be part of S bovis bacteremia patient management, with or without endocarditis.
Forty-eight strains of Streptococcus bovis were tested for induction with mitomycin C. Eleven inducible strains were found and the lysates of all 11 contained bacteriophage-like particles. The lysate of one strain also contained large numbers of particles which closely resembled polyheads. Eight of the lysates produced zones of inhibition on indicator strains and viable bacteriophages were detected in six lysates. The sources of the S. bovis were ovine and bovine rumen fluid (23 strains), ovine and bovine feces (5 strains), blood cultures from human endocarditis (8 strains), and a wide variety of other sources (12 strains). Only 1 of 23 rumen S. bovis strains was lysogenic, which suggests that lysogenic S. bovis strains are not an important source of bacteriophages in the rumen.
Forty-seven strains of Streptococcus bovis were tested for bacteriocin production. Fourteen were found to produce bacteriocins, while all 47 were sensitive to at least one of these bacteriocins. The bacteriocins, on the basis of their host range on S. bovis strains, formed six groups. A representative of each group was selected and characterized by temperature stability, sensitivity to trypsin and lipase, sedimentation by centrifugation, ability to pass through dialysis tubing, host range on other bacterial species, and conditions for production in liquid media. A correlation between mannitol fermentation and bacteriocin production was noted.
Neonatal infections have been caused by Streptococcus bovis, a nonenterococcal group D Streptococcus. A recent case of neonatal meningitis caused by this organism prompted a literature review regarding appropriate antibiotic therapy. Although most reports suggested penicillin therapy alone for S bovis meningitis, isolates of this organism that were as resistant to the lethal effect of penicillin as the enterococcus have been recovered. Therefor, it was recommended that until the results of minimal inhibitory concentration and minimal bactericidal concentration tests are known both an aminoglycoside and a penicillin be used simultaneously. Proved susceptibility to the penicillin would justify discontinuation of the aminoglycoside therapy. Physicians caring for neonates with S bovis should be aware that some strains may be resistant to the lethal effect of penicillin.
Two patients with colonic adenocarcinoma and Streptococcus bovis endocarditis suggested a possible association between the two. Non-enterococcal Group D streptococci were isolated from fecal cultures of 11 of 105 controls, 35 of 63 patients with carcinoma of the colon, seven of 25 with inflammatory bowel disease, four of 21 with non-colonic neoplasms and five of 37 with other gastrointestinal disorders. All such streptococci examined for lactose fermentation were S. bovis. The prevalence of S. bovis in fecal cultures from patients with carcinoma of the colon was significantly increased (P less than 0.001) as compared to that in controls, and also to all other groups (P less than 0.001). No other group had results significantly different from those of controls (P less than 0.05) although patients with inflammatory bowel disease were more frequently carriers. The carrier state was unrelated to age, hospitalization status, colonic stasis, gastrointestinal bleeding or recent barium-enema examination. The implications of this association are unknown.
We prospectively studied patients with Streptococcus bovis septicemia for the presence of gastrointestinal lesions. This study was prompted by our reported findings of the association of fecal carriage of S. bovis with carcinoma of the colon. We studied 29 patients with 30 episodes of S. bovis septicemia. Fifteen completed gastrointestinal evaluations that included colonscopy, surgery, or autopsy. Eight of these had carcinoma of the colon, three had adenomatous polyps of the colon without carcinoma, and two had carcinoma of the esophagus. The 14 patients who did not have complete evaluations included one each with carcinoma of the stomach, gastric lymphoma, and adenomatous polyp of the colon and three with colonic masses not further delineated. Nineteen patients had no gastrointestinal signs or symptoms or stools positive for occult blood at admission. The results of our study suggest that all patients with S. bovis septicemia need aggressive evaluation of the gastrointestinal tract, especially the colon.
Biological characteristics of eleven phages for Streptococcus bovis were investigated; seven phage were isolated from ovine rumen and four were virulent mutants of temperate phages of lysogenic cultures. The phages had many properties in common: similar morphology of negative colonies, the identical spectrum of lytic action, related antigens, absolute or high requirement of calcium ions, thermolability, and inactivation by the content of the rumen. Their susceptibility to the inactivating action of acetic acid, urea and temperature was however different. Chloroform and phenol may be used during purification and conservation of the phages.
The bacteriophage sensitivity of the Streptococcus bovis population resident in the rumens of two fistulated sheep was monitored for 112 days. During this time, three changes in the bacteriophage sensitivity of S. bovis occurred in the absence of detectable bacteriophages. Identical changes in bacteriophage sensitivity occurred simultaneously in both animals and, except for the relatively short periods of changeover in phage sensitivity, the S. bovis population in the rumens of the two sheep was homogeneous with respect to phage sensitivity.
Penicillin G alone is generally recommended for the treatment of infective endocarditis caused by Streptococcus bovis because clinical isolates of S bovis are represented as being uniformly and markedly susceptible to penicillin G. However, two strains of S bovis recovered from two patients with bacterial endocarditis were resistant to the lethal effect of penicillin G. Combination therapy, cefazolin sodium and gentamicin sulfate in patient 1 and penicillin G and gentamicin in patient 2, was necessary; synergy, as manifested by lethal activity against the infecting strains, was demonstrated in the laboratory. We stress the need to determine the minimal lethal concentration of penicillin G for clinical isolates of S bovis. Until such information is available, particularly in life-threatening infections, combination drug therapy, consisting of an aminocyclitol added to a beta-lactam antimicrobic, should be used.
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