Comparison of CampyPak II with standard 5% oxygen and candle jars for growth of Campylobacter jejuni from human feces

Potential role for Streptococcus gordonii-derived hydrogen peroxide in heme acquisition by Porphyromonas gingivalis

Streptococcus gordonii, an accessory pathogen and early colonizer of plaque, co-aggregates with many oral species including Porphyromonas gingivalis. It causes α-hemolysis on blood agar, a process mediated by H₂ O₂ and thought to involve concomitant oxidation of hemoglobin (Hb). Porphyromonas gingivalis has a growth requirement for heme, which is acquired mainly from Hb. The paradigm for Hb heme acquisition involves the initial oxidation of oxyhemoglobin (oxyHb) to methemoglobin (metHb), followed by heme release and extraction through the actions of K-gingipain protease and/or the HmuY hemophore-like protein. The ability of S. gordonii to mediate Hb oxidation may potentially aid heme capture during co-aggregation with P. gingivalis. Hemoglobin derived from zones of S. gordonii α-hemolysis was found to be metHb. Generation of metHb from oxyHb by S. gordonii cells was inhibited by catalase, and correlated with levels of cellular H₂ O₂ production. Generation of metHb by S. gordonii occurred through the higher Hb oxidation state of ferrylhemoglobin. Heme complexation by the P. gingivalis HmuY was employed as a measure of the ease of heme capture from metHb. HmuY was able to extract iron(III)protoporphyrin IX from metHb derived from zones of S. gordonii α-hemolysis and from metHb generated by the action of S. gordonii cells on isolated oxyHb. The rate of HmuY-Fe(III)heme complex formation from S. gordonii-mediated metHb was greater than from an equivalent concentration of auto-oxidized metHb. It is concluded that S. gordonii may potentially aid heme acquisition by P. gingivalis by facilitating metHb formation in the presence of oxyHb.

Detection of pathogenic Campylobacter species in blood culture systems

Because differences in recognition of Campylobacter fetus and Campylobacter jejuni in systemic infections may be due partially to differences in the ability to cultivate these organisms, we studied their growth characteristics in two widely used blood culture systems. In the Roche Septi-Chek system (Hoffman-La Roche, Inc., Nutley, N.J.), over a broad range of inocula all strains were detected in broth within 2 days and on paddles within 3 days. In the BACTEC 6B aerobic bottles (Johnston Laboratories, Inc., Towson, Md.), C. jejuni and C. fetus took a median of 5 and 3 days, respectively, to reach the growth index threshold. However, in the BACTEC 7D anaerobic bottles, C. fetus required a median of 2 days to reach the growth index threshold, whereas for C. jejuni the median was greater than 10 days. The poor performance of C. jejuni in both BACTEC systems may have been due to unfavorable incubation atmospheres and may partially explain why C. jejuni bacteremia is so infrequently detected. Overall, the Roche Septi-Chek system was excellent for detecting Campylobacter strains in blood cultures.

Evaluation of the Cult-a-Box gas generator system for isolation of Campylobacter spp. from stool specimens

The Cult-a-Box gas generator tablet method for isolating Campylobacter spp. from stool cultures was evaluated by comparison with a standard gas mixture of 5% oxygen, 10% carbon dioxide, and 85% nitrogen. Of the 186 positive cultures, 90.3% were found by both methods. Of the remaining 9.7% which were positive in one system only, 11 were found by the tablet method and 7 by the standard gas method.

A new selective medium for the isolation of Campylobacter jejuni from human faeces

A new selective medium, Butzler's medium Virion, for the isolation of Campylobacter jejuni from human faeces is described. This medium contains the following antibiotics per liter: cefoperazone 15 mg, rifampicin 10 mg, colistin 10,000 IU, and amphotericin B 2 mg. At 42 degrees C there was no difference in the isolation rate on Butzler's medium Virion and Butzler's medium Oxoid, but the competing faecal flora was best suppressed by the new medium which allows easier reading of plates and better recognition of campylobacter colonies. Also, the isolation rate and growth of faecal flora were comparable when this new selective medium was incubated at both 37 degrees C and 42 degrees C in a candle jar or a special incubator. These results suggest that Butzler's medium Virion is a very reliable medium for the isolation of campylobacter. In comparison with other selective media it has important advantages for investigators who have little experience in isolating this enteropathogen, or for developing countries where special 42 degrees C incubators are often not available.