Pre-formed urease activity of as determined by a viable cell count technique–clinical implications Free

Abstract

Summary

The pre-formed urease activity of three NCTC reference strains and five clinical isolates of was determined at room temperature (21°C) and 37°C by a viable cell count technique with a conventional urea slope test (Christensen’s agar) as well as the commercial CLO-test. The urease activity of two gastroduodenal commensals, and , was also tested. . strains produced positive reactions with viable cell counts of 10–10 cfu within 30 min and with counts of 10–10 cfu within 2 h. For some strains, smaller numbers of organisms were needed with the CLO-test than with the conventional test, and incubation of the CLO-test strips at 37°C slightly decreased the number of organisms required for positive results. . produced a positive result on urea slopes with an initial inoculum of 10–10 cfu at 2 h, but no positive reaction occurred for . at 12 h, even with an initial inoculum of 10 cfu. However, both . and . gave a positive result after incubation for 24 h with initial inocula of < 10 cfu and 10–10 cfu respectively. Incubation at 37°C significantly reduced the inoculum size of these organisms required for a positive result after incubation for 4 h when tested with the slopes, but not with the CLO-test. These findings indicate that . possesses much greater pre-formed urease activity than . and . . False negative results for clinical detection of . in gastroduodenal biopsies may be due to small numbers of organisms, especially after treatment with antimicrobial agents, and false positive results may arise from gastroduodenal commensals or contaminants.

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1994-06-01
2024-03-28
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