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. 1987 Aug;25(8):1453–1455. doi: 10.1128/jcm.25.8.1453-1455.1987

In vitro chloramphenicol susceptibility testing of Haemophilus influenzae: disk diffusion procedures and assays for chloramphenicol acetyltransferase.

G V Doern, G S Daum, T A Tubert
PMCID: PMC269246  PMID: 3497944

Abstract

The activity of chloramphenicol against 100 different strains of Haemophilus influenzae was assessed by a macrotube broth dilution technique and by a standardized disk diffusion method using both enriched chocolate agar (CHOC) and Mueller-Hinton agar containing 1.0% hemoglobin and 1.0% IsoVitaleX (BBL Microbiology Systems, Cockeysville, Md.) supplement (CHOC-MHA). Filter disks containing 30 micrograms of chloramphenicol were used with the disk diffusion procedure. The following zone diameter interpretive criteria were defined: CHOC-MHA, less than or equal to 25 mm = resistant [corrected] and greater than or equal to 26 mm = susceptible [corrected]; CHOC, less than or equal to 28 mm = resistant [corrected] and greater than or equal to 29 mm = susceptible [corrected]. all of the H. influenzae strains examined were also characterized by using two rapid assays for chloramphenicol acetyltransferase (CAT) activity: a 1-h tube method (t-CAT) and a 30-min procedure which used commercially available reagent-impregnated disks (d-CAT). The t-CAT procedure was found to be significantly more accurate than the d-CAT procedure as a means for demonstrating production of CAT.

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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