title: Comparison of culture media for the laboratory diagnosis of chancroid.
abstract: Seven different agar-based media were compared to determine the optimal set of culture media for primary isolation of Haemophilus ducreyi. Also, a new method for sampling genital ulcers -- with a disposable sterile plastic loop -- and processing specimens that provides a standardised inoculum for culture of H. ducreyi on various media is described. A total of 202 patients with genital ulcer disease was enrolled in this study. A sterile swab or plastic loop was used to sample the base of the ulcers and ulcer material was suspended in sterile phosphate-buffered saline. A 100-microl sample of this suspension was mixed with an equal volume of tryptic soy broth containing IsoVitaleX and centrifuged for 1 min. This suspension was used to inoculate the different media. Plates were incubated at 33 degrees C in micro-aerophilic conditions and examined for growth of H. ducreyi after 48 h. Of the 202 specimens, 77 (38.1%) were culture positive for H. ducreyi. None of the agar bases supported the growth of all H. ducreyi strains. Based on this observation, we recommend the universal use of Mueller-Hinton agar base supplemented with chocolate horse blood and IsovitaleX (MH-HBC) and Columbia agar base supplemented with bovine haemoglobin, activated charcoal, fetal calf serum and IsovitaleX (C-HgCh) to enable comparison of prevalence figures for chancroid. In addition, the novel sampling technique described in this study eliminates sampling bias normally associated with genital ulcer specimens.
authors.affiliation: Department of Medical Microbiology, Faculty of Medicine, University of Natal, Durban, South Africa.
authors.forename: A
authors.initials: A
authors.lastname: Pillay
authors.forename: A A
authors.initials: AA
authors.lastname: Hoosen
authors.forename: D
authors.initials: D
authors.lastname: Loykissoonlal
authors.forename: C
authors.initials: C
authors.lastname: Glock
authors.forename: B
authors.initials: B
authors.lastname: Odhav
authors.forename: A W
authors.initials: AW
authors.lastname: Sturm
mesh_terms: D002602:Chancroid / Q000175:diagnosis*; D003470:Culture Media; D006191:Haemophilus ducreyi / Q000302:isolation & purification*; D006801:Humans
chemical_list: D003470:Culture Media