Definitions for the level of evidence (I-IV) and grade of recommendation (A-C) are provided at the end of the "Major Recommendations" field.
Testing, wherever possible, is recommended in all cases of ano-genital ulceration acquired overseas in areas of the world where chancroid is prevalent including Africa, Asia, Latin America, parts of the USA and the Caribbean. The importance of asymptomatic carriage of Haemophilus ducreyi (H. ducreyi) is unclear.
Recommended Tests
Isolation of Causative Agent, H. ducreyi
- Culture of material obtained from the undermined edge of the ano-genital ulcer, after removing superficial pus with a cotton-tipped swab, that is plated directly onto culture medium and incubated at 33 degrees C, in high humidity with 5% carbon dioxide for a minimum of 48 to 72 hours. Transport media have been described but they have not been widely evaluated and in one study have shown little advantage over direct plating. Pus aspirate from inguinal buboes can also be cultured in the same way but the yield is lower than with ulcer-derived material.
- Different strains of H. ducreyi appear to grow preferentially on some culture media and so the use of more than one type of culture medium (described below) is recommended to give the greatest number of positives (sensitivity varies between 33% in low prevalence populations to 80%, in high prevalence populations (Evidence level IIa, Grade of Recommendation B). Addition of a selective agent, 3 mg/l vancomycin, is recommended. (Evidence level III, Grade of Recommendation B)
- Culture media include:
- GC agar supplemented with 1% haemoglobin, 5% foetal calf serum, 1% IsoVitaleX and 3 mg/L vancomycin
- Mueller-Hinton agar supplemented with 5% chocolatised horse blood, 1% IsoVitaleX and 3 mg/l vancomycin
- GC agar supplemented with 1% haemoglobin, 0.2% activated charcoal, 1% IsoVitaleX and 3 mg/l vancomycin
Direct Detection of H. ducreyi by Nucleic Acid Amplification
- There are no commercial tests available but there are a number of laboratories which have described in house tests, some of which also amplify Treponema pallidum and herpes simplex virus (HSV). Molecular detection for H. ducreyi is available via local laboratories sending specimens to the Sexually Transmitted Bacteria Reference Laboratory (STBRL) at the Health Protection Agency (stbrl@hpa.org.uk). (Evidence level IIb, Grade of Recommendation B)
Microscopy
- Detection of sheets of Gram-negative cocco-bacilli has a low sensitivity and is not recommended as a diagnostic test. (Evidence level IV, Grade of Recommendation C)
Serology
- The detection of antibody to H. ducreyi as a marker of chancroid has been useful for epidemiological studies but has no role in direct patient management. (Evidence level III, Grade of Recommendation B)
Recommended Sites for Testing
- Ano-genital ulcer material
- Bubo pus
Factors Which Alter Tests Recommended or Sites Tested
Recent travel by an index patient with genital ulceration (or his/her sexual partner) to a part of the world where chancroid is endemic suggests that H. ducreyi infection should be considered as a cause of genital ulceration.
The presence of a bubo may require pus to be aspirated in addition to taking a sample of the ulcer material. The inability of the local laboratory to offer a diagnostic facility for H. ducreyi infection may make it impossible for the clinician to undertake a diagnostic test for chancroid. Due to the infrequency of requests the laboratory diagnosis for chancroid is often unavailable. In low prevalence populations, such as the UK, culture media is often produced in response to a typical clinical presentation, which has made it very difficult to maintain good quality control. There is no quality assurance programme for culture for H. ducreyi in the UK.
Risk Groups
- Men who have sex with men (no alteration to standard recommendation)
- Sex workers (no alteration to standard recommendation)
Other Groups
- 'Young' patients (no alteration to standard recommendation)
- Pregnant women (no alteration to standard recommendation)
- Women with a history of hysterectomy (no alteration to standard recommendation)
Recommendation for Frequency of Repeat Testing in an Asymptomatic Patient
- Testing should only be performed in the presence of an ano-genital ulcer or a bubo in an individual at risk of acquiring chancroid
- Screening asymptomatic patients is not recommended
Recommendation for Test of Cure
- A test of cure for chancroid is not recommended
- If ulceration persists after therapy for chancroid, patients should have a repeat chancroid culture performed to determine if a strain of H. ducreyi resistant to the prescribed antimicrobial is present
Definitions:
Levels of Evidence
Ia: Evidence obtained from meta-analysis of randomised controlled trials
Ib: Evidence obtained from at least one randomised controlled trial
IIa: Evidence obtained from at least one well designed controlled study without randomisation
IIb: Evidence obtained from at least one other type of well designed quasi-experimental study
III: Evidence obtained from well designed non-experimental descriptive studies
IV: Evidence obtained from expert committee reports or opinions and/or clinical experience of respected authorities
Grading of Recommendations
- Evidence at level Ia or Ib
- Evidence at level IIa, IIb, or III
- Evidence at level IV
