Pathogen Safety Data Sheets: Infectious Substances – Haemophilus ducreyi



NAME: Haemophilus ducreyi

SYNONYM OR CROSS REFERENCE: Bacillus of Unna-Ducrey (1), The bacillus of Ducrey, Coccobacillus ducreyi (2), The ducreyi bacillus (3), Chancroid (4), Ulcus molle (5), Soft chancre (6).

CHARACTERISTICS: The agent is a fastidious facultative anaerobic (7), gram negative, non spore-forming, cocobaccillus (8). It is 1.5 µm long and 0.5 µm wide (2). In exudates, H.ducreyi is typically seen in a railroad or chaining arrangement (9).

H. ducreyi grows best in microaerophilic conditions at 33-35°C in a humid atmosphere containing 5% CO2 (9). There are numerous artificial media available to cultivate this bacterium (4), and growth usually takes 24-48 hours (2) . Following coloration, bipolar staining can be observed for individual bacteria (10).

The cell wall of H.ducreyi contains lipooligosaccharides. Usually, gram negative bacteria cell walls contain lipopolysaccharides, but the H. ducreyi cell wall lacks the O-antigen (11). The two type strains are differentiated by saccharide chain length: the more common strain expresses a nonasaccharide and the other express a pentasaccharide (10) .


PATHOGENICITY/TOXICITY: Acute bacterial infection usually localized in the genital area. The disease starts with the apparition of tender papule (papular stage) surrounded by a tiny erythematous zone after 4 to 7 days infection during sexual intercourse (4). Lesions can appear on prepuce, fraenulum, glans (2) or anus in men and on the vulva, cervix and perianal area in women. after the lesion next forms a pustule (pustular stage). This pustule ruptures after two or three days and forms an irregularly shaped ulcer with many projection and depression (ulcerative stage). The crater may be filled with yellow or grey purulent exudates and bleed easily if scraped. Depending on the site, ulcers may be more or less painful and size and appearance may vary. Women may also have internal and often painless ulcers (8) . Extragenital cases have been described on the inner thighs, breast and fingers.

Without treatment, the ulcer may become chronic and healing may take up to 3 months (8) . Complications include phimosis (only for men), phagedenic ulceration due to secondary bacterial infection, and unilateral lymphadenopathy (50% of cases (2) ). Affected lymph nodes may become tender and painful buboes. These buboes may spontaneously rupture and form inguinal ulcers.

EPIDEMIOLOGY: Men are more often affected than women (4) . The illness principally occurs in developing countries (occurrence is declining in South East Asia and Africa), but data are lacking (8) . Non-circumcised men are at slightly greater risk (12). Chancroid is a cofactor in HIV transmission, and HIV is a cofactor in Chancroid transmission (8). In developed countries, the outbreaks are often caused by people who have recently returned from endemic areas, sex workers and crack/cocaine consumers.

HOST RANGE: In nature, H. ducreyi can only cause illness in humans (4), but there are animal models (i.e. macaque (13), mouse (14) and swine (15)).

INFECTIOUS DOSE: The infectious dose is unknown (8). Under experimental conditions, 30 CFU of H. ducreyi can cause the formation of papule (rate of 95%) and pustule (69%) in human volunteers (4).

MODE OF TRANSMISSION: H. ducreyi is transmitted through direct contact with open lesions and exudates from lymph nodes during sexual intercourse (8). Auto-inoculation of non-genital sites can occur.

INCUBATION PERIOD: The incubation period is about 4-7 days (4), rarely under 3 days or over 10 days (2).

COMMUNICABILITY: Communicable while infectious agent persists in open lesions or lymph node discharge. The transmission rate by sexual contact is unknown, but increases with the number of sex partners (8) . Men can transmit the disease for five weeks after the appearance of papules and until ulcer healing (based on the assumption that they seek medical help after one to three weeks). The infectious period is unknown for women because duration of ulceration is not known. Without antibiotics, the infectious period is longer.


RESERVOIR: H. ducreyi is a strict human pathogen, and there are asymptomatic cases (8) .




DRUG SUSCEPTIBILITY: H. ducreyi is susceptible to erythromycin, azithromycin, chloramphenicol, norfloxacin, ofloxacin, pefloxacin, ceftriaxone and ciprofloxacin (4, 16). Plasmidic resistance can occur.

DRUG RESISTANCE: Resistance to antimicrobials is increasing, and this has been observed against ampicillin based on beta-lactamase production, tetracycline, sulfamethoxazole, and trimethoprim (16).

SUSCEPTIBILITY TO DISINFECTANTS: Phenolic disinfectants, hypochlorite, alcohols, formaldehyde, glutaraldehyde, iodophore and peracedic acid are effective against H. ducreyi (17).

PHYSICAL INACTIVATION: H. ducreyi can be inactivated by UV light (18), microwave (19) and gamma (20) radiation. It can also be inactivated by moist heat (121°C for at least 20 minutes (21)) and dry heat (165-170°C for 2 hours).

SURVIVAL OUTSIDE HOST: H. ducreyi can survive 2-4 hours (no more than a day) on a cotton swab before medium inoculation (9).


SURVEILLANCE: Monitor for symptoms and confirm infection by laboratory culture of genital lesions (9) . New techniques like PCR and antigen detection are more sensitive, but are not currently commercially available.

Note: All diagnostic methods are not necessarily available in all countries.

FIRST AID/TREATMENT: Treat with appropriate antibiotics (4) . The fluctuant buboes should be aspirated or incised and drained. The patients should also be treated for syphilis if the treatment is given on the basis of physical examination. HIV status should be screened.

IMMUNIZATION: None available.

PROPHYLAXIS: None available.


LABORATORY-ACQUIRED INFECTIONS: One laboratory worker was infected by the bites of an infected mouse (17).

SOURCES/SPECIMENS: Infected specimen, including genital lesion (ulcer lesion material and buboes aspirates) and serum (9).

PRIMARY HAZARDS: Accidentally parental inoculation (9).




CONTAINMENT REQUIREMENTS: Containment Level 2 facilities, equipment, and operational practices for work involving infectious or potentially infectious materials, animals, cultures.

PROTECTIVE CLOTHING: Lab coat. Gloves when direct skin contact with infected materials or animals is unavoidable. Eye protection must be used where there is a known or potential risk of exposure to splashes (23).

OTHER PRECAUTIONS: All procedures that may produce aerosols, or involve high concentrations or large volumes should be conducted in a biological safety cabinet (BSC). The use of needles, syringes, and other sharp objects should be strictly limited (23). Additional precautions should be considered with work involving animals or large scale activities.


SPILLS: Allow aerosols to settle. Wearing protective clothing, gently cover spill with paper towels and apply hypochlorite disinfectant, starting at perimeter and working towards the centre; allow sufficient contact time before clean up (23).

DISPOSAL: All material should be decontaminated before disposal with steam sterilization, incineration or chemical disinfection (23).

STORAGE: Samples and biological material should be store in appropriately labelled sealed containers (23).


REGULATORY INFORMATION: The import, transport, and use of pathogens in Canada is regulated under many regulatory bodies, including the Public Health Agency of Canada, Health Canada, Canadian Food Inspection Agency, Environment Canada, and Transport Canada. Users are responsible for ensuring they are compliant with all relevant acts, regulations, guidelines, and standards.

UPDATED: June 2010

PREPARED BY: Pathogen Regulation Directorate, Public Health Agency of Canada.

Although the information, opinions and recommendations contained in this Pathogen Safety Data Sheet are compiled from sources believed to be reliable, we accept no responsibility for the accuracy, sufficiency, or reliability or for any loss or injury resulting from the use of the information. Newly discovered hazards are frequent and this information may not be completely up to date.

Copyright ©

Public Health Agency of Canada, 2010



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  3. Jones, C. C., & Rosen, T. (1991). Cultural diagnosis of chancroid. Archives of Dermatology, 127(12), 1823-1827.
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  10. Lubwama, S. W., Plummer, F. A., Ndinya-Achola, J., Nsanze, H., Namaara, W., D'Costa, L. J., & Ronald, A. R. (1986). Isolation and identification of Haemophilus ducreyi in a clinical laboratory. Journal of Medical Microbiology, 22(2), 175-178.
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