HAEMOPHILUS DUCREYI: CHARACTERISTICS, CULTURE, PATHOLOGY - BIOLOGY - 2025

Haemophilus ducreyi is a Gram-negative coccobacillary bacterium that causes a sexually transmitted disease, called soft chancre, chancroid or Ducrey's disease. This pathology is characterized by the appearance of ulcerative lesions that are located at the perigenital and perianal level.

The disease is global in distribution and was endemic until the 20th century. Especially in wartime this disease was as important a health problem as gonorrhea.

Chocolate agar with colonies of the genus Haemophilus

Currently it is more common to diagnose it in the Caribbean, Africa and Asia, where it is the causal agent of 23 to 56% of ulcers in the genital area. There are also sporadic outbreaks in the United States and Canada.

The prevalence is estimated to range between 6 to 7 million cases annually worldwide, according to data from the World Health Organization (WHO). However, it is known that there are sub-records, due to the difficulty at times in confirming the diagnosis.

It has been determined that the frequency rate has been higher in heterosexual than homosexual couples, where the probability of contagion with a single sexual exposure is 0.35%.

Therefore, like any sexually transmitted disease, it is common to observe it in promiscuous people, such as prostitutes. Likewise, some studies speak that the infection is more frequent in uncircumcised men and associated more with the black race than the white.

On the other hand, in underdeveloped countries, chancroid lesions are considered a risk factor for acquiring the human immunodeficiency virus (HIV) in heterosexuals, with ulcerative lesions serving as a gateway for the virus.

General characteristics

Phylum: Proteobacteria

Class: Gammaproteobacteria

Order: Pasteurellales

Family Pasteurellaceae

Genus: Haemophilus

Species: ducreyi

Morphology

Haemophilus ducreyi in Gram stains of direct samples are observed as Gram negative coccobacilli that take up the dye weakly.

Bacteria are usually accompanied by abundant polymorphonuclear cells.

Likewise, bacteria in the Gram are characteristically arranged in loose clusters (similar to schools of fish), or as clusters of gently curved parallel chains, simulating a railroad track.

Isolated coccobacilli can also be found outside or inside polymorphonuclear cells.

At the culture level, the colonies of Haemophilus ducreyi are usually small, not mucoid with a gray to tan yellow color.

When touched with the platinum handle they can slide on the agar, being difficult to take, and when trying to dissolve them in physiological solution they form an inhomogeneous “lumpy” suspension.

On blood agar the colonies present a small zone of hemolysis around them.

Pathogenesis and pathology

The incubation period is short, usually lasting between three and seven days, without prodromal symptoms.

The lesion begins as a papule, with an erythematous and edematous border at first; after two to three days a pustule forms. These lesions (papule and pustule) are not painful.

Later the formation of a soft ulcer begins, which has indeterminate borders. The lesions are characterized by being torn ulcers, with necrotic and purulent exudate of a yellowish-gray color, very painful.

Multiple lesions are frequently found, due to autoinoculation in very close proximity to each other.

Chancroid ulcers have a very friable base formed by highly vascularized granulation tissue, which is why they bleed easily. These lesions, if not treated, can persist for months.

The patient presents inguinal lymphadenopathy, usually unilateral tender to palpation. It then progresses to a fluctuating inguinal bubo that can drain spontaneously.

Women may experience lymphadenopathy and buboes less frequently, but may instead report other clinical manifestations, such as: leukorrhea, light bleeding, dysuria, frequent urination, and dyspareunia.

Location of injuries

The location of the most frequent lesions in men is at the level of the penis (foreskin, frenulum, glans, coronal and balanopreputial sulcus).

While in women, they can be on the genital lips, perineum, introitus, vestibule, vaginal walls, cervix, and perianal region.

In women, extragenital cases have also been reported due to autoinoculation in the breasts, fingers, hips, and oral mucosa.

Whereas, in homosexuals they can appear on the penis (same places) and in the perianal region.

Types of injuries

Lesions can occur in various ways, which makes diagnosis difficult, hence, a differential diagnosis must be made with other sexually transmitted diseases.

Giant ulcers

They are those that measure more than 2 cm.

Serpeginous ulcers

Formed by the union of small ulcers.

Follicular ulcers

They are those that originate from a hair follicle.

Dwarf ulcers

They are 0.1 to 0.5 cm long, round and shallow. They are confused with herpetic lesions and are distinguished by the irregular base and pointed hemorrhagic edges.

Transient chancroid

It has a rapid evolution of 4 to 6 days, followed by lymphadenitis. This type of ulcer is confused with lymphogranuloma venereum.

Papular chancroid

This type of lesion begins as a papule and then ulcerates, its edges rise, resembling the lesions of condylomata acuminata and secondary syphilis.

Diagnosis

Sampling

The sample should be taken from the bottom and the undercut edges of the ulcer carefully sanitized, with cotton swabs, rayon, dacron or calcium alginate.

Bubo aspirates can also be cultured. However, the ideal sample is that of the ulcer, as this is where the viable microorganism is most often found.

As the samples tend to have low numbers of Haemophilus and at the same time they do not survive long outside the organism, it is recommended to sow it immediately directly in the culture media.

Culture media

For the cultivation of Haemophilus in general, nutritious culture media with special characteristics are required, since this genus is very demanding from a nutritional point of view. Haemophilus ducreyi does not escape it.

For the isolation of H. ducreyi, a medium composed of GC Agar with 1 to 2% hemoglobin, 5% fetal calf serum, 1% IsoVitalex enrichment and vancomycin (3 µg / mL) has been successfully used.

Another useful medium is the one prepared with Müeller Hinton Agar with 5% warmed horse blood (chocolate), 1% IsoVitalex enrichment and vancomycin (3µg / mL).

Growing conditions

The media are incubated at 35 ° C in 3 to 5% CO2 (microerophilia), with high humidity, observing the plates daily for 10 days. Typically, colonies develop in 2 to 4 days.

ID

Semi-automated or automated systems are used for identification, such as the RapIDANA system (bioMerieux Vitek, Inc).

Other diagnostic methods

Monoclonal antibodies directed against H. ducreyi are also used, using an indirect immunofluorescence test to detect the organism in smears prepared from genital ulcers.

Also through molecular biology tests such as PCR, they are the most sensitive.

Treatment

There are several treatment schemes, all very effective. Among them:

• Ceftriaxone, 250 mg single intramuscular dose.
• Azithromycin, 1 g single dose.
• Ciprofloxacin, 500 mg every 12 hours for three days.
• Erythromycin, 500 mg every 6 to 8 hours for seven days.

References

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