CHANCROID

Chancroid is almost exclusively a sexually transmitted bacterial disease caused by infection with Haemophilus ducreyi. The disease was first described by Ducrey in 1889. It is also described as soft chancre, to differentiate it from syphilitic chancre. Chancroid is endemic in tropical and subtropical countries, but it is sporadic in temperate countries. It is an acute, contagious infection of the genital skin or mucous membranes caused by Haemophilus ducreyi and characterized by painful ulcers and suppuration of the inguinal lymph nodes.

Etiology:  
H. ducreyi a gram negative cocco-bacillary rod with rounded ends and a tendency to occur in end-to-end pairs or short chains. It sometimes demonstrates bipolar staining. It is a fastidious organism, requiring hemin (X factor) for growth and thus is positive in the porphyrin test. H. ducreyi does not require NAD (V factor) for growth.

Clinical features:  
Incubation period ranges from 1 to 7 days. Usually the lesion appears 2-3 days after exposure, but it may be up to a month. An initial macule or papule first appears at the site of inoculation and rapidly passes through vesicular and pustular stages to form a well circumscribed non-indurated ulcer with inguinal lymphadenopathy. The ulcer, which can take different forms, can be single or multiple, and they are very painful. In men, the primary lesions are commonly located on the preputial orifice, frenulum, coronal sulcus and less often on the glans penis and penile shaft. Deeper erosion occasionally leads to marked tissue destruction. The inguinal lymph nodes become tender, enlarged and form an abscess (bubo) in the groin. The infection may be asymptomatic in women, the labia and clitoris are sites of predilection. The perineum and anus are less commonly affected. Auto-inoculation from primary lesions may occur in adjacent skin such as scrotum, thigh and even fingers. 
The H. ducreyi lesion (chancroid) is distinguished from a syphilitic lesion (chancre) in that it is a comparatively soft lesion. Secondary anaerobic infection of the lesions may also occur. Complications include phimosis, urethral stricture, urethral fistula, and severe tissue destruction.

Laboratory diagnosis:

• Specimen collection: Exudate from the edge of the ulcers or pus from a bubo may be collected.

•   Microscopy: Gram-stained smear from the ulcer shows Gram negative coccobacillary rods, which form long trails within mucous strands giving a 'shoal of fish' or 'school of fish' appearance.

• Culture: The organism is more fastidious than H. influenzae but can be grown on chocolate agar, supplemented with IsovitaleX in 5%-10% CO₂ atmosphere and the growth can be detected in 2-4 days. Culture plates should not be discarded as negative until after at least five days of inoculation.

• Antigen detection: The use of specific monoclonal antibodies to detect bacterial antigens is sensitive, specific and less time consuming but are not widely available. 

• Molecular technique: Polymerase chain reaction (PCR) can be used for higher diagnostic accuracy. 

Treatment:  
Antibiotics such as Erythromycin, Co-trimoxazole, Ciprofloxacin, Ceftriaxone, Ofloxacin are effective.