Chapter 139. Haemophilus Infections (Kỳ 5) Clinical Manifestations Infection is acquired as the result of a break in the epithelium during sexual contact with an infected individual. After an incubation period of 4–7 days, the initial lesion—a papule with surrounding erythema—appears. In 2 or 3 days, the papule evolves into a pustule, which spontaneously ruptures and forms a sharply circumscribed ulcer that is generally not indurated (Fig. 139-2). The ulcers are painful and bleed easily; little or no inflammation of the surrounding skin is evident. Approximately half of patients develop enlarged, tender inguinal lymph nodes, which frequently become fluctuant and spontaneously rupture. Patients usually seek medical care after 1–3 weeks of painful symptoms. The presentation of chancroid does not usually include all of the typical clinical features and is sometimes atypical. Multiple ulcers can coalesce to form giant ulcers. Ulcers can appear and then resolve, with inguinal adenitis (Fig. 139- 2) and suppuration following 1–3 weeks later; this clinical picture can be confused with that of lymphogranuloma venereum (Chap. 169). Multiple small ulcers can resemble folliculitis. Other differential diagnostic considerations include the various infections causing genital ulceration, such as primary syphilis, condyloma latum of secondary syphilis, genital herpes, and donovanosis. In rare cases chancroid lesions become secondarily infected with bacteria; the result is extensive inflammation. Diagnosis Clinical diagnosis of chancroid is often inaccurate, and laboratory confirmation should be attempted in suspected cases. Gram's staining of a swab of the lesion may reveal a predominance of characteristic gram-negative coccobacilli, but the presence of other bacteria often makes it difficult to interpret this result. An accurate diagnosis of chancroid relies on culture of H. ducreyi from the lesion. In addition, aspiration and culture of suppurative lymph nodes should be considered. Since the organism can be difficult to grow, the use of selective and supplemented media is necessary. A multiplex polymerase chain reaction assay has been developed for simultaneous amplification of DNA targets from H. ducreyi, Treponema pallidum, and herpes simplex virus types 1 and 2. When this assay becomes commercially available, it will be a useful diagnostic tool with which to identify the etiology of genital ulcers. Haemophilus ducreyi: Treatment The treatment regimen recommended by the Centers for Disease Control and Prevention is a single 1-g oral dose of azithromycin. Alternative regimens include ceftriaxone (250 mg intramuscularly in a single dose), ciprofloxacin (500 mg orally bid for 3 days), or erythromycin base (500 mg orally tid for 7 days). Isolates from patients who do not respond promptly to treatment should be tested for antimicrobial susceptibility. In patients with HIV infection, healing may be slow and longer courses of treatment may be necessary. Clinical treatment failure in HIV-seropositive patients may reflect co-infection, especially with herpes simplex virus. Contacts of patients with chancroid should be identified and treated, whether or not symptoms are present, if they had sexual contact with the patient during the 10 days preceding the patient's onset of symptoms. Further Readings Bong CT et al: Haemophilus ducreyi : Clinical features, epidemiology, and prospects for disease control. Microbes Infect 4:1141, 2002 [PMID: 12361914] Casey JR, Pichichero ME: Changes in frequency and pathogens causing acute otitis media in 1995– 2003. Pediatr Infect Dis J 23:824, 2004 [PMID: 15361720] Committee on Infectious Diseases: Haemophilus influenzae infections, in 2003 Red Book, Report of the Committee on Infectious Diseases , 26th ed, LK Pickering et al (eds). Elk Grove Village, IL, Am erican Academy of Pediatrics, 2003 Dominguez SR, Daum RS: Toward global Haemophilus influenzae type b immunization. Clin Infect Dis 37:1600, 2003 [PMID: 14689338] Heilmann KP et al: Decreasing prevalence of beta- lactamase production among respiratory tract isolates of Haemophilus influenzae in the United States. Antimicrob Agents Chemother 49:2561, 2005 [PMID: 15917574] Kelly DF et al: Haemophilus influenzae type b conjugate vaccines. Immunology 113:163, 2004 [PMID: 15379976] Liebowitz E et al: Haemophilus influenzae : A significant pathogen in acute otitis media. Pediatr Infect Dis J 23:1142, 2004 McGillivary G et al: Cloning and sequencing of a genomic island found in the Brazilian purpuric fever clone of Haemophilus influenzae biogroup aegyptius. Infect Immun 73:1927, 2005 [PMID: 15784532] Murphy TF: Respiratory infections caused by non-typeable Haemophilus influenzae. Curr Opin Infect Dis 16:129, 2003 [PMID: 12734445] ———et al: Persistent colonization by Haemophilus influenzae in chronic obstructive pulmonary disease. Am J Respir Crit Care Med 170:266, 2004 Sethi S et al: Strain-specific immune response to Haemophilus influenzae in chronic obstructive pulmonary disease. Am J Respir Crit Care Med 169:448, 2004 [PMID: 14597486] . Chapter 139. Haemophilus Infections (Kỳ 5) Clinical Manifestations Infection is acquired as the result of a break. purpuric fever clone of Haemophilus influenzae biogroup aegyptius. Infect Immun 73:1927, 2005 [PMID: 15784532] Murphy TF: Respiratory infections caused by non-typeable Haemophilus influenzae among respiratory tract isolates of Haemophilus influenzae in the United States. Antimicrob Agents Chemother 49:2561, 2005 [PMID: 15917574] Kelly DF et al: Haemophilus influenzae type b conjugate