Diagnosis of viral and chlamydial keratoconjunctivitis: which laboratory test?

Conjunctivitis and keratitis are common forms of ocular morbidity seen in general practice and eye units. 1 2 The aetiology of these diseases includes viral, bacterial, or parasitic infection as well as allergy, trauma, and dietary deficiency.Among the common microbial causes [3][4][5][6][7] (Table 1) are adenovirus, herpes simplex virus (HSV), and Chlamydia trachomatis.Ocular adenovirus infections occur throughout the world in both sporadic and epidemic forms, and large scale outbreaks of epidemic keratoconjunctivitis can occur in hospitals, schools, military establishments, or factories.8 HSV type 1 ocular infection occurs in all countries with an annual incidence of up to 20.7 per 100 000 population and is the most common infective cause of blindness in developed countries.4 9 Trachoma caused by C trachomatis serovars A-C is the leading infectious cause of blindness in the world and is a major public health problem in developing countries.10 Adult chlamydial conjunctivitis, caused by C trachomatis serovars D-K, is an oculogenital infection and up to 90% of patients have concurrent genital infection.[11][12][13] Chlamydial neonatal conjunctivitis (ophthalmia neonatorum) develops in 18%-74% of babies born to mothers with genital chlamydial infection.7 This article reviews available diagnostic laboratory techniques for keratoconjunctivitis caused by adenovirus, HSV, and C trachomatis with special emphasis on modern molecular diagnostic techniques.For information on the clinical features, epidemiology, and treatment of these infections the reader is referred to a number of other reviews.8 9 [14][15][16][17] The need for laboratory investigation Owing to the limited reliability of clinical diagnosis of adenovirus, HSV, and C trachomatis induced keratoconjunctivitis, [18][19][20][21][22][23] accurate laboratory investigation for these agents in conjunctival swabs is often valuable.Failure to diagnose ocular adenoviral disease can result in outbreaks of epidemic keratoconjunctivitis. Prompt recognition of the strains of adenovirus causing this condition in patients can, however, help to contain the development of a hospital based epidemic.24 C trachomatis infection (particularly with serovars D-K) is usually associated with asymptomatic genitourinary colonisation.25 Misdiagnosis of this ocular infection may represent a missed opportunity to detect infection of the genital tract which can ultimately result in a series of complications including pelvic inflammatory disease, epididymitis, ectopic pregnancy, and infertility in the patient and/or partner.11-13 25 In addition, delay in diagnosing chlamydial conjunctivitis and the use of inappropriate antibiotic treatment might trigger chlamydial persistence.26 The availability of appropriate treatment for chlamydia, 16 HSV, 17 and possibly adenovirus 27 together with the potentially serious residual morbidity of these infections clearly justifies the need for accurate laboratory investigation in cases of keratoconjunctivitis. Conventional laboratory techniquesThe conventional techniques for diagnosing viral and chlamydial keratoconjunctivitis include conjunctival cytological investigation [28][29][30] ; inoculation of susceptible cell lines followed by observation of cytopathic eVect or visualisation Table 1 Viral and chlamydial causes of infectious conjunctivitis Causative agent (references) DiVerential diagnosis Epidemiology DNA viruses: Adenovirus (3) EKC Primarily types 8 and 19, but types 2-5, 7, 9, 11, 14, 16, 21-23, and 37 have also been associated with EKC.Highly contagious and transmitted by hand to eye contact, instruments, and solutions.PCF Primarily types 3, 4, and 7; occasionally type 5. Contagious; droplet transmission, particularly in families.NSFC A number of serotypes have been reported including 1-11, 14-17, 19, 20, 22, and 26.HSV (4, 5) Conjunctivitis; keratitis or KC HSV-1 or HSV-2; conjunctivitis is most common in adults and children 1-5 years of age; recurrent disease is common; leading infectious cause of blindness in developed countries.RNA viruses (3): Picornavirus AHC EV70; CA24; common (epidemic or endemic forms) in developing countries; highly contagious.Measles virus (6) MVO Common cause of childhood blindness in developing countries.HSK may complicate measles in developing countries.Chlamydia: C trachomatis (7) NCO The most common form of infectious ophthalmia neonatorum today; occurs in babies born to mothers with genital infection serovars D-K.ACO Oculogenital infection caused by serovars D-K, sometimes by B, and rarely by C; common in developed countries and urban areas of developing countries.Trachoma Most common cause of preventable blindness in the world and common in rural areas of developing countries particularly in Africa, the Middle East, and Asia; caused by serovars A-C.LGV conjunctivitis Very rare and is caused by serotypes L-1, L-2, and L3; transmission either venereally or accidentally in the laboratory.EKC=epidemic keratoconjunctivitis; PCF=pharyngoconjunctival fever; NSFC=non-specific follicular conjunctivitis; KC=keratoconjunctivitis; AHC=acute haemorrhagic conjunctivitis;