Reducing suspicion of sexual abuse in paediatric chlamydial conjunctivitis using ompA genotyping

Background

Chlamydia trachomatis is an obligate intracellular Gram-negative bacterium with a biphasic developmental cycle that alternates between infectious extracellular elementary bodies, and non-infectious intracellular reticulate bodies.1 It primarily infects ocular and genital tract epithelial cells. Chlamydial infection of ocular epithelial cells can result in trachoma, neonatal conjunctivitis and adult chlamydial inclusion conjunctivitis.2

The outer membrane protein A (ompA) gene encodes the major outer membrane protein of C. trachomatis. This gene exhibits extensive nucleotide sequence variation that is localised to four discrete regions, termed variable segments I to IV (VS I–IV). ompA genotyping allows for chlamydial strain differentiation.3 Strains with ompA genotypes A–C cause the blinding disease trachoma, which is the leading infectious cause of blindness worldwide. Trachoma is a public health problem in 44 countries, particularly in rural regions of Africa, Central and South America, Asia, Australia and the Middle East.4 C. trachomatis strains with ompA genotypes D–K can cause urogenital infections and adult inclusion conjunctivitis. Chlamydial inclusion conjunctivitis is a chronic mucopurulent follicular conjunctivitis which is often unilateral, with associated lid oedema and non-tender lymphadenopathy. The cornea can show punctate epithelial erosions, subepithelial opacities and marginal infiltrates. It can be challenging to distinguish from other forms of conjunctivitis initially and is often diagnosed from conjunctival swabs when clinical suspicion has been raised.

Case presentation

A 10-year-old female presented to the Ophthalmology Department via her optician describing a 7-month history of persistent left itchy, watery eye and mild lid swelling. She had travelled by land to the UK from an urban centre in Afghanistan 8 months previously. She had no significant medical history or previous eye complaints and had no known allergies. A recent course of chloramphenicol eye drops had been found to make no subjective difference to symptoms or appearance of the eye.

The visual acuity in the right eye was 0.360, left eye 0.380 logMAR visual acuity unaided. The left conjunctiva showed superficial punctate stain and superior injection with fine corneal vascularisation and pannus. There was hyperaemia and papillae of the lower lid subtarsal conjunctiva, with raised fleshy lesions in the inferior fornix, with mild follicular reaction of the superior tarsal conjunctiva. Subepithelial infiltrates were found throughout the central and inferior cornea with no associated epitheliopathy on fluorescein staining. The anterior chamber was deep with no inflammatory cells seen, and the rest of her ocular examination was within normal limits, with a healthy, unaffected right eye. Cycloplegic retinoscopy showed an uncorrected small hypermetropia with astigmatism, and spectacles were prescribed. Findings were atypical for conjunctivitis and given the social context, a conjunctival swab of the left eye was taken and tested for C. trachomatis and Neisseria gonorrhoeae.

Investigations

The swabs taken from the left eye were tested for C. trachomatis and N. gonorrhoeae using the real-time CT/NG combined PCR assay (Abbott). The swab tested positive for C. trachomatis and negative for N. gonorrhoeae. Formal child protection investigations were undertaken by a paediatrician with expertise in child abuse but did not include genital examination or screening for other sexually transmitted infections. The patient denied any inappropriate intimate contact, with no genital pain, vaginal bleeding or discharge. The parents had not knowingly been infected with Chlamydia and denied having any symptoms.

A left conjunctival swab was sent to the Department of Molecular Microbiology at Southampton General Hospital for ompA genotyping. Chlamydial genomic DNA was isolated from the swab using NucleoSpin DNA Trace Tissue Kit (Macherey-Nagel, Germany). ompA was amplified using primers PCTM3 and NR1.5 PCR was carried out in a 20 µL volume consisting of 10 µL Phusion Flash High-Fidelity PCR Master Mix (Thermo Scientific, UK), 500 nM of the forward and reverse primers (Eurogentec, Belgium) and 1 µL of DNA. PCR amplification was conducted using a Veriti Thermal Cycler (Applied Biosystems, UK). The PCR conditions were as follows: initial denaturation at 98°C for 10 s, 40 cycles of 98°C for 2 s, 59°C for 5 s and 72°C for 10 s; and a final extension at 72°C for 1 min. PCR product was purified using the Wizard SV Gel and PCR Clean-Up System (Promega, UK), according to manufacturer’s instructions. PCR amplicons (1 ng/µL/100 bp) were commercially sequenced at Source Bioscience (Cambridge, UK). An alphabetical ompA genotype was assigned to the sample via ompA sequence comparison to the NCBI database using BLAST.

The sample shared the closest ompA sequence identity to strains with ompA genotype C, a known trachoma-causing ompA genotype that has never been associated with urogenital infection. This ruled out the possibility of acquisition of C. trachomatis via sexual routes and established the diagnosis of trachoma.

Outcome and follow-up

Following a 2-week course of oral erythromycin, corneal vascularisation and ocular hyperaemia regressed (figure 1). Symptoms improved subjectively and have been controlled to date with occasional preservative free lubricant eyedrops. Best subsequent visual acuities are 0.18 right eye, 0.5 left eye with spectacle correction 2 years following initial presentation. A coincidental and uncorrected astigmatism has caused the minor reduction in final best vision. Conjunctival swabs were taken from each eye following treatment, and each tested negative for C. trachomatis.

The child protection team were satisfied that this was not a case of sexual abuse, either intrafamilial or non-familial, that no further investigations were required, and child protection proceedings were halted.