Question
Tric agents
Answer
TRIC agents (an older term standing for Trachoma-Inclusion Conjunctivitis agents) refers to specific serovars of Chlamydia trachomatis historically grouped together because they were first isolated from, and cause, trachoma and inclusion conjunctivitis — before the modern classification of Chlamydia serovars was fully established.
Serovars and disease associations:
- Serovars A, B, Ba, C — cause trachoma, a chronic follicular keratoconjunctivitis endemic in areas of poor hygiene/overcrowding; repeated reinfection leads to conjunctival scarring, entropion, and trichiasis, causing corneal damage and blindness — a leading infectious cause of preventable blindness worldwide.
- Serovars D–K — sexually transmitted serovars causing genital tract infection (urethritis, cervicitis, PID), and, via genital-eye contact or perinatal transmission, adult inclusion conjunctivitis and neonatal inclusion conjunctivitis (ophthalmia neonatorum).
Organism characteristics: C. trachomatis is an obligate intracellular bacterium with a unique biphasic developmental cycle — the infectious, metabolically inert elementary body (EB) attaches to and enters host epithelial cells, then reorganizes into the larger, metabolically active, replicating reticulate body (RB), which multiplies within a cytoplasmic inclusion and eventually reorganizes back into EBs that are released to infect new cells.
Laboratory diagnosis: Giemsa-stained scrapings showing characteristic intracytoplasmic inclusion bodies (Halberstaedter-Prowazek bodies); direct fluorescent antibody test, enzyme immunoassay for chlamydial antigen; nucleic acid amplification tests (PCR) — the current gold standard; McCoy cell culture — the traditional reference method.
Treatment: azithromycin or doxycycline for genital/adult ocular infection; erythromycin for neonatal infection; mass azithromycin distribution and facial hygiene/environmental improvement (SAFE strategy) for trachoma control programmes.