Chlamydia trachomatis - Microbiology

Snapshot

A 5-year-old girl presents to the community clinic with a complaint of an intensely irritating foreign-body sensation in her left eye. On physical exam, she exhibits erratic twitching of her eyelid, inflammatory thickening of the upper tarsal conjunctiva, and evidence of conjunctival scarring. The girl and her family recently arrived in the United States from a refugee camp in Ethiopia, where they lived in crowded sleeping arrangements and had inadequate water access for personal hygiene.

Overview

Introduction

Classification
- Chlamydia trachomatis
  - obligate intracellular bacteria
Pathogenesis
- transmission
  - sexual intercourse
  - passage through birth canal
  - trachoma transmitted by hand-to-eye contact and flies
- location of infection
  - genital tract
  - eyes
- molecular biology
  - obligate intracellular organism
    - cannot make their own ATP
    - requires live cells for growth in laboratory
  - 2 forms
    - reticulate body
      - intracellular, metabolically active, replicating form
      - "Reticulate Replicates"
      - collections of reticulate bodies can be seen in the cytoplasm under light microscopy and are called "inclusion bodies"
    - elementary body
      - infectious, inactive, extracellular form
      - small, dense
      - "Elementary is Enfectious and Enters cell via Endocytosis"
  - infection of mucosal surfaces leads to granulomatous response and damage
  - cell wall lacks peptidoglycan
    - beta-lactam antibiotics are thus ineffective
Diseases
- trachoma
  - most common cause of preventable blindness
  - serotypes A, B, C
- chlamydia
  - the most common bacterial STD in the United States
  - serotypes D-K
- lymphogranuloma venereum
  - serotypes L1-3 ("L for lymphogranuloma")
Associated conditions
- co-infection with Neisseria gonorrhoeae
- pelvic inflammatory disease (PID)

Presentation

Trachoma
- itching and irritation of the eyes and eyelids
- discharge from the eyes containing mucus or pus
- eyelid inflammation
- blepharospasm
- conjunctival scarring
- trichiasis (inward-growing eyelashes)
Chlamydia
- in females
  - dysuria
  - yellow mucopurulent discharge from the urethra
  - vaginal discharge
  - abnormal vaginal bleeding
  - dyspareunia
  - fever (in pelvic inflammatory disesease)
  - asymptomatic in 80% of patients
- in males
  - dysuria
  - yellow mucopurulent discharge from the urethra
  - unilateral pain and swelling of the scrotum
  - fever
  - asymptomatic in 50% of patients
- in newborns
  - symptoms of conjunctivitis beginning at 1-2 weeks
    - eye discharge
    - eyelid swelling
  - symptoms of pneumonia beginning at 1-3 months
    - cough
    - fever
Lymphogranuloma venereum
- painful, localized inguinal adenopathy (buboes)
- genital ulceration

Studies

Laboratory diagnosis
- polymerase chain reaction (PCR)
- nucleic acid amplification test (NAAT)
- cytology for diagnosing infant conjunctivitis and trachoma
  - visualization of intracytoplasmic inclusions
Histology
- cytoplasmic inclusions (reticulate bodies)
  - seen on Giemsa or fluorescent antibody-stained smear
Additional studies
- pregnancy test for females with suspected chlamydial infection
  - doxycycline contraindicated in pregnancy
- strongly consider testing sexual partners for Chlamydia

Differential

Bacterial vaginosis
- distinguishing factor
  - gray vaginal discharge with a fishy smell
Trichomonas vaginitis
- distinguishing factor
  - frothy, yellow-green discharge
  - motile trichomonads on wet mount
Urinary tract infection
- distinguishing factor
  - lack of cytoplasmic inclusions seen on Giemsa or fluorescent antibody-stained smear

Treatment

Complications