Chlamydiae & Genital Ulcer Bacteria
An intracellular energy parasite and the ulcers that mimic each other
Chlamydial biology and diagnosis
Obligate intracellular energy parasites. Chlamydiae cannot make enough ATP and depend on the host cell for energy. Their envelope lacks a classic peptidoglycan layer (no muramic acid), and they do not grow on artificial media. Treatment therefore relies on drugs that act on bacterial ribosomes, chiefly doxycycline and azithromycin.
Developmental cycle. The small, dense elementary body is the infectious, metabolically inert form. It enters epithelial cells by endocytosis and prevents phagolysosome fusion. Within the membrane-bound inclusion it reorganizes into a larger reticulate body that divides by binary fission, then converts back into elementary bodies that are released when the cell lyses.
Laboratory. C. trachomatis inclusions contain glycogen and stain with iodine; Giemsa also shows them as cytoplasmic inclusions. Culture needs living cell lines, so nucleic acid amplification testing (NAAT) is the standard: a vaginal swab in women, first-catch urine in men, and rectal or pharyngeal swabs by exposure. Because infection is so often silent, sexually active women 24 years and younger are screened every year.
C. trachomatis serovars and disease
| Serovars | Disease | Key features |
|---|---|---|
| A–C | Trachoma | Endemic chronic follicular conjunctivitis in children → lid scarring, trichiasis, corneal blindness |
| D–K | Genital and neonatal infection | Urethritis, cervicitis, PID, epididymitis, proctitis, reactive arthritis; neonatal conjunctivitis and pneumonia |
| L1–L3 | Lymphogranuloma venereum | Transient painless ulcer → painful suppurative buboes; proctocolitis |
Trachoma. Spread among children by hands, flies, and shared cloths in endemic regions, repeated infection scars the tarsal conjunctiva. The lids turn inward (entropion) and the lashes rub the cornea (trichiasis), leading to corneal scarring. It is the leading infectious cause of blindness worldwide and is controlled with lid surgery, mass azithromycin treatment, face washing, and sanitation.
Genital infection. Serovars D–K cause the most commonly reported bacterial STI, frequently asymptomatic in women. Syndromes include nongonococcal urethritis, mucopurulent cervicitis, epididymitis in young men, and proctitis. Ascending infection causes PID with tubal scarring, ectopic pregnancy, infertility, and chronic pelvic pain; perihepatitis (Fitz-Hugh–Curtis syndrome) produces right upper quadrant pain and "violin-string" adhesions between liver capsule and abdominal wall. Reactive arthritis (arthritis, urethritis, conjunctivitis; HLA-B27) can follow.
Neonatal infection. Infants acquire D–K serovars during vaginal delivery. Conjunctivitis begins 5–14 days after birth, later than gonococcal ophthalmia (2–5 days). Pneumonia appears at 1–3 months: afebrile, with a repetitive staccato cough, tachypnea, peripheral eosinophilia, and hyperinflation with interstitial infiltrates.
Lymphogranuloma venereum. L1–L3 serovars invade lymphatics. A small, painless papule or ulcer heals unnoticed; weeks later painful, suppurative inguinal nodes (buboes) appear, sometimes above and below the inguinal ligament (groove sign), and may drain through fistulas. Anorectal infection, mainly in men who have sex with men, causes proctocolitis that can progress to strictures; chronic lymphatic obstruction can cause genital elephantiasis.
Treatment and other chlamydial species
Treatment. Uncomplicated genital infection: doxycycline for 7 days, with single-dose azithromycin as an alternative, plus partner treatment. In pregnancy, azithromycin is used (amoxicillin is an alternative) and a test of cure follows. LGV needs doxycycline for 21 days.
Erythromycin eye ointment at birth prevents gonococcal but not chlamydial conjunctivitis; infected newborns need oral erythromycin (azithromycin is the alternative), and both macrolides carry a risk of pyloric stenosis in infants under 6 weeks.
C. pneumoniae and C. psittaci. Chlamydophila (Chlamydia) pneumoniae spreads person to person and causes atypical pneumonia and bronchitis in adolescents and young adults. C. psittaci causes psittacosis after inhalation of dried droppings from parrots, parakeets, or poultry, with fever, severe headache, and a dry cough. Both respond to doxycycline or a macrolide.
Genital ulcer bacteria
Chancroid. Haemophilus ducreyi, a small gram-negative coccobacillus, causes a painful, soft ulcer with ragged, undermined borders and a gray purulent base, with tender inguinal nodes that may suppurate into buboes. Smears show organisms in parallel chains ("school of fish"). Treatment is single-dose azithromycin or ceftriaxone.
Granuloma inguinale (donovanosis). Klebsiella granulomatis, seen mainly in tropical regions, causes painless, slowly spreading, beefy-red, friable ulcers that bleed on contact, without true lymphadenopathy; subcutaneous granulomas can mimic nodes. Tissue crush preparations or biopsies stained with Wright or Giemsa show Donovan bodies, bipolar-staining bacteria resembling safety pins inside macrophages. Azithromycin is given until the lesions heal; scarring and lymphedema may follow.
| Feature | Chancroid | Granuloma inguinale | Primary syphilis | Genital herpes |
|---|---|---|---|---|
| Organism | H. ducreyi | K. granulomatis | T. pallidum | HSV-2 (or HSV-1) |
| Ulcer | Painful, ragged, purulent | Painless, beefy red, bleeds easily | Painless, indurated, clean base | Painful grouped vesicles on red base |
| Nodes | Tender, suppurative | None (pseudobuboes) | Nontender, rubbery | Tender |
| Diagnostic clue | "School of fish" rods | Donovan bodies | Darkfield, serology | PCR of lesion |