STI Microbiology: Pathogens, Diagnosis, Treatment & Complications

Chlamydia (Chlamydia trachomatis)

- Symptoms: observed 7-14 days after infection; causes watery or mucopurulent discharge and dysuria; can cause pelvic inflammatory disease, chronic disease and infertility in females; vertical transmission is possible during vaginal delivery of the baby

- Diagnosis: cell culture - ELISA, urine PCR

- Management: doxycycline, or azithromycin (if pregnant)

Gonorrhoea (Neisseria gonorrhoeae)

- Symptoms: observed 2-7 days - vaginal or urethral discharge, dysuria; males often asymptomatic; females: ++ complications

- Diagnosis: microscopy + culture of discharge, PCR

- Management: ceftriaxone IM with azithromycin

Syphilis (Treponema pallidum)

- Symptoms: incubation period 9-90 days; 4 stages of infection:

- Diagnosis: microscopy + serology

- Management: high dose penicillin

What are the 4 stages of syphilis infection

1) Primary = chancres - lesions (cervix, labia, urethra, penis); 2) Secondary = rash - highly infectious; 3) Latent; 4) Tertiary = decades later, CVS + neurosyphilis + congenital |

HPV

- Transmission: skin to skin

- Symptoms: warts; linked to cancer: cervical, anal, vulvar, penile

- Investigations: Pap smear

- Prevention & Mx: Gardasil vaccine - 6, 11, 16 & 18

HIV

- Transmission: blood, vertical, sexual

- Symptoms: seroconversion symptoms; AIDS

- Investigations: ELISA | Prevention & Mx: HAART (NRTI, NNRTI, protease inhibitor)

- Extra: AIDS-defining illness: toxoplasma, Kaposi sarcoma

Genital herpes (HSV)

- Transmission: Type 1 HSV-1: saliva; Type 2 HSV-2: sexual | Symptoms: Type 1 HSV-1: oral cold sores; Type 2 HSV-2: genital blisters/ulcers; 75% asymptomatic; painful vesicles

- Investigations: genital swab → PCR

- Prevention & Mx: acyclovir (anti-viral)

- lesions heal over 3-4 weeks but recurrent infections are common

Trichomoniasis (Trichomonas vaginalis, flagellated protozoan)

- Transmission: vaginal, oral or anal sexual intercourse | Symptoms: mostly asymptomatic; 50% of women - cervicitis, frothy vaginal discharge; some men - dysuria and penile discharge

- Investigations: PCR on urine or high vaginal swab | - Prevention & Mx: metronidazole

Candida albicans (fungus - normal oral, gut and vaginal flora)

- Transmission: blood, vertical, sexual | Symptoms: overgrowth → vaginal candida (thrush); irritation, inflammation, cheesy discharge +/- dysuria

- Investigations: microscopy + culture of discharge, PCR |

- Prevention & Mx: topical or oral antifungal

- Extra: risk factors: hormone changes (menstruation), diabetes, reduced cell mediated immunity, antibiotic treatment