Sexually transmitted infections flashcards
18 high-yield MRCP Part 1 cards from the Intellect Medicos Infectious Diseases course. Try to answer each question before you open it — then study them properly with spaced repetition, which brings each card back just before you would forget it.
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What is the first-line (and gold-standard) investigation for chlamydia?
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NAAT (nucleic acid amplification test) — vulvovaginal swab in women, first-void urine in men.
Why? NAAT is the most sensitive and specific test and is used for screening and diagnosis.
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What is the first-line treatment for uncomplicated genital chlamydia (BASHH)?
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Doxycycline 100 mg twice daily for 7 days.
Why? Doxycycline cures more infections than single-dose azithromycin, especially rectal infection; BASHH 2026 makes it the sole first-line treatment.
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What is the first-line treatment for uncomplicated gonorrhoea when sensitivities are unknown (BASHH)?
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Ceftriaxone 1 g IM as a single dose.
Why? High-dose ceftriaxone is used because of rising resistance. Test of cure is no longer routine for anogenital infection treated with ceftriaxone when the strain is known to be susceptible; it is still needed for pharyngeal infection, pregnancy, persistent symptoms, unknown susceptibility or non-ceftriaxone treatment.
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What is the treatment for early (primary, secondary or early latent) syphilis?
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Benzathine benzylpenicillin 2.4 million units IM as a single dose.
Why? Long-acting penicillin keeps treponemicidal levels for weeks (BASHH now recommends giving it with lidocaine). If penicillin cannot be used: doxycycline for 14 days or ceftriaxone for 10 days; macrolides are no longer recommended.
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After successful treatment of syphilis, which test type becomes negative and which stays positive?
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Non-treponemal tests (RPR, used in UK labs instead of VDRL) fall, often to negative; treponemal tests (EIA/CLIA, TPPA) usually stay positive for life.
Why? A quantitative RPR taken on the day treatment starts is the baseline for monitoring response; treponemal tests are not repeated for follow-up.
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A positive VDRL with a negative treponemal test suggests what?
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A biological false-positive VDRL.
Why? Non-treponemal tests detect anti-cardiolipin antibodies, so other conditions can trigger them.
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Which syphilis stage causes a non-itchy rash on the trunk, palms and soles?
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Secondary syphilis.
Why? It follows the painless chancre by weeks and is systemic (fever, lymphadenopathy, mucous patches, condylomata lata).
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Name three features of congenital syphilis.
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Any three of: Hutchinson's teeth, mulberry molars, rhagades, saddle nose, interstitial keratitis, sensorineural deafness, sabre shins.
Why? Late congenital features result from chronic treponemal inflammation during development.
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Which genital ulcer is painful, with ragged undermined edges and painful suppurating inguinal nodes?
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Chancroid (Haemophilus ducreyi).
Why? Gram stain may show a "school of fish" pattern; treat with single-dose azithromycin (or ceftriaxone).
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Which Chlamydia trachomatis infection causes a painless ulcer, then painful inguinal buboes and proctocolitis in MSM?
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Lymphogranuloma venereum (LGV, serovars L1–L3).
Why? Symptomatic LGV is treated with doxycycline for up to 21 days (longer than for ordinary chlamydia).
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What is the first-line investigation for genital herpes?
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NAAT/PCR of a swab from the base of a lesion.
Why? PCR is more sensitive than viral culture and distinguishes HSV-1 from HSV-2.
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What is recommended for a woman who develops a first (primary) episode of genital herpes in the third trimester?
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Treatment-dose oral aciclovir continued until delivery, and a planned caesarean section.
Why? Neonatal herpes risk is very high (about 41%) if a primary infection is still shedding at delivery, because there is no time for maternal antibodies to cross the placenta. Type-specific HSV serology is sent to check whether it is really a recurrence.
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Which HPV types cause most genital warts?
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HPV 6 and 11.
Why? These are low-risk types; HPV 16 and 18 cause most cervical and anal cancers.
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What is first-line treatment for multiple soft, non-keratinised genital warts versus a solitary keratinised wart?
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Multiple non-keratinised: topical podophyllotoxin. Solitary keratinised: cryotherapy.
Why? Imiquimod is the other self-applied option (similar efficacy); podophyllotoxin is usually chosen first because it is cheaper and faster. Neither is licensed in pregnancy, where cryotherapy can be used.
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List Amsel's criteria for bacterial vaginosis (3 of 4 needed).
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Thin white homogeneous discharge; clue cells on microscopy; vaginal pH >4.5; positive whiff test (fishy odour with KOH).
Why? BV is overgrowth of anaerobes such as Gardnerella vaginalis replacing lactobacilli; it is the commonest cause of abnormal discharge in women of childbearing age.
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What is the first-line treatment for symptomatic bacterial vaginosis?
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Oral metronidazole for 5–7 days.
Why? Alternatives include a 2 g single dose of metronidazole, or vaginal metronidazole/clindamycin gel. Male partners do not need treatment.
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A woman has frothy, offensive yellow-green vaginal discharge and vulval itching. Speculum shows punctate haemorrhages on the cervix. What is the first-line treatment?
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Oral metronidazole (BASHH: 7-day course); treat sexual partners too.
Why? This is Trichomonas vaginalis ("strawberry cervix"), a flagellated protozoan; NAAT is the first-line test.
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What is the outpatient treatment of pelvic inflammatory disease (BASHH)?
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IM ceftriaxone 1 g single dose PLUS oral doxycycline and metronidazole for 14 days.
Why? The regimen covers gonorrhoea, chlamydia and anaerobes together.
More Infectious Diseases topics
- Microbiology & antimicrobials
- Skin, soft tissue & Gram-positive infections
- Pneumonia & tuberculosis
- Meningitis & encephalitis
- Gastrointestinal infections
- Viral infections & hepatitis
- HIV & opportunistic infections
- Zoonoses & rickettsial infections
- Malaria & tropical infections
- Worms & helminths
- Vaccines, PEP & asplenia