Free UKMLA infection questions with explanations

E. Intravenous ceftriaxone

Reduced fluoroquinolone susceptibility is now so common in Salmonella Typhi from South Asia that ciprofloxacin cannot be used empirically for travellers from that region. For severe or complicated typhoid, such as drowsiness, very high fever or inability to take oral therapy, intravenous ceftriaxone is the empirical choice, with oral azithromycin used for uncomplicated disease. Extensively drug-resistant strains acquired in Pakistan are also ceftriaxone-resistant and need a carbapenem, so travel history and culture sensitivities direct the final choice. Gentamicin is active in vitro but fails clinically because the organism lives inside macrophages. The historic first-line agents (amoxicillin, co-trimoxazole, chloramphenicol) were abandoned because of multidrug resistance.

C. Tetanus immunoglobulin, a dose of tetanus-containing vaccine and wound debridement

A deep puncture wound contaminated with soil or manure is a high-risk tetanus-prone wound, and a patient with no history of immunisation has no protective antibody. He needs immediate passive protection with human tetanus immunoglobulin, which neutralises toxin while the wound is cleaned and devitalised tissue removed, together with active immunisation starting with a dose of tetanus-containing vaccine now and completion of the primary course afterwards. Antibiotics such as metronidazole are also given for a tetanus-prone wound as clinical severity indicates, but they never replace immunoglobulin or vaccine. Vaccine on its own takes weeks to generate protective antibody, too late for a wound already inoculated with spores.

B. Serum lactate

Serum lactate is the perfusion biomarker within the Sepsis Six (UK Sepsis Trust) and Surviving Sepsis Campaign bundles because inadequate oxygen delivery drives anaerobic glycolysis and lactate production. A level above 2 mmol/L signals significant hypoperfusion and above 4 mmol/L carries markedly increased mortality; a lactate over 2 mmol/L in medium-risk sepsis means managing as high risk, with 250 mL fluid boluses and senior review.

C. Aztreonam

Aztreonam is the only clinically used monobactam, with a single beta-lactam ring and no fused second ring. Its structure differs enough from penicillins that cross-reactivity in penicillin-allergic patients is essentially zero (except in patients specifically allergic to ceftazidime, which shares aztreonam's R1 side chain). It covers gram-negative aerobes including Pseudomonas.

Takeaway: Aztreonam is structurally a monobactam with negligible penicillin cross-reactivity; useful for gram-negative cover in penicillin-allergic patients.

C. Prolonged antibiotics with anaerobic cover and postural drainage

An aspiration lung abscess is a polymicrobial, predominantly anaerobic infection, and the great majority resolve with a prolonged course of antibiotics that cover oral anaerobes, typically 4 to 6 weeks, together with physiotherapy and postural drainage because the abscess drains naturally through the bronchial tree. A chest drain must not be inserted into a lung abscess: unlike an empyema, the cavity lies within lung parenchyma and drainage risks a bronchopleural fistula and empyema. Percutaneous or surgical drainage is reserved for abscesses that fail medical treatment, and lobectomy for uncontrolled sepsis, massive haemoptysis or suspected malignancy.

D. Percutaneous drainage with intravenous antibiotics

Pyogenic liver abscesses are treated with broad-spectrum intravenous antibiotics covering enteric Gram-negatives, streptococci and anaerobes, combined with image-guided percutaneous drainage for any collection large enough to drain, usually taken as more than about 3 cm. Antibiotics with observation can be reasonable for small abscesses under about 3 cm, but a 7 cm collection will not sterilise reliably without drainage and risks rupture. Surgical drainage is reserved for multiloculated or ruptured abscesses, or failure of percutaneous drainage. Antibiotics are continued for several weeks with imaging to confirm resolution.

D. Disseminated herpes zoster

Disseminated herpes zoster is the likely diagnosis: in profoundly immunosuppressed patients (CD4 <50), reactivated VZV escapes dermatomal confinement and seeds viscera, producing hepatitis, pneumonitis and encephalitis alongside widespread vesicles. The history of a dermatomal (left chest wall) onset that subsequently disseminated is the key discriminator, and UK guidance (BHIVA opportunistic infection guidelines) mandates IV aciclovir with isolation.

B. Prophylactic low-dose penicillin V

Prophylactic low-dose penicillin V (typically 250 mg twice daily) is the evidence-based intervention to reduce recurrence in patients with two or more cellulitis episodes per year, especially where lymphoedema or chronic venous disease predispose to reinfection. The PATCH I trial demonstrated a significant reduction in recurrence during prophylaxis (PATCH II, in patients after a single episode, did not reach statistical significance), and antibiotic prophylaxis should be considered in this group for at least 12 months alongside oedema management and skin care.

A. Cytotoxic T lymphocytes

Hepatocyte injury in chronic hepatitis B is mediated principally by HBV-specific CD8+ cytotoxic T lymphocytes, which recognise viral peptides presented on MHC class I of infected hepatocytes and induce apoptosis via perforin/granzyme and Fas-FasL pathways. HBV itself is non-cytopathic, which is why immunosuppressed patients can harbour high viral loads with minimal hepatitis, while immune reconstitution precipitates flares.

E. Seek urgent review if breathlessness, chest pain, or new confusion develop

Influenza safety-netting should highlight features suggesting serious complications such as secondary bacterial pneumonia, myocarditis, or encephalitis, namely worsening breathlessness, pleuritic chest pain, haemoptysis, and altered mental state. These warrant urgent reassessment because they indicate progression beyond uncomplicated viral illness. Uncomplicated influenza typically resolves over 7–10 days with supportive care alone.