infection

• A high-resolution computed tomography (HRCT) chest is more commonly used in patients with suspected interstitial lung disease.
• The lungs remain the most common site for secondary tuberculosis. Extra-pulmonary infection may occur in the following areas:

  • central nervous system (tuberculous meningitis - the most serious complication)
  • vertebral bodies (Pott's disease)
  • cervical lymph nodes (scrofuloderma)
  • renal
  • gastrointestinal tract

  
• Campylobacter infection is often self-limiting but if severe (presence of bloody diarrhoea) then treatment with a macrolide e.g. clarithromycin may be indicated

  Ciprofloxacin can be used for strains which are resistant to macrolides. 

  Indications for metronidazole include giardiasis and C.diff infection.
• Campylobacter is the commonest bacterial cause of infectious intestinal disease in the UK. The majority of cases are caused by the Gram-negative bacillus Campylobacter jejuni. It is spread by the faecal-oral route and has an incubation period of 1-6 days.

  • prodrome: headache malaise
  • diarrhoea: often bloody
  • abdominal pain: may mimic appendicitis
• Mycobacterium leprae, the causative organism for leprosy, is endemic in certain areas of India, which accounts for 60% of the world's cases. It is an important diagnosis to consider in endemic regions of the world. Symptoms of leprosy include hypo-pigmented patches, loss of sensation in fingers and toes, thickening of peripheral nerves, and thickening of the skin on the hands and face. Muscle weakness is also a relevant symptom. Acid-fast bacillus (AFB) smears are non-specific for mycobacterium, detecting all species.
• Congo red staining is the diagnostic test for amyloidosis from rectal biopsies, where apple-green birefringence is seen. 
• The Mantoux test is a test for latent tuberculosis, another of the mycobacterium species.
• The monospot test is a test for infectious mononucleosis, glandular fever, detecting the Epstein Barr virus.
• Antiretroviral therapy (ART) involves a combination of at least three drugs, typically two nucleoside reverse transcriptase inhibitors (NRTI) and either a protease inhibitor (PI) or a non-nucleoside reverse transcriptase inhibitor (NNRTI). This combination both decreases viral replication but also reduces the risk of viral resistance emerging
• Staphylococcus aureus is associated with cavitating lesions when it causes pneumonia and has a history of a preceding influenza infection
• Haemophilus influenza can cause cavitating pneumonia, however it is Haemophilus influenzae type A rather than Haemophilus influenzae type B that this occurs in. This organism is a common cause of infections in patients with COPD.
• Klebsiella pneumoniae is more likely in patients with alcohol abuse.
• Mycoplasma pneumoniae is an atypical cause of pneumonia. It may be hinted at by the presence of erythema multiforme or erythema nodosum.
• Streptococcus pneumoniae accounts for around 80% of pneumonia, but is not as linked to cavitating pneumonia as Staphylococcus aureus
• Infection from Legionella is often hinted at by water exposure (e.g. air conditioning), alongside any bradycardia, lymphopenia, deranged liver function tests and/or hyponatraemia.
• Community acquired pneumonia (CAP) may be caused by the following infectious agents:

  • Streptococcus pneumoniae (accounts for around 80% of cases)
  • Haemophilus influenzae
  • Staphylococcus aureus: commonly after influenza infection
  • atypical pneumonias (e.g. Due to Mycoplasma pneumoniae)
  • viruses

  Klebsiella pneumoniae is classically in alcoholics

  Characteristic features of pneumococcal pneumonia

  • rapid onset
  • high fever
  • pleuritic chest pain
  • herpes labialis (cold sores)
• Gonorrhoea is caused by gram-negative diplococcus Neisseria gonorrhoeae. According to the 2019 British Society for Sexual Health and HIV (BASHH) guidelines the new first-line treatment for gonorrhoea infection is a single dose of intramuscular ceftriaxone. However, if ceftriaxone is refused (e.g. needle-phobic) then oral cefixime and oral azithromycin should be used.
• Intramuscular benzathine penicillin is a recommended treatment for suspected or confirmed syphilis.
• Doxycycline is the first-line treatment for Chlamydia trachomatisinfection.
• Gonorrhoea is caused by the Gram-negative diplococcus Neisseria gonorrhoeae. Acute infection can occur on any mucous membrane surface, typically genitourinary but also rectum and pharynx. The incubation period of gonorrhoea is 2-5 days

  • males: urethral discharge, dysuria
  • females: cervicitis e.g. leading to vaginal discharge
  • rectal and pharyngeal infection is usually asymptomatic

  Management

  • If sensitivities are known a single dose of oral ciprofloxacin 500mg
  • if ceftriaxone is refused, oral cefixime 400mg (single dose) + oral azithromycin 2g (single dose) should be used
• Disseminated gonococcal infection (DGI) and gonococcal arthritis may also occur, with gonococcal infection being the most common cause of septic arthritis in young adults.

  • tenosynovitis
  • migratory polyarthritis
  • dermatitis (lesions can be maculopapular or vesicular)
• A calcified Ghon complex may be seen on the CXR of a patient with latent TB

  Miliary TB would present with scattered, very fine nodules throughout the lungs (or other affected areas)Sarcoidosis would typically involve bilateral lymphadenopathy, which would be symmetrical and seen in the hilar area.Small cell lung cancer is very unlikely if a non smoker. Rheumatoid arthritis can lead to fibrotic lung disease but would not typically produce a single calcified nodule.
• NICE now give two choices for treating latent tuberculosis:

  • 3 months of isoniazid (with pyridoxine) and rifampicin, or
  • 6 months of isoniazid (with pyridoxine)

  People with latent tuberculosis cannot pass the disease on to others, so there is no restriction in terms of employment etc. This
• A 3-day course of nitrofurantoin/ trimethoprim may be used to treat an uncomplicated UTI in a non-pregnant woman.

  A 7-day course of nitrofurantoin may be used to treat a catheterised patient if they are symptomatic, a man with a UTI, a pregnant woman with bacteriuria (regardless of symptoms) or a complicated UTI.
• For patients with sign of acute pyelonephritis hospital admission should be considered

  • the BNF currently recommends a broad-spectrum cephalosporin or a quinolone (for non-pregnant women) for 10-14 days
• Diphtheria


  A bacterial-mediated disease which primarily affects the mucous membranes of the throat and nose
• Diphtheria

  • Recent history of foreign travel to an endemic area (e.g. Eastern Europe)
  • Pseudomembrane formation (formation of a brown-greyish membrane covering the pharynx and tonsils as a result of dead tissue and fibrin accumulation at the site of infection)
  • Sore throat
  • Fever
• Diphtheria toxin


  Can spread to the myocardium and interfere with the normal functioning of the heart's conduction system and in some cases damage the AV node
• Complete heart block can also be seen in diphtheria
• In a patient who has not been previously immunised against rabies and has sustained a potential rabies exposure, such as a dog bite in an endemic area like Ecuador, the most appropriate management includes both passive and active immunisation. Passive immunisation with human rabies immunoglobulin (HRIG) provides immediate protection by neutralising the virus, while active immunisation with a full course of vaccination allows the patient's immune system to develop long-term protection.
• Ziehl-Neelson stain

  Stain used to identify Cryptosporidium infection
• Cryptosporidium infection

  Protozoal infection of the GI tract
• Cryptosporidium infection is most common in children and those with HIV
• Cryptosporidiosis


  Difficult to treat, does not respond well to medication
• Nitazoxanide


  Has shown some efficacy, limited use to immunocompromised patients or persistent cases in immunocompetent patients
• Cryptosporidium infection in immunocompetent patients

  Usually self-limiting, does not require specific treatment
• Advice for Cryptosporidium infection in immunocompetent patients

  1. Stay hydrated (may need rehydration therapy)

  2. Maintain nutrition

  3. Rest until symptoms resolve
• You would not give a beta-blocker to a hypotensive patient who is septic as this might lead to a further decompensation in their blood pressure.
• An active syphilis infection would be diagnosed with a positive non-treponemal test and a positive treponemal test. Partially treated syphilis would present with a positive treponemal test. Successfully treated syphilis would present with a negative non-treponemal test and a positive treponemal test, as the cardiolipin tested by the non-treponemal test decreases over time, but the antibodies tested by the treponemal test remain.
• Anaphylaxis - serum tryptase levels rise following an acute episode and remain elevated for up to 12 hours