Bacterial Infections

Lyme disease

This is a condition which is caused by the bacteria Borrelia burgdorferi.

Transmission occurs via the Ixodes tick bite, so it is important to ask a detailed travel history to places where these ticks live e.g., forests, parks (e.g., Richmond Park in London has a higher incidence).

It initially causes an expanding area of redness on the skin at the site of the tick bite.

The bacteria can become systemic and spread to the heart, joints and CNS where they can persist for years.

It is thought that the bacteria induce an autoimmune disease secondary to molecular mimicry, which leads to the development of symptoms. 

Symptoms

Initially fever, arthralgia, malaise

Starts with erythema migrans (rash at bite site, appears as a ring of erythema with a central clearing)

The disease can lead to several complications

Complications

Cardiovascular – heart block, acute myocarditis

CNS – can develop after a long time: meningitis, Bell’s palsy and neuropathy

Polyarthritis – lasts even after the bacteria have been eradicated

Key tests

The disease can be diagnosed clinically if erythema migrans is present

1st line is ELISA for antibodies – if positive, do immunoblot test for Lyme disease

Management

Patients should start treatment before the ELISA results come through if there is high clinical suspicion of the disease

In early disease, doxycycline is recommended

In later disease, other antibiotics such as ceftriaxone can be used

Leptospirosis

This is an infection due to the bacteria Leptospira which cause a systemic infection.

Transmission is via contaminated rat urine infected through breaches in the skin/ mucous membranes.

As it is spread in rat urine, it is seen in sewage workers and farmers in particular.

The bacteria spread to various organs, especially the liver, damaging hepatocytes.

Upregulated inflammation can also lead to an interstitial nephritis giving an AKI.

The most severe form of the disease is known as Weil’s disease, and typically causes jaundice due to hepatocyte damage.

Risk factors

Sewage workers and farmers particularly

Symptoms

Fever and flu like symptoms

Jaundice and elevated LFTs, due to liver involvement

Kidney – AKI, low urine output

Bleeding from lungs, gut and mucous membranes (due to depletion of platelets)

Subconjunctival haemorrhages

Key tests

Serological testing for IgM to bacteria is diagnostic

Bloods show raised inflammatory markers

Management

Antibiotics to clear bacteria, e.g., doxycycline/benzylpenicillin

Toxic shock syndrome

This is a condition which is due to an inflammatory reaction to bacterial toxins.

It is caused by S. Aureus or S. pyogenes usually which produce the TSS toxin – 1.

This acts as a superantigen meaning it can stimulate T cells directly and does not need initial processing by an antigen-presenting cell.

T cells are activated giving a cytokine storm and unregulated inflammation.

Risk factors

Tampon use

Skin lesions in young children

Symptoms 

Fever – temperature > 38.9ÅãC

Hypotension – systolic BP < 90 mmHg leading to confusion and lethargy

Headache, watery diarrhoea, non-purulent conjunctivitis

Diffuse red rash, typically like a ‘sunburn’

Desquamation of the rash occurs after 10 days (affecting soles, palms, and lips)

Involvement of 3 or more organ systems e.g., GI (vomiting/diarrhoea at start of disease), kidney (raised creatinine, indicating AKI), liver (abnormal liver function tests)

Management

Will usually require admission to ITU and IV antibiotics

Important to urgently remove/drain source of infection (e.g., remove tampon)