Differentials
Tularaemic bacteraemia
SIGNS / SYMPTOMS
No differentiating signs or symptoms.
INVESTIGATIONS
Positive culture for Francisella tularensis.
Cat scratch disease
SIGNS / SYMPTOMS
Localised lymphadenopathy with a scratch.
INVESTIGATIONS
Positive serology for Bartonella henselae.
Toxoplasmosis
SIGNS / SYMPTOMS
Bilateral lymphadenopathy and fever.
INVESTIGATIONS
Positive IgM serology for Toxoplasma gondii.
Non-tuberculous mycobacterial infections
SIGNS / SYMPTOMS
Unilateral sub-mandibular lymphadenopathy.
INVESTIGATIONS
Excisional biopsy of the node and culture of mycobacterium.
Infectious mononucleosis
SIGNS / SYMPTOMS
Diffuse lymphadenopathy.
INVESTIGATIONS
Positive monospot test.
Plague
SIGNS / SYMPTOMS
Unilateral lymphadenopathy.
INVESTIGATIONS
Positive culture for Yersinia pestis.
HIV infection
SIGNS / SYMPTOMS
Diffuse lymphadenopathy.
INVESTIGATIONS
HIV positive serology.
Community-acquired pneumonia
SIGNS / SYMPTOMS
No differentiating signs or symptoms.
INVESTIGATIONS
Sputum and blood cultures can diagnose some of the common causes.
Special media and urine antigen are useful for the diagnosis of legionella pneumonia.
Polymerase chain reaction, antigen detection, and culture of respiratory secretions are all useful tests for pneumonia due to viral aetiologies.
Streptococcal pharyngitis
SIGNS / SYMPTOMS
Exudative pharyngitis.
INVESTIGATIONS
Throat swab bacterial cultures and rapid test for group A streptococci (Streptococcus pyogenes) would be positive in most cases.
Conjunctivitis
SIGNS / SYMPTOMS
No differentiating signs or symptoms.
INVESTIGATIONS
Bacterial and viral causes of conjunctivitis can be cultured, and the Acanthamoeba is identified by its characteristic microscopic appearance.
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