Microbiology

The especially challenging task is to distinguish viral from bacterial sinusitis (1)

• in most patients, rhinoviral illness improves in 7 to 10 days therefore, a diagnosis of acute bacterial sinusitis requires the persistence of symptoms for longer than 10 days or a worsening of symptoms after 5 to 7 days
• symptoms of viral sinusitis, including fever, mimic those of bacterial sinusitis, although the colour and quality of nasal discharge — classically, clear and thin during viral sinusitis and yellow-green and thick during bacterial sinusitis — may help to differentiate the two

With respect to bacterial sinusitis, the organisms usually implicated are (1):

• Streptococcus pneumoniae and Haemophilus influenzae are the major bacterial pathogens in adults with sinusitis
• other species (including β-haemolytic and α-haemolytic streptococci, Staphylococcus aureus, and anaerobes) have also been cultured from adults with sinusitis but are much less frequent

Acute frontal sinusitis is most commonly preceded by a viral upper respiratory tract infection (2)

• with respect to viral upper respiratory tract infection, human rhinovirus is implicated in 50 % of cases, but other viruses may include coronavirus, influenza, parainfluenza, respiratory syncytial virus, adenovirus, and enterovirus
• the primary predisposing factor for acute rhinosinusitis (ARS) is an antecedent upper respiratory viral infection
  • approximately 0.5–2 % of viral upper respiratory tract infections are complicated by acute bacterial infection

Reference:

• (1) Piccirillo JF. Acute Bacterial Sinusitis. N Engl J Med 2004;351:902
• (2) Soudry E, Hwang PH. Acute Frontal Sinusitis. The Frontal Sinus. 2016 Aug 6:63–76.