Bacteria are the most common
infectious agents in sinusitis. The bacteria most commonly implicated
in sinusitis are the following:
(also called pneumococcal pneumonia or pneumococci). This bacterium
is found in between 20% and 43% of adults and children with sinusitis.
H. influenzae (a common
bacteria associated with many upper respiratory infections). This
bacterium colonizes nearly half of all children by age two, and
it causes about 25% of sinusitis cases in this group. Studies have
reported the presence of this bacterium in 22% to 35% of adult sinusitis
Over three-quarters of all children harbor this bacterium and it
causes about 25% of sinusitis cases.
(6% of adult cases).
Fungi are uncommon causes
of sinusitis, but the incidence of these infections is increasing.
Funguses involved in sinusitis are the following:
The fungus Aspergillus
is the most common cause of all forms of fungal sinusitis.
Others include Curvularia,
Bipolaris, Exserohilum, and Mucormycosis.
There have been a few
reports of fungal sinusitis caused by Metarrhizium anisopliae ,
which is used in biological insect control.
There are four categories
of fungal sinusitis:
Acute or invasive
fungal sinusitis. This infection is most likely to affect
people with diabetes and compromised immune systems.
Chronic or indolent
fungal sinusitis. This form is generally found outside the
US, most commonly in the Sudan and northern India.
Fungus ball (mycetoma).
This fungal sinusitis is noninvasive and occurs usually in one
sinus, most often the maxillary sinus.
sinusitis. This form typically occurs because of an allergy
to the fungus Aspergillus (rather than being caused by the fungus
itself). In such cases, a peanut butter-like fungal growth occurs
in the sinus cavities that may cause nasal passage obstruction
and the erosion of the bones.
Fungal infections can
be very serious, and both chronic and acute fungal sinusitis require
immediate treatment. Fungal ball is not invasive and is nearly always
Fungal infections should
be suspected in people with sinusitis who also have diabetes, leukemia,
AIDS, or other conditions that impair the immune system. Fungal
infections can also occur in patients with healthy immune systems
but they are far less common.
Viral Sinusitis. Viruses
are directly implicated in only about 10% of sinusitis cases.
in Chronic Sinusitis
The same organisms that cause acute sinusitis are often present
in chronic sinusitis, but other agents are often detected in chronic
cases that are not present in the original acute condition:
About 20% of chronic
sinusitis cases are caused by Staphylococcus aureus (commonly called
Staph infection). This bacteria may be present but is not usually
the infecting agent in acute sinusitis.
Along with other bacteria,
certain anaerobic bacteria, particularly the species Peptostreptococcus,
Fusobacterium, and Prevotella, are found in 88% of cultures in chronic
sinusitis cases. (Anaerobic bacteria exist without air.)
Fungi are the cause
of about 6% to 8% of chronic sinusitis cases.It should also be noted
that sometimes bacteria or other organisms do not appear to be directly
involved with chronic sinusitis.