chemical formula a combination of symbols used to express the chemical components of a substance. empirical formula a chemical formula that expresses the proportions of the elements present in a substance.
The bacteria streptococcus pneumoniae is the most common cause of acute bacterial sinusitis. This type of bacteria can be resistant to the most common types of antibiotics at standard dosages, although there are other antibiotics that can be used to treat the condition.
Usually, sinus infections are caused by viruses, like a cold virus. But if the sinuses have been blocked for too long, bacteria can invade, causing a secondary infection. Having multiple sinus infections can lead to chronic (long-term) sinusitis.