<P> Streptococcus pneumoniae (J13) is the most common bacterial cause of pneumonia in all age groups except newborn infants . Streptococcus pneumoniae is a Gram - positive bacterium that often lives in the throat of people who do not have pneumonia . </P> <P> Other important Gram - positive causes of pneumonia are Staphylococcus aureus (J15. 2) and Bacillus anthracis . </P> <P> Gram - negative bacteria are seen less frequently: Haemophilus influenzae (J14), Klebsiella pneumoniae (J15. 0), Escherichia coli (J15. 5), Pseudomonas aeruginosa (J15. 1), Bordetella pertussis, and Moraxella catarrhalis are the most common . </P> <P> These bacteria often live in the gut and enter the lungs when contents of the gut (such as vomit or faeces) are inhaled . </P>

Which of the following is the most common type of bacterial pneumonia