A 27-year-old male accident victim with a head injury is admitted to the ICU and kept on mechanical ventilatory support. On the seventh day after admission, he is clinically diagnosed with pneumonia. Blood samples and lower respiratory secretions are submitted to the laboratory for culture; empiric antimicrobial therapy is started.
Question
What is the most likely etiologic agent of pneumonia in this patient?
1 Streptococcus pneumoniae
2 Klebsiella pneumoniae
3 Mycoplasma pneumoniae
4 Moraxella catarrhalis
5 Haemophilus influenzae