Pseudomonas aeruginosa, an uncommon cause of CAP, is a difficult bacteria to treat. Bacteria and fungi typically enter the lungs by inhalation of water droplets, although they can reach the lung through the bloodstream if an infection is present. In the alveoli, bacteria and fungi travel into the spaces between cells and adjacent alveoli through connecting pores. The immune system responds by releasing neutrophil granulocytes, white blood cells responsible for attacking microorganisms, into the lungs. The neutrophils engulf and kill the microorganisms, releasing cytokines which activate the entire immune system. This response causes fever, chills and fatigue, common symptoms of CAP. The neutrophils, bacteria and fluids leaked from surrounding blood vessels fill the alveoli, impairing oxygen transport. Bacteria may travel from the lung to the bloodstream, causing septic shock (very low blood pressure which damages the brain, kidney, and heart). Parasites
A variety of parasites can affect the lungs, generally entering the body through the skin or by being swallowed. They then travel to the lungs through the blood, where the combination of cell destruction and immune response disrupts oxygen transport. Diagnosis
Patients with symptoms of CAP require evaluation. Diagnosis of pneumonia is made clinically, rather than on the basis of a particular test. Evaluation begins with a physical examination by a health provider, which may reveal fever, an increased respiratory rate (tachypnea), low blood pressure (hypotension), a fast heart rate (tachycardia) and changes in the amount of oxygen in the blood.
Current treatment guidelines recommend a beta lactam, like amoxicillin and a macrolide, like azithromycin or clarithromycin, or a quinolone, such as levofloxacin. Doxycycline is the antibiotic of choice in the UK for atypical bacteria, due to increased clostridium difficile colitis in hospital patients linked to the increased use of clarithromycin. Ceftriaxone and azithromycin are often used to treat community acquired pneumonia, which usually present with a few days of cough, fever, and shortness of breath. Chest x-ray typically reveals a lobar infiltrate (rather than diffuse). Newborns
Most newborn infants with CAP are hospitalized, receiving IV ampicillin and gentamicin for at least ten days to treat the common causative agents streptococcus agalactiae, listeria monocytogenes and escherichia coli. To treat the herpes simplex virus, IV acyclovir is administered for 21 days. Children
Treatment of CAP in children depends on the childs age and the severity of illness. Children under five are not usually treated for atypical bacteria. If hospitalization is not required, a seven-day course of amoxicillin is often prescribed, with co-trimaxazole as an alternative when there is allergy to penicillins. Further studies are needed to confirm the efficacy of newer antibiotics. With the increase in drug-resistant Streptococcus pneumoniae, antibiotics such as cefpodoxime may become more popular. Hospitalized children receive intravenous ampicillin, ceftriaxone or cefotaxime, and a recent study found that a three-day course of antibiotics seems sufficient for most mild-to-moderate CAP in children.