<unk>  is treated with an antibiotic that kills the infecting microorganism; treatment also aims at managing complications. If the causative microorganism is unidentified, which is often the case, the laboratory identifies the most effective antibiotic; this may take several days. Health professionals consider a person's risk factors for various organisms when choosing an initial antibiotic. Additional consideration is given to the treatment setting; most patients are cured by oral medication, while others must be hospitalized for intravenous therapy or intensive care. 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<unk> , 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<unk>  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<unk>  in children depends on the child's 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<unk>  in children. Adults In 2001 the American Thoracic Society, drawing on the work of the British and Canadian Thoracic Societies, established guidelines for the management of adult<unk>  by dividing patients into four categories based on common organisms: * Healthy outpatients without risk factors: This group (the largest) is composed of otherwise-healthy patients without risk factors for DRSP, enteric gram-negative bacteria, pseudomonas or other, less common, causes of<unk> . Primary microorganisms are viruses, atypical bacteria, penicillin-sensitive streptococcus pneumoniae and haemophilus influenzae. Recommended drugs are macrolide antibiotics, such as azithromycin or clarithromycin, for seven to ten days. A shorter course of these antibiotics has been investigated, however, there is not sufficient evidence to make recommendations. * Outpatients with underlying illness or risk factors: Although this group does not require hospitalization, they have underlying health problems such as emphysema or heart failure or are at risk for DRSP or enteric gram-negative bacteria. They may be treated with a quinolone active against streptococcus pneumoniae (such as levofloxacin) or a β-lactam antibiotic (such as cefpodoxime, cefuroxime, amoxicillin or amoxicillin/clavulanic acid) and a macrolide antibiotic, such as azithromycin or clarithromycin, for seven to ten days. * Hospitalized patients without risk for pseudomonas: This group requires intravenous antibiotics, with a quinolone active against streptococcus pneumoniae (such as levofloxacin), a β-lactam antibiotic (such as cefotaxime, ceftriaxone, ampicillin/sulbactam or high-dose ampicillin plus a macrolide antibiotic (such as azithromycin or clarithromycin) for seven to ten days. * Intensive-care patients at risk for pseudomonas aeruginosa: These patients require antibiotics targeting this difficult-to-eradicate bacterium. One regimen is an intravenous antipseudomonal beta-lactam such as cefepime, imipenem, meropenem or piperacillin/tazobactam, plus an IV antipseudomonal fluoroquinolone such as levofloxacin. Another is an IV antipseudomonal beta-lactam such as cefepime, imipenem, meropenem or piperacillin/tazobactam, plus an aminoglycoside such as gentamicin or tobramycin, plus a macrolide (such as azithromycin) or a nonpseudomonal fluoroquinolone such as ciprofloxacin. For mild-to-moderate<unk> , shorter courses of antibiotics (3–7 days) seem to be sufficient. Some patients with<unk>  will be at increased risk of death despite antimicrobial treatment. A key reason for this is the host's exaggerated inflammatory response. There is a tension between controlling the infection on one hand and minimizing damage to other tissues on the other. Some recent research focuses on immunomodulatory therapy that can modulate the immune response in order to reduce injury to the lung and other affected organs such as the heart. Although the evidence for these agents has not resulted in their routine use, their potential benefits are promising. Hospitalization Some<unk>  patients require intensive care, with clinical prediction rules such as the pneumonia severity index and CURB-65 guiding the decision whether or not to hospitalize. Factors increasing the need for hospitalization include: * Age greater than 65 * Underlying chronic illnesses * Respiratory rate greater than 30 per minute * Systolic blood pressure less than 90 mmHg * Heart rate greater than 125 per minute * Temperature below 35 or over 40 °C * Confusion * Evidence of infection outside the lung Laboratory results indicating hospitalization include: * Arterial oxygen tension less than 60 mm Hg * Carbon dioxide over 50 mmHg or pH under 7.35 while breathing room air * Hematocrit under 30 percent * Creatinine over 1.2 mg/dl or blood urea nitrogen over 20 mg/dl * White-blood-cell count under 4 × 10^9/L or over 30 × 10^9/L * Neutrophil count under 1 x 10^9/L X-ray findings indicating hospitalization include: * Involvement of more than one lobe of the lung * Presence of a cavity * Pleural effusion
Community-acquired pneumonia
Hospital-acquired pneumonia
Pneumococcal pneumonia
Bacterial pneumonia
Fungal pneumonia
Idiopathic pneumonia syndrome
Ventilator-associated pneumonia
Hantavirus pulmonary syndrome