Pneumonia causes
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Priyamvada Singh, M.D. [2]; Alejandro Lemor, M.D. [3]
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Pneumonia Microchapters |
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Diagnosis |
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Treatment |
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Case Studies |
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Pneumonia causes On the Web |
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Overview
Pneumonia can result from a variety of causes, including infection with bacteria, viruses, fungi, parasites, and chemical or physical injury to the lungs. The etiology will depend upon various factors such as age, immune status, geographical area, and comorbidities.
Causes
Microbiological Etiology
| Typical Bacteria | Atypical Bacteria | Viruses |
|---|---|---|
Most Common Etiologies for Community-Acquired Pneumonia [1][2][3]
| Outpatient | Inpatient (non-ICU) | Inpatient (ICU) |
|---|---|---|
Causes by Pathogen
Causes by Age
| Pathogen | Neonates | Children | Adults |
|---|---|---|---|
| Bacteria |
Typical Bacteria
Atypical Bacteria | ||
| Virus |
- Newborn infants, children, and adults are at risk for different spectrums of disease causing microorganisms.
- In addition, adults with chronic illnesses, who live in certain parts of the world, who reside in nursing homes, who have recently been treated with antibiotics, or who are alcoholics are at risk for unique infections.
Infants
Source of Infection
- Aerosol
- Aspiration of amniotic fluid
- Blood-borne infection across the placenta
Newborn
- Most common cause is Streptococcus agalactiae (Group B Streptococcus)
- GBS causes at least 50% of cases of CAP in the first week of life.[4]
- Other bacterial causes in the newborn period include Listeria monocytogenes and tuberculosis
- Viral causes like herpes simplex virus (most common) adenovirus, mumps, and enterovirus
Children
- For the most part, children older than one month are at risk for the same microorganisms as adults.
- However, children less than five years are much less likely to have pneumonia caused by mycoplasma pneumoniae, chlamydophila pneumoniae, or legionella pneumophila.
- In contrast, older children and teenagers are more likely to acquire mycoplasma pneumoniae and chlamydophila pneumoniae than adults.[5]
- A unique cause of CAP in this group is chlamydia trachomatis, which is acquired during birth but does not cause pneumonia until 2-4 weeks later.
- Common viruses include respiratory syncytial virus (RSV), metapneumovirus, adenovirus, parainfluenza, influenza, and rhinovirus.
- RSV in particular is a common source of illness and hospitalization.[6]
- Fungi and parasites are not typically encountered in otherwise healthy infants, though maternally-derived syphilis can be a cause of CAP in this age group.
Adults
Viruses
- Viruses cause 20% of CAP cases.
- Common viruses are influenza, parainfluenza, respiratory syncytial virus, metapneumovirus, and adenovirus.
- Less common viruses include chicken pox, SARS, avian flu, and hantavirus.[7]
Atypical Organisms
- Mycoplasma pneumoniae, chlamydophila pneumoniae, and legionella pneumophila are often grouped as atypical pneumonia. Community acquired pneumonia caused by these agents present insidiously, with a non-productive cough and prominent extra-pulmonary complaints, such as myalgias and diarrhea (lack the typical pneumonia symptoms of fever, cough, and sputum).
- Mycoplasma pneumonia is often called is "walking pneumonia." It is transmitted via respiratory droplets and is common among healthy individuals in close contact with one another, such as dormitories or military barracks.
- Atypical organisms are more difficult to grow, respond to different antibiotics, and were discovered more recently than the typical bacteria discovered in the early twentieth century.
Streptococcus Pneumoniae
- Streptococcus pneumoniae is the most common cause of community acquired pneumonia.
- Aspiration pneumonia is most commonly caused by anaerobic organisms.
- Prior to the development of antibiotics and vaccination, it was a leading cause of death.
- Traditionally, it was highly sensitive to penicillin, but during the 1970s resistance to multiple antibiotics began to develop.
- Current strains of "drug resistant Streptococcus pneumoniae" or DRSP are common, accounting for twenty percent of all streptococcus pneumoniae infections.
- Adults with risk factors for DRSP including being older than 65, having exposure to children in day care, alcoholism, other severe underlying disease, or recent treatment with antibiotics should initially be treated with antibiotics effective against DRSP.[8]
Hemophilus Influenzae
- Another common bacterial cause of CAP.
- First discovered in 1892, it was initially believed to be the cause of influenza because it commonly causes CAP in people who have suffered recent lung damage from viral pneumonia.
Enteric Gram Negative Bacteria
- Includes E.coli and K.pneumoniae
- Adults with risk factors for infection, which include living in a nursing home, serious heart and lung disease, and recent antibiotic use should initially be treated with antibiotics effective against enteric Gram negative bacteria.
Pseudomonas Aeruginosa
- Uncommon cause of CAP, but it is a particularly difficult bacteria to treat.
- Individuals who are malnourished, have bronchiectasis, are on corticosteroids, or have recently had strong antibiotics for a week or more, should initially be treated with antibiotics effective against Pseudomonas aeruginosa.[9]
Special Situations
- Coccidioides are common in southwestern US.
- Anaerobic infection is common in alcoholics. Pneumococcal pneumonia remains the most common cause of CAP in alcoholics too.
- Psittacosis (due to Chlamydophila psittaci) should be considered in the patient with exposure to birds or bird droppings.
- Anaerobes are common in patients with poor dental hygiene, and a suspected large volume of aspiration.
- Streptococcus pneumoniae, H.influenzae, moraxella catarrhalis, and legionella species are the common causes of community acquired pneumonia in chronic obstructive pulmonary disorders and smokers.
- S. pneumoniae, gram negative bacilli, H.influenzae, staphylococcus aureus, anaerobes, and chlamydia pneumoniae are more common in nursing home residents.
- S. pneumoniae, H.influenzae, and mycobacterium tuberculosis are common pathogens in early stages of HIV, whereas, P.jiroveci, histoplasma, and cryptococcus are commonly seen in late stages HIV.
- In patients with structural lung disease such as bronchiectasis and cystic fibrosis, pseudomonas aeruginosa, Burkholderia cepacia (pseudomonas), and staphylococcus aureus are the common pathogens involved.
Aspiration Pneumonia Causes
- Incompetent swallowing mechanism, such as in neurological disease (a common cause being strokes) or while a person is intoxicated.
- Iatrogenic causes such as general anaesthesia for an operation. Patients are therefore instructed to be nil per os (NPO) for at least four hours before surgery.
- Whether aspiration pneumonia represents a true bacterial infection or a chemical inflammatory process remains the subject of significant controversy.
Drug Side Effect
- Blinatumomab
- Belimumab
- Boceprevir
- Ceritinib
- Dornase Alfa
- Enfuvirtide
- ethanolamine oleate
- Felbamate
- Iloperidone
- interferon alfacon-1
- Pegylated interferon alfa-2b
References
- ↑ Mandell LA, Wunderink RG, Anzueto A, Bartlett JG, Campbell GD, Dean NC, Dowell SF, File TM, Musher DM, Niederman MS, Torres A, Whitney CG (2007). "Infectious Diseases Society of America/American Thoracic Society consensus guidelines on the management of community-acquired pneumonia in adults". Clinical Infectious Diseases : an Official Publication of the Infectious Diseases Society of America. 44 Suppl 2: S27–72. doi:10.1086/511159. PMID 17278083. Retrieved 2012-09-06. Unknown parameter
|month=ignored (help) - ↑ Wong, KK.; Fistek, M.; Watkins, RR. (2013). "Community-acquired pneumonia caused by Yersinia enterocolitica in an immunocompetent patient". J Med Microbiol. 62 (Pt 4): 650–1. doi:10.1099/jmm.0.053488-0. PMID 23242642. Unknown parameter
|month=ignored (help) - ↑ Oh, YJ.; Song, SH.; Baik, SH.; Lee, HH.; Han, IM.; Oh, DH. (2013). "A case of fulminant community-acquired Acinetobacter baumannii pneumonia in Korea". Korean J Intern Med. 28 (4): 486–90. doi:10.3904/kjim.2013.28.4.486. PMID 23864808. Unknown parameter
|month=ignored (help) - ↑ Webber S, Wilkinson AR, Lindsell D, Hope PL, Dobson SR, Isaacs D (1990). "Neonatal pneumonia". Arch Dis Child. 65 (2): 207–11. PMC 1792235. PMID 2107797.
- ↑ Wubbel L, Muniz L, Ahmed A, Trujillo M, Carubelli C, McCoig C; et al. (1999). "Etiology and treatment of community-acquired pneumonia in ambulatory children". Pediatr Infect Dis J. 18 (2): 98–104. PMID 10048679.
- ↑ Abzug MJ, Beam AC, Gyorkos EA, Levin MJ (1990). "Viral pneumonia in the first month of life". Pediatr Infect Dis J. 9 (12): 881–5. PMID 2177540.
- ↑ de Roux A, Marcos MA, Garcia E, Mensa J, Ewig S, Lode H; et al. (2004). "Viral community-acquired pneumonia in nonimmunocompromised adults". Chest. 125 (4): 1343–51. PMID 15078744. Check
|pmid=value (help). - ↑ Ruhe JJ, Myers L, Mushatt D, Hasbun R (2004). "High-level penicillin-nonsusceptible Streptococcus pneumoniae bacteremia: identification of a low-risk subgroup". Clin Infect Dis. 38 (4): 508–14. doi:10.1086/381197. PMID 14765343.
- ↑ Lieberman D, Schlaeffer F, Boldur I, Lieberman D, Horowitz S, Friedman MG; et al. (1996). "Multiple pathogens in adult patients admitted with community-acquired pneumonia: a one year prospective study of 346 consecutive patients". Thorax. 51 (2): 179–84. PMC 473032. PMID 8711652.