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| __NOTOC__
| | #REDIRECT [[Hospital-acquired pneumonia causes#Ventilator-associated Pneumonia (VAP)]] |
| {{CMG}}; '''Associate Editor(s)-In-Chief:''' [[Priyamvada Singh|Priyamvada Singh, M.D.]] [mailto:psingh13579@gmail.com]
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| {{Ventilator-associated pneumonia}}
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| ==Causes==
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| The microbiologic [[Flora (microbiology)|flora]] responsible for VAP is different from that of the more common [[community-acquired pneumonia]] (CAP). In particular, viruses and fungi are uncommon causes in people who do not have underlying [[immunocompromise|immune deficiencies]]. Though any microorganism that causes CAP can cause VAP, there are several bacteria which are particularly important causes of VAP because of their resistance to commonly used antibiotics. These bacteria are referred to as [[multidrug resistance|multidrug resistant]] (MDR).
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| :*''[[Pseudomonas aeruginosa]]'' is the most common MDR [[Gram-negative]] bacterium causing VAP. ''Pseudomonas'' has natural resistance to many antibiotics and has been known to acquire resistance to every antibiotic except for [[polymixin B]]. Resistance is typically acquired through upregulation or mutation of a variety of efflux pumps which pump antbiotics out of the cell. Resistance may also occur through loss of an outer membrane porin channel ([[OprD]])
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| :*''[[Klebsiella pneumoniae]]'' has natural resistance to some [[Beta-lactam antibiotic|beta-lactam antibiotic]]s such as [[ampicillin]]. Resistance to [[cephalosporins]] and [[aztreonam]] may arise through [[Enzyme induction and inhibition|induction]] of a [[plasmid]]-based extended spectrum [[beta-lactamase]] (ESBL) or plasmid-based [[ampC]]-type [[enzyme]]
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| :*''[[Serratia marcescens]]'' has an ampC [[gene]] which can be induced by exposure to antibiotics such as cephalosporins. Thus, culture sensitivities may initially indicate appropriate treatment which fails due to bacterial response.
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| :*''[[Enterobacter]]'' as a group also have an inducible ampC gene. Enterobacter may also develop resistance by acquiring plasmids.
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| :*''[[Citrobacter]]'' also has an inducible ampC gene.
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| :*''[[Stenotrophomonas maltophilia]]'' often colonizes people who have [[endotracheal tube]]s or [[tracheostomy|tracheostomies]] but can also cause pneumonia. It is often resistant to a wide array of antibiotics but is usually sensitive to [[co-trimoxazole]]
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| :*''[[Acinetobacter]]'' are becoming more common and may be resistant to [[carbapenem]]s such as [[imipenem]] and [[meropenem]]
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| :*''[[Burkholderia cepacia]]'' is an important organism in people with cystic fibrosis and is often resistant to multiple antibiotics
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| :*''[[Methicillin-resistant Staphylococcus aureus]]'' is an increasing cause of VAP. As many as fifty percent of ''Staphylococcus aureus'' isolates in the intensive care setting are resistant to methicillin. Resistance is conferred by the [[mecA]] gene.
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| ==References==
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| {{reflist|2}}
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| [[Category:Diseaase]]
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| [[Category:Pulmonology]]
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| [[Category:Infectious disease]]
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| [[Category:Pneumonia|Pneumonia]]
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| [[Category:Emergency medicine]]
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| [[Category:Needs overview]]
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| [[Category:Needs causes]]
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| {{WH}}
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| {{WS}}
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