Nosocomial pneumonia

Nosocomial pneumonia is the second most common nosocomial infection in the U.S.

Nosocomial pneumonia is more common in intubated critical ill patients by the use nasogastric feeding tubes.

Most frequent infection among mechanically ventilated patients treatment in Intensive Care Units (ICU’s).

Ventilator associated pneumonia is the leading nosocomial infection worldwide.

 Nosocomial pneumonia, or hospital acquired pneumonia refers to any pneumonia contracted by a patient in a hospital at least 48–72 hours after being admitted. 

Nosocomial ventilator associated pneumonia affects patients who undergo invasive mechanical ventilation in ICUs with an estimated incidence from 2 to 30 episodes per 1000 days of mechanical ventilation.

The disease develops in 5 to 40% of intubated critically ill patients.

It is distinguished from community-acquired pneumonia. 

It is usually caused by a bacterial infection, rather than a virus.

Hospital acquired pneumonia is the second most common nosocomial infection, after urinary tract infections, and accounts for 15–20% of the total.

It is the most common cause of death among nosocomial infections and is the primary cause of death in intensive care units.

It is also one of the most common infections acquired at the hospital in children around the world.

Hospital acquired pneumonia typically lengthens a hospital stay by 1–2 weeks.

Findings: New or progressive infiltrate on the chest X-ray with one of the following:

Fever > 37.8 °C (100 °F)

Purulent sputum

Leukocytosis > 10,000 cells/μl

In an elderly person, the first sign of hospital-acquired pneumonia may be mental changes or confusion. 

Other symptoms include:

A cough with greenish or pus-like phlegm

Fever and chills


Loss of appetite

Nausea and vomiting

Chest pain that gets worse with deep breathing or coughing

Shortness of breath

Decreased blood pressure and fast heart rate

The majority of cases of bacterial pneumonia relate to various gram-negative organisms (52%) and Staphylococcus aureus (19%), usually, MRSA type.

Microaspirations around the tracheal tube cuff and formation of a biofilm lead to progressive bacterial spread in the tracheal bronchial tree,  ultimately leading to pneumonia.

Haemophilus spp. (5%). 

In the ICU: S. aureus (17.4%), Pseudomonas aeruginosa (17.4%), Klebsiella pneumoniae and Enterobacter spp. (18.1%), and Haemophilus influenzae (4.9%).

Viral pneumonia: influenza and respiratory syncytial virus and, in the immunocompromised host, cytomegalovirus – cause 10–20% of infections.

Ventilator-associated pneumonia (VAP) is not characterized by the causative agents, but is restricted to patients undergoing mechanical ventilation while in a hospital. 

 To appropriately categorize the causative agent or mechanism it is recommended to obtain a culture prior to initiating mechanical ventilation as a reference.

Healthcare-associated pneumonia (HCAP)  is a condition in patients who can come from the community, but have frequent contact with the healthcare environment. 

The etiology and prognosis of nursing home pneumonia have a worse prognosis and higher incidence of multi drug resistant organisms as etiology agents. 

Healthcare-associated pneumonia (HCAP) can be defined as pneumonia in a patient with at least one of the following risk factors:

hospitalization in an acute care hospital for two or more days in the last 90 days;

residence in a nursing home or long-term care facility in the last 30 days

receiving outpatient intravenous therapy like antibiotics or chemotherapy within the past 30 days

receiving home wound care within the past 30 days

attending a hospital clinic or dialysis center in the last 30 days

having a family member with known multi-drug resistant pathogens

The bacteria found in patients with healthcare acquired pneumonia were more similar to hospital acquired than to community acquired pneumonia: have higher rates of Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa, and less Streptococcus pneumoniae and Haemophilus influenzae. 

Aspiration is thought to be the most important cause of healthcare associated pneumonia. 

Dental plaque might also be a reservoir for bacteria in HCAP.

Bacteria have been the most commonly isolated pathogens, although viral and fungal pathogens are potentially found in immunocompromised hosts.

The distribution of microbial pathogens varies among institutions:, differences in patient population and local patterns of anti microbial resistance in hospitals and critical care units.

Common bacterial pathogens: aerobic GNB, such as Pseudomonas aeruginosa, Acinetobacter, Klebsiella pneumoniae, Escherichia coli as well as gram-positive organisms such as Staphylococcus aureus. 

In patients with an early onset pneumonia, within 5 days of hospitalization, they usually have anti microbial-sensitive bacteria such as Enterobacter spp, E. coli, Klebsiella spp, Proteus spp, Serratia, and community pathogens such as Streptococcus pneumoniae, Haemophilus influenzae, and methicillin-sensitive S. aureus.

Pneumonia that starts in the hospital tends to be more serious than other lung infections because,as the types of germs present in a hospital are often more dangerous and more resistant to treatment than those outside in the community. 

Pneumonia occurs more often in people who are using a respirator. 

Hospital-acquired pneumonia can also be spread by health care workers.

Patients with HCAP are more likely than those with community-acquired pneumonia to receive inappropriate antibiotics that do not target the bacteria causing their disease.

Healthcare-associated pneumonia seems to have fatality rates similar to hospital-acquired pneumonia, worse than community-acquired pneumonia but less severe than pneumonia in ventilated patients.

Healthcare-associated pneumonia prognosis is influenced by the underlying associated comorbidities and functional capacities.

 Healthcare-associated pneumonia is the second most common type of pneumonia, occurring less commonly than community-acquired pneumonia but more frequently than hospital-acquired pneumonia and ventilator-associated pneumonia. 

In a  observational study, the rates for CAP, HCAP and HAP were 60%, 25% and 15% respectively.

Patients with HCAP are older and more commonly have simultaneous health problems, such as previous stroke, heart failure and diabetes.

Residents in long-term care facilities are known to develop pneumonia 10 times more than their community-dwelling peers, and hospital admittance rates are 30 times higher.

Nursing home-acquired pneumonia is an important subgroup of healthcare associated pneumonia.

The microbes responsible for their pneumonias may be different from those traditionally seen in community-dwelling patients, requiring therapy with different antibiotics. 

Other groups of healthcare associated pneumonia include patients who are admitted as a day case for regular hemodialysis or intravenous infusions.

HCAP in the very elderly and demented patients often present with atypical symptoms.

Risk factors for contracting HAP are mechanical ventilation, old age, decreased filtration of inspired air, intrinsic respiratory, neurologic, or other disease states that result in respiratory tract obstruction, trauma, surgery, medications, diminished lung volumes, or decreased clearance of secretions may diminish the defenses of the lung, poor hand-washing and inadequate disinfection of respiratory devices cause cross-infection.

Most nosocomial respiratory infections are caused by microaspiration of upper airway secretions, through inapparent aspiration, into the lower respiratory tract. 

Macroaspirations of esophageal or gastric material is known to result in HAP. 

Either type is called aspiration pneumonia.

Differential diagnosis of nosocomial pneumonia:


Congestive heart failure

Pulmonary embolism


Usually initial therapy is empirical antibiotics.

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