INTRODUCTION	Section 2 of 10
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Background: Nursing home–acquired pneumonia (NHAP) is defined as pneumonia occurring in a resident of a chronic care facility or nursing home. NHAP is one of the most common infectious disease problems in chronic care facilities. NHAP also is a significant cause of mortality and morbidity among residents of nursing homes or chronic care facilities. NHAP more closely resembles community-acquired pneumonia (CAP) than nosocomial pneumonia (NP).

NP occurs when the pathogen is distributed in a hospital setting, resulting in a subsequent infection. Aerobic gram-negative bacilli, including Pseudomonas aeruginosa, cause NPs. Staphylococcus aureus (eg, methicillin-susceptible S aureus [MSSA] and methicillin-resistant S aureus [MRSA]) infection is not a significant cause of CAP, NP, or NHAP. The presence of P aeruginosa and other aerobic gram-negative bacilli defines the NP group. Because NHAP is caused by CAP-associated pathogens and not NP-associated pathogens, NHAP is considered diagnostically and therapeutically synonymous to CAP. Patients with NHAP have the same length of hospital stay as patients with CAP. Physicians, therefore, approach the treatment strategy for NHAP and CAP in a similar way and with similar empiric antibiotic coverage.

Table 1. Comparison of Characteristics of Nursing Home–Acquired Pneumonia, Community-Acquired Pneumonia, and Nosocomial Pneumonia

Type of Pneumonia	Most Common Pathogens	Uncommon Pathogens	Appearance on Chest Radiograph	Length of Stay
NHAP	Streptococcus pneumoniae Haemophilus influenzae Moraxella catarrhalis	Legionella Chlamydia pneumoniae	Focal sequential/lobar ± consolidation ± pleural effusion No cavitation	7-10 days
CAP	S pneumoniae H influenzae M catarrhalis	Legionella Mycoplasma	Focal sequential/lobar ± consolidation ± pleural effusion No cavitation	7-10 days
NP	P aeruginosa Klebsiella Escherichia coli	Serratia	Necrotizing pneumonia and cavitation withP aeruginosa and Klebsiella Bilateral infiltrates without cavitation or pleural effusion	10-21 days

Pathophysiology: The pathophysiology of NHAP is the same as the pathophysiology of CAP. NHAP may result when a patient aspirates oropharyngeal contents into one or more lung segments or lobes. NHAP also may occur if a distant focus of infection hematogenously disseminates to the lungs.

Aspiration pneumonia, whether community-acquired or acquired in a nursing home, results microbiologically from aspirated anaerobic oropharyngeal flora. Hundreds of species of oropharyngeal anaerobes may be cultured from patients with aspiration pneumonia. However, oropharyngeal anaerobes are not like Bacteroides fragilis, which is the primary anaerobe below the diaphragm and is sensitive to nearly all antibiotics. Patients with CAP or NHAP do not require specific anti–B fragilis coverage. In aspiration pneumonia, the location of the lung lesion is related to the position of the patient at the time of aspiration. Because most patients are supine when they aspirate, most lung infiltrates observed on chest radiographs and most aspiration pneumonia occur in segments of the right lung.

If aspiration occurs when patients are lying on their right side, the pulmonary infiltrates most likely involve the right upper lobe. If patients are lying on their left side, the most likely location of the infiltrates is the left upper lobe. If patients are supine and the aspiration is massive, bilateral infiltrates involving multiple lung segments or lobes are possible and may produce a radiologic appearance indistinguishable from left ventricular failure or acute respiratory distress syndrome.

Table 2. Radiographic Patterns in Aspiration Pneumonia

Patient Position at Aspiration	Chest Radiograph Lobar Involvement
Supine	Right lower lobe (ie, superior or posterior segment) or bilateral infiltrates (ie, all lobes)
Right side down	Right upper lobe (ie, axillary segment)
Left side down	Left upper lobe (ie, axillary segment)
Prone	Right middle lobe (ie, lingula)
Sitting upright	Right lower lobe (ie, basilar segments)

Hematogenously acquired pneumonia is not common among patients with CAP or NHAP. Hematogenously acquired pneumonia presents with bilateral symmetrical perihilar infiltrates, as opposed to the localized segmental or lobar distribution characteristic of pneumonia acquired via primary inhalation.

The degree of impaired lung function resulting from NHAP depends on the extent of aspiration and the patient's preexisting physiologic and anatomic lung function. The histologic changes in lung parenchyma resulting from NHAP are the same as those observed resulting from CAP (ie, no cavitation, necrosis, or blood vessel invasion). As with CAP, resolving NHAP restores the lung function that existed prior to acquiring pneumonia.

Frequency:

• In the US: NHAP is one of the most common causes of infection in chronic care facilities and is one the most significant infection-related causes of mortality and morbidity in chronic care facilities.

• Internationally: NHAP is a common cause of infection in chronic care facilities.

Mortality/Morbidity:

• NHAP is one of the most important infection-related causes of mortality and morbidity in chronic care facilities.

Race:

• No race predilection exists.

Sex:

• No sex predilection exists.

Age:

• By definition, most patients in chronic care facilities and nursing homes are elderly; therefore, NHAP is a disease that primarily afflicts elderly individuals.

• NHAP is less common in chronic care or rehabilitation facilities that have smaller populations of elderly individuals.

	CLINICAL	Section 3 of 10
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History:

• Patients may complain of fever, cough, chest pain, or rapid respiration.

• Patients with chronic bronchitis are particularly prone to developing pneumonias.

• Patients with aspiration NHAP often have a history of CNS or esophageal disease, or they have a decreased gag reflex that predisposes them to recurrent aspiration.

Physical:

• Most, but not all, patients are febrile. Fever, when present, may be high-grade or low-grade.

• Physical findings in the chest include rales over the involved lung segments with or without signs of consolidation or pleural effusion.

Causes:

• The most common pathogens that cause NHAP and CAP are S pneumoniae, H influenzae, and M catarrhalis.

• Atypical organisms that cause NHAP are Mycoplasma pneumoniae, Legionella (primarily in chronic care facilities), and C pneumoniae (primarily in elderly residents of nursing homes).

• Overview of NHAP

• NHAP is a common diagnosis applied upon admission but is the definitive diagnosis in only 33% of patients.

• Many physicians perform a suboptimal workup for NHAP, omitting sputum Gram stains and culture studies. Blood cultures usually are negative.

• The distribution of pathogens observed in NHAP more closely resembles CAP than NP.

• Clinically, NHAP differs from NP in that NHAP is not associated with P aeruginosa, it does not produce cavitation on chest radiographs, and patients generally have a shorter hospital stay. The duration of the hospital stay for a patient with NHAP is the same as for a patient with CAP.

• The medical conditions most frequently misdiagnosed as NHAP are congestive heart failure (CHF) and chronic obstructive pulmonary disease.

• Chest radiograph findings in NHAP are useful to rule out CHF. Unilateral segmental or lobar infiltrates are the most common roentgenographic findings in NHAP, as they are in CAP.

• Fever and leukocytosis are more common in patients with NHAP than in patients with noninfectious mimics of NHAP, but these findings are nonspecific.

• Noninfectious infiltrates observed on chest radiographs frequently are misdiagnosed as NHAP.

• Treat NHAP empirically, using the same antibiotics as with CAP, but not as with NP.