Table 21.

Laboratory Diagnosis of Hospital-Acquired Pneumonia and Ventilator-Associated Pneumonia (Immunocompetent Host)

Etiologic Agents	Diagnostic Procedures	Optimum Specimens	Transport Issues and Optimal Transport Time
Bacteria
Pseudomonas aeruginosa  Escherichia coli  Klebsiella pneumoniae  Enterobacter spp  Serratia marcescens  Acinetobacter spp  Stenotrophomonas maltophilia  Staphylococcus aureus and MRSA  Haemophilus influenzae	Blood culture Gram stain Quantitative or semi-quantitative aerobic and anaerobic culturea	Blood cultures Sputum Endotracheal aspirates BAL Protected specimen brush samplesa Lung tissue	Routine blood culture bottles, RT <24 h Sterile cup or tube RT, 2 h; 4°C, >2–24 h
Streptococcus pneumoniae	As above plus urine antigenb	Urine	Sterile container RT, 24 h; >24 h–14 d, 2°C–8°C
Mixed anaerobes (aspiration)	Gram stain Culturea	Protected specimen brush samplesa Lung tissue	Sterile tube with 1 mL of thioglycollate (for brush samples); Sterile container for tissue; RT, 2 h; 4°C, >2–24 h
Legionella spp	Culture on BCYE media NAATc	Induced sputum Endotracheal aspirates BAL Protected specimen brush samples Lung tissue	Sterile cup or tube RT, 2 h; 4°C, >2–24 h
	Urine antigen (L. pneumophila serogroup 1 only)	Urine	Sterile container RT, <24 h; 4°C >24 h–14 d
Fungi
Aspergillus spp	Fungal stain—KOH with calcofluor; other fungal stains Fungal culture	Endotracheal aspirates BAL Protected specimen brush samples	Sterile cup or tube RT, 2 h; 4°C, >2–24 h
	Histology	Lung tissue	Sterile cup; RT, 2 h; or formalin container, RT, 2–14 d
	Galactomannand (1–3) β-d-glucan	Serum,	Clot tube 4°C, ≤5 d; >5 d, –70°C
		BAL	Sterile cup or tube RT, 2 h; 4°C, >2–24 h
Viruses
Influenza viruses A, B  Parainfluenza viruses  Adenovirus  RSV	Rapid antigen detection DFA Viral culture methods NAATe	Nasal washes, aspirates NP swabs Endotracheal aspirates BAL Protected specimen brush samples	Transport in viral transport media, RT or 4°C, 5 d; –70°C, >5 d

Abbreviations: BAL, bronchoalveolar lavage; BCYE, buffered charcoal yeast extract; DFA, direct fluorescent antibody; KOH, potassium hydroxide; MRSA, methicillin-resistant Staphylococcus aureus; NAAT, nucleic acid amplification test; NP, nasopharyngeal; RSV, respiratory syncytial virus; RT, room temperature.

^aAnaerobic culture should only be done if the specimen has been obtained with a protected brush or catheter and transported in an anaerobic transport container or by placing the brush in 1 mL of prereduced broth prior to transport.

^bSensitivity in nonbacteremic patients with pneumococcal pneumonia is 52%–78%; sensitivity in bacteremic cases of pneumococcal pneumonia is 80%–86%; specificity in adults is >90%. However, studies have reported a 21%–54% false-positive rate in children with NP carriage and no evidence of pneumonia and adults with chronic obstructive pulmonary disease [128, 131].

^cNo US Food and Drug Administration (FDA)–cleared test is currently available. Availability is laboratory specific. Provider needs to check with the laboratory for optimal specimen source, performance characteristics, and turnaround time.

^dPerformance characteristics of these tests are reviewed in references [133, 134].

^eSeveral FDA-cleared NAAT platforms are currently available and vary in their approved specimen requirements and range of analytes detected. Readers should check with their laboratories regarding availability and performance characteristics, including certain limitations.