Klebsiella Pneumonia

Steven J. Escobar

Klebsiella pneumoniae is a common nosocomial Gram-negative pathogen that has become an increasingly global concern due to its carbapenemase activity. Community-acquired pneumonia due to K. pneumoniae is rare in the United States and Europe but has been reported to be the second leading cause of severe pneumonia (following Streptococcus pneumonia) requiring hospitalization in Asia. A community-acquired K. pneumoniae primary bacteremic liver abscess syndrome with meningitis and/or endophthalmitis also has been described in Asia.

Klebsiella species are lactose-fermenting Gram-negative bacteria belonging to the Entero-bacteriaceae family. K. pneumoniae has a very large polysaccharide capsule with antiphagocytic property, which contributes to its virulence. Encapsulated K. pneumoniae strains have a mucoid appearance in culture plates, and Gram stain demonstrates bipolar Gram positivity, as seen in other enteric organisms. K. pneumoniae may be suspected on Gram stain if there are clear zones around apparently Gram-negative bacteria.

K. pneumoniae carbapenemase (KPC) was first described from an isolate in North Carolina in 1996 and was infrequently isolated prior to several outbreaks in New York and New Jersey in 2001. KPC has now been reported in 42 states of the United States, Europe, South America, Middle East, and Asia. The rapid global spread has been attributed to international travel, patient-to-patient transmission, and interspecies transfer of KPC-producing organisms. KPC is an Ambler class A carbapenemase that through hydrolysis confers decreased susceptibility or resistance to virtually all β-lactams, including carbapenem. The transferable plasmid encoding KPC frequently contains genes encoding amnioglycoside, extended-spectrum β-lactamase (ESBL), and flouroquinolone resistance. These plasmids may be horizontally transmitted to other enterobacteriaceae and have been reported in Pseudomonas aeruginosa and Acinetobacter baumannii.

K. pneumoniae is a saprophyte which colonizes the gastrointestinal tract, nasopharynx, and, rarely, the skin. K. pneumoniae may be found in 5% to 38% of stool samples and has a 1% to 6% nasopharyngeal carrier rate among normal hosts in the community. However, the nasopha-ryngeal colonization rate has been found to be as high as 30% in ambulatory alcoholics. The carrier rate increases in the hospital environment in direct proportion to the length of stay, prior antibiotic use, comorbidities and invasive lines and tubes. In hospitalized patients, the gastrointestinal, nasopharyngeal, and skin carrier rates have been reported to be as high as 77%, 19%, and 42% respectively.

The classic presentation of community-acquired K. pneumoniae pneumonia (Friedlander pneumonia) is rare and consists of acute onset prostration, pleuritic chest pain, dyspnea, high fever, and productive cough with “currant jelly” (thick, bloody-appearing and mucoid-viscid) sputum. Physical examination discloses tachypnea and signs of lung consolidation. The posterior segment of the right upper lobe is the most often affected area of the lung. Patients may present with sepsis or septic shock, and blood cultures are positive in 25% of cases. Leukocyte counts can be high, normal, or low. Neutropenia indicates a worse prognosis. Respiratory distress or failure requiring endotracheal intubation and mechanical ventilation upon presentation is common. Lung abscess, cavitation, and pulmonary gangrene (a large cavity containing fragments of necrotic lung) may complicate the course of illness. Pleural effusion and empyema also are common. After recovery, unclosed cavities, residual fibrosis, and reduced lung volumes may be detected.

The presentation of hospital-acquired K. pneumoniae

Only gold members can continue reading. Log In or Register to continue