History
Klebsiellae cause various clinical syndromes. Common klebsiellae infections in humans include (1) community-acquired pneumonia, (2) UTI, (3) nosocomial infection, (4) rhinoscleroma and ozena, (5) chronic genital ulcerative disease, and (6) colonization.
Community-acquired pneumonia
Lobar pneumonia differs from other pneumonias in that it is associated with destructive changes in the lungs. It is a very severe illness with a rapid onset and often-fatal outcome despite early and appropriate antimicrobial treatment.
Patients typically present with an acute onset of high fever and chills; flulike symptoms; and productive cough with an abundant, thick, tenacious, and blood-tinged sputum sometimes called currant jelly sputum.
An increased tendency exists toward abscess formation, cavitation, empyema, and pleural adhesions.
Most pulmonary diseases caused by K pneumoniae are in the form of bronchopneumonia or bronchitis. These infections are usually hospital-acquired and have a more subtle presentation.
Urinary tract infection
Klebsiellae UTIs [10] are clinically indistinguishable from UTIs caused by other common organisms.
Clinical features include frequency, urgency, dysuria, hesitancy, low back pain, and suprapubic discomfort. Systemic symptoms such as fever and chills are usually indicative of a concomitant pyelonephritis or prostatitis.
Nosocomial infection
Important manifestations of klebsiellae infection in the hospital setting include UTI, pneumonia, bacteremia, wound infection, cholecystitis, and catheter-associated bacteriuria. The presence of invasive devices in hospitalized patients greatly increases the likelihood of infection. Patients with these infections have similar presentations to those with infections caused by other organisms.
Other nosocomial infections in which klebsiellae may also be implicated include cholangitis, meningitis, endocarditis, and bacterial endophthalmitis. The latter occurs especially in patients with liver abscesses [11] and diabetes. These infectious presentations are relatively uncommon.
Rhinoscleroma and ozena
K rhinoscleromatis and K ozaenae cause rhinoscleroma and ozena, respectively. Both are rare in the United States and are associated with upper respiratory infection.
Rhinoscleroma is a chronic granulomatous infection. Patients present with a purulent nasal discharge with crusting and nodule formation that leads to respiratory obstruction. Diagnosis is aided by histology findings and positive results from blood culture.
Ozena is a primary atrophic rhinitis that often occurs in elderly persons. Common symptoms include nasal congestion and a constant nasal bad smell. Patients also may complain of headache and symptoms attributable to chronic sinusitis. Unlike rhinoscleroma, nasal congestion is not a prominent feature.
Chronic genital ulcerative disease
K granulomatis infection can result in granuloma inguinale or donovanosis, although these are uncommon in developed temperate countries. The mode of transmission is uncertain but is believed to be sexually transmitted. The incubation period is 1-3 weeks.
Ulcerative infection is likely transmitted by contact with microabraded skin. Nonulcerative infection is probably transmitted transepithelially.
Coinfection with other sexually transmitted diseases (STDs) is common.
Klebsiella chronic genital ulcerative disease presents as a firm papule or subcutaneous nodule that later ulcerates. An ulcerogranulomatous presentation is most common and is characterized as a beefy red ulcer. A hypertrophic or verrucous presentation may mimic condylomata acuminata. A necrotic presentation is characterized by a deep ulcer. Sclerotic and cicatricial presentations are rare.
Diagnosis is based on clinical suspicion. Direct microscopy shows intracytoplasmic bipolar staining inclusion bodies (Donovan bodies).
Colonization
Differentiating nosocomial colonization from infection presents a formidable challenge in clinical practice. It is a common problem in patients with indwelling catheters.
Duration of catheterization is the most important risk factor for the development of bacteriuria. Keeping catheter systems closed and removing catheters as soon as possible are ways to prevent development of bacteriuria.
Most catheter-related UTIs are asymptomatic; the usual complaints of frequency, urgency, dysuria, hesitancy, low back pain, and suprapubic discomfort typically are absent. Therefore, demonstration of bacteriuria is necessary to make a diagnosis. A density of 100,000 colony-forming units per milliliter is usually required to make a diagnosis. Concomitant presence of pyuria is usually present in patients with catheter-associated infection as opposed to those with colonization.
In general, the presence of symptoms in conjunction with bacteriological evidence of infection helps distinguish infection, in which organisms cause disease, from colonization, in which organisms coexist without causing harm.
Physical
Klebsiella pneumonia characteristically affects one of the upper lobes of the lung, although infection of the lower lobes is not uncommon.
Examination of patients with community-acquired pneumonia usually reveals unilateral chest signs, predominantly in the upper lobes. When these signs are observed in a patient such as described in History, the diagnosis of Klebsiella pneumonia is strongly suggested.
Clinical signs observed in patients with extrapulmonary disease depend on the organ system involved. In cases of nosocomial infections, physical examination should include a search for factors that predispose the individual to the development of such infections. These should include inspection for the presence and duration of invasive devices, wounds, and burn sites.
Causes
Host factors that lead to colonization and infection include the following:
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Hospitalization (especially admission to an intensive care unit)
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Immunocompromised states (eg, diabetes, alcoholism)
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Antimicrobial therapy
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Prolonged use of invasive medical devices
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Inadequate infection control practices
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Severe illness, including major surgery
The organism gains access to the body either by direct inoculation through breached epithelial surfaces or following aspiration of oropharyngeal organisms.
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This scanning electron micrograph (SEM) reveals some of the ultrastructural morphologic features of Klebsiella pneumoniae. Courtesy of CDC/Janice Carr.
