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      News & Perspective Drugs & Diseases CME & Education Academy Video Decision Point
      Drugs & Diseases > Infectious Diseases

      Klebsiella Infections Workup

      Updated: Dec 07, 2022
      • Author: Shahab Qureshi, MD, FACP; Chief Editor: Michael Stuart Bronze, MD  more...
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      Workup

      Laboratory Studies

      A complete blood cell count usually reveals leukocytosis with a left shift, but this is not invariably present. Persistence of leukocytosis may signify empyema formation.

      Obtain a sputum sample for Gram stain. Klebsiellae appear as short, plump, gram-negative bacilli. They usually are surrounded by a capsule that appears as a clear space.

      Serology results are not useful for detection of infection with Klebsiella organisms.

      Cultures should be obtained from possible sites (eg, wounds, peripheral or central intravenous access sites, urinary catheters, respiratory support equipment).

      • Klebsiellae may be isolated from blood, urine, pleural fluid, and wounds.

      • Klebsiellae are microaerophilic and, thus, can grow in the presence of oxygen or in its absence. They have no special culture requirements. Most species can use citrate and glucose as sole carbon sources; thus, they grow well on most ordinary media.

      • Klebsiellae are lactose-fermenting, urease-positive, and indole-negative organisms, although K oxytoca and some strains of K pneumoniae are exceptions. Klebsiellae do not produce hydrogen sulfide, and they yield positive results on both Voges-Proskauer and methyl red tests.

      • Wounds may be infected with Klebsiella organisms as the sole pathogens or as a component of a multipathogenic infection. Swabs for Gram stain and culture taken from possible sites may aid in establishing the diagnosis.

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      Imaging Studies

      Chest radiography

      The organism usually involves one of the upper lobes; however, involvement of lower lobes is not uncommon.

      The affected lobe typically appears swollen, producing the bulging fissure sign. This presentation is not necessarily exclusive to Klebsiella infection. Other organisms, such as H influenzae, may produce a similar radiographic appearance.

      Cavitation, especially in the presence of a unilateral necrotizing pneumonia, strongly supports the possibility of a Klebsiella organism as the etiologic agent.

      Pleural effusion, empyema, abscess formation, and pleural adhesions occur with increased frequency in patients with Klebsiella pneumonia.

      Chest tomography

      Chest tomography may be required for patients with nonresolving or slowly responding cases of pneumonia.

      The findings from this imaging test help exclude entities that are treatable with drainage or debridement such as empyema and respiratory tract obstruction caused by K rhinoscleromatis infection.

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      Other Tests

      Susceptibility testing for ESBL-producing organisms

      The rising importance of ESBL-producing organisms has mandated effective screening methods for their detection. Use of aztreonam or ceftazidime resistance as a marker misses approximately 15-20% of ESBL-producing organisms. Resistance to cefpodoxime as a screening method, with sensitivity breakpoints of ≥2 mcg/mL by minimal inhibitory concentration or < 22 mm by disk diffusion (for a 30-mcg cefpodoxime disk), has a sensitivity of at least 98% for ESBL detection.

      Different tests that help confirm ESBL susceptibility are available. One test involves using disks that contain cefotaxime and ceftazidime alone and disks containing a combination of clavulanic acid with these antibiotics. These are placed on Mueller-Hinton agar. A positive test result is defined as a 5-mm or greater increase in the size of the zone diameter for either cefotaxime or ceftazidime tested in combination with clavulanic acid versus the zone for either antibiotic tested alone. Another method is the E-test screen, which evaluates third-generation cephalosporins with and without a beta-lactamase inhibitor. Finally, the Vitek ESBL test, which is an automated broth microdilution test, uses cefotaxime and ceftazidime alone and in combination with clavulanic acid.

      A good screening strategy might include a cefpodoxime screen followed by confirmatory disk diffusion for screen-positive isolates. The Vitek test has sensitivity of at least 99.5% and specificity of 100%. It is a reliable single-test alternative.

      The Clinical and Laboratory Standards Institute recently updated their susceptibility criteria.

      European Committee clinical breakpoints for susceptibility are available online from European Committee on Antimicrobial Susceptibility Testing (EUCAST). [12] Reduced breakpoints eliminate the need for phenotypic modified Hodge test.

      DNA microarray technology may allow rapid identification of TEM, SHV, and CTX-M ESBLs and KPC in clinical isolates. [13]

      Infection-control practices include early detection by providing screening swabs, cultures, contact precautions, patient cohorting, dedicated staffing, antimicrobial stewardship, and limited use of invasive devices (eg, urinary catheters). [14]

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      Procedures

      Diagnostic thoracocentesis may be performed if a pleural fluid pocket is large enough for aspiration.

      Bronchoalveolar lavage with fiberoptic bronchoscopy may be helpful in occasional cases in which the diagnosis cannot be made by other means and can be used to ascertain the microbial organisms involved.

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