Relationship between isolation of extended spectrum beta-lactamase-producing Klebsiella pneumoniae and course of hospital-acquired pneumonia

Aim of the study. To evaluate relationship between isolation of extended spectrum beta-lactamaseproducing Klebsiella pneumoniae strains and course of hospital-acquired pneumonia.
Materials and methods. K. pneumoniae strains isolated from bronchial secretions or bronchoalveolar lavage fluid samples of patients hospitalized at an intensive care unit of Kaunas University of Medicine Hospital were analyzed. By means of synergistic two-antibiotics disc method, K. pneumoniae strains producing extended spectrum beta-lactamases were selected for further analysis using E-test (AB Biodisk, Solna, Sweden). Hospitalacquired pneumonia was diagnosed based on standard criteria for the diagnosis of pneumonia if signs of pneumonia occurred after 48 hours following admission. Late-onset hospital-acquired pneumonia was considered if these signs of pneumonia occurred on fifth day of hospitalization or later.
Results. Total of 45 strains of K. pneumoniae were isolated during the study period; 18 isolated strains produced ESBL. Thirty-two patients investigated have developed hospital-acquired pneumonia, 20 of which were cases of late-onset hospital-acquired pneumonia. Thirteen cases of K. pneumoniae isolation were classified as airway colonization. Extended spectrum beta-lactamase-producing K. pneumoniae strains were more frequently isolated from patients with hospital-acquired pneumonia (88.9%, n=16 and 11.1%, n=2, P<0.05) in comparison with non-producing strains. Extended spectrum beta-lactamase-producing strains were more prevalent in late-onset pneumonia group (93.8%, n=15) than in early-onset group (6.2%, n=1, P<0.001).
Conclusions. Extended spectrum beta-lactamase-producing K. pneumoniae strains were more frequently isolated from patients with hospital-acquired pneumonia as compared to colonized patients. Extended spectrum beta-lactamase-producing K. pneumoniae strains were more frequently isolated from patients with late-onset hospital-acquired pneumonia.