Detection of extended-spectrum β-lactamases in Klebsiella pneumoniae: comparison of phenotypic characterization methods

OBJECTIVE Extended-spectrum β-lactamase producing K. pneumoniae is a serious threat to the patients. This manuscript shows the comparison of phenotypic characterization methods used for ESBL K. pneumoniae and frequency distribution of these isolates in various clinical samples. METHODOLOGY Eleven different types of pathological samples collected on various time intervals were analyzed. K. pneumoniae were identified with API 20E system (bioMerieux) and initial screening of ESBL K. pneumoniae was performed using the ceftazidime antimicrobial disc. Double-disc synergy test (DDST) and CLSI confirmatory test were compared for the phenotypic detection of ESBL K. pneumoniae. RESULTS A total number of 214 ESBL producing K. pneumoniae were isolated from various clinical samples. Frequency distribution of ESBL producing K. pneumoniae was found to be highest among blood 117 (54.7%) and urine 46 (21.5%) samples. Data regarding the use of various interventions among these patients showed most common presence of intravenous line 209 (97.7%) and urinary catheters 46 (21.5%). Comparison of DDST and CLSI confirmatory test showed that the DDST detected 145 (67.8%) isolates while 213 (99.5%) ESBL K. pneumoniae were characterized by CLSI confirmatory test. CONCLUSION The use of CLSI confirmatory test is very efficient in the early detection of ESBL K. pneumoniae especially when the facilities for molecular characterization are not available.