Phenotypic methods for detection of Beta Lactam resistance in Klebsiella pneumoniae

Abstract

Background:Drug-resistant isolates remain an important hospital-acquired bacterial pathogen, add significantly to hospital stays and especially problematic in high-impact medical areas such as intensive care units. Klebsiella pneumoniae is the most common cause of nosocomial respiratory tract, and the second-most frequent cause of Gramnegative bacteraemia and urinary tract infections. It is essential to detect the beta lactam resistance in K. pneumoniae for proper antibiotic therapy and to limit the spread the infection. Objectives: The study was designed to review the rates of extended-spectrum β-lactamases (ESBL), metallo beta lactamases (MBL) and Ampicillin resistance gene group C (AmpC) beta lactamases production among K. pneumoniae isolates and to assess the best phenotypic method for detection of the resistance. Methodology: This study included 200 isolates obtained from patients admitted to different Departments in Assiut University Hospital. Screening and phenotypic confirmatory tests for resistance were done. Results: The Percentages of B -Lactamase enzymes producers from 50 isolates of K. pneumoniae were11 (22%) isolates not resistant; 6 (12%) by screening with antibiotic sensitivity tests and 5(10%) by the gold standard phenotypic tests. The remaining 39of 50 isolates (78%) were resistant and distributed as follow; Ten strains (20%) were ESBL alone, 2 (4%) were ESBL and AmpC, 4(8%) were ESBL and Carbapenemases, 13(26%) were AmpC producers alone and 10 (20%) were Carbapenemases producers alone. The combined disk test showed high sensitivity and specificity for detection of ESBL and MBL, For AmpC detection; the disk approximation test showed higher sensitivity and specificity than boronic acid. Conclusion: The rate of Beta lactamases production by K.pneumoniae is seriously increased, the most common type of beta lactamases in K.pneumoniae was the ESBL32% then AmpC30 %and lastly the Metallo beta lactamase (MBL) 28%. The phenotypic confirmatory tests showed high sensitivity and specificity and proved to be reliable methods for detection ofthe beta lactamase resistance, genotypic tests are recommended to be a gold standard tests to increase the specificity of the phenotypic tests.