Identification of ESBL strains in Hong Kong using MALDI-TOF MS-based assay

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Identification of ESBL strains in Hong Kong using MALDI-TOF MS-based assay

 

Author: Lee, Wing Yu
Title: Identification of ESBL strains in Hong Kong using MALDI-TOF MS-based assay
Degree: M.Sc.
Year: 2015
Subject: Beta lactamases.
Beta lactam antibiotics.
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Health Technology and Informatics
Pages: ix, 62 pages : color illustrations
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2829745
URI: http://theses.lib.polyu.edu.hk/handle/200/8317
Abstract: Introduction: Beta-lactam antibiotic is the largest group of antibiotics that are available in the market and because of their minimal side effect, they are frequently administrated for treating common bacterial infections caused by Gram-positive and Gram-negative bacteria and which explained a high frequency of resistance to beta-lactam antibiotics is reported. Resistance can be based on different mechanisms such as alternation influx/efflux pump, enzymatic modification or destruction of activity of antibiotic agent. Among different mechanisms, enzymatic modification is the most common mechanism that was found in many different microorganisms in against beta-lactam antibiotics. Most microorganisms share the same ability of producing a hydrolyzing enzyme, beta-lactamase, to destroy the beta-lactam ring of antibiotics. Resistance to antibiotics is a challenge that healthcare professionals confronting daily in managing severe bacterial infections and among the cases of antibiotic resistances, reports on resistance against beta-lactam antibiotics have increased dramatically in recent years. Therefore, a rapid detection of beta-lactam resistance is crucial for an appropriate antibiotic therapy and for the control of beta-lactam resistance strains spread in the community. Aims: This study is to evaluate the performance of Matrix Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry (MALDI-TOF MS) analyzer in identification of extended-spectrum beta- lactamase (ESBL) strains that are circulating in Hong Kong population, to establish a standard protocol for MALDI-TOF MS usage in medical microbiology laboratory and to expand the database with different ESBL strains isolated in Hong Kong.Methods: With the cooperation from three different public hospitals in Hong Kong, a total of 35 isolates including 22 ESBL positive strains and 13 ESBL negative strains were recovered from different specimen cultures including urine, wound, and blood culture. The clinical isolates were phenotypically confirmed with ESBL characteristics by conventional methods that include disk diffusion test and combined disk method. Identification test and detection of beta-lactamase activity were performed using MALDI-TOF MS analyzer. Multiplex PCR followed by gel electrophoresis were performed for ESBL positive isolates as to resolve the discrepancies occurred between conventional methods and MALDI-TOF MS analyzer. Results: The identification results from conventional methods and MALDI-TOF MS biotyper appeared to be exactly the same and which proven MALDI-TOF MS analyzer is capable of identify microorganism into species level in the same accuracy but in a more rapid pace. Among the 35 isolates, 94% (33/35) were identified as Escherichia coli whereas 3% (1/35) was identified as Klebsiella pneumoniae and 3% (1/35) was identified as Enterobacter cloacae from both conventional methods and MALDI-TOF MS biotyper. Among the 35 isolates, 22 ESBL positive strains and 13 ESBL negative strains were identified from the conventional methods whereas 20 ESBL positive strains and 15 ESBL negative strains were identified from MALDI-TOF MS analyzer. The data showed that MALDI-TOF MS-based assay have successfully achieved 90.9 % sensitivity and 100% specificity in the detection of beta-lactamase activity. In addition, results from the molecular test in this study showed CTX-M group 9 was the dominant gene found in most ESBL positives isolates and that indicated that the most common ESBL isolates circulating in our community are belonged to CTX-M group 9 which corresponded to other studies previously performed in Hong Kong.Conclusion: This is a first study performed in Hong Kong in comparing the conventional method with MALDI-TOF MS-based assay in identifying ESBL strains that are circulating in the community and the results supported MALDI-TOF MS-based assay provides a rapid detection of ESBLs with an optimal accuracy when compared to conventional methods.

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