Infection and Drug Resistance (Jun 2020)
Distribution of Class B and Class A β-Lactamases in Clinical Strains of Pseudomonas aeruginosa: Comparison of Phenotypic Methods and High-Resolution Melting Analysis (HRMA) Assay
Abstract
Sanaz Dehbashi,1 Hamed Tahmasebi,2 Mohammad Yousef Alikhani,1 Fariba Keramat,3 Mohammad Reza Arabestani1,4 1Microbiology Department, Faculty of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran; 2Microbiology Department, Faculty of Medicine, Zahedan University of Medical Sciences, Zahedan, Iran; 3Brucellosis Research Center, Faculty of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran; 4Nutrition Health Research Center, Hamadan University of Medical Sciences, Hamadan, IranCorrespondence: Mohammad Reza ArabestaniDepartment of Microbiology, Faculty of Medicine, Hamadan University of Medical Sciences, Hamadan, IranTel +989 188662009Email [email protected]: There are various phenotypic methods for identifying class B and class A β-lactamase enzymes in Pseudomonas aeruginosa. The purpose of this study was to compare the sensitivity and specificity of different phenotypic methods with HRMA assay to detect β-lactamase-producing P. aeruginosa strains.Methods: Eighty-eight of P. aeruginosa isolates were collected from different specimens. Conventional double-disk test (DDT) and EDTA-imipenem microbiological (EIM) were performed to detect ESBL and MBL-producing strains, respectively. Meanwhile, the Modified Hodge test and Carba-NP test were performed on all carbapenem-resistant strains. HRMA method and sensitivity and specificity of primers were determined based on the melt curve temperature range. In all comparisons, PCR was considered as the gold standard.Results: Of the 402 isolates collected from different clinical specimens, 88 isolates of P. aeruginosa were identified. However, 43 strains were (48.88%) ESBL-producing, and 7 strains (7.95%) were MBL-producing. Also, using the Modified Hodge test and Carba-NP method, 11 (12.5%) and 19 (21.59%) strains were carbapenemase-producing, respectively. The results of the HRMA test revealed that genes coding for blaSHV, blaTEM, blaKPC, blaIMP, blaVIM, and blaGES were detected in 44.31%, 22.72%, 13.63%, 14.7%, 5.6%, and 2.27% of P. aeruginosa isolates. Nonetheless, for blaKPC and blaGES genes, sensitivity and specificity of the Carba-NP test were 90.47%, 94.87%, and 83.36%, 94.80%, respectively. However, sensitivity and specificity of MHT was 91.66%, 98.70%, and 77.77%, 96.42%, respectively. For blaSHV and blaTEM genes, sensitivity and specificity of DDT were 95.55%, 95.55%, and 86%, 83.50%, respectively. However, sensitivity and specificity of EMI were 77.77%, 97.59%, and 91.66%, 97.43% for blaVIM and blaIMP, respectively.Conclusion: The HRMA is a powerful, accurate, closed-tube, rapid method for detecting β-lactamase genes in P. aeruginosa. The high sensitivity and specificity of this method, along with phenotypic tests, play a useful role in increasing the predictive value of clinical reports.Keywords: Pseudomonas aeruginosa, high-resolution melting curve analysis, HRMA, β-lactamases, drug resistance
