Prevalence of Carbapenem-Resistance among Extended Spectrum Beta Lactamase-Producing E. coli at Menoufia University Hospitals: Comparison of Phenotypic and Molecular Characterization Methods

Background: Emergence and global spread of ESBLs and carbapenemase-producing E.coli isolates are of great concern especially in healthcare settings with resultant increases in the rates of morbidity and mortality. Carbapenems are the antimicrobials of last resort to treat serious infections especially in high risk patients. Unfortunately, the high incidence of carbapenemase production seriously threatens this class of life-saving drugs. Objectives: This study was carried out during the period from January to December 2016 involving a total of 172 E. coli isolates collected from the different departments of Menoufia University Hospitals (MUHs). Methodology: Antibiogram was done by the modified Kirby Bauer disk diffusion method. Phenotypic identification of ESBLs production was confirmed by the combined disk synergy test (CD-T) using ceftazidime/ceftazidime-clavulanic acid. PCR-confirmed ESBLs-producing isolates were subjected to amino-phenylboronic acid combined disk (APB-CD) and Ertapenem/EDTA combined disk tests for detection of class A and class B carbapenemases respectively. Conventional multiplex PCR was conducted for detection of ESBLs and carbapenem resistance genes (blaSHV, blaTEM, blaKPC and blaVIM). In vitro susceptibility of E.coli isolates to tigecycline was performed by disk diffusion test. Results: Out of 172 E.coli isolates, 106 (61.6%) were ESBLs-producers of which 29 (27.3%) were carbapenemase co-producers. The blaTEM gene was the most prevalent (77.4%), followed by blaSHV (22.6%).None of the isolates harbored blaTEM and blaSHV together. Co-existence of ESBLs and carbapenemase genes was detected in 27.3% of the ESBL E.coli isolates including blaTEM+blaVIM in 75.8%, blaTEM+blaKPC in 20.7% and blaSHV+blaKPC in 3.5% of E.coli isolates. Aztreonam identified most of ESBL producers, while ertapenem alone identified most of the carbapenemase producers. In relation to PCR results, the sensitivity, specificity and accuracy of the CD-T were 96%, 67% and 85% respectively. While for APB-CD and Ertapenem/EDTA combined disk test, the sensitivity, specificity and accuracy were 86%,98%, 97%,91%,94% and 93% respectively.100% and 93% of ESBLs-and combined ESBLs/carbapenemase-producing E.coli isolates were susceptible to tigecycline. Conclusion: The blaTEM-type ESBLs-producing E. coli are highly prevalent in our locality. Co-existence of blaTEM and blaVIM were also found. Adequate prevention and control of these strains is imperative. Tigecycline can be used for treatment of infection by these strains.