RAPID DETECTION OF EXTENDED SPECTRUM Β ? LACTAMASES (ESBL) AND THEIR CTX-M GENETIC CHARACTERIZATION

Background: The recently described ESBL-NDP (Nordmann Dortet Poirel) test is a promising rapid and inexpensive phenotypic test used to recognize extended-spectrum-β-lactamases (ESBLs). Bla CTX-M gene is recently replacing bla SHV and bla TEM genotypes as the prevalent ESBL resistance genes and their detection may aid in infection control efforts and epidemiology of resistance. Aim: The current study aimed to detect the burden of ESBLs by the rapid ESBL-NDP test, and to examine the prevalence of CTX-M gene among Enterobacteracea in Egyptian patients. Material and Methods: One hundred forty seven Gram negative Enterobacteracea isolates were screened for ESBL production with disc diffusion method, double disc synergy test (DDST), and ESBLNDP test. All confirmed ESBL-producing isolates were screened for the blaCTX-M gene. Results: Overall, 49% of isolates were ESBL positive using the DDST while ESBL-NDP test revealed 47.6% ESBL producer. Two isolates (1.4%) gave false positive results with NDP test which indicated the presence of over expressed cephalosporinases (Amp C) with or without the presence of ESBL. The sensitivity and specificity of ESBL-NDP test were 97.2% and 100%, respectively in comparison with the DDST whereas the positive and negative predictive values of NDP test were 100% and 97.4%, respectively, with accuracy 98.6%. In our study CTX-M genotype could be identified in 83.3% of ESBL confirmed isolates. Conclusion: The NDP test is a rapid, sensitive, and cheap test that could be introduced in routine clinical practice. bla CTX-M gene was the predominant gene in ESBLs among Egyptian patients.