| Summary: | Background: Antimicrobial resistance (AMR) among Gram-negative pathogens, predominantly ESBL-producing clinical isolates, are increasing worldwide. The main aim of this study was to determine the prevalence of ESBL-producing clinical isolates, their antibiogram, and the frequency of ESBL genes (<i>bla</i><sub>TEM</sub> and <i>bla</i><sub>CTX-M</sub>) in the clinical samples from patients. Methods: A total of 1065 clinical specimens from patients suspected of heart infections were collected between February and August 2019. Bacterial isolates were identified on colony morphology and biochemical properties. Thus, obtained clinical isolates were screened for antimicrobial susceptibility testing (AST) using modified Kirby–Bauer disk diffusion method, while ESBL producers were identified by using a combination disk diffusion method. ESBL positive isolates were further assessed using conventional polymerase chain reaction (PCR) to detect the ESBL genes <i>bla</i><sub>TEM</sub> and <i>bla</i><sub>CTX-M</sub>. Results: Out of 1065 clinical specimens, 17.8% (190/1065) showed bacterial growth. Among 190 bacterial isolates, 57.4% (109/190) were Gram-negative bacteria. Among 109 Gram-negative bacteria, 40.3% (44/109) were <i>E. coli</i>, and 30.2% (33/109) were <i>K. pneumoniae</i>. In AST, 57.7% (<i>n</i> = 63) Gram-negative bacterial isolates were resistant to ampicillin and 47.7% (<i>n</i> = 52) were resistant to nalidixic acid. Over half of the isolates (51.3%; 56/109) were multidrug resistant (MDR). Of 44 <i>E. coli</i>, 27.3% (12/44) were ESBL producers. Among ESBL producer <i>E. coli</i> isolates, 58.4% (7/12) tested positive for the <i>bla</i><sub>CTX-M</sub> gene and 41.6% (5/12) tested positive for the <i>bla</i><sub>TEM</sub> gene. Conclusion: Half of the Gram-negative bacteria in our study were MDR. Routine identification of an infectious agent followed by AST is critical to optimize the treatment and prevent antimicrobial resistance.
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