the diagnostic capacity of three phenotypic techniques of extended-spectrum β-lactamase detection

Background: early detection of extended-spectrum β-lactamases (esbls) producing bacteria is critical for infection prevention and control. numerous phenotypic approaches and automated systems have been developed for detecting esbl bacteria. however, there is a scarcity of data in ethiopia regarding the most reliable, simple, and cost-effective methods for detecting esbl-producing bacteria. this study, therefore, aimed to evaluate the diagnostic performance of three phenotypic approaches for detecting esbl-producing bacteria. methods: in this study, 117 isolates of klebsiella pneumoniae, escherichia coli, klebsiella oxytoca, and proteus mirabilis were examined. cefotaxime (30 μg) and ceftazidime (30 μg) were used for screening esbl enzymes. a screening breakpoints of ≤ 27 mm and ≤ 22 mm were used for cefotaxime (30 μg) and ceftazidime (30 μg), respectively, as per the clinical and laboratory standards institute (clsi) guidelines. all 117 strains were further confirmed by the vitek 2 compact, double disk synergy, esbl epsilometer test, and combined disk method. the combined disk method was adopted as the reference method. results: out of 117 isolates, 90 (86%) had zone diameters of ≤ 27 mm and ≤ 22 mm for cefotaxime (30 μg) and ceftazidime (30 μg), respectively. the reference method detected 76 (65%) esbl isolates out of 117 ones. from among the three techniques (i.e., double disk synergy, vitek 2 compact, and esbl epsilometer test), the double disk synergy method demonstrated overall sensitivity and specificity of 97.4% and 97.6%, respectively. vitek-2, cefotaxime, and ceftazidime epsilometer test indicated indeterminate results of 6.8%, 6.8%, and 5.1% respectively. conclusion: double disk synergy was found to have the highest sensitivity and specificity for detecting esbl isolates with no indeterminate results.