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Escherichia
Published in Dongyou Liu, Laboratory Models for Foodborne Infections, 2017
E. coli grown on EMB agar produces black colonies with a diagnostic greenish-black metallic sheen. In addition, being lactose positive, E. coli generates deep red colonies on MacConkey agar, as fermentation of lactose decreases the medium’s pH and darkens the medium. Other biochemical features of E. coli include the ability to reduce nitrates to nitrites and to generate succinate, ethanol, acetate, and carbon dioxide. While most E. coli strains are positive for catalase, they are negative for oxidase, citrate, urease, and hydrogen sulfide. Further, E. coli is positive for indole production and the methyl red test. Given that about 98% of E. coli strains are positive in the indole test, it offers a useful approach to differentiate E. coli from other members of the family Enterobacteriaceae.
Molecular characterization and distribution of cephalosporin resistance determinants in Escherichia coli and Klebsiella pneumoniae isolated from patients attending Kampala International University Teaching Hospital in Bushenyi, Western Uganda
Published in Alexandria Journal of Medicine, 2021
Herbert Mbyemeire, Kenneth Ssekatawa, Charles D. Kato, Eddie M. Wampande
E. coli and K. pneumoniae identity was confirmed using biochemical tests as previously described. Triple sugar iron test that detects glucose, lactose, and sucrose fermenters [13,14], indole test [14] and citrate utilization test [13]), urease test [14]), and methyl red and Voges Proskaue tests [14] were conducted. The susceptibility tests were performed using the disc diffusion method according to the standard guidelines [15]. The isolates were subjected to antibiotic susceptibility test on Muller–Hinton agar using Ampicillin 25 µg; amoxicillin/clavulanic acid 20/10 µg; ceftazidime 30 µg; cefuroxime (CXM) 30 μg; temocillin (TEM) (30 μg); piperacillin-tazobactum (TPZ) 110 μg; cefoxitin (FOX) 30 μg; ceftizoxime (CTX) 30 μg; ceftazidime (CAZ) 30 μg; ceftriaxone (CRO) 30 μg; and cefixime (CFM) 30 μg. K. pneumoniae American Type Culture Collection (ATCC) 700603 and E. coli ATCC 25922 were used as positive and negative controls, respectively [16,17].