A strain of Enterobacter aerogenes was isolated and identified by standard methods from the blood of a two-year-old male patient, admitted (8th November 1999) to a tertiary care hospital in a Southwestern city of Nigeria, with clinical diagnosis of febrile convulsion. The case note is, however, not available for the history and outcome of the patient. The strain was identified by API 20E (bioMérieux Marcy l'Etoile, France) according to the instructions provided by the manufacturer.
Disk diffusion test was performed on Mueller-Hinton agar (disks and agar media were from Oxoid, Basingstoke UK) for the phenotypic identification of ESBLs as described elsewhere [9 (link)]. Briefly, the cefotaxime (CTX; 30-μg) disk was placed 20 mm away from the amoxicillin (20-μg)-clavulanate (10-μg) (AMC) disk, the ceftazidime (CAZ; 30-μg) disk was placed at 30 mm distance, and the cefepime (FEP; 30-μg) disk was placed at 30 mm distance. For the phenotypic detection of the AmpC enzyme, a cefoxitin (FOX; 30-μg) disk was placed on the agar, as well.
The MICs of key antibiotics were determined by the broth micro-dilution test using Mueller-Hinton Broth (Oxoid, Basingstoke UK) as recommended by CLSI. End-points were interpreted after 18 h of incubation at 37°C. E. coli ATCC 25922 and E. coli DH10B were included as control strains. Powder forms of antibiotics were obtained from local companies: ampicillin (Mustafa Nevzat), piperacillin & tazobactam (Wyeth), clavulanate (DEPA), cefepime (Bristol-Myers Squibb), cefotaxime (Toprak), ceftazidime (Glaxo-SmithKline), imipenem (Merck), meropenem (Astra-Zeneca), ciprofloxacin (Bayer), gentamicin (Bilim) and tobramycin (Nobel). The final concentration of clavulanate was 4 mg L-1.
Disk diffusion test was performed on Mueller-Hinton agar (disks and agar media were from Oxoid, Basingstoke UK) for the phenotypic identification of ESBLs as described elsewhere [9 (link)]. Briefly, the cefotaxime (CTX; 30-μg) disk was placed 20 mm away from the amoxicillin (20-μg)-clavulanate (10-μg) (AMC) disk, the ceftazidime (CAZ; 30-μg) disk was placed at 30 mm distance, and the cefepime (FEP; 30-μg) disk was placed at 30 mm distance. For the phenotypic detection of the AmpC enzyme, a cefoxitin (FOX; 30-μg) disk was placed on the agar, as well.
The MICs of key antibiotics were determined by the broth micro-dilution test using Mueller-Hinton Broth (Oxoid, Basingstoke UK) as recommended by CLSI. End-points were interpreted after 18 h of incubation at 37°C. E. coli ATCC 25922 and E. coli DH10B were included as control strains. Powder forms of antibiotics were obtained from local companies: ampicillin (Mustafa Nevzat), piperacillin & tazobactam (Wyeth), clavulanate (DEPA), cefepime (Bristol-Myers Squibb), cefotaxime (Toprak), ceftazidime (Glaxo-SmithKline), imipenem (Merck), meropenem (Astra-Zeneca), ciprofloxacin (Bayer), gentamicin (Bilim) and tobramycin (Nobel). The final concentration of clavulanate was 4 mg L-1.
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