Numerical evaluation of minimal biochemical test combinations for the identification of Enterobacteriaceae species

Abstract

Species identification of 572 clinical isolates of Enterobacteriaceae was determined using an in-house biochemical test panel and API 20E. The overall agreement was 82.7 per cent. When a numerical identification programme for Enterobacteriaceae was used to analyze the results of 440 E.coli isolates, the agreement with API 20E increased from 81.4 to 91.1 per cent. Numerical identification was then employed to evaluate 14 routine biochemical test panels used in 12 Swedish laboratories, and an additional 18 potential new test panel variants. The theoretical identification power of the panels was measured by a scoring system, based on simulated test results for the 14 most common species of Enterobacteriaceae. The results showed wide variations in the performance of different panels, with a number of panels being of insufficient quality. Among the 32 test panels, 6 panels indicated excellent performance. These should be further evaluated for routine laboratory performance. Numerical identification methods constitute powerful tools in the hands of the clinical microbiologist to aid in species identification as well as to analyze the quality of identification charts in use.

Antimicrobial resistance 1979–2009 at Karolinska hospital, Sweden: normalized resistance interpretation during a 30‐year follow‐up on Staphylococcus aureus and Escherichia coli resistance development

“…The two most frequent bacterial pathogens, Staphylococcus aureus and Escherichia coli , were included in the analysis. Species identification was according to established procedures (75–77). Methicillin‐resistant S. aureus , MRSA, was suspected when inhibition zones around a 10 μg cefoxitin disc were below 22 mm and then confirmed by PCR detection of the mecA gene (http://www.srga.org).…”

Acquired sulphonamide resistance genes in faecal Escherichia coli from healthy children in Bolivia and Peru

“…Identification of E. coli isolates was always confirmed using a series of biochemical tests (Voges-Proskauer, mannitol fermentation/gas production and production of betagaloactosidase, lysine decarboxylase, ornithine decarboxylase, urease and indole) using numerical identification procedures [18]. E. coli ATCC 25922 was used as a quality control organism.…”

Integrons and gene cassettes in clinical isolates of co-trimoxazole-resistant Gram-negative bacteria

“…Of these, 71 were consecutive trimethoprim‐resistant or intermediately‐resistant isolates, while the remaining 34 were consecutive trimethoprim‐susceptible isolates. The isolates were identified initially by standard biochemical tests and were tested for resistance to trimethoprim by disk diffusion [25] using Isosensitest agar and antibiotic disks (Oxoid AB, Sollentuna, Sweden). Zone breakpoints used for determining trimethoprim sensitivity and resistance were 17 mm and 13 mm, respectively, as recommended by the Swedish Reference Group for Antibiotics (SRGA) (http://www.srga.org) [26,27].…”