Measurement of Antimicrobial-Resistant Escherichia coli in Pig Feces with a Hydrophobic Grid Membrane Filter Interpreter System

Abstract

Hydrophobic grid membrane filter technology was used to measure resistance among Escherichia coli in pig fecal samples to ampicillin, sulfisoxazole, and tetracycline. The method accurately measured resistance, with sensitivities ranging from 96.5 to 99.5% and specificities ranging from 87.0 to 98.3%, and it identified E. coli with 96% confidence.

Mass screening for antimicrobial resistant Escherichia coli in dairy cows in northern New South Wales

“…Hydrophobic grid membrane filtration (HGMF) master grids were used to enumerate and replicate bacteria using a modification of the approach used by Dunlop et al 16 The HGMF grids were 60 mm square, had a base made of a membrane filter (45 µm pore size) and had a 40 x 40 grid pattern printed on the surface with a hydrophobic substance. 17 During filtration, suspended bacteria lodged in one of the 1600 grid cells and grew there when the grid was placed on agar and then incubated (90 mm diameter circular plates were used throughout this work).…”

“…Resistance testing required production of a 'master HGMF grid' with not more than 200 colonies of any type to limit the probability of any one colony being derived from more than one bacterium. 16 Colonies that grew on the master grid during incubation were replicated onto other HGMF grids placed on agar containing antimicrobials (for resistance testing) and chromogens (producing a colorimetric change for distinguishing E coli colonies) and these were also incubated. For each specimen a frozen sample of diluted faeces was thawed in a 30°C water bath and then 10 fold serial dilutions made in 0.1% peptone water containing 1% Tween 80 (Difco, Detroit, MI, USA).…”

The quantitative measurement of antimicrobial resistance in Escherichia coli at the meta-population level (meta-population analysis)

“…There is no clear agreement on the appropriate methodology to measure quantitatively antimicrobial resistance in such populations. Within a sample the resistance ÔabundanceÕ has been described in terms of the concentration of resistant bacteria per unit weight (Linton et al 1978), or more commonly as the proportion (percentage) of bacteria that are resistant (Langlois et al 1983;Dunlop et al 1998). In such studies the resistance estimates depend upon the measurement of bacterial isolates drawn from populations of millions or more.…”

Phenotypic and genotypic profiling of antimicrobial resistance in enteric Escherichia coli communities isolated from finisher pigs in Australia

“…A secondary objective was to screen the commensal E. coli populations for common, plasmid‐borne ARGs, including those imparting resistance or reduced susceptibility to 3rd‐generation cephalosporins and fluoroquinolones, which have public health significance. The laboratory techniques used were based on the use of hydrophobic grid‐membrane filtration (HGMF), which can efficiently assess up to several hundred E. coli colonies through a process of filtration of diluted faeces, growth on selective media, colony replication and enumeration of colonies using digital image analysis …”

“…The HGMF measurement system was used to inform on historical exposure of commensal communities to antimicrobials in the pig industry, while defining aspects of epidemiology of resistance in Gram‐negative enteric organisms that could affect the conducting of surveillance . When combined with pooling specimens from individual animals within the farms and multiplex PCRs to screen for common plasmid‐mediated ARGs, a detailed profile of phenotypic and genetic resistance was built for each farm.…”