Antimicrobial susceptibility testing (AST): A review of changing trends, quality control guidelines, test accuracy, and recommendation for the testing of β-lactam drugs

Jones, Ronald N.

doi:10.1016/0732-8893(83)90028-7

Cited by 32 publications

(10 citation statements)

References 50 publications

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“…All were susceptible to cefotaxime at a concentration of 16 pug/ml or less as measured by agar dilution (1). Susceptibilities from agar diffusion tests with 30-,ug cefotaxime disks agreed with agar dilution results (2,3).…”

supporting

confidence: 55%

Comparison of a beta-lactamase induction test with a test that detects low-frequency resistance to cefotaxime

Menzies¹,

MacCulloch²

1985

Antimicrob Agents Chemother

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A paper strip test that detects cefotaxime-resistant variants of gram-negative bacilli was described and compared with a beta-lactamase induction test. Both tests demonstrated a potential for resistance that is not indicated by standard agar dilution and agar diffusion tests.Emergence of bacterial resistance during therapy with third-generation cephalosporins such as cefotaxime has been noted by a number of authors whose findings were recently reviewed by Sanders and Sanders (7). Standard antibioticsusceptibility tests did not reveal the potential for resistance to emerge, and a beta-lactamase induction test (6) has been recommended for this purpose (5). This test detects bacteria that produce the Richmond and Sykes type I chromosomally mediated inducible beta-lactamase (9) which is associated with the emergence of resistance to third-generation cephalosporins (4,5,8,10).We have found that a paper strip test will demonstrate antibiotic-resistant bacterial cells present in a population that appears susceptible when tested by standard methods (4,5,8,9). It has been suggested that these variant cells may survive antibiotic treatment and cause therapy failure (7). We describe the paper strip test and compare it with the beta-lactamase induction test.For the beta-lactamase induction test, Mueller-Hinton agar plates were inoculated with gram-negative bacilli as for disk diffusion susceptibility testing. A 30-,ug cefoxitin disk (Becton Dickinson & Co., Paramus, N.J.) was placed on each plate, and a 30-,ug cefotaxime disk (Biological Laboratories Ltd., Auckland, New Zealand) was placed next to it, separated by a distance equal to the sum of the zones of inhibition for each disk when tested separately. Negative tests showed no change in the zone of inhibition around each cefotaxime disk. Positive tests showed a decreased zone of inhibition, equal to 4 mm or more around the cefotaxime disk adjacent to the cefoxitin disk (Fig. 1) (Fig. 2). * Corresponding author.These colonies were picked off and tested for an increase in cefotaxime resistance.We tested 292 gram-negative bacilli that were recent significant clinical isolates from the microbiology department of our hospital. All were susceptible to cefotaxime at a concentration of 16 pug/ml or less as measured by agar dilution (1). Susceptibilities from agar diffusion tests with 30-,ug cefotaxime disks agreed with agar dilution results (2, 3).Of the 78 isolates of Serratia, Citrobacter, indole-positive Proteus, Enterobacter, and Pseudomonas species, 59 produced colonies within the zone of inhibition next to the paper strip for the heavy inoculum (Table 1). Subsequent tests of these colonies confirmed increased resistance, with MICs of cefotaxime at least four times higher than those of the original inoculum. Still within the clinically susceptible range were 27 isolates that produced colonies with MICs to cefotaxime of 32 ,ug/ml or less. Colonies from 32 isolates had MICs that had increased to, or were greater than, 64 ,ug/ml and were classified as clinically resistant. Of ...

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supporting

confidence: 55%

Comparison of a beta-lactamase induction test with a test that detects low-frequency resistance to cefotaxime

Menzies¹,

MacCulloch²

1985

Antimicrob Agents Chemother

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“…Both agar and broth dilution methods are used for susceptibility tests on aerobic and facultative bacteria. Both of these methods were found to be equally effective and correlated well to each other (Jones 1983). However, the method most suitable to determine the susceptibility of anaerobic bacteria, including B. fragilis group, is yet to be determined (Finegold et nl.…”

mentioning

confidence: 80%

Growth of Bacteraides fragilis group in agar and broth media

Brook

1990

Journal of Applied Bacteriology

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The rate of bacterial growth of four Bacteroides fragilis group organisms was determined in agar and broth media. Exponential bacterial growth occurred in agar media within 4 to 8 h, while such growth was delayed in broth media and occurred within 12-24 h after inoculation. This phenomenon may explain why antimicrobials which manifest an 'inoculum effect' may show increased resistance to antimicrobials when tested in agar media.

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“…The two regression line constants, A, the slope, and B, the intercept, vary between bacterial species, medium used and between different laboratories. The inter-laboratory differences are caused by methological variations, despite strict standardizations of the disc-diffusion method (2,10,12,13,22,24). The numerical values of the two constants A and B for the fifteen species indicated a high degree of homogeneity between most species versus ceftazidime with a clustering in three groups.…”

Section: Discussionmentioning

confidence: 99%

“…For other antibiotics these differences were often much larger (8,15,16,17,18,19). The SRA method thus provides a method for individal laboratories to determine species-specific and laboratory-related interpretive breakpoints for improved accuracy ( 1,2,4,9,10,14,15,20,22).…”

Section: Discussionmentioning

confidence: 99%

Determination of Interpretive Breakpoints for Ceftazidime Disc‐diffusion Susceptibility Testing Using Single‐Strain Regression Analysis

Petersson

Kronvall

1985

Acta Pathologica Microbiologica Scandinavica Series B: Microbio

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Interpretive breakpoints for ceftazidime disc‐diffusion susceptibility testing were determined using single‐strain regression analysis (SRA). Regression lines were determined for a total of 58 strains representing 15 species, from inhibition zone diameters obtained for discs containing six different ceftazidime concentrations. Statistical analysis for excluding non‐linearity of test‐results was performed. A minimum of five tests on consecutive days was required for maximal precision of regression analysis according to the SRA‐method. Calculated regression lines showed similarities within individual and groups of bacterial species. A minimum of five strains could be used to represent these groups. Interpretive breakpoints according to recommended MIC‐limits were determined for each species taking into consideration confidence limits for zone correlates of MIC‐values. Single‐strain regression analysis for the determination of interpretive breakpoints for ceftazidime disc‐diffusion susceptibility testing in individual laboratories.

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Antimicrobial susceptibility testing (AST): A review of changing trends, quality control guidelines, test accuracy, and recommendation for the testing of β-lactam drugs

Cited by 32 publications

References 50 publications

Comparison of a beta-lactamase induction test with a test that detects low-frequency resistance to cefotaxime

Comparison of a beta-lactamase induction test with a test that detects low-frequency resistance to cefotaxime

Growth of Bacteraides fragilis group in agar and broth media

Determination of Interpretive Breakpoints for Ceftazidime Disc‐diffusion Susceptibility Testing Using Single‐Strain Regression Analysis

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