Evaluation of Alamar colorimetric broth microdilution susceptibility testing method for staphylococci and enterococci

Abstract

We compared the results of the Alamar broth microdilution susceptibility testing method with the results of the National Committee for Clinical Laboratory Standards reference broth microdilution method for 119 gram-positive organisms. The strains were tested for their susceptibilities to 20 antimicrobial agents. Only appropriate antimicrobial agents were evaluated for each species of bacteria. Absolute categorical agreement between the reference method and the test method was 91.5% for enterococci, 99.8% for oxacillin-susceptible staphylococci, and 97.4% for oxacillin-resistant staphylococci. Essential agreement (percent complete agreement plus percent minor errors) was >99% for all organisms tested. The results for enterococci showed no very major errors, one major error with ofloxacin, and numerous minor errors with the quinolones. However, all except one of the minor errors were within ؎1 log 2 dilution of the reference result. For staphylococci, only 2 very major errors (one each with chloramphenicol and oxacillin), 1 major error (chloramphenicol), and 15 minor errors (multiple drugs) were observed. The Alamar colorimetric system was easy to use and the results were easy to read. It appears to be an acceptable method for antimicrobial susceptibility testing of staphylococci and enterococci.

The Contribution of High-Order Metabolic Interactions to the Global Activity of a Four-Species Microbial Community

“…After growth to an OD 600 around 0.2, strains were transferred to a 96 wellplate. The metabolic rate was quantified using a fluorogenic assay for the presence of metabolic intermediates, the AlamarBlue assay containing the redox activity indicator compound resazurin [ 23 – 25 ]. Resazurin based assays have been used to quantify metabolism in a variety of bacterial and eukaryotic cells [ 26 – 32 ], making it a useful, universal indicator for metabolism in multispecies bacterial communities.…”

Biologically Active Heterocyclic Hybrids Based on Quinazolinone, Benzofuran and Imidazolium Moieties: Synthesis, Characterization, Cytotoxic and Antibacterial Evaluation

“…All newly synthesized 3‐[1‐(1‐benzofuran‐2‐yl)‐2‐(4‐oxoquinazolin‐3(4 H )‐yl)ethyl]‐1‐methyl‐1 H ‐imidazol‐3‐ium chloride derivatives were evaluated for their in vitro antibacterial and antifungal activity, using Alamar blue susceptibility test (MABA) method, against three Gram ‐positive bacteria ( Staphylococcus aureus PTCC 1337, Bacillus subtilis PTCC 1023, Listeria monocitogenes PTCC 1165) and three Gram ‐negative bacteria ( Escherichia coli PTCC 1338, Pseudomonas aeruginosa PTCC 1074, Salmonella entritidis PTCC 1091) and also yeast‐like fungi ( Candida albicans PTCC 5027) strains. Ciprofloxacin and Ketoconazole were used as the reference antibacterial and antifungal drugs for comparison.…”

“…Initial dilutions of synthesized hybrid compounds were prepared in DMSO (0.1 ml) and H 2 O (0.9 ml) to obtain concentration 10240 μg/ml as stock solutions. The serial dilution method was used to obtain 5120 to 320 μg/ml concentrations . Except negative control wells which should contain 160 μl of culture, 140 μl of culture were poured in each well of 96‐well plates.…”

“…Following a broth microdilution MIC test, from each well that shows no growth, contents were removed and spreaded onto Mueller–Hinton agar plates for bacteria and Sabouraud dextrose agar for fungi to determine minimum bactericidal concentration ( MBC ) and minimum fungicidal concentration ( MFC ) results. The plates were incubated for 24 h at 37 °C for bacteria and 25 °C for fungi …”

Comparison of Enzymatic Chemiluminescent Assay and Standard Agar Plate Method in the Determination of Bacterial Viability

“…The adenosine triphosphate (ATP) bioluminescence method (Goldschmidt and Fung 1979) or chromogenic and fluorogenic methods (Manafi et al. 1991; Baker and Tenover 1996) are rapid techniques that combine simplicity with a highly sensitive assay. However, the ATP bioluminescence method is expensive and unreliable for food materials containing large amounts of nonbacterial ATP.…”