Detection of antibiotic susceptibility by colorimetric minimum inhibitory concentration in staphylococcal isolates

Abstract

Aim: Assess performance of broth microdilution (BMD) as well as agar dilution methods for antimicrobial susceptibility testing of Staphylococci using tetrazolium salt. Methods and Results: Minimum inhibitory concentration (MIC) of eight antimicrobials; vancomycin (VA), linezolid, oxacillin, gentamicin (CN), tetracycline, ciprofloxacin, erythromycin and clindamycin was investigated for 80 isolates of Staphylococci by BMD with the addition of dimethyl thiazole diphenyl tetrazolium bromide (MTT), agar dilution with the addition of MTT and triphenyl tetrazolium chloride at the standard bacterial concentration together with addition of MTT at an experimental bacterial concentration. BMD (MTT) showed the highest agreement in comparison with the standard BMD. Conclusions: Colorimetric BMD was rapid and easy to interpret. Colorimetric agar dilution (MTT) was less tedious than BMD. Significance and Impact of the Study: Colorimetric antibiotic susceptibility is a good option to provide rapid reliable results for critically ill patients. In addition, agar dilution (MTT) helps to investigate outbreaks of methicillinresistant Staphylococcus aureus (MRSA), VISA or VRSA. BMD (MTT) can be performed routinely to detect VA MIC in MRSA blood stream infections and hospital acquired pneumonia, where, high VA MIC is associated with a higher mortality rate.

Prevalence and antimicrobial susceptibility profile of multidrug-resistant bacteria among intensive care units patients at Ain Shams University Hospitals in Egypt—a retrospective study

“…However, the results of other researchers regarding vancomycin and linezolid were in favor to that obtained in the present study where Al-Zoubi and his colleagues reported that all their S. aureus isolates were 100% susceptible to vancomycin [26]. Also, Basak et al [11] and Mahmoud et al [27] reported 100% susceptibility to both vancomycin and linezolid. The higher antibiotic resistance rates reported by the abovementioned researches in comparison to the current results might be attributable to inconvenient use of antimicrobials, geographic and socioeconomic variations, sampling biases, and dissimilar patients' characteristics [28].…”

Recent Developments in Phenotypic and Molecular Diagnostic Methods for Antimicrobial Resistance Detection in Staphylococcus aureus: A Narrative Review

“…Second, it is difficult, if not impossible, to have a homogeneous report due to the large variety of available methods. For example, the sensitivity, and specificity of the rapid BMD method [ 30 ], are conceptually different from the sensitivity and specificity of Raman spectroscopy and deep learning approaches [ 118 ]. Another example is when studies that assess diagnostic performance differ in their definition of TAT; some studies consider only the duration of the test, while others consider test duration plus hands-on time and sample preparation (see for example [ 76 , 77 , 79 , 80 ]).…”

“…The rapid BMD is easy to interpret, provides accurate AST results and is low cost. Therefore, it represents a good method that could be routinely implemented, especially in settings with limited resources [ 30 ].…”

Evaluation of antimicrobial potential and phytochemicals in Acmella ( A. oleracea ) flower pod extracts subjected to different drying techniques

“…In vitro antibacterial and antifungal activity were determined using NB and SDB medium, respectively. Bacterial and fungal cells were treated with different concentrations of the extract and MIC values were determined using the 96 well microtiter plate‐based method with 2,3,5, triphenyl tetrazolium chloride (TTC) dye as described by Mahmoud et al., (2019) with some modifications. By usingsterile distilled water 0.2 mg/ml TTC dye was prepaired.…”