Since the dawn of automated technologies in the 1980s, antibiotic susceptibility tests have been perpetually improvised and, hence, have superseded conventional phenotypic methods
[2]. Automation, simplicity, and compactness are the major reasons for their widespread acceptance in diagnostics. Computer integration has allowed online analysis and data sharing, which is a giant leap for results validation, especially in remote areas
[27]. Among the developed automated systems, MicroScan WalkAway (Beckman Coulter, Inc. Atlanta, Georgia, USA) (1980), Micronaut (Merlin, berlin, Germany) (1990), the avantage test (Abbott Laboratories, Irving, Texas, USA) (1980), Vitek 2 (bioMe’rieux, Marcy-l’Étoile, France) (2000), Phoenix (BD Diagnostics, Franklin Lakes, New jersey, USA) (2001), and Sensititre ARIS 2X (Trek Diagnostic Systems, Oakwood Village, Ohio, USA) (2004) are the major FDA approved systems for AST. Vitek and Pheonix detect growing bacteria on the basis of turbidity, whereas comparable automated systems like MicroScan WalkAway (Beckman Coulter, Inc. Atlanta, Georgia, USA) and Sensititre ARIS 2X (are based on fluorescence emission of the growing bacteria. The resistance in gram-negative, gram-positive, and
Streptococcus strains of bacteria can easily be estimated through Phoenix, and Vitek 2, but, MicroScan WalkAway and Sensititre ARIS 2XESBL (Trek Diagnostic Systems, Oakwood Village, Ohio, USA) are capable of detecting the extended-spectrum beta-lactamase (ESBL)-producing strains in the species mentioned above
[28]. Micronaut and Avantage are capable of accurate direct susceptibility testing for gram-positive and gram-negative bacteria, respectively
[29][30].
Detection incompatibility for many bacteria/antibiotics using Sensititre ARIS 2 and Vitek 1 have led to the development of the updated Sensititre ARIS 2X and Vitek 2, which have better performances and are applicable to a broader range of bacteria/antibiotics. Presently, all the automated systems are incorporated with advanced expert system software for enhanced performance and online data processing
[10]. Every automated system has a specific panel capacity and an average time for performing detection, which varies from 40 to 100 wells, and can vary in time such as 20, 12 and 9 h, respectively. Certain models such as Phoenix AP, and Vitek 2Xl, are dedicated towards automated inoculation, enhanced card capacity and compactness.
The aforementioned systems lack reproducibility, sensitivity, and reliability compared with the existing traditional methods. Moreover, an inability to test a wide range of clinically relevant bacteria (e.g.,
S. pneumonia), antimicrobial agents (e.g., vancomycin), and heteroresistant isolates, as well as a limited panel capacity and the high cost of instruments and consumables, are all significant issues that restrict these systems from frequent analysis
[31].