AUTOMATED SYSTEMS FOR BACTERIAL IDENTIFICATION AND ANTIBIOGRAM (VITEK 2 AUTOMATED COMPACT SYSTEM)

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There are several commercially available automated systems or computerized instrument and/or equipment that aid in the clinical/laboratory diagnosis of infectious diseases in the hospital especially as it relates to prompt and accurate identification of microbes. These automated systems also aid in carrying out antimicrobial susceptibility test (antibiogram) on identified clinical pathogens so that antimicrobial therapy can be properly guided. The VITEK 2 automated compact system (BioMérieux-Vitek) is one of such advanced expert systems that could be used in clinical microbiology laboratories for the prompt identification of microbial pathogens and for the determination of the antimicrobial susceptibility of already identified microbes (inclusive of bacteria and fungi). The VITEK 2 automated system is an automated high-throughput microbial identification system that uses an innovative mass spectrometry (MS) technology such as the Matrix Assisted Laser Desorption Ionization Time-of-Flight (MALDI-TOF) to provide pathogen identification results and antimicrobial susceptibility test (AST) results in minutes. It detects metabolic changes by fluorescence-based methods which facilitate the identification of Gram-negative bacteria, Gram-positive bacteria and pathogenic fungi from clinically-relevant specimens within some few hours.

The VITEK 2 system monitors the kinetics of bacterial and/or fungal growth and calculates the minimum inhibitory concentrations of (MICs) of antimicrobial agents or antibiotics using a unique algorithm with taxonomically updated databases of microbial strains and AST profiles. The VITEK system includes an Advanced Expert System (AES) that analyzes minimum inhibitory concentration (MIC) patterns of antimicrobial agents or antibiotics. This automated system also detects phenotypes for most microbial organisms including Gram-positive bacteria, Gram-negative bacteria and yeast-like organisms (Figure 1). The VITEK systems provide rapid laboratory test results especially as it is related to bacterial identification and antibiogram. Rapid laboratory results allow clinicians/physicians to discontinue blind treatment or empiric antimicrobial therapy (which allow resistant pathogens to evolve and spread). These rapid testing protocols will also guide physicians to prescribe targeted antimicrobial therapy that would result into improved patient outcomes and enhanced antibiotic stewardship in this era of skyrocketing antibiotic resistance.

Figure 1: The VITEK 2 automated compact equipment and workstation for bacterial identification and antimicrobial susceptibility test (AST). VITEK 2 automated system is used for microbial identification (bacteria and yeast), AST and it can also be used for epidemiological studies especially in the typing of bacterial strains. (1). Barcode scanning system for data entry (2). Windows-based user-friendly computer (3). The VITEK 2 processing unit. Photo courtesy: BioMérieux.

On a daily basis, medical doctors use results from the identification of pathogens from clinical specimens and antibiotic susceptibility test (AST) results to determine the antibiotic treatment that is most appropriate for a particular patient or disease condition in order to achieve best patient care. Also, the results from the AST are used to monitor changes in bacterial resistance to antibiotics in order to detect and halt any possible outbreak of disease due to resistant pathogens. Bacterial identification and antibiotic susceptibility testing play an essential role in patient care and the control of antibiotic resistance. These important laboratory procedures indicate the aetiology of the disease and also the likely antibiotics most suitable to cure or treat the infection or disease. AST also help physicians to avoid the unnecessary prescription of antibiotics – which help to reduce healthcare costs and prevent the evolution of drug resistant organisms.

However, these important clinical microbiology procedures (i.e. identification of pathogenic organisms and AST) are usually delayed in some hospitals because they lack the equipment and or instrument required to carry out these techniques promptly and deliver accurate results under the shortest possible time. The VITEK 2 system or platform is an AES that offers automated bacterial identification and AST so that clinical results as it pertains to AST and bacterial identification could be obtained within minutes or hours of processing the sample (Figure 2). In the conventional microbiological culture technique of bacterial identification and AST, clinical results pertaining to microbial identification and AST usually takes days to get. This impact negatively on the patient’s prognosis since blind treatment may be initiated until the test results from the clinical microbiology laboratory is finally obtained. Such practices may give rise to the emergence and spread of drug-resistant microbes.

Figure 2: Illustration of the workflow pattern using the VITEK 2 automated compact system for microbial identification and antimicrobial susceptibility test (AST). Photo courtesy: BioMérieux.

FURTHER READING

Ashutosh Kar (2008). Pharmaceutical Microbiology, 1st edition. New Age International Publishers: New Delhi, India. 

Block S.S (2001). Disinfection, sterilization and preservation. 5th edition. Lippincott Williams & Wilkins, Philadelphia and London.

Courvalin P, Leclercq R and Rice L.B (2010). Antibiogram. ESKA Publishing, ASM Press, Canada.

Denyer S.P., Hodges N.A and Gorman S.P (2004). Hugo & Russell’s Pharmaceutical Microbiology. 7th ed. Blackwell Publishing Company, USA. Pp.152-172.

Ejikeugwu Chika, Iroha Ifeanyichukwu, Adikwu Michael and Esimone Charles (2013). Susceptibility and Detection of Extended Spectrum β-Lactamase Enzymes from Otitis Media Pathogens. American Journal of Infectious Diseases. 9(1):24-29.

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