Antimicrobial Susceptibility Testing (AST) & Antibiogram

STANDARD QUALITY CONTROL STRAINS FOR ANTIBIOGRAM

Quality control strains (or reference strains)are typed cultures of microorganisms with known antimicrobial susceptibility patterns and which are used to ensure consistency, accuracy and reproducibility of a particular susceptibility test. They are important in any disk diffusion test because susceptibility tests are affected by plethora of factors such as incubation temperature, size of the test […]

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PREPARATION OF 0.5 McFARLAND TURBIDITY STANDARDS

McFarland Turbidity Standard is an important technique performed in the microbiology laboratory especially when carrying out antimicrobial susceptibility studies. It is a turbid solution that contains a mixture of barium salt, distilled water and tetraoxosulphate (VI) acid (H2SO4). McFarland turbidity standard is used to compare and balance the turbidity of both the test and control

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METALLO-β-LACTAMASE (MBL) – detection methods

Metallo-beta-lactamases (MBLs) are beta-lactamase enzymes produced by pathogenic bacteria, and which hydrolyzes the carbapenems (e.g. imipenem, meropenem, and ertapenem) and render the antibiotics ineffective for treatment. They are encoded by genes that have been procured by pathogenic bacteria either by mutation or by horizontal gene transfer from other resistant microbes. MBLs efficiently hydrolyze all beta-lactam

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EXTENDED SPECTRUM β-LACTAMASE (ESBL) – detection methods

Extended spectrum beta-lactamases (ESBLs) are beta-lactamase enzymes that breakdown or hydrolyze broad-spectrum beta-lactam drugs especially the third-generation oxyimino-cephalosporins (e.g. ceftazidime, ceftriaxone and cefotaxime). There is no consensus for the actually definition of ESBLs; but the acronym “ESBL” was originally coined to reflect the expanded substrate spectrum of the earlier beta-lactamase enzymes (e.g. TEM- and SHV-enzymes).

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BETA-LACTAMASE: an important resistance mechanism in bacteria

Beta-lactamases are enzymes secreted by both Gram positive and Gram negative bacteria, and which have the ability to hydrolyze (breakdown) beta-lactam antibiotics. Beta-lactamases are responsible for bacterial resistance to broad class of-beta-lactam antibiotics, including the penicillins, cephalosporins and carbapenems. They provide antibiotic resistance in pathogenic bacteria by breaking the antibiotic structure, thereby leaving a molecule

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Antibiotic Resistance / Antimicrobial Resistance (AMR), Antimicrobial Susceptibility Testing (AST) & Antibiogram, Pharmaceutical Microbiology, ,

MULTIDRUG RESISTANT BACTERIA (MDRB)

The introduction of antibiotics into clinical medicine for the treatment of infectious diseases heralded an era of one of the most significant breakthrough in medicine – since most infectious diseases that caused morbidity and mortality in the human race was drastically reduced and contained with antibiotics (the magic bullets). Particularly, penicillin was the first antibiotic

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MINIMUM INHIBITORY CONCENTRATION (MIC)

Antimicrobial susceptibility tests are used to determine which specific antibiotics or antimicrobial agents a particular pathogenic bacterium or fungus is sensitive to; and susceptibility tests can guide the physician in drug choice and dosage especially for difficult-to-treat infections. The results of antimicrobial susceptibility tests or studies are commonly reported as the minimal inhibitory concentration (MIC),

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MEASUREMENT OF ANTIMICROBIAL EFFICACY/ACTIVITY

The determination of the antimicrobial susceptibility of a given pathogen to a particular antimicrobial agent can be performed or undertaken by one of two basic methods, viz: Agar Disk Diffusion Method Agar disk diffusion technique of antimicrobial susceptibility testing provides a basis for the classification of a pathogenic strain as susceptible, intermediate or resistant to

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GENOTYPIC DETECTION OF ANTIBIOTIC RESISTANT MICROBES

The genotypic detection and characterization of antibiotic resistant genes in pathogenic bacteria is more specific in characterizing resistance genes than the phenotypic detection methods. The term genotypic is derived from genotype – which is the complete genetic makeup of an organism. Genotype describes the overall composition of the genetic information found in an organism.  Thus,

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FEATURES OF THE VITEK 2 AUTOMATED COMPACT SYSTEM FOR BACTERIAL IDENTIFICATION AND ANTIMICROBIAL SUSCEPTIBILITY TEST (AST)

Helping the physician select the best treatment at a much faster pace based on the right microbial identification and antimicrobial susceptibility test is crucial in any infectious disease management and patient total wellbeing. Clinical microbiology laboratories are the first lines of defense for the detection of antibiotic resistance from clinical pathogens and/or samples. And the

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