MT MLO key terms

The sequence for collecting blood tubes to prevent cross-contamination: blood culture, sodium citrate, serum, heparin, EDTA, glycolytic inhibitor. Mixing order matters because additives can carry over.

Transfer of additive or analyte from one tube or specimen to another during collection or processing, causing falsely elevated or depressed results. Prevented by proper order of draw and tube mixing.

Effect of tube additives such as EDTA, citrate, or heparin on microbial growth or assay performance. EDTA can inhibit some organisms and chelate cations; citrate dilutes plasma and binds calcium.

Predefined conditions that make a specimen unacceptable for testing, such as improper container, insufficient volume, delayed transport, or mismatch between label and requisition. Rejection protects result integrity.

The length of time and conditions under which a specimen retains its original microbial or analyte composition. Exceeding stability limits can cause false-negative cultures or inaccurate results.

A non-nutritive buffered solution that preserves fastidious organisms during transport to the laboratory while limiting overgrowth of commensals. Examples include Amies and Stuart media.

A microorganism with complex nutritional requirements that grows only on enriched media and may die quickly outside the host. Examples include Haemophilus influenzae and Neisseria gonorrhoeae.

A culture medium supplemented with nutrients such as blood, serum, or vitamins to support fastidious organisms. Blood agar and chocolate agar are common examples.

A medium containing inhibitors that suppress growth of unwanted organisms while allowing target organisms to grow. Examples include MacConkey agar and Columbia CNA agar.

A medium that distinguishes between types of microorganisms based on visible biochemical reactions, such as lactose fermentation or hemolysis. Examples include MacConkey and blood agar.

Destruction of red blood cells in blood agar, classified as alpha (green), beta (clear), or gamma (none). Used to presumptively identify streptococci and other organisms.

Grouping of streptococci by hemolytic pattern (alpha, beta, gamma) and Lancefield antigen (A, B, C, etc.). Guides identification and clinical significance.

The lowest concentration of an antimicrobial that prevents visible growth of a microorganism under defined conditions. Used with breakpoints to categorize susceptibility.

A threshold antimicrobial concentration used to classify an isolate as susceptible, intermediate, or resistant. Breakpoints are set by standards organizations and updated as resistance evolves.

Laboratory methods that determine whether a microorganism is inhibited by antimicrobial agents, including disk diffusion, broth dilution, and gradient diffusion. Results guide therapy.

Bacteria that resist decolorization with acid-alcohol after staining, notably Mycobacterium species. Detected by Ziehl-Neelsen or fluorochrome stains.

The primary causative agent of tuberculosis, an acid-fast, slow-growing bacillus. Requires specialized media and prolonged incubation; identified by molecular and phenotypic methods.

A genus of branching, gram-positive, weakly acid-fast bacilli that cause pulmonary and disseminated infections. Grows on routine media but may require extended incubation.

A fungus that grows as a mold at ambient temperature and as a yeast at body temperature. Examples include Histoplasma capsulatum and Blastomyces dermatitidis.

A multicellular fungus composed of hyphae that form a mycelium, often producing conidia. Identification is based on colony and microscopic morphology.

A unicellular fungus that reproduces by budding or fission. Clinical identification uses biochemical, morphological, and molecular methods, such as MALDI-TOF or sequencing.

Microscopic examination of stool for parasite eggs, larvae, cysts, and trophozoites using direct wet mounts and concentration techniques. Requires multiple specimens for optimal sensitivity.

A method that separates parasites from fecal debris to increase detection sensitivity, such as formalin-ethyl acetate sedimentation or zinc sulfate flotation.

A permanent stain used in parasitology that colors parasite internal structures blue-green against a green background, aiding identification of trophozoites and cysts.

Techniques that detect nucleic acids to identify pathogens or resistance markers, including PCR, sequencing, and hybridization. Offer speed and sensitivity but require contamination control.

An enzymatic method that amplifies specific DNA sequences through repeated cycles of denaturation, annealing, and extension. Used for direct detection and identification of microorganisms.

Practices that prevent extraneous nucleic acids or organisms from entering molecular or culture tests, including unidirectional workflow, dedicated rooms, and negative controls.

Procedures that monitor test performance by analyzing control materials with known values alongside patient samples. QC helps detect systematic error and ensure results are reliable.

A comprehensive program that monitors and improves all phases of laboratory testing, including pre-analytical, analytical, and post-analytical processes. QA goes beyond daily QC.

External evaluation in which a laboratory analyzes unknown samples and compares results with peer laboratories. Required for accreditation and used to identify performance gaps.

A set of containment precautions for handling infectious agents, ranging from BSL-1 to BSL-4. Level is based on agent risk, transmission route, and laboratory activity.

Barriers such as gloves, gowns, masks, and eye protection worn to prevent exposure to infectious materials. Correct selection and removal are essential for laboratory safety.

A ventilated enclosure that protects the worker, environment, and product from infectious aerosols through HEPA filtration and directional airflow. Class II cabinets are common in clinical microbiology.

A documented record of specimen handling from collection through testing and storage, used to ensure integrity for legal or forensic purposes. Each transfer is signed and dated.

U.S. federal regulations that set quality standards for clinical laboratories, including personnel qualifications, QC, proficiency testing, and inspections. Laboratories need a certificate to test human specimens.

Ongoing professional learning required to maintain certification or licensure. CE activities keep laboratory professionals current with technical and regulatory changes.

A structured evaluation of staff performance, including direct observation, result review, and problem-solving. Required at defined intervals to ensure ongoing competence.