Introduction to Laboratory Procedures in Medical Microbiology and Parasitology

Practice review flashcards covering laboratory procedures, specimen procurement, culture media, microscopy, differential staining techniques, and parasitological examinations based on lecture notes by Dr. Lawson S.D.

What is the major role of a medical laboratory in patient care?

To assist in the diagnosis and treatment of diseases by performing qualitative, quantitative, or screening test procedures or examinations on materials derived from the human body.

What are the five basic procedures ("five I's") used by microbiologists to examine and characterize microbes?

Inoculation, Incubation, Isolation, Inspection (observation), and Identification.

What are the three main phases of specimen procurement and handling in laboratory testing?

Pre-Analytical Phase (collection and transport guidelines), Analytical Phase (standard operating testing procedures), and Post-Analytical Phase (reporting and result interpretation).

What essential details must be clearly labeled on a clinical specimen container?

The patient's name, hospital number, ward, date, and time of collection.

Which types of clinical laboratory tests require blood collected in plain bottles without anticoagulants?

Tests that require serum.

What are four common anticoagulants used in clinical laboratory specimen bottles?

Heparin, Ethylene Diamine TetraAcetic Acid (EDTA), Fluoride-oxalate mixture, and Citrate.

What is venipuncture?

The step involved in obtaining an appropriate, identified blood specimen from a patient's vein.

What are the 3Rs of reporting clinical laboratory results?

Reliability, Rapidity, and Relevance.

How is a qualitative analysis defined in clinical laboratory testing?

A test that detects the presence of a specific substance or matter, or reveals the constituent matter of importance, in a given clinical specimen.

How is the total magnification of an optical microscope calculated?

By multiplying the magnification of the objective lens by the magnification of the eyepiece.

According to this labeled diagram of a microscope, which component is positioned directly beneath the stage aperture and above the illuminator?

The condenser (and diaphragm).

How is sterilization defined in microbiology?

The destruction or removal of all microorganisms, including bacteria and their endospores, viruses, fungi, and prions.

What is the most commonly used instrument in the microbiology laboratory for sterilizing culture media and glassware?

The autoclave.

What is the primary difference in application between disinfectants and antiseptics?

Disinfectants are applied to inanimate surfaces, medical equipment, and man-made objects, whereas antiseptics are used to disinfect the skin.

What is the difference between bactericidal and bacteriostatic substances?

Bactericidal substances kill bacteria, whereas bacteriostatic substances interfere with bacterial cell growth and reproduction.

What is sanitization?

Any cleansing technique that mechanically removes microorganisms to reduce them to a minimal level to control infection or spoilage.

What alga is agar derived from, and at what temperature does liquid agar solidify as it cools?

Agar is derived from the red alga Gelidium, and it solidifies when it cools to $42\,^\circ\text{C}$.

What defines a chemically defined or synthetic culture medium?

A medium with a defined, exact chemical composition prepared using a precise formula of inorganic and/or organic chemicals in distilled water.

Why is chocolate agar named chocolate agar?

It is enriched with heat-treated blood, which turns brown and gives the medium its characteristic color.

How does Mannitol Salt Agar function as a selective medium?

It contains $7.5\%$ $\text{NaCl}$, which inhibits most human pathogens except for members of the genus Staphylococcus.

What culture medium is shown in this image, and what do its black colonies indicate?

Xylose lysine deoxycholate agar (a selective and differential medium); black colonies indicate the production of hydrogen sulfide.

What centrifugation speed and duration are specified for preparing urine sediment in urine microscopy?

Centrifuged at low speed ($2500\,g$) for $5\,\text{minutes}$.

Why do Gram-positive bacteria retain the primary crystal violet stain and appear purple under microscopy?

Due to teichoic acid in their intact cell wall, which forms a mesh that prevents the primary stain-mordant complex from being washed away by the decolorizing agent.

In this comparison of Gram-stained bacteria, which color corresponds to Gram-positive bacteria and which to Gram-negative bacteria?

Gram-positive bacteria appear purple/violet (left), while Gram-negative bacteria appear red/pink (right).

According to this Gram staining procedure diagram, what reagent is used for decolorization and for how long is it applied?

95% Ethyl Alcohol applied for 5 to 10 seconds.

What decolorizer and counterstain are used in the Ziehl-Neelsen (ZN) method for Acid-Fast staining?

Decolorizer: $3\%$ acid alcohol; Counterstain: $0.5\%$ methylene blue or malachite green.

Which main type of microbial culture technique is specifically used for identifying viruses?

Cell Culture (infecting human or animal cell cultures with the microbe).

According to this diagram comparing thick and thin blood film examination patterns, what is the primary diagnostic purpose of the thin film?

To observe the morphological characteristics of parasites in order to accurately identify their specific species.

What parasites or parasite stages can be detected in urine specimens?

Eggs of Schistosoma haematobium, Microfilariae of Wuchereria bancrofti, Microfilariae of Onchocerca volvulus, and Trophozoites of Trichomonas vaginalis.