Microbiology Media Quiz

Fluids, swabs, tissues, bottles, and tubes are used to collect specimens from various parts of the body such as eyes, ears, nose, throat, wounds, ulcers, genital areas, and body fluids like pus, urine, sputum, bile, CSF, and blood.

Normal flora can contaminate specimens, so contamination should be avoided during collection and transport.

Specimen transport is critical for maintaining the viability of microorganisms, including anaerobes, and should be done as quickly as possible, at the correct temperature, and with transport media.

Microorganisms are identified using various laboratory diagnostic methods such as direct microscopy, antigen detection, culture, and genome detection.

Different methods are used based on the type of specimen and the expected organism, and the availability of culture.

Microscopy is used to identify the morphology and arrangement of bacteria and to provide a presumptive diagnosis, but it does not tell us about the exact species of bacteria.

Gram stain is a commonly used method for rapid identification, and it provides presumptive diagnosis by identifying the morphology and arrangement of bacteria based on their reaction to the stain.

Acid-fast stain, India ink, and fluorescent stains are used for specific organisms and to detect their unique characteristics.

Microscopy has limitations, including the need for expertise and time, and difficulties in evaluating specimens where normal flora are present.

Culture is the process of growing microorganisms in artificial culture media, which allows for the study of bacterial morphology, biochemical tests, and antibiotic sensitivity patterns.

Different types of culture media are used based on their appearance or consistency, including liquid media, semisolid media, and solid media.

Colonial morphology is used to identify bacteria based on their growth patterns and can be used to study bacterial morphology, demonstrate biochemical features, and determine antibiotic sensitivity patterns.

media types: simple/basal (nutrient agar), enriched (blood agar, chocolate agar), enrichment media (alkaline peptone water, Selenite F broth, tetrathionate broth), selective media (TCBS, XLD, MacConkey, Stuart, alkaline peptone H2O), transport media (Stuart, alkaline peptone H2O), anaerobic media (Robertson cooked meat broth), automated culture media

enriched media: supports growth of nutritionally demanding bacteria, added nutrients (blood, serum, egg), tests hemolytic property of bacteria (Staph aureus, Strep pyogenes), supports growth of fastidious bacteria (Haemophilus influenzae, Neisseria species)

selective media: solid media with inhibitory substances, prevents unwanted organisms from growing

enrichment media: prevents growth of contaminated microorganisms

transport media: not for bacterial growth, used for transporting clinical specimens

different media for specific bacteria: TCBS agar (Vibrio cholerae), DCA (salmonella, shigella), Thayer Martin medium (Gonococci)

automated culture media: mainly for blood and sterile body fluid culture, monitors microbial growth continuously, high cost, no observation of colony morphology.

aerobic culture methods: inoculate specimen onto media and incubate at 37°C

anaerobic culture methods: evacuate oxygen, use reducing agents or absorption methods, maintain anaerobic conditions with biochemical indicators.

limitations: appropriate collection, transport, and incubatory conditions required to maintain bacterial viability.