Bacteriology Culture Techniques, Media Types, Quality Control, and Physical/Chemical Sterilization

Flashcards covering bacteriology incubation times, specimen inoculation methods, culture media types and inhibitors, quality control procedures, and physical and chemical sterilization techniques from lecture notes.

Initial Aerobic and Anaerobic Incubation Times

Initial reading for aerobic cultures is at $18$\,hours, while anaerobic cultures require $24\text{--}48$\,hours.

Routine Culture Incubation Time

Standard routine culture incubation requires $48\text{--}72$\,hours.

Blood Culture Bottle Incubation Times

Manual blood culture bottles require $7$\,days, whereas automated blood culture bottles require $5$\,days.

Slow Growing Bacteria Incubation Time

Mycobacteria require $14$\,days to more than a month for incubation.

Bedside Inoculation

Direct inoculation technique performed immediately at the patient's bedside for genital specimens, corneal scrapings, sterile fluids, and nasopharyngeal swabs for Bordetella pertussis.

Streaking Technique

The most common inoculation technique used to obtain isolated colonies by flaming and cooling the loop between each quadrant and streaking successive quadrants.

Stabbing Technique

An inoculation procedure where an inoculating needle is inserted straight down to the bottom of the medium to create an anaerobic environment for deep portion growth.

Overlapping / Lawn Streaking

An inoculation method where the swab streaks the entire surface of an agar plate in an overlapping manner to create a uniform lawn of growth, used for Antimicrobial Susceptibility Testing (AST) or Disk Diffusion Method.

IV Catheter Inoculation Methods

Inoculated either by transfer into thioglycolate broth (to support fastidious organisms) or rolled on solid media and then streaked (to dislodge organisms).

Simple / General / Supportive Media

Media usually composed of meat and soybean extract that supports the growth of most non-fastidious bacteria, such as Nutrient Agar, Nutrient Broth, and TSB.

Enrichment Media (Liquid Type)

Liquid media with specific nutrients without additional supplements used to propagate a specific group of bacteria from a mixed population prior to subculturing (e.g., APW, Selenite F, Thioglycolate, Tetrathionate, Lim broth, GN broth).

Alkaline Peptone Water (APW)

An enrichment broth adjusted to $\text{pH } 8.4$ for Vibrio species prior to inoculation onto TCBS.

Gram Negative Broth (GN broth)

An enrichment and selective broth containing sodium citrate and sodium deoxycholate to inhibit Gram-positive organisms and enhance the growth of Salmonella and Shigella.

Enriched and Non-Selective Media

Solid media (such as BAP and CAP) containing additional supplements like blood, vitamins, or yeast extract to grow fastidious bacteria.

Gram-Positive Inhibitors in Selective Media

Chemical substances including Crystal/Gentian violet, Basic/Carbol Fuchsin, and Bile salts that inhibit Gram-positive organisms.

Gram-Negative Inhibitors in Selective Media

Chemical substances including Potassium tellurite and sodium azide that inhibit Gram-negative organisms.

Swarming Inhibitors in Selective Media

Substances such as alcohol and chloral hydrate added to selective media to inhibit swarming bacteria.

MacConkey Agar (MAC)

A differential culture medium for Gram-negative bacteria that differentiates lactose fermenters (pink colonies) from non-lactose fermenters (colorless colonies).

Eosin Methylene Blue (EMB) Agar

A differential medium where E. coli displays a metallic green sheen, while other lactose-fermenting bacteria form dark purple colonies.

Hektoen Enteric Agar (HEA)

A differential medium where Salmonella colonies produce bluish-green growth with a black center, while Shigella colonies appear green.

Lowenstein-Jensen (LJ) Medium

A protein-rich special medium containing whole eggs and malachite green that undergoes inspissation to isolate bacteria with special growth requirements.

Antimicrobial Removal Device (ARD)

Resin added to blood culture media to absorb antibiotics taken by the patient prior to blood collection.

Septi-chek System

A manual biphasic blood culture system composed of CAP and MAC.

BACTEC System

An automated blood culture system that detects microbial growth by measuring $\text{CO}_2$ production as a substrate.

Quality Control of Culture Media

Process of incubating sample preparations overnight at $35\,^\circ\text{C}$; media showing no growth is acceptable, whereas media showing growth is deemed contaminated and discarded.

Desiccation Viability of Neisseria gonorrhoeae

A Gram-negative diplococcus that remains viable for $1$\,hour in a dry environment and can withstand desiccation for only a month.

Desiccation Viability of Mycobacterium tuberculosis

An acid-fast bacillus with a waxy coat that remains viable for several months in a dry environment.

Desiccation Viability of Endospore-Forming Bacilli

Bacillus and Clostridium species remain viable for $10$\,years in a dry environment, with bacterial endospores capable of surviving for centuries.

Plasmolysis

The shrinkage of a bacterial cell in a hypertonic environment created by high concentrations of salts and sugars, which causes the cell to stop growing without dying.

Ionizing Radiation (Cold Sterilization)

Sterilization method using gamma rays ($1500$\,to\,$2500$) and x-rays that generates peroxide to cause DNA mutations, destroying vegetative cells and endospores; Bacillus pumilus is used as the biological indicator.

Non-Ionizing Radiation

Disinfection method using UV light, visible blue light, or microwaves that damages cellular DNA by producing thymine dimers to inhibit DNA replication.

Phenol (Tuberculocidal)

First widely used antiseptic/disinfectant that destroys plasma membranes and denatures proteins; used at a $5\%$ concentration for $10\text{--}30$\,mins against Mycobacteria.

Alcohol Disinfectant Requirements

Non-sporicidal bactericidal and fungicidal agent used in a $60\text{--}90\%$ concentration (where $30\%$ of the alcohol solution is water) with a contact time lasting until evaporation.

Sodium Hypochlorite (NaOCl)

A halogen disinfectant that destroys microorganisms via oxidation; must be prepared daily at a $1:10$ dilution with a contact time of $10\text{--}30$\,mins.

Iodine Antiseptic

An antiseptic that impairs protein synthesis and alters cell membranes, used primarily for skin disinfection and wound treatment with a contact time of $30\text{--}60$\,sec.