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WEEK 7 BACT LAB
CULTIVATION OF BACTERIA
| Question | Answer |
|---|---|
| This is the process of growing microorganisms in culture by taking bacteria from the infection site | Cultivation |
| NUTRITIONAL NEEDS | Bacteria with special nutritional or environmental requirements are said to be fastidious while; The nutritional needs of most clinically important bacteria are relatively basic and straightforward. These bacteria are considered non-fastidious |
| This is a semisolid media that contains a small percentage of agar that allows to grow anaerobic bacteria; provides an indication of the type of organism present based on oxygen requirements | Thioglycollate broth |
| List the amount of growth present and the location of growth within the broth based on oxygen requirements | Strict anaerobes will grow at the bottom of the broth tube. Anaerobes will grow near the surface. Microaerophilic organisms require oxygen and will grow slightly below the surface. Microaerobic & facultative anaerobes and aerotolerant organisms |
| This is the most common solidifying agent melting at high temperatures (95°C) but resolidifying after the temperature falls below 50°C | Agarose |
| This refer to as all bacterial cells within a single colony are the same genus and species, having identical genetic and phenotypic characteristics | Pure colony |
| It contain growth enhancers that are added to nonselective agar to allow fastidious organisms to flourish; enhance the growth of a particular bacterial pathogen from a mixture of organisms by providing specific nutrients for the organism’s growth | Enriched media |
| It is a liquid medium designed to encourage the growth of small numbers of a particular organism while suppressing other flora present (contaminating organism) | Enrichment broth |
| support the growth of a wide range of microorganisms and are considered nonselective because, theoretically, the growth of most organisms is supported; thus that support growth of most non-fastidious organisms | Nutritive media |
| This medium support the growth of one group of organisms but not another by adding one or more agents like antimicrobials, dyes, or alcohol to a particular medium that are all inhibitory to all organisms | Selective media |
| This is a broth media which can be used as a supplement to agar plates to detect small numbers of most aerobes, anaerobes, and microaerophiles and may also contain specific nutrients and may include selective properties to prevent the growth of contaminat | Supplemental broth media/Back-up broths/Enriched broth |
| This allows colonies of one bacterial species or type to exhibit certain metabolic or culture characteristics that can be used to distinguish them from other bacteria growing on the same agar plate. | Differential media |
| Why does sheep Blood Agar (BA) is considered to be nutritive and differential media and the most commonly used nutritive media ? | Blood agar is considered both a nutritive and differential medium because it differentiates organisms based on whether they are alpha (a)-, beta (b)-, or gamma (g)-hemolytic and certain bacteria produce extracellular enzymes that lyse red blood cells in |
| This broth is used to enhance the growth of group B streptococci and gram negative broth for the selective enrichment of enteric (GN) | LIM Broth (Todd Hewitt) |
| These are considered to be a back up broth/supplemental broth that supports growth of anaerobes, aerobes, microaerophilic, and fastidious microorganisms | Thioglycollate (thio) broth, brain-heart infusion broth (BHIB), and tryptic soy broth (TSB) |
| This agar is frequently used as the primary selective and differential agar for the isolation and differentiation of GN bacilli. is considered to be a selective media that contains the dye crystal violet, which inhibits gram-positive organisms. | MacConkey agar (MAC) |
| This agar is allowing gram positive bacteria to grow | Columbia agar with colistin and nalidixic acid (CNA) |
| This agar medium is used to identify aerobic gram-positive cocci and bacilli and anaerobic gram-positive cocci | Phenylethyl alcohol (PEA) |
| These medium are used for enteric gram-negative bacilli for most routine bacterial cultures | Selective and Differential media |
| It may be used as a supplement with specimens from sterile body fluids, tissues, lesions, wounds, and abscesses | Broth media |
| This agar medium supports growth for all but the most fastidious clinically significant bacteria thus cultivation for non-fastidious organisms and a determination for hemolytic reaction. | Blood agar (BA) |
| This a nutritionally rich medium with or without added blood; and a major component of the media developed for culturing a PX blood for bacteria & cultivation of fastidious and non-fastidious organisms | Brain Heart Infusion (BHI) agar or broth |
| This an enriched agar that is essentially the same with BA except that during preparation the red blood cells are lysed (Heme/X factor) when added to molten agar base; common for Neisseria gonorrhoeae | Chocolate Agar |
| This agar allows many types of GN bacilli to grow. Bacterial fermentation of lactose appears as dark purple to black, or with a green metallic sheen. Non–lactose-fermenters, such as Shigella spp., remain colorless and translucent | Eosin Methylene Blue Agar, Levine (EMB) |
| This agar used for the Selective (enrichment) liquid medium for enteric cultivation of gastrointestinal pathogens (i.e., Salmonella spp. and Shigella spp.) from stool specimens and rectal swabs | Gram Negative Broth (GN) |
| This agar is allowing Salmonella spp. and Shigella spp. to grow as a Differential, selective medium. | Hektoen Enteric Agar (HE) |
| This agar is for identification of Shigella spp. and Salmonella spp. | Xylose-Lysine-Deoxycholate Agar (XLD) |
| This agar is a Selective for N. gonorrhoeae and N. meningitidis. Supports the growth of Francisella and Brucella spp. | Modified Thayer-Martin agar (MTM) |
| Why does Eosin Methylene Blue Agar, Levine (EMB) considered to be both selective and differential agar? | Because this medium contains eosin Y and methylene blue dye to inhibit the growth of gram-positive bacteria. Lactose fermenters (dark purple to black/green metallic sheen). Non–lactose-fermenters, such as Shigella spp., remain colorless and translu |
| Why does Hektoen Enteric Agar (HE) considered to be both selective and differential agar? | Because HE agar contains bile salts and dyes (bromothymol blue and acid fuchsin) to selectively slow the growth of most nonpathogenic GN bacilli Differential because because many nonenteric pathogens that do grow will appear as orange to salmon-colored |
| Why does McConkey (MAC) considered to be selective and differential medium? | Because the media will not allow most gram-positive bacteria to grow cause by crystal violet dye to inhibit the bacteria Differentiates between GN bacteria that can and cannot ferment the sugar lactose cause by pH indicator neutral red |
| Why does sheep blood agar (BA) considered to be differential? | Because the appearance of colonies produced by certain bacterial species is distinguishable based on the hemolytic patterns of the organisms. |
| Why does Modified Thayer-Martin agar (MTM) considered to be enrichment and selective medium? | Because Thayer-Martin agar, which improves growth of the fastidious organisms Additional antibiotics may be included in other formulas including colistin to inhibit other GN bacteria, vancomycin to inhibit gram-positive bacteria, and nystatin to inhibi |
| Why does Gram Negative Broth (GN) considered to be Selective (Enrichment) liquid medium? | Because it contain sodium citrate and sodium deoxycholate (a bile salt) that inhibit gram-positive organisms and the early multiplication of GN |
| Why does Columbia Colistin-Nalidixic Acid With Blood (CNA) Agar considered to be Selective medium? | Because Columbia colistin-nalidixic acid (CNA) refers to the antibiotics colistin (C) and NA that are added to the medium to suppress the growth of most GN organisms |
| Why does Phenylethyl Alcohol Agar (PEA) considered to be Selective medium? | Because 5% sheep blood, inhibits the growth of aerobic and facultatively anaerobic GN rods |
| Why does Xylose-Lysine-Deoxycholate Agar (XLD) considered to be selective and differential medium? | Because the salt, sodium deoxycholate, inhibits many GN bacilli that are not enteric pathogens and inhibits gram positive organisms A phenol red indicator in the medium detects increased acidity from carbohydrate; Shigella colorless, Salmonella yellow |
| List 4 types of streak techniques | Quadrant Streak (Method A & B), Radiant Streak, Continuous Streak |
| The timing of autoclave sterilization should start from the moment the temperature reaches ____ and usually requires a minimum of ____ | 121C & 15 minutes |
| Once the sterilization cycle is completed, molten agar is allowed to cool to approximately ____ before being distributed to individual petri plates _____________ | 50C & approximately 20 to 25 mL of molten agar per plate |
| If other ingredients are to be added (e.g., supplements such as sheep blood or specific vitamins, nutrients, or antibiotics), the broth should be incorporated after the appropriate time of sterilization. | FALSE, molten agar should be cool down first just before distribution to plates |
| Membrane filters with pores ranging in size from ____ to ____ | 0.2 to 0.45 μm |
| This methods involve characterization of some portion of a bacterium’s genome using molecular methods for DNA or RNA analysis; involves detecting the presence of a gene | Genotypic identification |
| The presence of a specific gene or a particular nucleic acid sequence unique to the organism is interpreted to as? | Definitive identification of the organism |
| This refers to the percentage of patients without disease that will test negative for the presence of the organism | Specificity |
| This indicates the percentage of patients in whom the organism is present who actually test positive. | Sensitivity |
| This method are based on observable physical or metabolic characteristics of bacteria—that is, identification is through analysis of gene products rather than through the genes themselves. | Phenotypic criteria |
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