CNA Agar

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Columbia Nalidixic Acid (CNA) agar is a growth medium used for the isolation and cultivation of bacteria from clinical and non-clinical specimens. CNA agar contains antibiotics (nalidixic acid and colistin) that inhibit Gram-negative organisms, aiding in the selective isolation of Gram-positive bacteria. [1] Gram-positive organisms that grow on the media can be differentiated on the basis of hemolysis.

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Uses

CNA agar is commonly used in clinical microbiology laboratories to isolate pathogenic Gram-positive bacteria such as Staphylococcus , Enterococcus , Streptococcus , diphtheroids, and Listeria from clinical specimens. [1] A common use for CNA agar is commonly used for the detection of Streptococcus agalactiae carriage in pregnant women. [2] It is also effective for the isolation of Gram-positive anaerobes when incubated under anaerobic conditions. [3]

CNA agar is supplemented with sheep blood to facilitate the growth of more fastidious Gram-positive organisms [4] such as Streptococcus and Enterococcus. The sheep blood allows for the presumptive identification of some species of bacteria on the basis of hemolysis. Beta hemolytic organisms such as Staphylococcus aureus and Streptococcus pyogenes will produce colonies surrounded with a clear zone. Alpha hemolytic organisms such as Streptococcus pneumoniae [5] and viridans streptococci will produce colonies surrounded by a light to dark green zone.

Although CNA agar is formulated to select for Gram-positive bacteria, microbiologists working with this media should be aware of its limitations. Gram-negative rods that are resistant to quinolones and polymyxins may grow on the media. [6] Additionally, Candida and other molds are not inhibited by the antibiotics. Gram-positive aerobic spore forming bacteria such as Bacillus are also usually inhibited by the media.[ citation needed ]

Contents

The addition of peptones into the agar provides the growth factors required by the bacteria to grow. [7] Casein also provides a source of amino acids for organisms with fastidious growth requirements such as Lactobacillus brevis. [8] It contains the antibiotics colistin and nalidixic acid which inhibit the growth of many gram-negative bacteria.[ citation needed ]

Composition

Source: [6]

History

CNA agar was developed by Ellner et al. at Columbia university in 1965 while trying to develop an agar base that would enhance the hemolysis of Streptococcus pyogenes. [9]

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In bacteriology, gram-positive bacteria are bacteria that give a positive result in the Gram stain test, which is traditionally used to quickly classify bacteria into two broad categories according to their type of cell wall.

<i>Streptococcus</i> Genus of bacteria

Streptococcus is a genus of gram-positive or spherical bacteria that belongs to the family Streptococcaceae, within the order Lactobacillales, in the phylum Bacillota. Cell division in streptococci occurs along a single axis, thus when growing they tend to form pairs or chains, which may appear bent or twisted. This differs from staphylococci, which divide along multiple axes, thereby generating irregular, grape-like clusters of cells. Most streptococci are oxidase-negative and catalase-negative, and many are facultative anaerobes.

<i>Enterococcus</i> Genus of bacteria

Enterococcus is a large genus of lactic acid bacteria of the phylum Bacillota. Enterococci are Gram-positive cocci that often occur in pairs (diplococci) or short chains, and are difficult to distinguish from streptococci on physical characteristics alone. Two species are common commensal organisms in the intestines of humans: E. faecalis (90–95%) and E. faecium (5–10%). Rare clusters of infections occur with other species, including E. casseliflavus, E. gallinarum, and E. raffinosus.

<span class="mw-page-title-main">Agar plate</span> Petri dish with agar used to culture microbes

An agar plate is a Petri dish that contains a growth medium solidified with agar, used to culture microorganisms. Sometimes selective compounds are added to influence growth, such as antibiotics.

<i>Gardnerella vaginalis</i> Species of bacterium

Gardnerella vaginalis is a species of Gram-variable-staining facultative anaerobic bacteria. The organisms are small non-spore-forming, nonmotile coccobacilli.

<span class="mw-page-title-main">Microbiological culture</span> Method of allowing microorganisms to multiply in a controlled medium

A microbiological culture, or microbial culture, is a method of multiplying microbial organisms by letting them reproduce in predetermined culture medium under controlled laboratory conditions. Microbial cultures are foundational and basic diagnostic methods used as research tools in molecular biology.

<i>Erysipelothrix rhusiopathiae</i> Species of pathogenic bacterium

Erysipelothrix rhusiopathiae is a Gram-positive, catalase-negative, rod-shaped, non-spore-forming, nonacid-fast, nonmotile bacterium. Distributed worldwide, E. rhusiopathiae is primarily considered an animal pathogen, causing the disease known as erysipelas that may affect a wide range of animals. Pigs, turkeys and laying hens are most commonly affected, but cases have been reported in other mammals, birds, fish, and reptiles. In pigs, the disease is known as diamond skin disease. The bacterium can also cause zoonotic infections in humans, called erysipeloid. The human disease called erysipelas is not caused by E. rhusiopathiae, but by various members of the genus Streptococcus.

<span class="mw-page-title-main">Growth medium</span> Solid, liquid or gel used to grow microorganisms or cells

A growth medium or culture medium is a solid, liquid, or semi-solid designed to support the growth of a population of microorganisms or cells via the process of cell proliferation or small plants like the moss Physcomitrella patens. Different types of media are used for growing different types of cells.

<span class="mw-page-title-main">MacConkey agar</span> Differential media

MacConkey agar is a selective and differential culture medium for bacteria. It is designed to selectively isolate gram-negative and enteric bacteria and differentiate them based on lactose fermentation. Lactose fermenters turn red or pink on MacConkey agar, and nonfermenters do not change color. The media inhibits growth of gram-positive organisms with crystal violet and bile salts, allowing for the selection and isolation of gram-negative bacteria. The media detects lactose fermentation by enteric bacteria with the pH indicator neutral red.

<i>Elizabethkingia meningoseptica</i> Species of bacterium

Elizabethkingia meningoseptica is a Gram-negative, rod-shaped bacterium widely distributed in nature. It may be normally present in fish and frogs; it may be isolated from chronic infectious states, as in the sputum of cystic fibrosis patients. In 1959, American bacteriologist Elizabeth O. King was studying unclassified bacteria associated with pediatric meningitis at the Centers for Disease Control and Prevention in Atlanta, when she isolated an organism that she named Flavobacterium meningosepticum. In 1994, it was reclassified in the genus Chryseobacterium and renamed Chryseobacterium meningosepticum(chryseos = "golden" in Greek, so Chryseobacterium means a golden/yellow rod similar to Flavobacterium). In 2005, a 16S rRNA phylogenetic tree of Chryseobacteria showed that C. meningosepticum along with C. miricola were close to each other but outside the tree of the rest of the Chryseobacteria and were then placed in a new genus Elizabethkingia named after the original discoverer of F. meningosepticum.

<span class="mw-page-title-main">Thayer–Martin agar</span> Culture medium used in microbiology

Thayer–Martin agar is a Mueller–Hinton agar with 5% chocolate sheep blood and antibiotics. It is used for culturing and primarily isolating pathogenic Neisseria bacteria, including Neisseria gonorrhoeae and Neisseria meningitidis, as the medium inhibits the growth of most other microorganisms. When growing Neisseria meningitidis, one usually starts with a normally sterile body fluid, so a plain chocolate agar is used. Thayer–Martin agar was initially developed in 1964, with an improved formulation published in 1966.

<span class="mw-page-title-main">Mueller–Hinton agar</span> Culture medium used in microbiology

Mueller Hinton agar is a type of growth medium used in microbiology to culture bacterial isolates and test their susceptibility to antibiotics. This medium was first developed in 1941 by John Howard Mueller and Jane Hinton, who were microbiologists working at Harvard University. However, Mueller Hinton agar is made up of a couple of components, including beef extract, acid hydrolysate of casein, and starch, as well as agar to solidify the mixture. The composition of Mueller Hinton agar can vary depending on the manufacturer and the intended use, but the medium is generally nutrient-rich and free of inhibitors that could interfere with bacterial growth.                                

<i>Streptococcus zooepidemicus</i> Species of bacterium

Streptococcus zooepidemicus is a Lancefield group C streptococcus that was first isolated in 1934 by P. R. Edwards, and named Animal pyogens A. It is a mucosal commensal and opportunistic pathogen that infects several animals and humans, but most commonly isolated from the uterus of mares. It is a subspecies of Streptococcus equi, a contagious upper respiratory tract infection of horses, and shares greater than 98% DNA homology, as well as many of the same virulence factors.

<i>Streptococcus iniae</i> Species of bacterium

Streptococcus iniae is a species of Gram-positive, sphere-shaped bacterium belonging to the genus Streptococcus. Since its isolation from an Amazon freshwater dolphin in the 1970s, S. iniae has emerged as a leading fish pathogen in aquaculture operations worldwide, resulting in over US$100M in annual losses. Since its discovery, S. iniae infections have been reported in at least 27 species of cultured or wild fish from around the world. Freshwater and saltwater fish including tilapia, red drum, hybrid striped bass, and rainbow trout are among those susceptible to infection by S. iniae. Infections in fish manifest as meningoencephalitis, skin lesions, and septicemia.

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Lancefield grouping is a system of classification that classifies catalase-negative Gram-positive cocci based on the carbohydrate composition of bacterial antigens found on their cell walls. The system, created by Rebecca Lancefield, was historically used to organize the various members of the family Streptococcaceae, which includes the genera Lactococcus and Streptococcus, but now is largely superfluous due to explosive growth in the number of streptococcal species identified since the 1970s. However, it has retained some clinical usefulness even after the taxonomic changes, and as of 2018, Lancefield designations are still often used to communicate medical microbiological test results.

<span class="mw-page-title-main">New York City agar</span>

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<i>Streptomyces antibioticus</i> Species of bacterium

Streptomyces antibioticus is a gram-positive bacterium discovered in 1941 by Nobel-prize-winner Selman Waksman and H. Boyd Woodruff. Its name is derived from the Greek "strepto-" meaning "twisted", alluding to this genus' chain-like spore production, and "antibioticus", referring to this species' extensive antibiotic production. Upon its first characterization, it was noted that S. antibioticus produces a distinct soil odor.

<span class="mw-page-title-main">Granada medium</span>

Granada medium is a selective and differential culture medium designed to selectively isolate Streptococcus agalactiae and differentiate it from other microorganisms. Granada Medium was developed by Manuel Rosa-Fraile et al. at the Service of Microbiology in the Hospital Virgen de las Nieves in Granada (Spain).

In microbiology, the term isolation refers to the separation of a strain from a natural, mixed population of living microbes, as present in the environment, for example in water or soil, or from living beings with skin flora, oral flora or gut flora, in order to identify the microbe(s) of interest. Historically, the laboratory techniques of isolation first developed in the field of bacteriology and parasitology, before those in virology during the 20th century.

<span class="mw-page-title-main">Colonial morphology</span> Examination of microbial colonies

In microbiology, colonial morphology refers to the visual appearance of bacterial or fungal colonies on an agar plate. Examining colonial morphology is the first step in the identification of an unknown microbe. The systematic assessment of the colonies' appearance, focusing on aspects like size, shape, colour, opacity, and consistency, provides clues to the identity of the organism, allowing microbiologists to select appropriate tests to provide a definitive identification.

References

  1. 1 2 Atlas, R M; Snyder, J W (2011). "Reagents, Stains, and Media: Bacteriology". In Versalovic, James; American Society for Microbiology (eds.). Manual of clinical microbiology (10th ed.). Washington, DC: ASM Press. ISBN   978-1-55581-463-2. OCLC   657027913.
  2. ↑ El Aila, Nabil A; Tency, Inge; Claeys, Geert; Saerens, Bart; Cools, Piet; Verstraelen, Hans; Temmerman, Marleen; Verhelst, Rita; Vaneechoutte, Mario (Dec 2010). "Comparison of different sampling techniques and of different culture methods for detection of group B streptococcus carriage in pregnant women". BMC Infectious Diseases. 10 (1): 285. doi: 10.1186/1471-2334-10-285 . ISSN   1471-2334. PMC   2956727 . PMID   20920213.
  3. ↑ Baron, E J; Thomson, R B (2011). "Specimen Collation, Transport, and Processing: Bacteriology". In Versalovic, James; American Society for Microbiology (eds.). Manual of clinical microbiology (10th ed.). Washington, DC: ASM Press. ISBN   978-1-55581-463-2. OCLC   657027913.
  4. ↑ Golberg, R L; Washington JA, I I (Sep 1976). "Comparison of isolation of Haemophilus vaginalis (Corynebacterium vaginale) from peptone-starch-dextrose agar and Columbia colistin-nalidoxic acid agar". Journal of Clinical Microbiology. 4 (3): 245–247. doi:10.1128/jcm.4.3.245-247.1976. ISSN   0095-1137. PMC   274444 . PMID   1085777.
  5. ↑ McDevitt, Erin; Khan, Faidad; Scasny, Anna; Thompson, Courtney D.; Eichenbaum, Zehava; McDaniel, Larry S.; Vidal, Jorge E. (2020-12-23). Johnson, Michael David Leslie (ed.). "Hydrogen Peroxide Production by Streptococcus pneumoniae Results in Alpha-hemolysis by Oxidation of Oxy-hemoglobin to Met-hemoglobin". mSphere. 5 (6). doi:10.1128/mSphere.01117-20. ISSN   2379-5042. PMC   7729260 . PMID   33298575.
  6. 1 2 Remel (Oct 2011). "Columbia CNA Agar w/ 5% Sheep Blood" (PDF).
  7. ↑ Manual of Microbiological Culture Media (Technical report). Becton, Dickinson, and Company. 2009. 161-2.
  8. ↑ Bonnet, M.; Lagier, J.C.; Raoult, D.; Khelaifia, S. (Mar 2020). "Bacterial culture through selective and non-selective conditions: the evolution of culture media in clinical microbiology". New Microbes and New Infections. 34: 100622. doi:10.1016/j.nmni.2019.100622. PMC   6961714 . PMID   31956419.
  9. ↑ Ellner, PD; Stoessel, CJ; Drakeford, E; Vasi, F (April 1966). "A new culture medium for medical bacteriology". Am J Clin Pathol. 45 (4): 502–4. doi:10.1093/ajcp/45.4_ts.502. PMID   5325709 . Retrieved 13 March 2023.
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