Study Set Content:
: It’s a liquid medium, used to increase the relative concentration of certain microbes before culturing them on a solid medium plate. It’s used as a broth medium and inhibits the growth of commensal species of microorganisms (those who live in close association with each other) in the clinical specimen
Enrichment media
It contains certain indicators like dyes or metabolic substrates in the medium composition which gives different colors to colonies of different microbial species when they utilize or react with these components.It allows the growth of more than one microorganism, however, the bacterial colonies are differentiated based on their color when a chemical change occurs in the indicator, such as neutral red, phenol red, methylene blue
Differential or indicator media
n blood agar, three types of blood cell lysis or hemolysis are observed: alpha, beta, and gamma hemolysis.[5] It allows the growth of many microorganisms, however, their ability to lyse blood cells differs, and this helps to distinguish the bacterial colonies. For example, S. pyogenes completely lyse blood cells (beta hemolysis), thus causing total clearing of the media around its colonies. S. pneumoniae partially lyse red blood cells, resulting in a greenish-colored medium, while gamma hemolytic microorganisms like Enterococcus faecalis, Staphylococcus saprophyticus, and Staphylococcus epidermidis, can’t lyse red blood cells, thus causing no color change in the medium.
BLOOD AGAR
The fermentation of mannitol by Staphylococcus aureus causes the media to change to yellow, however, coagulase-negative staphylococci that can’t cause fermentation to appear in pink.
Mannitol salts agar
It differentiates the gram-negative bacteria based on their lactose metabolism. The lactose fermenting bacteria, such as Escherichia coli, Klebsiella spp, Citrobacter, and Enterobacter forms pink-red colonies, while lactose non-fermenters, like Salmonella, Shigella, Proteus, Providencia, Pseudomonas, and Morganella form pale or colorless colonies
MacConkey agar
he media contain sucrose, which is utilized by ferment microbes and helps to distinguish them from non-ferment microorganisms. Based on this characteristic, different colored bacterial colonies are formed on the media that help to identify and distinguish them from each other. For example, V. cholerae ferment the sucrose and form slightly flattened yellow colonies having opaque centers and translucent peripheries. Whereas, V. parahaemolyticus can’t ferment the sucrose and forms green to blue-green colonies
Thiosulfate citrate bile salts sucrose (TCBS) agar
are useful for clinical specimens which are required to be transferred immediately to labs to maintain the viability of potential pathogens and to prevent overgrowth of commensals or contaminating microorganisms. Some of them are semi-solid in consistency, and examples includ
Transport media
It’s used to transport feces from patients suspected to be suffering from bacillary dysentery
Sach’s buffered glycerol saline
Fecal samples collected from suspected cholera patients are transported using these media
Cary Blair transport and Venkatraman Ramakrishnan media
A throat specimen containing Streptococci is transported using this medium.
Pike’s medium:
This media is for anaerobic bacteria which require low oxygen levels, extra nutrients, and reduced oxidation-reduction potential. It is supplemented with hemin and vitamin K nutrients and oxygen is removed by boiling it in a water bath and sealing it with paraffin film. Examples are: Thioglycollate broth and Robertson Cooked Meat (RCM) medium which is commonly used to grow Clostridium spp.
Anaerobic media:
It’s used for amino acids, vitamins, and antibiotics assays. For example, antibiotic assay media is used to determine the antibiotic potency of microorganisms.
ASSAY MEDIA
It’s used to store microorganisms for a longer period, examples are chalk cooked meat broth and egg saline medium.
STORAGE MEDIA
An aerobic,spore-forming, Gram-positive bacillus; the causative agent of anthrax in humans, cattle, swine, sheep, rabbits, guinea pigs, and mice; causes a cutaneous, respiratory, or gastrointestinal disease, depending on the portal of entry
Bacillus anthracis
Anaerobic, Gramnegative bacilli; common members of the indigenous microflora of the oral cavity, gastrointestinal tract, and vagina; opportunistic pathogens that cause various infections, including appendicitis, peritonitis, abscesses, and postsurgical wound infections
Bacteroides
A fastidious, Gram-negative coccobacillus; the causative agent of whooping cough, which is also called pertussis
Bordetella pertussis
.A Gram-negative, loosely coiled spirochete; the causative agent of Lyme disease; transmitted from infected deer and mice to humans by tick bite
Borrelia burgdorferi
.A curved, Gram-negative bacillus, having a characteristic corkscrew-like motility; often seen in pairs (described as a gull-wing morphology because a pair of curved bacilli resembles a bird); microaerophilic and capnophilic; a common cause of gastroenteritis with malaise, myalgia, arthralgia, headache, and cramping abdominal pain.
Campylobacter jejuni
Pleomorphic, Gram-negative bacteria that are obligate intracellular pathogens; unable to grow on artificial media; etiologic agents of nongonococcal urethritis (NGU), trachoma, inclusion conjunctivitis, lymphogranuloma venereum, pneumonia, and psittacosis (ornithosis); different serotypes cause different diseases.
Chlamydia
An anaerobic, spore-forming, Grampositive bacillus; common in soil; produces a neurotoxin called botulinum toxin, which causes botulism, a very serious and sometimes fatal type of food poisoning
Clostridium botulinum
