Loffler's medium is?
Ans. D. Enriched medium.Enriched mediumThe media containing ingredients which enhance their growth-promoting qualities are enriched media e.g. blood agar, chocolate agar and Loeffler medium.The usual media employed for cultivation of the diphtheria bacillus are Loeffler's serum slope and tellurite blood agar.Diphtheria bacilli grow on Loeffler's serum slope very rapidly and colonies can be seen in 6-8 hours, long before the other bacteria grow.TYPES OF Bacteriological Media MediaCommente.g.1.Ordinary culture mediaThese are routinely employed in a laboratorye.g. nutrient broth, nutrient agar, infusion broth and lysate media.2.Enriched mediaCertain organisms do not grow on ordinary nutrient media. They require growth- promoting ingredients such as blood, glucose, serum, egg, etc. The media containing ingredients which enhance their growth- promoting qualities are enriched mediae.g. blood agar, chocolate agar and Loeffler medium.3.Enrichment mediaEnrichment media are liquid media containing chemical constituents which inhibit some normal flora and allow pathogens which may be present in very small number in the specimen, to grow unhampered and thus enriching them. Isolated colonies of these organisms may be obtained by subculturing onto solid media.An example of enrichment media is selenite F broth used for primary isolation of enteric bacteria.4.Differential/ Indicator mediaDifferential media have got some chemical constituents which characterize different bacteria by their special colonial appearances in the culture e.g. MacConkey agar contains lactose as a substrate and neutral red as an indicator. Bacteria fermenting lactose produce acid and this will change the colour of the indicator and thus the colonies will turn red. The red lactose fermenting colonies can be differentiated from the pale non-lactose fermenting colonies.1. Eosin methylene blue (EMB), which is differential for lactose and sucrose fermentation2. MacConkey (MCK), which is differential for lactose fermentation3. mannitol salt agar (MSA), which is differential for mannitol fermentation4. X-gal plates, which are differential for lac operon mutants5. Selective mediaSelective media will selectively permit the growth of pathogens and inhibit the commensals. In addition, it may differentiate the pathogen from commensals that grow by the colour and opacity of the coloniese.g. blood tellurite medium for C. diphtheriae.Buffered charcoal yeast extract agar, which is selective for certain gram-negative bacteria, especially Legionella pneumophila6. Transport mediaTransport media are also frequently used to sustain the viability of organisms when a clinical specimen is to be transported from the periphery to laboratory.The transport medium prevents the outgrowth of contaminants during transit and sustains the pathogen.Cary and Blair and Stuart media.Venkat-Ramakrishnan(VR) medium for v. cholerae.Thioglycolate broth for strict anaerobes.Loeffler MediaIt is primarily used for the isolation of Corynebacterium diphtheriae from clinical specimens. It is also used to determine the proteolytic activity and pigment production of various microorganisms.PRINCIPLE:Recovery is further enhanced when Loeffler Media is used in combination with Potassium Tellurite CystineAgar Media and blood agar. On Loeffler Media, C. diphtheriae produces characteristic metachromatic granules that can be detected by staining with methylene blue; it also demonstrates the characteristic Chinese-letter formation which is due to the cells snapping off when they divide. With the above information, a presumptive identification can result in 16-18 hours. Loeffler Media enhances the demonstration of the organism's natural morphological and physiological characteristics, i.e. pigmentation.FORMULA: Approximate, per 250 ml of deionized filtered water.Loeffler Media: Beef Extract..................................0.75 gDextrose.......................................1.25Sodium Chloride.............................1.25Proteose Micro Peptone....................2.50Horse Serum.................................750.00 mlInterpretation:Corynebacterium diphtheriae BiotypesMetachromatic GranulesMorphologyMitisIntensely stainedLong, pleomorphic but rigid rodsintermediusCells frequently swollen with terminal granules Irregularly barredHighly pleomorphic with very long and short rodsgravisNo granules but alternate bands of light and dark blueShort rods with many cocci of pear-shaped formsAdditional Educational points:Stains1Congo redAmyloid; apple-green birefringence in polarized light (because of a-pleated sheets).2Giemsa'sBorrelia, Plasmodium, trypanosomes, Chlamydia.3PAS (periodic acid-Schiff)Stains glycogen, mucopolysaccharides; used to diagnose Whipple's disease.4Ziehl-NeelsenAcid-fast bacteria.5India inkCryptococcus neoformans.6Silver stainFungi, PCP, Legionella.
Indicator medium
Selective medium
Enrichment medium
Enriched medium
General