Loeffler Medium- Composition, Principle, Preparation, Results, Uses


Loeffler medium is a special substance used to grow and identify certain types of bacteria, especially Corynebacterium diphtheriae, the causative agent of diphtheria. Diphtheria is a serious infection of the respiratory tract and skin that can cause severe complications and death if left untreated. Loeffler medium helps to confirm the diagnosis of diphtheria by enhancing the growth and morphological characteristics of C. diphtheriae.

Loeffler medium was developed by Friedrich Loeffler in 1887, who was a German bacteriologist and one of the discoverers of C. diphtheriae. He devised a culture medium containing horse serum, beef extract, dextrose, and proteose peptones, which provided the nutrients and conditions necessary for the cultivation of corynebacteria. Later, the medium was modified by other researchers to improve its performance and utility.

Loeffler medium has several advantages and applications in microbiological investigations. Some of them are:

  • It enhances the formation of metachromatic granules within the cells of C. diphtheriae, which are characteristic structures that can be seen under a microscope with a special stain called Loeffler`s methylene blue. The metachromatic granules are composed of polyphosphate granules that store energy and phosphate for the bacteria. The presence of these granules helps to differentiate C. diphtheriae from other corynebacteria and gram-positive bacilli.
  • It allows for the determination of proteolytic activity of microorganisms, which is the ability to break down proteins into smaller peptides and amino acids. Proteolysis is indicated by the appearance of colonies surrounded by a small crater of liquefied medium or liquefaction of the slant with the production of a putrid odor. Proteolysis is an important virulence factor for some pathogens, such as Clostridium perfringens, which causes gas gangrene.
  • It provides an excellent background for the detection and observation of colonial pigmentation, which is the production of colored substances by some microorganisms. Colonial pigmentation can be useful for identification and differentiation of some bacteria, such as Serratia marcescens, which produces a red pigment called prodigiosin.
  • It can be used for the detection of ascospores, which are spores produced by some fungi during sexual reproduction. Ascospores can be seen as black dots on the surface of the medium after heating and rupturing the slant. Ascospores are important for identification and classification of some fungi, such as Aspergillus and Penicillium.

In summary, Loeffler medium is a valuable tool for microbiologists to grow and identify certain bacteria and fungi, especially C. diphtheriae. It has been used for over a century and has contributed to the understanding and control of infectious diseases.