Page 5 – Microbiology Info.com

Biochemical Test and Identification of Pseudomonas aeruginosa

Characteristics Pseudomonas aeruginosa Gram Staining Negative Shape (Cocci/Diplococci/Rods) Rods Motility (Motile / Non-Motile) Motile (Unipolar) Capsule (Capsulated/Non-Capsulated) Non-Capsulated Spore (Sporing/Non-Sporing) Non-Sporing Flagella (Flagellated/Non-Flagellated) Single Flagella Catalase Positive (+ve) Oxidase Positive (+ve) MR Negative (-ve) VP Negative (-ve) OF (Oxidative/Fermentative) Oxidative Indole Negative (-ve) Citrate Positive … Read more

Urease Test- Principle, Media, Procedure and Result

Urea Agar was developed by Christensen in 1946 for the differentiation of enteric bacilli. The urease test is used to determine the ability of an organism to split urea, through the production of the enzyme urease. Principle of Urease Test Urea is the product of decarboxylation … Read more

Citrate Utilization Test- Principle, Media, Procedure and Result

Result Interpretation of Citrate Utilization Test

This test is among a suite of IMViC Tests (Indole, Methyl-Red, Vogues-Proskauer, and Citrate) that are used to differentiate among the Gram-Negative bacilli in the family Enterobacteriaceae. Principle of Citrate Utilization Test Citrate agar is used to test an organism’s ability to utilize citrate as a source … Read more

Voges–Proskauer (VP) Test- Principle, Reagents, Procedure and Result

Result Interpretation of Voges–Proskauer (VP) Test

Voges and Proskauer, in 1898, first observed the production of a red color after the addition of potassium hydroxide to cultures grown on specific media. Harden later revealed that the development of the red color was a result of acetyl-methyl carbinol production. In 1936 Barrit … Read more

Methyl Red (MR) Test- Principle, Procedure and Result Interpretation

The methyl red (MR) test detects the production of sufficient acid during the fermentation of glucose and the maintenance of conditions such that the pH of an old culture is sustained below a value of about 4.5, as shown by a change in the color … Read more

Indole Test- Principle, Reagents, Procedure, Result Interpretation and Limitations

This test demonstrate the ability of certain bacteria to decompose the amino acid tryptophane to indole, which accumulates in the medium. Indole production test is important in the identification of Enterobacteria. Most strains of E. coli, P. vulgaris, P. rettgeri, M. morgani and Providencia species break down the … Read more

Sabouraud Dextrose Agar (SDA) – Composition, Principle, Uses, Preparation and Colony Morphology

Sabouraud Dextrose Agar (SDA) is used for the isolation, cultivation, and maintenance of non-pathogenic and pathogenic species of fungi and yeasts. SDA was formulated by Sabouraud in 1892 for culturing dermatophytes. The pH is adjusted to approximately 5.6 in order to enhance the growth of fungi, especially dermatophytes, … Read more

Cetrimide Agar- Composition, Principle, Uses, Preparation and Colony Morphology

Cetrimide Agar is a selective and differential medium used for the isolation and identification of Pseudomonas aeruginosa from clinical and non-clinical specimens. Cetrimide is the selective agent and inhibits most bacteria by acting as a detergent ( Cetyltrimethylammonium bromide, a quaternary ammonium, cationic detergent). It is also known as … Read more

Mueller Hinton Agar (MHA) – Composition, Principle, Uses and Preparation

Mueller and Hinton developed Mueller Hinton Agar (MHA) in 1941 for the isolation of pathogenic Neisseria species. Nowadays, it is more commonly used for the routine susceptibility testing of non-fastidious microorganism by the Kirby-Bauer disk diffusion technique. Five percent sheep blood and nicotinamide adenine dinucleotide may also … Read more

Biochemical Test and Identification of Enterococcus faecalis

Characteristics Enterococcus faecalis Gram Staining Positive Shape (Cocci/Diplococci/Rods) Cocci Motility (Motile / Non-Motile) Non-Motile Capsule (Capsulated/Non-Capsulated) – Spore (Sporing/Non-Sporing) Non-Sporing Flagella (Flagellated/Non-Flagellated) – Catalase Negative (-ve) Oxidase Negative (-ve) MR – VP Positive (+ve) OF (Oxidative/Fermentative) – Indole Negative (-ve) Citrate Negative (-ve) Urease Negative … Read more

Differences between DNA and RNA

Here are 17 differences between DNA and RNA. S.N. DNA RNA 1. DNA stands for Deoxyribonucleic Acid. The sugar portion of DNA is 2-Deoxyribose. RNA stands for Ribonucleic Acid. The sugar portion of RNA is Ribose. 2. The helix geometry of DNA is of B-Form … Read more

Differences between Enzymes and Hormones

Enzymes are the biological catalyst which speed up the rate of biochemical reactions without undergoing any changes. Hormones are molecules, usually a peptide (eg: insulin) or steroid (eg: estrogen) that is produced in one part of an organisms and triggers a specific cellular reactions in … Read more

String test for the identification of Vibrio cholerae

Vibrio cholerae is a gram-negative bacilli bacteria with a “comma” shaped body and a flagella for the movement. V. cholerae and V. mimicus are the only Vibrio spp. that do not require salt for growth. The string test may be performed on a glass microscope slide … Read more

Optochin Susceptibility Test for the identification of Streptococcus pneumoniae

Result Interpretaion of Optochin Susceptibility Test

Differentiation of Streptococcus pneumoniae from other viridans streptococci depends on demonstrating optochin susceptibility, bile solubility, reaction with a specific DNA probe, or detection of species-specific capsular polysaccharides. Most clinical microbiology laboratories today depend on the optochin susceptibility test. Although optochin susceptibility was first described for … Read more

Biochemical Test and Identification of Staphylococcus aureus

Basic Characteristics Properties (Staphylococcus aureus) Capsule Non-Capsulated Catalase Positive (+ve) Citrate Positive (+ve) Coagulase Positive (+ve) Gas Negative (-ve) Gelatin Hydrolysis Positive (+ve) Gram Staining Positive (+ve) H2S Negative (-ve) Hemolysis Positive (+ve)- Beta Indole Negative (-ve) Motility Negative (-ve) MR (Methyl Red) Positive (+ve) Nitrate … Read more

Biochemical Test and Identification of E. coli

Characteristics E. coli Gram Staining Negative Shape (Cocci/Diplococci/Rods) Rods Motility (Motile / Non-Motile) Motile Capsule (Capsulated/Non-Capsulated) Variable Spore (Sporing/Non-Sporing) Non-Sporing Flagella (Flagellated/Non-Flagellated) Flagellated Catalase Positive (+ve) Oxidase Negative (-ve) MR Positive (+ve) VP Negative (-ve) OF (Oxidative/Fermentative) Fermentative Indole Positive (+ve) Citrate Negative (-ve) Urease … Read more

Differences Between Thick Blood Smear and Thin Blood Smear

S.N. Thick Blood Smear Thin Blood Smear 1. Thick blood smears are most useful for detecting the presence of parasites. Thin blood smears helps to discover which species of parasite is causing the infection. 2. A thick blood smear is a drop of blood on … Read more

Xylose Lysine Deoxycholate (XLD) Agar- Principle, Uses, Composition, Preparation and Colony Characteristics

Shigella and Salmonella Colonies on XLD Agar

Xylose Lysine Deoxycholate (XLD) Agar is a selective medium for the isolation of Salmonella and Shigella spp from clinical specimens and food samples. XLD Agar was originally formulated by Taylor for the isolation and identification of Shigella from stool specimens. The pathogens are differentiated not only from the non-pathogenic lactose … Read more

Differences Between Bacteremia and Septicemia

Bacteremia is the simple presence of bacteria in the blood while Septicemia is the presence and multiplication of bacteria in the blood. Septicemia is also known as blood poisoning. S.N. Bacteremia Septicemia 1. Bacteremia is the simple presence of bacteria in the blood. Septicemia is … Read more

Potato Dextrose Agar (PDA)- Principle, Uses, Composition, Procedure and Colony Characteristics

Colony Characteristics on Potato Dextrose Agar (PDA)

Potato Dextrose Agar (PDA) is used for the cultivation of fungi. Potato Dextrose Agar (PDA) is a general purpose medium for yeasts and molds that can be supplemented with acid or antibiotics to inhibit bacterial growth. It is recommended for plate count methods for foods, … Read more

Oxidase Test- Principle, Uses, Procedure, Types, Result Interpretation, Examples and Limitations

The oxidase test detects the presence of a cytochrome oxidase system that will catalyse the transport of electrons between electron donors in the bacteria and a redox dye- tetramethyl-p-phenylene-diamine. The dye is reduced to deep purple color. This test is used to assist in the … Read more

Catalase Test- Principle, Uses, Procedure, Result Interpretation with Precautions

Result Interpretation of Catalase Test and Examples

This test demonstrate the presence of catalase, an enzyme that catalyses the release of oxygen from hydrogen peroxide (H2O2). It is used to differentiate those bacteria that produces an enzyme catalase, such as staphylococci, from non-catalase producing bacteria such as streptococci. Normally 3% H2O2 is … Read more

Coombs Test- Principle, Types, Procedure and Result Interpretation

Coombs test is also known as antiglobulin test. The Coombs test tests for antibodies that may stick to the red blood cells and cause red blood cells to die too early. It was discovered by Coombs, Mourant and Race in 1945. Coombs reagent is antihuman … Read more

Differences Between Diarrhea And Dysentery

Diarrhea is a condition that involves the frequent passing of loose or watery stools while Dysentery is an intestinal inflammation, especially in the colon, that can lead to severe diarrhea with mucus or blood in the feces. The major differences between Diarrhea and Dysentery are as … Read more

Germ Tube Test- Principle, Procedure, Results, Interpretation and Limitations

Germ Tube Test is a screening test which is used to differentiate Candida albicans from other yeast. Germ tube (GT) formation was first reported by Reynolds and Braude in 1956. When Candida is grown in human or sheep serum at 37°C for 3 hours, they … Read more

Widal Test- Introduction, Principle, Procedure, Interpretation and Limitation

Interpretation of Widal Test- Tube Method

Introduction of Widal Test Widal Test is an agglutination test which detects the presence of serum agglutinins (H and O) in patients serum with typhoid and paratyphoid fever. When facilities for culturing are not available, the Widal test is the reliable and can be of … Read more

Differences Between Plasmodium falciparum and Plasmodium vivax

Malaria parasites are sporozoans and belongs to order Haemosporida. The genus Plasmodium has been subdivided into nine subgenera, of which three are found in mammals, four in birds and two in lizards. According to the classification, Plasmodium vivax, Plasmodium ovale and Plasmodium malariae belong to the … Read more

Antigen- Properties, Types and Determinants of Antigenicity

Antigen is a substances usually protein in nature and sometimes polysaccharide, that generates a specific immune response and induces the formation of a specific antibody or specially sensitized T cells or both. Although all antigens are recognized by specific lymphocytes or by antibodies, only some … Read more

Techniques of Virus Cultivation

Viruses are obligate intracellular parasites so they depend on host for their survival. They cannot be grown in non-living culture media or on agar plates alone, they must require living cells to support their replication. The primary purpose of virus cultivation is: To isolate and … Read more

Differences Between Exotoxins and Endotoxins

Many bacteria produce toxins, enzymes and pigments. Toxins and enzymes play important role in pathogenecity. Toxins are of two types: Exotoxins are usually heat labile proteins secreted by certain species of bacteria which diffuse into the surrounding medium. Endotoxins are heat stable lipopolysaccharide-protein complexes which … Read more