Recent Articles

Gelatin hydrolysis test: Principle, Procedure, Interpretation and preparation of nutrient gelatin medium

Gelatin hydrolysis is helpful in identifying and differentiating species of Bacillus, Clostridium, Proteus, Pseudomonas, and Serratia.  It also distinguishes the gelatinase-positive, pathogenic Staphylococcus aureus from the gelatinase-negative, non-pathogenic S. epidermidis . Gram-positive, spore-forming, rodshaped, aerobic or anaerobic bacteria such as Bacillus anthracis, Bacillus cereus, Bacillus subtilis, Clostridium perfringens and Clostridium tetani, are also positive for […]

Hippurate hydrolysis test

Hippurate hydrolysis test can be used for presumptive identification of Gardnerella vaginalis, Campylobacter jejuni, Listeria monocytogenes and group B streptococci. Principle of Hippurate hydrolysis test Hippurate hydrolysis test is used to detect the ability of bacteria to hydrolyse hippurate into glycine and benzoic acid by action of hippuricase enzyme present in bacteria. Previously, it was tested using ferric chloride […]

Introduction to Human Papiloma VIrus

Human papillomavirus (HPV) is a virus that infects the skin, genital area and lining of the cervix. There are about 100 different types of papilloma viruses (Some types of papillomaviruses cause warts on the skin, some types cause warts in the anal and genital areas, and some types cause cervical cancer.) Many different HPV types […]

Infections caused by anaerobes and features of anaerobic infections

Infections caused by anaerobic bacteria occur in all parts of body. These infected tissues usually contain a mixture of several kinds of anaerobes and frequently also contain aerobic and facultative bacteria. The types of infection commonly produced by anaerobic bacteria are as follows:  Intra-abdominal infections: Abscesses, post operative wound infections and generalized peritonitis produced by […]

Anaerobes: Why can’t anaerobic organism survive in presence of oxygen?

Anaerobes or anaerobic organisms are those that cannot grow in presence of oxygen. Oxygen is toxic for them so they must rely on other substances as terminal electron acceptor. Their metabolism is of fermentative type in which they reduce available organic compounds to various end products like organic acids and alcohols. The main reason behind […]

Urea hydrolysis/ Urease test (Christensen’s method)

Urea hydrolysis/Urease test is used to detect the ability of an organism to produce urease that hydrolyses urea contained in the medium. Hydrolysis of urea produces ammonia and carbon dioxide  The formation of ammonia makes the medium alkaline and the shift in pH is detected by the change of color of indicator phenol red from light […]

Triple Sugar Iron Agar test (TSI test): Principle, Procedure and Interpretation

Principle: Triple sugar iron agar test is used to determine whether gram negative bacilli utilize glucose and lactose or sucrose fermentatively and produce hydrogen sulfide (H2S).  It contains 10 parts of lactose: 10 parts of sucrose: 1 part of glucose and peptone.  Phenol red and ferrous sulphate serves as an indicator for acidification of medium […]