Recent Articles

Virulence factors of Pseudomonas aeruginosa

Alginate: It is a capsular polysaccharide that allows the infecting bacteria to adhere to lung epithelial cell surface and form biofilms which protects the bacteria from antibiotics and body’s immune system. Pilli: It is a surface appendage that allow adherence of the bacteria to GM -1 ganglioside receptor on host epithelial surface Neuraminidase: It removes […]

D test- A test for detection of inducible Clindamycin resistance in Staphylococcus aureus

D-test  detects inducible clindamycin resistance in Staphylococcus aureus by double disk diffusion using Clindamycin(2ug) and Erythromycin (15 ug) disks. Erythromycin is a macrolide and clindamycin is a lincosamide, two distinct classes of antimicrobial agents that inhibit protein synthesis by binding to the 50S ribosomal subunits of bacterial cells. Resistance in Staphylococcus can occur to both of these antimicrobial […]

ONPG (o-Nitrophenyl-β-D-Galactopyranoside) test: Principle, Procedure, Result and Interpretation

Principle: o-Nitrophenyl-β-D-Galactopyranoside (ONPG) is structurally similar to lactose except that o-nitrophenol has been substituted for glucose. On hydrolysis through the action of enzyme β-galactosidase, ONPG which is a colorless compound cleaves into two residues, galactose and o-nitrophenol which is yellow in color. Development yellow color provides visual evidence of hydrolysis of ONPG. Views – 7779 […]

Superoxol Test: Rapid presumptive test for Neisseria gonorrhoea (Gonococcus)

Superoxol test is a rapid test that can be used for presumptive identification of Neisseria gonorrhoea. It is similar to Catalase test in which 3% hydrogen peroxide (H2O2) solution is used but 30% hydrogen peroxide is used in this test. N. gonorrhoeae strains produce immediate, vigorous bubbling when the colony is emulsified with 30% H2O2. […]

Acetamide Utilization Test: Principle, Procedure, Expected results, Quality Control and Limitation

Acetamide Utilization test: This test is useful in differentiation of nonfermentative gram-negative bacteria, particularly Pseudomonas aeruginosa. Principle of Acetamide Utilization Test Acetamide utilization test is used to check the ability of an organism to use acetamide as a sole source of carbon. Organisms that can grow on this medium are able to deaminate acetamide and release […]

X and V factor test: Identification test for Haemophilus

Members of the genus Haemophilus are fastidious in nature. i.e. they require extra nutritional supplements in order to grow.  Some Hemophilus require only X factor (haemin-which is present on blood agar)  or only V factor (Nicotinamide-adenine dinucleotide, NAD- which is present within the blood cells) or a combination of both. So,  Haemophilus influenzae grows only […]

Definition of Staphylococci

Members of the genus Staphylococcus are gram positive cocci of size 0.5-1.5 um in diameter. They occur in singles, pairs, tetrads, short chains and irregular grape like cluster. They are nonmotile and nonspore- forming. Most species are catalase positive and are facultative anaerobes, grows better under aerobic than anaerobic conditions. The anaerobic species Staphylococcus saccharolyticus […]