1. Describe the various methods for identification of bacteria. 2. Define and classify sterilization. Explain about Hot air oven. 3. Write morphology, culture characteristics, pathogenicity and laboratory diagnosis of Salmonella typhi.
Answer (1)
Methods for Identification of Bacteria:
a. Microscopic Examination : This involves using a microscope to observe the shape, size, and arrangement of bacteria. Staining techniques like Gram staining help differentiate bacteria into gram-positive and gram-negative groups.
b. Culture Techniques : Bacteria are grown in specific media that support their growth. Different bacteria require different types of nutrients.
c. Biochemical Tests : These tests determine the metabolic and enzymatic activities of bacteria. Common tests include oxidase, catalase, and urease tests.
d. Molecular Methods : Techniques like PCR (Polymerase Chain Reaction) and DNA sequencing are used to identify bacteria based on genetic material.
e. Immunological Methods : Antibody-based methods are used to identify bacteria by detecting specific proteins on their surface.
Sterilization:
Sterilization is the process of eliminating all forms of life, including microbial spores, from an object or environment.
Classification of Sterilization:
a. Physical Methods : Involve removing or destroying microorganisms via heat or filtration. Techniques include autoclaving, hot air oven, and filtration.
b. Chemical Methods : Use of chemical agents like ethylene oxide, formaldehyde, and alcohols to sterilize equipment and surfaces.
Hot Air Oven:
A hot air oven uses dry heat to sterilize materials that can withstand high temperatures, typically set at around 160-170°C for 2-4 hours. It is commonly used for sterilizing laboratory glassware and metal instruments, as it does not corrode or dull these items.
Salmonella Typhi:
Morphology : Salmonella typhi are rod-shaped, gram-negative bacteria with flagella that provide motility.
Culture Characteristics : They grow on simple agar media, producing characteristic colonies. They can be cultured on selective media like XLD agar, which aids in identifying them from mixed flora.
Pathogenicity : Salmonella typhi is the causative agent of typhoid fever, a systemic infection marked by high fever, abdominal pain, and rash. The bacterium invades the intestinal lining and spreads through the bloodstream.
Laboratory Diagnosis : Diagnosis typically involves isolating the bacteria from blood, stool, or bone marrow samples. Serological tests like the Widal test can be used to detect antibodies against Salmonella antigens.
