Phage typing

Phage Typing

Plaques formed by bacteriophages on a bacterial lawn.

Phage typing is a method used to detect and identify bacterial species and strains based on their susceptibility to specific bacteriophages. This technique exploits the specificity of bacteriophages, which are viruses that infect bacteria, to differentiate between bacterial strains.

History

Phage typing was first developed in the early 20th century and became a valuable tool in epidemiology and microbiology. It was initially used to type strains of Salmonella and Staphylococcus aureus, providing insights into the spread of infectious diseases.

Methodology

The process of phage typing involves the following steps:

1. Isolation of Bacteria: The bacterial strain to be typed is isolated and cultured on an agar plate. 2. Application of Phages: A set of bacteriophages with known specificity is applied to the bacterial lawn. 3. Observation of Plaques: The plate is incubated, allowing phages to infect susceptible bacteria. This results in clear zones called plaques, where bacteria have been lysed. 4. Interpretation: The pattern of plaques is compared to a reference chart to determine the phage type of the bacterial strain.

Applications

Phage typing is used in various fields, including:

• Epidemiology: Tracking the source and spread of bacterial infections.
• Public Health: Identifying outbreaks of foodborne illnesses.
• Research: Studying bacterial genetics and evolution.

Advantages and Limitations

Phage typing offers several advantages, such as high specificity and the ability to differentiate closely related bacterial strains. However, it also has limitations, including the requirement for a comprehensive phage library and the potential for variability in results due to environmental factors.

Future Directions

With advances in genomics and molecular biology, phage typing is being complemented by molecular techniques such as whole genome sequencing. These methods provide more detailed information about bacterial strains and their genetic makeup.

Related Pages

• Bacteriophage
• Microbial genetics
• Antibiotic resistance
• Infectious disease