Methods for bacterial typing
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This document discusses various methods for typing bacterial strains, including phage typing, bacteriocin typing, resistotyping, biotyping, serotyping, plasmid typing, and molecular typing. Phage typing uses bacteriophages to identify bacterial strains and has been used for Staphylococcus aureus. Bacteriocin typing analyzes antibiotic-like substances produced by bacteria. Resistotyping examines sensitivity to antimicrobial agents. Biotyping, serotyping, and plasmid typing rely on biochemical reactions and presence of surface antigens or plasmids. Molecular typing uses techniques like PCR for high sensitivity and specificity but requires specialized equipment.
Methods for bacterial typing
- 1. 4/18/2013 1 Means identification of the organisms to strain level. The main purpose to control nosocomial infection and also can used in different epidemiological purpose (cholera, meningitis …etc).
- 2. 4/18/2013 2 Similarity between isolates Wide range of characters that could be examined Significance of differences needs to be understood Significance of differences needs to be clearly expressed Relationship to other strains Comparator strains must Be recognisable by the typing methods Have known characteristics Phage typing. Bactericin typing. Resistotyping. Biotyping. Serotyping. Plasmid typing
- 3. 4/18/2013 3 Phage is virus which live in a living cell. Bacteriophage: is a virus live in a bacterial cell, and used for typing of bacterial, it is specific and live in certain strain. There are two type of bacteriophage: Lytic bacteriophage: cause lysis of bacterial cell and used for typing. Lysogenic bacteriophage: Does not cause lysis of bacterial cell but play important role in the gene transferring. There is a bacteriophage for any bacteria but usually used for typing of S. aurus in control of nosocomial infections. Phage typing also used for different epidemiological purpose as in Mycobacterium, Brucella, Salmonella…etc.
- 4. 4/18/2013 4 Phage typing of S. aureus: There are 4 main group I, II, III and IV. And each group consist of different number of single phage. Method: Reconstitute the phage (activation the virus). Inoculate the NA plate with the tested organism after labelling. Add the phage as drop, incubate and read result Advantage: Very specific method. Disadvantage: Difficult to perform – need well equipped laboratory (preservation of virus) – time consuming – not used for all type of organisms.
- 5. 4/18/2013 5 Bactericin is antibiotic-like substance produced by certain organism that can inhibit the growth of some close related bacteria. Eg: Colicin typing used for typing of Shigella sonni Depend on biochemical reaction. Modified from identification to typing. Most used Analytical profile index (API). Eg: API 20 E
- 6. 4/18/2013 6 Advantage: Easy to perform – Standardized. Disadvantage: Cannot used for all organisms.
- 7. 4/18/2013 7 Depend on serological reactions. Used for identification and can be used for typing. Advantage: standardized – specific – easy to perform. Disadvantage: Cannot used for all microorganisms. Also called antibiogram. It is sensitivity test for typing. Used different type of antimicrobial agents differ from that used for treatment (toxic may be dyes). Advantage: easy to perform-simple- cheap. Disadvantage: limited sensitivity (for organism highly sensitive or resistant).
- 8. 4/18/2013 8 Also called molecular typing, eg; PCR. Advantage: very sensitive-very specific. Disadvantage: need special machine- very expensive method.