1. BACTERIAL TYPING Applications: @ To identify the source of infection. @ To distinguish infectious from non-infectious organisms (i.e. a pathogenic or a commensal). @ To distinguish relapse from reinfection cases.

3. Bacterial typing methods: # Phenotypic methods # Genotypic methods: Phenotypic methods 1.Antimicrobial susceptibility typing according to the susceptibility pattern 2.Biotyping: according to biochemical reactions.

5. 3. Bacteriocine Typing: @ Bacteriocine is a protein produced by certain bacterial species. @ It is a toxin that inhibits the growth of bacterial strains of the same family but not of the same species secreting it. @ This toxin is regarded as an antibiotic.

7. @ Common bacteriocines are: # Colicine: secreted by Gram-negative bacteria: e.g. E.coli & coliforms. # Megacine: secreted by Gram-positive bacteria e.g. B.megaterium. @ Production is controlled genetically by a plasmid factor.

9. Applications of bacteriocines: @ They are used to type bacteria. @ Treatment and diagnosis of cancer @ Treatment of listeriosis. @ Food preservation. 4. Pyocine Typing: @ Pyocine is produces by some strains of Pseudomonas; and used to type other Pseudomonas.

11. Pyocine typing is done as follows: @ Streak test strain across a tryptone soya blood agar medium @ Incubate at 37 °C overnight. Collect all the crop by a sterile slide. @ Expose the remaining growth on the plate to chloroform for 15 minutes @ Streak Ps. pyocyanea indicator strains at right angles to test strain streak. @ Re-incubate the plate at 37 °C overnight. @ Read test by looking for zones of inhibitions.

13. 5. Serological Typing: @ Here patient serum is used to study the antigen-antibody reaction @ Antigens used are known, and disease is diagnosed by identifying the antibody in serum @ Different types of serological tests: # Precipitation # Agglutination # Precipitation # ELISA # C.F.T. # ELISA # C.F.T. # Immunoflurescence # Immunoflurescence

15. Agglutination test: @ Agglutination occurs when the antigen unites with the antibody and clumps together. @ It will diagnose brucellosis, enteric fever, etc @ Agglutination needs : Presence of salts, e.g. Na Cl Neutral pH Temperature between 37 °– 50 °C Serum is heated (50°C) to destroy complement

17. Precipitation test: @ A precipitation ring occurs between the serum (antibody) and the fluid antigen.Applications: @ Lancefield typing @ Plate precipitation test. @ In immuno-electrophoresis @ To diagnose infections of Strep., Neisseria, B. anthracis, Haemophilus, pneumococci, etc.

19. Immunoflurescence : @ Antigen unites with a fluorescent dye, exposed to U.V. rays & examined under fluorescence microscope to see a fluorescent antigen.ELISA: @ Very popular, highly sensitive, more safe, more cheap, and constant in its results.

21. C.F.T.: @ First activate complement in serum by adding Ca ++ & Mg ++ salts. Positive CFT: @ Positive CFT: # Ag + specific Ab + C = complement fixation # Fixed complement + RBC = no RBC haemolysis Negative CFT: # Ag + non specific Ab + C = no C fixation # Non fixed complement + RBC = RBC haemolysis

23. 6. Phage Typing: @ Phage typing is used to trace sources of infections caused by: S.aureus, P.aeruginosa, Salmonella species, B.abortus, M.tuberculosis Staph. aureus phage typing: @ 24 phages known to destroy S. aureus. @ S. aureus is divided into > 100 phage types.

25. Procedure of phage typing: 1-Inoculate S. aureus on a nutrient agar plate divided into 24 squares from outside 2-Use standard concentration of phages that gives confluent areas of S. aureus killing.

27. 3-Drop each phage in a separate square and incubate at 37 °C overnight 4-Look for areas of no growth on each square, i.e. complete destruction of S. aureus cells. 5-Record the phage number that made the destruction. 6-This phage number is the S. aureus type.

29. BACTERIAL GENOTYPING Applications: @ To determine if bacterial isolates are genetically related. @ To trace the source of infection outbreaks @ To determine multidrug-resistant pathogens. @ GENOTYPIC METHODS INCLUDE: 1.Pulsed-field gel electrophoresis typing 2.PCR typing 3.Multilocus sequence typing 4.Plasmid analysis.

31. 1. Pulsed-field gel electrophoresis typing: @ It is similar to standard gel electrophoresis except that instead of running the current in one direction, it is run in 3 directions. @ It is applied for genotyping and tracing sources of infections.

33. 2. PCR typing: Application: # Identification of slow-growing organisms, # Early diagnosis of infectious diseases # Diagnosis of hereditary diseases # Identification of fingerprints and paternity

35. 3. Multilocus sequence typing: @ It is used to differentiate and type many isolates, e.g. Campylobacter, N. meningiditis, S. aureus, S. pyogenes, C. albicans

37. 4. Plasmid typing: @ A plasmid is a small DNA molecule that is separate from cell chromosomal DNA @ Plasmids carry genes of antibiotic resistance and can be transmitted from one bacterium to another. @ Plasmids are extracted by PCR and used to differentiate and type bacteria.