BACTERIAL TYPING To identify the source of To distinguish infectious from non-infectious organisms (i.e. a pathogenic or a To distinguish relapse from reinfection cases.

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

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

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

Applications of They are used to type Treatment and diagnosis of Treatment of Food preservation. 4. Pyocine Pyocine is produces by some strains of Pseudomonas; and used to type other Pseudomonas.

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

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

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

Precipitation A precipitation ring occurs between the serum (antibody) and the fluid Lancefield Plate precipitation In To diagnose infections of Strep., Neisseria, B. anthracis, Haemophilus, pneumococci, etc.

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

First activate complement in serum by adding Ca ++ & Mg ++ salts. Positive 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

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

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.

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.

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

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

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

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

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